Experimental study on a heat-pipe photovoltaic/ thermal system

In this study, a novel heat-pipe photovoltaic/thermal (HP-PV/T) collector is proposed. Compared with the traditional water-type PV/T collector, a heat-pipe photovoltaic/thermal collector does not freeze when used in cold regions by careful selection of a heat-pipe working fluid. Two types of heat-pipe photovoltaic/thermal collectors, with the tube spaces of heat pipes at 80 and 140 mm, were constructed. Two individual heat-pipe photovoltaic/thermal systems using each of the two types of collectors were also assembled. Outdoor tests were performed to study the performance of the two systems with solar collectors installed at tilt angles of 32 and 45°. A semi-empirical system efficiency model with variable (T_i-T̅_a)/H_t was used to correlate the results of the daily thermal efficiency, total PV/T efficiency and primary-energy-saving efficiency. Comparison analyses between the two systems and between the two solar collectors tilt angles were also carried out.