Low carbon energy system

Abstract

An energy system (100) for supplying electricity to a load (108) and a method of using said system are provided, the system comprising renewable electricity generation capacity (102) comprising solar and wind generation capacity, a battery (110) with a maximum electricity storage capacity sufficient to meet the mean load for up to 1 hr, an electrolyser (112) configured for hydrogen gas production and capable of operating at from 0.3 to 0.8 times the maximum output of the renewable electricity generation capacity; and gas storage (114) configured to receive the hydrogen gas; wherein the renewable electricity generation capacity is in electrical communication with the electrolyser via the battery and wherein the system is configured to allow electrical communication to the load such that electrical output not consumed by the load is used to generate hydrogen gas.

Description

[0001] Low Carbon Energy System

[0002] Field of the Invention

[0003] The present invention relates to a low carbon energy system and method of providing energy to a load using such a system.

[0004] Background of the Invention

[0005] The energy system in the UK is based on three grids, mostly based on fossil fuels: a national grid for electricity (21% of total energy use); gas pipe grid now using natural gas (34% of total energy use); and petroleum product grid which ships liquid fuels in road -tankers (45% of energy use). Since these grids are currently dominated by fossil fuels, there is a difficulty in decarbonising these systems as required to limit global warming to 1.5 °C.

[0006] The current solution to decarbonising these energy systems is to generate energy from renewable sources. Renewable energy sources are sources that are replenished at a higher rate than they are consumed, for example, renewable energy sources include solar, wind, wave, geothermal, biomass and rainfall.

[0007] Bringing reliable and affordable decarbonised energy to communities, in particular remote communities, is a significant challenge due to the intermittent nature of energy generated from renewable sources and the cost of large-scale energy storage. The present inventor has identified a system suitable for a mid-sized community that provides a reliable and affordable supply of renewable energy to said community.

[0008] Summary of the Invention

[0009] The present invention provides in a first aspect an energy system for supplying electricity to a load having a mean load of from 1 to 50 MW, the system comprising: renewable electricity generation capacity with a maximum output of from 1.5 to 5 times the mean load, comprising solar and wind generation capacity; a battery with a maximum electricity storage capacity sufficient to meet the mean load for up to 1 hr; an electrolyser configured for hydrogen gas production and capable of operating at from 0.3 to 0.8 times the maximum output of the renewable electricity generation capacity; and gas storage configured to receive hydrogen gas from the electrolyser.

[0010] Wherein the renewable electricity generation capacity is in electrical communication with the electrolyser via the battery and wherein the system is configured to allow electrical communication to the load, such that, when connected to the load, any electrical output not consumed by the load is used by the electrolyser to generate hydrogen gas, which is then passed into the gas storage.

[0011] The present invention provides in a second aspect, a method of supplying energy to a load having a mean load of from 1 to 50 MW using an energy system, the method comprising: generating renewable electricity using renewable electricity generation capacity and providing this electricity to the load, wherein when the electricity generated by the renewable electricity generation capacity exceeds the load, the electricity in excess of the load is used to charge a battery and wherein electrical energy stored in the battery is used to generate hydrogen gas that is then stored, to dampen fluctuations in the electricity supply to the load from the renewable electricity generation capacity, or a combination thereof.

[0012] In some embodiments, the energy system of the method of the second aspect may be that of the first aspect.

[0013] Detailed Description of the Invention

[0014] The present invention provides an energy system for supplying electricity to a load having a mean load of from 1 to 50 MW, the system comprising: renewable electricity generation capacity with a maximum output of from

[0015] 1.5 to 5 times the mean load, comprising solar and wind generation capacity; a battery with a maximum electricity storage capacity sufficient to meet the mean load for up to 1 hr; an electrolyser configured for hydrogen gas production and capable of operating at from 0.3 to 0.8 times the maximum output of the renewable electricity generation capacity; and gas storage configured to receive hydrogen gas from the electrolyser. Wherein, the renewable electricity generation capacity is in electrical communication with the electrolyser via the battery and wherein the system is configured to allow electrical communication to the load, such that, when connected to the load, any electrical output not consumed by the load is used by the electrolyser to generate hydrogen gas, which is then passed into the gas storage.

