WIG (wing-in-ground) effect dual-foil turbine for high renewable energy performance

Traditional HATs (horizontal axis turbines) are predominantly used for wind and tidal energy generation. HATs have higher power production than VATs (vertical axis turbines) for which also requires a rotational motion of their rotors. Existing HAT installations and operations are widely seen as wind turbines on land and hydrokinetic turbines underwater. However, the operation of both HAT and VAT requires large rotor diameter for large energy production. These introduce some disadvantages: requirement of large profile height on land and water depth underwater; high rotor tip speed and hence impact on surrounding ecology; and requirement of large kick-in speed and hence a low wind/tidal resource utilization or inapplicability in slow inflow energy sites. A dual-foil dynamic WIG (Wing-In-Ground) effect turbine, WIGT (Wing-in-ground effect turbine) for short, was developed and its renewable energy performance and characteristics were investigated. A performance comparison between traditional HATT (horizontal axis tidal turbine) and a WIGTT (wing-in-ground effect tidal turbine) was made, based on the tidal flow probability distribution of the Minas Passage, the Bay of Fundy, Canada. With about the same swept area, the WIGTT produces 1.73 times annual energy as an HATT. WIGT uses an active pitch control but the required power to pitch the foils was found to be about 10% generated power at the maximum. The use of trapezoidal pitch control produces 1.44 times as much power as either single-foil or dual-foil turbines. With a minimum gap of 16% chord between the foils, dynamic WIG effect produces 1.42 times as much energy. WIGT could generate 5 times power as much as a single foil with sinusoidal pitch and heave. WIGTs also have some outstanding advantages such as large power capacity under confined profile height on land or in shallow waters, power generation capability for low speed inflow, environmental friendly operation and better flow characteristics.