Heated patches for wind turbine blades11/10/2016
Futures Energies, a leading player in renewable energy in France, launched a call for projects in June 2016 to identify innovative solutions for reducing the impact of ice on wind turbines, especially on production losses.
22 applications were sent in response to the call, both from France and abroad. We asked Bernard Laurent (Deputy General Manager of Futures Energies) to tell us about the origin of this call for projects and the criteria used to choose the winner.
How is ice a problem for wind turbines?
In general, ice affects wind turbines both because of the very high speed at which the blade tip rotates (around 250 km/h) and because we often install wind turbines in rural areas where frost can occur.
In most cases, ice-related production losses are quite low and are accounted for in the business plan. In general, they represent a loss of only about 1%.
However, some sites face more serious problems in this area than others. This is especially true of Futures Energies’ production facility in Rézentières, which is located at an altitude of 1100 m in the Cantal, near Saint Flour. Icing over is common on this site and causes machine stoppages and relatively large production losses as a result.
The facility was commissioned in 2010, and so far we have not found an effective way to reduce these losses. The security aspect – particularly the risk of ice being cast off the blades – is also an important issue for the wind farm operators.
We launched a call for projects on OpenInnov by ENGIE to get a sense of the market and to see if there were innovative solutions out there that met our security requirements.
Can you be more specific about what problems ice can cause for wind turbines?
When there’s ice on the blades, the machine's safety systems detect it and stop operations automatically.
The responses to the call for projects were quite varied, ranging from new paint or water repellent varnishes to heating systems (like the one that was ultimately selected).
It’s true that we got a number of interesting responses to the call, with two broad categories of technological solutions:
- So-called passive technologies based on paint or special varnishes that can be applied to the blades and which are intended to prevent ice from forming
- Active, heat-producing technologies, which circulate electricity through a special paint that heats up to melt ice or prevent it from forming.
We ultimately preferred the latter kind of solution because of less-than-positive previous experiences in the company with passive paint. That kind of paint quickly gets dirty and less efficient, requiring a new coat, which makes it cost prohibitive.
Is the method you chose – heated patches – still in the testing phase?
Yes, clearly. We had already worked on this kind of product two or three years ago. At the time, the technology was really in its infancy. It’s now much more mature thanks to a very capable French SME that specializes in the adhesive system that allows the heated patches to be pasted onto the blades. They were able to perform field tests last winter, and the results were satisfactory overall, although there are still some technical problems.
The selection committee chose them because of the prospect of working with them to resolve these issues. They clearly identified the technical problem that has to be addressed, which is how assemble the heated patches so they last over the long term by connecting them to each other electrically.
It is important to work together with this SME and with the wind turbine supplier to solve this problem and to integrate the proposed solution onto our site.
What shape this partnership will take remains to be discussed with them.
Futures Energies is a subsidiary of the ENGIE Group, a leading provider of renewable energy –wind, solar and marine – in France. Futures Energies operates 26 wind farms and two solar parks in France and provides electricity for more than 500,000.
Source: Christine Leroy