Providing Stacked Balancing Services using Wind-Storage systems

Abstract

In order to decarbonize the electricity grid, renewable energy sources must be utilised in con- junction with energy storage to provide ancillary services, which maintain electricity supply quality, reliability and restorability, whilst remaining aordable. Due to a lack of knowledge about the potential of stacking UK ancillary services and electricity markets to improve service aordability, this study of a wind farm with a co-located battery system compares the UK Black Start service, Firm Frequency Response static low frequency secondary and dynamic high frequency services, alongside the day-ahead market as sources of revenue, both provided individually and stacked, with all mismatches handled in the balancing market, to identify the most protable method of operation. A model of the wind farm - battery system power and energy ows is used to assess availability of Black Start and two Firm Frequency Response services, as well as operation in the day-ahead and balancing market, for a one-year period. Internal rate of return and levelized cost of electricity are used to measure nancial perfor- mance, with a weighted average cost of capital (WACC) of 7.75%. Is is found that no service or market provision is protable compared to the WACC, and the most protable method of operating the system is to sell all wind energy forecast on the day-ahead market, not using storage and not stacking services. The most protable method of providing the BS service is when stacked with the FFR static low frequency secondary service. The most protable method of providing either the FFR static low frequency secondary service or FFR dynamic high frequency service is alone, not stacked. The protability of stacks are most sensitive to the changing of BS requirements, although the protability rank order of stacks doesn't change. A single bad wind year has a very small eect on BS availability, and the eect of increased frequency deviations doesn't aect the stacks of FFR services due to limited income from FFR service energy provision compared to the balancing market or from FFR service availability.