Techno-economic analysis of the Local System Operator concept in a multi-dwelling unit in Sweden : A parametric sizing and optimization of a PV-battery system with EVs equipped with vehicle-to-home application

Abstract: The climate change of the environment raises concerns about the increasing greenhouse gas (GHG) emissions where the energy sector is a large contributor to the emission problems. As the electricity demand rises, due to increased population, urbanisation, and improved lifestyle, expanding the renewable generation can solve the problem of covering the increased electricity demand while decreasing the GHG emissions. However, the intermittency of renewable energy put a lot of stress on the electricity distribution system where a decentralised approach of the electricity generation could reduce the stress from renewable energy sources (RES).   This techno-economic study investigates the decentralisation of electricity generation through the Local System Operator (LSO) concept by creating a perfect prediction model where the LSO operates a local energy system in a multi-dwelling unit in Örebro, Sweden which is owned by the housing company ÖrebroBostäder (ÖBO). The local energy system will consist of one or more of the technical components; photovoltaic (PV) system for electricity generation, a battery energy storage system (BESS) to store and supply electricity to the facility, but also to increase the self-consumption and self-sufficiency and electrical vehicles (EV) which will be able to store and supply the building with electricity through Vehicle-to-home (V2H) application charging stations. The cost-benefit analysis of the energy system is made by parametric optimization of the sizes of the different components to maximize the Net Present Value (NPV) of the system after 25 years, and also by creating control and operation strategies of the BESS and the EVs in order to reduce the electricity consumption peaks of the facility load. A degradation model is used to mimic the capacity fade the batteries in the BESS and the EVs experience as time elapses, and different availabilities of EVs during the day is used in the case study to see the effect the driver’s habits and vehicle patterns have on the result.   The result of the case study shows that a 92.4 kWP PV system (yearly production of 710 kWh/kWP) without a BESS or any EVs will provide the highest NPV after 25 years which amounts to 145 420 SEK. Also, shown by the results, is that the BESS and EVs is not economically viable due to high costs, but combining a BESS with a PV system will make the energy system profitable up to 41 kWh BESS, if combined with the PV system size resulting in highest NPV. Whereas a system consisting of EVs will never be profitable no matter what sizes and what components are used in the system. The sensitivity analysis shows that decreasing the cost of the BESS and the EV charging stations for V2H application by 10 % will still not make the components profitable by themselves. However, it will make the BESS profitable for larger sizes when combined with a PV system, while only make the EV charging stations with the V2H services become a little less economically unfavourable.   The results also suggest that the charging and control strategy applied in the study is successful in its task of decreasing the electricity bill, but the investments are too high compared to the savings. Availability of the EVs has a large impact on the use of the V2H on the facility loads profile, where a high availability during the day will increase the usefulness of the EVs on the modelled multi-dwelling unit. Finally, the LSO concept might be viable in the future since it is profitable for a housing company to invest in flexible assets as BESS up to a certain size and if the LSO can aggregate enough of the housing company’s building portfolio it can help transforming the energy system from a traditional top-down approach to a bottom-up approach.