In 2014, the cosy community of Gimo, Sweden, situated about 120 km north of Stockholm, decided to restore its ice rink with a cooling system upgrade, using CO2 transcritical technology. After a bit more than one year of operation, the first season’s detailed evaluation shows that the ice rink is operating self-sufficiently, due largely to its advanced heat reclaim system.
CO2 efficiency leading to more than 60% cost reductions
During the first six months of operation the system’s total energy usage was 296 MWh, which corresponds to over 60 % in energy cost reductions compared to the previous system.
“Our electric energy consumption is way below what I thought was possible. It is half the cost compared to our second ice rink,” the rink’s Technical Operations Manager Lasse Karlsson concluded.
“We are very proud to have this facility. If I would build a new ice rink facility today, I would only consider CO2, because the benefits are so great,” he added.
Self-sufficient operation with heat reclaim
The evaluation of the ice rink energy and functional performance was carried out by energy analysis experts, Energi & Kylanalys, who found that although this year’s Swedish winter was a particularly warm one, the total recovered heat amounted to 466,000 kWh over 6 months. Even during the coldest days with -15°C ambient temperatures, the system managed to fulfill the heating requirements.
“The ice rink, with its combined refrigeration and heating system, has recuperated 71% of the available heat and covered 100% of the demand – no supplementary heat has been used. On average the total COP including both refrigeration and heating is 5.1 – with a constant heat supply temperature of 60 °C.”
Furthermore, the average heat recovery ratio over the season reached 104% – which means that slightly more heat than cooling was recovered and produced respectively. For 80% of the operation time, the heat recovery ratio was above 84%,” Energi & Kylanalys’ Jörgen Rogstam confirmed..
Facts about the “new” Gimo ice rink
- Refrigeration system: 100% CO2 with heat recovery
- Design capacity: 250 kW (single sheet)
- Single stage heat recovery: 60 °C constant forward temperature
- Total building area: 3,450 m2
- Heated area (20 °C): 680 m2
- Ice rink air temperature: Approx. 8 °C
- Electric energy usage: 296 MWh (6 months operation)
- Recuperated heat: 466 MWh (to all heating systems in the ice rink)
CO2 transcritical proving most efficient for ice rinks
Ice rinks consume an enormous amount of energy, with the average usage of a Swedish rink weighing in at around 1000 MWh per year. Typically, the refrigeration system, usually with a cooling capacity around 300-350 kW, is the main contributor, consuming about 43% of the total energy.
Until 2011, nearly all ice rinks in Sweden used ammonia/brine systems, and even today, those using CO2 use the refrigerant only in the secondary cycle in place of brine.
However, the success of the transcritical CO2 unit Mistral supplied by Green & Cool in Gimo shows the huge potential of CO2 as a refrigerant in this application.
The Green & Cool Mistral unit has 250 kW cooling capacity and is able to recover most of the waste heat from the cooling process to use for site heating and hot water. Any excess heat is transferred to five 200-metre-deep drilled wells, which provide geothermal energy storage.
About Green & Cool
Green & Cool uses environmentally friendly carbon dioxide as a refrigerant, and supplies a range of cascade and transcritical solutions for commercial needs and larger applications like ice rinks. Green & Cool’s wide range of products appeals to companies of various sizes that are ready to invest in modern refrigeration equipment that meets strict environmental, financial and reliability criteria.