Experimental investigation of the thermal response of a thermal storage tank partially filled with different PCMs (phase change materials) to a steep demand

•Experimental plant designed and developed to test thermal storage tanks.•Test methodology developed to reproduce common situations in real facilities.•100L tank filled with 3 types of PCMs, macro- and micro-encapsulated compared.•The thermal response to a steep demand is not as slow as expected.

The inclusion of PCM (phase change materials) for improvement of thermal energy storage is a current topic of study, particularly for domestic hot water accumulation. An experimental setup with a 100-L tank was implemented to assess the behaviour of these materials. The PCMs used in this work consist of three different hydrated salts with different encapsulations. An experimental methodology based on a steep thermal demand was developed to compare and study the energy contribution and thermal response of these materials. The calculated energy balance shows that the thermal lag of the three different PCM and encapsulations is less than expected, which means that after 14 min of a thermal demand in the range of 25–30 kW, over 90% of the PCM appears to have aided the response of the tank. In addition, the estimated thermal lag of the different PCM reflects the typical stratification pattern of the tank. This study demonstrates that the three different materials studied in this work (PCM A, PCM B and PCM C) are suitable for delivery of energy during the typical steep demand found in domestic heating, but if the expected response is delivery of heat for fast recovery of the tank, different encapsulations should be used. Finally, a viability analysis of employing these materials is carried out taking into account stability, availability and economic factors.