The concentrating solar power is a promising technology for scalable solar electricity. The conversion of concentrated sunlight into heat is of paramount importance in the concentrating solar power. The current commercial parabolic trough collector has an annual average efficiency of approximately 50%, and the poor efficiency mainly results from the cosine loss. In this paper, a 300-kWth solar parabolic trough collector with north-south and rotatable axis tracking is originally presented. The rotatable steel-support frame and the slide rail can achieve the horizontal rotation of the parabolic trough collector. The rotation of the collector can change the surface azimuth angle of the collector, further reducing the solar incidence angle and thus reducing the cosine loss. Two patterns of tracking are adopted in this prototype. In summer, the solar incidence angle is small, and the north-south axis tracking is adopted. In winter, the solar incidence angle is large, and the cosine loss is serious, so using the rotatable axis tracking enables more solar irradiation to be harvested. The experimental results show that, by using the rotatable axis tracking, the daily average efficiency can be enhanced from 43% to 48% in winter. This study provides a promising approach for effectively reducing the cosine loss for the scalable parabolic trough collector, providing the possibility of improving the annual average collector efficiency and realizing cost-effective solar energy use.

Conclusions:

A prototype of a 300-kWth solar parabolic trough collector is originally presented and has rotatable and north-south axis tracking patterns. Tests on the thermal performance are studied. For the north-south axis tracking, the daily average efficiencies of 63% and 40% are obtained in summer and winter, respectively. Furthermore, comparison experiments on the effect of the cosine loss are carried out in winter. The results show that adopting the rotatable axis tracking reduces the daily average cosine loss by 10.3% and increases the daily average collector efficiency by 5.0% compared with north-south axis tracking. Thus, the solar parabolic trough collector prototype presented in this paper has the potential to increase the collector efficiency and further improve the solar energy utilization.

The results have been published on Applied Energy 207 (2017) 7–17.