Effects of battery technology and load scalability on stand-alone PV/ICE hybrid micro-grid system performance

This study investigates the performance of hybridised micro-grids based on solar PV supplemented by Internal Combustion Engines (ICE). Three different battery technologies (lead acid, lithium-ion, and vanadium redox flow) as well as the effects of load demand scalability are considered. The optimisations are based on Cost of Energy (COE) but the analyses consider several performance indicators including Excess Energy (EE), Renewable Penetration (RP), and Duty Factor (DF). Optimisations are done using the software tool HOMER (Hybrid Optimisation Model for Electric Renewable) and consider systems spanning 10 to 50 houses (210 kWh/yr to 1050 kWh/yr) and subject to modelling featuring hourly temporal resolution. A sensitivity analysis is also conducted to see the effects of various input parameters on the Cost of Energy. Results indicate that both PV/ICE/Li-ion and PV/ICE/LAB hybrid systems have comparable COE (0.31 0.32$/kWh). This occurs largely because the capital cost is lower for PV/ICE/LAB, but this is offset by relatively high replacement and O&M costs. This study highlights the need to use multi-objective optimisations (system sizing not just based on COE), and to specifically include lifecycle emissions when comparing between stand-alone hybrid systems that feature multiple options of battery technology. The results also highlight that when system sizing only considers COE, the optimisations yield comparable outcomes for both PV/ICE/LAB and PV/ICE/Li-ion hybrid systems. (C) 2018 Elsevier Ltd. All rights reserved.