Performance improvement of a photovoltaic-thermal system using a wavy-strip insert with and without nanofluid

Abstract

The influence of the wavy-strip insert on photovoltaic-thermal (PVT) system performance was studied. To this end, computational fluid dynamics were used to model the 3-D PVT system and wavy-strip insert. The effect of the wavy-strip insert in a given total mass flow rate was examined on different numbers of the tube (N), which is in the range of 5–25. A rise in N has a direct correlation by an increase in PVT efficiencies; meanwhile, for N > 16 based on the ASHRAE method, heat removal factor and the overall heat-loss coefficient tend to be almost constant. Moreover, the effect of the wavy-strip insert is more pronounced in a lower number of tubes, so that for N = 5, the heat removal factor improved by 18%, and the overall heat-loss coefficient reduced by 3.5%. The PV plate temperature distribution is a crucial issue that can lead to serious thermal stress and lifetime degradation. A detailed study on the PV plate temperature distribution demonstrates that using the wavy-strip insert considerably reduces the temperature gradient. For N = 16, the optimum performance of the PVT module was obtained, and hence the effect of different Reynolds numbers ranging from 600 to 1600 was examined for it. It has been found that the use of insert in considered Reynolds number range will cause the thermal and electrical efficiencies to improve by 6.92–8.64% and 2.01–2.45% compared to a typical PVT system, respectively. In entire cases, the pump power consumption compared to the PV cells’ electrical output power is negligible. A comparative study on the performance improvement of this method and other commonly used methods was carried out. It has shown that this method can become competitive with other methods to improve the PVT performance; meanwhile, it can tackle with substantial problems of previous common methods. Lastly, for optimum configuration of the studied PVT system, further improvement is achieved by dispersing Al2O3 nanoparticles into the working fluid. The results elucidate that the integrated PVT system/Al2O3-water based nanofluid with a wavy-strip compared to the typical PVT system leads to improve electrical and thermal efficiencies by 3.5% and 12.06%, respectively.