By Barney Richardson
The future of refrigeration for food preservation in refrigerators and in supermarkets is dependent on how we adopt and adapt to new technologies for refrigerant use.
There is a present trend in South Africa to use Carbon Dioxide in supermarkets and larger refrigeration systems. However, many refrigerants still have a high global warming potential (GWP) and ODP (ozone depletion potential).
The HFC and HFO refrigerant blends have been used for a short time as an interim measure in air conditioning and refrigeration while the transition to natural refrigerants takes place. This is a return to the original refrigeration engineering of 150 years ago when natural chemicals like carbon dioxide, ammonia and sulphur dioxide were all that was available. Ammonia has always been with us and carbon dioxide has made a return. It was in the 1930s that CFC refrigerants like R12 were developed and the 1950s when R22 made its appearance. These two refrigerants served us well until the environmental consequences came to light. The ozone problem was discovered in 1970 which led to the Montreal Protocol on CFC and HCFC on ozone depletion. Later, in 1995 global warming reared its ugly head and the search for alternatives began.
GWP is a measure of how much heat of the gas is trapped in the atmosphere as a greenhouse gas over a period of time. ODP is a number which refers to the amount of ozone depletion caused by a substance such as refrigerant in the stratosphere.
The large cold storage and processing industry will always choose ammonia as the preferred refrigerant because it has a low boiling point at -33°C, has zero GWP and has a zero ODP and high latent heat of vaporisation. Ammonia systems circulate less F-gas refrigerant for the same cooling capacity. The price for ammonia is a big attraction, being nearly 10 times cheaper than most F-gases.
Daikin has looked at alternative refrigerants for its room air conditioning units and has introduced R32. This is said to be more environmentally friendly than R410A through leak emissions. Daikin says through its energy efficiency and environmental advantage, “R32 air conditioning provides the perfect opportunity to future-proof the air conditioning system”.
Natural hydrocarbon (HC) refrigerants, now in favour, are non-toxic refrigerants that have zero ODP and low GWP. Hydrocarbon refrigerants such as R290 (propane), R600a (isobutane) are now commonly used in domestic refrigerators, beverage coolers and small refrigeration systems. These two refrigerants, in particular, are climate-friendly and cost-effective refrigerants in small refrigeration applications.
It is feasible that we could see R290 being used in room air conditioners in the years to come. These air conditioners would not present any concerns due to flammability because we are seeing R600a in domestic refrigerators already. It does require a greater competence of the installation and maintenance practitioners working on hydrocarbon systems however. These practitioners must be trained in the safe handling procedures for hydrocarbon refrigerants, be registered with SAQCC Gas and be authorised to issue a Certificate of Conformity.
A CoC is a requirement of the Occupational Health and Safety Act and Pressure Equipment Regulations regulation 17.
Hydrocarbons, carbon dioxide and ammonia used in various applications are safe energy-efficient alternatives to what has been used previously for moderate to high ambient air temperature climates. The engineering technology of refrigeration systems has progressed in leaps and bounds for the efficient use of these refrigerants.
Selecting new refrigerants requires thorough investigation of the initial time and maintenance costs. If the engineering and selection is done within standards and good practice many new projects can be initiated with natural refrigerants. New safe handling of refrigerant protocols and procedures for refrigeration and air conditioning systems can contribute to greater use of low GWP refrigerants.
All refrigerants are safe if safe handling of refrigerant guidelines and safety standards are adhered to. The SABS SANS 10147 and Pressure Equipment Regulations and the SARACCA safe handling training manual ensure good practice and conformity to the legal requirements.
About the author
Barney Richardson is the director of South African Refrigeration and Air Conditioning Contractors Association (SARACCA) and sits on various other boards within the HVAC industry, including the South African Qualifications and Certifications Committee for Gas (SAQCC) Gas.
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