Contribution of a photovoltaic solar system to the energetic sustainability of a Portuguese WWTP

Abstract

The concerning growth of energy and water demand worldwide presents two major issues that can both be tackled by using renewable energy sources to oppose the energy consumption of wastewater treatment plants (WWTP), while taking advantage of their energy production potentialities. This work deals with the sizing of a photovoltaic system of a medium-sized Portuguese WWTP designed to meet the energy consumption needs, benefitting from the higher levels of irradiance in the country. The goal is to act as a model for future similar projects. The potentiality of producing electricity through cogeneration of biogas, in WWTP’s of activated sludge, needs to be taken into account. In the study case, 70% of the energy consumption needs were covered via cogeneration. This led to the conception of two different scenarios concerning the PV System: the first one covers the total electric needs of the WWTP and the other covers 30%, taking into account that the cogeneration system ensures 70%. During the 25 year-life of the PV System, an average annual performance ratio of 0.805 for scenario 1 and 0.789 for scenario 2 was achieved. Furthermore, the average energy contribution of scenario 1 and 2 was 36.5% and 32.8%, respectively, ensuring 100% of self-sufficiency, when adding the cogeneration contribution.