How do wind turbines work?

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Have you ever wondered how wind turbines create energy? Or why they need to be so high? Have you ever seen one standing idle on a really windy day and wondered why the blades weren’t spinning? What about the impact they have on the communities where they are located?

Tune in to this podcast with Dave Harwood, DTE’s Director of Renewable Energy, to learn more about the sophisticated technology that makes today’s wind turbines efficient, cost-effective and safe.

Listen here:

Podcast Transcript:

Dave Lingholm: Welcome to the inaugural “Empowering Michigan” podcast. My name is Dave Lingholm. And generating electricity from wind is a growing industry in Michigan and it’s an industry that DTE Energy has been making some big investments in. To talk more about those investments and about wind energy in Michigan, I’m joined today by Dave Harwood, the Director of Renewable Energy for DTE Energy. So, thanks for joining us today, Dave.

Dave Harwood: Thanks for having me.

Dave Lingholm: Let’s start off just by revealing some of the basics about wind turbines, how they work, how they operate. Can you just give us a brief description of how it works and what it does to actually produce electricity?

Dave Harwood: Yeah, absolutely. So, I in a very simple way, you know, a wind turbine, consists of a rotor, a nacelle and a tower. The tower supports the nacelle, which typically contains a gearbox and a generator and that’s connected to the shaft that spins a rotor. So, you think about the wind blowing, through the rotor which has the blades on it, that wind energy is converted to mechanical energy. As some of the wind, flows through those blades, that mechanical energy is transferred through that rotating shaft to a gearbox which adjust the speed of the rotor and then into a generator all located up at the top of the turbine. The generator generates electricity which is then connected to the grid.

Dave Lingholm: So, you said top of the turbine because those tend to be pretty high and that’s a question that we see a fair amount on social media. Why do these things have to be so high?

Dave Harwood: Well, height, height is good for wind for two reasons. The higher you go, typically, the higher the wind speed you get and the more steady the wind is. And so, higher wind speeds, to some extent, result in more generation capability for the turbine and steadier wind speeds, more consistent wind speeds result in more efficient operation for the turbine.

Dave Lingholm: So, when it’s…That means that there’s a difference, you know, if it’s a windy day on the ground where we’re at, sometimes, you know, we do feel windy but we don’t necessarily see the turbines spinning. Why, why doesn’t it seem like they’re spinning when it’s already windy?

Dave Harwood: Yeah. So, yeah, that’s a good question. We get that a lot too where you, you might be driving around where we have some wind turbines and see that one turbine is spinning and one right next to it is not and wonder why that is. So, there’s a whole bunch of possible reasons for that. The first one perhaps is, is preventive maintenance. We take turbines down, offline twice a year, typically for a day each to do planned maintenance on those turbines and so you might see a turbine some at some point that’s its day. It’s having its planned maintenance being done, well, like I say, that happens twice a year. Another more frequent reason, actually is low wind speed. Our turbines, typically come online or start turning somewhere around seven miles an hour wind speed and again that’s when seven miles an hour up 300 feet in the air.

Dave Lingholm: Right.

Dave Harwood: And when you have winds that are in that range, that seven , eight , nine mile an hour range, it’s not unusual for one turbine to be seen eight, nine miles an hour and starting to get into its generation mode and the turbine right next to it still seeing six or seven miles an hour and it hasn’t quite started yet. If you watch closely, you can see actually gusts of wind or waves of wind flow through a wind park. You’ll see turbines come on and then go off and the ones behind them come and go off as that wind flows through the park.

Dave Lingholm: So, Dave, that makes a lot of sense when, you know, I’m by a wind park and I see one turbine spinning and another one that’s not or it seems like it might be getting started. But what happens when there are really strong winds out like when a cold front is coming through and, and there’s potentially severe weather coming by?

Dave Harwood: Right. Well, actually that could be the result of what’s in our turbines, an engineered safety mechanism that actually shuts the turbines down during very high winds for safety considerations. Our turbines are designed with very sophisticated weather gathering stations on each one and so they all collect data constantly on the weather conditions that, that individual turbine is seeing. And if a turbine sees over a 10 minute period, wind speeds in excess of 55 miles an hour, it will automatically shut itself down. And in fact, if it sees winds speeds in excess of 67 miles an hour for a shortest 10 seconds, it will shut itself down. And finally, if it sees wind speeds of 76 miles an hour or more for shortest of three second period, it’ll, it’ll shut themselves down. Even after they shut themselves down, they’ll continue to watch the weather and monitor that wind speed and, and if the wind speeds reduced enough for them to restart, there’s, there’s set up to restart themselves automatically. So, you will see on high windy days where certain turbines may be shutting themselves down for safety reasons.

