How does the thermal characteristics of PVT panels influence the performance of PVT heat pump systems

The effect of the thermal efficiency of hybrid photovoltaic – thermal (PVT) collectors was evaluated in system simulations where PVT collectors were used as source for a heat pump. The demand represented space heating and domestic hot water usage for a single-family house located in Denmark. With the presented system and emands it turned out that the value for the optical performance of the thermal absorber for the PVT collector had only marginal effect on the overall yearly system performance. An increase of the heat loss coefficient from 14.5 W m-2 K-1 to 58 W m-2 K-1 resulted in 1.7% higher electricity production of the solar cells due to lower PVT collector temperatures and 2% less electricity purchased from the grid due to higher COP in the heat pump caused by higher inlet temperatures to the heat pump in periods without solar radiation. The main effect of varying the different thermal characteristics was the minimum temperatures in the PVT collectors, hich affect the heat pump performance and COP. The largest risk is that the brine temperature at the inlet to the heat pump will drop below the limits of the heat pump causing it to switch off and run only on direct
electrical heating.