Life-cycle assessment of electricity in Portugal

Abstract

The Portuguese electricity mix is undergoing a significant shift away from the technologies that have dominated generation for the past decades. This article aims at assessing the environmental life-cycle impacts of electricity generation and supply in Portugal (PT), including: (i) modeling the main electricity generation systems; (ii) modeling the transmission and distribution (T&D) grid infrastructure; (iii) characterizing the evolution of the electricity sector in PT from 2003 to 2012; and (iv) discussing how the recent changes in the technology portfolio affected the environmental performance of the electricity generated and supplied. The life-cycle assessment methodology was used to quantify impacts in: non-renewable fossil energy demand (nREn), global warming (GW), abiotic depletion (AD), acidification (AC), eutrophication (ET), photochemical oxidation (PO) and ozone layer depletion (OD). From 2003 to 2012, an overall reduction of the environmental impacts was achieved. In particular, since 2008, electricity generation impacts in AC and PO dropped sharply as a result of the installation of desulphurization (62% reduction in AC; 74% reduction in PO) and denitrification (5% reduction in AC) systems in coal power plants (PP), as well as the phase out of large fuel oil PP. For NREn, AD and GW, the reduction of impacts was less pronounced (9–22% in the generation mix; 14–22% in the supply mix). T&D grid added 5–14% to the environmental impacts due to infrastructure (<5%) and T&D losses (5–9%). Despite the large increase in renewable capacity (especially wind) and the investments in lower-carbon fossil fuel technologies (natural gas), electricity generation still relies heavily on coal. There is, however, potential to further reduce environmental impacts in key categories (NREn, AD and GW) since there is significant available capacity of natural gas combined cycle currently underutilized.