PARTIAL ABSORPTION COATING FOR ALL-GLASS BOTTOMLESS SOLAR THERMAL ENERGY COLLECTORS

摘要

A bottomless solar thermal energy collector and method of making the same are disclosed. The solar thermal energy collector includes an inner translucent tube having a series of stress-relief grooves configured to reduce the stresses exerted due to temperature changes of the liquid located in the collector. The inner translucent tube also includes an absorptive coating disposed on an upper semicylinder of the tube and a reflective coating disposed on a lower semicylinder of the tube. An outer translucent tube is positioned around the inner translucent tube and a vacuum is disposed between them. The collector also includes collector-end regions where the diameter of the inner translucent tube decreases and the spacing between the inner translucent tube and the outer translucent tube increases. The grooves are created in the inner translucent tube by locally heating the tube, thinning the tube at the heated portion, reducing the tube's diameter at the heated portion, and then pushing the ends of the tube back towards each other.