Thermal energy storage
Thermal Energy Storage A thermal energy storage module comprising a composite phase change material, wherein the composite phase change material comprises: a phase change material having a composition which absorbs or releases heat isothermally, or substantially isothermally, by transitioning, in a respective transition direction, between a first phase state and a second phase state at a predetermined transition temperature, wherein the composite phase change material comprises at least 40 wt % of the phase change material, based on the total weight of the composite phase change material, the phase change material being in the form of a continuous phase, a discrete phase, or a mixture of continuous and discrete phases distributed within the composite phase change material; a structural material for structurally shape-stabilising the phase change material, the structural material comprising particles which are solid in a predetermined working temperature range including the predetermined transition temperature and are chemically compatible with the phase change material, wherein, for structurally shape-stabilising the phase change material, the phase change material is contained in interparticle regions between the particles of the structural material, wherein the composite phase change material comprises at least 10 wt % of the structural material, based on the total weight of the composite phase change material; and a plurality of voids distributed within the composite phase change material, wherein the plurality of voids accommodates at least a portion of a volumetric change of both the phase change material and the structural material in the predetermined working temperature range.
1 . A thermal energy storage module comprising a composite phase change material, wherein the composite phase change material comprises:
(i) a phase change material having a composition which absorbs or releases heat isothermally, or substantially isothermally, by transitioning, in a respective transition direction, between a first phase state and a second phase state at a predetermined transition temperature,
wherein the composite phase change material comprises at least 40 wt % of the phase change material, based on the total weight of the composite phase change material, the phase change material being in the form of a continuous phase or a mixture of continuous and discrete phases distributed within the composite phase change material,
wherein the phase change material comprises at least one inorganic salt or a mixture of a plurality of inorganic salts, and
wherein the phase change material further comprises dispersed particles for providing anti-leakage additive and heat transfer enhancement functionalities; wherein the composite phase change material further comprises
(ii) a structural material for structurally shape-stabilising the phase change material, the structural material comprising particles which are solid in a predetermined working temperature range including the predetermined transition temperature and are chemically compatible with the phase change material, wherein, for structurally shape-stabilising the phase change material, the phase change material is contained in interparticle regions between the particles of the structural material, wherein the composite phase change material comprises at least 10 wt % of the structural material, based on the total weight of the composite phase change material and wherein the particles of the structural material have an average particle size within the range of from 20 to 150 microns; and
(iii) a plurality of voids distributed within the composite phase change material, the plurality of voids being randomly and uniformly dispersed in the phase change material, wherein the plurality of voids accommodates at least a portion of a volumetric change of both the phase change material and the structural material in the predetermined working temperature range.
2 . The thermal energy storage module according to claim 1 , wherein the at least one inorganic salt, or a mixture of a plurality of any of the inorganic salts, is selected from the group consisting of nitrates, nitrites, carbonates, chlorides, bromides, fluorides, sulphates, and hydroxides.
3 . The thermal energy storage module according to claim 2 , wherein the phase change material comprises at least one alkali metal salt.
4 . The thermal energy storage module according to claim 1 , wherein the phase change material comprises a binary, ternary or quaternary eutectic mixture of individual phase change material components.
5 . The thermal energy storage module according to claim 1 , wherein the phase change material comprises dispersed particles having an average particle size within the range of from 10 nm to 10 microns.
6 . The thermal energy storage module according to claim 1 , wherein the composite phase change material comprises from 40 to 85 wt % of the phase change material, based on the total weight of the composite phase change material.
7 . The thermal energy storage module according to claim 1 , wherein the particles of the structural material are selected from the group consisting of inorganic particles, carbon particles, and polymeric particles, or any mixture of two or more thereof.
8 . The thermal energy storage module according to claim 7 , wherein the structural material comprises inorganic particles composed of a solid material selected from the group consisting of alkaline earth metal oxides, vermiculite, and clay minerals, or any mixture of two or more thereof.
9 . The thermal energy storage module according to claim 1 , wherein the structural material comprises porous particles, the phase change material being additionally contained in intraparticle regions within the porous particles of the structural material, wherein the particles of the structural material have an average particle size within the range of from 5 to 2000 microns.
