One-piece angled rotor
TouchWind develops a completely new design for a floating wind turbine. This turbine uses a one-piece rotor that is positioned angled to the wind. The innovative design lowers the turbine’s costs without compromising yield. In addition, maintenance is easier and turbines can be placed more densely in a wind farm, says TouchWind's manager and founder Mark Goossens.
For which problem have you found a solution?
“Current generation wind turbines have a rotor with pitch control on each blade. This regulates the rotational speed of the rotor to maximize energy yield. To prevent the generator from overloads, the turbine is switched off at wind speeds above 25 m/s. Pitch control is a costly and complex system with many components5.
In addition, traditional rotors tends to destabilize the floating construction. To guarantee stability, you need huge floaters, which results in a high LCoE’s.”
What is the core of your solution?
“Our rotor consists of one structural part, and it is angled to the wind: the higher the wind speed, the more horizontal the rotor. That way we regulate the rotor’s rotational speed. Speaking constructively, that is a lot less complex, but it introduces new problems, like: how do you prevent the rotor from breaking off due to the asymmetrical load on the rotor shaft? We solved that mechanically by using a smart way of connecting the rotor to the shaft.
The rotor is designed to generate large vortices. Normally, a rotor’s energy-poor wake influences the next downwind turbine in a wind farm. In our design, the vortices mix the energy-poor and energy-rich air. As a result, more energy is generated. In fact, we make use of more air: also air that is not passing through rotor’s projected surface area.
We increased the stability of the wind turbine by turning the rotor a quarter turn, so that it is almost perpendicular (±80 degrees) to the mast. No matter the wind direction, the rotor always pulls longitudinally from the mast, keeping it upright. The faster the wind blows, the more vertical the wind turbine will be and the more the rotor pulls upwards and stabilizes the system. ”
What is so pioneering about your innovation?
“The complete principle is unique. If you put a rotor at an angle to the wind, you expect it to “catch less wind” and thereby reduce the energy yield. According to Betz’s laws, this is true because the flow area, becomes smaller. However, we have succeeded in tilting the rotor without compromising yield because we make use of large vortices
Furthermore, the method of stabilization is ground breaking. The rotor is always perpendicular to the mast and pulls upwards. So as long as you make sure it doesn't “fly" out of the water the rotor stabilizes the system.”
What does your system deliver?
“Our wind turbine is cost-efficient because the construction is relatively simple. The rotor consists of one part; no pitch control per wing is required. Aerodynamically, very complex, but structurally quite straight forward. Maintenance costs are low because there is less components and the turbine can be tilted to the water surface
Moreover, our turbines can be placed closer together. It is estimated they can be positioned 1.5 to 2 times as close as conventional turbines. That is in two directions, meaning it results in a quadratic growth of turbines per km2. In addition, they can handle higher wind speeds of up to 70 m/s. So, it does not only generate more, but also more often.
And finally, the turbine can be assembled in the port. This makes installation at sea - much simpler and therefore reduces CAPEX.”
What challenges do you face?
“It is a completely new technology that has to be integrally designed. All aspects influence each other, so the hydrodynamic and aerodynamic behaviour will need to be calculated in one mathematical model. In addition, it concerns gigantic investments. We collaborate with large partners, but we are a new and relatively small player. The (floating) offshore wind market is characterized by a limited number of dominant players with enormous interests. So despite technology, our challenge is: How does one successfully introduce a completely new technology to the market? ”
Where are you now?
“We have formed a consortium with two knowledge institutions (Delft University of Technology and Marin) and three industrial parties (VDL, Nidec and We4ce). The consortium received a subsidy from RVO so that we can continue working on the design over the next three years. We simulate the systems dynamic behaviour and also tested a wind tunnel research model. The measurements largely confirm our theories of vortices and energy production. The wind turbine rotates stably in a slanting position and in this position it produces more energy than in vertical (conventional) position.
What are your next steps?
“The research models have a rotor diameter of 1.20 meters. That is the maximum to fit the wind tunnel properly.. That is why we want to test the next 6-meter model outdoors. We will be testing a few models with a diameter of ±30 meters in 2022, where our focus is on the wind farm effects. We know we can place them in a denser grid than tradition turbines, and we want to investigate how dense that grid can be for maximum energy yield.”
What are the benefits of Offshore Wind Innovators and TKI Offshore Wind?
“Without Offshore Wind Innovators it would have been much more difficult to form this consortium. Their network has helped us to gain knowledge from the market. Innovation manager Martin Weissmann brings parties together and he does a fantastic job. In addition, we can spar well about the right strategy. The network meetings of TKI Wind op Zee are also a very pleasant way to get in touch with other parties.”