Electric heating device and system, and method of controlling the same

Abstract

The invention relates to an electric heating device, including heat storage means, at least one electric heater configured to heat the heat storage means, and heat transport means, configured to transport heat from the heat storage means to the surroundings of the electric heating device, wherein the heat transport means are adjustable between a first setting, in which the transport of heat is relatively limited, and a second setting in which the transport of heat is less limited. According to the invention, the device comprises a controller operatively connected to the at least one electric heater for controlling the at least one electric heater, and to the heat transport means for changing back and forth from the first and second setting thereof. A related system and method are also disclosed.

Description

[0001] ELECTRIC HEATING DEVICE AND SYSTEM, AND METHOD OF CONTROLLING THE SAME

[0002] The invention relates to an electric heating device, including:

[0003] - heat storage means;

[0004] - at least one electric heater configured to heat the heat storage means; and

[0005] - heat transport means, configured to transport heat from the heat storage means to the surroundings of the electric heating device, wherein the heat transport means are adjustable between a first setting, in which the transport of heat is relatively limited, and a second setting in which the transport of heat is less limited.

[0006] In general, heating devices are known. Heat produced is often controlled by engaging the electric heater when heat is needed, and disengaging when no heat is needed.

[0007] According to the invention, it is possible to make better use of changing costs for electric energy if not only the heater is controlled, but also the transport means. Therefore, the invention provides an electric heating device as described in the preamble, which also comprises

[0008] - a controller operatively connected to the at least one electric heater for controlling the at least one electric heater, and to the heat transport means for changing back and forth from the first and second setting thereof.

[0009] Since the controller can control both the heat transport means and the electric heater, it becomes possible to heat the heat storage means at a moment when energy is relatively cheap, and to give off heat when it is needed but may be more expensive.

[0010] In particular, the electric heating device, in particular the electric heater(s) thereof, may be controlled and switched on or off from a server based central artificial intelligent controlling system, and may act as a high capacity energy storage device for heat, i.e. the home battery equivalent for heat. The home storage solution thus obtained allows locally to compensate for the imbalance of the available electric capacity of an electricity grid.

[0011] Due to industrial and social activity during the day, electricity demand was historically higher during the day and it was common to have two tariffs for electricity. A low night tariff and a day tariff. At night, low tariff heat was stored in water like in hot water boilers or in stone for stoves to be released when it was required at high tariff moments. Such known boilers are designed to contain the heat as long as possible with the highest thermal insulation grade to meet the best energy efficiency label.

[0012] Nowadays the volatility in energy demand and availability is increasing due to solar and wind resources and peak demand due to social patterns at wake up time or at the end of a working day collectively charging the electric vehicle , cooking evening dinner and TV time at night. In the past two years, energy companies introduced dynamic variable energy contracts to individual electricity users with hourly tariff rates available 24 hours in advance. The daily hourly tariff fluctuations are in the future expected to become more volatile due to the progressing energy transition away from fossil energy resources to natural resources like wind and solar. At the same time, increased peak demand by mass collective charging of electric vehicles adds to a supplydemand imbalance. Currently, as a result of increased peak PV energy and charging electric vehicles there are in general two 12 hours cycles a day recognizable with each a low and high tariff period.

[0013] The applicant has realized that the specific heat capacity of water (or some other heat storage medium) can be used for home heating, resulting in relatively cost effective and sustainable heat storage for frequent short cycle buffered heating, using a device as described herein. To utilize the energy storage capability optimally it should heat a storage tank or tanks of preferably at least 25 litres up to e.g. 300 litres.

[0014] For this purpose, the heat storage means may include at least one storage tank, preferably two or more storage tanks, in particular one or more water storage tanks optionally including water.

[0015] In case multiple tanks are used, they may be interconnected, so that their interiors are linked.

[0016] The at least one storage tank may be provided with a circulation pump. Such a pump can be used to prevent thermal layering of liquid (e.g. water) in the tank, thereby enhancing heat transfer to the environment. The circulation pump may be controlled by the controller. In particular, the pump may be engaged when the transport means are set to the second setting, and disengaged when the transport means are set to the first setting.

