Orientation and Tilt Angle of Parabolic Trough Solar Concentrator at Different Latitudes

摘要

The parabolic trough solar collector (PTC), may be oreinted in E-W or N-S direction with their axes horizontally. An investigation of the collection efficiency by a horizonal PTC at any angle between E-W and N-S orientation is presented at different latitudes. A generalised equation for the incidence angle and the rotation angle is obtained for this purpose. An optimization for the collector tilt angle of North-South orientation is obtained all over the year at any latitude. The results show that the PTC of North-South orientation at sites having latitude #phi# < 15 deg gives the highest daily collection efficiency all over the year. For sites having a latitude angles #phi# > 15 deg, it is preferable to orient the collector in the range of 70 deg < = #psi# < = 90 deg to obtain higher daily collection efficiency in winter. The results show that, there is an orientation at which the PTC gives nearly a constant daily collection efficiency all over the year, that is at vales of #psi# ranging from 60 deg to 70 deg measured from the south direction. Also, the effect of the surface azimuth angle #psi# on the collection efficiency is minor at latitude angle ranging from 30 deg to 40 deg, outside this range the effect of #psi# becomes major. In winter and summer, for sites having latitude angle #psi# < #delta#, the optimum collector tilt angle for the PTC of North-South orientation, varies linearly with latitude angle. The present study shows that the monthly adjusted PTC reaches about 99% efficiency of that with two-axis tracking.