Energy storage device

Abstract

This invention relates to a chemisorption based energy storage device, able to provide electricity, heating or cooling depending on the desired energy output. The device typically comprises sorbent materials which have an affinity for a refrigerant gas at different temperatures.

Claims

1. A chemisorption based energy storage device comprising: a first chemical reactor containing a first sorbent material and a second chemical reactor containing a second sorbent material different from the first sorbent material, the first sorbent material having an affinity towards a refrigerant gas at a high temperature and the second sorbent material having an affinity towards the refrigerant gas at a low temperature, the first and second chemical reactors being further provided with means for putting heat in to, or taking heat out of, the first and/or the second sorbent materials; a compressor/expander module selectively connected to the first and second chemical reactors, the compressor/expander module being configured to either compress or expand the refrigerant; wherein the means for putting heat in to, or taking heat out of, the first and/or the second sorbent materials provides a flow of refrigerant between the compressor/expander module and the first and second chemical reactors, and wherein the compressor/expander module is operable to compress or expand the refrigerant depending on energy storage requirements.

2. The device according to claim 1, wherein the refrigerant is ammonia.

3. The device according to claim 1, wherein the refrigerant is methanol.

4. The device according to claim 1, wherein the refrigerant is steam.

5. The device according to claim 1, wherein the first sorbent material is a salt selected from a metal halide, a metal sulphide and a metal sulphate.

6. The device according to claim 5, wherein the first sorbent material is a salt selected from the group: NiCl.sub.2, CaCl.sub.2, MgCl.sub.2, MgSO.sub.4 and MnCl.sub.2.

7. The device according to claim 1, wherein the second sorbent material is a salt selected from a metal halide, a metal sulphide and a metal sulphate.

8. The device according to claim 7, wherein the salt is selected from the group: CaCl.sub.2, SrCl.sub.2, BaCl.sub.2 and NaBr.

9. The device according to claim 1, wherein the first sorbent material and/or the second sorbent material is porous.

10. The device according to claim 1, wherein a valve is provided to provide selective connection to the compressor/expander module.

11. A method of operating a chemisorption based energy storage device to store energy, the device comprising: a first chemical reactor containing a first sorbent material and a second chemical reactor containing a second sorbent material, the first sorbent material having an affinity towards a refrigerant gas at high temperature and the second sorbent material having an affinity towards the refrigerant gas at low temperature, the first and second chemical reactors being further provided with means for putting heat in to, or taking heat out of, the first and second chemical reactors and a compressor/expander module selectively connected to the first and second chemical reactors, the compressor/expander module being configured to either compress or expand the refrigerant, the method comprising: heating the first chemical reactor to release refrigerant gas from the first sorbent material; compressing the refrigerant gas released from the first chemical reactor; and entraining compressed refrigerant gas to the second chemical reactor, the compressed refrigerant gas adsorbing onto the second sorbent material.

12. A method of operating a chemisorption based energy storage device to store energy, the device comprising: a first chemical reactor containing a first sorbent material and a second chemical reactor containing a second sorbent material, the first sorbent material having an affinity towards a refrigerant gas at high temperature and the second sorbent material having an affinity towards the refrigerant gas at low temperature, the first and second chemical reactors being further provided with means for putting heat in to, or taking heat out of, the first and second chemical reactors and a compressor/expander module selectively connected to the first and second chemical reactors, the compressor/expander module being configured to either compress or expand the refrigerant, the method comprising: heating the first chemical reactor to release refrigerant gas from the first sorbent material; expanding the refrigerant gas released from the first chemical reactor; and entraining refrigerant gas to the second chemical reactor, the refrigerant gas adsorbing onto the second sorbent material.