[0017] The at least one storage tank may be configured to be pressurized when reaching its maximum heating temperature, or is pressurized, preferably up to at least 2 bar, more preferably up to at least 3 bar. Accordingly, the amount of heat stored can be increased, because under higher pressure the boiling point is elevated.

[0018] The at least one storage tank or interconnected tanks may comprise a pressure release valve, for safety. If a housing is provided, the pressure release valve may release inside the housing to prevent burning users in the vicinity of the electric heating device.

[0019] Practically, the volume capacity will be limited by the maximum volume that can be heated with the available electric power in less than ca. 6 hours to a temperature just under the boiling temperature of the storage medium, which may be water. Depending on the operating pressure in the tank, the maximum temperature is preferably not higher than 15% below the boiling point at that pressure. For water as an example, a working pressure of 2 to 3 Bar results in a boiling point from 120 to 140°C. To utilize the energy storage capacity optimally, the stored heat should, after reaching a high temperature, be released from the tanks over a similar period of 5 to 6 hours before a new heating charging cycle will start, so that the heating cycle corresponds to the periodicity of the energy tariffs as explained above. The ideal situation of store and releasing heat would be in 4 equal cycles of 6 hours within every 24 hours. Due to changing ambient temperatures, varying low and high tariff times and the time of heat requirement, the cycle times will not be exactly equally long. In fact, more than 2 cycles of storing and releasing heat within a day are possible.

[0020] In any case, the device can be controlled to store energy in the device by heating up water at the lowest real-time energy price within a 24 hours cycle whilst relieving the electric grid from peak loads by releasing the stored energy off-grid during peak-times (which correspond to high- tariff times.

[0021] To actually store heat, the heat storage means are heated by the heater. In particular, an electric heater is provided for, especially in, each storage tank, so that medium (such as water) in the tank(s) can be heated when required.

[0022] Switching the heaters on and off between storing the heat in the heat storage means and releasing the heat from the heat storage means is controlled by e.g. tariff controlled WiFi power switches through internet. The controller may implement such switches, so that both the electric heater(s) and the transport means are controlled.

[0023] The electric heating device may be connected with a webhost in the cloud (e.g. on the server) storing Al processed data based on future tariff fluctuations provided a day ahead, and other relevant variables related to the electric heating device, such as storage capacity. The server may embody a self-learning behaviour model of released heat of each connected electric heating device. Algorithms may be used to process tariffs, home system data with time and temperature variables, historic system behaviour and external variable data such as social heating behaviour, local weather forecast, wind and the modelled behaviour of thermal isolation of the house, to provide the most effective heating at the lowest possible cost.

[0024] To allow server based remote control, the electric heating device may comprise a communication module for receiving instructions from the remote server.

[0025] The server may and the electric heating device together may form a heating system. Multiple electric heating devices may be connected to the same server, for being controlled by it. Of course the server need not be a single computer or processor per se, and may be a distributed service, or any other suitable remote service or remote control application.

[0026] The server, may be configured to perform the following steps, for each heating device a) obtain projected electricity prices for the electric heating device; b) obtain variables indicative of circumstances local to the electric heating device; and c) based on the electricity prices and the variables, provide instructions for the controller to control the at least one electric heater and the heat transport means.

[0027] The controller of the electric heating device may comprise of be connected to a temperature sensor, such as a thermometer, for obtaining the local temperature.

[0028] The application also relates a to a method of controlling at least one, preferably more heating devices, comprising - for each heating device: a) obtaining projected electricity prices for the electric heating device; b) obtaining variables indicative of circumstances local to the heating device; and c) based on the electricity prices and the variables, operate the electric heating device.

[0029] To arrive at a low-cost heating strategy, step c) may comprise controlling the heat transport means of the heating device to keep the temperature in a space in which the heating device is located within predefined boundaries, whilst controlling the at least one electric heater to heat the heat storage means during periods of relatively low cost electricity.

[0030] In general relevant variables for the method or system include one or more of:

[0031] - a weather forecast;

[0032] - historic behaviour of the heating device;

[0033] - behaviour patterns, historic or projected, of users of the heating device;

[0034] - a user-selected desired temperature or comfort level for a space in which the heating device is located; and

[0035] - insulation characteristics of a space in which the heating device is located.

