Energy payback time and Greenhouse Gas emissions: Studying the international energy agency guidelines architecture

Abstract

The International Energy Agency (IEA) in collaboration with an international panel of experts has published three editions of the Methodology Guidelines on Life Cycle Assessment of Photovoltaic Electricity (2009, 2011 and 2016) with the growing purpose of making increasingly precise assessments. This reference implies the estimation of major environmental indicators reported in literature, such as Energy PayBack Time (EPBT) and Greenhouse Gas (GHG) emissions in order to determine their benefits in terms of energy compared to conventional alternatives. However, in most cases this framework provides simplified calculations at the expense of accuracy. This study strengthens the monocrystalline (mono-Si) and polycrystalline (poly-Si) energy production estimation proposed by the IEA guidelines with formulas and calculation models of highest accuracy and contrast the resultant EPBT and GHG emissions in a case study. Likewise, a detailed analysis has been carried out to observe the range of orientations with the optimum performance while on the other hand; emphasis was placed on the need to compare the results directly with those corresponding to local energy sources, instead of regional or national ones. Results indicated that EPBT was 17%–19% and GHG emissions were 14–16% lower with the proposed method compared to the IEA guidelines respectively. Moreover, a range of orientations with near-optimal performance is also detailed. Finally, despite having clear environmental benefits compared to the local electric mix, its benefit is lower than if compared to the national electric mix in the case studied. Therefore, conclusions expressed herein contribute to reliability consolidation of PV technologies