Energy Payback Time of a Rooftop Photovoltaic System in Greece

Abstract

Life Cycle Analysis (LCA) is an important tool to quantitatively assess energy consumption and environmental impact of any product. Current research related to energy consumption in buildings moves towards Nearly Zero Energy Building (NZEB). In such a building, an important issue concerns the energy production by renewable sources, including on-site production. The most feasible way to achieve renewable energy utilization in a building level in Greece is by using rooftop Photovoltaic (PV) systems, also promoted in the last decade by the national legislation concerning energy conservation measures. Apart from cost-related issues and payback times, Embodied Energy (EE) and Embodied CO2 (ECO2) emissions have also to be considered against the anticipated corresponding savings. Using a particular PV system as a case study, its basic constitutive materials are determined and their masses are calculated. Embodied energy values are estimated by using embodied energy coefficients available in the international literature. Considering a specific geographic location in Greece for the building on which the PV is installed, the annual energy generated by the system is estimated based on its performance data and curves. The Energy and CO2 Payback Times (EPBT and CO2PBT) are estimated and assessed, as well as future work is suggested.