Distributed dynamic modelling with experimental validation on a photovoltaic solar-assisted heat pump

Abstract

The photovoltaic/thermal solar-assisted heat pump is a system that directly integrates a Rankine refrigeration device with a photovoltaic/thermal solar collector. A specially designed direct-expansion PV evaporator is employed in the system to acquire thermal energy and electricity from solar radiation simultaneously. In this paper, a distributed model is presented that describes the dynamic performance of the system. Numerical simulation was performed with instantaneous solar irradiance and ambient temperature based on the model. A testing rig was built in Hefei, China, and experiments were conducted to verify the model. The results show that high photovoltaic and thermal performance can be obtained by the system. The average electrical efficiency is around 13.02 per cent. The output electricity is about 85.5 per cent of the power consumption, which means that the system can offer most of the power consumed by itself. Neglecting the heat loss of the water box, the highest coefficient of performance (COP c ) can reach up to 7.3 and the average value is around 3.41. Comparisons between the simulation results and the experimental measurements show that the model is able to give satisfactory predictions. experimental studies were done by researchers worldwide. Their efforts were focused on using either air or water as the coolant. Hegazy [2] conducted theoretical analysis on four common designs of PV/T air collector and suggested a suitable configuration for the PV/T air system. Huang et al.[3] studied a watertype PV/T system experimentally and introduced the concept of primary-energy-saving efficiency for the evaluation of the system. In recent years, the research group [4-6] has developed a new flat-box water-type PV/T collector. Numerical simulation on the dynamic performance has been done and the corresponding experiments have also been conducted both in Hefei and Hong Kong, China.Prakash [7] showed that the cooling effect of water is much better than that of air due to its thermo-physical properties. Nevertheless, for residential use, the hot water temperature has to reach at least 40 • C, which unavoidably lowers the cooling effect of the PV system. The working temperature of the refrigerant in a direct expansion evaporator is much lower and steadier. Therefore, if the refrigerant works as a coolant to the JPE559 Distributed dynamic modelling on a PV-SAHP JPE559 © IMechE 2008 Proc. IMechE Vol. 222 Part A: J. Power and Energy where x i , for i = 1, . . . , n, is the variable of the function.JPE559

Operational performance of a novel heat pump assisted solar façade loop-heat-pipe water heating system

“…The compressor's theoretical power consumption and its input power can be given by [42] N th ¼ ng v V com p com;in j j À 1 p com;out p com;in…”

“…(23) and (25)). However, owing to the difference in the two-phase flow patterns within the evaporator and condenser, the condensation heat transfer coefficient in the condenser's two-phase flow region can be computed by [42] h tp ¼ h l ð1 À x r Þ 0:8 þ 3:8x 0:76 r ð1 À x r Þ 0:04…”