Optical performance comparison of two receiver configurations for medium temperature Linear Fresnel Collectors

Linear Fresnel collectors are good candidates to lower the use of fossil fuels in the built environment and in the industry, due to their compact nature and adaptability. In addition, the technology shows large margins for improvement, in terms of efficiency capital and operational expenditures. The present study presents a new atmospheric double tube absorber, which fully explores non-imaging optics design. An existing LFR system with a second stage concentrator consisting of an evacuated tube with an associated secondary parabolic reflector, is compared with a novel model adopting the same LFR primary field but a new second stage concentrator, which achieves a much wider acceptance angle. It is shown that, beyond a better performance, the novel proposed solution provides simpler maintenance, as in cleaning and parts' replacement, and a reduced cost, as it includes cheaper standard components. The study was conducted in ray-tracing environment with the Tonatiuh++ software, which is able to directly implement non-imaging optics configurations via analytic equations. The present study is centred on the optical performance of the collector. The quantitative comparison demonstrates that the annual yield of the novel model is increased at least by 8.3% while the cost per metre of the receiver is decreased by 45%.