Foundations are a big part of land-based turbines and more so for those headed offshore. A solution to the tricky foundation problems is to omit them – let the turbines float. So far, only one turbine floats. It’s on a 100-m spar in Norwegian waters. Principle Power (principlepowerinc.com) has another idea in its WindFloat, a design based on concept studies in the oil and gas industry. Its several advantages, says the company, include dynamic stability that provides pitching and yawing low enough to allows selecting from the current stock of turbines. The platform can be assembled onshore and wet-towed to sites not visible from shore. The developer says its primary markets are the transitional (30 to 60m) and deep (>60m) offshore water in the U.S. and Europe, sites previously inaccessible. These have a wind potential of at least 2 terawatt.
The details provide a closer look at WindFloat. A recent agreement with Vestas will supply a 2-MW turbine to a pioneer project off the Portuguese coast. Vestas and Principle Power have agreed to a joint venture led by Energias de Portugal to supply a wind turbine to the project. It marks the start of a test for floating turbines as part of a 12-month demonstration to begin in the second half of 2011.
WindFloat is fitted with horizontal water-entrapment plates at each column’s base. These stablilize the platform with additional damping and entrained water effects, allowing use of existing wind turbines. The platform’s stability is assisted by a closed-loop active ballast that mitigates wind-induced thrust forces, restoring the system to best efficiency following changes in wind velocity and direction.
Fabricating the structure onshore allows completing qualification tests at quayside in a controlled environment. The company adds that says commissioning costs are significantly less when compared with monopole-jacket offshore support structures.
The mooring system uses conventional components such as chain and polyester lines to minimize cost and complexity. This also minimizes use of pre-laid drag embedded anchors and site preparation.
WPE
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