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The US offshore wind energy technology conundrum

US could see more then 4,000 GW of power from offshore wind

By Layer 8 on Fri, 10/08/10 - 2:26pm.

If wind is ever to be a significant part of the energy equation in this country we'll need to take it offshore - into the deep oceans. Large offshore wind objects could harness about more than 4,000 GW of electricity according to a massive report on wind energy out this week from the US Department of Energy.

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The DOE notes that while the United States has not built any offshore wind projects about 20 projects representing more than 2,000 MW of capacity are in the planning and permitting process. Most of these activities are in the Northeast and Mid-Atlantic regions, although projects are being considered along the Great Lakes, the Gulf of Mexico, and the Pacific Coast. The deep waters off the West Coast, however, pose a technology challenge for the near term.

"Although Europe now has a decade of experience with offshore wind projects in shallow water, the technology essentially evolved from land-based wind energy systems. Significant opportunities remain for tailoring the technology to better address key differences in the offshore environment. These opportunities are multiplied when deepwater floating system technology is considered, which is now in the very early stages of development," the report states.

The challenges of offshore wind technologies are immense however. There are a number of issues including:

Turbine blades can be much larger without land-based transportation and construction constraints; however, enabling technology is needed to allow the construction of a blade greater than 70-meters in length.
The blades may also be allowed to rotate faster offshore, as blade noise is less likely to disturb human habitations. Faster rotors operate at lower torque, which means lighter, less costly drivetrain components.
Challenges unique to the offshore environment include resistance to corrosive salt waters, resilience to tropical and extra-tropical storms and waves, and coexistence with marine life and activities.
Greater distances from shore create challenges from increased water depth, exposure to more extreme open ocean conditions, long distance electrical transmission on high-voltage submarine cables, turbine maintenance at sea, and accommodation of maintenance personnel.
A primary challenge for offshore wind energy is cost reduction. Developing the necessary support infrastructure implies one-time costs for customized vessels, port and harbor upgrades, new manufacturing facilities, and workforce training. In general, capital costs are twice as high as land-based, but this may be partially offset by potentially higher energy yields-as much as 30% or more.
As was experienced with land-based wind systems over the past two decades, offshore wind costs are expected to drop with greater experience, increased deployment, and improved technology. To make offshore wind energy more cost effective, some manufacturers are designing larger wind turbines capable of generating more electricity per turbine. Several manufacturers are considering 10-MW turbine designs, and programs, such as UpWind in the European Union, are developing the tools to allow these larger machines to emerge.

The report went on to look at the technologies needed for deep water wind platforms. The three concepts for floating platform designs, including the semisubmersible, the spar buoy, and the tension-leg platform, each of which use a different method for achieving static stability.

"Although it is not yet known which of these designs will deliver the best system performance, designers seek platforms that are easy to install and minimize overall turbine loads. To determine this optimized design point, advanced computer simulation models need to be developed and validated. Most of the projects now reside in shallow water, and only two projects to date use transitional structures. One Norwegian demonstration project, Hywind, uses a deepwater floating design."

Looking for a major new ways to harness wind, solar and other evolving renewable energy, the DOE last month issued a call for advanced large-scale energy storage system technology. The DOE said the goal of its solicitation is to identify and prove new concepts for applied research in materials chemistry, battery components, battery designs and any technologies that will lead to breakthroughs in grid energy storage.

Such technology will be focused on novel materials, electrodes, electrolytes, membranes and other components, along with new concepts for ultra low cost, high efficiency and long lasting energy storage systems. Emphasis is placed on highly innovative research proposals in areas that have the potential to have strong impact on large-scale energy storage in the future, the DOE stated.

In July the DOE said it was looking for the public to help identify the most significant barriers to future wind energy development. In addition the agency said it is looking for ideas that will help the US grow and educate its wind energy workforce. While other US energy industries have extensive training infrastructures in place, minimal infrastructure currently exists for the wind industry. Many companies are struggling to find individuals with experience in wind technologies, the DOE stated.

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