Spatial cooling system

Abstract

A system 100 provides cooling to a contained environment 120 and comprises a controller 180, an energy storage unit 150 comprising a coolth storage medium 168 in an insulating housing 152 and an elect

Description

FIELD OF THE INVENTION The present invention pertains generally to the field of cooling and, in particular the cooling of enclosed spaces. More particularly, the present invention relates to a method and system for the controlled environmental cooling of an enclosed space. BACKGROUND OF THE INVENTION Thermal control of spaces for a particular purpose is a constant challenge for any space, whether for heating or cooling. Cooling of enclosed spaces presents a challenge, for example in homes in warm countries, for storage facilities that require a constant temperature for the preservation of their contents, for workplaces and factories who may have regulatory compliance issues and for refrigeration, both in-home and in-store. A particular challenge with cooling, such as in refrigeration, is the cost, both financial and environmental. With increasing need to address and mitigate the effects of climate change, increasingly stringent requirements on energy use and CO2 emissions are likely to be implemented. There is therefore an incentive to find lower CO2 emissions solutions to the problem of refrigeration and to cooling more generally. By way of example, there are millions of fridges and fridge-freezer units in millions of homes, shops, retail outlets, restaurants, supermarkets and convenience stores across the globe today. These appliances collectively consume many Terawatt-hours (TWh) of electricity and are responsible for the emission of several Gigaton of CO2 into the atmosphere each year. Unfortunately, in many countries where large number of these fridges and / or fridge-freezers are in use, most of the electricity which they consume is generated using fossil fuels. This is true also for many factories, laboratories and homes that require thermal control too. In order to reduce fossil fuel consumption, there is a global drive to use renewable power sources to generate electricity, which is then used to power refrigeration and other apparatus. However, most renewable power sources, such as wind energy and solar energy, are intermittent at generation which makes it difficult to use the renewable power as a reliable solution for powering refrigeration units, which are required to maintain a lowered temperature to avoid the spoilage of food etc. It is known to provide grid-level energy storage to smooth fluctuations in renewable power but there is also the opportunity for demand-side management of electricity and energy use that can also contribute. There is also an urgent global need to reduce humanity’s materials consumption. Typical refrigeration apparatus requires substantial amount of raw material, and energy consumption during manufacture, to form housings, compressors, electronics etc. It would be advantageous to reduce this requirement for material and energy. There is a need for a solution to spatial cooling and maintenance of the temperature of contained spatial environments below a temperature of an outside temperature in a manner that reduces reliance on fossil fuel-derived electricity and improves the efficiency of energy use. The present inventors have found a solution to the above. PROBLEM TO BE SOLVED BY THE INVENTION It is an object of the invention to provide an improved system for cooling an enclosed or contained space which provides effective cooling at a lower cost and / or with lower CO2 emissions. SUMMARY OF THE INVENTION In accordance with a first aspect of the invention, there is provided a system for providing cooling to a contained environment, the system comprising: a controller; at least one energy storage unit, an energy storage unit comprising: an insulating housing; a coolth storage medium within the housing; and an electrically-powered cooler, which is configured to provide electrically-powered cooling to cool the coolth storage medium, wherein the electrically-powered cooling is variable under the control of the controller; at least one demand-initiating device for generating a demand factor associated with the demand for coolth in the contained environment; and a coolth delivery sub-system configured to deliver coolth from the energy storage unit to the contained environment in response to at least one demand factor from the at least one demand-initiating device, wherein the controller is configured to operate the electrically-powered cooler to increase the quantity of energy stored as coolth, according to i) predicted frequency, magnitude and / or duration of generated demand factors; and / or ii) predicted availability of renewable energy-derived electricity and / or electricity having a cost below a defined threshold. In a second aspect of the invention, there is a coolth delivery system for delivering coolth from an energy storage unit storing coolth to a contained environment, for use as a coolth delivery sub-system in the above system. In a third aspect of the invention, there is a coolth delivery system for delivering coolth from an energy storage unit storing coolth to a contained environment, the coolth delivery systems comprising a coolth delivery conduit for the transfer of a coolth delivery fluid from a coolth storage medium in an energy storage unit to a coolth delivery interface disposed in or in relation to the contained environment. In a fourth aspect of the invention, there is a spatial cooling system comprising a system for providing cooling to a contained environment as defined above and a contained environment provided with the said system. In a fifth aspect of the invention, there is provided a coolth delivery interface for delivering coolth from a coolth delivery system. In a sixth aspect of the invention, there is provided a refrigerator door adapted for use as a coolth delivery interface for providing coolth to a refrigerator. In a seventh aspect of the invention, there is a method of cooling a contained environment to a desired temperature or maintaining the temperature of a contained environment at a temperature below that of the surrounding environment, the method comprising operating the system of providing cooling to a contained environment as defined above. In an eighth aspect of the invention, there is a coolth circulation system for providing coolth to multiple contained environments from a common energy storage unit, the system comprising: at least one energy storage unit comprising at least one insulated housing, a coolth storage medium in the at least one insulated housing and electrically-powered cooler for cooling the coolth storage medium within the insulated housing; a coolth delivery circuit for delivering a coolth delivery fluid selectively to any one or more of a plurality of discrete contained environments via a coolth delivery interface associated with each of the plurality of discrete contained environments; a coolth return circuit for returning the coolth delivery fluid from the one or more of a plurality of discrete contained environments; a controller for controlling the selective delivery of coolth delivery fluid via the coolth delivery circuit to the any one or more of a plurality of discrete contained environments according to one or more pre-defined criteria; and, preferably, a controller for controlling the operation of the electrically-powered cooler according to: i) predicted cumulative frequency, magnitude and / or duration of generated demand factors from the plurality of contained environments; and / or ii) predicted availability of renewable energy-derived electricity and / or electricity having a cost below a defined threshold. In a ninth aspect of the invention, there is provided an apparatus comprising: an apparatus controller; at least one energy storage unit, an energy storage unit comprising: a housing comprising an insulating layer; a coolth storage medium within the housing; an electrically powered cooler, configured to provide electrically powered cooling to cool the coolth storage medium, wherein the electrically powered cooling is variable under the control of the apparatus controller; at least one outlet port; and one or more refrigeration units in fluid communication with the at least one energy storage unit via at least one fluid (e.g. air) conduit, each refrigeration unit comprising: a housing comprising an insulating layer; one or more storage chambers within the housing; and at least one inlet port; and at least one fluid (e.g. air) moving device configured to transport cool fluid (e.g. air) from the at least one energy storage unit to the one or more refrigeration units via the at least one fluid (e.g. air) conduit. ADVANTAGES OF THE INVENTION The system of the invention provides an improved method for the cooling of a contained environment, such as a refrigerator, in which the cost of the energy used is minimized and / or the renewable energy content of the energy used is maximized. BRIEF DESCRIPTION OF THE DRAWINGS Figure lisa schematic diagram of a system in accordance with an embodiment of the present invention; Figure 2 is a schematic diagram of an apparatus in accordance with a further embodiment of the present invention; Figure 3 is a schematic diagram of an alternative energy storage unit in accordance with the present invention; Figure 4 is a schematic representation of one embodiment of a system for providing cooling to a contained environment according to one aspect of the present invention; Figures 5A and 5B illustrate a coolth interface for use in a system of the invention according to one embodiment and in another aspect of the invention; Figure 6 illustrates a coolth interface of Figures 5 A and 5B in a refrigerator in one embodiment of the invention; Figure 7 illustrates a refrigerator and refrigerator door according to an embodiment of the invention; Figure 8 illustrates a refrigerator and refrigerator door according to another embodiment of the invention; and Figure 9 is a diagrammatic representation of a coolth circulation system according to another aspect of the invention. DETAILED DESCRIPTION OF THE INVENTION The invention is directed to a system for providing cooling to a contained environment. The system comprises a controller, at least one energy storage unit, at least one demand-initiating device and a coolth delivery subsystem. The energy storage unit comprises an insulating housing and, within the housing, a coolth storage medium, and an electrically powered cooler configured to provide electrically-powered cooling to cool the coolth storage medium, which electrically powered cooler is under the control of the controller. The controller is configured to operate the electrically-powered cooler to increase the quantity of energy stored as coolth, according to: i) predicted frequency, magnitude and / or duration of generated demand factors; and / or ii) predicted availability of renewable energy-derived electricity and / or electricity having a cost below a defined threshold. Thus, the coolth stored in the coolth storage medium and in the energy storage unit may be varied in dependence of demand-side factors and / or supply-side factors, preferably with a view to maximizing the utilization of low-carbon energy in providing cooling for the contained environment. The electrically-powered cooler is thus preferably configured to operate only when it is advantageous to do so according to demandside and supply-side factors. The provision of energy storage as coolth within the apparatus enables renewable power use to be maximised and / or electricity cost to be minimised, while tolerating gaps in renewable energy availability, such as the relatively long gaps which may occur with wind power or overnight in the case of solar power. The storage of coolth within a coolth storage medium can be more energy efficient than storing power in a battery and avoids the consumption of rare earth metals and other components required to build large batteries. The term coolth will be understood to mean the opposite or absence of warmth, for example, the potential for thermal energy to be absorbed. Providing coolth to a system is therefore understood to be the introduction of a means by which the thermal energy of a system may be absorbed and removed therefrom. The term coolth is a relative term, but it will be understood that in this context we are referring to the potential for thermal energy to be removed from ambient temperature air, or air above the optimal operating temperature or selected temperature range of the contained environment. It will therefore be understood that storing coolth in a material refers to storing thermal energy absorption potential within the material by reducing the thermal energy of the material through cooling. The coolth is understood to be stored because the material now has the potential to absorb thermal energy from its surroundings, i.e., the material can cool the surroundings. It will be understood that references to the amount of coolth stored by or in a material relates to how much thermal energy the material can absorb before it is in thermal equilibrium with its surroundings. Thus, the coolth storage capacity of a material may be increased by further cooling the material, thus increasing its capacity for thermal energy absorption. More coolth may be stored in a material if the material undergoes a phase change during cooling, as further thermal energy may be absorbed without changing the temperature of the material. For the avoidance of doubt, it will be understood that the movement of coolth will refer to the movement of this thermal energy absorption potential or a material which contains or to which is imparted the thermal energy absorption potential, e.g. a coolant fluid. The coolth storage medium may be any suitable storage medium. It may be that the coolth storage medium is a solid coolth storage medium (e.g., sand) or it may be a liquid coolth storage medium. Optionally, the coolth storage medium is a phase change material, such as water. Preferably, the coolth storage medium is water, or an aqueous medium, which acts as a phase change material. It may be that at least one energy storage unit comprises a plurality of coolth storage modules, each module comprising a respective volume of coolth storage medium. In one embodiment, the at least one energy storage unit is configured to selectively cool the coolth storage medium within different storage modules of the plurality of coolth storage modules at different times, or different rates. For example, the at least one energy storage unit may be configured to selectively cool the coolth storage medium within different storage modules of the plurality of coolth storage modules consecutively. Thus, the step of cooling the coolth storage medium may comprise cooling coolth storage medium within different storage modules at different times, for example in turn or consecutively. Alternatively, or additionally, the at least one energy storage unit may be configured to cool the coolth storage medium within different storage modules of the plurality of coolth storage modules concurrently, in parallel. In one embodiment, where the energy storage unit comprises a plurality of coolth storage modules, the system may be configured so that the coolth delivery sub-system is configured to deliver coolth from one or more discrete coolth storage modules to one or more discrete contained environments. For example, the system may be configured such that each coolth storage module is the source of coolth for separate contained environments or that two or more coolth storage modules of the plurality of coolth storage modules may together be the source of coolth for an individual contained environment. In another embodiment, system may be configured such that the coolth delivery sub-system is configured to deliver coolth from the plurality of coolth storage modules within the energy storage unit, as a single source of coolth, to one or a plurality of contained environments in sequence or in parallel. The coolth delivery system is operable in response to demand factors or to signals representative of demand factors sent to a delivery controller, which may be the same or different to the controller for the electrically-powered cooler, but is preferably in communication therewith. The delivery controller, in turn, signals the coolth delivery system to operate in delivery of coolth to the contained environment. Demand factors may be a signal or condition and may be represented by a signal, e.g. a demand-dependent signal or a demand signal, which a coolth delivery system may be configured to be responsive to. Demand factors may be generated by a demand-initiating device. The demand-initiating device may be any device capable of generating a demand factor or demand signal which a coolth delivery system and, more particularly, a controller therein, may be responsive to, for the purpose of delivering coolth to the or a contained environment. In one embodiment, a demand-initiating device may be a switch or button that is configured to generate a demand factor in the form of a signal upon actuation by a user (e.g. a user of the contained environment). The demand factor may, in such a case, be simply an on / off signal or a signal indicating a demand for a pre-determined time period. Such a manual demand-initiating device may be used alone or in combination with other demand-initiated devices. In another embodiment, the demand-initiating device may be a sensor, the sensor being capable of detecting one or a combination of demand features, which are features