GB2597245A

GB2597245A - Heating or cooling system with thermal reserve

Info

Publication number: GB2597245A
Application number: GB2010867.6A
Authority: GB
Inventors: James Wyllie Nicholas
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-07-14
Filing date: 2020-07-14
Publication date: 2022-01-26
Anticipated expiration: 2040-07-14
Also published as: GB2597245B; GB202010867D0; WO2022013726A1

Abstract

A heating and/or cooling apparatus 1 comprises a thermally insulated housing 7 defining a first chamber 2 and a second chamber 3, the first chamber having a door 5 and the first chamber is in thermal communication with the second chamber by a thermoelectric module 9, 10. A controller receives an indication that the door of the first chamber is to be opened and the voltage applied to the thermoelectric module is controlled whether or not an indication that the door is to be opened has been received. The open door indication may comprise a schedule of door opening events, the pressing of a button, an unlocking action, sensor data of an approaching user, stopping of a vehicle transporting the apparatus or the proximity of the apparatus to a destination. The chambers may be coupled to a sealed thermal reserve 4 to store thermal energy via the thermoelectric module(s). The reserve may contain air, another gas, liquid, solid material or a phase change material. The first chamber may be an oven and the second chamber may be a refrigerator or freezer with a drawer 6. Further chambers in thermal communication via further thermoelectric modules may be used (fig 2).

Description

Heating or cooling system with thermal reserve Field of the invention [1] The invention relates to a heating and/or cooling system with a thermal reserve. In particular, it relates to a heating and/or cooling system with a temperature controlled chamber openable to the external environment, in thermal communication with a thermal reserve which is not ordinarily openable to the external environment.

Background of the invention

[2] Changing the ambient temperature in a chamber costs energy. To increase the temperature, such as in an oven, heat must be transferred from a store of thermal energy in thermal communication with the chamber, or must be generated by a heat source, converting (for example) chemical or electrical energy into thermal energy.

[3] Decreasing the ambient temperature in a chamber, such as a refrigerator, 15 requires the thermal energy to be drawn from the chamber into either a store of thermal energy or a heat sink.

[4] Most of the energy cost lies in reaching the desired temperature. Once the desired temperature has been reached, it is relatively inexpensive in energy terms to maintain the temperature. In a perfect system, this would not be necessary at all, but in real world systems, there are always losses, due to conduction through the chamber walls, or radiation from the chamber walls, or convection through gaps in the chamber walls.

[5] Significant energy wastage occurs, however, when such a chamber is opened to the external environment in use, after energy has been spent changing its ambient temperature with respect to that of the external environment. In the case of an oven, or other chamber which has been heated, much of the thermal energy transferred to or generated in the chamber escapes to the external environment once, for example, the oven door is opened. In the case of a refrigerator, or other chamber which has been cooled, thermal energy from the external environment enters rapidly when, for example, the refrigerator door is opened.

[006] It is desirable to reduce this wasted energy while still being able to open 5 heated or cooled chambers to the external environment when needed.

Statement of invention

[1] The invention provides an apparatus comprising a thermally insulated housing defining a first chamber and a second chamber, the first chamber comprising a door openable to the external environment, the first chamber being in thermal communication with the second chamber by means of a thermoelectric module; the apparatus further comprising an electrical power supply connected to the thermoelectric module in such a way that a voltage applied across the thermoelectric module can be switched on and off with either polarity; and a controller configured to receive an indication that the door of the first chamber is to be opened; wherein the voltage applied across the thermoelectric module is controlled according to whether or not an indication that the door of the first chamber is to be opened has been received.

[2] The indication that the door of the first chamber is to be opened may comprise at least one of: a schedule of door opening events; the pressing of a button; an unlocking action; sensor data indicating the approach of a user; the stopping of a vehicle transporting the apparatus; or proximity of the apparatus to a destination [3] The voltage applied across the thermoelectric module may be controlled such that the thermoelectric module draws heat from the second chamber into the first chamber when an indication that the door of the first chamber is to be opened is not received. In this case, the voltage applied across the thermoelectric module may be controlled such that the thermoelectric module draws heat from the first chamber into the second chamber when an indication that the door of the first chamber is to be opened is received. Alternatively in this case, the voltage applied across the thermoelectric module may be switched off when an indication that the door fo the first chamber is to be opened is received.

