The potential benefits of transmission hubs and modular grids for the transmission of electricity generated from renewables were both in focus in early 2017
Late March 2017 saw transmission system operators (TSOs) TenneT in the Netherlands and Germany and Energinet in Denmark sign an agreement for the development of a large-scale renewable European electricity system in the North Sea. The so-called North Sea Wind Power Hub has the potential to supply 70–100 million inhabitants of Europe with renewable energy by 2050. At about the same time, the board of directors of Elia approved investment in an electricity plug or modular offshore grid (MOG) in the North Sea that they believe will be of strategic importance for the future of Belgium in terms of its participation in the development of renewable energy in the North Sea.
Mel Kroon, chief executive officer of TenneT, and Torben Glar Nielsen, chief technology officer of Energinet, said the North Sea wind power hub would act as a connection point for thousands of offshore wind turbines. They aim to build the hub in a shallow-water location in the North Sea with optimal conditions for the transmission of electricity to European consumers.
“Building one or more artificial islands in the middle of the North Sea sounds like a science fiction project, but it could actually be a very efficient and affordable way for North Sea countries to meet the future demand for more renewable electricity,” said Mr Nielsen, noting that a location such as Dogger Bank has many advantages, not least that it could significantly reduce transmission costs.
The TSOs anticipate that the North Sea hub could transmit electricity from wind energy to the Netherlands, Denmark, Germany, the UK and Belgium. They anticipate that the transmission cables from offshore windfarms would simultaneously function as interconnectors between the energy markets of the aforementioned countries. Apart from transmitting wind energy to the countries in question, these ‘wind connectors’ will enable them to trade electricity.
Having signed the agreement, TenneT and Energinet plan to spend “a few years” investigating the potential of one or more power islands. If the TSOs decide to go ahead with the project, a power link island could be developed by 2035.
Elia says the electricity plug or MOG will connect offshore windfarms in the North Sea such as Rentel, Northwester 2, Mermaid and Seastar to the Belgian grid in a cost-effective and reliable way and create opportunities for future offshore wind development and interconnections with neighbouring countries of the type also envisaged by the TSOs.
The modular offshore grid includes an offshore platform to provide connections to the new windfarms. This will be located approximately 40 km from the coast of Zeebrugge in Belgium. Three 220 kV submarine cables will link the platform with the Stevin substation in Zeebrugge, so that wind energy can be injected in the Belgian grid. The total installed capacity of the four windfarms is expected to be 1.03 gigawatts.
Chris Peeters, chief executive officer of Elia, said “This is a very important step for Elia. The modular grid is a first building block of a future North Sea grid and will expand our activities in Belgium from onshore towards offshore. A modular grid such as this one can generate opportunities for the economy, help to develop new technology and lead to the creation of high-quality jobs.”
The MOG is due to enter service in Q3 2019. Elia has already undertaken seabed survey campaigns to investigate soil conditions along the cable route and at the platform location. Detailed design of the offshore platform is currently being undertaken, and other tenders for the main construction contracts are ongoing. The estimated total investment is approximately €400M (US$428.9M), which includes construction work by Elia and the acquisition of assets built by Rentel. Once the modular offshore grid is constructed, Elia will own and operate the offshore assets.
“The benefits of the modular offshore grid compared to a direct connection are multiple,” said Elia. “It allows windfarms connected to the MOG to inject wind energy directly into the Belgian grid, even when there is a loss or failure of one of the offshore cables. Because of its modular character, construction can be phased and synchronised to the different time schedules of individual windfarms. It is also more cost-efficient and environmentally friendly and will facilitate a reduction of the total cable length by 40 km and, as a result, reduce potential disturbance of the seabed and marine life.”