[0016] The system of the invention provides renewable electricity to a load, such as community or industrial complex. Both the load and renewable electricity generated will vary overtime and will not always be equal. Therefore, excess renewable electricity generated by the renewable electricity generation capacity is used to power an electrolyser generating hydrogen gas which is passed into the gas storage. When the load is greater than the renewable electricity generated, the stored hydrogen gas may be used to generate electrical or thermal power to be supplied to the load, thereby bridging the gap in renewable electricity production. The battery in the system dampens short term fluctuations in the supply of renewable electricity to the electrolyser, allowing the electrolyser to function efficiently.

[0017] The system of the invention may be configured such that, when connected to the load, the renewable electricity generation capacity is in direct electrical communication with the load.

[0018] The renewable electricity generation capacity of the invention comprises wind and solar electricity generation capacity. Wind energy generation capacity may comprise or consist of wind turbines generating electricity from wind. Solar energy generation capacity may comprise or consist of solar panels generating electricity from solar radiation.

[0019] Wind and solar electricity generation capacity typically generates electricity 50% of the time across a year. A combination of 5 MW of wind electricity generation capacity and 5 MW of solar electricity generation capacity would therefore typically provide 5 MW of power over the course of a year. In the context of this invention, generation capacity is the maximum output of the component, for example a 5 MW of solar electricity generation capacity can produce at most 5 MW of electricity. By combining wind and solar electricity generation capacity, supply can be smoothed over the course of a year as solar electricity generation is generally more productive during the summer months and wind electricity generation is generally more productive during the winter.

[0020] To regularly meet the demands of the load and provide electricity to generate hydrogen gas via the electrolyser during periods of high electricity production to bridge periods of low electricity production that do not meet the demands of the load, the system of the invention requires renewable electricity generation capacity with a maximum output of at least 1.5 times the mean load. For example, if the mean load is 10 MW, the invention requires renewable electricity generation capacity of from 15 MW. Greater than five times the mean load increases the costs of the system beyond the cost that a mid-sized community can support and so is not economically viable. Therefore, the system of the invention requires renewable electricity generation capacity with a maximum output not greater than five times the mean load.

[0021] The system comprises renewable electricity generation capacity with a maximum output of from 1.5 to 5 times the mean load, such as from 1.5 to 4, or from 1.5 to 3 or from 2 to 4 times the mean load.

[0022] The renewable electricity generation capacity may further comprise hydroelectric generation capacity, biomass electricity generation capacity, or a combination thereof.

[0023] Alternatively, the renewable electricity generation capacity may consist of wind and solar electricity generation capacity. The balance of wind and solar power may be modified to provide the most reliable or most cost-efficient energy mix depending on the geography and climate of the location. The skilled person would readily understand how to arrive at the most reliable or most cost-efficient mix of wind and solar electricity generation. By way of example, wind electricity generation capacity may contribute from 25 to 75% of the renewable electricity generation capacity, such as from 30 to 70%, from 35 to 65% or from 40 to 60%. The remainder of the renewable electricity generation capacity may be provided by solar electricity generation capacity, for example the renewable electricity generation capacity may be 40 to 60% wind electricity generation capacity and 40 to 60% solar electricity generation capacity for a total of 100%, such as 50% wind electricity generation capacity and 50% solar electricity generation capacity. The electrolyser of the invention may be a polymer electrolyte membrane (PEM) device. Such devices provide pure hydrogen gas at storage pressures around 3.5 MPa (35 bar). Hydrogen gas at this pressure is suitable for storage in a stack of steel or composite cylinders and for piping into domestic or commercial buildings.

[0024] The electrolyser of the invention is capable of operating at from 0.3 to 0.8 times the maximum output of the renewable electricity generation capacity. To ensure that the system is economic the electrolyser needs to be of a size that it regularly operates at capacity. The electrolyser therefore operates at not greater than 0.8 times the maximum output of the renewable electricity generation capacity, such as not greater than 0.7 times, not greater than 0.6 times or not greater than 0.5 times the maximum output of the renewable electricity generation capacity, as during normal operation a portion of the electricity generated by the renewable electricity generation capacity will be consumed by the load, leaving less than 100% to power the electrolyser. To ensure that the electrolyser is able to produce sufficient hydrogen gas when excess electricity is produced to bridge gaps when insufficient electricity is produced the electrolyser needs to be capable of operating at at least 0.3 times the maximum output of the renewable electricity generation capacity, such as at least 0.4, at least 0.5 or at least 0.6 times the maximum output of the renewable electricity generation capacity. For example, if the maximum output of the renewable electricity generation capacity of 10 MW, the electrolyser will be capable of operating at from 3 to 8 MW.

