Environmental Impact of Refrigerants | Daikin Industries, Ltd.

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Properties of Future Candidate Refrigerants

Basic Refrigerant Properties

Features of Natural Refrigerants and other Candidate Refrigerants

Characteristics of Candidate Substances

New Candidate Refrigerants

Daikin's Position

Basic Refrigerant Properties

The main Properties required of refrigerants are stability, adequate pressure, and efficiency.

Stability

Air conditioners and refrigerators have an expected lifetime of 10 years or more, so the refrigerants used must work stably for at least 10 years. This means that refrigerants must be chemically stable. Refrigerants cannot be used if they undergo chemical reaction over the years and significantly change in performance.

Adequate Pressure

For air conditioners to give superior performance, their refrigerants must have adequate pressure.

If the vapor (condensation) pressure is too high, the amount of heat generated when the refrigerant liquefies is too little, so the COP*drops.

Likewise, if the vapor pressure is too low, a greater volume flow is needed. This means a bigger pressure loss due to flow speed, resulting in the need for larger pipes or a decrease in COP.

*COP is the energy consumption efficiency. COP = cooling (heating) capacity (kW) divided by rated power consumption,

Efficiency

Air conditioners don't just contribute to global warming directly due to refrigerant emissions; they also contribute indirectly by consuming energy to operate, as well as when they are manufactured and disposed of. Compared to the direct effects from the refrigerants of air conditioners and refrigerators, the indirect effects from their operation are usually much larger.

Assessment of global warming impacts using LCA

In order to truly reduce the total global warming impact of air conditioners, we have to look at all the ways they contribute to global warming.

It's not enough to simply create measures that deal with the global warming impacts of refrigerants alone or the impacts of consumed energy alone. Refrigerants must have high efficiency. It's possible, however, to make up for poor refrigerant efficiency by raising efficiency through larger components on the air conditioner. But making larger components will consume more energy during manufacture and disposal, thus offsetting any gains.

Features of Natural Refrigerants and other Candidate Refrigerants

The table below shows the characteristics of the main candidate refrigerants for air conditioning. You can see that using HFCs will help avoid ozone layer depletion.

HFCs, however, have a relatively high global warming potential (GWP), while natural refrigerants generally have a GWP close to zero.

Type and Characteristics of Future Refrigerants

Air conditioners contribute directly to global warming through the refrigerants they use. But they also contribute in indirect ways, such as through the energy they consume and in their manufacturing and final disposal stages. Usually, the indirect effect that air conditioners and refrigerators have on global warming due to their operation is greater than the direct effect that they have through their refrigerants.

Types and properties of future refrigerants.(table)

Characteristics of Candidate Substances

Ammonia
Ammonia does not contribute to global warming, and it is a superb refrigerant. Because it is toxic and slightly combustible, however, it must be carefully controlled. Since we believe ammonia is suitable for use in places like factories, where it can be strictly controlled, we use it in large-scale refrigeration equipment.
If we used ammonia for general air conditioning, we would have to invest a lot of money in safety equipment. As well, because copper material cannot be used, there will be less money available to spend on performance. As a result, we believe that indirect global warming impact will increase.

If we used ammonia for general air conditioning, we would have to invest a lot of money in safety equipment. As well, because copper material cannot be used, there will be less money available to spend on performance. As a result, we believe that indirect global warming impact will increase.

Propane
Propane has equivalent performance to R22, and isobutane, a substance similar to propane, is used as a refrigerant in refrigerators. Propane is highly combustible and thus susceptible to explosion in the event of leakage into the air. To use as an air conditioner refrigerant, the volume of propane must be dramatically reduced to ensure that it is safe. (Air conditioners use about 10 times as much refrigerant as refrigerators. Ten times the refrigerant volume increases the danger of explosion by 1,000 to 10,000 times.) As well, the pipe work for air conditioners must be done on-site. Current technology cannot guarantee the safety of propane air conditioners. This means there is still much work to be done before its practical application as a refrigerant.

Carbon dioxide (CO2)
CO2 has a lower toxicity rating and is not flammable. However, because it has a low COP, air conditioners using it require more electricity, thus, there are doubts whether it will lessen the total global warming impact. In addition, it has significantly higher operation pressure than conventional refrigerants. But because it has similar performance as conventional refrigerants for applications like water heaters, Daikin uses CO2 as a refrigerant for heat pump water heaters.

HFC32
A type of HFC, HFC32 has the potential to significantly reduce global warming: it has a global warming potential approximately one-third of HFC410A and HFC407C, and it is more efficient. It can also be adapted for use in air conditioners in a relatively short time. However, even though HFC32 is not classified as a flammable gas under Japanese general high-pressure gas safety laws, it is slightly combustible. That is why we are currently assessing its risks and developing technologies to ensure its safe use. International standards for the safe use of propane, HFC32, and other flammable refrigerants are currently under development.

New Candidate Refrigerants
There are a limited number of substances that can be used as refrigerants, and it is not easy to find substances that satisfy the conditions for efficiency and safety. We will, however, continue our search.

Daikin’s Position

Although a number of possible future refrigerants can help solve the problem of global warming, they still must be made energy efficient and safe in order to be viable air conditioner refrigerants.

The substitute refrigerants HFC410A and HFC407C have about the same global warming impact and energy efficiency as conventional HCFC22. Our current global warming prevention measures are therefore twofold: use these refrigerants in air conditioners in order to stop ozone layer depletion; and continue to develop energy-efficient products and to recover refrigerants from used air conditioners.

With the prevention of global warming becoming a worldwide concern, we are doing all we can to both raise energy efficiency and lessen environmental impact by searching for possible new refrigerants while at the same time studying the feasibility of natural refrigerants.

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