Passive techniques for the thermal performance enhancement of flat plate solar collector: A comprehensive review

One of the most abundantly available non-conventional energy sources is solar energy. The advantages of solar energy are that it is freely available, sustainable, non-exhaustible, pollution-free, etc. Many thermal energy technologies are frequently employed to utilize solar energy for different household, agricultural, residential, and industrial applications. A flat plate solar collector (FPSC) is one of the most popular devices for harvesting solar energy and transforming solar radiation into useful heat. The low thermal performance of FPSC is one of its major disadvantages. The performance of the FPSC can be enhanced using active, passive, and mixed methods. In this article, various thermal performance enhancement techniques of FPSC, including design and modification, use of inserts, selective coating, nanofluid, phase change material, mini/microchannels, and transparent insulation material, are discussed. The use of nanomaterial coatings can reduce the convection and radiation losses from the FPSC. High absorptivity black nickel nanoparticles make them excellent for selective coatings. The performance of FPSC with CuO/water nanofluid was more efficient than that of other metal oxides. The performance of a minichannel integrated FPSC is better than that of conventional type because of its direct contact with water, which enhances the heat transfer rate. The most recent technological development of enhanced FPSC discussed in this article will be very useful to the scientific community.