Experimental study of a pilot-scale fin-and-tube phase change material storage

The large-scale deployment of solar-assisted systems in the residential sector relies on innovative thermal energy storage units. This paper contributes to the present-day discussion by proposing a pilot-scale phase change material storage, whose size has been selected to be coupled with solar-assisted heat pumps. The storage unit consists of a fin-and-tube heat exchanger placed within a tank: water is circulated on one side of the heat exchanger and, on the other side, commercial paraffin RT26 is employed. The storage system is operated considering two heat exchanger configurations (viz., parallel and series configurations) and implementing a broad set of boundary conditions, to test the storage unit under relevant operating conditions. To this end, a novel test rig with electrical resistances (to provide the heating load) and a heat pump (to provide the cooling load) has been designed and build. The results were commented in terms of global and local performances; it was found that the proposed storage, compared with a volume-equivalent water storage, is able to store 65% higher thermal energy. In addition, the dataset obtained in this research is attractive to validate numerical codes of phase change material storage units.