A system for storing and transferring heat

Abstract

The invention relates to a system for storing and transferring heat comprising at least one vessel unit having a first inner heat storage vessel for storing heat and a second outer vessel surrounding the first inner vessel, wherein between the first inner vessel and the second outer vessel a thermal insulation space is provided. The invention also relates to an on-site generation structure for energy storage and transfer comprising the system for storing and transferring heat. The invention further relates to a method for storing and transferring heat.

Description

[0001] Title: A system for storing and transferring heat

[0002] Description:

[0003] The invention relates to a system for storing and transferring heat.

[0004] The invention also relates to an on-site generation structure for energy storage and transfer comprising a system of this disclosure.

[0005] The invention further relates to a method for storing and transferring heat.

[0006] Systems for generating sustainable energy have the disadvantage that the amount of electricity produced and the timing of the production vary greatly. The fluctuating nature of renewable energy have among others led to the development of various storage technologies to help store surplus or cost-effective energy and discharge that stored energy at a different moment in time. Thermal storage requires a heat storage in which thermal energy is stored via a change in temperature (only). Hot water storage is for example one of the most popular types of heat stores. An example of a double wall water tank with a heat exchanger and a vacuum pump to store heat is disclosed in DE 10 2009 056 693 A1. In this double wall water tank heat is stored in the water inside the inner water tank by means of the heat exchanger and the heated water can be discharged from the inner tank at a different moment in time. A drawback of this system is that water (energy) discharge goes together with a relatively cold water supply which means that water (energy) discharge from the water tank has a relatively strong impact on the total energy stored in the tank. Hence, if the energy demand is relatively high and energy input is relatively low, the double wall water tank will run out of energy in a relatively short period of time. In addition, the maximum temperature of water is relatively low under atmospheric pressure conditions.

[0007] It is an object of the present invention to provide an improved system for storing and transferring heat, for example an improved system in which heat energy can be stored for a relatively long period with reduced loss of energy and / or transferred with reduced loss of energy.

[0008] The above object is achieved with a system as defined in claim 1.

[0009] The system for storing and transferring heat comprises:

[0010] - at least one vessel unit having a first inner heat storage vessel for storing heat and a second outer vessel surrounding the first inner vessel, wherein between the first inner vessel and the second outer vessel a thermal insulation space is provided;

[0011] - a vacuum pump configured to provide at least a partial vacuum in the thermal insulation space;

[0012] - a heat transfer mechanism configured to be brought in fluid communication with the thermal insulation space for transferring heat out of the at least one vessel unit.

[0013] By means of this system it is possible to store energy, in particular heat, for a relatively long period of time. By storing energy in the system in the summer, where there is normally a surplus of energy, for example provided by solar panels, a solar thermal collector or other sustainable energy sources, and / or at times where energy is relatively cost friendly, the system is configured to provide minimal energy storage loss for a relatively long time, such as weeks or even months, by using vacuum technology. Vacuum technology is used in the system to engineer high-performance thermal insulation to prevent conductive and convective heat transfer, i.e. to reduce heat loss from the first inner heat storage by providing a vacuum or at least a partial vacuum of for example 50-10000 Pa. At times, for example the winter period, where the costs of energy are higher, the system further has an improved configuration to transfer the energy, in particular heat, out of the system. The system is configured to transfer heat in a relatively efficient manner out of the system with a relatively low impact on the total heat energy stored in the system. This configuration ensures that heat is not directly transferred from the first inner heat storage vessel, but instead indirectly by using the heat transfer mechanism which is configured to be brought in fluid communication with the thermal insulation space between the first inner vessel and the second outer vessel for transferring heat out of the at least one vessel unit. In this manner an improved system for storing and transferring heat is obtained, wherein in periods of no or minimal heat transfer a maximal insulation with vacuum technology can be obtained, wherein in periods with heat transfer out of the system, the impact of energy transfer on the total heat energy stored in the system can be reduced.

[0014] The heat transfer mechanism comprises a heat exchanger.