[0036] Heat transport may be effected by radiation, by radiating some heat away from the device, in addition or as an alternative, heat may be transported by heating air which is allowed to flow away by convection. In particular, the heat storage means are kept in place. In the example of one or more storage tanks, the medium in the tank (such as water) is kept in the tank, and heat may be transported by heating air with the tank and the water inside it, using a heat exchanger. The tanks may otherwise be sealed during normal operation.

[0037] In practice, the electric heating device comprises a housing, which houses at least the heat storage means and the at least one electric heater, wherein optionally the housing also houses the vent of the heat storage means and / or the controller.

[0038] To allow some radiation, i.e. a deliberate but relatively small continuous heat loss, the heat storage means and the housing may be in heat exchanging contact. The heat exchanging contact may be made using metal strips extending from the tanks to the housing.

[0039] The skilled person will realize that the amount of heat radiated by the housing can be adjusted using the heat exchanging contact. As an example, if metal strips are used to create said contact, the provision of more metal strips, or strips of a larger cross section, the amount of heat radiated away from the housing is increased. Of course, the opposite is also true. In practice, the heat contact would be chosen such that the heat flux through radiation from the housing is a predefined portion of the total heat stored, or of the total heat loss, for instance over a cycle. The predefined portion may be e.g. at least 10%, preferably at least 20%, more preferably at least 30%.

[0040] The heat contact between heat storage means and the housing is conductive in nature, i.e. a physical heat transferring connection may be made, e.g. via metal parts joining the two components.

[0041] The same can also be viewed as a ratio between heat transport via radiation as compared to convection, which would be the only other significant transport mode. The ratio of heat lost via radiation versus convection may thus be at least 10:90, preferably at least 20:80, more preferably at least 30:90, preferably defined when the transport means are in the second setting.

[0042] The thermal contact may cause the housing to heat up and radiate some heat away continuously. The continuous radiating heat loss is perceived as comfortable by users.

[0043] In practice, the heat exchanging contact is configured so that during normal use, the housing does not heat up sufficiently to bum a user touching the housing. Instead, the housing is heated to give off a comforting feeling, whereas the bulk of heating is performed through convection.

[0044] To optimize the heat exchanging contact, the heat exchanging contact is present on multiple locations spread across a surface area of the housing.

[0045] The heat transport means may comprise a convection channel along the heat storage means. The wall of the tanks may accordingly form a heat exchanger, which gives of heat to the air passing through the channel. A separate heat exchanger in thermal contact with both the tank (and the water) and the air may also be provided, however it is possible the tanks themselves are capable of transferring sufficient heat if the air is allowed to transport away due to convection.

[0046] The heat transport means may further comprises a shutter configured to in the first setting close a relatively large portion or all of the convection channel, and in the second setting close a smaller portion or none of the convection channel.

[0047] The shutter may allow or prevent convection, so that the amount of heat given off to the environment can be controlled to some extent. Of course, if thermal contact with the housing is employed, said heat loss cannot be eliminated using the shutter.

[0048] It is particularly advantageous if said thermal contact is present whilst the convection can be controlled. In this way, a user will have a continued comfort by the radiation, whereas the more relevant heat flux caused by convection can be used to control to a large extent how much heat is given off and at what time. The convection channel may be covered with an air permeable grid on an inlet and / or outlet side thereof, for safety, to prevent access, or to prevent e.g. dust, debris, etc. from entering the channel.

[0049] The at least one electric heater may provided with a temperature controlled shut-off switch, configured to use the temperature of the heat storage means, to safeguard operation.

[0050] Each of the at least one electric heaters preferably has a capacity of at least 1000 W, more preferably of at least 1500 W. Such a capacity is sufficient for heating a reasonable amount of water twice a day, yet is readily available and can be powered using normal plugs and require no high-capacity fuses.

[0051] The heat storage means may have a capacity of at least 5 kWh, preferably of at least 10 kWh. A reasonable sized heater may thus be obtained, that can provide a relevant amount of heating for e.g. a home.

[0052] EXAMPLE

[0053] As an example an electric heating device containing 100 litres of water to explain the inventive use the device. It is noted that since the device also heats a house, use is made of the heat capacity of the house and its physical elements as the water system, stone walls, concrete and tile floors, all of these working as on-line heat accumulators, the house functioning as a matter of saying as a thermal storage. Further clarification of the energy storage and release is presented with a 100 litre electric heating device, which could of course be scaled by changing the tank volume and heater capacity to larger or smaller capacities.

