Evaluation of Combined Solar Thermal Heat Pump Systems Using Dynamic System Simulations

This paper presents results from the national Austrian project “Highly efficient combinations of solar thermal and heat pump systems (SolPumpEff)”. In this project different combinations of solar energy and heat pump systems are considered through dynamic system simulations in TRNSYS [1]. In such systems solar thermal energy can be used on one hand directly to charge the buffer storage and on the other hand as heat source for the evaporator of the heat pump (HP). In this work systems, in which solar heat is only used directly (parallel operation of solar and HP) and systems using the collectors also as a heat source for the HP are analysed and compared to conventional air HP systems. With a combined parallel solar thermal HP system the system performance compared to a conventional HP system can be significantly increased. Unglazed selectively coated collectors as source for the HP have the advantage, that the collector can be used as an air heat exchanger. If solar radiation is available and the collector is used as source for the HP, higher temperatures at the evaporator of the HP can be achieved than with a conventional air HP system.