The Environmental Profile of a Building-Integrated Concentrating Photovoltaic System with Hexagonal Concentrators and Micro-Tracking: Embodied Energy and Other Indicators

This paper aims to evaluate the eco-profile of a building-integrated concentrating photovoltaic system (photovoltaic-cell electrical efficiency: 21.6%; geometrical concentration ratio: 12.5×), extending previous work on the design and energetic/optical performance of this system (University of Lleida, Spain). There is a lack of studies on the eco-profile of these technologies; for this reason, this study is based on environmental life cycle assessment (case study: a building in Barcelona; tools: SimaPro/ecoinvent, inventory-of-carbon-and-energy). Focusing on global warming potential and cumulative energy demand, the impacts range from 341 to 507 kg CO2.eq/m2 and from 5660 to 7505 MJprim/m2. Energy and greenhouse-gas payback times vary between 2.5 and 6.7 years and are shorter than the useful life of this energy-generating element (pessimistic scenario: 15 years). Avoided-impact calculations have also been performed, verifying the benefits of this system during the use phase. Overall, the results are comparable to those of traditional photovoltaic systems. The additional advantage of the proposed modules is that they serve as an atrium and offer illumination, successfully combining the benefits of concentrating photovoltaics (high efficiency; reduction in the amount of solar-cell material required), two optical media (achromatic doublets), hexagonal solar concentrators (high packing efficiency) and micro-tracking (overcoming limitations of bulky external trackers).