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cause the operational costs to be around $15 per 1000 gallons of processed water. Instead of requiring chemicals, the reverse osmosis systems require additional pumping power to force the water through the filtering membrane. Operational costs for the reverse osmosis systems average $3 to $5 per 1000 gallons. The paybacks on both systems typically span 6 to 10 years. The paybacks can be reduced by a change in the temperature of the ice sheet. With the use of demineralized water the temperature of the ice sheet can be raised slightly to accommodate the reduction of energy needed to freeze pure water as compared to water with dissolved solids. Several arenas that use either temporary ion-exchange tanks or a reverse osmosis flood water demineralization system are listed below. Demineralization Type Reverse Osmosis, Tanks Reverse Osmosis Reverse Osmosis Reverse Osmosis Arena Bloomington Ice Gardens Hutchinson Civic Arena Cottage Grove Arena Victory (Minneapolis) Contact Person Andy Baltgalvis Marv Haugen Dean Mulso Virgil Oldre Phone (612) 948-8842 (320) 234-4227 (612)458-2846 (612)627-2953 Electric Ice Resurfacer Ventilation with outside air is extremely important in ice arenas where resurfacers driven by internal combustion engines are used. The airborne pollutants emitted during the combustion process must be removed from the space or diluted to a concentration level that will not harm arena occupants. A fine balance must be found to ensure that sufficient outdoor air is provided to dilute combustion contaminants, while minimizing excessive levels to reduce dehumidification and heating loads. Using electric resurfacers eliminates the need for extra outdoor air ventilation to dilute combustion products. The only remaining need for ventilation is to assure adequate occupant comfort. Electric resurfacers have been improved with technology from the forklift industry. Electric powered forklifts have been in use for many years and have performed indoors without problems. The power requirements of an ice resurfacer are somewhat higher than a forklift, but this is easily overcome with the addition of a larger battery pack. The alternative to the battery operated machine is to plug the resurfacer into an electrical supply grid. This is accomplished with the use of a tether that is supported in the ceiling of the arena. Costs for electric resurfacers range from $72,000 for tethered machines to $75,000 for battery models. Simple paybacks for electric resurfacers can be somewhat high when only considering the incremental cost over a new propane resurfacer. Anew propane powered resurfacer has a cost of $55,000 which results in an incremental cost of $20,000. The resulting payback is typically over 10 years. Paybacks are reduced when operational costs are considered. The typical propane resurfacer will use approximately $1,620/yr in propane where as an electric resurfacers performing the same number of resurfacings will use only $420/yr, resulting in a $1,200/yr savings in operational costs alone. Replacing a propane powered resurfacer will provide the immediate benefit of improved indoor air quality even though the economic payback is longer than for many other improvements. Energy Improvements in Minnesota Public Ice Arenas Project Page 5 Center for Energy c~ Environment