Solar cooling and heating plants: An energy and economic analysis of liquid sensible vs phase change material (PCM) heat storage

摘要

A key factor for the energy optimization of a solar heating/cooling plant is the design of the heat storage. Latent heat storage system using phase change materials (PCMs) is an effective way of storing thermal energy and takes advantage from the high-energy storage density and the isothermal nature of the storage process. It is interesting to evaluate the potential of integrated solar absorption cooling and heating systems with sensible vs PCMs heat storage tanks, Dynamic transient simulations by Trnsys tool were used as a basis for assessment for a typical offices building and solar heating and cooling plant application sited near Rome. An optimization of the storage capacity from both energy and economic point of view has been performed, considering the tanks on both the sides of the plant (the one coupled to the solar field, the hot storage, and the other coupled to the absorption chiller, the cold storage). Different cases have been simulated: both tanks modeled as sensible (water) storage, only hot side tank modeled as PCM storage and only cold side tank modeled as PCM storage. In the second case, two different sub-cases have been further considered: "hot" (temperature of fusion 89℃) and "warm" (temperature of fusion 44℃) PCM heat storage. Results indicate that the solution that features the lowest global primary energy consumption and the highest solar ratio provide a 3000 1 "warm" tank filled with PCM melting at 44℃ and a 2000 1 "cold" sensible (water) storage.