Environmental performance evaluation of a grid-independent solar photovoltaic power generation (SPPG) plant

Abstract

This paper presents the environmental analysis of a solar photovoltaic power generation (SPPG) plant model, proposed for small off-grid communities. The analysis carefully considers both the life cycle energy- and the emission-related impacts of the plant's components, such as the PV array and the balance of system (BOS). Results reveal that a proposed 54.15 kW SPPG plant has global warming potential (GWP) ranging from 72,445 to 75,085 kg CO2−eq. The results further show that the battery system accounts for ∼85–90% of the plant's GWP impact. The battery also accounts for ∼68–75% of the total cumulative energy demand (CED) of 7.01–10.36 × 106 MJ. The energy payback times (EPT) for the PV-only range from 2.12 to 4.39 years, while a relatively higher value of 9.41–10.36 years was obtained for the PV and the BOS. The net energy ratio (NER) values of 4.56–9.43 and 2.24–2.52 were obtained for the PV-only and the PV with BOS, respectively, for a lifetime of 20 years. The NERs obtained for a lifetime of 25 years were 5.7–11.79 and 2.41–2.66, while the values obtained for a 30-year lifetime range from 6.83 to 14.15 and 2.54 to 2.78. These results have been obtained under different solar irradiation levels, lifetimes and performance ratios (PRs) of 1450–2200 kWh/m2/yr, 20–30 years and 60–80%. The research outputs demonstrate that the battery system has the highest life cycle energy and emissions impact because of its relatively shorter lifespan and the replacements over the system's lifetime. However, a sensitivity analysis reveals that the impact of the battery reduces as the lifespan increases. In addition, the GWP and the EPTs increases as the PRs are decreased, while the NERs are reduced. The significance of the study is that it reveals the effect of solar irradiation, lifetimes, PRs and the battery lifespan on the SPPG plant's environmental performance, which can be a basis for understanding solar PV life cycle impact for different locations around the world.