[0015] In one aspect, the thermal insulation space has at least one port, wherein the vacuum pump and the heat exchanger are in fluid communication with the thermal insulation space by means of the at least one port. The at least one port may be used by means of the vacuum pump and the heat transfer mechanism sequentially or simultaneously. In such an embodiment, the vacuum pump is in fluid communication with the thermal insulation space by means of the port(s) and the heat exchanger of the heat transfer mechanism is in fluid communication with the thermal insulation space by means of the same port(s). In this embodiment the vacuum pump can be used to transfer heat from the thermal insulation space to the heat transfer mechanism in an efficient manner and simultaneously lower the pressure in the thermal insulation space by means of the vacuum pump. By arranging the heat transfer mechanism, in particular the heat exchanger of the heat transfer mechanism, between the vacuum pump and the thermal insulation space, in particular the at least one port associated to the thermal insulation space, the gas temperature for the vacuum pump can be controlled by means of the heat transfer mechanism, such that the vacuum pump can be protected against relatively high temperatures such that the lifespan of the vacuum pump can be extended and / or maintenance work can be more limited. The system may further comprise at least one fluid inlet. The at least one fluid inlet is adapted to be closed in a first operating mode, such as an insulation operating mode of the system, and adapted to be opened in a second operating mode, such as a heat transfer operating mode of the system. In an open state, the at least one fluid inlet provides an external inflow of gas, for example ambient air, into the thermal insulation space, wherein in use the gas can be heated by means of the first inner heat storage vessel. In one aspect, the at least one fluid inlet and the at least one port are arranged in the vessel unit at a distance from each other such that it is possible to provide a flow there between in the thermal insulation space. For example, the at least one fluid inlet may be located in or close to the top of the vessel unit and the at least one port may be located in or close the bottom of the vessel unit, or, alternatively, the at least one fluid inlet is arranged at an opposite side of the vessel unit with respect to the at least one port.

[0016] It is possible to use a liquid, for example water, in the first inner heat storage vessel to store energy. Solid material in the first inner heat storage vessel to store energy for long term heat storage is more preferred from efficiency and safety perspective, in particular solid materials having no phase change in temperature ranges between 100-1000 degrees . The solid material may be capable to be heated to a temperature between 150-1000°C, preferably between 250-750°C, without significant chemical reactions or melting. The solid material is a stationary heat storage medium. Solid storage material may include natural rocks, sandstone, granite, sand, salts, oxides ceramics, castable cements, concrete, basalt, steel slag or elements such as carbon / graphite, silicon, or iron. It is also possible to use mixtures of the mentioned solid materials.

[0017] It is further an object of the present invention to provide an improved method system for storing and transferring heat, for example an improved method for storing heat energy for a relatively long period with reduced loss of energy and / or transferred with reduced loss of energy.

[0018] This object is achieved with the included method claim. The method for storing and transferring heat comprises the following steps:

[0019] A- storing heat in a first inner heat storage vessel;

[0020] B- providing at least a partial vacuum in a thermal insulation space between the first inner heat storage vessel and a second outer vessel surrounding the first inner vessel;

[0021] C- transferring heat from the first inner heat storage vessel by means of providing a fluid communication between the thermal insulation space and a heat transfer mechanism.

[0022] For purposes of convenience and brevity, reference is made to the abovedescribed device for corresponding advantages of the method of this disclosure.

[0023] In one aspect of the method, gas, for example ambient air, is introduced in the thermal insulation space before and / or simultaneously with step C. By means of the introduction of gas into thermal insulation space an improved and / or more optimal heat transfer by means of step C may be achieved. From insulation perspective the time window for introducing gas like ambient air is chosen relatively short under normal working conditions of the system of this disclosure. The introduction of gas into thermal insulation space may start on or before step C and may end after the heat transfer step c has started. The introduction of gas may end as step C ends. Step C may be performed by using the vacuum pump which is used in step B. The method of this disclosure comprises an insulation operating mode and a heat transfer operating mode, wherein in the insulation operating mode step B is being performed without step C, wherein in the heat transfer operating mode at least step C is being performed. The aspects described above as well as other aspects of the system and the method will be explained hereunder on the basis of an exemplary embodiment in combination with figures. The invention is not, however, limited to the exemplary embodiments described hereunder. Rather, a number of adaptations and modifications are possible, which also make use of the idea of the invention claimed in the claims and consequently fall within the scope of protection. In particular, the possibility is mentioned of combining the features / aspects that are only mentioned in the description and / or are shown in the figures, with the features of the claims in so far as compatible.

