Water heater capable of responding to power grid condition

Abstract

An object of the present invention is to provide an electric water heater having a vertically arranged water reservoir, an upper resistive heating element, and a bottom resistive heating element, and possibly having a lower heating element composed of a condenser of a heat pump. To-be-heated water enters the bottom and is taken out from the upper part. The water heater is configured to operate in different heating modes selectable by a user, where all modes ensure that a set temperature is met, but differ in control logic and consumption levels, and also capable of flexible consumption according to the condition of the power grid.

Description

Technical Field

[0001] The following describes a storage-type electric water heater for domestic or technical water heating in rooms.

[0002] A method for managing an electric storage water heater is also described. Background Art

[0003] The advantage of storage water heaters over instantaneous water heaters is that they require less electricity. However, storage water heaters also have some disadvantages. For example, storage water heaters experience continuous heat loss, which increases as the average temperature of the water contained in the storage tank increases.

[0004] Traditionally, such water heaters comprise a heating element of the electrical resistance type (hereinafter referred to as "resistor"). In addition to or as an alternative to the electrical resistance, storage water heaters are also known which use a heat pump as heating means.

[0005] The need to reduce electricity consumption has led to the development of "smart" water heaters equipped with algorithms that take into account historical events when adjusting the temperature of the water reservoir. Thus, when the probability of a user needing hot water is low, the water reservoir is kept at a lower average temperature, and when the probability of hot water is high, the temperature of the water reservoir is kept at a higher average temperature.

[0006] As energy sources gradually transition from fossil fuels to renewable energy, the supply of electricity on the grid depends on the availability of wind or photovoltaic energy (which are intermittent and uncontrollable by their nature). In addition, the power grid (referred to as the "grid") faces high variability in electricity demand throughout the day (e.g., different peaks in electricity consumption throughout the day).

[0007] The grid therefore finds itself in a situation where it must balance the supply of electrical energy with the demand and, contrary to the past, the demand must at least partially adapt to the supply. There is now a need for household appliances to be able to adapt their power consumption requirements (ie supply) to the conditions of the grid. Storage water heaters are known in which the algorithm for managing the heating element takes into account the imbalance of the grid.

[0008] EP3662210B1 describes a storage electric water heater in which the heating is controlled by an electronic regulator that takes into account the user's habits. During periods of time when the expectation for hot water extraction is low, the water heater maintains a constant low temperature. The learning of the water extraction pattern (called the "water withdrawal" pattern) is based on an estimate of the water withdrawal by analyzing the temperature changes in the water tank. This method basically links the operation of the heating element to the expected water withdrawal pattern, which achieves a significant reduction in electrical energy consumption in normal operation, but does not teach how to respond to signals from the power grid in an optimized way (for example, how to respond to grid imbalances and thus ultimately adapt to conditions of insufficient or excessive power).

[0009] Document US11300325B2 describes a storage water heater with resistors in the upper and bottom regions of the water storage. The management of the resistors is assigned to an electronic regulator that takes into account the power shortage or power surplus conditions of the power grid. Temperature hysteresis is applied to both the top and bottom heating elements. In balanced conditions of the power grid, the water heater does not adopt any strategy to rationalize the power consumption. In power shortage conditions (power supply exceeds the available amount and the power supply is unbalanced), the power consumption of the bottom resistor is reduced according to a heuristic algorithm that takes into account the historical water withdrawal. This reduction is achieved by reducing the activation threshold and the deactivation threshold. The accompanying figure shows the corresponding reduction in the amount of hysteresis generated. In power surplus conditions (generation imbalance), the water heater increases the power consumption by increasing the temperature threshold for activation of the resistor, while keeping the deactivation threshold unchanged, thereby reducing the amount of hysteresis. The increase in the activation temperature threshold does not take into account the actual needs of the user, and therefore does not maximize the stored and future available power, and the increase in power consumption partially leads to a waste of power.

[0010] An increase in electrical energy consumption needs to be converted into electrical energy storage, thereby allowing for a subsequent reduction in electrical energy.

[0011] Document US20130200168A1 describes a water heater with an upper resistor and a bottom resistor, which can operate in a normal mode and an energy-saving mode; in the energy-saving mode, the constant temperature is lowered according to the user's habits. The water heater can respond to insufficient or excessive power conditions of the power grid by activating or deactivating the heating element, perhaps through an external controller associated with it.

[0012] Document WO2019060 describes a water heater with an upper resistor and a bottom resistor, which is capable of receiving a signal from the power grid indicating a power shortage or surplus condition, and responding to the power surplus signal by entering a high power consumption operating mode and responding to the power shortage signal by switching to a low power consumption operating mode. The document does not teach user-selectable modes.

