(Town of Beloit) Neil Johnson, Gazette
As Alliant Energy engineer Kim Halverson drove along a gravel access road behind Alliant's Riverside Energy complex, he motioned toward dozens of steel posts in arrow-straight rows nearly 200 feet long.
The posts are a framework, part of a rack system that will support thousands of solar-collecting panels in a 2.3 megawatt solar energy facility under construction at Alliant's facility on Beloit-Rock Townline Road.
“I call it The Vineyard,” Halverson said.
It's not a bad analogy. Grapes on the vine might be nature's most capable sun-harvester. Yet the solar energy field in the town of Beloit might have one up on the grape.
Grapes can't move, but Hanwha's solar panels can.
Alliant is partnering on the project with Korean solar energy firm Hanwha Q Cells USA. The rows of solar collecting panels—7,740 in all—are geared to tilt in electronically-controlled motion to track the sun across the sky.
As early as June, Alliant plans to activate its seven solar-collecting arrays built on 17 acres of capped coal-ash landfill along the Rock River.
It's the largest solar field ever built for use by a Wisconsin utility and the first of its size here to use technology that moves solar panels to more efficiently track the sun.
Hanwha is paying to develop the $5 million project and will own and operate the solar facility. Hanwha plans to analyze the solar collectors' efficiency and output daily and seasonally.
That will give Alliant time to study how solar energy production performs at the facility, Halverson said.
If over the next decade the solar plant performs as expected, Halverson said, Alliant has an option to buy the site from Hanwha.
Meanwhile, through a 10-year power purchase agreement, Alliant plans to buy solar electricity and push it out to the grid in tandem with electricity from Alliant's other generation facilities at the town of Beloit site.
Alliant would sell the electricity to customers at market rates.
Halverson, who is the project's manager for Alliant, said the solar arrays will collect and convert enough of the sun's energy year round to power the equivalent of 500 residential customers, which he called a “conservative” estimate.
Earlier estimates by Alliant were that the solar array could generate enough power for as many as 2,000 residential customers.
The solar arrays are being built in a semicircle with an access road at the rim of a terraced hillside that breaks the site in two halves--the high end and the low end of a manmade mound.
Unlike many of the mounds along the Rock River between Janesville and Beloit, the hump at Riverside complex wasn't built by ancient Winnebago tribes. It's a capped coal-ash landfill, a dumping ground where utility operators for decades buried remnants of coal burned at the now-defunct, Rock River generating power plant at the east end of the Alliant property.
“That's maybe the most significant thing about this site,” Halverson said. “It's the first time in Wisconsin anybody has built a solar energy site on top of a (reclaimed coal ash) landfill.”
SLOW TO SOLAR
The state Public Service Commission estimates that electric utilities in Wisconsin can now produce two megawatts of their own solar electricity—a sliver of less than 1 percent of the total power state utilities generate.
The utilities sell less than one-quarter of that capacity to customers, according to the PSC.
Solar makes up the smallest cut of electricity generated and sold by Wisconsin utilities through the use of renewable energy sources, including hydropower, wind and biomass.
Wisconsin is among 38 states in which state law permits utilities to buy solar power through purchase agreements with companies that own solar systems but aren't registered as utilities.
That's how Alliant and Hanwha's partnership is set up, and it's the largest such arrangement involving solar energy in Wisconsin.
The bulk of solar electricity is still generated by private residents, municipal energy cooperatives or businesses. Those are commonly rooftop panels on homes or commercial buildings.
Some utilities here are beginning to carry out modernization projects that would retrofit coal or gas-fired plants to operate more efficiently and cleanly.
Some utilities, including Alliant, are phasing out aging coal-fired plants and replacing the lost capacity with plants that use cleaner burning natural gas—an energy source which is in abundance in the region and can be supplied through pipelines.
Many power utilities are offering a growing blend of renewable energies. Some, like Alliant, are spending millions of dollars outfitting their own offices and electric plants with solar panels intended to increase the efficiency of their own operations.
Alliant plans to build another solar field alongside the planned, 700-megawatt, gas-fired power plant the company plans to break ground for this summer at the Riverside Energy complex.
Alliant has said it would use that solar plant to offset operations at the gas-fired plant.
That solar plant, along with one now being built, will eventually give Alliant access to up to 4.3 megawatts of solar power for sale and for its own use at the Riverside Energy complex.
While that would still be just a fraction of Alliant's overall energy portfolio—including all renewable sources—it's the biggest commitment yet by a Wisconsin utility to jump into solar.
Such moves are somewhat tied to the looming draw-down of coal burning for electric generation—part of a federal plan to cut emissions of carbon dioxide and other greenhouse gases.
But in other ways, the shift is tied to goals the state has set through its Renewable Portfolio Standard, a benchmark that requires utilities to offer renewable energy.
The town of Beloit solar energy plant allows Alliant to make small steps toward meeting state benchmarks for offering renewable energy alternatives to customers.
Plus, the solar plant offers a suitable use for a former landfill parcel that otherwise would be unused.
Normally, solar arrays are mounted on pilings sunk into the ground, but state and federal rules prohibit development on capped landfills that disturbs or breaks open the soil, Halverson said.
To meet state Department of Natural Resources approval, the project had to be specially engineered.
Designers decided to use pre-cast concrete ballasts, 1,655 of them, which are designed to float on the soil that caps the landfill and bear the weight of the solar panels and racking system.
The 7,740 solar panels weigh a total of 189 tons, according to Hanwha product specifications and project notes. Then there's the weight of the pre-cast concrete, reinforcing steel and drive shafts that make up the racks that hold the panels.
Because the ground on landfills can shift more than on other sites, project engineers designed metal I-beams to tie the solar panels and racks into the concrete slabs using a special, bolted boot that can adjust the racks up and down if the soft terrain shifts.
That would prevent the rows of solar panels from becoming skewed and washing other nearby panels in shadows, Halverson said.
A NEW LANDMARK
Looking east across the solar arrays is the former source of the coal ash that filled Alliant's landfill, the now defunct Rock River Generating Station.
It's a large, red brick powerhouse on Townline Road with white and red candy-striped stacks.
That's a well-known landmark for regional air traffic and for anyone driving along Interstate 90/39 between Janesville and Beloit.
The plant, owned by Alliant, hasn't run in any capacity for more than a decade.
Soon after the solar arrays begin operating and even before Alliant finishes building its planned, 700-megawatt gas-fired plant at the Riverside complex, the old coal plant is going to be gone.
Alliant decided early in 2015 to demolish the old plant and nearby outbuildings. Halverson said the plan is to tear down the plant and its smokestacks before the end of the year.
Halverson said Alliant tried to convince investors to buy the huge facility for reuse, potentially as an indoor sports complex.
The Southern Wisconsin Regional Airport has a flight pattern that runs above Alliant's Riverside Energy complex, and the new solar field will act as a visual reference for pilots the way the old coal plant now does.
Halverson said the solar panels would produce a flash similar to sunlight reflecting off water that at times would be visible to airplane pilots.
But he said the Federal Aviation Administration has determined the solar arrays will be beneath the threshold for visual ground distractions.