[0025] Electrolysers also generate thermal energy as a by-product during normal operation. In typical systems the thermal energy generated may be lost. To prevent energy wastage and so make the system more efficient, the system of the present invention may further comprise a thermal transfer component configured to capture the thermal energy generated by the electrolyser and transport it to a location to be used or stored, for example to buildings requiring heating, to heat the battery as may be required in cold climates or to a thermal store such as a sand battery. The heat transfer component may be a simple pumped coolant component or it may further comprise heat exchange and compression components to heat buildings or heat stores to a temperature greater than that of the electrolyser. Where the system comprises a heat transfer component and thermal store as described above, the system will further comprise a second heat transfer system configured to deliver thermal energy to a second location, such as a building to be heated or a battery. In some embodiments of the invention, the electrolyser will consist of one or more electrolyser sub-units, each functioning as an individual electrolyser. This configuration enables hydrogen gas generation capacity to be added to the system through additional electrolyser sub-units in response to an increase in renewable electricity generation capacity. The capacity of the system can thus be expanded to meet an increase in the load.

[0026] Fluctuations in electricity supply to electrolysers shortens the lifespan of these devices and they are therefore poorly suited to run solely on electricity produced directly from renewable sources, which are inherently variable. To ensure that the system is affordable and able to operate in remote communities the lifespan of the system needs to be as long as possible. The system of the invention therefore comprises a battery configured to store electrical energy. The present inventor has identified that a battery positioned between the renewable electricity generation capacity and the electrolyser extends the lifespan of the electrolyser.

[0027] The purpose of the battery is to dampen short term fluctuations in the supply of renewable electricity to the electrolyser. Short term fluctuations are changes in the supply of electricity provided from the renewable electricity generation capacity over the course of an hour. Connection to an electricity grid, when available, can also be used to dampen short-term fluctuations in renewable electricity generation.

[0028] Long term fluctuations, for examples over more than one hour or one or more days, may be dampened using the stored hydrogen gas, for example the hydrogen gas may be used to power hydrogen boilers or hydrogen fuel cells. Hydrogen fuel cells can provide combined heat and power (CHP) in buildings and other applications.

[0029] The battery of the invention has a maximum electricity storage capacity sufficient to meet the mean load for up to 1 hr. In other words, the battery has a maximum energy storage in MWh of up to 1 times the mean load in MW. This provides energy storage on the scale required to ensure efficient operation of the electrolyser without increasing the cost of the system. For example, the battery may have a maximum energy storage in MWh of from 0.1 to 1 times the mean load in MW, such as from 0.2 to 1, from 0.3 to 1, from 0.4 to 1, from 0.1 to 0.9, from 0.1 to 0.8 or from 0.1 to 0.7 times the mean load in MW.

[0030] The battery of the invention may be a lithium-ion battery, or other battery type suitable for the purpose. The battery comprises one or more cells. The battery may comprise a single battery or may comprise two or more batteries arranged in sequence or in parallel.

[0031] The system of the invention may be configured such that, when connected to the load, the battery is in sequence between the renewable electricity generation capacity and the load. That is, when the system is connected to the load the renewable electricity generation capacity is in electrical communication with the load via the battery. This configuration also enables the dampening of electricity fluctuations in the electricity supplied to the load and improves the reliability of the electricity supply to the load further.

[0032] The system of the invention comprises a gas storage configured to receive hydrogen gas from the electrolyser. The gas storage may comprise one or more storage vessels, such as two or more or three or more. The one or more storage vessels may be a stack of steel or composite cylinders, a tube trailer or a combination thereof. Storing hydrogen gas produced by the electrolyser allows it to be held in reserve during periods of high renewable electricity production (i.e. greater than the requirements of the load) and used to supplement or replace renewable electricity production during periods of low production (i.e. when supply of renewable electricity production falls below the requirements of the load).

[0033] The gas storage has a capacity sufficient to cover the energy needs during periods of low electricity production by the renewable electricity generation capacity. The storage requirements will vary according to the location of the system, size of the output of the renewable electricity generation capacity, the size of the mean load, and degree to which the system provides hydrogen gas to the hydrogen economy. The skilled person can readily determine the size of gas storage required according to these variables. The gas storage may have a capacity of at least 0.5 tons, such as at least 1 ton, at least 2 tons, at least 3 tons or at least 4 tons. The gas storage may have a capacity of no greater than 10 tons, such as no greater than 8 tons, no greater than 6 tons, no greater than 5 tons or no greater than 4 tons. The gas storage may be a stack of steel or composite cylinders, or a tube trailer, or a combination thereof. The gas storage may be connected to a national gas grid, a local gas grid configured to supply the load, or a combination thereof.

