The biggest solar power project in Minnesota won approval Thursday from state regulators.

The $250 million Aurora Solar Project by Edina-based Geronimo Energy calls for the installation of ground-mounted solar panels at 21 mostly rural sites from Chisago County north of the Twin Cities to Waseca in southeast Minnesota. Geronimo plans to finish the project in 2016 and sell the power to Xcel Energy.

“This signals that something big is happening in solar energy in Minnesota,” said Michael Noble, executive director of Fresh Energy, a St. Paul nonprofit that advocates greater reliance on renewable energy.

It is by far the largest solar project approved in Minnesota, and in one sweep increases the state’s solar output sevenfold. The combined 100 million watts is the equivalent of a small traditional power plant. The largest of the 21 solar sites, near Paynesville, will cover an area the size of Lake of the Isles in Minneapolis.

The state Public Utilities Commission (PUC) voted 3-0 to approve a permit for project, but rejected three of the original 24 sites, in Pipestone, Wyoming and Zumbrota, because of local land-use objections. Another site, near Hastings, is in jeopardy because of recently discovered soil conditions.

Geronimo Energy said the project will go ahead without them.

Graphic: Solar arrays across Minnesota Graphic: Solar arrays across Minnesota

“We had offered more sites than we would use because of the need for flexibility if a site ended up not being constructible,” said Betsy Engelking, vice president for policy and strategy at Geronimo.

In a major victory last year, the project successfully competed in a PUC bidding process against natural gas projects. It aims to be a cost-effective means to supply Xcel Energy extra power on high-demand summer days. Geronimo plans to achieve this by installing solar panels that track the sun from east to west, capturing solar power late in the day when electricity demand rises.

To avoid expensive transmission lines, Geronimo selected solar sites near existing electric substations, and will send power straight onto distribution lines. Most of the solar sites now are farmland, and at the request of environmental officials, Geronimo agreed to put bee-friendly native plants under and around the solar panels.

Enel Green Power, a global renewable energy company, will own and operate the solar project, selling the power to Xcel, the Minneapolis-based power company serving 1.2 million electric customers in Minnesota.

First of a wave

Even more solar is coming to Minnesota under a 2013 solar energy law that requires investor-owned utilities like Xcel to get 1.5 percent of their electricity from the sun by 2020.

Xcel has signed deals with three other energy developers to build large solar projects in the state.

One of them near North Branch would be the same size as the Aurora project — but all the panels would be installed on one site. Those projects are now seeking permits from the PUC.

One Aurora site that the PUC rejected was in Pipestone, in the southwest corner of the state.

It is adjacent to a residential area. With homes on the south side of the project, it would be difficult, if not impossible, to screen from view the acres of solar panels. Any barrier, such as trees, likely would have blocked the sun.

“The record clearly demonstrates that’s probably not such a great site,” Suzanne Steinhauer, a state Commerce Department official who reviewed the site, told the commission.

A solar site off Hwy. 52 in Zumbrota was rejected because it lies in an area where local and state governments have upgraded roads and utilities hoping to attract commercial and industrial projects, which pay higher property taxes than solar projects.

“We weren’t against solar, just the area it was placed in,” Zumbrota City Administrator Neil Jensen said.

Weighing local concerns

State law gives the PUC sole authority to approve or reject large energy projects — trumping local zoning laws — although regulators must consider local concerns. Some legislators have pushed for a change in state law to give local governments more say.

PUC Chairwoman Beverly Jones Heydinger said she recognized that communities raised issues with solar projects.

“Because this is the first facility that we are siting, we are particularly sensitive in having it go as smoothly with local units of government as possible,” Heydinger said.

Engelking said Geronimo hopes to begin construction this fall, using roving teams of construction workers who go from site to site.

Earth-moving crews would start off, followed by those who install the solar panel supports, then teams that install panels and do other work.

To retain eligibility for an expiring 30 percent federal solar investment tax credit, the Aurora project must be generating electricity by the end of 2016. After that, the tax credit drops to 10 percent.