[0013] There is a need to regulate water heaters to reduce power consumption under normal conditions and to have an additional level of flexibility to respond to grid imbalance conditions without unduly impairing comfort. Comfort refers to a level of performance that guarantees that water at a set temperature is available to the user at all times when there is demand. There is no known water heater that meets the need to optimize power consumption under normal conditions and can be further configured to flexibly consume power in response to grid conditions. Summary of the invention

[0014] These and other objects are achieved by a method and an apparatus according to the method main claim and an apparatus (or system) according to the apparatus main claim. These and other objects will become clear from the following.

[0015] Other objects can also be achieved by means of the additional features of the dependent claims.

[0016] The following describes a storage electric water heater comprising a vertically arranged water tank or water reservoir, which comprises an upper region from which hot water is drawn and a bottom region into which water to be heated is introduced. The bottom region and the upper region are heated by respective heating elements and respective temperature sensors. In short, this configuration will be referred to as "dual zone" hereinafter.

[0017] A method for managing the operation of a "dual zone" type electric storage water heater is also described. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] - Figure 1.a , Figure 1.b , Figure 1.c and Figure 1.d Various views showing one possible embodiment of a water heater having an electrical resistance; - Figure 2.a , Figure 2.b and Figure 2.c A second possible embodiment of a water heater comprising an electrical resistance and a heat pump is shown; - Figure 3.a and Figure 3.b A table showing the correspondence between hourly rates and specific grid conditions; - Figure 4 A table showing the values ​​of the variables in different possible operating modes. DETAILED DESCRIPTION

[0019] Further features of the invention will be better highlighted by the following description of possible embodiments, in accordance with the claims; and these features are illustrated by non-limiting examples only, with the aid of the accompanying drawings. It should be noted that the invention is not limited to the structural details, examples and contents shown in the accompanying drawings; other embodiments are possible without departing from the scope of the claims. The terms used in this specification should not be interpreted as limiting. The terms "receive", "read", "detect" and "sensing" are used in a broad sense to mean receiving information, including information contained in a signal from the outside, information retrieved from a memory, or information received as input from a user interface. Similarly, "communication" or "connection" is not limited to communication via a physical link or line.

[0020] In the drawings, reference numeral 1 denotes a water heater comprising a vertically arranged water reservoir 10 having an upper portion 11 and a bottom portion 12 .

[0021] The upper part 11 of the water reservoir 10 comprises at least one first heating element 41, and the bottom part 12 of the water reservoir 10 comprises at least one second heating element 51, 61, also referred to as heating element (or simply element) hereinafter. The at least one upper element 41 may comprise a resistor, and the at least one bottom element 51, 61 may be a resistor 51 and / or a condenser 61 of a heat pump 6.

[0022] Located near each element 41, 51, 61 is a first or upper temperature sensor 42 that senses a higher temperature (referred to as "Tdome" or "top temperature") and a second or bottom temperature sensor 52 that senses a bottom temperature "Tbottom". The temperature sensors 42, 52 may be conventional temperature sensors (e.g., thermistors).

[0023] The water heater 1 comprising only the resistors 41 , 51 as heating elements will be referred to hereinafter as an electric water heater or electric model to distinguish it from a “hybrid” model also comprising a condenser 61 of a heat pump 6 .

[0024] The reservoir 10 is configured to allow cold water to enter near the bottom 12 through the first opening 2, and to allow hot water directed to the user to flow out through the second opening 3 near the top of the reservoir 10. In this way, under static conditions, the stratification of temperature helps the water flowing out of the reservoir 10 to be at the highest temperature.

[0025] The water heater 1 further comprises a regulator 5 for regulating the operation of the heating elements 41 , 51 , 61 .

[0026] The regulator 5 comprises memory means and is adapted to receive temperature readings obtained by the temperature sensors 42 , 52 and a temperature “Tset” which can be set by a user via a user interface 7 .

[0027] The regulator 5 is configured to calculate a control temperature for each heating element 41, 51, 61. The control temperature may be equal to the temperature detected by the temperature sensor 42, 52, or may be equal to a weighted average thereof. A plurality of heating elements 41, 51, 61 may share the same control temperature.

[0028] The regulator 5 may be an electronic control unit, comprising: - Memory with program instructions and parameters; - means for executing instructions and calculations; - Device for controlling heating elements and receiving signals from the outside.

[0029] The regulator 5 is configured to implement a set temperature Tset, which can be set via the user interface 7 .

[0030] The user interface 7 may be integrated in the water heater and include manual input means (such as buttons or knobs) and / or an external device and include means for sending input data to the regulator 5 configured to receive the input data. Figure 1.a , Figure 1.b , Figure 2.a and Figure 2.b As shown, when integrated in the water heater 1 , the user interface 7 may be assembled with the regulator 5 in a single component.

[0031] The upper part 11 of the water reservoir is heated directly by at least one upper heating element 41 and indirectly by at least one bottom heating element 51, 61 through convection effect. At least one upper heating element 41 has an upper temperature Tdome as a control temperature or has an upper temperature Tdome as the main component in a weighted average of the temperatures sensed by the temperature sensors 42, 52. For at least one bottom heating element 51, 61, the control temperature is the bottom temperature Tbottom or alternatively an average temperature "Tavg" obtained as an average between the top temperature Tdome and the bottom temperature Tbottom. Preferably, the average is a weighted average; even more preferably, the weight "Wdome" of the top temperature is less than the weight "Wbottom" of the bottom temperature Tbottom.