or conditions that are in some way representative of a demand, and generating a demand factor as a result of the demand feature detection, which demand factor may typically be in the form of a sensor signal. When the demand factor received by the controller or generated by the demand-initiating device meets a pre-defined threshold (or dynamic threshold, depending upon predicted future use) for the delivery of coolth, the controller may actuate or cause the operation of the coolth delivery system to deliver coolth to the contained environment. The demand signal is typically produced by one or more sensors configured to sense certain pre-defined demand features and to communicate that signal to the delivery controller. Demand factors may be any factor that affects the need for cooling of a contained space. For example, demand factors or demand features may include any one or more of: occupancy level (e.g. number of articles that need to be cooled or number of people or animals in the contained environment at one time); nature of occupancy (e.g. thermal energy being released by the occupant articles of beings in the contained environment - for example, a warm food article placed in a refrigerator space, or a warm biological sample placed in the room, or a person exercising in the contained environment); opening of the contained environment such as opening of a door (including number of openings, extent of openings and duration of openings); thermal factors such as temperature within the contained environment reaching or exceeding a pre-defined threshold; and manual activation (e.g. the pressing of a button by a user). Sensors for detecting demand features and generating demand factors may include one or more or a combination of, for example: counters for determining occupancy level or thermal imaging camera sensors or infrared sensors for detecting occupancy by warm-bodied articles or people; thermal or infrared sensors for detecting degree of thermal emission by occupying articles or people in the contained environment; door sensors for detecting when and for how long a door of a contained environment is opened; and temperature sensors for detecting the temperature in the contained environment and determining the differential temperature in the contained environment relative to an external temperature (i.e. immediately outside the contained environment). The actual temperature as determined by thermal sensors within the contained environment may be considered as a contemporaneous indicator of temperature in the contained environment while other demand factors such as occupancy level, door-opening and occupancy nature may be lead indicators of temperature in the contained environment and of the need for coolth. Such lead indicators may be used, via demand signals, to cause the operation of the coolth delivery sub-system to deliver coolth to the contained environment according to pre-determined thresholds associated with one or more of the demand signals. Temperature data (e.g. from thermal sensors within the contained environment) may be considered as direct demand data as may manual activation signal data (e.g. pressing of a button, or selection of a switch on a mobile app), while other demand factors as discussed above (e.g. occupancy data, occupancy nature and opening data) may be considered as indirect demand data. Thus, in one embodiment of the invention and in a further aspect of the invention, there is a correlation engine comprising a processor running a machine learning algorithm to establish relationships between indirect demand data and temperature within the contained environment in order to produce demand signal profiles and / or coolth-initiating thresholds associated with indirect demand data for a particular contained environment. In a further embodiment and aspect, there is a method for establishing demand signal profiles and / or coolth-initiating thresholds associated with indirect demand data for a particular contained environment, the method comprising supplying an appropriately configured correlation engine with indirect demand data and demand data over time or the method comprises measuring indirect and direct demand data associated with the contained environment, establishing correlations between indirect demand data and temperature data over time associated with the contained environment and determining therefrom profile features and / or thresholds of indirect demand data that are correlated with or predictive of a temperature threshold associated with the contained environment being reached. The delivery controller may be configured to utilise such established demand signal profiles and / or coolth-initiating thresholds associated with indirect demand data for a particular contained environment to signal the coolth delivery system to operate in delivery of coolth to the contained environment, optionally in combination with direct demand data. The configuration of the controller to operate the electrically-powered cooler to increase the quantity of energy stored as coolth may include a machine learning and / or artificial intelligence module. This machine learning and / or artificial intelligence module may be used to assist the controller in operating the electrically-powered cooler according to predicted frequency, magnitude and / or duration of generated demand factors. Such a machine learning and / or artificial intelligence model may be configured to predict demand factor patterns based upon measured demand factors and other correlated behaviour factors using machine learning algorithms and AI. Other correlated behaviour factors may include weather data (e.g. the increased desire for cool drinks on a warm day, thus correlating warm weather with increased demand), work pattern data (or school holiday information) thus correlating working from home or working for work with the timing of demand as well as personal data such as personal calendars (for predicted presence and usage of the contained environment) and digital communication and social media activity (e.g. event-hosting plans), and advertising data (e.g. promoting a certain behaviour). For example, social media activity (e.g. by the operator or owner of the contained space or by people in the same geographic area) may be mined for demand prediction indicators - it could be that the mention of key words such as bbq, party, beer or more pertinently contextual interpretation of social media activity can be used by such AI / ML module to predict demand factors for coolth in the contained space. Similarly, weather forecasts may be used to provide predicted demand factors over a period of time, to predict demand for coolth in the contained environment - an extended period of warm weather, for example, may be predictive of increased demand for coolth. Thus, in one embodiment of the invention and in a further aspect of the invention, there is a machine learning module for predicting demand factors, the machine learning module comprising a processor having one or more machine learning algorithm configured to determine correlations of measured demand factor data and other correlated behavioural factors to establish behavioural patterns and correlating-inter-relationships whereby demand factor frequency, duration and extent can be predicted for a particular contained environment (e.g. from preliminary measured demand factor patterns and / or other correlated behavioural factors). In one embodiment of the invention, the controller is configured to operate the electrically-powered cooler to increase the quantity of energy stored as coolth in dependence on the predicted demand factors for the contained environment over a projected period of time. Furthermore, the controller may be configured to change a threshold (e.g. of electricity price or availability of renewables) for operating the electrically-powered cooler, in response to a predicted change in demand of a projected period of time. As mentioned above, in additional to or as an alternative to predicted frequency, magnitude and / or duration of generated demand factors as a condition of operating the electrically-powered cooler to increase the quantity of energy stored as coolth, the controller may be configured to operate the electrically-powered cooler to increase the quantity of energy stored as coolth according to predicted availability of renewable energy-derived electricity and / or electricity having a cost below a defined threshold. The predicted availability of renewable energy-derived electricity and / or electricity having a cost below a defined threshold may be supplied by existing commercially-available algorithms or by electricity provides with demand-flexibility tariffs, such as Octopus Energy in the UK. Availability of renewable electricity or energy may refer to electricity or energy of which a variable fraction is generated by renewable power generators, such that a greater availability of renewable electricity or energy indicates that a greater proportion of the electricity or energy available to be consumed is generated through renewable means. Thus, the apparatus may harvest available renewable electricity when it is available, thereby maximising the use of renewable electricity and minimising the reliance on electricity from non-renewable sources. Additionally, the contained environment may thereby be maintained at its target temperature or temperature range through renewable means even if renewable energy is not available at a time when cooling is required. In one embodiment, the controller is configured to implement (and the method comprises implementing) a temporary energy storage procedure in response to a decreased cost of electricity. Thus, the apparatus may store electricity when it is at a lower cost in order to provide any necessary cooling (e.g. predicted from demand patterns or pre-programmed) during periods of higher cost (relative to the lower cost) electricity to save the user money on electricity. In one embodiment, the controller is configured to implement (and the method may comprise implementing) the temporary energy storage procedure in dependence on predicted future availability of renewable electricity. It may be that the apparatus controller is configured to implement (and the method may comprise implementing) the temporary energy storage procedure in advance of a predicted increase in availability of renewable electricity. It may be that the apparatus controller is configured to implement (and the method may comprise implementing) the temporary energy storage procedure in advance of a predicted decrease in availability of renewable electricity. Thus, if it is predicted that there will soon be a period of time for which a limited amount of renewable electricity will be available, the apparatus can store coolth in advance of this period of time to maximise the remaining renewable electricity availability and minimise the reliance on electricity from primarily non-renewable sources. It may be that the apparatus controller is configured to implement (and the method may comprise implementing) the temporary energy storage procedure in dependence on predicted future cost of electricity. It may be that the apparatus controller is configured to implement (and the method may comprise implementing) the temporary energy storage procedure in advance of a predicted decrease in cost of electricity. It may be that the apparatus controller is configured to implement (and the method may comprise implementing) the temporary energy storage procedure in advance of a predicted increase in cost of electricity. Thus, if the price of electricity is predicted to increase at a point in the future, the temporary energy storage procedure may be implemented to store the maximum amount of coolth possible while the price of electricity is still low relative to the future predicted price. This therefore allows the apparatus to continue refrigeration during the period of high electricity price without needing to consume the high-price electricity. It may be that the apparatus is configured to stop an energy storage procedure (and the method may comprise stopping an energy storage procedure) in response to a maximum storage condition being met by the at least one energy storage unit. Thus, the apparatus does not use excess electricity when it cannot be harvested, thus minimising wasteful electricity usage. It may be that the maximum storage condition is a temperature threshold condition. The energy storage procedure may be said cooling of the coolth storage medium by the electrically-powered cooler. It may be that the maximum storage condition is variable. Thus, the apparatus can be configured to have a variable capacity for storage. It may be that a greater amount of coolth is stored in response to an increased availability of renewable electricity. Thus, the apparatus may use a greater proportion of the available renewable electricity at the time that it is available, thereby maximising the use of renewable electricity and minimising the reliance on electricity from nonrenewable sources as more coolth will be stored for later use. It may be that a greater amount of coolth is stored in response to a decreased cost of electricity. Thus, the apparatus may store a greater amount of coolth using electricity at a lower cost such that refrigeration may be provided for a longer period of time, e.g., during periods of higher cost (relative to the lower cost) electricity, thereby saving the user money on electricity. It may be that a greater amount of coolth is stored in response to a predicted decrease (or increase) in the availability of renewable electricity than would otherwise be the case. Thus, if it is predicted that there will soon be a period of time for which a limited amount of renewable electricity will be available, the apparatus may increase the amount of coolth which is able to be stored such that amount of coolth stored using the remaining renewable electricity availability is maximised and the reliance on electricity from primarily nonrenewable sources is minimised during the period of time for which a limited amount of renewable electricity is available. It may be that a greater amount of coolth is stored in response to a predicted increase (or decrease) in cost of electricity than would otherwise be the case. Thus, if the price of electricity is predicted to increase at a point in the future, the apparatus may increase the amount of coolth which is able to be stored such that the amount of coolth stored is maximised while the price of electricity is still low relative to the future predicted price. This therefore allows the apparatus to continue refrigeration during the period of high electricity price without needing to consume the high-price electricity. The electrically-powered cooler is configured to provide electrically-powered cooling to cool the storage medium or cause the change of phase of the storage medium - in other words, the electrically powered cooler is configured to extract energy from the storage medium (whether for the purpose of cooling or changing the phase thereof). The electrically-powered cooler operates under the control of the controller. Any suitable electrically-powered cooler may be used. For example, the electrically-powered cooler may be a compressor-type cooler having a compression-expansion circuit, as used in a refrigerator or fridge freezer, whereby a circulating coolant is circulated through a circuit (e.g. expansion conduit) in thermal communication with the energy storage unit and, more particularly, the coolth storage medium (through one or more thermally conductive pipes or conduits). In another example, the electrically-powered cooler is a thermoelectric cooler. According to this example, the thermoelectric cooler may serve to cool a coolant fluid which is circulated through a pipe or conduit in thermal communication with the energy storage unit and, more particularly, the coolth storage medium, or the thermoelectric cooler may be in direct contact with the energy storage unit or coolth storage medium to impart coolth (i.e. extract energy) from the coolth storage medium. The electrically-powered cooling of the coolth storage medium may be variable because the electrically-powered cooler can be switched on or off by the apparatus controller. The electrically-powered cooling may be variable because the rate of cooling (e.g., power consumption of the electrically-powered cooler) may be variable within a range. Optionally, the electrically-powered cooler, which produces waste heat (e.g. thermal energy extracted from the coolth storage medium) is configured to cooperate with a heat demand and / or a heat store. In the event that there is a neighbouring contained environment for which a higher than ambient temperature is required, the waste heat may be provided to the neighbouring contained environment. Optionally, the electrically-powered cooler cooperates with a heat store for the use or storage of its waste heat, e.g. phase change material heat store or water tank or seasonal storage vessel (e.g. underground thermal storage). The contained environment may be any environment that is an insulated space that has a requirement for occasional, periodic or continuous maintenance of a temperature below the surrounding ambient temperature. The contained environment may be a home or house, a cooled storage room (e.g. for articles or artifacts requiring a constant temperature), a laboratory (with a need for constant temperature), a walk-in refrigerated room, or a (food) storage chamber of a refrigerator. In a particular set of embodiments, the contained environment is the storage chamber of a