| dc.description.abstract | Solar assisted air source heat pump (SAASHP), combining solar thermal energy and heat pump, shows great potential as a promising energy-saving heating technology. It is widely considered for supplying hot water (HW), space heating (SH) and/or space cooling in the domestic sector. The performance of SAASHPs can be affected by many factors such as system configuration, component size, weather conditions and working conditions. This project is aimed to find an efficient and cost-effective heating system based on SAASHP in UK weather conditions as a green heating method for the domestic sector. The serial, parallel and dual-source indirect expansion solar assisted air source heat pumps are modelled and simulated under the weather conditions in London using TRNSYS to investigate the operation performance over a typical year. These three heat pumps are applied to provide space heating and hot water of 300 L per day for a typical single-family house. The simulation results show comparisons of the three systems. The serial type heat pump shows the highest seasonal performance factor of 5.5, but requires a solar collector of 45 m² and a thermal energy storage tank of 3000 L. The dual-source and parallel type heat pumps show slightly lower seasonal performance factors of 4.4 and 4.5, respectively, requiring a solar collector of 18 m² and a thermal energy storage tank of 500 L. Furthermore, the results show that the air source part contributes to an important proportion of the heat provision and stable operation of the systems. The yearly seasonal performance factor higher than 4.4 achievable by the three heat pumps suggests that they are potentially applied in the regions with relatively lower solar irradiance. The economic analyses indicate that the parallel and dual-source type heat pumps provide cost effective alternatives to replacing the gas-boiler heating system. The set hot-water-supply temperature of the heating system affects both the system operation performance and the thermal comfort condition of the house. The effect of low temperature heating on the system operation performance is investigated to figure out the way to significantly save electricity. A single-family house is chosen as the reference building and the heating system is modelled and simulated under the weather conditions in London, Aughton and Aberdeen in the UK over a year. The set hot-water-supply temperatures are taken to be 40, 45, 50 and 55 ºC. For the heating systems, with the decrease in set hot-water-supply temperature from 55 ºC to 50, 45 and 40 ºC, the yearly seasonal performance factor increases and the yearly total electricity consumption decreases. The results show that low temperature heating enables a significant reduction in electricity consumption of such heating systems. To achieve high thermal performance and low cost, solar assisted air source heat pump heating systems are numerically simulated by integrating compound parabolic concentrator-capillary tube solar collectors. The heating system is used to provide both space heating and hot water for a single-family house in London, UK. The operation of the heating system is simulated by TRNSYS. The results are compared with those of the heating systems using flat plate solar collectors of the same area. The concentrated solar collectors increase the utilisation of solar energy by 6.5%, reduce the electricity consumption by 6.1% and thus increase the seasonal performance factor by 6.8%. Particularly, for almost the same seasonal performance factor, the area required for the concentrated solar collector is 12 m² while the area required for the flat plate solar collector is 18 m², leading to one third collector size reduction and hence significant cost reduction and convenient installation. According to both system performance and economic analysis, CPC-CSC with an area of around 9 m² is recommended. Considering further improvements in system design and operation, the heating system using smaller size CPC-CSC e.g. 6 m² can potentially achieve a higher SPFsys. Since solar collectors with a smaller size can be much more easily adopted for domestic use, using CPC-CSC benefits the wide rollout of SAASHP heating systems for domestic heating. | en_US |
