Subsea cable launch begins integration of energy markets

The first subsea electricity cable between Britain and the Netherlands opened last week, starting the integration of the UK and European energy markets.

The 260km BritNed interconnector, a joint venture by National Grid and its Dutch equivalent TenneT, began operating on 1 April, allowing up to 1GW of power to flow between the two countries.

This is the first step toward a system that could allow Britain to make the best use of its growing supply of intermittent renewable energy, as well as helping to stabilise wholesale energy prices.

The connector will help to make intermittent renewable sources more financially viable

‘This will enable the sharing of renewable power and the maximising of its use, helping to make electricity more affordable, reliable and sustainable,’ said National Grid executive director, Nick Winser, at the BritNed launch event.

‘With wind, one of the biggest issues facing the European energy industry is intermittency. Interconnection is one of the key paths to solving that issue by providing back-up across Europe.’

BritNed takes the total transfer capacity between Britain and the continent to 3GW, adding to the 2GW of the England-France interconnector that launched in 1986.

However, the Dutch cable is the first to use a system to effectively sell energy as well as capacity, enabling power generated in one market to be sold in another and marking a step towards a single European energy market.

Construction phase

Building the high-voltage direct-current (HVDC) cable and two converter stations at the Isle of Grain in Kent and Maasvlakte near Rotterdam cost around €600m (£530m).

Around 24,000 tonnes of copper and lead was buried under the seabed in a zigzag route across the Channel in order to avoid large areas of shifting sand and take into account busy shipping lanes and 10 other undersea cables, including the UK-Europe gas pipe.

At its peak, the operation involved 450 crew members and 36 vessels, including some of the biggest cable-laying ships in Europe, said BritNed’s director, Bill Russell.

‘We used chain trenchers, ROV [remotely operated vehicle] launching to make sure they were laying the cable in the right area, and in the soft sand we used a mass flow excavator, which blows out high-pressure water to create a major trench in the seabed.’

On land, the company had to lay 1,200 foundation piles at the marshy Isle of Grain site and use a method known as sand compaction to stabilise the Maasvlakte site, which was reclaimed from the sea.

BritNed then constructed stations to convert alternating current from the grid to direct current for cost-efficient transportation (and vice versa), each with seven converters weighing more than 200 tonnes in total.

‘One of the biggest challenges was the size and scale of the equipment we were using, which all had to be imported from Germany,’ said Russell, commenting on the Siemens/BAM Nuttall converter stations.

Business model

BritNed also had to construct a business model, becoming the first UK business to use an ‘implicit’ auction process where it sells energy a day in advance of transmission, as well as ‘explicitly’ auction physical transmission rights up to a year in advance.

This system, run by trading firm APX-ENDEX, links Britain’s energy market to that of the already integrated central western European zone of France, Belgium, the Netherlands and Germany.

Under this ‘market coupling’ arrangement, electricity is sold from the cheaper market to the more expensive one, which helps to bring wholesale prices closer together.

UK prices are not consistently higher than those of its continental neighbours so wholesale energy costs could go up as well as down if Dutch electricity is more expensive.

The connector would also allow Britain to sell unused energy, such as wind power generated at times of low demand, helping to make intermittent renewable sources more financially viable.

Price convergence

But the relatively small capacity of the BritNed cable will limit its impact and the main aim of linking European energy markets is price convergence and stability, helping protect all countries by securing energy supplies.

The European Council recently set 2014 as the target date for a fully interconnected single European energy market. Planned cables between the UK and France, Belgium and Norway are expected to increase transmission capacity to more than 10GW by 2020.