Working PrincipleIn parabolic trough collector, long, Parabolic mirrors focus the rays of the sun into an absorber pipe. The mirrors track the sun on one linear axis from north to south during the day. The pipe is seated above the mirror in the centre along the focal line and has a heat-absorbent medium running in it. The collector is generally composed of one bent glass mirror, with either silver or aluminium coated on the backside of the glass. The glass is about 4mm thick and low in iron, maximizing the reflectance of incoming sunlight. Parabolic trough collectors are a low cost implementation of concentrated solar power technology that focuses incident sunlight onto a tube filled with a heat transfer fluid. The efficiency and cost of the parabolic trough collector designs is influenced by structural stiffness, choice of materials, assembly tolerances, mirror cleanliness and wear. ADVANTAGES:1. The working Fluid can achieve higher temperatures in a concentrator system when compared with another evacuated tube system of the same solar-energy collecting surface. This means that a higher thermodynamic efficiency can be achieved.2. The thermal efficiency is greater because of the small heat-loss area relative to the receiver area.3. Reflecting surface requires less material and is structurally simpler than other collector. For a concentrating collector, the cost per unit area of the solar collecting surface is therefore less than that of another collector.4. Owing to the relatively small area of receiver per unit of collected solar energy, selective surface treatment and vacuum insulation to reduce heat losses and improve the collector efficiency are often economically viable.
