Abstract
The chapter discusses various phase-transition heat-accumulating materials. Their application in heat pumps and their use for heat supply are presented. Phase-transition heat-accumulating materials in heat pipes are also considered, various types of heat pipes are presented. The installation of heat storage with phase-transition materials is presented. Along with phase-transition heat-accumulating materials, the chapter considers thermochemical heat-accumulating material of photochemical reactions of energy storage. As an example of a thermochemical heat-accumulating material, a solar power plant for thermochemical energy storage is presented. A developed computer program for the description of thermochemical reactions allows examining chemical and thermochemical reactions in multicomponent reciprocal systems, which can be carried out in the course of the reciprocal multicomponent systems. The computer program allows identifying thermochemical reactions occurring in mutual multicomponent systems, regardless of component and dependent on temperature.
TopBackground
The success of the creation and introduction of thermochemical heat accumulators, which can be considered as seasonal, depend on the solution of thermophysical problems related to the selection of the necessary working substances and the economic problems associated with their cost parameters.
Chemical reagents and reactions for a chemical heat accumulator must meet the following requirements:
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Cheapness and accessibility;
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High volumetric density of stored energy;
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If possible, reaction without catalyst;
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Be chemically inert with respect to the structural materials of the thermal battery;
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Ease in implementing control over the course of a chemical reaction by means of temperature or pressure;
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A large number of thermochemical cycles;
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Have a large and developed external surface to intensify the course of the chemical reaction.
Of great importance is the search for new energy-intensive thermochemical heat-accumulating materials. Literary analysis (Magomedov, 2000; Engelsht & Muratalieva, 2013) shows the wide possibilities of their application. In addition, the chemical reactions used to store energy can convert low-potential energy into a high-potential energy. A similar feature is not possessed either by batteries based on phase transitions, nor, especially, by heat capacity.
Chemical energy can be stored either directly in the form of the internal energy of the molecules (for example, obtaining under the action of light enriched energy conformers, in particular valence isomers), or in reaction products that can interact with each other, releasing energy in a useful form.
To accumulate solar energy, in particular, it is possible to use any endoenergetic reactions that under the action of solar radiation (SR), accompanied by a rearrangement of chemical bonds or molecular structure. At the same time, two groups of processes that convert solar energy into chemical energy-photochemical and thermochemical can be distinguished from the mechanism of action of SR.
Key Terms in this Chapter
Underground Heat Accumulator: The thermal energy accumulator located under the ground surface with different types of thermal insulation and heat storage materials.
Heat Accumulator: Device for heat accumulation for the purpose of its further use.
Heat Storage Material: Material used for the accumulation of thermal energy and may be classified according to the material class, the way of accumulation and heat release as well as from the cyclic operation.
Heat Storage System: The system of devices intended for temporary storage of thermal energy by means of various heat-storage materials and including a number of auxiliary equipment including heat exchangers, pumps, pipelines, fittings, test equipment and automatic devices, as well as other devices serving and providing the work of the heat storage system.
Phase-Transfer Heat-Accumulating Material: The type of heat-accumulating material using latent heat of phase transitions of the heat-accumulating material.
Thermochemical Heat Accumulator: The type of heat accumulator based on the use of binding energy of reversible chemical reactions of chemical accumulation.