Dave Alexander | October 22, 2013 | www.mlive.com
MUSKEGON, MI – Ice on Lake Michigan is apparently not a “show stopper” for those exploring wind turbine farms on the Great Lakes.
That is the initial conclusion of University of Michigan marine engineer Dale G. Karr based upon his work for the U.S. Department of Energy studying Great Lakes ice and its impact on wind turbine towers.
“I have not found ice to be a show stopper but our research will be useful in determining that question,” Karr told a lecture audience Monday, Oct. 21 at the Grand Valley State University Michigan Alternative and Renewable Energy Center in Muskegon.
That is not to say that lake ice isn’t an issue, far from it.
“The Department of Energy is supporting this research to see if there is a show stopper,” Karr said. “Ice is a major issue if not the major issue for wind energy on the Great Lakes. The answer will start to emerge next spring when we will determine the designs and costs.”
Already offshore wind production is three times the cost of onshore wind farms such as the Consumers Energy Lake Winds Energy Park now producing electricity in Mason County south of Ludington, according to MAREC Director Arn Boezaart. Factoring in the cost of engineering wind tower protection against the ice is just one more reason that Great Lakes wind farms are likely more than a decade away, if the political will for such installations ever materializes, he said.
Karr said that the United States has taken an economic and technological back seat to Europe – especially Germany – and now both China and Japan in exploring, developing and deploying offshore wind. With the controversy of offshore wind in the United States for more than a decade, no offshore wind turbine has been installed although seven test projects are underway with federal funding.
“Europe is ahead of us probably a decade or so,” Karr said of offshore wind. “The German government is making offshore wind development the equivalent of our 1960s moon program. We are not the world leaders (in offshore wind) but now playing catch up.”
As the University of Michigan’s world-renowned department of marine engineering and naval architecture decided several years ago to delve into offshore wind technology questions, Karr began to study the effects of ice – an expertise he has obtained through studying oil and natural gas rigs in Arctic waters.
“We always get the question, why put wind turbines in the Great Lakes when there is ice?” Karr said of his research.
The answer: A wind map of the United States shows that the Great Lakes has some of the nation’s best wind resources in relatively shallow waters with close proximity to Midwest population centers and electrical grid networks.
These same factors motivated a Norwegian wind energy development company to propose 100-turbine wind farms off the coast of Mason, Oceana, Muskegon and Ottawa counties in 2009. The Scandia offshore wind proposal caused an outcry by many worried about the visual issues of such large structures in the near-coastal waters of the Big Lake.
Specifically, Karr has worked on putting an ice impact component into the National Energy Research Laboratory’s wind turbine model, which has become an industry standard. Ice pushes against a wind turbine tower with the same forces of the wind and wave action found on the lake, Karr said.
“Taking the ice forces into consideration will make these Great Lakes wind turbines more expensive,” Karr said. “There are a lot of engineering challenges.”
Great Lakes ice is more solid and stronger than ocean ice, Karr said. Ice is brittle when cracking it but strong when trying to crush it, he said.
And ice data – the frequency, duration and thickness of the ice – for specific locations in Lake Michigan is not known. That will need to be determined before any wind turbine tower technology is selected for a specific project, Karr said.
In 65 feet of water depth, the offshore industry standard is a mono-pole wind tower anchored into the lake bottom with 100 feet of depth and more needing towers with “multiple feet.” Even deeper water requires floating turbine technology. Each has its own ice issues and economic considerations, Karr said.
“The further offshore you go, the less concern there is with ice cover and ice flows and then the forces are not as much of a concern,” Karr said. The further offshore a turbine tower would be installed would decrease public concerns over views but would add to the overall cost of the project, he indicated.
The University of Michigan professor’s research has looked at six “models” of the effects of ice on Great Lakes wind turbines from ice flow movements impacting the towers, ice slowly crushing the platforms and the random vibrations of ice driven by waves and wind in the open waters.
The typical engineering solution would be to build a “cone” around the base of the tower that would raise the ice in an upward or downward direction – allowing for the ice to break and crack before doing damage. Engineers must worry about tower damage at the surface of the water and in the ice forces applied to the base of the tower in the lake bed, he said.
“Our models are just developing as the research is in its infancy,” Karr said. “We are just beginning.”
URL to article: https://www.wind-watch.org/news/2013/10/22/great-lakes-ice-shouldnt-stop-wind-turbines-but-will-increase-costs-engineering-professor-says/