Improving the performance of large-aperture parabolic trough solar concentrator using semi-circular absorber tube with external fin and flat-plate radiation shield

Abstract An improved absorber tube (AT) design consisting of a semi-circular and external flat fin with a flat-plate radiation shield inside an evacuated annulus is proposed for large aperture parabolic trough concentrator (PTC) systems. In the present design, the AT's semi-circular part absorbs the most sun rays. The other rays originally absorbed by the AT's upper part is now intercepted by the external two fins. And the flat-plate radiation shield reflects the external radiation energy from the AT's upper half back to the AT. The trough condenser has the 8m diameter and 80° half rim angle, and the AT consists of a semicircle with a diameter of 100 mm and outer fins with a length of 10 mm. The optical and thermal efficiency of this new design could reach up to 83.3% and 80.3%, respectively. The optical and thermal efficiency was 8%-units higher than that of traditional optimal design. The maximum temperature always appears at the edge of the fin, which is up to 50 °C higher than that of the heat transfer fluid (HTF) at 0.5 m/s, which was the optimal fluid rate for the new design and the fins also make contribution to the PTCs of 6.5% optical efficiency and more than 3.5% thermal efficiency. The improved AT design contribute to plan more effective PTC systems.