Optimum Radiation Availability for New Delhi and Pune

Liu and Jordan method is used generally to determine optimum tilts for a given location. Although, it is a classical method but it suffers from various errors. An improved method has been used, for this purpose, in the present work. This method was developed by Hay, Davies, Klutcher and Reindl, known as HDKR Method, and takes account of the errors like circumsolar radiation and horizon brightening. It has been used to determine monthly optimum tilts for two types of surfaces: fixed surface (south facing); azimuthally tracking surface (i.e. one-axis tracking surface). The study has been carried out for two Indian stations: New Delhi (28.63º N, 77.2º E) and Pune (18.53º N, 73.85º E). Solar radiation has been computed, by using this method, on normal-incidence tracking surface also (i.e. twoaxis tracking) and inter-comparison among these various surfaces has been carried out. It is seen that difference in optimum tilts, as determined by these two methods, is about 4 degrees. The average increase in solar radiation is about 15% in case of fixed surface w.r.t horizontal surface. In case of one-axis tracking surface, average increase is about 40% w.r.t. horizontal surface and 20% w.r.t. fixed surfaces. For two-axis tracking surface, the increase is about 45%, 25% and 5% w.r.t. horizontal surface, fixed surface and one-axis tracking surface, respectively. As the increase in solar radiation for a two-axis tracking is only about 5% over the one-axis tracking surface, considering the complexity and cost of two-axis tracking system, one-axis tracking system is recommended for collecting solar radiation.