Design, analysis and optimization of solar industrial process heat plants without storage

Abstract

Solar industrial process heat applications which have a constant daytime load every day of the year permit optimal collector utilization, thus minimizing the cost of solar energy. In particular, one can avoid the cost and performance penalties associated with storage of solar heat, if the backup can operate at variable heating rate. Hence, these applications are particularly relevant for the near future when solar equipment is still relatively expensive and one is looking for solar applications with the lowest possible cost. This paper develops a method for designing and optimizing installations of this type, including a quick procedure for selecting the most cost effective collector and calculation of pumping energy. The economic optimum is shown to imply a slightly oversized collector field with dumping of excess energy during peak insolation. Using recently developed correlations for the annual energy collectible by the principal collector types, we state all results as explicit algebraic equations which are readily evaluated with a hand calculator. The accuracy is on the order of 3 percent if there is no uncertainty in the input variables. The method is illustrated by an example.