Optical and thermal performance of sun-tracking CPC heat pipe evacuated tubular collector

A tracking CPC (Compound Parabolic Concentrator) solar collector with a concentration ratio of 2.3, which integrates CPC heat pipe evacuated tubular solar collector and crank rod tracking mechanism, has been developed. Based on the TracePro optical simulation software, the concentration behaviors of this CPC solar collector at different tracking modes were simulated. And its thermal performances were investigated experimentally. Simulation results showed that, the transversal projection angle (θ_t) is the vital factor that affects the optical performance. When θ_t is within the range of -23.5° and 23.5°, the incident angle modifier (IAM) reaches 0.95-1.14. By means of tracking, θ^t can be reduced effectively, providing a 30% higher optical efficiency compared to the fixed mode. The optical efficiency can reach over 60% only when the three positions intermittent sun-tracking method is adopted. The change tendencies of thermal efficiencies at different tracking modes are well in consistent with the simulated optical efficiencies. The tested effectively operating time and the average thermal efficiency in tracking modes are 2.7 and 2.1 times those of the fixed one, respectively. In addition, the linear of normalized efficiency is favorable. The fitted efficiency intercept is 52%, with the relative error lower than 12% to the simulated optical efficiency, which provides evidence of the correctness of former simulation results, to some extent.