Dave Lingholm: So, Dave, one of the things that I know people complain about because I’ve seen them do it online, is the sound that comes typically from wind turbines. .I’ve been on different tours of wind farms myself and haven’t noticed but I could be an outlier. How do you plan for complaints like that?

Dave Harwood: Yes. So, turbine sound is something that we get a lot of questions about. The fact is that community zoning typically limits sound from turbines at a home to about 45 decibels or less. And to put that in context, that’s approximately the level of noise you would get from a new high energy refrigerator in your home. So, it’s fairly quiet. But nonetheless, we ensure compliance with those zoning requirements by modeling a project’s acoustic characteristics before we build it, and then verifying compliance though studies after it’s up and running. And then, in addition, I would say that we typically site turbines, a quarter mile from a home anyway. So, we try to really minimize the noise concern.

Dave Lingholm: That makes a lot of sense and you talk about communities and zoning. I wonder how a wind turbine farm or park, how does that affect the local economy of the municipalities where they’re located?

Dave Harwood: Yeah. So, that’s a good question too. We provide that economic benefit in a number of different ways. Maybe the one, more obvious one, would be jobs. Creating jobs both during the construction phase of a project but then certainly after it’s up and running we hav, wind turbine technicians and engineers and business related folks helping us maintain and operate the machines. But also through property taxes. Wind parks generate substantial tax revenue for local communities and that’s a great benefit for roads and schools and hospitals and public works and all kinds of community services. And this is actually even in addition to the payments that we make to participating landowners within the park, either through easement payments or through operating royalties. To give you an example, in Huron County in Michigan’s Thumb, they reported tax revenue of $17 million from our wind energy parks in 2014 and 2015. So, a significant impact, I think, in a rural community.

Dave Lingholm: All right. So I also wonder, you know, we’ve talked about mitigating some of the sound, potential sound issues, making sure that there’s provisions for that and that you’re doing data modeling to take care of that. What’s being done to protect wildlife that lives around these wind parks?

Dave Harwood: Good question. So, contrary to what some folks might think, wind turbines do not pose a significant risk to birds or bats. In fact, national studies have shown that the percentage of avian fatalities from wind turbines is actually quite low. As low as 0.1 percent. In fact, cats, windows, buildings pose a much greater risk to the bird population. Specifically, at DTE, we take several steps to protect wildlife when we site a new wind project. We conduct habitats studies. We consult with the US Fish and Wildlife Service along with professional wildlife consultants. And when we site a park, we also voluntarily impose a 1,000-foot setback from forested areas to help minimize those interactions. And then after a park is constructed, similar to noise, we go back again and monitor wildlife interactions to ensure that what we planned is actually occurring.

Dave Lingholm: So, once all of those things are done, it sounds like a lot goes into the planning and the building. But does that make this a really expensive way to generate electricity? Or is it a cost effective way for a utility like DTE to generate electricity?

Dave Harwood: Yeah, so in the US, and in Michigan closer to home, wind power is becoming an increasingly cost competitive way to generate electricity. Over the past six years, the average cost of wind power in the US has declined 66 percent. We’ve seen a similar trend in Michigan. And it is the most effective and efficient and cost effective form of renewable energy today in Michigan. Until recently, the cost competitive nature of wind versus the traditional forms of generation, say natural gas, for example, has been supported by federal tax credits. These tax credits for new turbines are phasing out over the next couple of years. But the good news is that the actual cost of wind energy in Michigan is now on par with natural gas generation even without those tax credits. So, for utility building wind parks, it’s indeed a cost effective way to generate electricity and then once built, the park can operate for at least 20 to 25 years. Our experience shows that large scale wind generation is the best renewable investment for Michigan and for the foreseeable future.

Dave Lingholm: Well, Dave, thank you for taking the time today to answer my questions. It certainly has been a good education for me. I appreciate it.

Dave Harwood: Thanks for having me.

Dave Lingholm: And thank you for listening to our first ever Empowering Michigan podcast. You’ll be able to hear this regularly on our blog, Thank you.