Solar heat pump systems for heating applications : Analysis of system performance and possible solutions for improving system performance

Solar heat pump systems (SHPs) are systems that combine solar energy and heat pumps. SHPs have been investigated for several decades and have been proven to increase the share of renewable energy and reduce electric energy demand in residential heating applications. Many solar thermal heat pump systems have become market-available in recent years; however these systems are still not widely employed in the residential sector. This is due mainly to the high initial costs (investment and installation costs) of solar thermal heat pump systems, which limits their cost-effectiveness. Enhancing cost-effectiveness of solar thermal heat pump systems is necessary for a more effective and broader market penetration. In this thesis, solar thermal and photovoltaic systems combined with heat pumps for heating applications are treated. The overall aims of the thesis are to: 1) investigate techno-economics of SHPs and 2) investigate possible solutions for improving system performance of a reference solar thermal and heat pump system for residential heating applications. In the first part of the thesis, the influence of climatic boundary conditions on economic performance of SHPs has been investigated by means of: a) an economic comparison of SHPs found in the relevant literature and b) system simulations of the reference solar thermal heat pump system. In the second part of the thesis, potential solutions for improving system performance of the reference solar thermal heat pump system with limited change in system’ costs are investigated. A systematic approach was used for investigating cost-effectiveness of the system improvements in the reference system. Based on results of the cost-effectiveness analysis, some of the investigated system improvements were chosen for being included in the design of a novel solar thermal and air source heat pump system concept. The novel system was designed for a house standard with relatively high operating temperatures (55°C/45°C) in the space heating distribution system and for high space heating demand (123 kWh/m2·year). Finally, the thesis ends with a cost-effectiveness analysis of the novel system