An Analytical Model for the Integrated Daily Performance of Solar Air Heating Systems

Abstract

An analytical Integrated Daily Performance Model (IDPM) is developed to predict the long term performance of solar air heating systems. The model is developed for systems using packed-bed energy storage and includes the effects of temperature stratification within the storage. The model makes use of the stratification coefficient approach to integrate the equations describing system performance. This analysis differs from similar previous analyses for water heating systems in that a control scheme more typical of air heating systems is used: collector output may go directly to either storage or the load. The IDPM is compared to simulations using a fully mixed model of storage and a single-phase model of storage. The comparisons show that the IDPM is more accurate than the mixed model and requires considerably less computation time than simulations using the single-phase model. In addition, the IDPM identifies several parameters that are important to system performance, but are not easily identified by non-analytical analyses.