Impact of 15-day energy forecasts on the hydro-thermal scheduling of a future Nordic power system

One of the most promising ways of de-carbonising the energy sector is through increasing the amounts of inherently uncertain variable renewable energy (VRE) generation in power systems.
Typically, stochastic energy system studies have focused solely on the day-ahead horizon of 36 hours ahead of time, while studies about hydro-thermal scheduling and expansion planning often neglect VRE uncertainty entirely.
In this work, the potential benefits of extending the horizon of VRE forecasts on the operation of hydro-dominated power systems was studied using a future Nordic system case study.
15-day ensemble weather forecasts were processed into realistic VRE forecasts up to 348 hours ahead of time, and their impacts on power system operations were simulated using stochastic unit commitment and economic dispatch optimisation.
While decreases in total yearly operational costs as well as hydropower spillage and wind power curtailment were observed until forecast horizons up to around 132--156 hours ahead of time, the relative cost reductions remained rather insignificant at around 0.20--0.35 \% and 0.10 pp respectively.