[0032] According to a preferred embodiment, the weight Wdome of the top temperature is comprised between 0.25 and 0.40, for example 0.3. At least one of the weights Wdome, Wbottom is a parameter stored in the memory of the regulator 5, while the other weight can be calculated accordingly or can also be stored.

[0033] A constant temperature “Ttarget” is set for each heating element 41 , 51 , 61 .

[0034] In a possible embodiment, the regulator 5 sets a common constant temperature Ttarget at least for the resistors 41, 51. The constant temperature Ttarget of each heating element 41, 51, 61 is included in the interval between a minimum temperature "Tmin" and a maximum temperature "Tmax" (Tmin≤Ttarget≤Tmax).

[0035] The maximum temperature Tmax is a factory parameter which can be modified on site and can vary, for example, between 55° C. and 85° C. Preferably, if a thermostatic mixing valve is present, this maximum temperature reaches the highest value.

[0036] The minimum temperature Tmin is considered to be an acceptable temperature to ensure comfort for domestic use; it may be comprised within a range between 37° C. and 42° C., for example about 40° C. By achieving thermostatting at a temperature above the minimum temperature Tmin, the drawn water can be mixed with cold water, which brings the advantage of increasing the volume of water delivered beyond the volume of the water reservoir.

[0037] The heating elements 41, 51, 61 are configured to be activated when the corresponding control temperature drops below the thermostatic temperature Ttarget minus the hysteresis value, and to be deactivated at the thermostatic temperature Ttarget. At least one upper element 41 has an upper hysteresis ThystDome (so the switch-on temperature is equal to Ttarget-ThystDome), and at least one bottom heating element 51, 61 has a bottom hysteresis Thyst (so the switch-on temperature is equal to Ttarget-Thyst). In general, each heating element may have a different hysteresis. Therefore, the midpoint between the activation temperature and the deactivation temperature is: For the upper heating element 41, it is Ttarget - ThystDome / 2; For the bottom heating elements 51 , 61 it is Ttarget−Thyst / 2.

[0038] By varying all temperature values ​​of the hysteresis amplitude, the present description can also be applied to the following possible implementation: the heating element is activated at a constant temperature Ttarget and is deactivated at temperatures Ttarget+Thyst, Ttarget+ThystDome, provided that the temperature rise is equal to the hysteresis Thyst, ThystDome. Therefore, in this case, the intermediate value between the activation temperature and the deactivation temperature is: For the upper heating element 41, it is Ttarget+ThystDome / 2; For the bottom heating elements 51 , 61 it is Ttarget+Thyst / 2.

[0039] exist Figure 2.a and Figure 2.b In the schematically shown embodiment, the at least one bottom heating element 51 , 61 comprises a bottom resistor 51 and a condenser 61 of a heat pump 6 .

[0040] In the example shown, the condenser 61 includes two sets of windings 611 , 612 located above and below the bottom resistor 51 , respectively.

[0041] Compared to resistor 51 , heat pump 6 has a higher energy efficiency, but may only heat up to a maximum heat pump temperature threshold Thp, here called heat pump threshold Thp for simplicity; a typical value of the heat pump threshold Thp of the pump is about 55° C. Above this heat pump threshold Thp, the heating function can be performed by resistors 41 , 51 .

[0042] 2 , the bottom resistor 51 can work in relay mode with the condenser 61 of the heat pump 6. In relay operation below the heat pump threshold Thp, the bottom element used is the condenser 61, and in relay operation above the threshold Thp, the bottom element used is the resistor 51.

[0043] The relay operation between the exchanger 61 of the heat pump 6 and the bottom resistor 51 allows to reduce the instantaneous power consumption and the electric energy consumption, since the heat pump 6 has a higher energy efficiency compared to the resistor 51 .

[0044] When the heat pump 6 and the bottom resistor 51 work in a relay mode, it is preferred that the control temperature of both is the average temperature Tavg, so that the water heater 1 works more efficiently. According to some embodiments of the water heater model 1 (including the condenser 61 as the only or additional bottom heating element), for all the bottom heating elements 51, 61, the control temperature is the average temperature Tavg.

[0045] In a dedicated electrical model, for the bottom resistor 51 , the control temperature is preferably the bottom temperature Tbottom measured by the bottom sensor 52 .

[0046] In preferred embodiments, the upper resistor 41 and the bottom resistor 51 are never activated together; even more preferably, the upper resistor 41 takes precedence over the bottom resistor 51. In other words, in these embodiments, the water contained in the upper part 11 of the water reservoir 10 (the first batch of water to be supplied) is always heated with priority.

[0047] In order to meet the different requirements of reducing energy consumption and ensuring sufficiently hot water, the water heater 1 has at least two heating modes, which can be selected according to the needs of the user.

