By Brendan Lenko, P.E. Imagine your living room with 20,000 pounds of frozen ice on the carpet, then dropping 100 gallons of hot water on your kitchen floor. Then try to keep the occupants warm and comfortable; try to keep the ice frozen; and try to keep your home dry and free of condensation on the walls, glass, and ceiling. The idea becomes ever harder if your front door was constantly open as hundreds of people come in to enjoy the ice; and even worse if you had to ventilate with 10,000 cfm of hot, humid, outside air. Even if you have all the refrigeration, heating and dehumidification you need, keeping the people comfortable, the ice cold, and the space dry is still an extremely difficult job….But, this is exactly what hundreds are ice rinks are faced with on a regular basis. By their very nature, ice rinks are a different beast. They combine an industrial refrigeration process, in the very same room with spectator occupancy requiring comfort heating & dehumidification, and right next to shower and change rooms needing exhaust air flow and even more heat. Commercial offices, swimming pools, banquet rooms, daycare, play rooms, gymnasiums, fitness rooms, and arcades are all other types of space within an ice rink facility that all have different requirements. In most buildings, human comfort can be achieved by simply adjusting a thermostat. In an ice rink however, it is not that easy because we want to keep the ice cold while keeping the rest of the space warm. Contrary to many beliefs, we don't want to create a freezer inside the ice rink. The ice is the only part that has to be frozen. The rest of the space should be warm and comfortable for the occupants, and this is the challenge. Back to Top If we overheat the space it will impose an unnecessarily high heat load on the ice, causing soft ice and/or higher refrigeration energy costs. Conversely, if we over cool the ice it will cause the rink space to become colder than necessary or cause higher space heating energy costs together with increased costs on refrigeration not to mention the poor brittle ice conditions. An ice rink poses a challenging balancing act to facility operators, ice rink architects & designers, as well as engineers. Too often the mistake is made where the designer attempts to make the ice rink like a freezer with really cold ice and such high building insulation levels and powerful air circulation within the rink that the entire rink is extremely cold as well. This then gets combated with huge amounts of heat in an attempt to keep the space warm. The end result of comfort might be achieved but not likely without high energy costs in refrigeration, space heating and costs of running many fans for air circulation. Proper operation and design of an ice rink requires a tight balancing act between space heating, ice refrigeration, dehumidification, arena air circulation and outdoor air ventilation. If any one of these is not being properly managed various problems can develop. For example, if the ice is kept too cold, it could cause colder surface temperatures within the rink and result in condensation and dripping on the ice. This particular problem is worsened if outdoor air is added without sufficient dehumidification. Although heating up the rink will help solve the problem, there is a huge energy penalty in heating the building space with such cold ice temperatures. Back to Top As another example, too much air movement via fans and dehumidifiers in the rink can help reduce fog and condensation, but can add an additional convective heat load on the ice. That is, as the speed of the air over the ice increases, so does the heat transfer from the air to the ice. Then, the refrigeration system will have to work harder and longer to remove this heat form the ice. Conversely, if the air handling is designed without as much movement, it will have a natural tendency to stratify leaving the colder air near the ice and the warmer air up higher above the ice. When properly done, this can save refrigeration costs because the ice is constantly exposed to colder air moving slowly, and the heat is left at a height where occupants benefit from it. Further, the warmer air which naturally stratifies higher above the ice will also aid in comfort of spectators keeping them warmer as well. Sometimes a very small adjustment in an ice rink operation can have a dramatic effect on energy, comfort, condensation, and even ice quality. But to achieve the proper results, a more engineered approach is often necessary. One must understand the relationships between space heating, ice temperature control, dehumidification and air movement within the rink. One particular twin sheet facility, the Tomken Twin Arena had suffered with extremely high refrigeration energy costs, together with nuisance occurrences of condensation, fog and dripping onto the ice. After reviewing the design and operation of the facility, it was found that their refrigeration controls were controlling the ice inefficiently causing the ice to be colder than necessary most of the time. This was compounded by uncontrolled amounts of outside air entering the building causing high amounts of fog and condensation in the rink. Although the rink had dehumidification, it was simply assumed that there was not enough capacity to handle the moisture loads. For years they attempted to deal with the problem by running more blowers and fans to break up the fog and prevent condensation. Although this reduced the effects of the moisture, it did not take care of the problems all the time and the cost of operating the fan and blower motors was still present. More importantly, with the added air movement, this solution caused a greater heat load on the ice and higher refrigeration energy bills. Back to Top An engineered approach to this facility resulted in several changes that solved problems while saving a great deal of energy. Several adjustments to their existing DDC control system allowed the refrigeration to be controlled directly from the ice temperature. This maintained the ice at the desired temperature all of the time without the wasteful overcooling that plagued their original refrigeration controls. This adjustment alone helped reduce some of the fog and condensation. This is because at night, the ice temperature did not fall as cold as before and the rink space was left in a warmer state. These control adjustments also reduced refrigeration energy costs because the ice was not kept as cold as before for the entire day. With the new method of control, infrared ice surface temperature sensors were placed above the ice and RTD probe sensors were installed in the slab. The operators could then choose which form of ice control they desired. With the control adjustments, the rink was also able to start setting up their ice temperatures at night generating even more energy savings and further preventing fog and condensation. Additional energy savings came from utilizing their existing two speed brine pump motors in a more cost effective manner. Because the compressors and pumps were controlled from the same source, the actual ice temperature, it allowed the pumps to be shut off when the compressors were off and to run when the compressors were on. An intermediate step was added to allow the pumps to run on low speed under part load conditions. The end result was one which operated the pumps in an optimum manner, turning on only when they were needed. Back to Top This engineered evaluation of the Tomken Arena also uncovered some additional areas of energy waste. Several pumps which were only need for air conditioning were found running in winter months and consequently shut off. Malfunctions in their air handling equipment were discovered and remedied, and some original design flaws were repaired. After all of the above changes were implemented, this twin rink went on to save approximately $4000.00 per month in the next two months and similar results in the following months. With project costs of under $20,000, this facility managed to pay off the project in nearly 6 months and generate positive cash flow after that time. There have been many similar projects where moderate improvements in ice rink operation result in substantial energy savings. Ice rinks naturally use much more electrical energy than most other types of facilities. Because of the complex relationships between the refrigeration, the dehumidification, the heating, and the outdoor air ventilation, it is no wonder that rink operations often fall out of line resulting in high energy costs. It certainly makes economic sense to have qualified personnel, trained in these areas, to review your facility and help identify areas of energy waste. Often some significant savings can be achieved at a much smaller cost. Back to Top About the Author: Brendan Lenko, P.E. is a professional engineer and President of Energy Ice. Through his career, he has been involved in hundreds of low emissivity ceiling projects through out the world in consulting, design, energy analysis and project management capacities. His experience includes projects in countries such as Japan, Russia, Finland, Sweden, Norway, Denmark, Switzerland, Germany, Indonesia, as well as Canada and the USA. If you have questions relating to low emissivity ceilings, ice temperature controls or just energy conservation & engineering in ice rinks in general, you can reach him in Canada at 905-632-8840. |
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