Optimum number of glass covers of thermal flat plate solar collectors

Abstract

Within the framework of Libya's pursuit to harness solar energy and integrate it into the national energy mix, surpassing a 50% contribution from renewable energies by 2050, this study focuses on the optimal utilization of solar energy, both photovoltaic and thermal, along with wind energy. The research presents an exemplary design for flat solar collectors, emphasizing the requisite number of transparent covers to achieve optimal thermal performance. Simulations were conducted under specified weather conditions, including solar irradiance of 100W/m2, ambient air temperature of 30°C, and wind speed of 3m/s. Operating conditions were set at a flow rate of 100m3/h, with the inlet air temperature equal to the ambient air temperature. The efficiency equation provided by the manufacturer, a linear function considering the fluid inlet temperature, ambient air temperature, and solar irradiance on the inclined collector surface at a 30° angle south, was adopted. Consequently, a novel design for flat solar collectors, incorporating both air and water channels, was proposed. The design was delineated based on temperature differentials between the absorber plate and ambient air in distinct intervals: the range (5-0°C) without any cover, the range (40-5°C) with one cover, the range (85-40°C) with two covers, the range (140-85°C) with three covers, the range (180-140°C) with four covers, and the range (>180°C) with five covers. This distribution was applied to an air-based flat solar collector of 5m length, resulting in the following configuration: no cover for distances (0-0.1m), one cover for distances (0.1-2.3m), two covers for distances (2.3-3.9m), and three covers for the remaining distance (3.9-5.0m).