Solar Thermal Energy Storage

1 Importance and modes of energy storage.- 1.1 The importance of energy storage.- 1.2 Influence of type and extent of mismatch on storage.- 1.3 Size and duration of storage.- 1.4 Applications.- 1.4.1 Stationary applications.- 1.4.2 Transport applications.- 1.5 Quality of energy and modes of energy storage.- 1.6 Thermal energy storage.- 1.6.1Sensible heat storage.- 1.6.2 Storage in phase change materials (PCM).- 1.7 Mechanical energy storage.- 1.7.1 Storage as potential energy.- 1.7.2 Storage as kinetic energy.- 1.7.3 Energy storage in a compressed gas.- 1.8 Electrical and magnetic energy storage.- 1.8.1 Storage in electrical cap ac i tors.- 1.8.2 Storage in electromagnets.- 1.8.3 Storage in magnets with superconducting coils.- 1.8.4 Storage in a battery.- 1.9 Chemical energy storage.- 1.9.1 Synthetic fuels.- 1.9.2 Thermochemical storage.- 1.9.3 Electrochemical storage.- 1.9.4 Photochemical storage.- References.- 2 Sensible heat storage.- 2.1 Sensible heat storage basics.- 2.2 Sensible heat storage and type of load.- 2.3 Sensible heat storage media.- 2.4 Well-mixed liquid storage.- 2.5 Stratified liquid storage.- 2.5.1 Analytical studies on thermally stratified hot water tanks.- 2.5.2 Experimental studies on thermally stratified hot water storage tanks.- 2.5.3 Forced stratification in liquids.- 2.6 Containers for water storage.- 2.7 Packed bed storage system.- References.- Appendix -I.- Appendix - II.- 3 Latent heat or phase change thermal energy storage.- 3.1 Basics of latent heat storage.- 3.1.1 Heat of fusion (Latent heat).- 3.1.2 Employment of latent heat storage system.- 3.2 Liquid-solid transformation.- 3.2.1 Nucleation and supercooling.- 3.2.2 The rate of crystal growth.- 3.2.3 Types of solidification or crystallization.- 3.2.4 Melting and freezing characteristics.- 3.2.5 Interpretation of freezing curves.- 3.2.6 Relative rates of heat and mass transport.- 3.2.7 Binary phase diagrams.- 3.3 Phase change materials (PCM).- 3.3.1 Solid-solid transitions.- 3.3.2 Solid-liquid transformations.- i) Salt hydrates.- ii) Other inorganic compounds.- iii) Paraffins.- iv) Non paraffin organic solids.- v) Clathrate and semi-clathrate hydrates.- vi)Eutectics.- 3.4 Selection of PCM.- 3.5 Storage in salt hydrates.- 3.5.1 Nucleation and crystallization.- 3.5.2 Incongruent melting.- 3.5.3 Thickening agents.- 3.5.4 Some promising salt hydrates and the binary phase diagrams.- 3.6 Prevention of incongruent melting and thermal cycling.- 3.6.1 Thickening agents.- 3.6.2 Extra water principle.- 3.6.3 Rolling cylinder method.- 3.6.4 Adding SrCl2 6H2 C in CaCl2 H2O system.- 3.7 Storage in paraffins.- 3.8 Heat transfer in PCM.- 3.8.1 Freezing of tops of ponds.- 3.8.2 An approximate analytical model for a periodic process.- 3.8.3 Heat-exchange with fluid-flow between trays holding PCM.- 3.9 Heat exchange arrangement and containment of PCM.- 3.9.1 Encapsulation of PCM.- 3.9.2 Containment.- 3.9.3 Compatibility.- 3.9.4 Special heat exchangers for PCM.- (A) Passive systems.- (B) Active systems.- 3.10 Storage in PCM undergoing solid-solid transition.- 3.10.1 Storage in modified high density polyethylene (HDPE).- 3.10.2 Storage in layer perovskites and other organometallic compounds.- 3.11 Heat of solution storage and heat exchangers.- 3.11.1 Crystallization from saturated solution.- 3.11.2 Heat exchangers in heat-of-solution storage system.- References.- 4 Chemical energy storage.- 4.1 Introduction.- 4.2 Selection Criterion.- 4.2.1 Thermodynamic considerations.- 4.2.2 Reversibility.- 4.2.3 Reaction rates.- 4.2.4 Controllability.- 4.2.5 Ease of storage.- 4.2.6 Safety.- 4.2.7 Availability and Cost.- 4.2.8 Product separation.- 4.2.9 Reaction with water and oxygen.- 4.2.10 Technology.- 4.2.11 Catalyst availability and lifetime.- 4.3 Energy storage in thermal dissociation type of reactions.- 4.3.1 Thermal dissociation of SO3.- 4.3.2 Dissociation of Ammonia.- 4.3.3 Thermal dissociation of inorganic hydroxides.