Here – come the sun tracking solar siphons

Abstract

Flat surface solar thermal systems are normally installed at fixed tilts, facing the equator. In the tropics, fixed azimuth installations are disadvantageous because the two sun crossovers on the latitude dramatically raise beam incidence angles after one of the crossovers. Specifically for the equatorial belt, one could ask: where should the collectors face? In temperate areas, summer’s daily reflex angle solar azimuth ranges can cause obtuse angles of incidence on fixed collectors. This paper addresses these problems. It presents two low-cost sun-tracking solar siphons. One unit tracks about a single inclined axis every day throughout the year. The other does azimuth tracking but with seasonal adjustments of tilt. It was found that tracking can increase daily energy yield by up to 30% when compared with fixed units. The azimuth tracking unit performed better than the inclined axis one. In addition, it achieved higher temperatures. Both had to be installed as free standing units. A consideration of water flow in the inclined axis tubes revealed that there were thermal-siphoning failures in higher parts of the hot water header occasioned by inevitable mid-positioning of the collector outlet pipe. It was thus concluded that although the inclined axis tracking principle could be suitable for non-flow collectors, the azimuth tracking unit was the more appropriate to develop for commercialization of solar tracking solar siphons.