Nanofluids for improved efficiency in cooling solar collectors - A review

The use of nanofluids for cooling is an attracting considerable attention in various industrial applications. Compared with conventional fluids, nanofluids improve the heat transfer rate, as well as the optical properties, thermal properties, efficiency, and transmission and extinction coefficients of solar systems. The effects of different nanofluids on the cooling rate and hence the efficiency of solar systems can be experimentally investigated. Accordingly, this review paper presents the effects of nanofluids on the performance of solar collectors from the considerations of efficiency and environmental benefits. A review of literature shows that many studies have evaluated the potential of nanofluids for cooling different thermal systems. The second part of this paper presents an overview of the research, performance, and development of photovoltaic/thermal (PV/T) collector systems. Descriptions are made on water PV/T collector types, analytical and numerical models, and simulation and experimental works. The parameters affecting PV/T performance such as covered versus uncovered PV/T collectors, absorber plate parameters, and absorber configuration design types are extensively discussed. Exergy analysis shows that the coverless PV/T collector produces the largest total (electrical+thermal) exergy. Furthermore, PV/T collectors are observed to be very promising devices, and further work should be carried out to improve their efficiency and reduce their cost. Therefore, using nanofluids for cooling PV/T systems may be reasonable.