refrigerator, which may be a domestic or a commercial refrigerator or refrigeration system. The coolth delivery sub-system may be any suitable coolth delivery system for delivering coolth from the energy storage unit to the contained environment. Typically, the coolth delivery system will utilise a coolth delivery fluid that flows or is pumped through a delivery conduit from the energy storage unit to the contained environment. The coolth delivery system may comprise a delivery interface, being where the coolth is transferred from the coolth delivery fluid to the contained environment (i.e. where heat is absorbed by the coolth delivery fluid from the contained environment). The coolth delivery system may comprise a storage interface where coolth is transferred from the coolth storage medium to the coolth delivery fluid (e.g. heat is absorbed by the coolth storage medium from the coolth delivery fluid). The coolth delivery system may be a direct coolth delivery or an indirect coolth delivery arrangement. By direct coolth delivery, it is meant that the coolth delivery fluid comes into direct contact with the atmosphere of the contained environment. By indirect coolth delivery, it is meant that the coolth delivery fluid does not come into direct contact with the atmosphere of the contained environment, but instead may come into thermal contact or thermal communication with the contained environment, or into thermal communication with a separate sub-system delivering coolth to the contained environment. The coolth delivery system may comprise a direct coolth absorption configuration or an indirect coolth absorption configuration. By direct coolth absorption, it is meant that the coolth delivery fluid is placed into direct contact with the coolth storage medium. By indirect direct coolth absorption, it is meant that the coolth delivery fluid is not brought into direct contact with the coolth storage medium, but may be brought into indirect or thermal contact with the coolth storage medium. In one embodiment incorporating a direct coolth delivery arrangement, the coolth delivery fluid mixes and becomes a part of the atmosphere of the contained environment. In this embodiment, the coolth delivery interface may comprise a fluid outlet from the coolth delivery conduit, which delivers the fluid into the contained environment. Preferably, according to this embodiment, the composition of the coolth delivery fluid should be compatible with, consistent with or the same as the fluid of the atmosphere of the contained environment. In one embodiment, where the atmosphere of the contained environment is air, the coolth delivery fluid may, for example, be air, oxy gen-depleted air or nitrogen. In another embodiment, in which an indirect coolth delivery arrangement is incorporated, the coolth delivery fluid is not mixed with the atmosphere of the contained environment, but comes into indirect or thermal contact with the atmosphere of the contained environment. For example, the coolth delivery fluid may be circulated through a thermally conductive conduit or pipe or panel that is in contact with the contained environment which then directs the coolth delivery fluid out of contact with the contained environment. In an alternative example, the coolth delivery fluid may heat exchange with a separate circulating fluid which circulates through the contained environment and through a heat exchanger with the coolth delivery fluid. In one embodiment in which a direct coolth absorption arrangement is incorporated, the coolth delivery fluid is brought into direct contact with the coolth storage medium. In this embodiment, the storage interface may comprise a fluid inlet to allow passage of coolth delivery fluid from the energy storage unit into the coolth delivery conduit. The coolth delivery conduit may typically be air or another gaseous or liquid fluid, which is provided to the energy storage unit for direct contact with the coolth storage medium through, for example, a source inlet, e.g. from atmosphere or from a supply conduit. In another embodiment in which an indirect coolth absorption configuration is incorporated, the coolth delivery fluid is not placed into direct contact with the coolth storage medium, but comes into indirect or thermal contact therewith. For example, the coolth delivery fluid may be circulated through a thermally conductive conduit or pipe or panel that is in contact with the coolth storage medium which then leads to the fluid delivery conduit for supply to the contained environment. In an alternative example, the coolth delivery fluid may heat exchange with a separate circulating fluid which circulates through the coolth storage medium and through a heat exchanger with the coolth delivery fluid. The coolth storage interface and the coolth delivery interface may be appropriately configured according to whether the system incorporates a direct or indirect coolth delivery arrangement and a direct or indirect coolth absorption configuration. The coolth delivery system may therefore comprises: a direct coolth absorption configuration and a direct coolth delivery arrangement; a direct coolth absorption configuration and an indirect coolth delivery arrangement; an indirect coolth absorption configuration and a direct coolth delivery arrangement; or an indirect coolth absorption configuration and an indirect coolth delivery arrangement. As mentioned above, the coolth delivery system comprises a coolth delivery conduit for transferring coolth delivery fluid from coolth absorption interface to the coolth delivery interface. In one embodiment, there is no coolth delivery return conduit. Instead, the coolth delivery fluid is delivered via the coolth delivery interface to the contained environment, in a direct coolth delivery arrangement, or the coolth delivery fluid is released (e.g. vented to atmosphere in the case of a gaseous fluid) external to the contained environment downstream of the coolth delivery interface. Optionally, and preferably, the coolth delivery system comprises a fluid return conduit for transferring relatively warm coolth delivery fluid from the coolth delivery interface to the coolth absorption interface. In, one particular arrangement of the coolth delivery system, the coolth absorption configuration is indirect, whereby a coolth delivery fluid is cooled by indirect contact with the coolth storage medium, and the coolth delivery arrangement is direct, whereby the coolth delivery fluid is fed directly into the contained environment. In this embodiment, the system is not circulatory, but one way, with fresh coolth delivery fluid (e.g. air) being drawn into the system via a source inlet before thermal contact with the coolth storage medium. In each case, passage of the coolth delivery fluid through the fluid delivery conduit is preferably driven by a suitable pump, which is operated by a delivery controller. In one embodiment, the coolth delivery fluid may serve to provide pre-cooling to a coolth delivery fluid of a primary contained environment cooling system. In this embodiment, there may be a single coolth delivery fluid which circulates through both the energy storage system and through a primary contained environment cooling system. In another implementation, the coolth delivery interface of the coolth delivery system of the invention may comprise a heat exchanger with the relatively warm fluid of a primary contained environment cooling system whereby heat in the conventional or primary contained environment cooling system is absorbed the coolth delivery fluid and then returned for further cooling by the coolth storage medium via a return conduit or vented to atmosphere. In another embodiment, the coolth delivery system is the sole means for cooling the contained environment. In the case of a refrigerator, the refrigerator may be cooled solely by the coolth delivery system and be absent a conventional compressor-type refrigeration system. In another embodiment, the coolth delivery system is part of a combined system for cooling the contained environment in which the contained environment may be cooled by the coolth delivery system and by a conventional cooling system, such as a refrigerator compressor system. For example, the coolth delivery system may be secondary or subsidiary to, or may be configured to operate in parallel with, a primary or conventional contained environment cooling system, such as a compressionexpansion circuit refrigeration system, whereby the coolth delivery system and the primary or conventional contained environment cooling system are configured to operate independently to cool the contained environment or are configured to operate in cooperation to separately cool the contained environment. In the system of the present invention, the contained environment typically has a door for providing access to the contained environment, the door typically forming a part of the insulating housing. The door, is therefore typically an insulated door. In one embodiment as a coolth delivery interface of a coolth delivery system, and as a further aspect of the invention, there is a door configured for delivery of coolth to the contained environment, which may be referred to as a coolth-delivery door. By providing an adapted door as a coolth delivery interface for the coolth delivery system, the system of the invention may be readily retro-fitted to existing refrigerators. The door of an existing refrigerator may thereby be replaced with a suitably dimensioned coolth-delivery door in order to convert the existing refrigerator into a system of the invention in which the coolth delivery system may be the sole or a combined source of coolth (e.g. combined with the existing refrigerator compressor). The coolth-delivery door may be configured to be a direct or indirect coolth delivery arrangement. That is to say, in one embodiment, the coolth-delivery door may supply coolth to the contained environment of the refrigerator by, for example, thermal exchange (i.e. absorption of heat by the coolth delivery fluid from the atmosphere of the contained environment) through one or more thermally conductive conduits or panels on the inside face of the door, which conduits or panels are supplied with coolth delivery fluid form the energy storage unit. Alternatively, in another embodiment, the coolth-delivery door may supply coolth to the contained environment by direct delivery of coolth delivery fluid to the contained environment. In this embodiment, the coolth delivery fluid, which may be air cooled by the coolth storage medium, may be delivery to the contained environment by one or, preferably, multiple fluid delivery outlets formed in the internal surface of the coolth-delivery door. In either embodiment, the coolth delivery fluid preferably passes through a supply aperture formed in the coolth-delivery door to enable the coolth delivery fluid to pass from a coolth delivery conduit to the coolth delivery interface (whether that is the fluid outlets or the thermally conductive conduits or panels of the coolth-delivery door). Preferably, the supply aperture is positioned close to a hinge edge of the coolth-delivery door, whether that is the top hinge edge or a side hinge edge. The coolth delivery conduit may lead to the supply aperture from a location on the top of, or beneath or to the side of the refrigerator. In one embodiment, the coolth storage unit may be located on top of the refrigerator. Alternatively, in either embodiment of the coolth-delivery door, the coolth storage unit is disposed as a panel in the coolth delivery door itself, within a separate insulated housing, in a panel arrangement. Thus, there is no need for an external aperture in the door and coolth delivery fluid may instead be transferred from the energy storage unit part of the door to a coolth delivery interface part of the coolth-delivery door. In a further aspect of the invention whereby there is provided an apparatus comprising: an apparatus controller; at least one energy storage unit, an energy storage unit comprising: a housing comprising an insulating layer; a coolth storage medium within the housing; an electrically powered cooler, configured to provide electrically powered cooling to cool the coolth storage medium, wherein the electrically powered cooling is variable under the control of the apparatus controller; at least one outlet port; and one or more refrigeration units in fluid communication with the at least one energy storage unit via at least one fluid (e.g. air) conduit, each refrigeration unit comprising: a housing comprising an insulating layer; one or more storage chambers within the housing; and at least one inlet port; and at least one fluid (e.g. air) moving device configured to transport cool fluid (e.g. air) from the at least one energy storage unit to the one or more refrigeration units via the at least one fluid (e.g. air) conduit. With regard to this aspect and, to the extent allowed by the context any of the other aspects disclosed herein, there are further embodiments, options and features described as follows. Notably, the apparatus and system may utilize a coolant fluid (or coolth delivery fluid) (including fluids other than air), by way of heat exchange arrangements provided as coolth delivery interfaces instead of provision of air to the contained environments, where the context allows. The invention thus enables coolth to be selectively stored by operation of the electrically powered cooler under the control of the apparatus and later used for cooling the one or more refrigeration units using the at least one air moving device. The electrically powered cooler may therefore be used when it is advantageous to do so, for example, at a time when electricity prices are relatively low, or when there is a high availability of renewable power, for example wind or solar. In some embodiments, discussed below, multiple refrigeration units may be supplied with cool air from a single energy storage unit, reducing the number of electrically powered cooling devices which are required to maintain multiple refrigerators, for example in a shop setting. In some embodiments, one or more refrigeration units may be formed by recycling existing refrigeration units, further reducing material consumption. The invention also extends in a second aspect to a method of operating the apparatus, the method comprising varying the cooling of the coolth storage medium and causing the at least one air moving device to transport of cool air from the at least one energy storage unit to the one or more refrigeration units via the at least one air conduit. It may be that at least one of the one or more refrigeration units is demountably retained or retainable on a top surface of the at least one energy storage unit. It may be that each of the one or more refrigeration units is demountably retained or retainable on a top surface of the at least one energy storage unit. It may be that a bottom surface of a demountably retained or retainable refrigeration unit comprises features configured to couple with cooperating features of the top surface of the at least one energy storage unit to stably mount a refrigeration unit to the top surface of at least one energy storage unit. It may be that an energy storage unit and a refrigeration unit are coupled to form a single unit. Typically, the energy storage unit is underneath the refrigeration unit (when the energy storage unit is coupled to the refrigeration unit). This arrangement has the benefit of being compact. The apparatus may comprise an apparatus housing which houses both the refrigeration unit and the energy storage unit. It may be that the energy storage unit is installed partially or wholly below ground level (e.g. in a recess in the ground), with the refrigeration unit on top (and extending above or entirely above ground level) such that the apparatus does not take up more space than a conventional refrigeration unit. Typically the outlet port of the at least one energy storage unit is connected to the inlet port of some or all of the one or more refrigeration units by the at least one air conduit. Thus, cool air can be transported from the at least one energy storage unit to the one or more refrigeration units. It may be that the outlet port of each of the one or more energy storage units is configured to connect to the inlet port of a respective one of the one or more refrigeration units while the refrigeration unit is demountably retained thereon. Thus, coolth from the internal cavity of the energy storage unit may be transported directly to the storage chamber of the respective refrigeration unit from the internal cavities of the one or more energy storage units without the need for a further conduit therebetween. Coolth supplied to the storage chamber of the respective refrigeration unit is therefore insulated from the external environment by the insulating layers of the housings of the energy storage unit and the respective refrigeration unit, each of which provides greater insulation than an external conduit, thereby minimising potential losses of coolth to the external environment. It may be that the one or more refrigeration units comprise a plurality of refrigeration units in fluid communication with one energy storage unit. It may be that the at least one air moving device can selectively transport cool air from the one energy storage unit to one or more of the said plurality of refrigeration units. Thus, all of the cooling for a plurality of refrigeration units may be supplied by one energy storage unit, thus reducing materials used (for example only a single electrically powered cooler would be required) and cost of operations in