From ammonia to air, the rac industry has refrigerant options aplenty to present to end users
RAC’s Alternative Cooling Conference prompted much speculation on the future of HFCs as viable refrigerants; however, industry presented a host of alternatives.
Rob Lamb of Star Refrigeration presented ammonia (R717) as an alternative refrigerant and in doing so he added a new point to the debate over refrigerant leakage.
“The fact that ammonia is toxic and flammable means the systems are designed not to leak, so the engineering has to be of the highest standard,” he said.
Other common sense ways of ensuring the safety of ammonia systems, he suggested, were: using an indirect system, with water as a secondary refrigerant, to keep the ammonia charge as small as possible and out of occupied areas; plate heat exchangers, to reduce the likelihood of leaks into the water system; using a plant room to contain any risk; and constant monitoring by detectors.
Mr Lamb noted that the development of sealed plug and play elements was prompting increasing interest amongst customers who previously had concerns about the safety issues.
“There are plenty of splits and chillers of all sizes,” said Nicholas Cox of Earthcare Products, “already using hydrocarbons.” These also include ground source heat pump units. However, according to his reading of the safety regulations, no units containing hydrocarbons can be mounted below 1.5m, which means only cassettes, ceiling, highwall and ducted indoor units can be installed.
As well as pure hydrocarbons, such as Propane R290, his company has produced a number of blends as replacements for traditional refrigerants, including ECP410A as a replacement for R410A.
According to Mr Cox, the required charge of hydrocarbon is only 40 per cent of the mass of HFCs, so smaller, lighter units can be manufactured.
“It is important to acknowledge flammability and deal with that,” he said, “but we have had clear safety standards since 1995.”
Bernd Heinbokel of Carrier Commercial Refrigeration, one of the pioneers of retail CO2 systems, examined how many European supermarkets are seeing the gas as the main alternative to synthetic refrigerants.
The main reason for this is, said Mr Heinbokel, that it has a number of advantages over its rivals, particularly the fact that it is now well known and already proven.
On the safety front it is a natural substance, has no ozone depletion potential, is non-flammable, non-toxic and is not subject to the F-Gas Regulation. On the financial front it is not subject to GWP taxes. On the performance front it has low sensitivity to pressure losses, excellent heat transfer properties, high volumetric efficiency, has no filling charge limitation and is not in danger of being phased out.
It is also, said Mr Heinbokel, attractive to supermarkets because of its heat recovery properties.
“We can reclaim 90 per cent of waste heat for use in a supermarket’s central heating system,” he said.
The ultimate environmentally friendly refrigerant, air, was looked at by Bristol University’s Judith Evans.
Air cycle technology is based on systems that have been used in aircraft for years, using the expansion and compression of air to provide heating and cooling.
Its greatest advantage is that air is free, completely safe and environmentally benign, Ms Evans said: “It ticks a lot of boxes on what you want air conditioning to be.”
It is also, she said, extremely reliable, reducing maintenance costs and system down-time, and performance does not deteriorate as much as that of a vapour compression unit outside its design conditions.
It can also produce heat to provide steam or hot water, provide low temperature cooling and even outperform liquid nitrogen systems for fast freezing, said Ms Evans.
“As far as supermarket refrigeration is concerned, it is easy to maintain, has no leakage problem and can cool and heat from the same equipment. We are currently looking at using it to both cool and freeze food.
“What we need now, to compete with other systems on efficiency, is specially made, highly efficient components, which are beginning to become available” she said.
If these become available she believes the system can provide retailers with an extremely flexible refrigeration system, with individual cabinets plugged into a central system.
But a commercial unit, she said, was five to ten years away.