Tilting Windmills Can Save Fortunes · 17. September 2012
Future wind turbines can be produced much more cheaply and with significantly lower weight if they are designed to lean against the wind. So concludes an acclaimed final project from two new engineering graduates of Aalborg University who have experimented with a smart and potentially revolutionary idea for the market from wind turbine manufacturer Vestas.
- The whole point of the project is to investigate whether it’s possible to reduce the load on the wind turbine tower by letting it balance against the wind. This can save on materials and labor, so the entire wind turbine is cheaper to set up, explains Martin Bonderup Brorsen who along with classmate Jesper Larsen received the top grade of 12 for the project.
The idea of dropping the firm anchoring of the heavy wind towers and instead placing lighter versions on pivoting hinges comes from Vestas own development division. A trip on a two-wheeled self-balancing Segway vehicle provided specialist Keld Hammerum some inspiration while he was looking for solutions that could reduce the load on the turbines in extreme situations with strong winds.
- I got the idea for the principle while working on a project that aimed to reduce extreme loads on wind turbine towers. At the same time, I tried a Segway, so the idea may well be described as a mating between a windmill and a Segway. And in principle there are no technical barriers in allowing a wind turbine to lean against the wind, says Keld Hammerum.
According to the Vestas specialist, the final project documents that two very fundamental requirements are met – that the turbine must be stable regardless of weather conditions and that it of course must be effective at converting wind into energy.
Simulations
The challenge on the other hand is that there must be an advanced control system, which utilizes the wind turbines hinged movement to keep it balanced in all kinds of weather. This can be achieved by continuously adjusting the turbine blades’ angle to the wind direction and their rotational speed.
The control strategy that the two newly graduated AAU engineers used for this purpose proved to be very effective in simulations. The load on the tower was reduced by about 83 percent, and the metal fatigue was reduced by an entire 99.86 percent.
- The possible negative side effects are that it can affect energy production, because something is lost when the blades’ position is changed. In our simulation, we lose about 3.4 percent of the power output as a result of this. But the important conclusion is that the concept actually works without completely changing the blade design or something similar, says Jesper Larsen.
Quantum leap
Specialist Keld Hammerum stresses that at Vestas the project is still in the very early concept stage. It is therefore not possible for him to say whether specific products derived from it will come out on the market, or when that might happen. Alternatively, he does not hide the fact that the potential for large savings in materials for the wind turbine is worth pursuing:
- For our products to be competitive cost price is crucial. The tower and foundation of a wind turbine are an essential part of the price, so significant load reductions are extremely interesting. It’s not wrong to say that the realization of this concept will be a quantum leap in the structural design of wind turbines, states Keld Hammerum.
The promising numbers from the simulations must be treated with caution, but in any case Vestas has gotten an important thing out of the project:
- The greatest benefit we’ve received is the realization that the extra degree of freedom does not necessarily affect the rest of the windmill's performance significantly in negative way, says Keld Hammerum.
For the two AAU engineering graduates, having worked with Vestas was also a good experience:
- It's always more exciting to work with the industry because it adds a touch of practical application where university projects otherwise can often seem too theoretical. In addition, Vestas and Keld Hammerum have provided some very interesting feedback, particularly in terms of how we should test our solution and assess the results, says Martin Bonderup Brorsen.
Further information:
• Martin Bonderup Brorsen, Engineer, martin.brorsen@gmail.com, mobile +45 2834 7692.
• Jesper Larsen, Engineer, knorr.jesper@gmail.com, mobile +45 2729 4103.
• Keld Hammerum, Specialist, Vestas Technology R&D, keham@vestas.com, tel. +45 9730 7265, mobile +45 2534 8035.
• Carsten Nielsen, Science Journalist, Aalborg University, cn@adm.aau.dk, mobile +45 2340 6554.