e.g., a shop. It may be that the one energy storage unit is in fluid communication with the plurality of refrigeration units through at least one manifold. It may be that at least one manifold comprises one or more individually controllable (e.g., electronically controllable) valves and / or fans. It may be that the one energy storage unit is in fluid communication with the plurality of refrigeration units through a first air manifold which supplies coolth to the plurality of refrigeration units and a second air manifold which supplies warmth (returns air that is less cool) to the energy storage unit for cooling. Nevertheless, it may be that a plurality of energy storage units are in fluid communication with the plurality of refrigeration units through at least one manifold. A first air manifold may supply coolth to the plurality of refrigeration units and a second air manifold may supply warmth (returns air that is less cool) to the plurality of energy storage units for cooling. It may be that the one or more individually controllable valves are a plurality of individually controllable valves, each one of the plurality associated with a respective one of the plurality of refrigeration units, such that a respective valve may be opened to permit fluid communication between the at least one manifold and the respective refrigeration unit, thereby selectively providing cool air thereto. Cool air may be selectively transported to a selected one or more of the plurality of refrigeration units, for example under the control of the apparatus controller and / or a the refrigeration unit controller. Thus, each individual refrigeration unit of the plurality of refrigeration units may be cooled independently of cooling requirements of each of the other refrigeration units of the plurality of refrigeration units. It may be that each of the plurality of refrigeration units has an optimal operating temperature range. It may be that at least one of the plurality of refrigeration units has an optimal operating temperature range different to the optimal operating temperature range of a different one of the plurality of refrigeration units. It may be that the method comprises selectively supply cool air from the energy storage unit such as to supply different amounts of cool air to different ones of the plurality of refrigeration units. It may be that the method comprises selectively supply cool air from the energy storage unit to a selected one of the plurality of refrigeration units. It may be that the apparatus is configured to cut off (or the method comprises cutting off) the supply of cool air to a refrigeration unit of the plurality of refrigeration units, when the door of the respective refrigeration unit is open, but to concurrently supply cool air to one or more of the remainder of the plurality of refrigeration units. It may be that the plurality of refrigeration units comprises a plurality of separate refrigeration units within a shop. The invention may extend to a shop comprising a said apparatus with a plurality of separate refrigeration units in fluid communication with one energy storage unit. It may be that the insulating layer of the housing of the at least one energy storage unit has a greater thickness than the insulating layers of the housings of the one or more refrigeration units. This can provide a more cost effective or lower material cost option than providing the same thickness of insulation in the housings of the one or more refrigeration units and the at least one energy storage unit. It may be that the operation of the at least one air moving device is variable under the control of the apparatus controller to vary the rate at which coolth is transferred from the at least one energy storage unit to at least one refrigeration unit. The method typically comprises varying the rate at which coolth is transferred from the at least one energy storage unit to at least one refrigeration unit. It may be that the rate at which coolth is transferred from the at least one energy storage unit to the at least one refrigeration unit is dependent on the difference in temperature between the internal temperature of the at least one refrigeration unit and an upper bound of an optimal operating temperature range of the at least one refrigeration unit. Thus, refrigeration units requiring a greater amount of cooling (i.e., with a high internal temperature relative to a target operating temperature thereof) will be supplied coolth at a faster rate to reduce the time taken to reach the target operating temperature. Additionally, refrigeration units requiring only a smaller amount of cooling (i.e., with internal temperatures only slightly above the upper bound of the respective optimal operating temperature range) will be supplied coolth at a slower rate (than those requiring a larger amount of cooling) such that power usage by the at least one air moving device is minimised. It may be that the apparatus controller is configured to implement (and the method comprises carrying out) a temporary energy storage procedure in the at least one energy storage unit, wherein the temporary energy storage procedure comprises causing the electrically powered cooler of the at least one energy storage unit to cause cooling of the coolth store medium, thereby storing electrical energy in the form of coolth. Thus, the apparatus may make use of (and the method may comprise using) electricity based on current electricity availability or price, rather than using electricity as and when cooling is required by the one or more refrigeration units, as is the case in typical refrigeration units. This therefore results in a more efficient use of electricity. It may be that the apparatus controller is configured to implement the temporary energy storage procedure in response to an increased availability of renewable electricity. The method may comprise implementing the temporary energy storage procedure in response to an increased availability of renewable electricity. It may be that at least one of the one or more refrigeration units comprises an electrically powered cooler configured to provide electrically powered cooling to cool the one or more storage chambers of the respective refrigeration unit. It may be that each of the one or more refrigeration units comprises an electrically powered cooler configured to provide electrically powered cooling to cool the one or more storage chambers of the respective refrigeration unit. Thus, cooling can still be provided to the one or more refrigeration units independently without requiring coolth from the energy storage unit. It may be that the one or more refrigeration units comprising an electrically powered cooler are configured to be cooled by their respective electrically powered coolers in response to a detection that there is a limited availability of coolth stored in the coolth storage medium. Thus, items stored within the one or more refrigeration units will still be refrigerated even if the energy storage unit cannot supply coolth thereto. It may be that the one or more refrigeration units comprising electrically powered coolers are configured to be cooled by the respective electrically powered coolers in response to an availability of renewable electricity. Thus, during periods of high renewable electricity availability (e.g., high winds, sunny days) the renewable electricity may be harvested by the at least one energy storage unit through implementation of the temporary storage procedure while also being used to provide power to the electrically powered coolers of the one or more refrigeration units to cool the one or more refrigeration units while the temporary storage procedure is being implemented. It may be that the electrically powered cooling is variable, typically under the control of the apparatus controller. It may be that the one or more refrigeration units are pre-existing refrigeration units repurposed for use in the apparatus, for example, by removal of an existing compressor and addition of an inlet port. Thus, standard refrigeration units need not be replaced when installing the system, merely integrated. This reduces waste and increases viability of widespread adoption, as consumers (e.g., shop owners) may use their existing hardware as the one or more refrigeration units of the apparatus. It may be that the cool th storage medium comprises a material which changes phase at a temperature within the operating temperature range of the at least one energy storage unit. It may be that each of the one or more refrigeration units comprises a door. It may be that each energy storage unit is sealed. It may be that each energy storage unit has a space (e.g. a gap), typically at the top, typically within the energy storage unit, to enable airflow. Thus, the one or more storage chambers of each of the or more refrigeration units are able to be accessed by a user when the respective door is in an open configuration, while providing a sealed, insulated internal environment when in a closed configuration. The door may comprise a seal to minimise potential coolth lost through the door when in a closed configuration. The door may be hingeably attached to a side wall of the housing of the respective refrigeration unit. The door may comprise a handle for ease of opening. The door may open via a sliding mechanism. The door may provide additional insulation to a front portion of the respective refrigeration unit. The door may comprise a door sensor. The door sensor may be in communication with the apparatus controller and may send signals thereto in response to a detection that the door has been opened and in response to a detection that the door has been closed. Thus, the apparatus controller will have information on the current status of each of the doors of each of the one or more refrigeration units. The status of a door may be taken into account by the apparatus controller when deciding whether a cooling procedure should be implemented for the respective refrigeration unit. For example, if the apparatus controller has received a signal indicating that the door to a respective refrigeration unit has been opened but has not yet received a signal indicating that the door has been shut, it may choose not to implement a cooling procedure until a signal has been received indicating the door has been shut, or until a predetermined period Of time has passed without receiving said signal. Thus, unnecessary coolth loss through doors in open configurations can be mitigated. It may be that the apparatus controller initiates a cooling procedure (and the method may comprise initiating a cooling procedure) whenever the door sensor sends a signal indicating that a door has been shut, thus ensuring the internal temperature of the respective refrigeration remains within the optimal operating temperature range without the temperature having to have first exceeded a threshold temperature. The cooling procedure may be causing the at least one air moving device to transport cool air. The cooling procedure may be causing the electrically powered cooler to cool the coolth storage medium. The door may comprise an alarm system configured to activate if the door has been left open for a predetermined amount of time. Thus, a user may be alerted to the open door to prevent unnecessary coolth loss. It may be that one or more refrigeration units comprises a material which changes phase at a temperature within the operating temperature range of the refrigeration unit, to buffer temperature changes. It may be that the air moving device comprises a fan, and wherein the air moving device further comprises a battery power supply for the fan. The method may comprise powering the air moving device (e.g. a fan) from a battery. Thus, the air moving device may be used to transfer coolth to the one or more refrigeration units when power is not available, for example during mains power outages. It may also be more energy efficient in some circumstances to use a battery to power the fan than to keep the power supply for the compressor operational. Thus, the battery power supply may be operated to power the fan when the compressor is not powered and / or when mains power is not available. It may be that the electrically powered cooler comprises an electrically powered compressor. The electrically powered cooler may comprise a Peltier pump. The method may comprise varying the electrically powered cooling by switching on and off the electrically powered cooler. The refrigeration unit may be in thermal communication with (optionally may encompass) one or more computer servers. The present invention further extends to a building comprising an apparatus as described hereinbefore, the building comprising a plurality of rooms (or server computers) and an air conditioning manifold in gaseous communication with the plurality of rooms to regulate the temperature of the plurality of rooms (or server computers), wherein the energy storage unit is controllably connected to the air conditioning manifold to thereby selectively provide cooled air to the plurality of rooms (or server computers). In accordance with a further aspect of the invention, there is provided an energy storage unit comprising: a housing comprising an insulating layer; a coolth storage medium within the housing; an electrically powered cooler, configured to provide electrically powered cooling to cool the coolth storage medium, wherein the electrically powered cooling is variable under the control of the apparatus controller; at least one outlet port; wherein the energy storage unit is configured to operate as the energy storage unit described hereinbefore. In accordance with a still further aspect of the invention, there is provided an apparatus comprising: a controller; an energy storage unit comprising: a coolth storage medium; and an electrically powered cooler configured to provide electrically powered cooling to cool the coolth storage medium, wherein the electrically powered cooling is variable under the control of the controller; wherein the controller is configured to use information based on meteorological data to determine whether a renewable energy availability condition has been satisfied, wherein the controller is configured to use information based on meteorological data to predict when the renewable energy availability condition will be satisfied, and wherein the controller is configured to cause the electrically powered cooler to provide electrically powered cooling of the coolth storage medium upon satisfaction or predicted satisfaction of the renewable energy availability condition, such that the electrically powered cooler is powered by renewable sources of electricity, thereby storing renewable energy in the form of coolth. Typically the energy storage unit further comprises at least one outlet port. In accordance with a still further aspect of the invention, there is provided a method of operating an apparatus, the apparatus comprising: an energy storage unit comprising: a coolth storage medium; and an electrically powered cooler configured to provide electrically powered cooling to cool the coolth storage medium, wherein the electrically powered cooling is variable under the control of the controller; the method comprising: receiving information based on meteorological data, using the information to determine or predict when a renewable energy availability condition has been or will be satisfied, and causing the electrically powered cooler to provide electrically powered cooling of the coolth storage medium upon satisfaction or predicted satisfaction of the renewable energy availability condition such that the electrically powered cooler is powered by renewable sources of electricity, thereby storing renewable energy in the form of coolth. Typically the apparatus further comprises one or more refrigeration units in fluid communication with the at least one energy storage unit via at least one air conduit, each refrigeration unit comprising: a housing comprising an insulating layer; one or more storage chambers within the housing; and at least one inlet port; and at least one air moving device configured to transport cool air from the at least one energy storage unit to the one or more refrigeration units via the at least one air conduit. Thus, the apparatus is typically also an apparatus according to the first aspect of the invention. It may be that the meteorological data comprises wind speed data. It may be that the renewable energy is wind power. It may be that the meteorological data comprises cloud cover data. It may be that the meteorological data comprises sunlight strength data. It may be that the renewable energy is solar power. The apparatus typically takes into account the location of the energy storage unit. The meteorological data may be received from one or more sensors. The one or more sensors may comprise temperature, pressure, wind speed and / or wind direction sensors. One or more sensors may be located on an orbital satellite. The availability condition may be an availability below a threshold. Thus, cooling of the coolth storage medium may take place in advance of a low availability of renewable power. The invention will now be described in more detail, without limitation, with reference to the accompanying Figures. In Figure 1, which is a schematic diagram of a system of an embodiment of the invention, the system 100 comprises an apparatus 112 for storing energy as coolth which may then be used in refrigeration. The apparatus 112 comprises a refrigeration unit 116 for refrigerating items stored within. The refrigeration unit 116 comprises a housing 118 defining a storage chamber 120, the housing 118 