The HVAC industry, throughout its history, has always been searching for better refrigerants, and a need to balance their efficiency with their environmental impact as well as making them optimal to replace those in use. This has led to the constant evolution of new refrigerants and the phasing out of those that were fire hazards or could cause the depletion of ozone.
Early refrigerants that were in use, when refrigeration first made its presence felt were sulfur dioxide, methyl chloride, and ammonia which met the objective of effective cooling. These refrigerants were also known for their high toxicity or were refrigerants that had a high flammability potential. In the 1930s, CFCs or chlorofluorocarbons were introduced and were thought to be a safe and more efficient refrigerant than the chemicals that were used before. They dominated the HVAC industry, because they were not only safe to use, but were highly efficient. In the 1950s, HFCs or Hydrochlorofluorocarbons were added to the alternatives available as refrigerants.
In the 1970s scientists came to the conclusion that both CFCs and HFCs were major contributors to the depletion of the ozone zone, that prevents the earth from large-scale damage due to ultraviolet rays of the sun. CFCs bore the larger responsibility while HFCs were considered only slightly less guilty of this damage to the environment. There was a worldwide concern that these refrigerants needed to be replaced, and the Montreal Protocol that suggested phaseout dates of 1996 for CFCs, while HFCs which had a lower ozone depletion potential or ODP was scheduled to be replaced between 2004 and 2030. Developing countries were allowed a further six years for the phasing out of HFCs. This protocol went into effect in 1987. In the 1990s, it was found that even refrigerants that had a favorable ODP were still contributing to global warming and had a high global warming potential or GWP. The KYOTO protocol in 1997 set additional targets for the reduction of greenhouse gases or those with a high GWP.
In both protocols, which have been signed by most of the countries, every country was expected to make its own program for reduction of harmful refrigerants that sets dates for stopping production of these refrigerants. The stoppage of production did not mean that these refrigerants could not be used, but all equipment using these now phased out refrigerants had to rely on stockpiled supplies and then will need to replace the refrigerant or equipment to use refrigerants that addressed environmental concerns. The next family of refrigerants in the continued evolution of these cooling aids were the hydrofluoroolefins or HFOs and had a low impact on the ozone layer or addition to greenhouse gases. These refrigerants have not yet been completely evaluated and various alternatives are being constantly developed and looked at.
The environmental impact of refrigerants depends on their ODP, GWP and the leak rates of these gases from the HVAC equipment. Older chiller designs in HVAC equipment did not place much importance to leakage rates, but as the awareness became more impactful, engineers looked at reducing leakage rates, and this has led to chillers that have reduced such leakage and hence reduced damage to the ozone layer and the environment by a factor of 10. In fact, it is estimated that refrigerants now cause only 5 percent of the impact on the environment, while the use of power by HVAC equipment causes the other 95%. This environmental impact caused by the use of HVAC equipment comes from the fossil fuels used by the power generating stations that produce the power used by the equipment. Another factor that can reduce leakages and hence environmental impact is operating pressures, and equipment manufacturers attempting to evolve technologies that minimize the amount of refrigerant use, and hence also reduce the leakage that is of major concern. Low-pressure technologies coupled with a reduced charge of refrigerants can greatly reduce emissions during the lifetime of equipment and thus mitigate environmental concerns.
Governments and authorities all over the world are aggressively regulating refrigerants, and this has led to equipment manufacturers constantly evaluating the design of compressors and their use of alternative refrigerants that have low ODP and GWP values. Every refrigerant has different physical properties and this leads to different requirements for their compression and to concerns for their safe and reliable use. The industry is constantly being asked to move to the use of low GWP refrigerants. One of the natural refrigerants that are gaining in popularity is R-290, tough it has safety concerns, because of its flammability. R-290 is high purity propane that has a chemical formula of C3H8. It is a refrigerant that has a low environmental impact but makes for very good thermodynamic performance.
Different types of refrigeration and HVAC equipment have their efficiencies linked to the type of refrigerants that they use, and the equipment manufacturers look to use a gas that has a low GWP and ODP, while it gives the best thermodynamic performance. R-32, an HFC, is another next-generation refrigerant that carries heat efficiently and has a lower impact on the environment. Its physical properties also allow it to reduce the use of electricity for its compression, and this further adds to its reduction of impact on the environment. It is an HFC gas that has a zero ODP and a GWP of 675. which is far lower than other gases like R12, a CFC, R22, and R410A, both HFCs, which are other gases that are still in use. The most commonly used refrigerant in today’s world is R410A, and companies are trying to move to R-32. This has the potential to reduce the CO2 equivalent of 800 million tons.
While the impact that refrigerants have on the environment has always been highlighted, it is rapidly being realized that reducing the requirement of power for the use of HVAC equipment may lead to greater advantages and the reduction of greenhouse gases. Manufacturers such as www.bluonenergy.com are now offering energy-saving technologies like the use of inverters that eliminate wasted operation of chilling equipment by controlling the speed of motors.