Natural refrigerants are being used in a wider array of applications than ever before, according to the latest data from Cold Hard Facts 3 (CHF3).
It shows that Australia is on track to phaseout HCFCs by 2030 in accordance with the Montreal Protocol.
It also shows that the use of natural refrigerants in Australia is evolving with many factors shaping this emerging market.
Compiled by research firm, the Expert Group, and commissioned by the federal Department of Environment, CHF3, provides wide ranging insight into local natural refrigerant trends.
One segment of the market that is leading the charge in trialling new refrigeration systems is the retail sector, particularly supermarkets.
This is being achieved with the active adoption of ‘cascade’ refrigeration systems that employ a smaller charge of high GWP HFC in the primary cooling loop, and a charge of CO2 in a secondary refrigerant circuit (i.e. a large store with 1,000 kg refrigerant charge comprising 2/3 HFC-134a and 1/3 CO2).
Cascade systems are now regularly being specified for newly built large supermarkets.
The first HFC/CO2 cascade refrigeration system was installed in Australia in 2005 by Coles and other varieties were trialled including an ammonia/CO2 cascade system. There are now more than 800 of these advanced refrigeration systems in operation in Australian supermarkets, according to the CHF3 Report.
The technology formats and charge sizes in cascade systems vary significantly, however a new generation of CO2 trans-critical technology is rapidly evolving.
The CHF3 Report points to a mix of technology enhancement add-ons including booster systems, parallel compression groups, ejectors, adiabatic coolers, evaporative pre-cooling, indirect evaporative/dew point coolers and mechanical sub-cooling.
“Many of these innovations seek to manage the system gas cooler outlet temperature to offset the limitations of the low critical temperature of CO2.,” the report said.
“These systems are now well established in major supermarket groups and are starting to be employed by smaller independent supermarket operators.”
Leading supermarket contractor AJ Baker has installed CO2 trans-critical systems across 14 sites with seven in Perth, one in Brisbane, two in Sydney and 4 others as of March 2018.
“The key lessons have been that system gas cooler outlet temperature control is imperative for energy efficient operation in higher ambient temperatures zones, and that adiabatic coolers can deliver energy savings not previously possible in hotter months,” the report said.
“A combination of the focus on alternative refrigerants, dedicated efforts to reduce losses of refrigerant, the shift to cascade systems with much smaller HFC charges, and the adoption of some CO2-only trans-critical systems, have all contributed to reduce demand for bulk refrigerant in supermarkets.”
As a result of these trends, and particularly the surge in investment in cascade and CO2-only trans-critical systems, the CHF3 Report predicts that a significant portion of high GWP refrigerants will be removed from the supermarket sector by 2030, with around 35% of systems operating entirely or in part on CO2.
According to the CHF3 Report, the supply chain for CO2 is very complex with multiple steps, comprising many resellers, and suppliers sometimes going direct to end users, or with end users purchasing CO2 from further up the supply chain at the wholesale level as part of a project or new development.
Expert Group collects sales data from many of the supply chain participants and estimates the average sales volume over the last three years is approximately 120 tonnes per annum.
Although aggregate supplies of CO2 were estimated to be 120 tonnes in 2016 the installed base of equipment suggests that a portion of this gas is carried in the supply line, and on site as back-up supplies in manifolded cylinder pallets (i.e. Manpacks) to cover catastrophic failures (i.e. compressor failures or ruptures of gas lines).
While designs of CO2 systems are improving, owners and suppliers of CO2 refrigerant report the systems occasionally suffer gas line or seal failures and lose their entire charge, as CO2 systems have very high operating pressures.
These factors lead to the current estimate of a relatively small refrigerant bank of CO2 refrigerant of around 127 tonnes.
It should be noted that whilst a loss of charge is very inconvenient for the end user, the environmental impact is relatively insignificant as the refrigerant has a GWP of 1.
It is expected that with the now extensive base of installed CO2 refrigerant technology in enterprises with full-time engineering support, the technology and the expertise to design and operate them will continue to evolve rapidly and be employed in a wider range of applications in the cold food chain, including large food processors.
CO2 systems are also being used in truck and automotive air conditioning, small refrigerated vending machines and merchandisers, hot water heat pumps and for refrigerated containers known as reefers.
One such new small scale example of a CO2 application is the EcoCute technology, widely available in Europe and Japan, that uses CO2 refrigerant technology on hot water heat pumps to achieve high efficiencies and lower running costs.
In Europe and the US some end users and manufacturers of CO2 equipment are predicting CO2 will increasingly enter the industrial arena and are expecting ammonia systems to face increased competition from CO2 trans-critical systems in the industrial sphere, while foreseeing strong growth in ammonia heat pumps (i.e. low-charge packaged ammonia systems).
Recent innovations developed by equipment suppliers include demonstrations of micro-cascade air-cooled condensing units available in capacities from capacities as small as 2.5 kWr and upwards.
These units offer hybrid refrigeration (HFC-134a/CO2) systems for use in smaller sites and have potential for application across a broad range of commercial refrigeration applications.