Ensuring flexibility requirements is an emerging issue in electricity economics and market analysis. In the context of increasing renewable penetration, flexibility requirements are expected to increase significantly. This paper focuses on flexibility requirements occurring on a daily basis over multi-hour timescale and the needed operating reserves. We extend the definition of capacity adequacy so as to incorporate the flexibility dimension and we propose the use of relevant metrics.
Moreover we make use of a unit commitment algorithm, mimicking the day-ahead and balancing market on hourly basis, throughout a wide range of scenarios. Flexibility service is quantified and its delivery is linked with operating maintenance costs and revenues in dayahead market. As flexibility is imperative from a security of supply perspective (public good) and no further remuneration is given to units, providing ramping services, a free-riding problem arises. We conclude that flexibility provision must be procured through capacity auctioning procedures, ensuring the supply of these.