comprising an outer shell 122, an insulating layer 124, and a door 128 hingeably attached to and forming a front portion of the housing 118, which provides access to the storage chamber 120 when in an open configuration (shown in Figure 1) and provides a sealed, insulated environment when in a closed configuration (not shown). The housing 118 defines a coolth inlet 130 (functioning as the inlet port) extending from the storage chamber 120 through the base of the housing 118 and a warmth outlet 134 defined by a side wall 136 of the housing 118 at a height at least as high as half of the vertical extent of the storage chamber 120, the warmth outlet 134 extending from the storage chamber 120 through the side wall 136 to a warm air conduit 138 (functioning as the air conduit). A first air moving device 146 is provided within the coolth inlet 130 to move cool air into the storage chamber 120, and a second air moving device 148 is provided within the warmth outlet 134 to move warm air out of the storage chamber 120 and into the warm air conduit 138. The storage chamber 120 is further provided with a first temperature sensor 144 for measuring the temperature of the air within the storage chamber 120. The apparatus 112 further comprises an energy storage unit 150 upon a top surface of which the refrigeration unit 116 is demountably retained. The energy storage unit 150 comprises a housing 152 for housing the various portions thereof. A first portion of the energy storage unit 150 is an energy storage portion 154 comprising an energy storage cartridge 166 filled with a phase change material 168 (functioning as the coolth storage medium) for the storage of energy as coolth. The energy storage cartridge 166 sits within an internal cavity 160 which is surrounded and defined by an insulating layer 156 of the energy storage portion 154. The internal cavity 160 is in fluid communication with the storage chamber 120 of the refrigeration unit 116 via a coolth outlet 162 (functioning as the outlet port) which extends from the internal cavity 160 through the insulating layer 156 of the energy storage portion 154 and the housing 152 of the energy storage unit 150 and aligns with the coolth inlet 130 of the refrigeration unit 116 to form a sealed channel through which air can move. The internal cavity 160 is in further fluid communication with the warm air conduit 138 via a warmth inlet 164 (functioning as the inlet port) defined by the housing 152 of the energy storage unit 150 and the insulating layer 156 of the energy storage portion 154 and extending therethrough from the warm air conduit 138 to the internal cavity 160. The internal cavity 160 is further provided with a second temperature sensor 161 for measuring the temperature of the air within the internal cavity 160. The energy storage unit 150 further comprises a second portion in the form of a control portion 170 comprising an electrically powered cooler comprising a compressor 172 for cooling the phase change material 168 of the energy storage cartridge 166, a first power supply unit 174 for powering the compressor 172, a second power supply unit 176 which supplies power to the first and second air moving devices 146, 148, and a third power supply unit 178 for providing backup power to the first and second air moving devices 146, 148. The control portion 170 further comprises an apparatus controller 180 for controlling the first, second, and third power supply units 174, 176, 178 to thereby control the activation of the compressor 172 and the first and second air moving devices 146, 148, and for receiving data from the first and second temperature sensors 144, 161 and a network 114 of the system 100. The energy storage unit 150 is further provided with a third portion in the form of a heat transfer portion 182 abutting the insulating layer 156 of the energy storage portion 154. The heat transfer portion 182 comprises a heat absorbing medium 184 surrounding a condenser unit 186 for discarding heat energy removed from the phase change material 168 during freezing into the heat absorbing medium 184. The heat absorbing medium 184 further surrounds a heat exchanger 188 comprising an inlet pipe 190 through which cold water is pumped, a heat extraction portion 192 for circulating the cold water from the inlet pipe 190 through the heat absorbing medium 184 to absorb the heat accumulated within, and an outlet pipe 194 for transferring the water warmed in the heat extraction portion 192 away from the apparatus 112. The system 100 further comprises a plurality of sensors 102 for collecting meteorological data at various locations. The sensors 102 are in communication with a server 104 which comprises a first memory 106 for storing data received from each of the sensors 102, a second memory 108 for storing location data of the apparatus 112, and a processor 110 which produces information using the data stored in the first and second memories 106, 108. This information is communicated from the processor 110 to the apparatus 112 via the network 114. The operation of an embodiment of a system according to Figure 1 will now be described. The plurality of sensors 102 are positioned to measure meteorological conditions (e.g., wind speed) at a plurality of locations situated in the vicinity of a wide array of renewable energy power stations (e.g., wind farms). The sensors send meteorological data to the server 104 where they are stored in the first memory 106. The processor 110 retrieves and processes the data using machine learning and predictive analytics software to predict the availability of renewable energy at the plurality of locations. If the processor 110 predicts a spike in availability of renewable energy, e.g., it predicts an increase in wind speed, at a particular location, the processor 110 will identify the location of this spike, retrieve location data from the second memory 108 to identify apparatuses near to this location, and send signals to those apparatuses via the network 114. When the apparatus controller 180 of the apparatus 112 receives confirmation that there is an availability of renewable energy in the electricity grid from the server 104 via the network 114, it will initiate a temporary energy storage procedure by sending a signal to the first power supply unit 174 to turn on the compressor 172. The compressor will then begin changing the phase of (i.e., freezing) the phase change material 168 in the energy storage cartridge 166 and will continue until the phase change material is completely frozen and has reduced to a minimum threshold temperature, measured by the second temperature sensor 161, at which point the apparatus controller will send a signal to switch off the first power supply unit off. The available renewable energy has therefore been harvested by the apparatus for use at a later time. During the cooling of the phase change material 168, the thermal energy removed from the energy storage cartridge 166 is discarded through the condenser unit 186, where it is absorbed by the heat absorbing medium 184 and carried away from the apparatus via the heat exchanger 188. The water which circulates through the heat exchanger is warmed by the heat stored in the heat absorbing medium. This warmed water may then be used for another purpose. A user who wishes to use the apparatus 112 to refrigerate items, for example, food items, will open the door 128 of the refrigeration unit 116, place the items within the storage chamber 120, and closes the door. The internal temperature of the refrigeration unit will increase upon opening the door, as ambient temperature air will be allowed to enter the storage chamber and cooled air allowed to exit the storage chamber. Once the door has been shut again, the temperature of the air within the storage chamber will continue to rise as the higher-temperature items will transfer their heat energy to the lower-temperature surroundings. This internal temperature is measured by the first temperature sensor 144. It may be that the first temperature sensor sends temperature data to the apparatus controller 180 continuously, and the apparatus controller monitors the incoming data to determine whether the temperature has surpassed a threshold value, or it may be that the temperature sensor only sends a signal to the apparatus controller once it detects that the temperature threshold has been surpassed. This threshold value may be static and predetermined, or it may be dynamically assigned based on other factors (e.g., whether the door is open or closed). Once the apparatus controller has determined that the temperature inside the storage chamber has exceeded this threshold value, the apparatus controller will initiate a cooling procedure by switching on the second power supply unit 176 which will activate the first and second air moving devices 146, 148. It may be that apparatus is further provided with a door sensor (not shown), which will send a signal to the apparatus controller upon detection that the door has been opened and closed, and the apparatus controller may initiate a cooling procedure in response to receiving this signal. It may be that the operation of the air moving devices is variable and controllable by the apparatus controller and is dependent on how much cooling is required. For example, the speed of an air moving device in the form of a fan may be dependent on the difference in temperature between the current internal temperature and the target operating temperature, such that the fan spins at a greater rotational rate in response to large differences in temperature. Activation of the first air moving device 146 causes air within the internal cavity 160 of the energy storage unit 150, which has been cooled by the frozen phase change material 168 of the energy storage cartridge 166, to be moved out of the internal cavity 160 through the coolth outlet 162 by the first air moving device and into the storage chamber 120 of the refrigeration unit 116 via the coolth inlet 130, thereby reducing the internal temperature of the refrigeration unit. The activation of the second air moving device 148 will cause the warmer air towards the top half of the storage chamber to be moved out of the storage chamber through the warmth outlet 134 where it will be transported through the warm air conduit 138 and back into the internal cavity of the energy storage unit via the warmth inlet 164. The warmer air entering the internal cavity will be circulated past the frozen phase change material of the energy storage cartridge and will be cooled as a result. This cooler air will then be cycled back into the storage chamber to continue the cycle. Typically, the warmer air returning to the energy storage unit will be cooler than ambient air, and so this is more energy efficient than taking in fresh atmospheric air. Once the apparatus controller 180 detects that the internal temperature of the refrigeration unit has dropped to below a second threshold temperature, i.e., at a temperature suitable for refrigeration, the apparatus controller will send a signal to switch off the second power supply unit, thus ceasing the controlled circulation of air within the apparatus. Figure 2 is a schematic diagram of an apparatus in accordance with a further embodiment of the present invention. The apparatus 200 comprises an energy storage unit 250 for storing electricity as coolth. The energy storage unit 250 is substantially similar to the energy storage unit 150 of Figure 1, apart from the hereinafter described differences. Like features are illustrated with like reference numbers, with the first digit changing from 1 to 2, to indicate that the feature is relevant to Figure 2 instead of Figure 1 (e.g., the housing 152 of the energy storage unit 150 of Figure 1 corresponds to the housing 252 of the energy storage unit 250 of Figure 2). Specifically, the energy storage unit 250 includes a housing 252, an energy storage portion 254, an insulating layer 256, an internal cavity 260, a temperature sensor 261, a coolth outlet 262, a warmth inlet 264, an energy storage cartridge 266, a phase change material 268, a control portion 270, a compressor 272, a first power supply unit 274, an apparatus controller 280, a heat transfer portion 282, a heat absorbing medium 284, a condenser unit 286, a heat exchanger 288, an inlet pipe 290, a heat extraction portion 292, and an outlet pipe 294. The apparatus 200 further comprises a first refrigeration unit 216A, a second refrigeration unit 216B, and a third refrigeration unit 216C, each for refrigerating items stored within, wherein each refrigeration unit is substantially similar to the refrigeration unit 116 of Figure 1, apart from the hereinafter described differences. Like features are illustrated with like reference numbers, with the first digit changing from 1 to 2, to indicate that the feature is relevant to Figure 2 instead of Figure 1 and a reference letter A, B, or C added to indicate that the feature belongs to the first, second, or third refrigeration unit 216A, 216B, or 216C, respectively (e.g., the storage chamber 120 of the refrigeration unit 116 of Figure 1 corresponds to the storage chamber 220B of the second refrigeration unit 216B of Figure 2). Specifically, the first refrigeration unit 216A includes a housing 218A, a storage chamber 220A, an outer shell 222A, an insulating layer 224A, a door 228A, a coolth inlet 230A, a warmth outlet 234A, and a temperature sensor 244A. Similarly, the second refrigeration unit 216B includes a housing 218B, a storage chamber 220B, an outer shell 222B, an insulating layer 224B, a door 228B, a coolth inlet 230B, a warmth outlet 234B, and a temperature sensor 244B. The third refrigeration unit 216C includes a housing 218C, a storage chamber 220C, an outer shell 222C, an insulating layer 224C, a door 228C, a coolth inlet 230C, a warmth outlet 234C, and a temperature sensor 244C. The first refrigeration unit 216A is further provided with a door sensor 225A for detecting that the door 228A of the first refrigeration unit has been opened or closed and, in response to this detection, sending signals to the apparatus controller 280. Similarly, the second refrigeration unit 216B is further provided with a door sensor 225B for detecting that the door 228B of the second refrigeration unit has been opened or closed and, in response to this detection, sending signals to the apparatus controller 280, and the third refrigeration unit 216C is further provided with a door sensor 225C for detecting that the door 228C of the third refrigeration unit has been opened or closed and, in response to this detection, sending signals to the apparatus controller 280. The first, second, and third refrigeration units 216A, 216B, 216C are further provided with respective door sensors 225A, 225B, 225C for detecting that the respective doors 228A, 228B, 228C have been opened or closed and, in response to these detections, sending signals to the apparatus controller 280. In the embodiment represented in Figure 2, the energy storage unit 250 is in fluid communication with each of the first, second, and third refrigeration units 216A, 216B, 216C via a common coolth conduit 232 (functioning as the air conduit) which extends from the coolth outlet 262 of the energy storage unit 250. The common coolth conduit 232 comprises a first branch portion 233A extending from a main trunk portion 233D to the coolth inlet 230A of the first refrigeration unit 216A, a second branch portion 23 3B extending from the main trunk portion 23 3D to the coolth inlet 23 OB of the second refrigeration unit 216B, and a third branch portion 233C extending from the main trunk portion 233D to the coolth inlet 230C of the third refrigeration unit 216C. A first valve 235A is positioned within the first branch portion 233A of the common coolth conduit which may be in an open state (as shown in Figure 2) to permit, or in a closed state (not shown) to prohibit, the movement of air between the main trunk portion 233D of the common coolth conduit 232 and the storage chamber 220A of the refrigeration unit 216A. Similarly, second and third valves 235B, 235C are positioned within the second and third branch portions 233B, 233C, respectively, to selectively permit or prohibit fluid communication between the main trunk portion 233D and the storage chambers 220B, 220C of the second and third refrigeration units 216B, 216C respectively. The first, second, and third valves 235A, 235B, and 235C are each individually controlled by the apparatus controller 280 which is configured to selectively actuate the valves depending on the cooling requirements of the individual refrigeration units. The energy storage unit 250 is in further fluid communication with each of the refrigeration units 216A, 216B, 216C via a common warmth conduit 242 comprising a first branch portion 243A extending from the warmth outlet 234A of the first refrigeration unit 216A to a main trunk portion 243D, a second branch portion 243B extending from the warmth outlet 234B of the second refrigeration unit 216B to the main trunk portion 243D, and a third branch portion 243C extending from the warmth outlet 234C of the third refrigeration unit 216C to the main trunk portion 243D, the main trunk portion 243D extending from the first, second, and third branch portions 243A, 243B, 243C to the warmth inlet 264 of the energy storage unit 250. The first branch portion 243A is provided with a first air moving device 245A for moving warm air out of the storage chamber 220A of the first refrigeration unit 216A so that it may be cycled back to the 24 energy storage unit 250 via the main trunk portion 243D of the common warmth conduit 242. Similarly, the second