Brownfields come in all shapes and sizes, from a few blocks to many acres, and all locations, from inner cities through suburbia and into rural areas.

They get their name because they have environmental contamination. And their owners, in some cases public officials, would like to overcome that obstacle to return them to some kind of productive use.

Sometimes, such as with the site of the former Ford Motor Co. assembly plant in St. Paul, the contamination is manageable enough to remove safely and allow for a new life as tax-generating, privately redeveloped properties.

At other sites, such as with the dozens of closed and "capped" landfills that dot the state, the environmental risks and physical limitations remain too high to let them be used for housing, shopping centers or industrial facilities.

But now an alternative to commercial redevelopment is emerging: conversion into solar power installations.

Brownfield advocates locally and around the country are touting the unique suitability of many former landfills to host solar panels, thereby wringing at least some value out of even the worst contamination sites.

"Using capped landfills for solar development is something that has the potential to provide a great amount of energy to the country," said Joe Mahowald, a program associate with Minnesota Brownfields, a nonprofit group devoted to promoting the redevelopment of contaminated lands. "There are thousands of landfills that meet the necessary criteria for solar development."

Those prerequisites, he said, include open land space, optimal solar exposure, access to service roads, compliance with zoning regulations and access to the electric grid.

"Solar development on landfills can reduce energy costs in that particular area," Mahowald said. "And many states [including Minnesota] now have renewable energy quotas. Utilities in those states are often eager to expand their renewable energy output."

In Minnesota, three capped landfills have become hosts to solar installations. Two of them have been established by the Minnesota Pollution Control Agency, or MPCA, and are being used to provide power for equipment set up at the sites to collect the methane gas and leachate produced by decomposing fill.

The state-owned Lindenfelser Landfill in St. Michael and the one-time Washington County landfill in Lake Elmo — which in 2008 required the biggest cleanup in state history — each have solar panel installations. MPCA spokesman Walker Smith said the agency built them in 2015 using locally manufactured panels that qualified for a Made in Minnesota Solar Energy Production Incentive.

"Those sites can't be redeveloped into something like a shopping center, or even a passive use such as a park, so they're perfect candidates for use as solar installations," he said. "Also, unlike a lot of urban brownfields, they're in isolated areas and usually are not close to highways, railways and other infrastructure that would make them useful as, say, new industrial sites."

Smith said the solar array in Lake Elmo is supplying 80 percent of the power for its collection system. The MPCA's electricity bill there was more than $4,500 in fiscal year 2013.

The state's other landfill solar installation is in Hutchinson, where the city is partly powering its wastewater treatment plant with a 400-kilowatt solar array atop what used to be the municipal dump. That project, completed in 2015, was made possible with a grant from Xcel Energy, which is using it to demonstrate the statewide potential for solar brownfield redevelopment.

The ultimate goal of brownfield advocates is to look at many more contaminated sites, beyond just former landfills, as possibilities for the expansion of solar power. One such candidate is "Area C" at the St. Paul Ford plant, a 22-acre site along the Mississippi River which was once used by the automaker as a dump site. Its "cap" is a concrete parking pad.

While Ford and the MPCA are continuing to assess exactly what was buried there over the years and its level of contamination, renewable power advocates are already pushing for re-use as a solar installation.

Don Jacobson is a freelance writer based in St. Paul. He is the former editor of the Minneapolis-St. Paul Real Estate Journal.