The WindQuest floating wind turbine in testing in Brest: a vertical axis, a smaller and cheaper float

Vertical axis: a solution to reduce manufacturing costs

"The original shape presents several advantages", explains Benoît Augier, head of the test tank at the Ifremer Centre in Brest. "Most of its weight is concentrated at the foot of the mast. Its centre of gravity and centre of buoyancy are thus 20% lower than those of horizontal axis wind turbines. More stable, the wind turbine can be installed on a float which is 40% smaller. This implies lower manufacturing costs and therefore a lower cost per kWh. This is the challenge facing offshore wind, and renewable energy in general: develop a technology capable of competing with other sources of energy.

Another advantage is that WindQuest wind turbines are much more tolerant of wind direction variations than conventional wind turbines, which have to turn their rotors accordingly. "The wind can vary by 40 °, hardly affecting WindQuest's performance," adds Benoît Augier.
 

Float behaviour, filmed from every angle

On 8 July 2019, a series of experiments got underway at the Ifremer test tank to characterize the behaviour of the wind turbine structures under the effect of the thrust generated by blade rotations. The first step is to test the "attitude" of the float that will support the wind turbine.
"For these first tests, the float model called Nautilus, designed by the Spanish company Tecnalia, is topped with a double fan that aims to simulate the thrust generated by blade rotation", explains Benoît Augier. "We test and compare the attitude of the float against the two types of aerodynamic thrust generated by the WindQuest wind turbine and a conventional wind turbine. Thanks to the four cameras around the tank, the Ifremer team films and measures the movements (roll, pitch, surge, heave, yaw) of the two objects. The team then uses these images to reconstruct the three-dimensional behaviour of both wind turbines at sea and analyze their differences.
 

Wind tunnel and offshore testing to follow in 2020 and 2021

Once this stage is completed, the plan is to test this same float in 2020 under aerodynamic thrust conditions. "The aerodynamic thrust effect of wind turbines varies constantly with the movements of the float. It is therefore important to test these conditions closer to reality, " adds Benoît Augier.
 

Other tests on the horizon:

- end of 2020: experiments at the wind tunnel of the National School of Mechanics and Aerotechnics (ENSMA) with the P' laboratory in Poitiers. Objective: to characterize the aerodynamic performance of the wind turbine under configured float movement conditions.
- début 2021: beginning of 2021: construction of a 1/8 scale demonstration model to be tested offshore at the THeoREM Research Infrastructure test site in Sainte Anne du Portzic. Objective: To characterize the performance of the global structure (wind, float and anchor) under real sea conditions.

Photo: IFREMER