Heat pumps are modern devices that allow for efficient heating and cooling of buildings by using energy from the environment. They are promoted and are essentially already seen as an eco-friendly alternative to traditional heating systems. However, to fully assess their environmental impact, attention must be paid to the parameters related to the refrigerants used in them. Alongside the GWP coefficient, one of the key indicators is ODP.
ODP is an acronym from the English Ozone Depletion Potential, which translates to "ozone depletion potential". It is a numerical value that determines the extent to which a given gas contributes to the degradation of ozone in the atmosphere. This, of course, refers to the gas used in the heat pump as the working fluid, often colloquially called freon (though not always strictly accurately). Therefore, the ODP indicator actually refers more to the refrigerant used in the heat pump than to the pump itself.
The numerical scale of the ODP indicator - is established in relation to the refrigerant CFC-11, for which the ODP is 1. So, if another refrigerant has an ODP = 0.1, it means its impact on the ozone layer is ten times smaller than that of CFC-11. Or, more simply - from an ecological point of view - the lower the ODP, the better. Ideally, it should be 0 (which is possible).
Refrigerants used in heat pumps are responsible for transferring thermal energy within the system - without them, the operation of a heat pump is not possible. In the past, gases with high ODP were used, such as the old R12 or R22, which led to the destruction of the ozone layer. Even back in the days when heat pumps were in their infancy - in the 1970s and 1980s, it was discovered that the ozone layer in the Earth's atmosphere was depleting. At that time, these gases were not primarily used in heat pumps - as these devices were hardly present on the broad market. They appeared more often, for example, in refrigerators or air conditioning systems. In response to the rapid degradation of the ozone layer, Western countries, led by Canada - using UN structures - brought about the signing of the so-called Montreal Protocol in 1987, in which a number of countries decided to commit to phasing out the use of refrigerants with high ODP. In 1987 in Montreal, the protocol was signed by 47 countries - including the USA and the USSR - as well as many smaller countries, like the UK, France, West Germany or Poland. Later, other countries signed it; today it covers virtually the entire world (197 countries).
Thus - current regulations – including those introduced by the Montreal Protocol – prohibit the use of substances with significant ozone depletion potential, which is why modern heat pumps use refrigerants with an ODP equal to 0.
Most refrigerants currently used in heat pumps, such as R410A, R32, or R290 (propane), are characterized by zero ODP. This means that even in the case of a leak and the refrigerant escaping into the atmosphere, it will not directly cause destruction of the ozone layer. However, it is important to remember that these same refrigerants may have a high GWP index, impacting the greenhouse effect - because ODP is not the only factor determining whether a device is environmentally friendly.
The ODP (Ozone Depletion Potential) coefficient was introduced in the late 1970s, when scientists began to study the impact of freons and other halogenated substances on the ozone layer in more detail.
The concept of ODP was first described by Prof. Mario Molina and Prof. F. Sherwood Rowland in 1974 in their scientific paper, which demonstrated that CFCs (chlorofluorocarbons) could cause the breakdown of ozone in the stratosphere. The ODP indicator became widely used in the 1980s when international efforts to protect the ozone layer began, especially under the Montreal Protocol of 1987. Today, it is discussed a bit less than, for example, the GWP indicator (which determines a gas's impact on the greenhouse effect), but this might be related to the fact that after the signing of the Montreal Protocol, most countries effectively took action to limit and phase out gases with a high ODP coefficient (even if it took some time). Today, scientific reports are already noting the recovery of the ozone layer, and even that by the year 2100 it could reach a size comparable to its state in 1970, despite ongoing technological development.
ODP is an important parameter from an environmental protection perspective, defining the impact of a refrigerant on the ozone layer. In modern heat pumps, the ODP is typically 0, which is in line with international regulations and ecological goals. Nevertheless, when choosing a heat pump, it is worth analyzing not only the ODP but also the GWP, so that the device is both safe for the ozone layer and has a minimal impact on climate change.
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