[0048] The heating modes (hereinafter also referred to as "modes" for simplicity) allow the water to be at a set temperature Tset, but they differ in terms of control logic and consumption of the heating elements 41 , 51 , 61. The heating mode can preferably be selected using a user interface 7 .

[0049] In a first heating mode, called "Manual" or "Comfort", the water heater 1 sets the thermostatic temperature Ttarget equal to the set temperature Tset for all resistive heating elements 41, 51 and any heat pump 6, provided that the user temperature Tset is not higher than the heat pump threshold Thp. The user temperature Tset varies between a minimum temperature Tmin and a maximum temperature Tmax. In the first heating mode Comfort: - The upper resistor 41 and the bottom resistor 51 are never enabled together, - The upper resistor 41 takes precedence over the bottom resistor 51, If the condenser 61 is present as the bottom element, the bottom resistor 51 works in relay mode with the heat pump 6 .

[0050] According to a possible embodiment, the heating mode also includes a second heating mode, which is an optimization mode called "I-memory". The second mode I-memory is different from the first mode Comfort for a constant temperature Ttarget (which is equal to the optimized temperature Tmem that varies with time and is related to a saved water intake mode (the water intake mode includes data on the amount and temperature of water taken over a period of time)). The optimized temperature Tmem can vary from a minimum temperature Tmin to a maximum temperature Tmax. Methods for calculating the optimized temperature are known; for example, a method is described in EP2366081B1 (the content of which forms an integral part of this specification).

[0051] In FIG. 2 , the water heater 1 comprises at least one heating element 41 , 51 of the resistive type and a heating element consisting of a condenser 61 of a heat pump 6 , suitable for heating to a maximum temperature heat pump threshold Thp.

[0052] In particular, in the embodiments described herein comprising a heat pump 6, the water heater 1 may further comprise a third heating mode, a sustainable mode called "Green", and / or a fourth heating mode, a fast mode called "Fast".

[0053] The third heating mode Green prioritizes reducing power consumption and uses only the heat pump 6 , while the resistance-type elements 41 , 51 are always deactivated. In the third mode Green, the constant temperature Ttarget is equal to the minimum value between the user temperature Tset and the threshold Thp of the heat pump 6 .

[0054] The fourth mode Fast gives priority to fast heating, and is different from the first mode Comfort in that the bottom resistor 51 and the heat pump 6 are not enabled in a relay mode but are enabled simultaneously, with the only additional restriction being that the upper resistor 41 is turned off and remains turned off, while the bottom resistor 51 is turned on. In the fourth mode Fast, the heat pump 6 is preferably controlled at an average temperature Tavg, while the bottom resistor 51 is preferably controlled at a bottom temperature Tbottom.

[0055] In the third mode Green and the fourth mode Fast, the constant temperature Ttarget is equal to the user set temperature Tset. A fifth mode called "I-memory green" can be implemented, which is equivalent to the third mode Green, in which the constant temperature Ttarget is equal to the minimum value between the optimized temperature Tmem and the heat pump temperature threshold Thp. Similarly, a sixth mode called "I-memory fast" can be implemented, which is equivalent to the fourth mode Fast, in which the constant temperature Ttarget is equal to the optimized temperature Tmem. This allows the advantages of the second mode I-memory to be combined with the third mode Green or the fourth mode Fast. Figure 4 The constant temperature Ttarget for each heating mode is shown in table form.

[0056] As is clear from the above description, each heating mode is configured to reach one of a user set temperature Tset, a temperature threshold Thp of a heating element (condenser 61 of heat pump 6), or an optimized temperature Tmem.

[0057] According to some possible variants, at least two hysteresis values ​​are defined: an upper hysteresis "ThystDome" for the upper element 41 and a bottom hysteresis "Thyst" for at least one bottom element 51, 61. It has been observed that adopting different hysteresis values ​​for the upper heating element 41 and the bottom heating element 51, 61 can further reduce the consumption or, for the same consumption, improve the comfort. In the following, the top hysteresis ThystDome denotes the hysteresis of one or more upper elements, while the bottom hysteresis Thyst denotes the hysteresis of one or more bottom elements 51.

[0058] In particular, in an embodiment of the water heater 1 having only resistors 41, 51, it is advantageous to have a higher value of the bottom hysteresis Thyst (for example, comprised in the range between 2°C and 21°C, preferably in the range between 12°C and 18°C, in particular 15°C) and a smaller value of the top hysteresis ThystDome (for example, in the range between 1°C and 20°C, preferably in the range between 3°C and 9°C, in particular 5°C).

[0059] In contrast, in an embodiment in which the water heater 1 comprises the condenser 61 of the heat pump 6 as the bottom heating element, the situation is reversed and it is more convenient to have a smaller value of the bottom hysteresis Thyst (e.g. in the interval between 1°C and 20°C, preferably in the interval between 3°C and 9°C, in particular 5°C) and a higher value of the top hysteresis ThystDome (e.g. in the interval between 2°C and 21°C, preferably in the interval between 9°C and 18°C, in particular 12°C).

