Cross Linear Solar Concentration System for CSP

Abstract The novel solar concentration system, Cross linear (CL) system, with which a high cosine factor above 0.85 can be achieved through the year even in winter season and at high latitudes, has been invented by Tokyo Institute of Technology. Theoretical expression of the cosine factor for CL system can be given by cosine factor = sin δ{cos ϕ (-cos μ) + sin ϕ sin μ) + cos δ cos ω(sin ϕ cos μ + cos ϕ sin μ), where δ, ϕ, μ, amd ω are solar declination, latitude, elevation angle of the reflection mirror, and hour angle, respectively. The value of tan μ corresponds to the ratio of the receiver height and mirror position distance from the receiver position for the receiver/mirror configuration of the CL concentration system. One simulation result for the CL system sample geometry (tan μ = 0.7, mirror length 1.5m, mirror number=13 in north side, and 2 in south side from the receiver) shows that we can get 7.7kWh/m 2 /d for each mirror (as average) in December at 36.8°N latitude and 11.5 kWh/m 2 /d in August, assuming DNI = 1.0 kW/m 2 and collection efficiency = 1.0. Nearly the same result is obtained at high latitude of 40 ο N latitude. Thus, a higher cosine factor above 0.85 can be obtained in winter months even at the higher northern latitude. Also, the CL system can eliminate the end loss, and a comparison study shows that CL system can significantly increase the optical efficiency compared to Trough and LFR (Linear Fresnel Reflector system). Also, from the flux values above 100 kW/m 2 obtained by simulation for the CL system sample, it can be expected that a higher temperature around 600-700 °C can be reliably obtained and the air is heated up with a tubular receiver even in the winter season. With varying the parameters for CL system configuration, suitable solar concentration system with a high cosine factor could be designed depending on a wide temperature range of 300-700 °C. A joint collaboration between Japanese and Indian industries, institutes and universities has been launched to demonstrate and develop the CL system technology in Dec 2012.