Experimental evaluation of solar collector performance

Abstract: Solar energy is today one of the most important sources of renewable energy, it is an environmentally friendly and unlimited source that can be used anywhere in the world. There are several different types of solar collectors and methods to harness solar energy, however this project focuses on flat plate collectors used for water heating systems.   This project aims to evaluate how the operational parameters, mass flow rate and tilt angle, affect the thermal efficiency of a flat plate solar collector. A theoretical model has been concluded in Microsoft Excel 2011 in order to determine the performance of the collector. Furthermore a minor field study has been conducted in Sri Lanka, where a simple solar water system has been built. This consisted of a flat plate collector without an absorber plate and glazing. From this warm water system, experimental measurements have been extracted and employed in the theoretical model.   The result of the project shows that the mass flow rate had a large impact on the collector’s efficiency, however the tilt angle did not. After comparing the results with existing studies on collector performances it was discovered that the tilt angle should affect the efficiency to a greater extent. It was discussed that the result of this project may show a false representation of the tilt angle because of too small changes being made when taking the readings. The average efficiency of the studied collector was 35%, which is considerable less than the average efficiency of a typical flat plate collector. It has been acknowledged, however, that the studied flat plate collector has all the thermal losses, convection, conduction and radiation, as it lacks absorber plate, glazing material and insulation, thus the low average efficiency value.   The influencing parameters have been studied in relation to the global irradiance and it has been concluded that the global irradiance has a direct impact on both the mass flow rate and the tilt angle. Since historical averaged data has been used for the global irradiance it is not possible to obtain exact values for the efficiency, hence causing uncertainties in the results.