[004] Alternatively, the voltage applied across the thermoelectric module may be 5 controlled to draw heat from the first chamber into the second chamber when an indication that the door of the first chamber is to be opened is not received. In this case, the voltage applied across the thermoelectric module may be controlled to draw heat from the second chamber into the first chamber when an indication that the door of the first chamber is to be opened is received. Alternatively in this 10 case, the voltage applied across the thermoelectric module may be switched off when an indication that the door of the first chamber is to be opened is received.

10051 A third chamber may be defined by the housing, the third chamber being thermally insulated from the first chamber, and being in thermal communication with the second chamber by means of a second thermoelectric module.

10061 The second chamber may be in thermal communication with the external environment by means of a third thermoelectric module.

Brief description of the drawings

10071 The invention will be described, by way of example only, with reference to the following drawings: 10081 Figure 1 depicts a heating and cooling unit according to a first embodiment of the invention.

10091 Figure 2 depicts a heating, cooling and freezing unit according to a second embodiment of the invention.

Detailed description

10101 In general terms, the invention provides a chamber which is heated or cooled in any conventional manner, and an adjacent or otherwise thermally coupled thermal reserve in the form of a scaled reservoir of thermal energy. In particular, the chamber and the thermal reserve are in thermal communication by means of thermoelectric devices.

[0111 Thermoelectric devices (for example, Peltier or Seebeck devices) create a voltage when a temperature difference exists across its two opposing sides. When a voltage is applied to a thermoelectric device, it draws heat from a first side to the second side, the direction of heat transfer depending on the polarity of the voltage.

19121 The thermal reserve(s) may contain air. Alternatively, depending on the intended application, the thermal reserve may contain another gas, or a liquid, or a suitable solid material. In other embodiments, the thermal reserve(s) may contain a substance which changes phase between solid, liquid and gas across the intended range of operating temperatures and pressures. 'the material should be selected according to the required specific heat capacity. The optimal specific heat capacity will vary according to the application. Each thermal reserve may contain a plurality of different materials. In embodiments with more than one thermal reserve, some or each of them may contain different materials.

VA 3] When, for example, an indication is made that a user wishes to open the door of an oven which has been heated to a temperature greater than that of the external environment, a voltage is applied to the thermoelectric module coupling the oven to the thermal reserve such that heat is drawn from the oven into the thermal reserve, cooling the oven but storing the thermal energy already generated in or otherwise provided to the oven. The door can then be opened, with less energy lost, since the oven temperature has been reduced to be closer to, or the same as, the temperature of the external environment. In some embodiments, the energy will be reduced to below the external ambient temperature before the door is opened, in which case thermal energy from the external environment will be brought into the oven chamber. When the oven door is closed again, the polarity of the voltage applied to the thermoelectric module can be reversed, and heat transferred back from the thermal store to the oven. In this way, less heat needs to be newly generated or brought in from outside the system to get the oven back up to temperature.

10141 Since a temperature flux across a thermoelectric module creates a voltage 5 across the module as heat transfers from the warmer side to the cooler side so as to approach thermal equilibrium, in certain conditions the same result can be achieved without applying a voltage, but rather while generating electrical energy. For example, when heat is being transferred from the oven to the thermal reserve before the door is opened, and the time available means no accelerated transfer is required, any voltage applied to the thermoelectric module can be stopped, and the natural heat transfer will generate electricity in the thermoelectric module. In such embodiments, a voltage may need to be applied once thermal equilibrium is achieved between the oven and the thermal store if the thermal equilibrium temperature is higher than the external environment temperature, in order to reduce heat loss.

10151 Energy generated by this system can be used to power other heating elements, if they are used, other electrical loads, or stored in a battery or other energy storage system, or fed back to the grid.

