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

摘要

Small-scale solar concentrators based on Linear Fresnel Collectors (LFC) are a promising technology for domestic and industry applications. In such small 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 less time-consuming procedure is the analytical method, based on the equations that describe the sun and mirror positions. This method was used in this paper to study the behavior of the optical end losses with latitude and LFC geometry. A simple least square fitting expression was proposed to estimate the average annual non-illuminated length and the end loss factor for any latitude - between 0° and ±40° - and for any LFC azimuth. In particular, instantaneous, daily and annual periods at different latitudes for a North-South tracking LFC were analyzed. Finally, the instantaneous non-illuminated length on a short LFC system in Salta city, Argentina (24.7°S, 65.4°W) was experimentally determined through digital imaging analysis. A good agreement between the theoretical and the experimental values was found with average RMSE values of 6%.