A guest blog by John Dooley titled Technology problems with wind turbines appeared in the Irish Energy Blog in November. An unnamed commentator prefaces the article on LinkedIn with, “the blog has the Irish wind industry hopping and the wind-turbine manufacturer Siemens, tearing it’s (sic) hair out. The secret is out – the design flaws in these big bad turbines are so fundamental that their lifespan is nothing near to what it says on the tin.” In the blog, Mr. Dooley cites an article from Windpower Engineering & Development, authored by AeroTorque’s Doug Herr and David Heidenreich, that discusses bearing problems in wind-turbine gearboxes.
It’s no secret that wind critics such as Mr. Dooley will use any club to beat the wind industry. They seem to find no half-truth too misleading and no benefits too good to ignore.
For instance, it is no secret that wind-turbine gearboxes have had a shorter lifespan than was claimed 10 years ago, and the article in Windpower Engineering & Development was not the first to point out the problem. My disappointment in the blog is that the Mr. Dooley did not finish reading the article. If he had, he would have learned that AeroTorque had studied the problem of axial cracking in gearbox bearings, pinpointed its likely source (transient torque reversals), devised a torque-limiting mechanism that relieves drivetrains of reversing torque overloads, and that after testing the device in wind turbines, found that it works.
Doug Herr, one author of the article cited by Mr. Dooley, had this to say about the blog: “The characterization of the Wind-over-power ratio is incorrect in the blog post. There are no standards regarding that calculation. Rather, it is a new way of analyzing the potential for excess loading. The intent of the article was to point out the many improvements to the design of turbines and the availability of solutions that have been designed to ensure even greater reliability. Wind works because, everyday, new research and new developments make for better turbines, a better return on investment and a greener tomorrow!”
If Mr. Dooley had been a regular reader of the magazine, he would know that gearbox manufacturers, such as Moventas and repair firms such as Gearbox Express, have engineered solutions that toughen gearboxes to lengthen their lives. And if he would scan www.windpowerengineering.com every once in a while, he would also find that Frontier Wind has devised a mechanism for turbine blades that can eliminate damaging transient torques caused by gusts and turbulence, further lengthening the life of drivetrain components.
This blogger further quotes from the magazine article, “…it’s rare to find axial-crack failures in gearbox bearings in other industries.” That is true enough but again no secret or mystery. Gearboxes in most industry are bolted to massive bases and operate at a steady state with few if any torque overloads. In contrast, wind-turbine gearboxes operate on tall towers and frequently work at an unsteady state. This is common knowledge to most engineers.
What’s also disappointing is that Mr. Dooley seems to conclude that what we know now is all we can know, and wind turbines will not improve. However, anyone with a modest sense of history knows that is not true. Can you remember a time before cell phones? Where did they come from? They came from curious and inventive people, the same type that are building the wind industry.
It is further disappointing that this blogger seems to expect flawless performance from the wind industry. What industry, please tell, produces flawless products and is not trying to improve itself?
To compound my disappointment, the author makes no mention of the incredible usefulness of the wind industry and how it has brought jobs to rural communities and financial benefits to land owners on whose property wind farms are built. Perhaps in this regard, the UK can take a lesson from the U.S. wind industry. For instance, from The Wall Street Journal, “wind farms generate almost $200 million in land leases for American farmers, providing a much-needed source of income for many families, writes National Farmers Union President Roger Johnson. Between 98% and 99% of farm land with turbines can be used for other applications. In Missouri, landowners receive $1.4 million each year through land leases. “The benefits in this case largely outweigh the costs,” he writes. U.S. farmers also consider the wind a drought-resistant crop.
Larger turbines are a challenge but their economy of scale makes good sense. In the same way that aircraft have been built larger and more reliable with time and R&D, so too will wind turbines.
The wind industry faces no insurmountable challenges. Mr. Dooley has simply recognized the growing pains of a vibrant industry. To see what could be showing up on wind turbines of the future, just page through the recent issue of Windpower Engineering & Development. The latest digital issue is here: https://www.windpowerengineering.com/digital-issues/windpower-engineering-and-development-digital-edition-october-2015/.
- Paul Dvorak, Editor, Windpower Engineering & Development
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