Testing has begun on the world’s longest undersea electric cable, stretching 720km between southern Norway and the north of England. The North Sea Link is the seventh interconnector to the UK mainland, with a further four in construction or planning phase, increasing the ability of the various countries to exchange electricity, which will be particularly useful in balancing the intermittency of renewable energy production (although Norway’s large portion of hydroelectricity does not suffer significantly from intermittency). The North Sea Link, a joint venture between National Grid and Statnett, is capable of carrying up to 1.4GW of power, and will begin commercial operation in October this year. Construction was a particular engineering challenge given the rough seas off the coast of Norway.