Wind power and solar PV technologies can provide grid support services (GSS) for frequency, voltage and certain functions in system restoration (i.e. ancillary services provided by DER). The REserviceS project confirmed that variable renewable energy sources like wind and solar PV generation (VAR-RES) meet most of the capability requirements for delivering such ancillary services, as prescribed in Grid Codes. Where enhanced capabilities would be required, technical solutions exist, but are not used today because of economic reasons due to additional costs, of which REserviceS has made an assessment. While in some countries financial incentives for VAR-RES with enhanced capabilities exist, this remains the exception rather than the rule in Europe. Appropriate operational and market frameworks are therefore needed for enhanced participation of VAR-RES in GSS.
The need for VAR-RES’ participation in GSS provision, especially at high penetration levels, depends on the power system characteristics (for example its size and resilience) and how VAR-RES are integrated into it (for example its dispersion and technical characteristics). As GSS come with a cost, requirements for generator capabilities and service provision should demand only what is needed by the system to avoid excessive system costs. Importantly, REserviceS analyses found that frequency management can be adequately and economically achieved with only a fraction of all installed VAR-RES generators participating in frequency support.
Preparing for future electricity systems with large shares of VAR-RES requires detailed studies and simulations to make well-founded estimates of the needs and technical requirements. Moreover, detailed and clear specifications, as well as market designs and products taking into account the characteristics of VAR-RES, are crucial for their participation in GSS provision.
An increase of VAR-RES means that generating capacity is increased in Distribution System Operator (DSO) networks. Hence, DSO/TSO (Transmission System Operator) interaction will also be increasingly important in the future with large shares of VAR-RES. DSOs in particular will have an increasing role in the transition of electricity networks and increasing involvement in defence and restoration plan. Revised governance for DSO/TSO interaction to properly coordinate frequency and voltage support, as well as restoration services provided by VAR-RES, is needed.
The REserviceS recommendations provide technical and economic guidelines for the design of market mechanisms that would enable power systems in Europe to function safely, reliably and cost-efficiently with high shares of variable renewables which can provide GSS themselves.
The recommendations are primarily addressing the European Network of Transmission System Operators for Electricity (ENTSO-E), national TSOs and DSOs, market operators, the EU Agency for the Cooperation of Energy Regulators (ACER) and national regulators as well as the European Commission and national energy policy makers.
If the political goal of achieving a truly integrated Internal Energy Market goes beyond the energy-only market model, the roll-out of GSS market models throughout the EU must be considered. Therefore, the REserviceS project recommendations need to be taken into account, in particular in the revision of the EU-wide Target Model and more specifically in the relevant network codes as well as in national grid connection requirements.
They can be downloaded online at www.reservices-project.eu and are divided into: recommendations for policy and electricity market design, EU network codes and national grid codes, and research and technological development.