Brooklyn Park officials think their reengineered, super-efficient ice arena is beyond cool.

So on Saturday morning, the city will throw a grand-reopening party.

But the good feelings go beyond a return to normal skating hours after six months of disruption. City officials want to collect data for a year, but they believe the stats will show that they now have the most energy-efficient ice arena in North America.

Thanks to a $4.5 million overhaul, the arena requires half the energy it once did to perform at the same capacity, said Mark Rasmussen, project director for McKinstry Co., the contractor that completed the overhaul as part of a $6.3 million citywide energy-efficiency project.

The technical details of the new system could make the average person's brain do a triple axel.

At its most basic, the arena now is operating on one mechanical system rather than the dual systems that once chilled the two rinks, built in 1983 and 1997.

The compressors that run the refrigeration system now can do so more efficiently because they are constantly cooled by a stream of untreated 51-degree water that the activity center intercepts as it flows between the city's well and treatment plant, about half a mile away.

The system also can react to, and make use of, warm and cold outdoor air. And it is able to employ excess heat and cold, for example, by using waste heat to warm the water used to resurface the rinks, or to provide heating or cooling elsewhere in the Community Activity Center.

McKinstry, based in Seattle but with offices in Brooklyn Park, completed the work as a design-build project, meaning it oversaw both aspects of the job.

Even with the high-efficiency features, Rasmussen said, the design-build approach allowed the city to complete the project at about the same cost as a traditional retrofit, which would not have provided the added long-term operational savings, and would have made the project's very tight timeline nearly impossible.

Much of the project was funded through a combination of grants, utility rebates and an infusion from the city's heritage fund. Part of the cost also came from a bond the city took out on the larger project. Before long, Rasmussen said, operational savings will offset the cost of the bond payments for the arena project, and it will operate without city subsidies.

The citywide project also received $650,000 in federal stimulus money, which the city targeted for high-efficiency lighting improvements in the Community Activity Center and across the city, said Central Services Superintendent Steve Lawrence.

Lawrence beams as he describes the project. "It's not doing what they said -- it's better," he said. "We've created a new approach."

Maria Elena Baca • 612-673-4409