[0034] The system of the invention may be configured to prepare the hydrogen gas generated for shipping and transport. To achieve this, the system of the invention may comprise one or more gas compression component configured to compress the hydrogen gas generated to a pressure of at least 50 MPa (500 bar) suitable for storage in a tube trailer. This tube trailer can the ship and dispense the gas. The gas compression component may be configured to compress the hydrogen gas to at least 70 MPa (700 bar) suitable for hydrogen powered vehicles and small storage tanks. A gas compression component may be positioned in the flow of hydrogen gas between the electrolyser and the gas storage. In addition, or alternatively, a gas compression component may be positioned downstream from the gas storage. In addition, or alternatively, a gas compression component may be positioned between different storage vessels of the gas storage.

[0035] The system of the invention may also be configured to supply hydrogen gas to a national gas grid, optionally when gas storage within the system reaches capacity.

[0036] The system of the invention may be configured to convert stored hydrogen gas into energy for the community. This allows the system to provide energy during periods when the renewable electricity generation capacity is not producing energy. The system may be configured to provide energy for heating by direct water heating in hydrogen boilers, or electrical energy or Combined Heat and Power (CHP) by being supplied to hydrogen generators, hydrogen(diesel) generators, or hydrogen fuel cells. The gas storage may be connected to a gas grid supplying the load. The system may further comprise one or more energy generation component, such as hydrogen boilers, or Combined Heat and Power (CHP) units such as hydrogen generators, hydrogen(diesel) generators or hydrogen fuel cells. The one or more energy generation components may be connected to the gas storage by a piped gas distribution system. Alternatively, the one or more energy generation components are provided with hydrogen gas from the gas storage by a gas cylinder distribution network. The system of the invention allows remote communities, not connected to a national electricity grid, to access reliable and affordable renewable energy. Therefore, the system of the invention, the load or both, may have no connection to a national electricity grid. However, in another example the system of the invention may be configured to allow an electrical connection to a national grid, which facilitates the provision of electricity generated in excess of the requirements of the electrolyser and the load to a national electricity grid. An electrical connection to a national grid may also allow the system to balance large fluctuations in the renewable electricity generation.

[0037] The system of the invention is suitable for supplying a load having a mean load of from 1 and 50 MW. A system suitable for supplying a mean load outside of this range is uneconomic. The system of the invention may be suitable for supplying a mean load of from 1 and 20 MW, such as from 1 to 15 MW, from 1 to 10 MW, from 2 to 20 MW or from 5 to 20 MW. In some embodiments, the load may be a community of houses or businesses or a combination thereof, which may take electrical energy from the system generated by the renewable electricity generation capacity and from hydrogen gas stored in the gas storage component, for example, electricity generated from hydrogen gas by a CHP unit. Alternatively, the load may take electrical energy generated by the renewable electricity generation capacity of the system and heat energy generated by the burning of hydrogen gas stored in the gas storage of the system. CHP units generate heat and electricity, therefore in an alternative the load may take electrical energy generated by the renewable electricity generation capacity of the system and heat and electrical energy generated using hydrogen gas generated by the system.

[0038] The present invention further provides a method of supplying energy to a load having a mean load of from 1 to 50 MW using an energy system, the method comprising: generating renewable electricity using renewable electricity generation capacity and providing this electricity to the load, wherein when the electricity generated by the renewable electricity generation capacity exceeds the load, the electricity in excess of the load is used to charge a battery and wherein electrical energy stored in the battery is used to generate hydrogen gas that is then stored, to dampen fluctuations in the electricity supply to the load from the renewable electricity generation capacity, or a combination thereof. The method may further comprise the step wherein when the electricity generated by the renewable electricity generation capacity is less than the load, electrical energy stored in the battery is supplied to the load and / or stored hydrogen gas is used to generate electrical or thermal energy which is supplied to the load. For example, some or all the hydrogen gas generated by the electrolyser may be used to generate heat and / or electrical energy from the hydrogen gas, such as hydrogen boilers, hydrogen (diesel) generators, hydrogen generators, or hydrogen fuel cells.

[0039] The energy system of the method of the invention aspect may be the energy system of the invention.

[0040] The method may further comprise the step wherein some or all of the hydrogen gas generated may be passed into the hydrogen economy, optionally by way of a national gas network or gas refuelling station. This option may be preferable when gas storage capacity is full and the renewable electricity generation exceeds the requirements of the load, such that excess hydrogen gas is generated.

