HOUGHTON, Mich. — Michigan Technological University replaced the ice-making system in the John MacInnes Student Ice Arena last summer, removing the building's original Freon 22 direct system and installing an ammonia brine indirect system.
The reviews of the ice from rink users are very positive, but the most impressive part of the new system might be its reduced impact on the environment and the University's budget.
"What you have is the most environmentally-friendly and energy-efficient system available," said Mark Rodorigo, owner and CEO of Commercial Refrigeration of Virginia, Minn., which did the initial installation of the new system. "We replaced the Freon R-22, which is an ozone-depleting chemical, with anhydrous ammonia, an all-natural substance. Plus, we're reclaiming the waste heat. You have reduced your carbon footprint tremendously."
A calcium chloride (saltwater brine) is chilled by the anhydrous ammonia refrigerant in a large shell and tube heat exchanger called the "chiller". The brine leaves the chiller and is pumped through 13 miles of tubing inside the rink's concrete slab. It leaves the mechanical room at 12 degrees and returns a few degrees warmer back into the chiller.
Heat is created when the ammonia is compressed to be used as a refrigerant. This high-temperature gas travels to three large water tanks that heat 100 percent of the domestic hot water used in the ice arena. The gas also feeds into a titanium-plated heat exchanger which maintains the water temperature for the Student Development Complex swimming pool and dive tank.
The last step in the process is the final cooling of the gas by an evaporative condenser. Because the gas has already cooled by going through the water tanks and heat exchanger, the condenser uses less energy, water and chemicals.
One other bonus feature of the system is utilizing the waste heat from the compressor crankcase oil. The hot oil is pumped through a small heat exchanger where it is cooled. The removed heat is then sent through the rink subfloor to prevent frost from forming under the rink's insulated concrete slab.
Dave Nordstrom, Michigan Tech's associate athletic director and building manager for the SDC and ice arena, is really pleased with the early returns on the new ice plant.
"Mark and Commercial Refrigeration have done an outstanding job with this project," said Nordstrom. "This new system is not only better for the environment, it's going to save the University thousands of dollars."
Early estimates put the annual savings at $40,000.
"Anhydrous ammonia is a lot cheaper than R-22," said Rodorigo. "You're also saving money on heating your hot water, your swimming pool and your subfloor. You're also saving money on water and chemicals used in the evaporation condenser because you're not emitting as much heat into the atmosphere.
"I would think that a lot of other universities would be looking at this system."
The John MacInnes Student Ice Arena was built in 1971. It is home to the Michigan Tech Huskies hockey team and used for many other purposes as well including high school and youth hockey games, figure skating, concerts and the University's spring commencement.