and third branch portions 243B, 243C are provided with second and third air moving devices 245B, 245C, respectively, for moving warm air out of the storage chambers 220B, 220C of the second and third refrigeration units 216B, 216C, respectively so that the warm air may be cycled back to the energy storage unit 250 via the main trunk portion 243D of the common warmth conduit 242. The warmth inlet 264 of the energy storage unit 250 is further provided with a fourth air moving device 255 for moving warm air from the common warmth conduit 242 into the internal cavity 260. The coolth outlet 262 of the energy storage unit 250 is further provided with a fifth air moving device 265 for moving cool air from the internal cavity into the common coolth conduit 242 to thereby promote the flow of coolth into the storage chambers 220A, 220B, 220C of the first, second, and third refrigeration units 216A, 216B, 216C. The main trunk portions 23 3D, 243D of the common coolth conduit 232 and the common warmth conduit 242 may comprise further air moving devices (not shown) to further promote airflow therethrough. The operation of an apparatus in accordance with Figure 2 will now be described. When the apparatus controller 280 of the apparatus 200 receives confirmation that there is an availability of renewable energy in the electricity grid, which meets a predetermine criteria (e.g. as to amount of renewable energy available) from a server (not shown) via a network (not shown), it will initiate a temporary energy storage procedure by sending a signal to the first power supply unit 274 to turn on the compressor 272. The compressor will then begin cooling, and thereby changing the phase of (i.e., freezing) the phase change material 268 in the energy storage cartridge 266 and will continue until the phase change material is completely frozen and reduced to a threshold temperature, measured by the temperature sensor 261 of the energy storage unit 250, at which point the apparatus controller will send a signal to switch off the first power supply unit off. The available renewable energy has therefore been harvested by the apparatus for use at a later time. During the cooling of the phase change material 268, the thermal energy removed from the energy storage cartridge 266 is discarded through the condenser unit 286, where it is absorbed by the heat absorbing medium 284 and carried away from the apparatus 200 via the heat exchanger 288. The water which circulates through the heat exchanger is warmed by the heat stored in the heat absorbing medium. This warmed water may then be used for another purpose. The apparatus 200 may be situated within, e.g., a shop 205, wherein each refrigerator may require a different cooling regime based on how often each door is opened and how long each door is left open for. While Figure 2 only includes three refrigeration units, it will be understood that the apparatus may contain fewer than three, e.g., two, or more than three, e.g., ten, refrigeration units. The apparatus controller 280 uses data from the first, second, and third temperature sensors 244A, 244B, 244C to determine whether a cooling procedure is required by the first, second, or third storage chambers 220A, 220B, 220C, respectively. The apparatus controller also uses data from the door sensors 225A, 225B, 225C to determine the current status of each of the doors 228A, 228B, 228C to ensure that the door to a respective refrigeration unit is in a closed state before initiating a cooling procedure for the respective refrigeration unit to prevent unnecessary loss of coolth. If at least one storage chamber is deemed to require (and deemed to be suitable for) cooling, the apparatus controller initiates a cooling procedure by activating the fourth and fifth air moving devices 255, 265 to move air through the internal cavity 260 of the energy storage unit 250 and expel coolth through the coolth outlet to the common coolth conduit 232. The apparatus controller will then cause only the valves corresponding to refrigeration units which require and are deemed suitable for cooling to open, thus allowing the coolth in the main trunk portion 233D of the common coolth conduit to enter the branch portions and storage chambers corresponding to those refrigeration units. The apparatus controller sends additional signals to the air moving devices 245A, 245B, 245C corresponding to the refrigeration units undergoing cooling to draw warm air out of the respective storage chambers and into the respective branch portions 243A, 243B, 243C of the common warmth conduit. The warm air is then drawn 19 through the common warmth conduit and expelled into the internal cavity 260 of the energy storage unit 250 via the warmth inlet 264. As the warm air circulates past the energy storage cartridge 266 within the internal cavity 260 it is cooled by the frozen phase change material 268 and the cycle can repeat. If at any point the door sensors detect that a door to a refrigeration unit undergoing a cooling cycle has been opened, the apparatus controller will send signals to close and deactivate the corresponding valve and air moving device, respectively, to stop the cooling process and minimise coolth loss. The cooling procedure may be initiated once again once the door sensor has detected that the door has been closed. If the apparatus controller detects that an additional storage chamber requires cooling while a cooling procedure is already underway, the apparatus controller will send signals to open the corresponding valve and activate the corresponding air moving device to allow the storage chamber to receive the coolth from the common coolth conduit. Once the temperature in the storage chamber has returned to a target value, which may be within or may be below the optimal operating range of the refrigeration device, the apparatus controller 280 will send signals to close the corresponding valve and deactivate the corresponding air moving device. Once all of the valves of the apparatus are closed, the apparatus controller will cease the cooling procedure entirely by deactivating the fourth and fifth air moving devices. In an example scenario for the apparatus 200, the temperature sensor 244A of the refrigeration unit 216A detects that the air within storage chamber 220A has exceeded a threshold value and sends a signal to the apparatus controller 280. The apparatus controller 280 checks whether a signal has been received from the door sensor 225A to indicate that the door 228A is in an open configuration. In this scenario, the door is closed, so no such signal has been received. The apparatus controller 280 therefore initiates a cooling procedure by activating the fourth and fifth air moving devices 255, 256 to begin the circulation of air through the internal cavity 260 of the energy storage unit 250 and into the common coolth conduit 232. Simultaneously, the apparatus controller 280 sends a signal to open the first valve 23 5A such that air moving through the main trunk portion 233D of the common coolth conduit 232 may enter the storage chamber 220A through the coolth inlet 230A via the first branch portion 233 A of the common coolth conduit 232. The apparatus controller also sends a signal to activate the first air moving device 245A such that warm air may be expelled from the storage chamber 220A through the warmth outlet 234A and the first branch portion 243A of the common warmth conduit 242 to the main trunk portion 243D thereof, where it is then cycled back to the energy storage unit 250 for cooling. Once the temperature in the storage chamber 220A of the first refrigeration device has returned to a value within the optimal operating range thereof, the apparatus controller 280 will send signals to close the first valve 235A and deactivate the first air moving device 245A. Once all of the valves of the apparatus are closed, the apparatus controller will cease the cooling procedure entirely by deactivating the fourth and fifth air moving devices. It may be that the apparatus controller chooses to initiate a cooling procedure in response to a prediction that there is currently a high availability of renewable power or that there will soon be a reduced availability of renewable power. This will involve initiating a cooling procedure with all of the valves and all of the air moving devices in the apparatus open and activated, respectively, until all of the coolth stored in the phase change material is used up and the refrigeration devices have been cooled to a temperature below the typical operating range thereof. The valves will then be closed and the air moving devices deactivated to preserve the extra coolth within the storage chambers of the refrigeration units. This will allow a maximum amount of renewable power to be harvested by the energy storage unit while extending the period of time for which the internal temperature of the refrigeration units is below the threshold temperature value. It may be that the apparatus controller chooses to initiate a cooling procedure in response to one or more of: a restock of items in a shop; door being left open for significant amount of time; the internal temperature within a refrigeration unit continuing to rise significantly once door is shut; or a user selection of a manual “restock” option through a user interface (e.g., a 11 button). Usefully, even though electrical power provided through a grid typically comprises electrical power produced by a mixture of both renewable power and non-renewable power (e.g. power from the combustion of fossil fuels), by timing cooling for when renewable power is available close to the apparatus, the proportion of electrical power used by the apparatus which comes from renewable power sources will be increased. In the apparatus of Figure 2 it is beneficial from an environmental and material consumption perspective to have required only one compressor to regulate the temperature in multiple refrigeration units. Figure 3 is a schematic diagram of an energy storage unit in accordance with a further embodiment of the present invention for storing electricity as coolth. The energy storage unit 300 is substantially similar to the energy storage unit 150 of Figure 1, apart from the hereinafter described differences. Like features are illustrated with like reference numbers, with the first digit changing from 1 to 3, to indicate that the feature is relevant to Figure 3 instead of Figure 1 (e.g., the housing 152 of the energy storage unit 150 of Figure 1 corresponds to the housing 352 of the energy storage unit 300 of Figure 3). Specifically, the energy storage unit 300 includes a housing 352, a control portion 370, a compressor 372, a first power supply unit 374, an apparatus controller 380, a heat transfer portion 382, a heat absorbing medium 384, a condenser unit 386, a heat exchanger 388, an inlet pipe 390, a heat extraction portion 392, and an outlet pipe 394. The energy storage unit 300 further comprises an energy storage array 357, comprising first, second, and third energy storage portions 354A, 354B, 354C, functioning as the coolth storage modules, wherein each energy storage portion is substantially similar to the energy storage portion of Figure 2, apart from the hereinafter described differences. Like features are illustrated with like reference numbers, with the first digit changing from 2 to 3, to indicate that the feature is relevant to Figure 3 instead of Figure 2 and a reference letter A, B, or C added to indicate that the feature belongs to the first, second, or third energy storage portion 354A, 354B, or 354C, respectively (e.g., the insulating layer 256 of the energy storage portion 254 of Figure 2 corresponds to the insulating layer 356A of the first energy storage portion 354A of the energy storage portion array 357 of Figure 3). Specifically, the first energy storage portion 354A includes an insulating layer 356A, an internal cavity 360A, a coolth outlet 362A, a warmth inlet 364A, an energy storage cartridge 366A, and a phase change material 368A. Similarly, the second energy storage portion 354B includes an insulating layer 356B, an internal cavity 360B, a coolth outlet 362B, a warmth inlet 364B, an energy storage cartridge 366B, and a phase change material 368B. The third energy storage portion 354C includes an insulating layer 356C, an internal cavity 360C, a coolth outlet 362C, a warmth inlet 364C, an energy storage cartridge 366C, and a phase change material 368C. Thus, in this embodiment, the phase change material is divided into multiple portions located in multiple storage portions. The coolth outlets 362A, 362B, 362C of each individual storage portion may be connected to a different individual refrigeration unit although, in some embodiments, two or more storage portions may be connected to the same refrigeration unit and / or an individual storage portion may be connected to multiple refrigeration units. In use, during cooling, the phase change materials 368A, 368B, 368C within the different energy storage portions are cooled in turn. If there is a limited supply of renewable energy it may be that the phase change materials of only some of the energy storage portions are cooled and where there is a high supply of renewable energy, or there is a prediction of an extended period of time with a low supply of renewable energy, the phase change materials of all of the energy storage portions are cooled. In some embodiments, for example where individual storage portions are connected to individual refrigeration units then they may supply cool th at different rates. Optionally, in any of the embodiments described above in relation to Figures 1 to 3, the air conduit and air moving device may be substituted with a cooling fluid circulation system whereby a cooling fluid or coolth delivery fluid is circulated through the circulation system and whereby coolth is delivered to the refrigeration unit(s) by way of heat exchanging interfaces and coolth is captured from the coolth storage units by a heat exchanging interface (e.g. thermally conductive coil or conduit). Optionally, where the context allows, the refrigeration unit as described in relation to Figures 1 to 3 may, in the alternative be substituted for any contained environment where there is a need or desire for cooling, such as a room (preferably an insulated room), such as a clinic or storage repository, or computer plant room or home / house. In Figure 4, illustrating a particular embodiment of the systems of the invention, there is a space cooling system 401 comprising a system for cooling 403 and a contained environment 405. The system for cooling 403 the contained environment 405 comprises an energy storage unit 407 that includes an insulated housing 409 for storing a coolth storage medium (not shown), which may be a phase change material, such as water. The energy storage unit 407 further comprises an electrically powered cooler 411 that has a cooler power source connection 413, which may be an off-grid source (such as a solar panel or a battery), but is typically a power grid connection. The system for cooling 403 further comprises a coolth delivery system 415 as a sub-system thereto. The coolth delivery system 415 has a coolth delivery conduit for movement of a coolth delivery fluid (not shown) that has been cooled by the coolth storage medium in the energy storage unit 407 to a coolth delivery interface 419 in the form of a heat exchanger (e.g. a thermally conductive panel or coil of conduit) within the contained environment 405, where it serves to cool the contained environment (i.e. thermal energy is absorbed by the coolth delivery fluid at the coolth delivery interface 419 from the contained environment 419). The ‘warmed’ coolth delivery fluid can then return via return conduit 421 to the energy storage unit 407 for cooling again. The coolth delivery system 415 circuit is completed by a coolth absorption interface 423 within the energy storage unit 407. Relatively warm coolth delivery fluid is returned via the return conduit 421 to the coolth absorption interface 423, where it is cooled by the coolth storage medium and circulates through the coolth delivery conduit 417 to the coolth delivery interface 419 to cool the contained environment 405 as needed. The coolth absorption interface may be any suitable means for transferring coolth from the coolth storage medium to the coolth delivery fluid (i.e. by which the coolth storage medium can absorb thermal energy from the coolth delivery fluid), and may be a thermally conductive conduit that coils or zig-zags or spirals or, by any other suitable configuration, passes through the coolth storage medium. The circulation of the coolth delivery fluid through the coolth delivery system 415 is driven by a circulation pump 425. The coolth delivery fluid may be any suitable energy-carrying fluid, and may be a gas, such as air, but is preferably a liquid, such as an aqueous liquid and may be water with an antifreeze agent to ensure it has a lower freezing point than water. The circulation pump 425 is controlled by a controller 427 according to one or more pre-determined criteria that may include the temperature falling below a pre-determined level and, possibly, predicted future behaviour of the user(s) of the contained environment. The controller 427 may be provide with data from a sensor 429 (and one or more further sensors) that provides data that corresponds to the temperature in the contained environment. While, typically, the sensor 429 is a temperature sensor in the contained environment, it may be a pressure, light or contact-sensor that indicates when a door or other aperture (not shown) to the contained environment is opened (and may lead to temperature rise within the contained environment). Thus, cooling is provided to the contained environment under the control of the controller 427 according to certain predetermined or adapting criteria based, at least in part, upon sensor data from the at least one sensor 429. Controller 427 may also control the operation of the electrically-powered cooler 411 according to one or more sets of pre-determined or actively developing criteria, including criteria corresponding to the availability or predicted availability of renewable energy-derived electricity and / or electricity having a cost below a defined threshold and / or the predicted frequency, magnitude and / or duration of generated demand factors, which may be learned for the particular contained environment (e.g. by an artificial intelligence / machine learning correlation engine). Relevant data for use by the controller may be stored locally to the controller or in one or more remote servers, which may be accessed, for example, by a wireless connector 431. In Figures 5 A and 5B which illustrate a coolth delivery interface 519 according to one embodiment in top and front views respectively, the coolth delivery interface 519 comprises a plate member which may be a glass plate, for example, for use as a shelf in a refrigerator, or a more thermally conductive plate, such as a metal plate. Mounted to one side of the plate member 533, or disposed within it, is a thermally conductive fluid conduit 535 (e.g. of copper) disposed in a suitable arrangement whereby for distribution of coolth from across a substantial area of the plate member 533. An interface inlet port 537 and an interface outlet port 539 provide connections for connecting to a coolth delivery conduit and coolth return conduit (not shown). As illustrated in Figure 6, a refrigerator body 641 has a plurality of glass shelves 645, one of which has been replaced by a coolth delivery interface 619 of the type illustrated in Figures 5 A and 5B and comprising a glass plate member 633 with the thermally conductive fluid conduit 635 disposed beneath. The refrigerator body 641 has two access apertures 643 to enable a coolth delivery and a coolth return conduit (not shown) to access the contained space defined by the refrigerator body 641 in order to deliver coolth delivery fluid to the interface inlet and outlet ports of the interface 619. The circulation of coolth delivery fluid through the coolth delivery interface 619 serves to cool the interior space (contained environment) of the refrigerator body 641 (by absorbing thermal energy from the interior space) as required and typically under the control of a controller (not shown). Optionally, a fan (not shown) may be provided within the refrigerator body 641 or integral with the coolth delivery interface 619 in order to circulate cooled air within the refrigerator body 641. Figure 7 illustrates a refrigerator 747 according to the invention in which a coolth delivery door 749 has been fitted to a refrigerator body 741. The coolth delivery door 749 comprises a coolth delivery interface 719 having a plate member 733, which may be of a conductive material or simply a carrier for the thermally conductive fluid conduit 735 disposed thereon or therein, which is to be supplied from a coolth delivery conduit (not shown) and which returns warmed fluid to coolth return conduit (not shown) via interface inlet and outlet ports 737, 739. The coolth delivery and return conduits (not shown) may gain access to the interface inlet and outlet ports 737, 739 via access aperture 743 provided in the top or side surfaces of the coolth delivery door 749. Another embodiment of a coolth delivery door 849 is illustrated in Figure 8 as a part of another refrigerator 847 in which the door 849 is hingedly mounted to the refrigerator body 841. As in Figure 7, the coolth delivery door 849 has a coolth delivery interface 819 having a plate member 833, which may be of a conductive material or simply a carrier for the thermally conductive fluid conduit 835 disposed thereon or therein. In this case, however, the thermally conductive fluid conduit 835 of the coolth delivery interface 833 is supplied by a coolth delivery conduit 817 and returns warmed fluid to coolth return conduit 821 via interface inlet and outlet ports 837,839, which coolth delivery conduit 817 and return conduit 821 are connected to a energy storage unit 807 (via a coolth absorption interface, not shown), containing the coolth storage medium (not shown), formed in the coolth delivery door 849. The insulated housing for the coolth storage medium in the energy storage unit 807 is provided by the coolth delivery door 849. The coolth delivery fluid may be driven from coolth absorption interface (not shown) in the energy storage unit 807 to the coolth delivery interface 819 through the coolth delivery conduit 817 by pump 825. The operation of the circulation pump 825 is powered by an electrical connection (not shown) and controlled by a controller (not shown) which may be in the coolth delivery door or external thereto. The or a controller may control an electrically-powered cooler (not shown) for the coolth storage medium in the energy storage unit 807, which electrically-powered cooler and controller therefore may be internal to or external to the coolth delivery door 849. Figure 9 illustrates a coolth common circulation system 951 according to another aspect of the invention, in which coolth may be circulated from a single (or multiple) cumulative energy storage unit 907 to multiple users of coolth (e.g. to multiple contained environments, such as refrigerators 947). In this illustrated embodiment, a cumulative energy storage unit 907 is located in the basement 953 of an office / accommodation block 955 having multiple office / accommodation units 957, each having a demand for coolth in a contained environment, whether that be for air conditioning in the office / accommodation units themselves (as contained environments) or for refrigeration in refrigerators 947 located within each office / accommodation unit 957. The coolth for each of the refrigerators 947 (or contained environments) is supplied by the cumulative energy storage unit 947 via a coolth delivery fluid through a circulation system 951 comprising a coolth delivery manifold 959 having coolth delivery spurs 961 extending therefrom to each refrigerator 947 and warmed coolth delivery fluid returned to the energy storage unit for re-cooling by a return manifold 963 fed by return spurs 965. The coolth delivery spurs 961 and return spurs 965 will typically be coupled with inlet and outlet ports of a coolth delivery interface such as that illustrated in Figures 6 and 7. The coolth delivery fluid will be circulated through the circuit 951 by pump 925 under the control of controller 927 which will also control the electrically-powered cooler 911 for storing coolth in the energy storage unit 907. The controller 927 will be configured to control the generation of coolth in the energy storage unit 907 via the electrically-powered cooler 911 according to actual and / or predicted availability of renewable energy or energy having a cost below a pre-defined threshold and predicted cumulative demand for coolth from the contained environments (refrigerators 947), which may be based upon the predictive demand for each refrigerator 947 which may rely upon an Al / machine learning module for learning the behaviour of users of each refrigerator 947 and correlating that behaviour with demand for coolth over time, in a manner discussed above. The supply of coolth to the individual refrigerators 947 may be also controlled by controller 927 or by local controllers (not shown) which allow the opening of a valve (not shown) to the respective coolth delivery spur 961. Optionally, payment mechanisms can be configured for supply of coolth according to pre-determined requirements and usage based upon the amount of coolth used and / or the access to coolth at peak times. Thereby, a system is described in which coolth is provided as a service to multiple users from a common bulk storage of coolth, enabling more effective access to renewable energy. In each of the examples described in Figures 6 to 9, the refrigerators may be primarily or solely dependent upon the supply of coolth from the energy storage unit (rather than as a secondary or auxiliary dependence). Throughout the description and claims of this specification, the words “comprise” and contain” and variations of them mean “including but not limited to”, and they are not intended to and do not exclude other components, integers, or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Features, integers, characteristics, or groups described in conjunction with a particular aspect, embodiment, or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. Further aspects and / or embodiments of the invention are described in the following clauses: Clause 1. An apparatus comprising: an apparatus controller; at least one energy storage unit, an energy storage unit comprising: a housing comprising an insulating layer; a coolth storage medium within the housing; an electrically powered cooler, configured to provide electrically powered cooling to cool the coolth storage medium, wherein the electrically powered cooling is variable under the control of the apparatus controller; at least one outlet port; and one or more refrigeration units in fluid communication with the at least one energy storage unit via at least one air conduit, each refrigeration unit comprising: a housing comprising an insulating layer; one or more storage chambers within the housing; and at least one inlet port; and at least one air moving device configured to transport cool air from the at least one energy storage unit to the one or more refrigeration units via the at least one air conduit. Clause 2. An apparatus according to clause 1, wherein each of the one or more refrigeration units is demountably retained or retainable on a top surface of at least one energy storage unit. Clause 3. An apparatus according to clause 1, wherein an energy storage unit and a refrigeration unit are coupled to form a single unit, typically with the energy storage unit underneath the refrigeration unit. Clause 4. An apparatus according to clause 2 or clause 3, wherein the outlet port of each of the one or more energy storage units is configured to connect to the inlet port of a respective one of the one or more refrigeration units while the refrigeration unit is demountably retained thereon. Clause 5. An apparatus according to any preceding clause, wherein the one or more refrigeration units comprise a plurality of refrigeration units in fluid communication with one energy storage unit such that the at least one air moving device can selectively transport cool air from the one energy storage unit to one or more of the said plurality of refrigeration units. Clause 6. An apparatus according to clause 5, wherein the plurality of refrigeration units comprise a plurality of separate refrigeration units within a shop. Clause 7. An apparatus according to any preceding clause wherein the insulating layer of the housing of the at least one energy storage unit has a greater thickness than the insulating layers of the housings of the one or more refrigeration units. Clause 8. An apparatus according to any preceding clause, wherein the operation of the at least one air moving device is variable under the control of the apparatus controller to vary the rate at which coolth is transferred from the at least one energy storage unit to at least one refrigeration unit. Clause 9. An apparatus according to any preceding clause, wherein the apparatus controller is configured to implement a temporary energy storage procedure in the at least one energy storage unit, wherein the temporary energy storage procedure comprises causing the electrically powered cooler of the at least one energy storage unit to cause cooling of the coolth store medium, thereby storing electrical energy in the form of coolth. Clause 10. An apparatus according to clause 9, wherein the apparatus controller is configured to implement the temporary energy storage procedure in response to an increased availability of renewable electricity or a decreased cost of electricity. Clause 11. An apparatus according to clause 9 or clause 10, wherein the apparatus controller is configured to implement the temporary energy storage in dependence on predicted future availability of renewable electricity or in dependence on predicted future cost of electricity. Clause 12. An apparatus according to any one preceding clause wherein the apparatus is configured to stop an energy storage procedure in response to a maximum storage condition being met by the at least one energy storage units. Clause 13. An apparatus according to clause 12, wherein the maximum storage condition is variable and a greater amount of coolth is stored in response to an increased availability of renewable electricity or a decreased cost of electricity, or a predicted increase in the availability of renewable electricity or a predicted decrease in cost of electricity, than would otherwise be the case. Clause 14. An apparatus according to any preceding clause, wherein at least one of the one or more refrigeration units comprises an electrically powered cooler configured to provide electrically powered cooling to cool the one or more storage chambers of the respective refrigeration unit, wherein the electrically powered cooling is variable under the control of the apparatus controller. Clause 15. An apparatus according to any preceding clause, wherein the coolth storage medium comprises a material which changes phase at a temperature within the operating temperature range of the at least one energy storage unit. Clause 16. An apparatus according to any preceding clause, wherein each of the one or more refrigeration units comprises a door. Claus 17. An apparatus according to any preceding clause, wherein one or more refrigeration units comprises a material which changes phase at a temperature within the operating temperature range of the refrigeration unit, to buffer temperature changes. Clause 18. An apparatus according to any preceding clause, wherein the air moving device comprises a fan, and wherein the air moving device further comprises a battery power supply for the fan. Clause 19. An apparatus according to any preceding clause, wherein the electrically powered cooler comprises an electrically powered compressor. Clause 20. A building comprising an apparatus according to any one preceding clause, the building comprising a plurality of rooms and an air conditioning manifold in gaseous communication with the plurality of rooms to regulate the temperature of the plurality of rooms, wherein the energy storage unit is controllably connected to the air conditioning manifold to thereby selectively provide cooled air to the plurality of rooms. Clause 21. An energy storage unit comprising: a housing comprising an insulating layer; a coolth storage medium within the housing; an electrically powered cooler, configured to provide electrically powered cooling to cool the coolth storage medium, wherein the electrically powered cooling is variable under the control of the apparatus controller; at least one outlet port; and configured to operate as the energy storage unit of any one of clauses 1 to 19. Clause 22. An apparatus comprising: a controller; an energy storage unit comprising: a coolth storage medium; and an electrically powered cooler configured to provide electrically powered cooling to cool the coolth storage medium, wherein the electrically powered cooling is variable under the control of the controller; wherein the controller is configured to use information based on meteorological data to determine whether a renewable energy availability condition has been satisfied, wherein the controller is configured to use information based on meteorological data to predict when the renewable energy availability condition will be satisfied, and wherein the controller is configured to cause the electrically powered cooler to provide electrically powered cooling of the coolth storage medium upon satisfaction or predicted satisfaction of the renewable energy availability condition, such that the electrically powered cooler is powered by renewable sources of electricity, thereby storing renewable energy in the form of coolth. Clause 23. An apparatus according to clause 22, wherein the meteorological data comprises wind speed data and the renewable energy is wind power. Clause 24. A method of operating the apparatus of any of clauses 1 to 23, the method comprising varying the cooling of the coolth storage medium and causing the at least one air moving device to transport cool air from the at least one energy storage unit to the one or more refrigeration units via the at least one air conduit. Clause 25. A method according to clause 24, wherein the apparatus comprises a plurality of refrigeration units in fluid communication with one energy storage unit such that the at least one air moving device can selectively transport cool air from the one energy storage unit to one or more of the said plurality of refrigeration units, and the method comprises selectively supply cool air from the energy storage unit, such as to supply different amounts of cool air to different ones of the plurality of refrigeration units. The invention has been described with reference to preferred embodiments. However, it will be appreciated that variations and modifications can be effected by a person of ordinary skill in the art without departing from the scope of the invention