[0060] This is because, in embodiments where water heating is achieved solely with the aid of electrical resistances, it is preferable to avoid activation of the bottom resistor 51 due to small momentary temperature fluctuations, which are caused by a small water withdrawal and the subsequent water turbulence leading to the entry of cold water. A higher value of the hysteresis Thyst at the bottom resistor 51 makes it more stable and less sensitive to small turbulences. To compensate for the lower sensitivity, it is very useful to set the upper hysteresis ThystDome to a smaller value, so that the upper resistor 41 is very sensitive even to small turbulences, so that it can be activated quickly to ensure the correct temperature at the outlet 3 of the water heater 1.

[0061] In the embodiment also including the condenser 61 as the bottom heating element, it is preferred to maximize the use of the heat pump 6, thus limiting the use of the resistors 41, 51. Therefore, here, even for small water temperature fluctuations, it is recommended to activate the heat pump 6 by adopting a bottom hysteresis Thyst with a value smaller than the upper hysteresis ThystDome.

[0062] Optionally, in the heat pump model, the electrical model hysteresis is used when the average temperature Tavg or the constant temperature Ttarget is greater than the heat pump threshold Thp. Under these conditions, the heat pump 6 cannot contribute and the water heater 1 can be controlled as in the electrical model.

[0063] According to a possible embodiment, the water heater 1 is powered by electricity from the power grid and is configured to operate in at least two heating modes selected between a first mode "Comfort", a second mode "I-memory", a third mode "Green", a fourth mode "Fast", a fifth mode "I-memory green" or a sixth mode "I-memory fast" and receive a heating mode selection from a user interface. The regulator 5 is also configured to deactivate the heating elements 41, 51, 61 and / or modify their control parameters according to the insufficient or excessive condition of electric energy (detected, estimated or foreseen insufficient or excessive condition) and the selected heating mode.

[0064] In an ideal situation, the demand for electrical energy and the energy fed into the grid are balanced. In reality, these values ​​differ from each other, resulting in an unbalanced situation, which leads to frequency and voltage drifts. Beyond the allowed interval, the grid cannot tolerate this imbalance, and consumers or generators may have to be disconnected in order to avoid damage or a total blackout or in any case to comply with voltage and frequency standards. In the following, a situation of severe imbalance in the energy supply will be referred to as a shortage situation; vice versa, a situation of severe imbalance in the energy fed into the grid will be referred to as an excess situation.

[0065] Several severity levels may be defined in a power grid deficit condition (towards demand imbalance) and / or in a power surplus condition (towards supply imbalance); and preferably, the water heater 1 is configured to respond to at least two different severity levels (hereinafter referred to as "levels") for power grid deficit conditions and / or power grid surplus conditions.

[0066] In one possible embodiment, the regulator 5 is adapted to manage the following severity levels (listed in order of increasing severity): - The first level of power shortage, which represents a moderate imbalance to demand, is called "Load shed"; - A second level of power shortage, representing a strong imbalance with demand, called a “Critical peak event”; - The third level of power shortage, which represents a very strong imbalance in demand with the risk of disconnection, is called "Grid emergency"; - The first level of excess energy, representing a moderate imbalance in supply, is called "Load up"; and - The second level of excess power, which indicates a strong imbalance in supply, is called "Advanced load up".

[0067] It should be noted that the response of the water heater 1 does not guarantee an immediate deterministic change in the consumption level, but there is a probability associated with a change in consumption, and this probability increases with the severity level and the persistence of the grid conditions over time. This is because of the physical limitations of the thermal system and because the regulator 5 of the water heater 1 preferably implements rules that ensure that a minimum comfort level is maintained. If there are multiple water heaters 1 in the same grid, the overall effect of the change in energy demand is deterministic for a larger number, thus achieving the goal of balancing the grid.

[0068] According to a first embodiment, the water heater 1 is capable of receiving a signal S, and the regulator 5 is configured to respond to the signal S according to at least some of the five defined severity levels (first, second and third power shortage levels: "Load shed", "Critical peak event" and "Grid emergency"; first and second power surplus levels: "Load up" and "Aadvanced load up"), the signal S indicating a power shortage or surplus condition in the power grid.

[0069] Several known protocols allow a device connected to the electrical grid to receive a signal S corresponding to at least some of the listed severity levels. Some protocols include in the signal S the severity level and the duration required for a response.

[0070] As a non-limiting example, the water heater 1 may be configured to receive signals compatible with protocol CTA2045. Similar protocols are increasingly common in general because they are used to implement so-called "demand response" services that allow the energy supply to be flexible over a period of time in order to closely follow demand.

[0071] The water heater 1 may directly receive the signal S from the power grid, or may indirectly receive the signal S with the aid of other devices that receive the signal S from the power grid.