[0054] The specific heat capacity of water is 4.2 KJ / litre / °C. 100 litre is equivalent to 420 KJ / °C. The tap water temperature is approximately 12 °C which can be heated to 102°C staying 15% under the boiling point of 120 °C at 2 Bar. This results in 420 x 90°C = 37.800 KJ or 10,5 kWh of heat storage. Steel tanks can be provided, e.g. with a specific heat capacity of 0,53 KJ / kg / °C and weights 35 kg to hold the 100 litres of water. The tanks thus store (0,53 x 35) x 90 °C = 1700 KJ = 0,47 kWh additionally. The total heat storage capacity is 10.5 + 0,47 = 10,97 kWh for 100 litres of water in steel tanks. This amount of heat is ideally used (i.e. passed to the environment and recharged by the heaters) twice a day.

[0055] In practice the tank will take long to cool down to a temperature which is close to the room temperature due to the relatively low temperature gradient at that time. The average cooling period is set at ca. 6 hours. Considering the winter weather, with wind, humidity and temperature outside the house, it is realistic to assume an average cooling down of the tanks to 27°C over such period, reducing the stored heat capacity per cycle of 12 hours to 420 x 75°C = 31.500 KJ or 8,75 kWh + 0,39 kWh for the steel tanks resulting in a 9, 14 kWh realistic heat storage capacity twice a day. Presented is a proposed solution of a modified commercially available boiler which is not connected to the pressured tap water piping system. For its operation it is a closed system and can be filled with water one time. For this purpose, the device may comprise a water inlet, for instance provided with a one-way valve. Suitable couplings are available, such as those commonly known in garden watering installations.

[0056] The use of existing boiler production technology may be part of the invention to enable quick implementation of the proposed solution. The proposed heat storage means will not be thermally insulated with respect to its housing, which may generally be made of plate-metal. The bottom of the apparatus may be open and on the top of the apparatus there may be a sliding air grille which can be opened to let air through or closed to stop airflow. A convection channel may be made in between. This represents a practical approach of a simple solution using water (in the boiler tank) as energy accumulator for heating at high tariff moments without using the grid at that time.

[0057] The heated tank, which may have an outside temperature of up to 85°C, should have more length than width to promote hot air convection by heating the air between the tank and outer housing. The length is defined in the vertical direction in use of the device. The hot air will flow through a manually, thermally or electrically closable air grille or valve on top of the apparatus. As described above, the grill or any other type of shutter, could be operated by the controller. When the grille is closed there will be no airflow by convection and the outer housing will only radiate limited heat by the heat convection from the tanks to the outer casing and through a number of metal heat conduction mounting strips between the tanks and the outer casing. These strips are used to modify the commercially available boiler by breaking the insulation normally present therein, and establishing thermal contact between tank and housing.

[0058] The apparatus described herein is as such can be applied as an relatively cost effective heat accumulator and radiator functioning as an environment heating device over a couple of hours per day by releasing the stored heat by convection and radiation. Such solution is likely the most cost effective when variable hourly energy tariffs are available. Other than using low-tariff energy, the device as described herein may also find use to limit peak use of the electricity grid, or both.

[0059] For optimal heat storage in water, the device requires smart control of the water heating and optimal heat release calculated by advanced algorithms with system model variables and external variables like local weather and social model heating requirement affected by work, home presence or weekends. This results in modelling each house or space in which the electric heating device is placed, with the most optimal on- off control of the heater and heat transport means, e.g. by WiFi powerline switches, to store the heat in the heat storage stoves, concrete and tile floors or inner building walls by embedded resistive heating wires or heating foil. In general, it is noted that the heat storage means may thus be embodied as the environment that is being heated. Even in such a case, the advantageous principles set about in this application may be applied. However, it is advantageous to provide further heat storage capacity in the form of one or more tanks fdled with water, which can be done relatively cost effectively by modifying existing boilers, or producing a similar apparatus.