10161 In some embodiments, the thermal reserve will itself be the principle source of heat for the oven, in which case, in order to raise the oven to the required temperature, a voltage is applied across the thermoelectric module to draw heat from the thermal reserve (cooling it) into the oven (heating it). This embodiment is particularly useful for the purposes of saving energy, since (apart from inevitable real-world losses) the electrical energy spent in heating the oven is partly regained when thermal equilibrium is restored before opening the door, by the generation of a voltage across the thermoelectric module by the natural transfer of heat. Furthermore, the state of thermal equilibrium reached in this case may be similar to the temperature of the external environment, so less energy will be lost when the door is opened.

10171 In all these embodiments, a voltage will need to be maintained across the thermoelectric coupling once there is a temperature difference between the oven and the thermal reserve, in order to maintain or increase the temperature difference. Future technological advances may reduce this requirement or even render it negligible.

10181 The same principles apply in reverse for a cooling system, such as a refrigerator. Heat can be drawn from the refrigerator into the thermal reserve, and/or by another cooling system, to reach a desired temperature. When an indication is received that the door is to be opened, thermal equilibrium can be allowed to return by removing the applied voltage across the thermoelectric module, or by applying a reversed voltage to the thermoelectric module. If cooling is achieved at least in part by means other than drawing heat into the thermal reserve, once thermal equilibrium is obtained a voltage may need to be applied to draw more heat from the thermal reserve in order to bring the refrigerator temperature closer to the external environment temperature. The voltage may also need to be applied to speed up the process of heat transfer. It may be preferable, in some embodiments, to brill-g the refrigerator chamber to a higher temperature than the external ambient temperature, so that thermal energy is lost to the environment when the door is opened, reducing the energy cost of cooling it again. This may not always be possible given time constraints, or desirable, depending on the function of the refrigerator chamber.

10191 The examples discussed so far have been an oven and a refrigerator. It will be apparent that the invention could be applied to many other systems. For example, the invention could be used for domestic or industrial cooling and/or heating, food and drink storage and preparation, food and drink display, hospital and laboratory equipment, the storage of medical equipment and medicines, incubators and coolers, temperature controlled transport of people, goods and equipment, and other portable applications.

[0201 Furthermore, the invention could be advantageous in embodiments with separate chambers for heating and cooling, linked by a thermal reserve. In such cases, heat could be drawn from a cooling chamber into the thermal reserve by the application of a voltage across a thermoelectric module coupling the two. Heat could be drawn from the thermal reserve into the heating chamber. Before a door opening event of either chamber, the heat could be transferred or allowed to return in the opposite direction, to or from the chamber about to be opened.

[0211 The embodiments above have been described with reference to an indication that a door is about to be opened. The invention could, additionally or alternatively, be controlled by a schedule of door opening events. An indication, if applicable to the embodiment, could include the pressing of a button, an unlocking action, sensor data indicating the approach of a user, or the stopping of a vehicle or proximity to a destination in mobile embodiments, or many other indications that will be apparent to the skilled person. An indication, including for the purposes of this specification a scheduled indication, should be made in time to give the preparatory heat transfer to occur to or from the chamber to be opened. In some embodiments, the door to the chamber could be automatically locked until the preparator heat transfer has occurred. An emergency lock release mechanism should be provided in such embodiments.

[0221 In other embodiments, the heating and/or cooling chamber could be openable without waiting for the heat transfer to or from the thermal reserve. This may be a useful option, for example, where the particular use of the chamber does not lend itself to being brought close to the external ambient temperature, such as the baking of a cake. It may also be useful on occasions when there is not enough time for the heat transfer to be made before the door is opened, or when the conservation of energy is not the primary consideration.

[23] The invention will now be described with reference to an embodiment depicted in Figure 1.

[24] Figure 1 depicts a unit 1 comprising an oven 2, a cooler 3, and a thermal reserve 4. The oven 2 is adjacent to the cooler 3, although this is not strictly necessary. The thermal reserve 4 is adjacent to both the oven 2 and the cooler 3, which is important, although not absolutely necessary; as will become apparent, what is absolutely necessary is that there is a path for heat transfer between the oven 2 and the thermal reserve 4, and between the cooler 3 and the thermal reserve 4.

[025] The oven is openable to the external environment by means of a door 5 which is depicted in a partially open configuration. The cooler is openable to the external environment by means of a drawer 6 which is depicted in the closed configuration. The thermal reserve is not openable to the external environment in ordinary use, although a maintenance hatch, for example, may be provided where appropriate, as long as proper thermal insulation provisions are made.