[0072] According to a possible embodiment, the signal S is sent to the water heater 1 by a local device that manages the energy consumption of one or more devices.

[0073] In a second embodiment, the water heater 1 responds to an hourly energy price table and assigns one of the severity levels to a price value that is higher or lower relative to the average. Without loss of generality, the hourly price table can be preset in the water heater 1, the user manually updates the table, the water heater 1 periodically updates the table or receives the table in real time, and the water heater 1 is configured to receive and manage hourly price signals. As a non-limiting example, the water heater 1 can be configured to receive hourly rate signals using protocol JA-13.

[0074] The same water heater 1 can be configured to receive the signal S and set an hourly price list. The first, second and third power shortage levels ("Load shed", "Critical peak event" and "Grid emergency") take precedence over any other settings including the hourly price list. Preferably, the response to the grid condition takes precedence over the hourly price list. Typically, the water heater 1 takes precedence over the signal S from the grid.

[0075] The water heater 1 can work as follows: 1. receiving input from a user interface of a heating mode "Comfort", "I-memory", "Green", "Fast", "I-memory green", "I-memory fast" defining a control logic for each heating element; 2. receiving a first signal S and a duration, the first signal being associated with one of the severity levels of a power shortage or surplus condition in the grid, the severity level being one of a list comprising first, second and third power shortage levels “Load shed”, “Critical peak event”, “Grid emergency” and first and second power surplus levels “Load up”, “Advanced load up”; 3. Depending on the selected heating mode and severity level, a new constant temperature Ttarget is set for all heating elements and / or a new hysteresis Thyst is set for the bottom heating element; - In case of the third power shortage level "Grid emergency", the heating elements are deactivated; - in the heat pump model, in the event of a second power shortage level "Critical peak event", the resistors 41 , 51 are deactivated, and in the case of an electric water heater, the bottom resistor 51 is deactivated; - If the second signal S arrives, return to step 2; - if a new heating mode "Comfort", "Green", "I-memory", "fast", "I-memorygreen", "I-memory fast" is selected or a new temperature Tset is set, step 3 is continued with the new heating mode or the newly set temperature value Tset for the remaining duration; - At the end of the duration associated with the signal S, the control logic associated with the selected heating mode is restored.

[0076] The water heater 1 can be configured to respond to the hourly energy price schedule by associating severity levels corresponding to excess energy conditions with lower price values, by lowering the price and increasing the excess energy severity level, and by associating severity levels corresponding to insufficient energy conditions with higher prices, by increasing the price and increasing the insufficient energy severity level. Preferably, prices at intermediate levels are not associated with any severity level.

[0077] use Figure 3.a and Figure 3.b A method for optimizing consumption according to an hourly rate price schedule is described. The method comprises the following steps: Step 1: receiving a heating mode defining a control logic for each heating element from the user interface 7; Step 2: Reading in a memory or receiving from an input or from the grid an hourly energy price schedule, each hourly energy price schedule being associated with a time period of the day known as a time band; The order in which step 1 or step 2 is executed is irrelevant: Step 3: Identify the lowest price and the highest price among all prices associated with various time bands; Step 4: Select the severity level of response required; Step 5: Divide the interval between the lowest and highest prices into as many sub-intervals as the selected severity levels, plus possible intermediate intervals; Step 6: Sort the intervals by increasing price, and: - Associate the lowest price bands with electricity surplus conditions in order of decreasing severity and increasing price; - associate higher price bands with power shortage conditions in order of decreasing severity and increasing price; - Make the middle price range not associated with any severity level; Step 7: For each new time band where the price does not fall within the middle level, the heating element is controlled according to the active heating mode and the severity level.

[0078] Figure 3.a A diagram according to a possible implementation is shown, wherein the selected severity levels are first and second power shortage levels "Load shed", "Critical peak event" and a first power surplus level "Loadup". Figure 3.b A second possible implementation is shown, in which all defined severity levels are selected.

[0079] Some preferred embodiments of varying control parameters according to severity level are described below.

[0080] As described above, the water heater 1 is configured to respond to different severity levels by modifying control parameters; according to a preferred embodiment, the control parameters include at least the constant temperature Ttarget. Preferably, the control parameters also include the upper hysteresis ThystDome and / or the bottom hysteresis Thyst.

[0081] For the first power shortage level "load shed", the water heater 1 sets the constant temperature Ttarget to the minimum value between the comfort threshold Tcomfort and the previous constant temperature Ttarget, and the formula is as follows: Ttarget = min (Tcomfort, Ttarget) The comfort threshold Tcomfort is a value comprised in a comfort interval corresponding to approximately 40°C-50°C, which is preferably equal to approximately 42°C.

[0082] In any heating mode, the thermostatic temperature Ttarget may already be below the comfort threshold Tcomfort = 42°C because the user has set it to a minimum value or it is set by the algorithm in the case of the second mode I-memory. In all other cases, an actual reduction in consumption is achieved.

