Data from more than 23,000 operating hours of CO₂ refrigeration of reefer containers, open cycle R744 system and CO₂ compressors for MAC were the topics highlighting the opportunity for CO₂ refrigerant in the transport sector. Also presented at the ATMOsphere Europe conference were: heat recovery in commercial and industrial CO₂ transcritical systems saving more than 1,000 tons of CO₂-eq per year or reducing running cost by 20% in comparison with reference HFC system.

Efficient sustainable container reefer applications using CO₂
J Michael Griffin from Carrier presented results from extensive sea trials of refrigerated reefer containers for the transport of perishable and frozen cargo.
Based on new CO₂ technology with optimised efficiency for different modes of operation, the system consists of purpose built multi-stage compressor, gas cooler heat exchanger, two speed gas cooler fan, flash tank, variable speed drive and advance controls. The CO₂ transcritical system has been successfully tested during more than 23,000 operating hours, resulting in an average energy use equal to R134a.

Transport refrigeration system using CO₂
A new technology trend in the transport refrigeration sector brought to the ATMOsphere conference by Bart W. Ezendam from Thermo King is the open cycle CO₂ refrigeration. Liquid CO₂ obtained as a by-product from industrial production is stored in a tank mounted to a truck and when released cools air through an evaporator coil located in a refrigerated space.

CO₂ Compressors for mobile air conditioning and light commercial refrigeration
A presentation by Jan Hinrichs from Ixetic introducing a heat pump system using CO₂ for thermal management in battery electric vehicles and for passenger air-conditioning brought a lively discussion among participants in the market innovation session. The electric driven CO₂ compressor with a gas cooler in the heating/ cooling unit with a heating power of 3.2kW at -7°C ambient temperature had a COP of about 3.0. With the recent development in the mobile air conditioning (MAC) sector pointing to a renewed interest in natural refrigerants, it is likely that CO₂ MAC systems will be in the spotlight at next year’s ATMOsphere event.

Transcritical CO₂ cooling and freezing system for Norwegian ice cream manufacturer
Torben M. Hansen from Advansor introduced a case study with performance analysis of the 220kW (at -38°C) industrial transcritial CO₂ system with 150kW of heat recovery and hot gas defrost. According to the simulation of energy consumption, the R744 system with heat recovery achieves reductions of 1,000 tons of CO₂ equivalent per year (direct and indirect emissions) in comparison with a similar R404A system.

Refrigeration and heat recovery with CO₂ in food retail stores
Torben Funder-Kristensen from Danfoss showed the advantage of a R744 commercial system with heat recovery on a case study from Denmark. The CO₂ booster system of 160kW cooling capacity (5 MT and 4 LT compressors) with heat recovery has a 34% lower TEWI than a conventional R404A system with high direct emission. With a potential running cost reduction of 20%, CO₂ systems with heat recovery are suitable for supermarket applications.

Development of a high temperature CO₂ heat pump for space heating
Georges Khoury from Sanden Europe in his presentation introduced a high temperature CO₂ air/water heat pump with a new cascade and control. The newly developed R744 heat pump is targeting space heating applications. The heat pump supplies hot water of up to 80°C, the temperature required by heating systems in older buildings. The patented technology - the new cascade - is based on the upper stage recovery of the excess heat in the first stage through an intermediate heat exchanger. A maximum heating capacity of 8.6kW with a COP of 2.6 makes it an attractive alternative to fuel and gas boilers. According to laboratory tests, in combined mode (space heating & DHW), R744 would be more efficient than HFC.