Implications on EROI and climate change of introducing Li-ion batteries to residential PV systems

Abstract

In this study, we investigate the sustainability aspect of residential PV installations combined with batteries — with a focus on EROI (Energy Return On Invested Energy) and CO2 reduction potential. We pay special attention to situations where an excess of photovoltaic power generation is not allowed to be fully fed into the distribution grid and has to be (partly) curtailed. To this extent, we estimate the impact of residential solar batteries in three different European countries: Switzerland, Norway, and Spain. The combined EROI (PV coupled with battery) was shown to be greater for all battery sizes up to 30 kWh compared to a scenario where excess PV production would be curtailed, with Spain’s EROI almost doubling from around 8 for the case of no battery to 15 for an 18 kWh battery. For Switzerland and Norway, the EROI is improving by about 50% to 11 and 9, respectively, with the ideal size being smaller at 12 kWh. Optimal battery sizes were also calculated for different curtailment thresholds, which are set to increase in the coming years due to higher PV penetration in national power grids. Residential solar batteries were demonstrated to be a viable addition in all geographical settings from a Net Energy Analysis point of view. When considering CO2-equivalent emission reduction potential of a PV plus battery system, the local grid’s CO2 intensity is decisive, increasing the benefit in countries such as Spain and Switzerland, but worsening overall impacts in Norway for oversized batteries.