[0083] In some possible embodiments, the water heater 1 combines the reduction of the thermostatic temperature Ttarget and the deactivation of the bottom resistor 51 to respond to the second power shortage level "critical peak event", and in the case of the heat pump model, by heating only with the heat pump, it also deactivates the upper resistor 41. This response is applicable to all heating modes.

[0084] In response to the third power shortage level "Grid emergency", the water heater 1 can deactivate all heating elements and / or can set the thermostatic temperature Ttarget to a value just above the average temperature of tap water, equal to 16° C. as a non-limiting example. In this case, functionality is no longer guaranteed; the third power shortage level "Grid emergency" represents a risk of power outage or an hourly energy cost that the user is unwilling to bear.

[0085] According to a possible embodiment, the bottom hysteresis Thyst in normal mains conditions is greater than or equal to 4°C and, in response to the first level of excess electrical energy "Load up", the water heater 1 increases the average temperature of the bottom relative to the thermostatic temperature Ttarget; this is achieved by reducing the bottom hysteresis Thyst, which corresponds to increasing the temperature of the enabling element. For example, the hysteresis can be reduced to a value lower than or equal to 3°C. It should be noted that in an alternative embodiment of the shut-off threshold defined by the hysteresis, the hysteresis will be increased in order to obtain the same average temperature increase effect.

[0086] In response to the second power surplus level "Advanced load up", in addition to increasing the average temperature of the bottom, the water heater 1 can increase the constant temperature Ttarget to the maximum temperature Tmax by reducing the bottom hysteresis Thyst. In the case of the third mode "Green", the maximum value of the constant temperature Ttarget has the heat pump threshold Thp as an upper limit.

[0087] It should be noted that the response to the severity level maintains the basic characteristics of the heating mode, for example, if the thermostatic temperature Ttarget is 40°C in the second mode I-memory, the severity level "Load up" will result in a reduction in the bottom hysteresis Thyst (i.e. a small increase in the average temperature of the bottom relative to the thermostatic control temperature Ttarget) instead of causing the thermostat to be increased at an unnecessary temperature.

[0088] In other words, the regulator 5 is configured so that the response to the severity level does not constitute a switch from one mode to another, but rather a modification within the selected heating mode. The response to the severity level is thus combined with the control logic determined by the selected heating mode, resulting in a modified logic that depends on both the selected heating mode and the severity level.

[0089] Any reference to a user interface should be understood in a broad sense and includes any device capable of receiving input from a user and sending it to the regulator 5; in particular, as non-limiting examples, it includes a dedicated physical user interface 7 included in the water heater or an interface of a smart phone or other device that is not part of the water heater 1 but from which the water heater 1 is configured to receive input using any known communication technology (including wireless communication or voice command sensors).

[0090] It is clear to the expert in the field that a system having the characteristics of the water heater 1 can be used to heat other types of liquids and is not limited to water.

Claims

1. A water heater (1), powered by electric energy from a power grid, the water heater comprising: - a vertically arranged water reservoir (10) having an upper part (11) and a bottom part (12), to which respective upper temperature sensors (42) and bottom temperature sensors (52) and at least one respective upper heating element (41) and bottom heating element (51; 61) are associated, the at least one respective upper heating element (41) and bottom heating element (51; 61) being suitable for heating liquid in the reservoir (10); - an interface (7) for selecting one of at least two heating modes (Comfort, I-memory, Green, Fast, I-memory green, I-memory fast) different from each other through the control logic of the heating element (41; 51; 61), and the heating mode is configured to reach a user set temperature Tset, or a temperature threshold Thp or an optimized temperature Tmem of the heating element of the condenser (61) of the heat pump (6); - a regulator (5) of a heating element (41; 51; 61), adapted to receive the reading of a selected heating mode (Comfort, I-memory, Green, Fast, I-memory green, I-memory fast) from said temperature sensor (42; 52) and to execute a control logic of said heating element (41; 51; 61) according to said selected heating mode; The water heater (1) is characterized in that the regulator (5) is configured to modify the control parameters of the heating element (41; 51; 61) in response to a detected and / or estimated and / or expected grid power shortage or surplus condition, and the behavior caused by the response to the grid condition is related to both the grid condition and the user-selected heating mode.

2. The water heater (1) according to claim 1, wherein: The control parameters modified in response to the conditions of the grid include at least a common constant temperature Ttarget of all active heating elements.

3. The water heater (1) according to claim 1 or 2, wherein: Energy deficit and / or excess conditions of the power grid may be associated with severity levels, and the regulator (5) is configured to respond in different ways to at least two of the following severity levels listed in increasing order for each condition: - The first power shortage level (Load shed); - Second power shortage level (Critical peak event); - The third power shortage level (Grid emergency); - The first level of excess power (Load up); - The second level of excess power (Advanced load up).

4. The water heater (1) according to claim 3, wherein: The regulator (5) is configured to set a feasible new thermostatic temperature Ttarget for all heating elements and / or a feasible new hysteresis Thyst for the bottom heating element according to the detected severity level.