- 4.3.4 Thermal decomposition of carbonates.- 4.3.5 Decomposition of sulfates.- 4.3.6 Thermal decomposition of CS2.- 4.3.7 Organic hydrogenation/dehydrogenation reaction.- 4.3.8 Thermal dissociation of ammoniated salts.- 4.3.9 Oxides-Peroxides and super oxides decomposition.- 4.3.10 Hydride decomposition.- 4.3.11 The reaction N2 O4 2N0+02.- 4.4 Methane based reactions.- 4.5 Heat transformation (HT) and chemical heat pumps (CHP).- 4.5.1 Working materials for CHP and HT.- 4.5.2 Thermal efficiency of CHP cycles.- 4.5.3 Ammoniates based CHP.- 4.5.4 Salt hydrates in chemical heat pump.- 4.5.5 Hydrides in CHP and HT.- 4.5.6 Methanolated salts.- 4.5.7 Heat of solution systems.- 4.6 Three step approach.- 4.7 Energy storage by adsorption.- References.- 5 Longterm energy storage.- 5.1 Solar ponds.- 5.1.1 Classification of solar ponds.- i) Shallow solar pond.- ii) Salt gradient solar ponds.- iii) Partitioned solar pond (PSP).- iv) Viscosity stabilized ponds.- v) Membrane stratified solar pond.- vi) Saturated solar pond.- 5.1.2 Thermal stability of solar ponds.- 5.1.3 Salt properties.- 5.1.4 Passage of solar insolation into solar pond.- 5.1.5 Creation and maintenance of solar pond.- 5.1.6 Performance analysis of a solar pond.- 5.1.7 Heat extraction.- 5.1.8 Applications.- i) Space heating.- ii) Domestic water or swimming pool heating.- iii) Industrial process heat.- iv) Power production.- v) Desalination.- 5.1.9 Some remarks.- 5.2 Energy storage in aquifers.- 5.2.1 Operational strategies.- 5.2.2 Theoretical studies.- 5.2.3 Characteristics of the aquifer.- 5.3 Heat storage in underground water tanks.- 5.4 Heat storage in the ground.- References.- 6 Energy storage in building materials.- 6.1 Introduction.- 6.2 Basic passive designs.- 6.2.1 Direct gain systems.- 6.2.2 Convective loops.- 6.2.3 Thermal storage walls.- 6.2.4 Roof ponds.- 6.2.5 Attached sunspace.- 6.3 PCM in building panels.- 6.4 Experiments on PCM building panels.- 6.5 Applications.- References.- 7 High temperature heat storage.- 7.1 Introduction.- 7.2 Techniques for thermal energy storage.- 7.3 Sensible heat storage systems.- 7.3.1 Rock bed storage system.- 7.3.2 Rock bed-liquid (Dual medium) storage system.- 7.3.3 Two stage thermal storage in unpressurized liquids.- 7.3.4 Molten slag storage system.- 7.3.5 Thermal storage in large hollow steel ingots.- 7.3.6 Thermal energy storage in sand (fluidized bed).- 7.4 Phase change energy storage systems and ceramic pellets.- 7.4.1 Phase change salt and ceramic 570 pellets with air as working fluid.- 7.4.2 Phase change salt/metal storage systems.- 7.4.3 Phase change storage material with heat exchanger.- 7.4.4 Energy storage boiler.- 7.4.5 Storage heat in PCM and use of scraper for removing solid boundary layer.- 7.5 Chemical reactions.- 7.5.1 Catalytic decomposition reactions.- 7.5.2 Thermal dissociation reactions.- References.- 8 Testing of thermal energy storage system.- 8.1 Introduction.- 8.2 Historical development.- 8.3 Related studies.- 8.4 Basis and evolution of testing procedures.- 8.5 Standard procedure.- 8.5.1 ASHRAE 94-77.- 8.5.2 NBSIR 74-634.- 8.6 Some comments.- References.- Appendices.- Appendix 1 Conversion of units.- Appendix 2 Physical properties of some solid materials.- Appendix 3 Physical properties of some building and insulating materials.- Appendix 4 Physical properties of some liquids.- Appendix 5 Physical properties of some liquid metals.- Appendix 6 Physical properties of saturated water.- Appendix 7 Physical properties of saturated steam.- Appendix 8 Physical properties of some gases.- Appendix 9 Physical properties of dry air at atmospheric pressure.- Appendix 10 Freezing points of aqueous solutions.- Appendix11 Properties of typical refrigerants.- Appendix 12 Storage capacities.- Appendix 13 Properties of some promising latent-heat thermal energy storage materials.- Appendix 14 Solubility behavior of candidate salts for salt-gradient solar pond.