An Experimental Investigation of Influence of Relative Humidity on Thermal Performances of a Parabolic Trough Solar Concentrator

Abstract

Solar energy is considered by many as a highly prospective alternative energy source due to its ability to meet a significant portion of the world's energy demand. The effectiveness of a solar concentrator depends on operational and atmospheric conditions. This paper presents an experimental analysis of the influence of humidity coupled with inclination angle and mass flow rate on the performance of a parabolic trough solar concentrator.  The parabolic trough solar collector underwent experimental testing at the LAUTECH engineering facility in Ogbomoso. It possesses a collector length of 2.1m, an aperture width of 1.2m, an adjustable rim angle of 75^o, 90^o, and 105^o, a focal length of 30 cm, a 10-liter storage reservoir, and variable flow rates of 0.0004 m³/s, 0.0008 m³/s, and 0.0012 m³/s. Temperatures were measured using a 12-channel temperature recorder (SD data logger), solar radiation was measured using a solar meter, relative humidity was measured using an environment meter,  and water was used as the working fluid. Thermal performance analysis was conducted to ascertain the impact of relative humidity coupled with tilt angle, mass flow rate, and weather conditions on the solar concentrator's effectiveness. The findings reveals that at higher mass flow rates and a 90° tilt angle, the system has a greater thermal efficacy with weather elements such as solar intensity and relative humidity. Parabolic trough concentrators' performance is determined by the amount of solar intensity focused onto a receiver tube and high humidity in the air reduces the quantity of direct solar radiation that reaches the concentrator and high relative humidity reduces the thermal effectiveness of the system. While relative humidity may not be the main factor influencing the performance of a parabolic trough concentrator, its effects on thermal efficiency and heat exchange should be taken into account when designing and operating such solar thermal systems, especially in environments with varying humidity levels.

Keywords Parabolic Trough Collector, Heat loss, Thermal efficiency, Humidity.

DOI: 10.7176/JEES/14-2-05

Publication date:March 31^st 2024