[0024] Brief description of the drawings:

[0025] Figure 1 shows in a diagrammatic manner a system for storing and transferring heat;

[0026] Figure 2 shows in a diagrammatic manner another embodiment of a system for storing and transferring heat;

[0027] Figure 3 shows in a diagrammatic manner a further embodiment of a system for storing and transferring heat;

[0028] Figure 4 shows a flow chart of a method of this disclosure for storing and transferring heat.

[0029] In the following description identical or corresponding parts have identical or corresponding reference numerals. Each feature disclosed with reference to a specific figure can also be combined with another feature disclosed in this disclosure, unless it is evident for a person skilled in the art that these features are incompatible.

[0030] Detailed description of the drawings:

[0031] Figures 1-3 show a system 1 ; 101 ; 201 for storing and transferring heat. The system 1 ; 101 ; 201 comprises:

[0032] - at least one vessel unit 10 having a first inner heat storage vessel 3 for storing heat and a second outer vessel 5 surrounding the first inner vessel 3, wherein between the first inner vessel 3 and the second outer vessel 5 a thermal insulation space 7 is provided;

[0033] - a vacuum pump 9 configured to provide at least a partial vacuum in the thermal insulation space 7; - a heat transfer mechanism 11 configured to be brought in fluid communication with the thermal insulation space 7 for transferring heat out of the at least one vessel unit 10.

[0034] The first inner heat storage vessel 3 is adapted for solid material for storing heat energy and comprises solid material (not shown) for storing heat energy, wherein the solid material in the first inner heat storage vessel 3 is capable to be heated to a temperature between 150-1000°C, preferably between 250-750°C, without significant chemical reactions or melting.

[0035] The systems 1 ; 201 as shown in figures 1 and 3 differ from the system 101 shown in figure 2 in that the system 101 comprises one or more radiation shields indicated by dotted lines 113 arranged in the thermal insulation space 7. It is possible to use radiation shields 113 also in the system 201.

[0036] In the embodiment shown the radiation shields 113 surround the first inner heat storage vessel 3. Other configurations of the radiation shields are possible, such as for example multiple parallel extending radiation shields or radiation shields arranged and extending in the longest dimension of the vessel unit 10. The radiation shields 113 are arranged at a distance from an outer wall of the first inner heat storage vessel 3. The radiation shields 113 may be arranged between the outer wall of the first inner heat storage vessel 3 and an inner wall of the second outer vessel 5, for example at a distance in a range of 10-90% of the total distance between the outer wall of the first inner heat storage vessel 3 and an inner wall of the second outer vessel 5. The shield 113 may comprise a single layer or a multi-layer, wherein at least one layer is made from an appropriate metal or alloy, in particular aluminium or an aluminium alloy, or stainless steel or a steel alloy.

[0037] The systems 1 ; 101 as shown in figures 1 and 2 differ from the system 201 as shown in figure 3 in that an energy introduction unit 15 of the system 1 ; 101 for storing heat energy in the first inner heat storage vessel 3 is configured for electricity or electrical energy conversion into heat, whereas the system 201 comprises an energy introduction unit 215 with a different configuration, i.e. the energy introduction unit 215 is configured for fluid or fluid heat transfer.

[0038] The energy introduction unit 215 of the system 201 stores heat energy in the first inner heat storage vessel 3 of the at least one vessel unit 10 by a fluid provided to the first inner heat storage vessel 3. The energy introduction unit 215 comprises a pump mechanism 216, a fluid supply line 218, a fluid discharge line 220 and in the first inner heat storage vessel 3 a heat transfer arrangement 222 for exchanging / transferring the heat of the fluid supplied by the fluid supply line 218 into the solid material in the first inner heat storage vessel 3. The fluid to be supplied to the first inner heat storage vessel 3 by means of the pump mechanism 216 is for example a liquid heated by a solar thermal collector (not shown).

[0039] The energy introduction unit 15 of the system 1 ; 101 for storing heat energy in the first inner heat storage vessel 3 comprises an electrical network 17 and in the first inner heat storage vessel 3 a heat transfer arrangement 22, for example heated element(s) to be heated with electricity from the electrical network 17 for heating the solid material in the first inner heat storage vessel 3. The electrical network 17 is for example connected or connectable to solar panels (not shown) as a power source.

