Results from measurements on six solar water storage tanks for space heat and domestic hot water show that the new key performance indicator for stratification efficiency of the storage system correlates well with the simulated and emulated electricity demand of a heat pump that is charging the storage. While the stratification efficiency was the decisive factor for the energetic performance of the system, the determined heat losses of the storage system showed no correlation with the overall energetic performance of the system.

SPF Institute for Solar Technology