[0060] Hereinafter the invention will be elucidated more in detail with reference to the figures, in which:

[0061] Figure 1 schematically shows a cross sectional views from a top, front and bottom of a water boiler converted to an electric heating device; and

[0062] Figure 2 schematically shows a temperature of a room heated by such a device, temperature of the heat storage means, and energy tariffs.

[0063] Figure 1 shows an exemplary embodiment of the heat storage stove device according to the invention with two interconnected tanks 1 of 50 up to 150 litre each. Both tanks contain water and an electric heater element 2 of at least 1000W but preferably 1500W each. The electric heaters are connected through a thermal switch which limits the temperature of the water in the tanks to a maximum temperature 102°C at 2 Bar or a higher correlated temperature keeping the water 15% under the boiling point at a higher pressure. The maximum pressure is limited by the pressure valve 10. The normal operating pressure for commercially available boiler tanks is approximately 2 Bar but the tanks are designed and tested by imposed safety standards to handle pressures up of 6 to 9 Bar. The advantage of increased pressure is a higher boiling point and therefore a higher thermal storage capacity and faster heating / cooling cycles. The electric heaters will be switched off when reaching the maximal adjusted temperature of the thermal switch 3 or when the tariff is no longer attractive. The heat storage stove is connected by a power cord with plug with protective earth 4. The heaters are both connected by cord 5 via the thermal safety switch. The bottom side of the heat storage device is open with a protective grid 6 to prevent undesired physical contact with the hot tanks. The system will be filled with water through a cold water inlet tap 7 with e.g. a pluggable garden hose until water sprinkles out of the hot water valve 8, which also serves to release air during fillingTap 7 and 8 can be closed with e.g. a screwable end cap. In general, it is possible to use the taps 7, 8 to connect e.g. a radiator 14 to further enhance heat transfer if needed. Suitable pressure capable (flexible) tubing is readily available for this purpose, or can by flexible pressure capable tubes be connected to an optional radiator. Filling needs to be done only once as water is kept in the tank afterwards. A circulation pump 13 may keep the temperature over both tanks evenly distributed to increase heat release, and provide water circulation to an optional external radiator. The optional radiator(s) 14 discussed herein find particular use in combination with relatively large volume tanks (e.g. >100L). On top of the device is a closable air grille 9 which will be manually or electrically moved to regulate the heat release during the chargedischarge cycles. With grille 9 closed there will be little to no convection airflow through the heat storage stove and only a limited amount of heat will be released by heat radiation of the outer casing 12 of the stove. To prevent unacceptable overpressure in the tanks there is a pressure safety valve 10 which will release overpressure by steam or water drops. The exit of this overpressure valve could be within the outer casing of the stove to prevent burnings by hot steam. A critical part of the design is the heat release from the tanks to the outer casing of the device. Available boilers do not have any thermal conductive connection of significance to the outer casing of the boiler, they are in fact insulated. For a heating device there could be multiple thermal conductive connections 11 with the outer casing at multiple points of the housing to provide a comfortable evenly distributed warmth over the outer casing 12 surface, which will start to radiate heat for comfort. The outer case connection on the flat sides of the tank will be made on the four flat bars which connect the two tanks at the top and bottom. These bars can reach temperatures up to 102°C which implies that the outer case should have a reduced thermal conductivity from the flat bars to the plated outer case by applying some thermal isolation or bended steel plate strips keeping an air gap between the tanks and outer case while also reducing the heat conduction. Some similar metal mounting strips 11 at the round sides of the outer casing around the tanks will also conduct limited heat to the outer case.

[0064] Figure 2 shows an average hourly tariff table of an average day in beginning of January 2023 with calculated optimal points for the variables of that day to optimal charge and discharge the heat. The 24 hr. timescale baseline shows the varying tariff per hour. The host algorithms will switch the heaters on through the WiFi switch at a calculated optimum and switch of when the tariff gets high or when the thermal switch reached the set maximum temperature.

[0065] As can be seen, the algorithm decides if the heaters can achieve full charge in 5 or 6 hours and should switch on at 0:00 hr. or 1:00 hr. Once the maximum temperature is reached the air grille on top of the device should remain closed until wake up time to save most of the heat until 7:00 or 8:00 am for the remainder of the morning. A new charging cycle can start at 10:00 or 11:00 am. During the day the heat up could be with the air grille open when there is presence in the room. This will take a longer heat up time. This will all be calculated with advanced algorithms and artificial intelligence.