[0040] By means of the heat transfer mechanism 11 heat energy is transferred from the system 1 ; 101 ; 201 , for example to a conventional heating system for buildings or other energy heat demanding appliances or converted to other forms such as mechanical work or electricity. The heat transfer mechanism 11 is, or comprises, a heat exchanger which is arranged externally to the at least one vessel unit 10.

[0041] As shown in figures 1-3 the thermal insulation space 7 is defined between the first inner heat storage vessel 3 and a vessel wall 6 of the second outer vessel 5. The thermal insulation space 7 has at least one port 25, wherein the vacuum pump 9 and the heat transfer mechanism 11 are in fluid communication with the thermal insulation space 7 by means of the at least one port 25. The at least one port 25 is arranged in the vessel wall 6 of the second outer vessel 5 as shown in figures 1-3. The heat transfer mechanism 11 , in particular its heat exchanger, is arranged between the vacuum pump 9 and the thermal insulation space 7, in particular the port 25. The heat transfer mechanism 11 is configured to control the temperature of gas supplied to the vacuum pump 9 from the thermal insulation space 7, wherein at the same time heat energy can be transferred from the system 1 ; 101 ; 201 by means of the heat transfer mechanism 11. The system 1 ; 101 ; 201 further comprises at least one fluid inlet 27 which is adapted to be closed in a first operating mode, such as an insulation operating mode of the system, and adapted to be opened in a second operating mode, such as a heat transfer operating mode of the system. In the heat transfer operating mode heat energy is transferred out the system 1 ; 101 ; 201 by means of the heat transfer mechanism 11. Although not shown it is also possible to provide the system 1 ; 101 ; 201 without a fluid inlet 27. The heat transfer mechanism 11 may be configured to open the port 25 for introducing a gas, such as ambient air, into the thermal insulation space 7.

[0042] The system 1 ; 101 ; 201 comprises at least one controller 50 configured for:

[0043] - switching the at least one fluid inlet 27 between the first operating mode and the second operating mode; and / or

[0044] - operating the vacuum pump 9; and / or

[0045] - operating heat transfer mechanism 11 ; and / or

[0046] - operating the energy introduction unit 15; 215.

[0047] The controller 50 is not shown in figure 2, but the controller 50 is present in the system 101 like the controller 50 shown in figure 1.

[0048] Further, this disclosure relates to an on-site generation structure for energy generation, storage and transfer comprising the system 1 : 101 ; 201 for storing and transferring heat of this disclosure. Onsite generation is the production of energy at or near the point of use. It is “decentralised energy” which enables a business or one or a couple of households to make and use its own generated energy, rather than buying that energy through the grid. In the on-site generation structure of this disclosure renewable energy is generated, for example by solar panels, solar thermal collectors and / or other sustainable energy sources, wherein the generated energy is provided to the system of this disclosure for storage and transfer. On-site generation structure may be used to store renewable energy by means of heat energy, wherein the heat energy is used / transferred at a different moment. The on-site generation structure may be for example used to store renewable energy between seasons. The dimensions of the vessel unit 10 in an on-site generation structure will between a height of 2-10 meter, such as a height of 4-6 meter and a diameter between 1-5 meter, such as 1 ,5- 3 meter. In other applications than in an on-site generation structure different dimensions of the vessel unit 10, i.e. most likely larger dimensions, will be used.

[0049] Figure 4 shows a flow chart of the method steps for storing and transferring heat, for example by using the system of this disclosure, the method comprising the following steps:

[0050] A- storing heat in a first inner heat storage vessel 3; B- providing at least a partial vacuum by means of the vacuum pump 9 in a thermal insulation space 7 between the first inner heat storage vessel 3 and a second outer vessel 5 surrounding the first inner vessel 3;

[0051] C- transferring heat from the first inner heat storage vessel 3 by means of providing a fluid communication between the thermal insulation space 7 and a heat transfer mechanism 11 by means of the vacuum pump 9.

[0052] By means of the method of this disclosure maximal insulation can be obtained by using vacuum technology and the impact of the energy transfer (step C) on the total energy stored in the first inner heat storage vessel 3 is reduced by transferring the heat indirect by means of the thermal insulation space. The components and functions of the system 1 : 101 : 201 as described above can also be applied on the method of this disclosure. For example, the first inner vessel 3 and the second outer vessel 5 provide the at least one vessel unit 10 as shown in Figs 1-3.

