Least square based method for the estimation of the optical end loss of linear Fresnel concentrators

Abstract

Small-scale solar concentrators based on linear Fresnel (LFC) are a promising technology for domestic and industry applications. In such short systems, optical end losses and their influence on the energy performance are crucial issues. Although ray tracing is the most used method to estimate end losses, a less detailed and time-consuming procedure is the analytical method, which is applied in the literature to very specific sites or LFC mirror configurations. This paper studies the optical end losses behaviour with latitude and LFC geometry through the analytical method. A simple analytic equation to estimate the average annual non-illuminated length and end loss factor for any latitude -between 0 and ±40º- and LFC geometry is developed. Instantaneous, daily and annual periods at different latitudes and geometries were analyzed. Finally, the instantaneous non-illuminated length on a short LFC system in Salta city, Argentina (24.7ºS, 65.4ºW) was experimentally determined through digital imaging analysis. A good agreement between the theoretical and experimental values was found, with average RMSE values of 6%.