Optimising the inclination of solar panels taking energy demands into consideration

Abstract

Ideally, the angle of inclination of non-tracking solar panels, whether of the photovoltaic variety or solar thermal, should be determined in relation to the energy demand curve they are meant to satisfy. This is not always the case since it is common practice to install solar panels at a particular angle, depending on the geographical location of the site, irrespective of the demand curve. For example in Malta, installers have for many years been fixing panels for solar water heating at an angle of inclination of 45 degrees to the horizontal, since Malta is situated at a latitude of 36 degrees North. The authors of this paper have looked at a number of different demand curve scenarios, namely for maximum output, constant energy demand and constant hot water demand for the whole year and for winter and summer months. A computer program was written to simulate the solar radiation received on planes set at different angles of inclination and azimuth. A factor was introduced to correct for the effect of clouds, water vapour and particles in the atmosphere. The factor for Malta was derived using data downloaded from the website of the Joint Research Centre (JRC) of the European Commission. The program was then able to calculate the optimal angle of inclination for the different scenarios considered. To calculate the optimal angle for demand matching, two approaches were considered, one based on the best fit between demand and insolation using the lowest standard deviation and the other based on minimum area of collector panels.