Thermal Energy Storage and Transport

The efficient use of energy is important to restrain the emission of greenhouse effect gases. Thermal energy storage and heat transport technology enable to utilize the renewable energy and the waste heat which are generally unstable, maldistributed, and thin. They also enable to operate energy devices at a highly efficient condition. This chapter introduces some basic research and development activities of thermal energy storage and heat transport, especially latent heat utilization. First, the following fundamental knowledge of thermal energy storage is explained: (1) the functions of thermal energy storage, (2) the classification of storage methods, (3) the characteristics of thermal energy storage materials especially phase change materials (PCMs), and (4) the constitutions of thermal energy storage devices. Other characteristics and challenges of latent heat thermal energy storage (LHTES) which utilize supercooling phenomenon are also explained. Second, several examples of the practical use of LHTES including the utilization of snow and ice are discussed. In the same way, several characteristics and examples of the practical use of the heat transport using latent heat are also explained. Furthermore, recent developments on the following research subjects are introduced: (1) thermal energy storage for hot water supply using the supercooling phenomenon of sugar alcohol, (2) heat storage for space heating using the supercooling of hydrate, (3) the improvement of thermal characteristics of paraffin wax as a PCM, (4) a steam accumulator using sugar alcohol, (5) pipeless heat transport using sugar alcohol or hydrate, and (6) heat transport method using the microencapsulated PCM slurry.