News that the latest transmission system interconnector – the Nemo Link between the UK and Belgium – has gone live marks another major step on a European-wide electricity transmission system.
Interconnectors have become possible due to developments in high voltage solid state electronics. These allow the efficient transfer of power via high voltage direct current (HVDC) cables. A converter station at each end transforms the AC (alternating current) power into DC and vice versa, ensuring the link supplies synchronous energy as required.
The UK already has several large international power connections in place, with a collective capacity of some 4 GW. For example, there is already the 2 GW of interconnector capacity between the UK and France, a further 1 GW to the Netherlands with BritNed and two connections to the island of Ireland of 500 MW each.
The benefits of a fully interconnected European electricity system are well known. For instance, during the summer heatwaves that regularly hit mainland Europe, France has a problem. The country supplies much of its electricity from nuclear reactors and extracting sufficient cooling water from its rivers threatens significant ecological harm. As a result, power output from French reactors is commonly cut and, this July, French electricity giant EDF again reportedly closed down reactors at two plants in the south of the country.
To meet its domestic demands, France imports power through the 2 GW Interconnexion France-Angleterre (IFA). This two way joint venture link between the French Transmission Operator RTE and the UK’s National Grid was commissioned in 1986 and benefits both French and UK consumers.
THE CHANGING ROLE
Today though, the role and the need for interconnectors is growing in the light of soaring renewable energy capacity. Based largely on variable output wind and solar power, a major challenge for transmission system operators is maintaining grid stability when a significant proportion of generating capacity is not always available.
Christer Gilje, VP of corporate communications for Norwegian TSO Statnett, explains: “In Norway, the electricity system is based very much on hydro power. In average years, we will have a surplus of hydro power, but some years might be dryer with less rain and snow. That means we need more electricity to heat our houses, and then we need to import extra electricity. Interconnectors have been very important for us.”
He continues: “The second driver is that we’re also increasing our capacity for renewable production. Norway now has more wind power than before and it’s still increasing, so we get more of that intermittent renewable power production, which means that when you produce it, you need to use it. However, the value of this energy increases when you connect to new markets, because when you see a new wind power plant and the power is not needed in Norway or the closest neighbouring country, you might sell it to Germany or the UK when you are connected to these markets. The value of Norwegian power production capacity, both new wind power and other new renewable power, as well as the existing renewable power, will increase a little bit when you connect to new market.
“The third reason for building interconnectors is that on both sides there will be more intermittent power production. With Norway, very often we can help out balancing by using hydro power, because we can leave the water in the reservoir and basically import wind power or solar power. When there’s a need on the other side, we can start running the hydro power plant and export hydro power to Germany or the UK or Netherlands or Denmark.”
It is this capability for continental grid balancing, coupled with a number of technical developments, that have prompted and enabled long distance bulk power transmission systems to flourish. Consequently, several additional interconnectors have been commissioned with additional links under construction.
BULDING NEW INTERCONNECTORS
Nemo Link is National Grid’s third operational interconnector to Europe and the latest to begin operations. Stretching 140 km (80 miles) from the industrial zone in Herdersbrug near Bruge on the Belgian coast to Richborough in Kent, south-east England, Nemo Link has a 1 GW capacity and was developed at a cost of some £600 million. Siemens supplied the converter stations and Sumitomo the cables (pictured, left).
Expected to operate for at least 25 years, project partners include National Grid Interconnector Holdings and Elia, Belgium’s grid system operator. In 2010, Elia expanded its activities in Europe and acquired the German System Operator 50Hertz in cooperation with Industry Funds Management (IFM). It is now one of the top five transmission system operators in Europe.
July saw the initiation of spot market trading through the Nemo link in Central West Europe (CWE) bidding zones, the result of the cooperation of 18 parties, including nine TSOs during two years of work and months of extensive testing. For the Belgian Bidding Zone, EPEX Spot SE and EMCO/Nord Pool are now active for the Day-ahead Market Coupling.
After a 10-year development and construction phase, ultimately, the Nemo Link is part of a series of measures that will help to establish an integrated European grid where surplus renewable energy is traded internationally.
Completion of Nemo Link’s marks a crucial stage in the ongoing integration of the European power grid, where excess power can be traded at favourable prices across the whole of Europe. Interconnections contribute not only to a sustainable energy system, but also to a reliable, affordable energy system.
Commenting on the development, Chris Peeters, CEO of Elia, noted: “The commissioning of the Nemo Link, combined with that of the ALEGrO connection, scheduled for next year, will significantly boost our energy exchange capacity and position our infrastructure at the heart of Europe’s future electricity system.”
The UK is also constructing additional interconnectors. According to electricity regulatory Ofgem, a further three links are planned with France, including ElecLink, IFA2 and FAB Link, which have a combined capacity of 3,400 MW. A second link with Ireland is anticipated and the Viking Link will connect the UK with Denmark in a venture between National Grid and Energinet.dk.
National Grid recently announced that it had been given financial approval for the construction of the Viking Link. In addition, North Sea Link (NSL) is a joint venture between Norway’s TSO Statnett and National Grid that will see a 1400 MW two-way interconnector join the two nations.
This is being built between Kvilldal in Norway to Blyth in the UK. Again, technical improvements in HVDC systems are improving the economics of interconnectors. “The HVDC technology has made it possible to increase the capacity for these interconnectors. The first ones that we made in the 1970s were 215 MW, the one to the Netherlands completed in 2008 and to Denmark in 2014 had a 700 MW capacity and then we are building two with a 1400 MW capacity. So we see that the capacity is increasing and then we can import and export more through one subsea cable of this kind,” Gilje comments.
In building new links, there are also other considerations for the system operators to manage. Gilje says: “As the system operator, we always have to say what it would mean for the Norwegian power system and the Norwegian national grid if we connect more interconnectors between Norway and other countries. You will always have to consider the physical exchange of power when you start up a new interconnector and you suddenly have 1400 MW going out of the national grid in one big set point. Sometimes it will change between exporting and importing, again there could be difficulties for the system if you change the direction of the power too often and too quickly. That’s where you get regulations covering things like ramping rates so that you can adjust the rest of the power grid every time you change the direction of the interconnector.”
Nonetheless, interconnectors do have a vital role to play in reaching European climate change goals. As Gilje explains: “Since it goes both ways, the more interconnectors you have between the different European countries, the less you need to keep security of supply within each country where you probably would need to keep so many power plants running that have carbon emissions. Instead you send the renewable energy between different systems and it becomes greener and more efficient.
“I think it’s important to note that as the UK gets more and more interconnectors, it’s possible to get away from keeping those coal and gas-fired power plants that the UK wants to phase out and to have more green and renewable energy in the system.”