[0053] Before and / or simultaneously with step C gas, for example ambient air, may be introduced in the thermal insulation space.

[0054] In an insulation operating mode of the method step B is being performed without step C, wherein in a heat transfer operating mode of the method at least step C is being performed.

[0055] The first inner heat storage vessel may comprise solid material for storing heat energy. In step A solid material may be heated to a temperature between 150-1000°C, preferably between 250-750°C, without significant chemical reactions or melting.

[0056] The system (not shown) may also comprise multiple vessel units 10.

Claims

CLAIMS1. A system for storing and transferring heat comprising:- at least one vessel unit having a first inner heat storage vessel for storing heat and a second outer vessel surrounding the first inner vessel, wherein between the first inner vessel and the second outer vessel a thermal insulation space is provided;- a vacuum pump configured to provide at least a partial vacuum in the thermal insulation space;- a heat transfer mechanism configured to be brought in fluid communication with the thermal insulation space for transferring heat out of the at least one vessel unit, wherein the heat transfer mechanism comprises a heat exchanger, wherein the thermal insulation space has at least one port, wherein the vacuum pump and the heat exchanger are in fluid communication with the thermal insulation space by means of the at least one port.

2. The system according to claim 1 , wherein the heat transfer mechanism is configured to open the port for introducing a gas, such as ambient air, into the thermal insulation space.

3. The system according to claim 1 or 2, wherein the system comprises at least one fluid inlet which is adapted to be closed in a first operating mode, such as an insulation operating mode of the system, and adapted to be opened in a second operating mode, such as a heat transfer operating mode of the system.

4. The system according to any of the preceding claims, wherein the heat exchanger is arranged between the vacuum pump and the thermal insulation space.

5. The system according to any of the preceding claims, wherein the heat transfer mechanism is configured to control the temperature of gas supplied to the vacuum pump from the thermal insulation space.

6. The system according to any of the preceding claims, wherein the first inner heat storage vessel is configured for receiving solid material for storing heat energy.

7. The system according to claim 6, wherein the solid material in the first inner heat storage vessel is capable to be heated to a temperature between 150-1000°C, preferably between 250-750°C, without significant chemical reactions or melting.

8. The system according to any of the preceding claims, wherein the system further comprises an energy introduction unit for storing heat energy in the first inner heat storage vessel of the at least one vessel unit, for example by converting electrical energy into heat energy and / or by a fluid provided to the first inner heat storage vessel9. The system according to any of the preceding claims, wherein the system comprises at least one controller configured for:- switching the at least one fluid inlet between the first operating mode and the second operating mode; and / or- operating the vacuum pump; and / or- operating heat transfer mechanism; and / or- operating the energy introduction unit.

10. The system according to any of the preceding claims, wherein the system comprises one or more radiation shields arranged in the thermal insulation space, preferably at a distance from an outer wall of the first inner heat storage vessel.

11. The system according to any of the preceding claims, wherein the a heat exchanger is arranged externally to the at least one vessel unit.

12. An on-site generation structure for energy storage and transfer comprising a system according to any of the preceding claims.

13. A method for storing and transferring heat comprising the following steps:A- storing heat in a first inner heat storage vessel;B- providing at least a partial vacuum by means of a vacuum pump in a thermal insulation space between the first inner heat storage vessel and a second outer vessel surrounding the first inner vessel;C- transferring heat from the first inner heat storage vessel by means of providing a fluid communication between the thermal insulation space and a heat transfer mechanism by means of the vacuum pump.

14. The method according to claim 13, wherein before and / or simultaneously with step C gas, for example ambient air, is introduced in the thermal insulation space.

15. The method according to claim 13 or 14, wherein the method comprises an insulation operating mode and a heat transfer operating mode, wherein in the insulation operating mode step B is being performed without step C, wherein in the heat transfer operating mode at least step C is being performed.

16. The method according to any of the preceding claims 13-15, wherein the first inner heat storage vessel comprises solid material for storing heat energy, wherein the solid material is heated to a temperature between 150-1000°C, preferably between 250-750°C, without significant chemical reactions or melting.

Images