[0041] A gas refuelling station or tube trailer with dispenser is used to provide hydrogen gas to hydrogen powered vehicles. A dispenser in this context is any component configured to allow hydrogen gas transfer from the tube trailer to the fuel tank of a hydrogen powered vehicle.

[0042] Summary of the Figures

[0043] Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0044] Figure 1 is a schematic of a system according to the invention.

[0045] Figure 2 is a schematic of a system according to the invention wherein the system further comprises the additional components of power generation and a refuelling station, wherein the gas storage is configured to provide these additional components with hydrogen gas. Figure 3 is a is a schematic of a system according to the invention, wherein the system further comprises a gas distribution network, hydrogen boilers and a refuelling station.

[0046] In the figures, like or corresponding reference numerals are used for like or corresponding features.

[0047] Detailed Description of the Figures

[0048] The invention will now be further described through reference to the figures.

[0049] Referring firstly to Figure 1 of the accompanying drawings, the energy system (100) comprises renewable electrical electricity generation capacity (102) comprising one or more wind turbine (104) providing wind generation capacity and one or more solar panel (106) providing solar generation capacity. The renewable electricity generation capacity (102) provides electrical energy to a load (108). Excess electricity generated by the renewable electricity generation capacity (102) but not consumed by the load is provided via the battery (110) to the electrolyser (112) where it is consumed generating hydrogen gas. The hydrogen gas generated is passed from the electrolyser (112) to the gas storage (114).

[0050] Referring to Figures 2 and 3 of the accompanying drawings, the energy system (200, 300) comprises the features of Figure 1. The renewable electricity generation capacity (202, 302) provides electrical energy to a load (208, 308). Excess electricity generated by the renewable electricity generation capacity (202, 302) but not consumed by the load is provided via the battery (210, 310) to the electrolyser (212, 312) where it is consumed generating hydrogen gas. The hydrogen gas generated is passed from the electrolyser (212, 312) to the gas storage (214, 314). When the gas storage may pass excess hydrogen gas generated by the electrolyser to a refuelling station (218, 318) for hydrogen powered vehicles. Between the gas storage and the refuelling station is a gas compression component (not shown) that compresses the hydrogen gas to a pressure suitable for hydrogen vehicles.

[0051] In Figure 2, the system further comprises power generation (216) such as one or more CHP unit, for example one or more hydrogen generators, one or more hydrogen(diesel) generators, or one or more hydrogen fuel cells or combinations thereof. When the electricity generated by the renewable electricity generation capacity (202) is insufficient to meet the load (208), hydrogen gas stored in the gas storage (214) is transferred to the power generation (216), optionally via a pipe network or gas cylinder network (not shown). The power generation uses the hydrogen gas to generate electricity which is then supplied to the load (208), thereby supplementing the renewable electricity generation capacity (202).

[0052] In Figure 3, the system further comprises a gas distribution network (316) configured to carry hydrogen gas from the gas storage (314) to hydrogen boilers or CHP units distributed throughout the community. When the electricity generated by the renewable electricity generation capacity (302) is insufficient to meet the load (308), hydrogen gas stored in the gas storage (314) is transferred to the hydrogen boilers (316) via the gas distribution network (320) to provide heating to the load, which may be a community of domestic dwellings, commercial premises or a combination thereof, to supplement the renewable electricity generation capacity (302).

[0053] Example

[0054] An energy system for a community of 6000 people containing many homes, buildings for work and small businesses and hundreds of vehicles.

[0055] The size of the rural site is large, almost 1 square mile in area on a hill, such that a 2MW wind turbine could be installed plus 4.4MW of solar panels on a grassy area, to provide renewable energy for electrical power, space heating and transport plus export to industries. The average electrical, power bill was originally for 3.5MW mean power, so the renewable power / demand ratio was 6.4 / 3.5 which was near the theoretical 2 / 1 ratio for availability. Both wind and solar worked well, with more wind in winter and more solar in summer, but the performance over 12 months and longer periods is not yet certain. A IMWh battery is used to bridge the fluctuations so the electrolyser had a steady voltage. A 3MW PEM electrolyser was installed with a Iton hydrogen gas storage steel cylinder stack used for holding hydrogen gas at 35bar. A tube trailer was filled with Iton compressed hydrogen gas at 500 bar for shipping or dispensing to vehicles. The ratio of stored energy to daily demand was almost one, capable of bridging a full day with low wind / solar. The cost of equipment and installation was £12M. The saving on utility bills of £3M / a gave a payback time near 4 years. A grid connection was agreed and was used to balance large fluctuations in the wind / solar generation, but high flow of renewable energy to the grid was curtailed.

