On the temporal granularity of joint energy-reserve markets in a high-RES system.

• Study of the temporal granularity of joint energy-operating reserve markets. • Analysis based on state-of-the-art unit commitment model accounting for uncertainty. • Benefits in terms of cost-efficiency and scarcity on operating reserve markets. • Case study reveals potential total operating cost reductions of 1.5–1.8%. The cost-efficient integration of variable renewable power (vRES) requires adequate operating reserve and energy markets. This paper focusses on the benefits of increasing the temporal granularity of joint energy-operating reserve markets in a case study on two high-vRES systems. Specifically, the impact of the frequency (i.e., how often reserves are sized and procured) and the resolution or contract duration (i.e., the length of the sizing and procurement blocks) is isolated by comparing year-long unit commitment and economic dispatch simulation results. We optimize the power system's operation in consecutive stages: scheduling of generation units with procurement of reserves, intra-day adjustments of generation schedules and real-time activation of flexibility to compensate for imbalances. The results suggest that dynamic and more frequent sizing, limiting the reserve procurement contract duration and a higher procurement frequency allow reducing the total operating cost by 1.5–1.8%, while eliminating scarcity on reserve markets. These design changes facilitate the integration of intermittent renewables in reserve markets. Finally, some challenges following the proposed market design changes are highlighted. [ABSTRACT FROM AUTHOR]