How do solar farms work?

DUBUQUE — Solar energy in Linn County has received much attention — and contention — this year between the Duane Arnold Solar projects near Palo and the Coggon solar project.

Solar still is in its early days in Iowa, which nationally ranks 33rd for its installed solar, according to the Solar Energy Industries Association. The state’s current 517 installed megawatts — a boost from last year’s 159 megawatts — contribute less than 1 percent of Iowa’s electricity.

But solar energy is gaining momentum, especially as utilities better integrate it into their energy portfolios. MidAmerican Energy completed 141 megawatts of solar generation this year and is planning to add 50 additional megawatts. Alliant Energy is adding 400 megawatts of solar generation by the end of 2024, including the 200-megawatt Duane Arnold Solar projects.

The Gazette toured the West Dubuque Solar Garden — a 3.9-megawatt site sporting more than 15,000 panels — with Alliant Energy staffers to learn more about solar energy. We spoke with strategic project manager Justin Foss and Alliant spokesperson Morgan Hawk. Their answers are edited for brevity and clarity.

Q: What are solar panels are made out of, and how do they work?

Foss: It's mostly glass. There's a solid material in the middle that — when ultraviolet rays in sunlight hit it — generates an electrical current. That current goes to an inverter station that changes the direct current (like you would find in a car cigarette lighter) to an alternating current, which is what the power grid runs on. That inverter brings it to the substation and puts it on the grid.

There's two main types of structures we have that support our solar panels. A fixed-tilt system is mounted on poles and does not change its angle relative to the sun. These have lower costs to build and install. But because the tilt never changes with the sun throughout the seasons, it's a trade off for performance. The other type is called single-axis trackers that tilt toward the sun throughout the day. What we find is that, at the larger installations, you get enough improved performance to offset the extra cost for it.

Q: How does solar fit Iowa’s energy needs?

Foss: With solar generation, we see amazing performance from late spring all through summer and early fall, and then it drops off in the winter. Generation really ramps up between 10 a.m. until 4 p.m. to 6 p.m., depending on the time of year.

One of the best things about solar is that it's normally producing the most energy during our peak, when we need electricity the most. We see the most electricity use on the power grid between 4 p.m. and 7 p.m. when people are getting home from work. So, we’ve got wind the covers us at night and winter, and solar that covers us during our summer peaks. That's the one of the biggest values of solar for us.

Q: The Gazette recently reported a story about agrivoltaics, the practice of putting solar panels on top of crops. Is agrivoltaics a viable option in Iowa?

Foss: When you grow crops with agrivoltaics, you want to have a tractor. But tractors can't go under solar panels. The structures holding the panels need to be maybe three times as tall and substantially thicker and stronger because of the wind.

That means, in order to do agrivoltaics on a large scale, you sometimes double or triple the cost because of the physical structure needed to hold them down. It’s just cost prohibitive right now. We're partnering with agencies to figure out how we can do it on smaller projects.

Q: How do solar farms benefit the surrounding community members that don’t own the impacted land?

Foss: Alliant Energy, just like anybody's assigned electric utility, is responsible for putting as much energy onto the power grid as customers are taking off. Solar projects benefit the local folks because the electrons are most likely going to the homes around this area. Energy from our solar projects is going on to the power grid, and it's benefiting all of our customers across 83 of the state’s 99 counties. The projects also provide a tax revenue source that goes to the local community.

Hawk: Economic development is a big piece of this as well, because businesses have their own renewable energy goals. Businesses want to locate where they can receive renewable energy.

Q: What's the life span for a solar farm?

Foss: We plan for 30 to 50 years. We depreciate them over 30 years, but that's not to say that they don’t operate. They just have decreased performance but still operate quite well. It will be a mathematics equation that we’ll run in the future when we have to start making decisions: Do we just let them sit and do their thing? Is it better for our customers to replace them with new equipment and get all those increased benefits?

Right now, everybody asks, “Are all these solar panels gonna go to the landfill?” I don't know that. Because they're mostly made of glass, they're relatively easy to recycle. And in 30 years, they're still going to have between 80 and 90 percent performance left. That's why everybody's expecting a secondary market to come for these.

Q: How do you feel about the future of solar in Iowa?

Foss: I think that solar is going to continue to evolve. It will be one of the many ways that we generate electricity for our customers. It will never be the only way to generate electricity. No technology would be perfect enough to be the only way to generate electricity. But, with continued volatility in the commodities market for farmers, we're seeing more and more farmers reach out to us saying, “I would like to shore up my risk.”

If we think about them on the large scale, these solar farms are barely even a drop in the bucket on the overall generation portfolio of Iowa. We're going from zero solar to some solar. The question will be: How much solar do we want to have?

Brittney J. Miller is an environmental reporter for The Gazette and a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: (319) 398-8370; brittney.miller@thegazette.com