In a recent global clean energy investment trends forecast, New Energy Finance estimated that worldwide investment in clean energy would total $63.3 billion in 2006, up 30% from 2005. The forecast further estimated that global investment could reach $100 billion per year by 2010. New Energy's forecast notes that offshore wind ‘represents the single best opportunity for large-scale development of renewable energy resources,’ but the sector has been slow to realize initial plans for offshore development.
In its recommendations for maintaining long-term attractiveness of the clean energy industry to investors, New Energy identified impediments to offshore wind farm technologies that are hindering significant investment in this sector. Specific hurdles noted in the forecast include:
-cost of offshore development – double that of onshore projects,
-hostile operating environment,
-long distance to grid feed-in points and
-higher maintenance costs.
In an effort to promote future renewables investment, the Massachusetts Technology Transfer Center, the Massachusetts Hydrogen Coalition and the Massachusetts Institute of Technology (MIT) Enterprise Forum presented their second annual Conference on Clean Energy in Boston on Nov. 2, 2006. The conference provided an opportunity for inventors and entrepreneurs to deliver presentations for investors on renewable technologies being developed in the Northeast. Among technologies introduced at the conference was Medford, Mass.-based Oceanwind Technology LLC's floating offshore wind farm (FOWF).
Floating turbine platform designs are not a new concept to the offshore wind farm sector, but they are in the development stage and likely would not be commercialized fully for at least a decade, according to wind power industry representatives.
MIT and National Renewable Energy Laboratory (NREL) researchers have received positive responses from wind and energy companies to their floating platform design, which is similar to Oceanwind's concept but is based on a tension leg platform (TLP) system that uses tethers to connect the corners of a platform to a mooring system. (See ‘MIT, NREL Study Floating Turbines,’ NAW, November 2006, p. 3.) Although both designs take advantage of wind resources where ocean depths reach more than 100 feet, Oceanwind's concept is fundamentally different and specifically addresses cost and operation hurdles identified by New Energy.
The platform is a derivative of a spar-buoy structure and maintains a center of gravity that is very low and deep in the water. The near-water surface section is hydrodynamically designed to minimize wave load, while bridled cables add stability against roll and pitch movement. The platforms would be connected to one another at their bases by horizontal tension cables that form a stable multi-unit foundation, which allows anchor-sharing to drastically decrease the anchoring costs per unit.
The biggest advantage of Oceanwind's design over the TLP-based floating platform is the low anchoring cost, according to Yuki Yamamoto, chief executive officer of Oceanwind. Anchors for the TLPs need to sustain substantial vertical force upward, and the cost depends heavily on the depth and the seabed soil conditions. With Oceanwind's FOWF, anchors are shared and forces applied to the anchors are more horizontal.
The FOWF horizontal connecting cables could be placed deeper than 250 feet so most surface vessels can pass over them. Additional benefits of the technology include its ability to take advantage of strong, steady winds on the outer ocean and off-site manufacturing capabilities that reduce on-site construction.
Oceanwind currently is seeking to raise $5 million, $320,000 of which is slated to support a prototype phase.
‘We received some investor leads from the conference, but we are open to more,’ says Yamamoto. The prototype phase will include hydrodynamic modeling and scaled model testing to complete the design of full-scale demonstration units. A commercialization phase, currently slated for 2008 or later, will use the remaining $4.68 million investment to develop demonstration units.
The location of Oceanwind's test platforms will be based on the needs of investors. ‘The Northeastern states, California and Hawaii provide the best potential for our technology,’ says Yamamoto.
A handful of shallow-water offshore wind farms have been proposed in the U.S., but none has reached commercial operation. Wind Energy Systems Technologies LLC plans to place 50 3 MW wind turbines off the Texas coast near Galveston, while Cape Wind could bring 130 GE 3.6 MW turbines to Nantucket Sound. The turbines in the Cape Wind project will be erected using a monopole foundation driven approximately 80 feet into the ocean bed.
Construction of Cape Wind was slated to begin in 2006, but the project currently is on hold pending issue of a draft environmental impact statement from the U.S. Department of the Interior's Minerals Management Service, says Mark Rodgers, communications director for Cape Wind.