During the three-year duration of the project, the 26 consortium partners, from ten member states of the European Union plus one associated member, have validated, through six real life demonstrations, various technologies that contribute to a greater and better integration of onshore and offshore wind energy into the electricity system and which demonstrate a greater efficiency of the system by achieving a reduction in: total generation costs, CO2 emissions and the risk of renewable energy dumping.

The Twenties initiative has had a budget of 57 million euros, of which 32 million have been funded by the European Commission under the Seventh Framework Programme for research, technological development and demonstration activities.

A technological innovation Project
The results of this innovative project have proven the technical feasibility of the six large-scale demonstrations carried out around three main axes: the capacity of wind power generation and aggregation of distributed energy resources of demand and generation to provide system services to the Transmission System Operator (TSO); the development of the offshore transmission grid in high voltage direct current (HVDC) to enable the safe incorporation of offshore wind power energy, and the application of new technologies regarding the transmission grid that will increase its flexibility and capacity to safely and predictably manage a greater amount of wind power production.

In the first case, the technical feasibility of providing voltage and frequency control services by wind farms, or through aggregation of distributed energy resources of demand and generation has been demonstrated. The financial viability of this initiative currently depends on the regulatory framework or the market model defined by the business plan associated with the provision of these services.

On the other hand, it was found that the development of the offshore transmission grid in HVDC is critical in order to integrate large amounts of offshore wind power and to offer new interconnection capabilities between electricity systems, although the structure and level of meshing depends on the evolution of CO2 prices and the cost of the various components of the HVDC grid itself. In this regard, the manufacturing of a prototype direct current circuit breaker with the capability to act in 2.5 milliseconds (about 20 times faster than the actual alternating current circuit breaker) is a very prominent technological milestone. Similarly, a new offshore wind turbine control system that manages a gradual disconnection of the wind farm in situations of excess wind has also been developed and tested, reducing by up to 70% the energy dumped in these situations.

Achieving greater flexibility in transmission grids in order to expand the capacity of wind power evacuation has been the aim of the third Twenties task force. In these demonstrations, a procedure for the management of the active elements of the transmission grid (HVDC links, transformers, phase shifters, etc.) has been designed in order to act in a coordinated manner when challenged by variations in this type of generation. Additionally, an overload controller has been developed, and put into service in Red Eléctrica's 220 kV grid, that is capable of distributing energy via alternative routes and avoiding congestion situations resulting from high wind production at specific points in the grid, allowing the electricity transmission system capacity to be used more efficiently, hence increasing control and safety and reducing costs.

Also, with the aim of increasing the flexibility of the grid, two alternative technologies to dynamically determine the actual capacity of transmission lines have been validated. The first of these calculates capacity through the use of devices that measure the conductor’s fundamental frequency of vibration, whilst the second, developed by Red Eléctrica, involves using a special Optical Phase Conductor (OPPC) which provides continuous direct measurement of the conductor temperature throughout the length of the line.

The results of these studies are integrated in a European study which assesses the potential economic and regulatory impact of the widespread application of validated solutions identified as necessary to ensure the adequate contribution of the transmission grid to reach the objectives of the European electricity system by 2020, in line with the objectives of the European Strategic Energy Technology Plan.