The cost of ancillary services in high PV penetration scenarios: the case of Spain

• High renewable penetration scenarios pose a challenge on Ancillary Services provision. • Properly equipped renewable facilities can provide voltage control and system inertia. • Ancillary services provision by storage and renewables results more efficient. • The Spanish case for 2030 has been used to illustrate the savings. Renewables should reach a 42.5 % share of total energy consumption by 2030 to meet the EU agenda, which translates to 75–80 % of the electricity generation mix for intermittent renewable resources (wind, solar…). In this context, running out-of-merit thermal power plants just to provide ancillary services (AS) has undesirable side effects, namely: increased supply cost and CO2 emissions, and reduced renewables share in the mix. This article proposes a methodology to compare the impact of AS provision in future scenarios with high renewables penetration, mainly photovoltaics (PV), under two different alternatives: 1) AS fully provided by conventional power plants, as is done today; and 2) AS provided by renewable sources, according to marginal market criteria. The future scenarios are built considering the current generation portfolio plus additional wind, PV and battery storage facilities, all of them competing with the marginal thermal technology (combined cycles). The methodology is applied to the Spanish case, keeping in mind the revised National Energy and Climate Plan for 2030. In conclusion, a series of recommendations are made regarding ancillary service provision and storage deployment.