Development of Heat Storage System Using Metal Hydride: Experiment of Performance by the Actual Loading Condition

An innovative heat storage system with metal hydride (MH) applied to air conditioning of buildings is investigated. The characteristics that metal hydride generates heat at absorption process and absorbs heat at desorption process is useful for new air conditioning system without chlorofluorocarbon (CFC). The trial system is composed of two heat storage vessels of a “shell and tube type” heat exchanger with heat transfer fins and filled with MH and a compressor equipped for hydrogen transfer. The system proposed in this paper is simple because the heat storage vessel has two functions of heat source and heat storage, and suitable for environment because of no usage of CFC. The purpose of heat storage is to decrease the difference of the electric power demand at daytime and that at night. That is to say, the effective heat storage system consumes electric power at night and requires no power at daytime. In the innovative heat storage system with metal hydride, the hydrogen is transferred using electric power at night and transferred in reverse only by the pressure difference between two heat storage vessels at daytime. The trial system was operated at actual loading condition, and the performance of the MH heat storage system was evaluated. As the experimental result, heat storage finishes in a limited time, and heat quantity for cooling was 13.5MJ, which was sufficient for the heat capacity to cool the 10m² room for 3 hours. In addition, the coefficient of performance of the system is 2.44.