The ability to transmit power produced by renewable energy sources from one country to another using so-called ‘interconnectors’ is expected to become a key part of European energy markets in years to come, but doing so is technically challenging and raises a number of legal, regulatory and financial issues.
Agreements have already been reached on a number of interconnectors between European countries, most using dedicated, purpose-designed and built infrastructure, but a project that is getting underway in the Netherlands is taking a different approach, and will examine the feasibility of using infrastructure that is already part of an offshore windfarm, rather than building a dedicated interconnector to distribute power generated by renewables.
Over the next four years, a consortium of nine organisations will investigate how they might help reduce the cost of energy generated by offshore wind by developing an innovative type of electricity infrastructure in the North Sea.
At the end of 2012, the Dutch government provided €2 million for the innovative ‘plug socket’ project, having set itself a target of achieving 16 per cent renewably-generated energy by 2020. Wind energy generated at sea is seen as an essential contributor to meeting this target, but to achieve this goal, it will be essential to reduce the price of offshore wind.
The consortium consists of Nuon/Vattenfall, Liandon, ECN, RoyalHaskoningDHV, Groningen Centre of Energy Law of the University of Groningen, Delft University of Technology, DC Offshore and Energy Solutions, with Grontmij acting as project co-ordinator. Over the next four years, until December 2017, the consortium will investigate the feasibility of this new kind of electricity infrastructure for the North Sea, and examine technical solutions, changes to international legislation and regulations that might be required, and new financing models.
At present, each European country has its own, independent electricity infrastructure, but by combining the individual infrastructures via an interconnector, it is anticipated that the cost price of energy generated by renewables will fall.
Interconnectors have the ability to make power from offshore wind available when and where it is needed, across international boundaries, but dedicated interconnectors will be expensive. By developing a different kind of infrastructure, the consortium of companies hopes that offshore windfarms could be directly connected to the international electricity grid.
Speaking to OWJ in early February, representatives from Grontmij and Nuon provided an insight into how they are going about the project. As Marc Kreft, the consortium leader at Grontmij explained, in addition to knowing whether such radical, low-cost electricity infrastructure is technically feasible, it is important to know whether it is feasible financially, and to examine issues such as whether there is a firm business case for the concept, and who would actually own and operate the assets that form part of the interconnector. This being the case, the project has been broken down into a number of discrete work packages. Although there are no UK-based companies involved, the project is examining the feasibility of an interconnector using infrastructure in offshore windfarms in the waters of the Netherlands and the UK.
Work package 1 will focus on the technical feasibility of the concept, particularly the kind of multi-terminal high voltage direct current (HVDC) grid that would be required; other work packages will focus on finance, the regulatory framework, and related issues such as the role that new types of compact offshore substations might play in the new infrastructure.
As Martin Ars, who is leading the project at Royal Haskoning, explained, the use of HVDC technology is well understood. The major benefits of using HVDC are that, compared with the alternatives, it can help increase transmission capacity and reduce transmission losses.
However, to date, the technology has been limited to connecting two terminals. There has been little demand for multi-terminal HVDC systems. Now, however, researchers are looking at multi-terminal HVDC as a potentially competitive solution for the interconnection of offshore windfarms into national/international grids. By the end of the project, said Mr Ars, the partners undertaking it hope to have a much clearer idea of what is technically feasible, and what kind of technology would need to be built into offshore windfarms in future in order to enable them to form part of such a low-cost interconnector.
In a related development, recent weeks have also seen what has been described as “a major breakthrough” in efforts to integrate renewables into the European electricity system and develop the kind of very high voltage direct current grids that will be required to do so.
In February, Alstom Grid confirmed that it had achieved what it described as “the best performance ever seen” in an HVDC circuit breaker while testing a prototype at its facility in Villeurbanne, France. In less than 2.5 milliseconds, the HVDC circuit breaker interrupted currents exceeding 3,000 amperes.
The tests were conducted as part of utility company Réseau de Transport d’Electricité’s (RTE’s) demonstration activity on the architecture and technology for DC power grids within the Twenties large-scale demonstration project, which is supported by the FP7 programme at the European Commission.
“In the context of the energy turnaround, these tests, led by RTE, contribute to the development and implementation of new technology which will facilitate the integration of renewable energy sources into the European electrical grid,” claimed Alstom.
“This technological achievement is excellent news for the entire electrical engineering community, and a considerable advance in our industry,” says Alstom Grid president Grégoire Poux-Guillaume. “The direct current circuit breaker is a key element in building super grids, both onshore and offshore. It will help to increase the share of renewable energy on the grid.”
The circuit breaker is a key element of power network protection in the event of a short circuit. Well known in AC connections, the technology is required to perform 10-20 times faster if it is to be applicable to direct current systems.
Operators increasingly use direct current to guarantee that power is carried efficiently over long distances or to stabilise the grid as it is confronted with a growing supply of power from variable sources. Circuit breakers are not necessary for direct current transmission line connections between two points. However, having a circuit breaker is vital for protecting complex so-called ‘meshed’ grids that will, in the near future, require the interconnection of several points. The challenge is to avoid failures and blackouts, by cutting the current as fast as possible, isolating the fault from the rest of the grid.
Alstom said the tests it is undertaking will continue until the summer of 2013 as part of the Twenties project. The Alstom Grid team is then planning to pursue the qualification of the technology via another new milestone: interrupting a 7,500 ampere current at 180kV.
DNV research unit to focus on grid technology
DNV has announced that it is to open a research unit at DNV Kema’s headquarters in Arnhem, the Netherlands, which will focus on the development of smart grids and ‘super grids’. Smart grids and super grids are key elements and a prerequisite to integrate large-scale renewable energy in the future energy system.
The opening of the research unit was announced by Bjørn Haugland, chief technology officer at DNV and a member of the supervisory board of DNV Kema, during a panel debate on energy transition at the World Future Energy Summit in Abu Dhabi.
“By opening up a strategic research unit for smart grids and super grids in Arnhem, DNV is preparing the practices and tools we need to meet the growing demand as well as facilitate the integration of large-scale renewable energy to the grids,” said Mr Haugland.
“Smart grids and super grids are essential for the further development of our future energy system,” said DNV, noting that in November 2012, DNV Kema had announced a €70 million investment in the expansion of its high power laboratory in order to create what it claims is the first lab in the world able to undertake the kind of testing that new grid infrastructure will require.
Germany and Norway sign interconnector deal
The Norwegian grid operator Statnett, KfW Ipex-Bank, and TenneT TSO, the transmission system operator for the German North Sea region, have concluded a co-operation agreement to develop and construct a subsea interconnector between Germany and Norway. The high voltage direct current (HVDC) interconnector will enable energy to flow between Germany and Norway and help improve the distribution of renewable energy sources between the two countries. “The integration of the Norwegian and German electricity markets … will ensure greater grid stability in the two countries, increase market efficiency, and stabilise prices,” said the parties to the agreement.
The interconnector project will require an investment of approximately €1.5-2 billion. The agreement provides for a 50:50 partnership between Norway and Germany. State-owned Statnett will own 50 per cent of the project. On the German side, KfW and TenneT will jointly own 50 per cent via a newly established project company. The target is to commence operation of the cable in late 2018.
“We have been preparing this subsea interconnector between Norway and Germany for two years,” said Martin Fuchs, chairman of the board of TenneT TSO. “It is a good development for the integration of wind power and a vital contribution to the German Energy energy transition. We are pleased with the participation of the German KfW Ipex-Bank. Statnett, KfW and TenneT combine the innovative power, financial solidity and technical leadership needed for a project of this scale.”OWJ
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