13. A method of operating a chemisorption based energy storage device to store energy and generate electric power and refrigeration, the device comprising: a first chemical reactor containing a first sorbent material and a second chemical reactor containing a second sorbent material, the first sorbent material having an affinity towards a refrigerant gas at high temperature and the second sorbent material having an affinity towards the refrigerant gas at low temperature, the first and second chemical reactors being further provided with means for putting heat in to, or taking heat out of, the first and second chemical reactors and a compressor/expander module selectively connected to the first and second chemical reactors, the compressor/expander module being configured to either compress or expand the refrigerant, the method comprising: heating the second chemical reactor to release a high pressure refrigerant gas; entraining the high pressure refrigerant gas to the compressor/expander module; expanding the high pressure refrigerant gas to produce electricity and an exhausted refrigerant gas; and entraining the exhausted refrigerant gas to the first chemical reactor for adsorption onto the first sorbent material.

14. A method of operating a chemisorption based energy storage device to store energy and generate heat, the device comprising: a first chemical reactor containing a first sorbent material and a second chemical reactor containing a second sorbent material, the first sorbent material having an affinity towards a refrigerant gas at high temperature and the second sorbent material having an affinity towards the refrigerant gas at low temperature, the first and second chemical reactors being further provided with means for putting heat in to, or taking heat out of, the first and second chemical reactors and a compressor/expander module selectively connected to the first and second chemical reactors, the compressor/expander module being configured to either compress or expand the refrigerant, the method comprising: heating the second chemical reactor to release a high pressure refrigerant gas; and entraining the high pressure refrigerant gas directly to the first chemical reactor causing the high pressure refrigerant gas to adsorb onto the first sorbent material to provide heat.

15. A method of operating a chemisorption based energy storage device to store energy and generate refrigeration, the device comprising: a first chemical reactor containing a first sorbent material and a second chemical reactor containing a second sorbent material, the first sorbent material having an affinity towards a refrigerant gas at high temperature and the second sorbent material having an affinity towards the refrigerant gas at low temperature, the first and second chemical reactors being further provided with means for putting heat in to, or taking heat out of, the first and second chemical reactors and a compressor/expander module selectively connected to the first and second chemical reactors, the compressor/expander module being configured to either compress or expand the refrigerant, the method comprising: extracting heat from an external source and directing that heat to the second chemical reactor causing release of refrigerant gas from the second sorbent material; and entraining the refrigerant gas directly to the first chemical reactor wherein the refrigerant gas is adsorbed onto the first sorbent material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

(2) FIG. 1 is a schematic of the system. Inset 1 shows the first step of compression; inset 2a shows the second step of expansion for power generation; inset 2b shows the second step of producing heat; and inset 2c shows the second step of producing cooling.

DETAILED DESCRIPTION

(3) First sorbent material may be in the form of a high temperature salt adsorbent bed in a vessel. Examples of appropriate adsorbent salts (particularly effective when the refrigerant is ammonia) are NiCl.sub.2, CaCl.sub.2, MgCl.sub.2, MgSO.sub.4 and MnCl.sub.2.

(4) The second sorbent material may be in the form of a low temperature salt adsorbent bed in a vessel. Examples of appropriate adsorbent (particularly effective when the refrigerant is ammonia) salt are CaCl.sub.2, SrCl.sub.2, BaCl.sub.2 and NaBr.

(5) Chemisorption is a form of adsorption which involves the formation of and breaking of chemical bonds (e.g. dative bonds) between an adsorbate (in this case the refrigerant gas) and a sorbent.

(6) The chemisorption storage system is capable of reproducing electricity or heating or cooling depending on different energy requirements. It promises greater flexibility comparable to flow batteries.

(7) Where a sorbent has an affinity for a refrigerant gas at a given temperature, the equilibrium between the gas being adsorbed (i.e. chemically bonded to the sorbent) and the gas not being adsorbed (i.e. not chemically bonded to the sorbent) at that temperature lies towards the gas being adsorbed.

(8) The terms high temperature and low temperature used in this specification are intended to be understood relative to each other.

