The next abbreviation in HVAC we have to explain is GWP. A lot of people want to know what is GWP in HVAC. Specifically, GWP relates to refrigerants (also referred to as “freon”) used in air conditioners and heat pumps.
GWP stands for Global Warming Potential. It tells us how environmentally-friendly or environmentally-bad a specific refrigerant is. In recent news, we can find a lot of debate about methane global warming potential (from cows). This is because methane has a GWP of 27-30; that means it is 27-30 worse pound-per-pound than carbon dioxide (CO2) as a greenhouse gas.
Example of a standard refrigerant (for comparison): R-22 refrigerant has a 1,810 net GWP per 100 years.
What does that mean?
Here is a GWP definition according to Wikipedia: “GWP is a measure of how much infrared thermal radiation a greenhouse gas added to the atmosphere would absorb over a given time frame, as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide (CO2).”
We are going to explain what all this means in plain English and why GWP matters. Even if you don’t subscribe to the use of greener refigerant alternatives, the government does prefer lower GWP refrigerants, and introduces directives and laws that will impact the refrigerants we all use in the future.
Just want to mention this to avoid confusion: There are two metrics that determine how “green” refrigerants are.
- GWP or Global Warming Potential. This has to do with refrigerants creating a greenhouse effect. We will discuss this one here.
- ODP or Ozone Depletion Potential. This has to do with refrigerants creating a hole in the ozone layer.
Example: According to the EPA, “the production (not use) of R-22 was being phased out (in 2020)” due to high ODP (not high GWP). The most common alternative cited by the EPA is the R-410A which has a GWP of 2,088; this is more than R-22’s 1,810 GWP.
Let’s break this GWP definition down:
What Is Global Warming Potential (GWP)?
Refrigerants are quite ingenious gas – liquid substances. All air conditioners, heat pumps, and fridges use refrigerants. Without a refrigerant, in fact, it would not be possible to engineer the AC we know today (refrigeration cycle based cooling and heating).
One of the biggest disadvantages refrigerants like R-22 have is that they are bad for the environment. How bad? This is exactly what GWP tells us. GWP was introduced in IPCC-AR1 (Shine et al., 1990) document to quantify how bad a specific refrigerant is.
In accordance with the Kyoto Protocol from 1997, the premise for this new GWP metric was to compare how worse than carbon dioxide or CO2 (widely known greenhouse gas) freon is. We refer to this as “carbon dioxide equivalent”.
Here is how GWP is set up:
- CO2 is a reference greenhouse gas. It has a GWP of 1.
- A refrigerant that would produce a 10 times worse effect on the environment has a GWP of 10.
- A refrigerant that would produce a 1,000 times worse effect on the environment has a GWP of 1,000.
Now, what exactly means that R-22 freon has a 1,810 times worse effect on the environment?
In the context of GWP, that means that it will absorb 1,810 more infrared thermal radiation (this is one of the main Sun radiations that produces the greenhouse effect) in 100 years. Namely, 1 lb of R-22 (if released into the environment) will have the same environmentally negative effect as 1,810 lbs of CO2.
Every pound of R-22 refrigerant can absorb 1,810 times more heat (that impacts the greenhouse effect) than every pound of CO2. We know that CO2 built-up is bad for global warming, right? Well, R-22 is 1,810 worse; this is what 1,810 GWP tells us.
The main reason why refrigerants have such a high GWP is the presence of fluorine in their molecular structure.
Refrigerants can have anywhere from 0 to over 10,000 GWP. Let’s look at the GWP of the most commonly used refrigerants in the US:
GWP Of Commonly Used Refrigerants
Here is a short list of what GWPs commonly used refrigerants have:
|Refrigerant (or Freon):||GWP (Global Warming Potential):|
|R-50 (Methane)||27 – 30 GWP|
|R-744 (Carbon Dioxide)||1 GWP|
From this, we can see that most refrigerants we currently use have about 2,000 GWP. You can find a full refrigerant GWP chart with 61 freons here.
Going forward, we are probably going to see more low-GWP refrigerants.
A good example is using natural refrigerants like propane (R-290). Propane has a 3.3 to 9.5 GWP, which is great, but it comes with a very negative property: propane is flammable and has a limited scope of use.
Hopefully, this illustrates well what GWP means in HVAC. It’s basically a measure of how worse greenhouse gas a refrigerants is as the most prevalent greenhouse gas (carbon dioxide). If you have any questions, you can welcome to use our comment section below, and we’ll help you out.