Utilizing the solar and geothermal energy in space heating systems can save fossil fuels and reduce emissions. In this study, compound parabolic concentrator (CPC) photovoltaic/thermal collectors (PV/T), absorption and ground source heat pumps are integrated to a novel space heating system for use in hotel and office buildings. A full simulation model of the system is constructed and validated by using the Engineering Equation Solver software. The heating system is analyzed against its energy, environmental, economic, and flexibility performance using multiple variables including the PV coverage ratio, ambient temperature, solar beam irradiance, and electricity price. The results show that integrating solar and geothermal energy can be effective to supplement the space heating demand. The best integrated performance point of the office building gives a 32% energy saving ratio, 9% annual cost savings ratio, 23% emission reduction ratio, and 67% excess adjustable ratio compared to a pure ground heat pump system. This research provides new directions of integrated performance evaluation of heating systems assisted by renewable energy resources. (C) 2021 Elsevier Ltd. All rights reserved.

An improved evacuated absorber tube (AT) design consisting of a semi-circular tube is proposed for large-aperture parabolic trough concentrator. The absorber tube also contains a flat-plate radiation shield in the vacuum part of the tube in the glass cover. To enhance the heat transfer in the AT, different fins geometries added to the bottom of the AT were analyzed here. Compared to an AT without fins, the thermal efficiency of the tube could be increased from 75.7% to 76.9% with a short and thick fin and to 77.3% with a long and thin fin in the flow velocity range of 0.4-1.5 m/s. The long and thin finned AT shows better enhancement of heat transfer, but the heat transfer performance factor also accounting for frictional losses is higher for short and thick fin. Simultaneously, increasing the number of long and thin fins in the AT would not improve much the heat transfer performance. (C) 2020 Elsevier Ltd. All rights reserved.