No time to lose: equipping Europe's future electricity grid

What will the future grid look like, which technologies are most promising for raising transmission capacity and flexibility, and how can more energy from remote wind and solar farms be brought in? Those were the questions at “Renewing the EU electricity grid: the Best Paths towards energy transition”, the final conference of the EU project BEST PATHS, held in Brussels on 20 September 2018. Organised by Greenovate! Europe, it brought around 120 experts from across the continent together with policy makers to discuss how to upgrade the European electricity grid.

Project coordinator Vicente González López of Red Eléctrica de España said: “The technologies developed in Best Paths will have a significant role in the evolution of the transmission grid, ensuring the grid is ready to cover the market actors’ requirements in the new energy paradigm at an affordable cost. Investment today in the future grid is mandatory to accelerate the transition process. All relevant actors: policy makers, regulatory authorities, transmission system operators and utilities, manufacturers, researchers and citizens should understand that there is no time to lose if Europe wants to continue leading the transition process worldwide.”

BEST PATHS was the largest energy research project financed under the EU’s Seventh Framework Programme for Research, Technological Development and Demonstration (FP7). It ended in September 2018 after four years, having united 38 partners around five large-scale demonstrations that tested the technical feasibility, costs, impacts and benefits of new grid technologies. The demonstrations focused on the move from HVDC lines to HVDC grids, on upgrading and repowering existing AC parts of the network, and on fitting superconducting high power DC links into a meshed AC network.

Three parallel workshops presented the latest results.

Workshop 1: HVDC converter technologies

The session asked what the main interoperability problems are, how the partners proposed to overcome them, and how converters can be adapted for offshore wind farms.

In Demonstration 2, the interoperability of converters from several vendors was assessed systematically and adaptations were proposed. Shortly before the conference the partners had shown the results of pioneering tests on high-voltage AC/DC converters supplied by different HVDC manufacturers.

For offshore wind farms, Demonstration 1, led by the Spanish utility Iberdrola, tested three converter prototypes in the 50 kW range, built to emulate modular multilevel converter technology. The results pointed to the network topologies best suited to connecting the larger offshore wind farms still to be built.

In Demonstration 3, an innovative industrial-size converter was taken from concept through design, construction and testing. System studies of multi-terminal operation were also carried out, looking at smart control strategies and at the costs and benefits of completely revamping an existing Italian link.

The session was chaired by Olivier Despouys of RTE, Réseau de Transport d’Électricité.

Workshop 2: cable technologies

Which cable technologies are most promising, which materials perform best in HVDC cables, and what can superconducting cables do for electricity transport?

The workshop presented new ways to upgrade multi-terminal HVDC links. In Demonstration 3, the Italian transmission system operator Terna took the SACOI link between Sardinia, Corsica and mainland Italy as its real reference case, and used it to develop improved extruded submarine and land cables for very high voltages and depths, taken successfully up to qualification tests.

In Demonstration 5, the partners designed a superconducting cable system including high-voltage insulation and terminations. The wires can carry 500 times more current than copper wires, and the system can transport up to 3.2 GW. It was the first high-voltage superconducting cable system designed to run on direct current, whereas all existing projects used alternating current. The superconductor is magnesium diboride, which is very economical to produce.

Christian-Eric Bruzek of Nexans chaired the session.

Workshop 3: overhead lines

The third workshop looked at new ways to repower existing high voltage lines and improve their design, operation and maintenance.

New conductor technologies were only part of the answer; existing overhead lines also had to be improved and repowered. BEST PATHS Demonstration 4 worked on new features and repair methods for conventional lines, among them insulated cross-arms, high temperature low sag conductors, a composite tower, dynamic line rating and live-line working methods.

In Demonstration 3, first-of-a-kind high-performance HVDC conductors for overhead lines and new insulators were developed and tested successfully in the field.

The chair was Matthias Müller-Mienack of GridLab, for 50Hertz.

After BEST PATHS

The closing session turned to incentive schemes that could help the new grid technologies, the areas where interconnected grids and their components need new standardisation procedures, and the partners’ overall recommendations. Antonio Iliceto of Terna, chairman of the BEST PATHS consortium, presented a set of recommendations meant to ease the deployment of the technologies developed in the project.

Each demonstration had earlier held its own stakeholder workshop:

• 11 May 2017, Trondheim (Norway): real-time simulation of large offshore wind farms and their interactions with power grids;
• 5 April 2018, Budapest (Hungary): innovative repowering of AC corridors;
• 9 May 2018, Codrongianos (Italy): upgrading multi-terminal HVDC interconnectors;
• 6 June 2018, Paris (France): maximising multivendor interoperability in HVDC systems;
• 5 July 2018, La Spezia (Italy): superconducting cables for very high power transmission.

The conference presentations, agenda, photographs (by Vivian Hertz) and the project recommendations were published by the project.

The SACOI link used as the cable testbed is being replaced: SACOI 3, rated at 400 MW, is under construction with completion planned for 2029, and the superconducting design from the second workshop is explained on the Demonstration 5 page.