The ozone layer is a hot topic for New Zealanders and Australians as our proximity to a “hole” over Antarctica means we have relatively low ozone levels. Ozone absorbs ultraviolet radiation from the sun – our depleted levels coupled with the number of fair-skinned people in our population have lead to the highest death rate from skin cancer in the world, relatively speaking.
The release of CFCs has been controlled since the late 1980s by the Montreal Protocol on Substances that Deplete the Ozone Layer, which New Zealand adopted in 1998. The Environmental Protection Authority says it is illegal to release these gases into the atmosphere - while CFCs are being phased out under the Montreal Protocol, it is not yet illegal to use them.
Countdown’s GM corporate affairs and strategy Richard Manaton says the supermarket chain has been modifying its equipment for a number of years as part of its sustainability programme, but changing laws provided the final push.
“In terms of CFC based refrigeration, we are exiting this equipment as the refrigerant gases to support them can no longer be imported into New Zealand under international convention.”
Manaton says fewer than 10 percent of its stores use CFCs in their refrigeration systems, and they will be upgraded “in the coming years.” A Countdown spokesperson anticipated that the chain would be completely free from CFC systems within the next two to three years.
Manaton says every time equipment is replaced or installed, more energy-efficient systems with more environmentally-friendly refrigerant gases are used, saying this has helped keep its carbon footprint to within 4 percent of 2006 levels despite a 33 percent increase in selling space.
According to Consumer magazine, CFC gases are no longer common in consumer appliances. These usually contain a refrigerant called R131a, which contributes to the greenhouse effect but does not damage the ozone layer. Some manufacturers instead use R600a, a flammable hydrocarbon which is more environmentally sound.
When asked by The Register about CFC gases, Foodstuffs NZ sustainability manager Mike Sammons chose not to speak about CFCs and instead volunteered information on Foodstuffs’ use of a chemically similar but less damaging group of compounds, HFCF or hydrochlorofluorocarbons. HCFCs have replaced CFCs in many applications but are also being phased out.
Sammons says HCFC-based systems are the norm in New Zealand supermarkets. By the end of this year, 12 of Foodstuffs’ 178 Kiwi supermarkets will use new carbon dioxide (CO2) based transcritical systems but 93 percent of Foodstuffs stores use either hybrid systems or ones based on HCFC technology.
Cost was formerly a factor in supermarkets sticking with older, environmentally damaging technology like CFCs and HCFCs, but Sammons says it is now about implementation issues.
“From a whole of life perspective its not so much cost, rather it’s more about suitability in terms of scale and technical issues especially if it’s part of a refurbishment.”
Sammons says environmentally sound, CO2 based transcritical refrigeration technology has only become commercially proven in the last few years, and Foodstuffs supermarkets are the first in the Southern Hemisphere to begin implementing the change to transcitical refrigeration.
“[It’s] a massive step forward, [with] the ability to reduce carbon emissions by 99 percent compared to the HCFC system.”
As more and more CO2 based systems are installed and equipment supplier technology increases, Sammons says, the perception that CO2 is only viable for large stores decreases. CO2 is now being used in domestic HVAC and Heat-pump DHW applications so is becoming more viable for all store sizes.
We asked Sammons about the positives and negatives of CO2 technology:
- As more and more systems are installed, component suppliers are enabling economies of scale and introducing better components and controls, as well as maximising the energy potential of operating a CO2 system
- A transcritical system is 100 percent CO2, so only one gas is required on site and it operates on a direct expansion cycle for both LT and MT applications.
- Typically a CO2 system has some energy saving advantages in cooler climates, combined with excellent heat recovery properties. Total store energy savings can be obtained in winter months in HVAC and year round via water heating.
- Green image! It's non-toxic, natural and non-flammable so there are no adverse effects on the environment.
- Its future is secure and it won't be phased out as other refrigerants have been in the past. It is the environmental choice for many refrigeration system applications.
- High volumetric cooling capacity, so smaller piping, evaporators and compressors can be employed, however in summer months it operates at higher pressures.
- It's a high density gas so all heat exchangers become very efficient.
- In summer ambient conditions the efficiency gains are reduced and, in some instances negated, compared to traditional HFC systems.
- Special care in design needs to be made by experienced designers to avoid high energy costs, predominantly through smart control algorithms and additional control componentry. Transcritical CO2 is currently not recommended for warmer climates in the sub-tropical regions because of this.
- Requires specific training in the maintenance of systems. Incorrect service and maintenance can lead to loss of refrigerant and wasted energy. Only use CO2 trained service technicians.
- Operates at higher pressures so thicker wall piping and stronger components are required. This offsets the reduction in pipe and compressor size so capital cost can be greater.
- A subcritical system(Hybrid) still requires two gases on site with typically R134a (HFC) as the secondary gas which attracts a levy.