This report presented an assessment of energy storage opportunities for Gotland, primarily focused on the potential integration of local energy storage systems to minimise RES curtailment, which is mainly caused by the limited power capacity of the mainland interconnection.
The assessment has been structured around two main activities:
- Evaluation of the feasibility of establishing a seawater PHS on the island.
- Sizing of an energy storage system to reduce RES curtailment resulting from limited interconnection power capacity.
Regarding the first activity, a detailed analysis was conducted to explore the feasibility of a seawater PHS on Gotland. A potential location was identified; however, due to the limited elevation of the island, only a small-scale energy storage (in terms of both power and energy capacity) could be implemented. A significant CAPEX exceeding EUR 100 million for a 10 MW/100 MWh PHS was also found. Due to its limited scale, such a system would mostly be able to operate on a daily or weekly basis to reduce RES curtailment. It would not enable participation in profitable markets such as ancillary or energy arbitrage. Moreover, it would not function as a real long-duration energy storage to overcome seasonal imbalances on the island.
Regarding the second activity, the calculations were based on the previous studies using 2014-2017 data and adapted to future scenarios that considered a potential new HVDC mainland connection (currently in the pipeline) and its increased maximum power capacity. The proposed values should be regarded as preliminary estimates, and primarily aimed at mitigating hourly wind curtailment for potential surpluses of around 240-250 MW of RES. Once the number of “prolonged/subsequent hours” of curtailment of WT/RES is assessed, the proposed values could be proportionally calculated according to the number of hours/amount of wind power or wind energy curtailed.