The impact of soft shading on photovoltaic cells in the Maltese islands

Abstract

In this study the author explores the impact of soft shading on the performance of photovoltaic (PV) modules. Shades caused by obstacles, such as, pipes, poles, cables and vents that are commonly found on the rooftops of Maltese constructions. This research also intends to increase the knowledge of stake holders on PV systems and factors affecting their efficiency. The production of electric power in Malta is mainly generated from oil. In 2009, Malta scored second highest after Cyprus as oil dependent nation for the generation of electricity in European Union. This is considered as nonsustainable in the future and like all EU countries, Malta is committed from its part to achieve 10 percent of renewable energy by the year 2020. To this effect, the Malta Resource Authority (MRA) issued feed-in tariffs to encourage the Maltese population to invest in renewable energy generating sources. This led to an increased popularity and uptake of integrated solar photovoltaic systems installation. The Maltese Archipelago enjoys high potentials for solar energy generation due to its abundant long sunny days and high temperatures throughout the year. In his thesis the author studies the impact of shadow through experimental simulations by making use of three polyvinyl (PVC) pipes of diameters: 8 mm, 20 mm. and 50 mm. He also investigates the shading effect by positioning the different sized pipes at 20 cm, 30 cm, 50 cm, 100 cm., 150 cm. and 200 cm away from the PV module so as to establish the level of power loss and possibly indicate at which distance performance efficiency is least affected. For the experiment, three stand-alone PV modules of the model ET-M52620: P 8202.1 of the Ammonit brand are used, each module consisting of 36 monocrystalline silicon cells of 125mm2. The modules were set at different inclinations: 15° and 30°. A data logger was used to facilitate recording of the different parameters pertaining to the energy output. The experiment was performed in the month of May. Findings sustain that shading of obstacles as specified above impact negatively on the optimum performance of a PV system. It further indicates that the impact of shading on electric power production is not devastating. The percentage power loss varies according to the size of the obstacle as indicated hereunder: 1. PV module at 15° inclination: - 8mm obstacle between 0.07% and 1.30% - 20mm obstacle between 1.66 % and 3.43% - 50mm obstacle between 3.91% and 8.73% 2. PV module at 30° inclination: - 8mm obstacle between 0.06% and 2.86% - 20mm obstacle between 0.85% and 4.29% - 50mm obstacle between 7.17% and 12.22% The dissertation is divided into five Chapters. The first two chapters deal with the energy production situation in the Maltese Islands, its potential to generate renewable energy and the aim of this project. Chapter three focuses on a literature review, while chapter four includes mainly the experimental simulations and results. Chapter five summarizes overall conclusions, recommendations and proposes future studies.