China is to get its first high-voltage direct current offshore wind substation.

China has committed heavily to developing its offshore windpower capacity and plans to have 5 GW installed by 2020 – last year alone it installed almost 1.2 GW. This brought the cumulative total installed capacity to nearly 2.8 GW, third globally behind the UK and Germany.

However, the country faces a challenge: all the promising wind farm sites within 10 km offshore have already been exploited. To boost capacity further and meet the 2020 target, China is having to explore locations that are further offshore.

To facilitate this, Huadong Engineering Corporation is planning a ground-breaking 1.1 GW offshore windfarm some 90 km off the coast of Jiangsu Province in eastern China.

To support this project, Huadong has hired energy experts from certification body DNV GL to supply technical training, advice and support on their feasibility study on aspects of conceptual design and risk assessment.

Traditional submarine high-voltage alternating current (HVAC) cables become extremely inefficient when transporting large amounts of electricity over such long distances. In contrast, high-voltage direct current systems allow power to be transmitted over large distances under the sea with minimal losses.

Therefore, a key stage in the new project will be the creation of an offshore HVDC transmission system to export offshore power from the windfarm to the mainland, including offshore HVDC converter station, submarine cables and onshore HVDC converter station. This will be the first offshore voltage-source converter HVDC system in China.

“Offshore HVDC transmission system is a new business for DNV GL China and the Asia Pacific region,” said Haifeng Qi of Huadong Engineering.

“So it is invaluable to be able to call on DNV GL. Their experience will be a critical factor in successfully delivering a major new windfarm so far from land to help China continue to lead the way in offshore wind generation.”

William Pan, head of offshore wind APAC for DNV GL–Energy, said that compared with onshore HVDC technology, “offshore wind HVDC has unique specification and requires to combine both offshore wind and HVDC technology on the limited space, to satisfy safety and function requirement”.