The largest system in the Upper Midwest for converting solar energy to electricity would be installed atop the Minneapolis Convention Center under a proposal that advanced Monday.

The rooftop installation would cover the equivalent of nearly four football fields and supply some of the power for the center.

A Minneapolis City Council committee directed its staff to keep negotiating a proposed 20-year deal with EyeOn Solar LLC of Boulder, Colo. But some members expressed caution.

"I'd hate to see us hurry to put on our happy environmental hat," said Council Member Lisa Goodman, who questioned the proposal closely.

The project needs to be completed in December to take advantage of the federal tax incentives set to expire.

The committee endorsed continued talks with the provision that any proposed deal come back to the council for review.

According to staff analysis, the project's entire output would supply only about 5 percent of the center's annual power needs.

"EyeOn Solar is one of a number of companies that have sprung up in the last two years that are essentially ... based on tax incentives," said David Morris, a vice president of the nonprofit Institute for Local Self-Reliance.

EyeOn is committed to installing one megawatt of photovoltaic cells in a deal with the city of Boulder, Colo. Although it received approval late last year, it is behind schedule in beginning the installation, according to Ned Williams, that city's public works director.

The Minneapolis project would install 3,000 panels of thin photovoltaic cells with a capacity of 600 kilowatts on utility areas on part of the convention center's roof. One-third would be oriented for maximum energy capture, one third to capture solar energy at the building's peak energy use, and another third for Xcel Energy's peak demand.

The project would be partially financed by $2 million from state-mandated renewable energy grants funded by Xcel. The deal is also financed by federal renewable energy tax credits and accelerated depreciation. The city's role would be to provide the rooftop site and agree to buy the power for 20 years. Initially, the power cost probably would represent no savings for the city compared to what it pays Xcel, but the city would lock in its costs for 20 years if electricity charges increase, said Greg Goeke, the city's director of property services.

Morris said that the state grants were intended to develop in-state expertise, but the money for the Convention Center installation would go to a Colorado developer: "What is left in Minnesota after the project is completed will be an impressive tourist attraction and bragging rights by Minneapolis, but no Minnesota-based engineering or manufacturing or design expertise."

Steve Brandt • 612-673-4438