[26] All three chambers are housed in a housing 7, which must be thermally insulating. The chambers are separated by thermally insulating walls 8.

[27] A first thermoelectric module 9 is provided in the wall 8 separating the oven 2 from the thermal reserve 4. A second thermoelectric module 10 is provided in the wall 8 separating the cooler from the thermal reserve. The thermoelectric modules 9, 10 are preferably each connected to a switchable voltage source (not shown) so that a voltage can be applied in either direction across each of the thermoelectric modules, preferably independently. Appropriate control circuitry may be provided, depending on the intended use of the unit (not shown). If the voltage source(s) comprise mains power, appropriate conversion circuity will also be provided (not shown). If the voltage source(s) comprise a battery or other direct current power sources, step up Or step down conversion circuitry may be provided (not shown). If the voltage source(s) comprise a renewable or variable power source such as photovoltaic cells, maximum power point tracking circuitry and other conversion circuitry may be provided (not shown).

[0281 Some or all of the thermoelectric modules in any embodiment of the invention may be provided with fans, or other fluid impellers, on one or both sides. The fans or similar may be individually controllable, wherein the control may comprise activation and deactivation, or an increase or decrease in the rate of impelling, and reversal of direction. This can assist the heat transfer. In the figures, fans are depicted on both sides of all thermoelectric modules, but it will be apparent to the skilled person that this is not necessary.

[0291 Each thermoelectric module is connected to a heat sink on both sides. The number, size, shape and position of the heat sinks may vary according to the application, as may their mode of connection to the interior of their respective chambers and to the thermoelectric modules. In some embodiments the heat sinks may be hollow, to allow the passage of fluids through them, for example a fluid contained within a thermal reserve. They may be integral to the internal casing of their respective chambers. In some embodiments each heat sink may be made of a plurality of different materials. In other embodiments, no heat sinks are provided at all.

[030] Beginning from thermal equilibrium between the three chambers 2-4 and the external environment, with both doors 5, 6 closed, in order to heat the oven 2 and cool the cooler 3, a voltage is applied across the first thermoelectric module 9 with polarity to draw heat from the thermal reserve 4 into the heater (the direction of heat transfer is shown by arrow 11). A voltage is also applied across the second thermoelectric module 10, with polarity to draw heat from the cooler 3 to the thermal reserve 4 (the direction of heat transfer is shown by arrow 12).

l031I When an indication is made that the oven door 5 is to be opened, the voltage applied across the first thermoelectric module 9 is stopped, or its polarity is reversed. Both will have the effect of reversing the direction of heat transfer, from the oven 2 to the thermal reserve 4. Tf the applied voltage is stopped, a voltage will be created across the thermoelectric module 9 by the natural transfer of heat from the oven 2 to the thermal reserve 4. The electrical energy generated can be stored or used, as discussed above, if appropriate circuitry is provided. If the applied voltage is reversed, the heat transfer between the oven and the thermal reserve will be accelerated, and the final temperature in the oven 2 will be lower. The final temperature will be lower because, even ignoring ordinary real-world losses, thermal equilibrium between the oven 2 and the thermal reserve 4 in this embodiment will be reached at a higher temperature than that of the external environment, because heat has been added to the thermal reserve 4 by the second thermoelectric module 10, from the cooler 3. It will be apparent that both options (removing the applied voltage or reversing it have their advantages, the former retrieving some of the spent electrical energy from the thermal energy in the system, and the second losing less thermal energy when the oven door 5 is opened, since the temperature in the oven 2 will be closer to the temperature of the external environment. In some embodiments, where heat is actively drawn from the oven 2 by the application of a reversed polarity voltage across the thermoelectric module 2, the temperature in the oven 2 can be brought below the external ambient temperature, in order to draw heat from the external environment when the oven door 5 is opened. As a final step, the oven door 5 is opened for whatever purpose, and the oven 2 approaches thermal equilibrium with the external environment until the oven door 5 is closed again. If the oven 2 is still to be heated after the door 5 is closed, the voltage across the first thermoelectric module 9 is restored to its original polarity, indicated by arrow 11.

