The collector's efficiency is the collector's capability to utilize the useful heat gain achieved from solar energy. Three elements, namely, the incidence angle modifier, the heat loss coefficient, and the optical efficiency, need to be assessed aim to obtain the thermal efficiency.
Solar energy collectors are crucial for converting solar radiation into usable forms like heat or electricity. There are two main types of collectors: non-concentration and concentrating collectors. In non-concentration collectors, the collector area and absorber area are the same.
High temperatures that are required to achieve the utmost efficiency can be obtained by increasing the energy flux density of the solar radiation incident on a collector. According to Lupu et al. energy efficiency of a solar thermal collector is: ... ... Cp, m, and T are latent heat, mass of plate, and temperature, respectively.
The maximum possible useful energy gain (heat transfer) in a solar collector occurs when the whole collector is at the inlet fluid temperature; heat losses to the surroundings are then at minimum. The collector heat removal factor times this maximum possible energy gain is equal to the actual useful energy gain .
The collector efficiency varies with respect to the collector material (soil type/absorber plate material and transparent cover material), location, available solar radiation and the slope of the collector. The open solar-air collector accounts for about 50% of the investment cost of a SCPP and about 30% of the overall system losses .
The progress of solar energy conversion technologies during the last few decades triggered the development of various types of collectors, thermal, photovoltaic (PV), or hybrid. In this paper, authors present the basic elements of thermal (energy and exergy) analysis solar collectors and their efficiency.