An optimized tracking strategy for small-scale double-axis parabolic trough collector

Small-scale double-axis parabolic trough collector (PTC) is suitable for solar thermochemical reactions and solar-aided coal-fired power plants. In the present work, the double-axis PTC is numerically investigated and an optimized tracking strategy is proposed. That is to maintain PTC at the half-day optimal azimuth angles in the morning and afternoon, shifting at solar noon, in order to maximize the annual received solar radiation amount. The half-day optimal azimuth angle is found correlated to the latitude and varies diversely through a year. A normalized rating method is proposed to generally evaluate the performance of the proposed tracking strategy under theoretical and practical conditions. The results indicate that the recommended regions and periods to apply the proposed tracking strategy are low and middle latitudes (phi = -60 degrees to 60 degrees) and autumn and winter seasons (N-day = 266-80), respectively, where the performance is rated above 0.6 regarding the traditional single-axis and double-axis tracking strategies. Experiments have been carried out on a 300 kWt double-axis PTC rig in Langfang, Hebei, China, in early November. Compared to the north-south single-axis tracking strategy, the proposed optimized tracking strategy (14 NW) shows roughly 68.8% higher in heat gain and 15-17 percentage points boost in collector efficiency. (C) 2016 Elsevier Ltd. All rights reserved.