On sizing of Battery Energy Storage Systems for independent multi-ancillary services in AC grids

Battery Energy Storage Systems (BESS) arise as a crucial technology to transition from conventional/centralized to decentralized/eletronized power systems. A multi-step BESS sizing procedure for independent multi-ancillary services is a highly demanded tool that supports prosumers’ and utilities’ decision-making to pursue attractive investments that meet the intended technical requirements. Thus, this paper proposes a novel multi-step methodology for BESS sizing, evaluating economic viability, utilizing real-world mission profiles, and estimating Li-ion battery bank degradation, based on three ancillary services: self-consumption (SC), energy time-shift (ETS), and islanded (IS) operation. The methodology is applied to four case studies in the SC and ETS modes, evaluating the effects of ( i ) photovoltaic (PV) power plant size, ( i i ) fixed PV capacity, ( i i i ) battery size trade-offs, and ( i v ) grid power charging. Results showed that the sized BESS performing ETS, charged by a 250 kW PV system, with a capital expenditure of $218,806, achieved a net present value of $417,739, an internal rate of return of 18.55%, and a discounted payback period of 9 years. The system maintains an average state of charge of 75%, with 6.4% of the time unable to provide ETS due to battery constraints. In islanded operation, the same system provided 10 h of autonomy during grid outages, which is sufficient to support the facility. It is also shown that sensitivity analysis in promising scenarios, such as energy tariff increases and BESS cost reductions, further enhances the technical and economic feasibility of the system. • Proposed multi-step BESS sizing procedure for independent multi-ancillary services. • BESS sized for ancillary services such as energy–time shift, islanded, and self-consumption modes. • Methodology employs real-field mission-profile data, ensuring its effectiveness in addressing real-world sizing challenges. • The lifetime of Li-ion batteries is assessed comparatively for several case studies, considering the damage caused by cycling and calendar aging mechanisms. • Techno-economic viability of BESS operating in energy–time shift mode is evaluated through economic metrics: net present value, internal rate of return, and discounted payback. • Although economically viable, discounted payback of 9 years and internal rate of return of 18.5% suggest that financial metrics are not as attractive as other investments (i.e., PV systems). Until a better technology maturation in the market, BESS investment cannot be motivated only by economics yet, being also justified by technical reasons.