[0066] Although the invention has been explained with reference to specific examples and embodiments, it is not limited thereto. In fact, the invention is described also be the following claims.

Claims

Claims1. Electric heating device, including:- heat storage means;- at least one electric heater configured to heat the heat storage means; and- heat transport means, configured to transport heat from the heat storage means to the surroundings of the electric heating device, wherein the heat transport means are adjustable between a first setting, in which the transport of heat is relatively limited, and a second setting in which the transport of heat is less limited; characterized by- a controller operatively connected to the at least one electric heater for controlling the at least one electric heater, and to the heat transport means for changing back and forth from the first and second setting thereof.

2. Electric heating device according to the previous claim, wherein the heat storage means include at least one storage tank, preferably two or more storage tanks, in particular one or more water storage tanks optionally including water.

3. Electric heating device according to the previous claim, wherein the at least one storage tank is configured to be pressurized, or is pressurized, preferably up to at least 2 bar, more preferably up to at least 3 bar, even more preferably at least 5 bar.

4. Electric heating device according to the previous claim, wherein the at least one storage tank comprises a pressure release valve.

5. Electric heating device according to any one of claims 2 - 4, wherein an electric heater is provided for, especially in, each storage tank.

6. Electric heating device according to any of the preceding claims, further comprising a housing, which houses at least the heat storage means and the at least one electric heater, wherein optionally the housing also houses the vent of the heat storage means and / or the controller.

7. Electric heating device according to the previous claim, wherein the heat storage means and the housing are in heat conductive exchanging contact, wherein preferably the heat exchanging contact causes a heat flux of at least 10% of the stored heat energy to be emitted by the housing by heat radiation, preferably at least 20%, most preferably at least 30%.

8. Electric heating device according to the previous claim, wherein the heat exchanging contact is present on multiple locations spread across a surface area of the housing.

9. Electric heating device according to any of the preceding claims, wherein the heat transport means comprise a convection channel along the heat storage means.

10. Electric heating device according to the previous claim, wherein the heat transport means further comprise a shutter configured to in the first setting close a relatively large portion or all of the convection channel, and in the second setting close a smaller portion or none of the convection channel.

11. Electric heating device according to any one of claims 9 - 10, wherein the convection channel is covered with an air permeable grid on an inlet and / or outlet side thereof.

12. Electric heating device according to any of the preceding claims, wherein the at least one electric heater is provided with a temperature controlled shut-off switch, configured to take the temperature of the heat storage means.

13. Electric heating device according to any of the preceding claims, wherein each of the at least one electric heaters has a capacity of at least 1000 W, more preferably of at least 1500 W.

14. Electric heating device according to any of the preceding claims, wherein the heat storage means have a capacity of at least 5 kWh, preferably of at least 10 kWh.

15. Electric heating device according to the previous claim, the controller comprising a communication module for receiving instructions from a remote server.

16. Heating system comprising one or more electric heating devices according to the previous claim, and a remote server connected to each of the electric heating devices.

17. Heating system according to the previous claim, wherein the remote server is configured to, for each electric heating device: a) obtain projected electricity prices for the electric heating device; b) obtain variables indicative of circumstances local to the electric heating device; andc) based on the electricity prices and the variables, provide instructions for the controller to control the at least one electric heater and the heat transport means.

18. Method of controlling a least one, preferably more heating devices, preferably according to any one of the claims 1 - 15, wherein the method comprises, for each heating device, a) obtaining projected electricity prices for the electric heating device; b) obtaining variables indicative of circumstances local to the heating device; and c) based on the electricity prices and the variables, operate the electric heating device.

19. Method according to the previous claim, wherein step c) comprises controlling heat transport means of the heating device to keep the temperature in a space in which the heating device is located within predefined boundaries, whilst controlling the at least one electric heater to heat the heat storage means during periods of relatively low cost electricity.

20. Method according to any of the preceding method claims, wherein the variables include one or more of:- a weather forecast;- historic behaviour of the heating device;- behaviour patterns, historic or projected, of users of the heating device;- a user-selected desired temperature or comfort level for a space in which the heating device is located; and- insulation characteristics of a space in which the heating device is located.

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