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Offshore vs. onshore
Wind energy has been harnessed on land for centuries. Moving the technology offshore brings advantages and challenges. The advantages are proximity to population centers, stronger winds that are in phase with peak demands, and the potential to develop larger farms. In addition, the capture and conveyance of offshore wind and onshore wind -- in terms of IT -- are similar.
However, transmission of the energy from a remote offshore facility presents challenges. It is expensive to convey energy to shore. About 20 percent of the project cost for the up to 1,000-MW London Array, the world's largest offshore wind farm, will go toward developing a grid connection.
Site assessment
Wind turbine structure design, similar to the design of wave and current energy capture devices, requires information on the environment where the energy harnessing equipment will operate, as well as information specific to the particular energy source they seek to harness. Right from the feasibility stage of an offshore wind energy project, information on the region's seismicity, water depth, climatology, and a review of the existing wind, wave, current and tide level data for the site can provide early screening for suitable areas and structure types. Data regarding the region's geology and subsurface conditions will provide an indication of foundation and transmission line design requirements.
As the project takes shape, more detailed data will be required for designing the structures. Questions to be answered include:
- What are the 100-year extreme values for wave heights or wind speeds?
- What is the best time of year for installation?
- What is the forecasted power output from the installation?
- What foundation system will be used?
While it is often sufficient to use existing data sources and models for feasibility studies, it is usually essential to make at least a few months of site-specific measurements to fully validate wind, wave or current criteria used for engineering purposes.
In particular, measurements during the winter months are essential for validating statistics toward the extremes of likely conditions. Site assessment and other engineering aspects of designing and installing the necessary infrastructure were discussed at the Marine Technology Society for Offshore Wind Power Workshop held earlier this year.
What does offshore wind mean for utilities?
U.S. offshore wind development requirements will be defined by offshore wind experience in Europe and offshore oil and gas experience in the United States. Project success will require firms that have such experience.
With the American Recovery and Reinvestment Act of 2009, provisions of interest to wind energy -- such as the authorization of additional clean renewable energy bonds to finance facilities that generate electricity from renewable sources such as wind -- could mean that utilities attain their renewable energy portfolio goals more quickly.
Owning and building
Construction and finance would be the responsibility of developers looking to build the farms -- likely in federal or state waters. Firms with open-ocean experience should be retained during each phase of the project, from survey to investigation, through to design and fabrication.
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Intelligent Utility magazine is the new, thought-leading publication on how to successfully deliver information-enabled energy. This article originally appeared in the May/June 2009 issue.