(9) A single cycle of the energy storage device is composed of four main components: high temperature salt vessel (HTS adsorbent bed), low temperature salt vessel (LTS adsorbent bed), a compressor which can work in reverse as an expander, and a heat exchanger for releasing cold energy. The working principle of one complete cycle is made up of two steps. A compressor or expander may be located on separate loops as two separate components.

(10) In the first step, the energy storage system uses the off-peak period electricity to drive the compressor which pressurizes the ammonia released from HTS ammoniates, a-b shown in FIG. 1(1) represents the isentropic compression. The ammonia is stored in the form of LTS ammoniate impregnated in porous material at heat sink temperature, b-c shown in FIG. 1(1) which demonstrates isobaric cooling. Point c is the equilibrium state of LTS synthesis reaction.

(11) In the second step, the energy storage system may be operated in a number of ways in order to reproduce electricity, heating or cooling (refrigeration).

(12) To reproduce electric power generation and additional refrigeration, the LTS vessel is heated at 60 C. (as shown in FIG. 1(2a) by the path d). The LTS vessel releases high pressure ammonia which passes through the expander and produces electricity (as shown in FIG. 1(2a) by the path d). Afterwards, the exhausted ammonia is adsorbed by HTS vessel (FIG. 1(2a) by the path e-f).

(13) The ammonia vapour arrives at the inlet of the expander at low temperature but at high pressure and simultaneously, the HTS adsorbent downstream of the expander is at an extremely low equilibrium pressure; good performance of the expansion and large power outputs are achieved. The exhausted ammonia provides additional refrigeration.

(14) To produce heat, the LTS vessel is heated at 60 C. (FIG. 1(2b) shown by the path d-e) and the LTS vessel releases ammonia which is directly be adsorbed by the HTS vessel. A valve is provided connect the LTS vessel and the HTS vessel directly.

(15) A high temperature synthesis heat (d-e) is produced as shown in FIG. 1(2b).

(16) If high temperature sorbent material is NiCl.sub.2, heat at around 260 C. is released. Other sorbent materials such as MnCl.sub.2 produce heat at around 150 C. and CaCl.sub.2 produces heat at around 90 C.

(17) To produce refrigeration, the LTS vessel is configured to extract heat from the surroundings and thereby the LTS vessel produces a cooling effect on the surroundings. The extracted heat initiates a release of the ammonia (as shown in FIG. 1(2c) path d-e) and the decomposition heat extracted from the surroundings results in a refrigeration effect. Simultaneously, the HTS vessel is cooled and adsorbs the ammonia (as shown in FIG. 1(2c) path d-e).

(18) The HTS adsorbent cooling temperatures that result in a refrigeration effect are dependent on the selected sorbent material. CaCl.sub.2 can be cooled at 20 C. for 15 C. refrigeration effect, whereas MnCl.sub.2 and NiCl.sub.2 only need to be cooled at maximum 71 C. and 157 C., respectively for the same refrigeration effect. Therefore, choosing MnCl.sub.2 and NiCl.sub.2 as HTSs yields much better and lower-temperature refrigeration if a 20 C. heat sink is applied.

(19) By using chemical reactions (i.e. the formation of or breaking of chemical bonds, e.g. dative bonds), for example between refrigerant gases (such as steam or ammonia) and solid sorbents (such as MgO and halide salts), heat may be stored long term (with minimal losses) at one temperature and then extracted from the storage system as either: heat (at the same or a higher temperature), cooling or electricity. Energy extracted from the storage system can then be used to reduce the electricity, heating and/or cooling demand leading to financial benefits.

(20) There are two components of a thermochemical heat storage system:

(21) 1. A chemical reactor containing the sorbent material (solid or liquid) that can be heated or cooled. When it is heated (heat being supplied to the reactor, from either waste heat or the environment and converted to chemical potential energy) a refrigerant gas is desorbed and leaves the reactor. When the refrigerant enters the reactor and is absorbed, heat is generated and this is extracted from the reactor as heat and used in for example an industrial process.

(22) 2. A compressor/expander that either consumes work (electricity) in order to compress the refrigerant gas, or expands the gas to produce work that can generate electricity.

