## The V -I characteristic of a photocell can be described by a rather complex mathematical formula

The V -I characteristic of a photocell can be described by a rather complex mathematical formula, which can be handled with a computer but is too complicated for an in-class exam. To simplify handling, we are adopting, rather arbitrarily, a simplified characteristic consisting of two straight lines as shown in the above. The position of point C, of maximum output, varies with the Iν/I0 ratio. Empirically, VC = VOC 0.7+0.0082 ln Iν I0 and IC = Iν 0.824 + 0.0065 ln Iν I0 . Now consider silicon photodiodes operating at 298 K. These diodes form a panel, 1 m2 in area, situated in Palo Alto (latitude 37.4◦ N, longitude 125◦ W). The panel faces true south and has an elevation of 35◦. In practice, the panel would consist of many diodes in a series/parallel connection. In the here, assume that the panel has a single enormous photodiode. Calculate the insolation on the surface at a 1130 PST and at 1600 PST on October 27. Assume clear meteorological conditions. Assume that the true solar time is equal to the PST. 1. Calculate the insolation on the collector at the two moments mentioned.