At its most basic, refrigeration is based on the fact that heat always travels from a warm medium to a cooler one in an attempt to reach thermal equilibrium. This principle of thermodynamics forms the basis of how mechanically frozen ice rinks are created and maintained.

Ice Rink refrigeration systems can be one of two different types – direct or indirect. In an “indirect” refrigeration system, a liquid refrigerant absorbs heat from a secondary liquid, or brine, which then pulls heat out of a rink floor as the brine is pumped and circulated through pipes embedded evenly throughout the floor. In a “direct” system, the floor’s heat is removed by pumping the primary refrigerant directly through the floor’s pipes—there is no secondary coolant involved. Regardless of whether it is a direct or indirect system, the chilled liquid flowing through the pipes is kept at 32° F / 0° C, so that any water placed on top of the slab freezes and becomes the ice-skating surface that we see and use. A level of insulation is set beneath the concrete slab so that the ice can shrink and expand as needed.

Until somewhat recently, indirect systems were the choice of refrigeration specialists and rink operators seeking safer control from the potentially harmful refrigerants used in such applications, such as ammonia, which is toxic, and to a much lesser degree, R-22 (in older systems), whose phase-out is well underway.

Direct systems have proven to be more efficient by circulating their refrigerant directly through the nearly 10 miles of piping that traverse a typical rink floor. Since the sheer length of piping involved poses a potential for leaks, the characteristics of the refrigerant selected for the system become the main determining factor for whether to go direct or indirect. Although ammonia’s pungent odor can be detected once it reaches a certain concentration, the toxicity and flammability issues are then in play.

Over the past decade, CO₂ has been gaining traction in ice rink applications. It was not until 2010 that the world’s first 100% CO₂-based refrigeration system deployed in an ice rink was completed in Marcel Dutil Arena in Quebec, Canada. In 2012, a comparative study of refrigeration systems for ice rinks in Quebec was undertaken by Canada’s CanmetENERGY Research Centre. They compared 12 typical refrigeration systems currently offered for ice arenas in the market and found the CO₂/R744 system as being the most energy efficient.

Hillphoenix has been at the forefront of CO₂ refrigeration system technology and design over the past decade. The Hillphoenix CO₂ booster system serves as an ideal solution for direct ice rink applications, capitalizing on the inherent advantages of CO₂ as a refrigerant, including its thermal efficiency and environmentally benign, non-toxic and non-flammable nature.