[032] It will be apparent that the same principle applies if an indication is made that the cooler door 6 is to be opened. Heat will be transferred from the thermal reserve 4 to the cooler 3, either by stopping the voltage applied to the second thermoelectric module 10, or by reversing its polarity. The applied voltage will be restored to its original polarity 12 if the cooler 3 continues in use after the door 6 is dosed again. Depending on the time available, and the use to which the cooler is put, the heat transfer in preparation for opening the cooler will either be to a temperature closer to but still lower than the external ambient temperature, substantially the same as the external ambient temperature, or higher than the external ambient temperature.

L0331 Figure 2 depicts a second embodiment in the form of a second unit 13 having two ovens 14, 15, a refrigerator 16, and a freezer compartment 17. For example, the oven compartments 14, 15 could be configured to operate with internal temperatures up to and/or greater than 200 degrees, while the refrigerator 16 operates at an internal temperature of 4 degrees and the freezer compartment 17 operates at a temperature of -18 degrees. Two thermal reserves 18, 19 are provided. The first thermal reserve 18 is adjacent to both oven compartments 14, 15 and both cooling compartments 16, 17. The second thermal reserve 19 is adjacent to the first oven 14, which in this embodiment is larger and needs more heat energy to maintain a given internal temperature. It is advantageous to provide a smaller oven, itzter alia because it costs less energy to get a smaller oven to a given temperature than it takes to get a larger oven to the same temperature.

10341 In some embodiments comprising at least one heating chamber and at least one cooling chamber, it may be the case that some of the chambers are temperature controlled most of the time, and other chambers are only temperature controlled occasionally One example of this is a unit comprising a refrigerator, in constant use for storing perishable goods, and an oven, used occasionally for cooking food. Another example is a super-freeze chamber for occasional highspeed cooling, and a furnace in constant use.

10351 Although it is not necessary, it is likely to be convenient to configure the unit 13 such that at least one oven compartment 15 is adjacent to either the refrigerator 16 or the freezer 17. In this case, it is useful to have extra insulation 20 separating these compartments.

[036] Several specific configurations of heating and/or cooling devices are disclosed by way of example in this specification. It will be apparent to the skilled person that any configuration of heating and/or cooling chambers and thermal reserves can be used with this invention, including configurations with differently sized chambers and different numbers of chambers. Tt may be advantageous, for example, to have a large thermal reserve chamber and a smaller heating chamber, in order to reduce the energy required in drawing thermal energy from the thermal reserve to the heating chamber to achieve a desired temperature in the heating chamber. Similarly, it may be advantageous to have a larger cooling chamber in a joint heating and cooling system. It may be advantageous in some embodiments to have a plurality of thermal reserves, for example a thermal reserve coupled to the cooling chamber(s) and a separate thermal reserve coupled to the heating chamber(s).

[0371 Each heating and cooling compartment 14-17 is in thermal communication with the first thermal reserve 18 by means of a respective thermoelectric module 21-24. The first thermal reserve 18 is in thermal communication with the second thermal reserve 19 by means of a fifth thermoelectric module 25. The second thermal reserve is in thermal communication with the external environment by means of a sixth thermoelectric module 26. The second thermal reserve 19 is in thermal communication with the first oven 14 by means of a seventh thermoelectric module 27. Although it is not shown, controller circuitry and power circuitry is provided so that a switchable voltage can be applied across each of the thermoelectric modules independently. A compartment 28 may be provided for housing control circuitry and power storage. The control circuitry may receive temperature signals from each of the chambers 14-17 and the thermal reserves 18, 19, for example from thermometers 33 disposed throughout the unit. The control of the system may be based, at least in part, on the temperature readings provided by the thermometers 33.

[38] All embodiments preferably include a user interface (not shown). As well as providing means for providing an indication that a chamber is about to be opened, the user interface will provide more conventional controls, such as temperature controls for each chamber, scheduling controls, and any other necessary or useful inputs.

[39] The second thermal reserve can draw heat from the external environment by means of the sixth thermoelectric module 26. This can provide additional thermal energy when this is needed to heat first oven 14, by means of seventh thermoelectric module 27. Alternatively, it can provide thermal energy to the first thermal reserve 18 by means of fifth thermoelectric module 25. If the thermal reserves 18, 19 overheat, thermal energy can be expelled through the sixth thermoelectric module 26 to the external environment.

