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outside air through a condenser. In order for heat to flow from the refrigerant in the condenser to the outside air, the refrigerant must be at a high temperature and pressure (referred to as the head pressure). This high temperature and pressure is generated by the compressors that pump the refrigerant through the various parts of the refrigeration system. Since the compressors are the primary energy users in the refrigeration system, reducing the head pressure will save significant amounts of energy and reduce wear on the compressors. Many direct refrigeration systems will operate properly with head pressures as low as 150 psi, while many indirect systems (those with thermostatic expansion valves) may need higher pressures of 175 psi. Typical annual energy cost savings that can be realized with only a 20 to 25 psi reduction are $400 to $1,000 for asix- month arena and $900 to $1,800 for facilities that operate 9 months or more. The head pressure can be reduced in two ways: (1) by manual adjustment or (2) by replacing standard condenser controls with more efficient automated condenser control systems (see refrigeration system section). The refrigeration industry has traditionally encouraged maintaining a higher than necessary head pressure by turning off fans that blow outside air through the condenser and/or by using a pump that sprays water over the condenser. These approaches are very conservative in terms of ensuring adequate cooling of the ice under the most taxing conditions; however, these practices unnecessarily increase energy costs and wear on the compressors during periods of normal arena operation. This energy conservation method has already been successfully implemented in several Minnesota ice arenas. LIGHTING IMPROVEMENTS Efficient Lighting Fixtures for Public Spaces A number of existing technologies can make interior and exterior lighting significantly more energy efficient. The impact any particular lighting improvement has on operating costs depends heavily on the hours of operation. Obviously, fixtures which are operated 24 hours a day will provide more savings from high efficiency improvements than similar fixtures that only operate for a fraction of each day. Maintenance costs for replacing spent fixtures must also be considered when calculating the paybacks of lighting improvements. There are six main types of lighting improvements which are feasible in most ice arenas. Ice sheet lighting recommendations are dealt with in the next section. Replacing standard incandescent lamps or "light bulbs" with more efficient fluorescent lamps will use 30 to 80 percent less electricity per lamp while producing the same light levels. In addition, maintenance costs will be reduced since fluorescent lamps last 5 to 12 times longer than standard incandescents. 2. Replacing existing four or eight foot fluorescent fixtures with high efficiency fluorescent T-8 lamps and improved electronic ballasts can provided significant cost savings. 3. Public areas such as halls, corridors, and lobbies often have more fixtures than are needed for desired light levels. Wasted light can easily be eliminated by either using lower wattage ballasts (dewatting) or disconnecting unnecessary ballasts (delamping). Page 2 Energy Improvements in Minnesota Public Ice Arenas Project Center for Energy & Environment