5. The water heater (1) according to claim 3 or 4, configured to respond to the first load shed level (Load shed) by setting the thermostatic temperature Ttarget to the minimum value between the comfort threshold Tcomfort and the previous thermostatic temperature Ttarget, the formula is as follows: Ttarget = min (Tcomfort, Ttarget) Therein the comfort threshold Tcomfort is a value comprised in the interval 40°C to 50°C, preferably it is equal to about 42°C.

6. The water heater (1) according to claim 5, configured to respond to the second critical peak event by: implementing a response to the first load shed, and in addition: If the heating element comprises a heat pump (6), by deactivating any resistive element (41; 51), Otherwise by deactivating at least one of the bottom resistive elements (51).

7. The water heater (1) according to any one of claims 34 to 6, configured to have a hysteresis Thyst of the bottom heating element (51; 61) in the following models: - Model with only bottom resistive type elements, comprised within the interval 4°C to 21°C, and preferably equal to 15°C; - A model comprising at least one condenser of the heat pump as a bottom heating element, comprised in the interval 4°C to 20°C, and preferably equal to 5°C; And configured to respond to the first excess power level (Load up) by making the hysteresis Thyst of the bottom element reach a value lower than or equal to 3°C.

8. The water heater (1) according to claim 7, configured to respond to the second level of excess electrical energy (Advanced Load up) by: implementing a response to the first level of excess electrical energy (load up), and in addition: - if only resistive heating elements are provided, by setting said constant temperature Ttarget equal to a predetermined maximum temperature Tmax; - If at least one heat pump (6) is provided and the sustainable heating mode (Green; I-memory green) is selected, characterised in that By setting the thermostatic temperature Ttarget equal to the minimum value between the maximum temperature Tmax provided for the thermostat and the maximum temperature threshold Th that the heat pump (6) can reach, the use of the heating element is restricted to the heat pump (6).

9. A water heater (1) according to any one of claims 2, 3, 4, 5, 6, 7 or 8, configured to receive a signal (S), said regulator (5) being capable of processing said signal and conveying the condition of the grid and optionally said severity level.

10. A water heater (1) according to any one of claims 3, 4, 5, 6, 7, 8 or 9, configured to respond to an hourly price schedule for energy prices by associating severity levels corresponding to excess energy conditions with lower price values, with price increases causing the severity level to decrease, and associating severity levels corresponding to insufficient energy conditions with higher prices, with cost increases causing the severity level to increase.

11. A method for heating a liquid in a water heater (1) according to any one of claims 3 to 10, the method comprising: Step 1: receiving a selection of a heating mode (Comfort), (I-memory), (Green), (Fast), (I-memory green), (I-memory fast) defining a control logic for each heating element from a user interface (7); Step 2: receiving a first signal (S) associated with a severity level and a duration of a power shortage or excess condition in a power grid, wherein the severity level belongs to the following list: a first power shortage level (Load shed), a second power shortage level (Critical peak event), a third power shortage level (Grid emergency), a first power excess level (Loadup), and a second power excess level (Advanced load up); Step 3: According to the selected heating mode and severity level, set a feasible new constant temperature Ttarget for all heating elements and / or set a feasible new hysteresis Thyst for the bottom heating element; - In case of the third power shortage level (Grid emergency), deactivation of the heating elements; - if the heating element comprises a heat pump, in the event of a second power shortage level (Critical peak event), deactivating any resistive element (41, 51); - otherwise deactivating at least one of the bottom resistive elements (51); - If the second signal (S) arrives, repeat step 2; - Otherwise, if a new heating mode (Comfort), (green), (I-memory), (fast), (I-memory green) or (I-memory fast) is selected or a new temperature Tset is set, continue with step 3 for the remaining duration with the new heating mode or the new set temperature Tset value.

12. A method for heating liquid in a water heater (1) according to an hourly rate tariff, the water heater (1) being a water heater (1) according to claim 3 or any claim dependent thereon, the method comprising the steps of: Step 1: receiving a heating mode defining a control logic for each heating element from a user interface (7); Step 2: Read the hourly price list into memory or receive the hourly price list from the input or the grid, wherein the order between steps 1 or 2 is irrelevant; Step 3: Divide the interval between the lowest and highest prices into as many sub-intervals as the overall severity level, plus possible intermediate intervals; Step 4: Sort the intervals in order of increasing price and associate them to severity levels, by associating lower price intervals with excess power conditions in order of decreasing severity and increasing price, and associating higher price intervals with insufficient power conditions in order of decreasing severity and decreasing price, leaving the middle intervals unassociated with any severity level. Step 5: For each new time band in which the price does not belong to the middle range, deactivate the heating elements and / or modify their control parameters according to the active heating mode (Comfort), (Green), (I-memory), (Fast), (I-memory green) or (I-memory fast) and the severity level (Load shed), (Critical peak event), (Grid emergency), (Load up), (Advanced Loadup).

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