[40] The compartments 14-17 are heated and cooled in the same way as the compartments in the first embodiment.

[041] I ';ach of the ovens 14, 15 and coolers 16, 17 is openable to the external environment by means of a respective door or drawer 29-32. Each door or drawer is shown in a partially open configuration. It will be clear to the skilled person that the chambers can be openable by any prior art means, according to the intended use of the particular embodiment.

[042] When an indication is made that one of the doors 29-32 is to be opened, the voltages applied across the appropriate thermoelectric modules 21-27 are stopped or reversed, as described above.

[043] It will be apparent that the same principles apply when an indication is made that more than one door is to be opened at the same time. In such a case, all of the appropriate thermoelectric modules 21-27 are controlled at the same time, to cause the compartments about to be opened to approach, attain, or pass thermal equilibrium with the external environment before they are opened.

[44] Although the invention has been described according to certain embodiments, these embodiments are not limiting The scope of the invention is limited only by the claims.

[45] The skilled person will readily envisage a wide variety of embodiments for 5 the invention, including incorporation into otherwise conventional systems, for example, ovens, refrigerators industrial cooling units and furnaces.

[46] The environmental benefits of the invention will be clear to the skilled reader. I 'imbodiments of this invention waste less energy, and require less input energy for the generation of or removal of heat. Some embodiments of the 10 invention generate electrical energy through heat flux.

Claims

Claims 1. An apparatus comprising a thermally insulated housing defining a first chamber and a second chamber, the first chamber comprising a door openable to the external environment, the first chamber being in thermal communication with 5 the second chamber by means of a thermoelectric module; the apparatus further comprising: an electrical power supply connected to the thermoelectric module in such a way that a voltage applied across the thermoelectric module can be switched on and off with either polarity; and a controller configured to receive an indication that the door of the first chamber is to be opened; wherein the voltage applied 10 across the thermoelectric module is controlled according to whether or not an indication that the door of the first chamber is to be opened has been received.
2. An apparatus according to claim 1 wherein the indication that the door of the first chamber is to be opened comprises at least one of: a schedule of door opening events; the pressing of a button; an unlocking action; sensor data indicating the approach of a user; the stopping of a vehicle transporting the apparatus; or proximity of the apparatus to a destination
3. An apparatus according to claim 1 or claim 2, wherein the voltage applied across the thermoelectric module is controlled such that the thermoelectric module draws heat from the second chamber into the first chamber when an indication 20 that the door of the first chamber is to be opened is not received.
4. An apparatus according to claim 3, wherein the voltage applied across the thermoelectric module is controlled such that the thermoelectric module draws heat from the first chamber into the second chamber when an indication that the door of the first chamber is to be opened is received.
5. An apparatus according to claim 3, wherein the voltage applied across the thermoelectric module is switched off when an indication that the door of the first chamber is to be opened is received.
6. An apparatus according to claim 1 or claim 2, wherein the voltage applied 5 across the thermoelectric module is controlled to draw heat from the first chamber into the second chamber when an indication that the door of the first chamber is to be opened is not received.
7. An apparatus according to claim 6, wherein the voltage applied across the thermoelectric module is controlled to draw heat from the second chamber into 10 the first chamber when an indication that the door of the first chamber is to be opened is received.
8. An apparatus according to claim 6, wherein the voltage applied across the thermoelectric module is switched off when an indication that the door of the first chamber is to be opened is received.
9. An apparatus according to claim 5 or claim 8, further comprising an electrical load, wherein the electrical load is connected to the thermoelectric module when the voltage applied across the thermoelectric module is switched off
10. An apparatus according to claim 9, wherein the electrical load is an electrical energy store.
11. An apparatus according to any preceding claim, wherein a third chamber is defined by the housing, the third chamber being thermally insulated from the first chamber, and being in thermal communication with the second chamber by means of a second thermoelectric module.
12. An apparatus according to any preceding claim, wherein the second chamber is in thermal communication with the external environment by means of a third thermoelectric module.