For every good turbine, there’s a good platform. At least that’s what Norwegian-based NLI Innovations is aiming for in its efforts to develop a new offshore floating platform. “There is still a lot of room for development within wind energy, especially turbines,” says Anders Torud, business development manager at NLI. “That includes materials and how they are manufactured.”
The WindSea is a floating structure currently in the R&D process that can carry three standard horizontally axled wind turbines. “In our opinion, any of the commercially available offshore turbines on the market are compatible with the platform and can carry any of the 5 megawatts (MW) turbines available on the market,” says Torud. “In fact, we believe the platform will be able to carry 6 to 10 MW turbines when they become commercially available.”
The turbine platform is based on the well-proven concept of semi-submersible platforms currently used extensively for offshore oil and gas installations. However, compared to other proposed design concepts that use a spar buoy design, the WindSea uses a semi-submersible platform. This allows it to operate in relatively shallow water, needing only approximately 147 feet to operate whereas others need between 300 and 400 feet depths. And currently there is no technical limit to water depth installation.
To date, the WindSea has completed a proof of concept phase including tests in a wave tank and wind tunnel, and been verified by third parties. Now the company is working on financing a large 1:3 scale prototype project they hope to have operational by 2012. During this phase, the company hopes to narrow down its materials options, which include composites for both the primary structure as well as secondary structures like staircases and j-tubes. “Composites would allow a lighter structure and less corrosion,” says Torud. “Deciding what and where products we’ll use will be a continuous process, even into the commercial phase as we determine what gives the overall system the best lifetime cost.”
One of the biggest options the company wants to offer with the WindSea is portability. From the beginning, NLI designed it so when the WindSea is not operational, for example, it only needs between 26 to 32 feet of water. Those specifications allow the platform to be completed at a yard—including the turbine installation—and transported from the shipyard, effectively eliminating the need for costly heavy-lifting vessels on site.
Faced with a potential problem, WindSea still feels its new product will bring a lot to the wind-market table. During development, NLI placed three turbines close together on a relatively small platform to test production rates. While one of the turbines will experience a shadow effect, where less wind is captured by a nearby turbine, the calculations and wind tunnel tests have both proven that over a one year production cycle, the shadow effect only amounts to a 7 percent production loss. Combine that, as they label it, nominal loss with the installation and upkeep reduction costs and NLI feels it has an attractive concept on the seaboard horizon.