Accurate modeling of instantaneous solar radiation

Abstract

The need for alternative energy sources is becoming more and more apparent as time goes by. The world's resources of fossil fuel are rapidly decreasing, and scientists are looking for alternate routes to solve the energy problems faced by most nations on earth. One such route is the utilization of Solar energy which is abundant in enormous quantities. For example, the amount falling on Lake Erie can supply the needs for the entire nation. Solar Engineers have been trying to bring Solar Energy into the picture as an alternative source of energy for many years now, because of its promise in providing efficient and economical systems. However, the design of an efficient and economical system depends on the accuracy of predicting the amount of radiation received during the period in which the system is expected to operate. Unfortunately it is very difficult to model incoming radiation because of constant changes in atmospheric conditions. The best that could be done, thus far, is to use previous radiation data average over a number of years or a specific locality, and through statistical analysis predict future insolation. Such a technique was present by Liu and Jordan in 1960. It turns out, however, that this kind of approach is not very useful for predicting the performance of a solar system because it is an averaging technique and solar systems do not operate on an average basis. Thus, the need for a model that predicts instantaneous radiation that is not averaged over the entire day (which in turn is averaged over the entire month) is yet to be satisfied. Alexander and Taft have derived such a model using Liu and Jordan's technique along with Meinel's development of Laue's observations.

This paper outlines a computer program which models and tests Alexander and Taft's technique and outputs instantaneous insolation data for 10 different locations around the country. Using this technique, modifications to Laue's curves were proposed for the different locations under study. The program can be used to predict instantaneous solar insolation for any location in the world where monthly average total radiation data are available.