10 . The thermal energy storage module according to claim 1 , wherein the composite phase change material comprises from 15 to 60 wt % of the structural material, based on the total weight of the composite phase change material.
11 . The thermal energy storage module according to claim 1 , wherein the particles of the structural material are randomly packed in the composite phase change material, with both the interparticle and intraparticle regions containing the phase change material.
12 . The thermal energy storage module according to claim 1 , wherein the voids have a total volume fraction of from 1 to 30% based on the total volume of the composite phase change material at 25° C. and wherein the voids have an average width within the range of from 0.01 to 100 microns.
13 . The thermal energy storage module according to claim 1 , wherein the anti-leakage additive dispersed in the phase change material comprises inert filler particles which are solid in the predetermined working temperature range, wherein the inert filler particles of the anti-leakage additive have an average primary particle size within the range of from 1 to 500 nanometers.
14 . The thermal energy storage module according to claim 13 , wherein the composite phase change material comprises from 0.01 to 10 wt % of the anti-leakage additive, based on the total weight of the composite phase change material.
15 . The thermal energy storage module according to claim 13 , wherein the inert filler particles comprise one or more of metal oxides, silicon oxides, carbon, carbides, clay, and metal particles and wherein the inert filler particles of the anti-leakage additive are primary particles or agglomerates comprising a plurality of the primary particles, and wherein the agglomerates have an average agglomerate particle size within the range of from 10 to 2000 nanometers and the inert filler particles of the anti-leakage additive have an average primary particle size within the range of from 10 to 100 nanometers.
16 . The thermal energy storage module according to claim 13 , wherein the inert filler particles, or if present the agglomerates, are randomly and uniformly dispersed in the phase change material.
17 . The thermal energy storage module according to claim 1 , wherein the particles of heat transfer enhancement material are selected from the group consisting of carbon, metal oxide, metal, and carbide, or a mixture of any two or more thereof.
18 . The thermal energy storage module according to claim 17 , wherein the particles of the heat transfer enhancement material have an average particle size within the range of from 0.01 to 100 microns and the composite phase change material comprises from 0.01 to 20 wt % of the heat transfer enhancement material, based on the total weight of the composite phase change material.
19 . The thermal energy storage module according to claim 1 , wherein the composite phase change material further comprises:
(vi) an exterior layer adjacent to and surrounding at least a portion of an external surface of the composite phase change material, wherein the exterior layer seals the composite phase change material against at least one of, or two or more of, (a) leakage of the phase change material from the composite phase change material, (b) oxidation of components of the composite phase change material by an oxidising environment, and (c) corrosion of surrounding materials in contact with the composite phase change material module by a corrosive component of the composite phase change material.
20 . The thermal energy storage module according to claim 19 , wherein the exterior layer comprises (a) a chemically reducing agent for decreasing any oxidation of the components of the composite phase change material and/or (b) an inorganic particulate which is solid in the predetermined working temperature range.
21 . The thermal energy storage module according to claim 20 , wherein the chemically reducing agent comprises a carbon material, a carbide, and/or a metallic material, or any mixture thereof and/or wherein the chemically reducing agent is in the form of a particulate, wherein the particulate of the chemically reducing agent has an average particle size within the range of from 0.02 to 1000 microns.
22 . The thermal energy storage module according to claim 21 , wherein the carbon material comprises graphite, the carbide comprises silicon carbide, and/or the metallic material comprises iron.
23 . The thermal energy storage module according to claim 19 , wherein the inorganic particulate of the exterior layer has the same composition and/or particle size as the structural material and/or wherein the exterior layer comprises a mixture of the chemically reducing agent and the inorganic particulate and/or wherein the exterior layer has a total thickness of from 10 to 4000 microns.
24 . The thermal energy storage unit comprising at least one thermal energy storage module according to claim 1 which is assembled into a three-dimensional shape to form the thermal energy storage unit,
wherein the thermal energy storage unit is in the shape of a sphere, brick, disc or rod.
25 . The thermal energy storage unit according to claim 24 , further comprising a metal, a ceramic, or an enameled metal casing which surrounds the composite phase change material and is in direct thermal contact with the composite phase change material module(s).
26 . The thermal energy storage device comprising a plurality of the composite phase change material units according to 24 , wherein the units are assembled together in direct or indirect thermal contact to form a unitary assembly of the units.