Overview on Solar Thermal Plus Heat Pump Systems and Review of Monitoring Results
Abstract
In recent years several companies started offering Solar thermal And Heat Pump Systems (SAHPS) on the European Market; already in 2009 an overview was given for example by Zörner W. et al (2009). For single family houses the systems are offered as pre defined package (kit) solutions. The systems deliver thermal energy for heating, domestic hot water and eventually as well cooling to the building usually without any further back up burner. The hydraulic schemes of the single systems, especially the degree of integration of the solar thermal and electrical driven heat pump unit vary significantly. The same is true for the used low temperature heat source for the heat pump where ground heat exchangers (horizontal and vertical), ambient air, specific solar collectors, phase change material storages (e.g. ice/water) and exhaust air are implemented. The objective of combining solar thermal and heat pump units is to enhance the overall share of renewable heat applied, by allowing a high Solar Fraction (SF) and an enhanced Seasonal Performance Factor (SPF) of the heat pump system. This second figure is claimed to be up to SPF ~ 5 in some commercial presentations. The practical experiences with such systems are still limited and the published monitoring results are only in part in line with the mentioned expectations. Within the Task 44/Annex 38 of the International Energy Agency (IEA) Solar Heating and Cooling Program / Heat Pump Program, such systems are analyzed in detail, including simulations, evaluation of monitoring results and development of test procedures. The target of the present paper is to give an overview on commercially available Solar thermal And Heat Pump Systems (SAHPS) and a review on published monitoring results from realized installations.