11/07/2023
For years we've been told that heat pumps are the most energy efficient heat (and therefore eco friendly) sources, but are they environmentally friendlier? Seems not!
"The cold facts about refrigerants:
Why some heat pumps are better than others:
Greenhouse gases don’t all cause equal harm to the environment, and the refrigerants used in many of our heat pumps are much more harmful than carbon dioxide (CO₂). The global warming potential (GWP) of a gas indicates the contribution to global warming resulting from the emission of 1 unit of that gas compared to 1 unit of carbon dioxide, which has a value of 1.
For example, R410A (a refrigerant widely used in heat pumps in this country) has a GWP of 2088. If that escapes from a heat pump, it will contribute to much more damage (2088 times more) than an equal amount of carbon dioxide. In some research work, heat pumps are estimated to lose around 6% of their refrigerant per year, which works out to around half of their total refrigerant over a lifetime.
How is this relevant to the building industry? When it comes to specifying water heating heat pumps, a heat pump with CO₂ as a refrigerant is clearly better for the environment than a heat pump with another refrigerant with a higher GWP such as R410A.
Heat pumps with R410A are currently being phased out, being replaced with heat pumps using R32 refrigerant. R32 has a better GWP but is still 675 times more damaging than CO₂ so will only be a transition refrigerant until some time a better refrigerant is available.
There are a number of heat pump water heaters available on the New Zealand market that use CO₂ as a refrigerant.
One encouraging development is that newer heat pumps tend to use less refrigerant. Some newer heat pumps have an R32 refrigerant charge of around 0.6 kg compared to older heat pumps with a refrigerant charge typically around 1.5 kg.
Last year, New Zealand signed up to a global agreement to phase out the use of HFC gases such as R32."