(23) An optional third component would be a condenser/evaporator that either condenses refrigerant leaving a reactor, producing a useful heat output, or evaporates the refrigerant with a heat input that can either be from the environment or waste heat from an industrial process.

(24) A key novel aspect of this storage technology is that the components are inter-changeable so that a bespoke system can be developed for an industrial plant or process depending upon the amount or frequency of recoverable heat produced, the demands for heating, cooling and electricity and the operational needs of the system. This flexibility improves efficiency, maximises energy demand reduction and allows the system to be utilised for a wide range of applications. A competing approach to improve industrial energy utilisation is a system with thermal energy storage using high temperature phase change materials and a suitable operating temperature Organic Rankine Cycle engine to reduce electricity demand within an industrial application.

(25) Cooling and electric power chemisorption systems employ compressors/expanders and the performance characteristics of ammonia-solid chemisorption such as heat and mass transfer, adsorption/desorption capacity, reactive materials and chemical reaction kinetics can be good.

(26) There are many types of reactors and heat exchangers able to be incorporated into the device and method (i.e. regenerators) such as cylindrical regenerators, shell and finned-tube regenerators, rotating multiple bed regenerators, plate heat exchanger regenerators.

(27) Alternative compressor/expander technologies are available and suitable for the device. Examples include rotatory devices such as scroll type, vane type, or lobe type devices, and examples of reciprocating devices include in-line type, V-shape type, tandem piston type, single-acting type, and double-acting type.

(28) Many materials have been studied as the porous support of the consolidated adsorbent compound, such as activated carbon, vermiculite, expanded graphite, zeolite, and silica gel. Certain porous supports have physical-sorption capability toward the refrigerant gas which contributes an extra sorption bonus. Others are just inert matrices.

(29) For example, expandable graphite is used to produce a porous supporter. The expandable graphite is expanded by heat treatment at approximately 600 C. for a duration of approximately 10 min by position the expandable graphite in an electric oven. The exact temperature and duration of heating with depend on different raw graphite materials. The expanded graphite is then mixed with a salt solution such as a halide salt, for example CaCl.sub.2 and dried for approximately 24 hours at 110 C. to remove the free water and allow the impregnation of the CaCl.sub.2.nH.sub.2O in to the expanded graphite material. The mixture is kept for several hours at a temperature of around 270 C. to calcinate the CaCl.sub.2.nH.sub.2O into CaCl.sub.2. The optimal mass ratio of salt to expanded graphite has been studied for improved heat and mass transfer. The optimal mass fraction of reactive salt over the total adsorbent compound ranges from 50% to 90%, e.g. from 65% to 80%.

(30) The compound adsorbent of CaCl.sub.2 and expanded graphite improves the thermal conductivity of pure salt (CaCl.sub.2) by about 36 times. The addition of expanded graphite texture contributes to the mass transfer of the refrigerant gas and reduces swelling and agglomeration that the pure salt adsorbent has been found to be susceptible to.

(31) The reaction equilibrium and dynamic behaviour for salt/refrigerant combinations has been studied for a number of salt/refrigerant combinations.

(32) High temperature phase change material stores may be used and may be tailored to specific industrial temperature ranges

(33) Many materials have been studied as the porous material or support for consolidated adsorbent compound, such as activated carbon, vermiculite, expanded graphite, zeolite, and silica gel. Some of the materials have physical-sorption capability toward the refrigerant, which provides an extra sorption bonus, and some are just inert matrices that provide a support for the adsorbent compound. The addition of these porous supporters enhances the heat and mass transfer properties of adsorbent materials, leading to overall performance improvement of the device.

(34) It will be clear to a person skilled in the art that features described in relation to any of the embodiments described above can be applicable interchangeably between the different embodiments. The embodiments described above are examples to illustrate various features of the invention

(35) Throughout the description and claims of this specification, the words comprise and contain and variations of them mean including but not limited to, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

(36) Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

(37) The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.