China Special - Offshore: Donghai litmus test for offshore plan

China's potential for offshore is great, with particularly rich wind resources off its eastern coastline and neighbouring islands and islets.

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If successfully harnessed, these resources could ensure electricity demand in nearby major load centres is met.

Preliminary estimates for the country suggest at least 750 GW of offshore wind power capacity could be installed - that's three times more than the potential onshore. China's Energy Research Institute says that 100 GW could be installed at a water depth of 10 metres. A further 300 GW could be installed in waters 20 metres deep, and up to 490 GW could go at 30 metres deep.

Interest in exploiting this potential is growing, and the performance of the Donghai Bridge project, the only real commercial wind project at sea, is being watched eagerly. In 2007, a 1.5 MW direct-drive wind turbine was installed for scientific research, but was not connected to the power grid.

"If our project goes smoothly, China's offshore wind farms will surge ahead. Otherwise, development will be prolonged," says Zhang Kaihua, deputy general manager of the Donghai Bridge project. "The offshore wind farms scheduled to be built in east China and north China coastal areas have similar situations to ours."

Donghai Bridge, off the eastern coast of Shanghai, currently comprises three prototype 3 MW turbines from Sinovel, which were connected to the local grid in August. The plan is to install a total of 34 turbines, taking the project to 102 MW.

Besides the soft seabed conditions, the impact of the typhoons that hit south-east coastal provinces every year is one of the most challenging problems. Super Typhoon Saomai almost destroyed the coastal Cangnan Wind Farm in August 2006, damaging 20 of its 28 turbines. "We may boldly develop offshore wind farms in coastal areas to the north of the Yangtze River estuary, considering the present technological levels. But we must take great care to develop offshore wind farms to the south of the Yangtze River estuary, because of the typhoons," says Wu Yundong, general manager of Zhejiang Huayi Wind Energy Development.

Much work on technology is needed before any further development can happen in earnest. Projects at sea demand more complex technologies and construction methods, because the operational environment is more complex than for land-based wind farms. "Because of salt mist erosions, ocean waves and tidal currents, offshore wind farms raise high demands on the performances of turbines," says Wu. "Offshore wind equipment has to be operated for a considerable period on land, with operation experiences accumulated, before they are shipped to offshore farms. Otherwise, investment risks will be enormous."

Other key issues include a lack of vessels designed specifically for offshore wind farm construction, while maintenance of offshore turbines is also a difficult problem.

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