Effect of Boundary Conditions on Glazed Flat-Plate Solar Collector Performance Test Results
Abstract
This analysis investigates the effect of performance test boundary conditions on the glazed flat-plate solar collector performance test results. The current test standard allows for some variations in boundary conditions, which can lead to differences in thermal performance characteristics. This article focuses on variations in collector tilt angle, average air speed, solar irradiance at the collector plane, and heat transfer fluid flow rate. A series of experimental thermal performance evaluations of a specific flat-plate solar collector was conducted using an indoor solar simulator, following the ISO 9806 test standard under various boundary conditions. It was observed that differences in collector tilt angle and wind speed resulted in variations in thermal performance test results, especially under high values of reduced temperature difference. However, irradiance and heat transfer fluid flow rate variations did not yield significant differences in thermal performance test results. Subsequently, an annual simulation analysis was performed using ScenoCalc simulation software under various constant mean operating temperatures and the climatic conditions of Stockholm, Würzburg, and Athens. The results demonstrated that differences in test boundary conditions under the current test standard would not cause considerable differences in solar system energy output simulation results for the most common solar thermal system applications (pool heating, solar domestic hot water systems, and space heating). Conversely, differences in test boundary conditions could lead to significant disparities in energy output simulation results for high-temperature solar thermal applications, such as process heat thermal systems.