Effect of orientation and tilt angles of solar collectors on their performance: Analysis of the relevance of general recommendations in the West and Central African context

Abstract

Installing solar panels or collectors with optimum orientation and tilt angles to maximise energy generation over a specific period is important to improve the economics of solar systems, and hence, their large-scale utilisation. As a general rule, for installations aiming at maximum annual solar production in the intertropical region, it is recommended to point the panel towards the Equator at a tilt angle equal to the local latitude. However, there are several situations where it is difficult or even impossible to follow these general recommendations, for example in case of the presence of an obstacle creating shading, inadequate orientation or slope of the roofs, or when roofs are inaccessible. This raises the question of the impact of non-compliance with the general recommendations on solar systems’ performance. We have used RETScreen software for the calculation of annual average irradiation on tilted panels in various locations in West and Central Africa, namely in the capital cities (latitudes between 0° N and 15° N). For each site, the maximum annual solar irradiation is simulated and taken as a reference value. The annual irradiations for various orientations and tilt angles were then recorded and compared to the reference. It appears that in West and Central Africa, a moderate deviation (up to 20°) from the optimal orientation and inclination does not significantly influence the incident solar radiation (reduction in irradiation < 5%). Construction of structures dedicated to solar installations or architectural modification to comply with general recommendations is therefore generally not justified. A set of diagrams and tables, which allow us to quickly determine the percentage of incident solar radiation on a solar panel based on its orientation and tilt angle compared to the optimal tilt and orientation for any capital city in West and Central Africa, is provided.