Techno-economic analysis of PV and energy storage systems for Swedish households

University essay from KTH/Kraft- och värmeteknologi

Author: Alia Amber Ahmed; [2020]

Keywords: PV systems; Energy storage; STandUP;

Abstract: As more countries progress towards renewable energy, intermittency in the power system is causing an unreliable power supply. Flexibility solutions from prosumers, which both consume and produce electricity, is one solution to provide stability to the power system. Households with both PV and energy storage are studied for this purpose in this thesis where the following flexibility services for both a household and the electricity grid of Sweden are studied: Increasing PV self-consumption, peak shaving, energy arbitrage at the day-ahead electricity market and providing the frequency regulation reserves FCR-N, FCR-D, aFRR and mFRR. Each house is assumed to have a 10 kW PV capacity and a battery capacity of 7.68 kWh. The services are studied in the software HOMER Grid and are modelled in different scales to see how the load in different aggregated levels affect the services. The case studies are a single family house, an overloaded transformer, an energy community and on a national scale. For the aggregated case studies, the potential capacity for PV will be based on the existing Swedish policies and the number of energy storages will be inspired by one the leading countries in Europe in energy storage installations, Germany. The results showed that for a single household the self-consumption and self-sufficiency increased the most with an addition of a battery. The battery was most efficient in peak shaving and reducing the overall electricity cost when the electricity fee targeted both the electricity consumption during peak hours and the monthly peaks. With this price scheme, the payback time of the battery and PV system is around 14 years. However, when the electricity fee is only targeting the electricity consumption during peak hours, the results showed that the monthly electricity demand peaks actually increase with an addition of a battery. For the aggregated case studies, it showed that decentralized batteries are not as effective in decreasing the electricity demand peaks if the peak lasts more than a few hours. On a national scale the results show that 20% of the aggregated batteries capacity is sufficient to provide around 70-100% of each of the frequency reserves individually. The highest savings are gained for the households when both the primary frequency reserves, FCR-N and FCR-D, are provided by the aggregated batteries together with increasing the PV self-consumption, peak shaving and energy arbitrage. The battery payback time is then reduced to 11 years. Based on a sensitivity analysis, the costs that affects the battery payback the most are the investment cost and the power fee.

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