Performance of a domestic straight-through type solar receiver

A 435 m² micro-arc Fresnel concentrating solar collector pilot installation integrating the domestic straight-through type receiver(STR), which was the key component of moderate temperature heat collecting system, was set up. A one dimensional steady-state heat transfer model of the receiver was developed. Based on this model, the influences of vacuum level, temperature difference between the metal absorber and ambient as well as wind speed on heat loss were analyzed. The effects of solar irradiance, concentration ratio and flow rate of the heat transfer oil on the thermal efficiency of this pilot installation were investigated. Also, the thermal efficiency was measured experimentally. The results showed that, the heat transfer model could well describe and predict the characteristics of the STR with a lower than 2% relative error of the calculated results compared with the experimental data. Vacuum level and the temperature difference are the major factors that influence the heat loss, and the annulus pressure should be kept lower than 0.013 Pa. A correlation was developed to predict the heat loss as a function of the temperature difference through nonlinear regression. The thermal efficiency reaches 55.4% with a concentration ratio of 25 at 625 W/m² direct solar irradiance. The optimized flow rate is 3.5 m³/h. The domestic STR, which has the heat collecting performance similar to the UVAC3 during the temperature lower than 200 ℃, is perspective for the moderate temperature solar heat applications.