The growing share of renewable power generation along with increasing demand for electric mobility changes electricity systems around the world. Challenges include unforeseen and costly imbalances created by fluctuations in renewable power supply that threaten grid stability as well as surges in demand from electric vehicles that lead to load curtailment and decrease transformer lifetime. Grid energy storage has the potential to address these issues by effectively buffering supply and demand and thereby generating significant welfare gains. In spite of these benefits and plummeting battery prices, grid energy storage remains a costly investment, and the complexity involved in operating storage assets adds to this.
In their article “The Value of Coordination in Multi-Market Bidding of Grid Energy Storage”, forthcoming in Operations Research, Prof. Nils Löhndorf (LCL) and Prof. David Wozabal (TU München) consider the problem of optimal storage operation in an electricity market with a day-ahead auction and a continuous intraday market – which is the standard market design in Europe.
The authors show that owners of storage are better off by coordinating trading activities across both markets. However, coordination is not current practice, due to the inherent complexity of the underlying decision problem. Rather, decision-makers treat these markets as independent. To address this shortcoming, the authors develop a mathematical optimisation model for day-ahead bidding and hourly intraday trading along with a corresponding stochastic price model. The new model enables energy traders to calculate day-ahead bids that accounts for the option to rebalance their portfolio in the continuous market. The model also provides investors in storage with a more accurate picture of the value of storage by considering both markets simultaneously.
In a case study with real-world data, the authors find that coordination is most valuable for large storage assets, like pumped-hydro storage. For small assets, like battery storage, participation in the day-ahead auction can be viewed as optional and focusing on intraday trading alone is likely the best strategy.