An enormous wind turbine collapsed in January in Dodge County. Here's what we know nearly two months later.
HERMAN - The overnight collapse of a towering, 400-foot-tall wind turbine at the Butler Ridge Wind Farm in eastern Dodge County on Jan. 18 continues to be a topic of conversation and concern in the town of Herman and surrounding communities.
Stunning photos of the collapsed tower went viral on social media, attracting unusual attention to the town, a farming community midway between Horicon and Allenton on State 33.
Nearly two months later, the remains of the crumpled tower are still where they fell, it's 86-ton turbine and blades resting partially buried in a hole created by the impact.
Preparations are underway for its removal, but there are still no answers from Nextera Energy Resources, the owner and operator of the wind farm, to questions about what caused the collapse.
Here's what we do know.
Could it have been brought down by wind?
The day of the collapse started with light winds that built out of the northeast after sunset to nearly 20 mph, with gusts up to 30 mph, according to records from the Dodge County Airport in Juneau, the closest National Weather Service observation site.
Those wind speeds are what the turbines need to produce their maximum electric output, and were well below the 40 mph speed at which Butler Ridge's GE turbines are designed to shut down to avoid damage, according to a fact sheet. That only one turbine was damaged suggests the answer is more complicated than a single large wind gust.
Were the other 35 turbines inspected after the collapse?
NextEra, in a statement immediately after the collapse, said it would inspect the other turbines.
Property owners who rent land to the company weren't sure if that had happened by early March. However, several people who rent land to NextEra said that local maintenance and inspection crews have had a regular and diligent presence over the years and continue to patrol the area.
Do wind turbines get old? How long do they last?
The Butler Ridge Solar Farm began producing electricity in 2009. That makes the turbines middle-aged based on a general life expectancy of about 25 years. Wind turbines need to be regularly inspected throughout their life cycle in accordance with the manufacturer's guidelines, said Tony Palese a spokesman for Alliant Energy, which operates a wind farm of similar age near Eden in Fond du Lac County.
In addition to visual inspections, wind turbines are continuously monitored by electronic systems which detect when there is a problem with the turbine, rotor or blades, and can be shut down remotely by operators, said Jason Ryan, spokesman for the American Clean Power Association, a Washington, D.C-based industry group.
How much power was lost when the turbine collapsed?
Each turbine at Butler Ridge can produce 1.5 megawatts of electricity under ideal conditions. That's enough to power about 500 homes.
The loss of one turbine doesn't affect the others — each operates independently and sends power to the electric grid. The entire 36-turbine wind farm produces enough electricity to power 18,000 homes.
Most of that energy is sold to WPPI Energy under a contract that dates 2009, an association of 51 municipally-owned Wisconsin utilties. WPPI declined to comment for this story.
Any excess power is sold to the wholesale power market.
Has something like this ever happened in Wisconsin?
This was the first collapse of a wind turbine on a Wisconsin wind farm since the first one became operational in 1999.
The state is home to 10-utility scale wind farms. Combined they have 437 wind turbines that produce about 3% of the state's electric supply, or enough to power about 250,000 homes.
We've seen other windmill collapses in headlines and videos. How often do these things happen?
That's hard to say — there is no offical record keeping when it comes to wind turbine failures.
"There's a lot of operating experience that is shared from company to company, but there is not a one-point catch-all for that," said Neva Espinoza, vice president of energy supply and low-carbon resources at the nonprofit Electric Power Research Institute.
A review of online news stories found six turbine failures in the United States in the last year. The causes that have been made public include storms, mechanical failures and damaged blades.
That may seem a lot, but industry officials point out that there are more than 72,000 turbines operating in the country. That puts the failure rate at about .01%.
Ryan said setback requirements keep the towers well away from roads, homes and other structures to protect people and property. According to ACP data, no member of the public has ever been injured by a turbine, he said.
Our subscribers make this reporting possible. Please consider supporting local journalism by subscribing to the Journal Sentinel at jsonline.com/deal.
DOWNLOAD THE APP: Get the latest news, sports and more
This article originally appeared on Milwaukee Journal Sentinel: What we know about the collapse of an enormous windill in Dodge County
