Sawtooth V-Trough Cavity for Low-Concentration Photovoltaic Systems Based on Small-Scale Linear Fresnel Reflectors: Optimal Design, Verification, and Construction

Abstract

Ensuring the uniformity of solar irradiance distribution on photovoltaic cells is a major challenge in low-concentrating photovoltaic systems based on a small-scale linear Fresnel reflector. A novel sawtooth V-cavity design method based on an optimization algorithm to achieve uniform irradiance distribution on photovoltaic cells is presented. The reliability of the design was verified using the Monte Carlo ray-tracing method and a laser experiment. A prototype was built using 3D printing technology with a biodegradable green polymer material known as polylactic acid. The new cavity was compared to the standard V-trough cavity, keeping the cavity aperture, reflective surface area, and photovoltaic cell width constant. In addition, the focal height, number of mirrors, mirror width, and mirror spacing were also kept constant; so, the cost of the two configurations was the same from the point of view of the primary reflector system. The new design ensured the uniform distribution of solar irradiation and significantly reduced the height of the cavity. The significant decrease in the height of the proposed cavity has the following advantages: (i) a decrease in the dimensions of the fixed structure of the small-scale linear Fresnel reflector, thus reducing its cost, (ii) a significant decrease in the surface area exposed to wind loads, thus reducing the cost of the fixed structure and secondary system structures, (iii) a reduction in the difficulty of the manufacture, maintenance, and transportation of the cavity’s reflecting walls, and (iv) an increase in the cooling surface area, which increases the electrical efficiency of the photovoltaic cells.

Experimental Investigation of the Influence of Longitudinal Tilt Angles on the Thermal Performance of a Small-Scale Linear Fresnel Reflector

“…(v) Based on the length of the PV system, a mirror length of 658 (mm) was chosen. (vi) The optical properties of the materials used in the calculations were already used in previous studies [14,36]: mirror reflectivity ρ = 0.94 [37], mirror cleanliness CI m = 0.96 [38], glass cleanliness CI g = 0.96 [38], glass transmissivity τ g = 0.92 [39], encapsulant transmissivity τ e = 0.90 [40], and PV cell absorptivity α = 0.90 [40]. (vii) The optimal design conditions are impossible to meet from sunrise to sunset.…”

“…Therefore, a balance between the three curves shown in Figure 5 must be found. Based on other studies, θ t 0 is considered to be 46 ( • ) [14,36]. This choice guarantees 74.65% of the unattainable ideal value of 100% annual solar irradiation.…”