Claims

1. A system for providing cooling to a contained environment, the system comprising:a controller;at least one energy storage unit, an energy storage unit comprising:an insulating housing;a coolth storage medium within the housing; andan electrically-powered cooler, which is configured to provide electrically-powered cooling to cool the coolth storage medium, wherein the electrically-powered cooling is variable under the control of the controller;at least one demand-initiating device for generating a demand factor associated with the demand for coolth in the contained environment; anda coolth delivery sub-system configured to deliver coolth from the energy storage unit to the contained environment in response to at least one demand factor from the at least one demand-initiating device, wherein the controller is configured to operate the electrically-powered cooler to increase the quantity of energy stored as coolth, according toi) predicted frequency, magnitude and / or duration of generated demand factors; and / orii) predicted availability of renewable energy-derived electricity and / or electricity having a cost below a defined threshold.

2. A system as claimed in claim 1, wherein the coolth storage medium is a phase change material.

3. A system as claimed in claim 1 or claim 2, wherein the coolth storage medium is ice / water.

4. A system as claimed in any one of claims 1 to 3, wherein the electrically-powered cooler comprises one or more of a compressor-type cooler and a thermoelectric cooler.

5. A system as claimed in claim 4, wherein the electrically-powered cooler is in direct contact with the energy storage unit or serves to cool a coolant fluid which is circulated through a pipe or conduit in thermal communication with the cool th storage medium.

6. A system as claimed in any one of the preceding claims, wherein the controller comprises or has access to an IA / ML module to assist the controller in operating the electrically-powered cooler according to predicted frequency, magnitude and / or duration of generated demand factors.

7. A system as claimed in any one of the preceding claims, wherein the one or more demand-initiating devices includes a manually actuated switch or button for generating a manual demand factor in the form of a demand signal.

8. A system as claimed in any one of the preceding claims, wherein the one or more demand-initiating devices include one or more sensors for detecting demand features and generating demand factors therefrom.

9. A system as claimed in claim 8, wherein the demand features include one or a combination of any two or more of occupancy level, nature of occupancy (e.g. thermal energy being emitted by occupant articles or beings and / or density of occupant articles or beings and / or size / volume of occupant articles or beings), opening of (e.g. a door of) the contained environment, temperature within the contained environment, and temperature outside the contained environment.

10. A system as claimed in any one of the preceding claims, wherein the coolth delivery sub-system comprises a direct coolth delivery arrangement and / or a direct coolth absorption configuration.

11. A system as claimed in claim 10, wherein the coolth delivery system comprises a coolth delivery fluid that is pumped from the energy storage unit tothe contained environment via a coolth delivery conduit and wherein the coolth delivery fluid is air or oxy gen-depleted air.

12. A system as claimed in any one of claims 1 to 9, wherein the coolth delivery sub-system comprises an indirect coolth delivery arrangement and an indirect coolth absorption configuration.

13. A system as claimed in claim 12, wherein the coolth delivery sub-system comprises the circulation of a coolth delivery fluid, through a coolth delivery conduit, a delivery interface, a return conduit and a storage interface.

14. A system as claimed in claim 13, wherein the delivery interface comprises a thermally conductive conduit or panel that is in contact with the contained environment.

15. A system as claimed in claim 14, wherein the delivery interface is provided as a component integral with a plate member, such as a glass plate for use as a refrigerator shelf.

16. A system as claimed in claim 14, wherein the delivery interface is integral with a door to the contained environment.

17. A system as claimed in any one of claims 12 to 16, wherein the coolth delivery fluid is water or an aqueous solution (e.g. containing alcohol or antifreeze, which may serve to lower the freezing point of the coolth delivery fluid).

18. A system as claimed in any one of claims 1 to 17, wherein the contained environment is a room or house and the system is for providing air conditioning to a living or working space.

19. A system as claimed in any one of claims 1 to 17, wherein the contained environment is a cool box of a refrigerator.

20. A spatial cooling system comprising a system for providing cooling to a contained environment as defined in any one of claims 1 to 19 and a contained environment provided with the said system.

21. A refrigerator door adapted for use as a coolth delivery interface for providing coolth to a refrigerator, the coolth delivery interface being configured for connection with a coolth delivery fluid supply conduit and a coolth delivery fluid return conduit.

22. A method of cooling a contained environment to a desired temperature or maintaining the temperature of a contained environment at a temperature below that of the surrounding environment, the method comprising operating the system of providing cooling to a contained environment as defined in any one of claims 1 to 19.23 A coolth circulation system for providing coolth to multiple contained environments from a common energy storage unit, the system comprising: at least one energy storage unit comprisingat least one insulated housing,a coolth storage medium in the at least one insulated housing and an electrically-powered cooler for cooling the coolth storage medium within the insulated housing;a coolth delivery circuit for delivering a coolth delivery fluid selectively to any one or more of a plurality of discrete contained environments via a coolth delivery interface associated with each of the plurality of discrete contained environments;a coolth return circuit for returning the coolth delivery fluid from the one or more of a plurality of discrete contained environments;a controller for controlling the selective delivery of coolth delivery fluid via the coolth delivery circuit to the any one or more of a plurality of discrete contained environments according to one or more pre-defined criteria; and, preferably, a controller for controlling the operation of the electrically-powered cooler according to:i) predicted cumulative frequency, magnitude and / or duration of generated demand factors from the plurality of contained environments; and / or ii) predicted availability of renewable energy-derived electricity and / or electricity having a cost below a defined threshold

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