[0056] This design of a local distributed renewable energy system fitted the low carbon definition and was almost independent of the large utility companies, thus providing renewable energy for vehicles, buildings and industries at less than half price of a grid connection.

Claims

CLAIMS1. An energy system for supplying electricity to a load having a mean load of from 1 to 50 MW, the system comprising: renewable electricity generation capacity with a maximum output of from1.5 to 5 times the mean load, comprising solar and wind generation capacity; a battery with a maximum electricity storage capacity sufficient to meet the mean load for up to 1 hr; an electrolyser configured for hydrogen gas production and capable of operating at from 0.3 to 0.8 times the maximum output of the renewable electricity generation capacity; and gas storage configured to receive hydrogen gas from the electrolyser; wherein the renewable electricity generation capacity is in electrical communication with the electrolyser via the battery and wherein the system is configured to allow electrical communication to the load such that any electrical output not consumed by the load is used by the electrolyser to generate hydrogen gas that is then passed into the gas storage.

2. The energy system of claim 1, wherein wind generation capacity contributes from 25 to 75% of the renewable electricity generation capacity.

3. The energy system of any one of claims 1 or 2, wherein the renewable electricity generation capacity consists of wind generation capacity and solar generation capacity.

4. The energy system of any one of claims 1 or 2, wherein the renewable electricity generation capacity further comprises hydroelectric generation capacity, biomass electricity generation capacity, or a combination thereof.

5. The energy system of any preceding claim, wherein the electrolyser of the invention is a polymer electrolyte membrane (PEM) device.

6. The energy system of any preceding claim, wherein the system further comprises a thermal transfer component in thermal communication with the electrolyser, configured to transfer thermal energy generated by the electrolyser to a location where it is used or stored.

7. The energy system of claim 6, wherein the system further comprises a thermal store, and wherein the thermal transfer component is configured to transfer thermal energy from the electrolyser to the thermal store.

8. The energy system of any preceding claim, wherein when the system is connected to the load the renewable electricity generation capacity is in electrical communication with the load via the battery.

9. The energy system of any preceding claim, wherein the gas storage comprises one or more storage vessels, optionally selected from a stack of steel or composite cylinders, a tube trailer, or combinations thereof.

10. The energy system of any preceding claim, wherein the gas storage has a capacity of at least 0.5 tons.

11. The energy system of any preceding claim, wherein may comprise one or more gas compression component and configured to compress the hydrogen gas generated to a pressure of at least 50 MPa.

12. The energy system of claim 11, wherein a gas compression component is positioned in the flow of hydrogen gas between the electrolyser and the gas storage, and / or a gas compression component is positioned downstream from the gas storage and / or a gas compression component is positioned between different storage vessels of the gas storage.

13. The energy system of any preceding claim, wherein the system further comprises one or more energy generation component, selected from hydrogen boilers, Combined Heat and Power (CHP) units, or combinations thereof, and wherein the one or more energy generation component is configured to be supplied with hydrogen gas from the gas storage and to supply energy generated to the load.

14. The energy system of any preceding claim, wherein the system has no connection to a national electricity grid.

15. A method of supplying energy to a load having a mean load of from 1 to 50 MW using an energy system, the method comprising:Generating renewable electricity using renewable electricity generation capacity and providing this electricity to the load, wherein when the electricity generated by the renewable electricity generation capacity exceeds the load, the electricity in excess of the load is used to charge a battery and wherein electrical energy stored in the battery is used to generate hydrogen gas that is then stored, to dampen fluctuations in the electricity supply to the load from the renewable electricity generation capacity, or a combination thereof.

16. The method of claim 15, wherein the energy system is the system of any one of claims 1 to 14.

17. The method of claim 15 or claim 16, wherein when the electricity generated by the renewable electricity generation capacity is less than the load, electrical energy stored in the battery is supplied to the load and / or stored hydrogen gas is used to generate electrical or thermal energy which is supplied to the load.

18. The method of any one of claims 15 to 17, wherein the method further comprises wherein some or all of the hydrogen gas generated by the electrolyser may be passed into the hydrogen economy, optionally by way of a national gas network, gas refuelling station or combination thereof.

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