HVAC equipment using refrigerants can include packaged rooftop units, direct expansion split systems, chillers, variable refrigerant flow (VRF) systems and several others. Different equipment systems can contain different refrigerant types with varying emissions potential.
Refrigerants are classified by global warming potential (GWP), which refers to the emissions contribution of a substance relative to that of carbon dioxide. Carbon dioxide has a GWP of 1, while R22 refrigerant has a GWP of 1810, meaning that one molecule of R22 has a global warming impact 1,810 times that of one molecule of carbon dioxide. The higher the GWP, the greater greenhouse gas impact associated with the refrigerant per ton. The federal government has regulated high-GWP refrigerants and is responsible for phasing out the use of R22 in new equipment.
GWP can be used to quickly measure and analyze the greenhouse gas emissions of refrigerants. Refrigerant emissions are classified as a Scope 1 emission (i.e., an emission that originates from the building site). Selecting and implementing equipment that uses low-GWP refrigerants is one of the simplest ways to reduce Scope 1 emissions.
Refrigerant emissions come from three main sources: installation, operation and disposal. Installation refers to either the primary refrigerant charge of the system, whether the system is charged at the factory or field installed (variable refrigerant flow, split DX systems, etc.) and charged on-site. This process is not perfect, and refrigerant leakage can occur. Proper manufacturer installation guidelines should be followed to minimize or eliminate leaks.
Operational emissions can occur due to refrigerant leaks over the lifetime of the system. These leaks are much likelier in a field-installed system when compared to a factory-charged system. The larger and more complex the field-installed system, the more likely leaks are to occur.
Disposal emissions occur during the decommissioning of a system. The Environmental Protection Agency (EPA) and manufacturers have strict guidelines to reduce disposal emissions; however, leaks and improper decommissioning results in substantial leakage.
How to measure and report:
The EPA has published several methods for determining greenhouse gas emissions from refrigerants1. They categorize refrigerant emissions as coming from installation, operation and disposal. If equipment is pre-charged from a vendor, the emissions data may be provided by the vendor.
Figure 1 estimates emissions from installation, with "k" typically estimated to be 10% losses. If a piece of equipment is charged at the factory, those emissions would not be included in the Scope 1 calculations.
Figure 2 estimates emissions from operation. Annual leak rate is determined by the piece of equipment and associated piping. Historical data from the facility can be used to estimate the leakage rate. Annual leakage for field-installed systems will be much higher than factory-charged equipment. Data should be collected during yearly maintenance from the facility contractor. Additionally, ANSI/ASHRAE Standard 228, Standard Method of Evaluating Zero Net Energy and Zero Net Carbon Building performance, provides typical annual refrigerant leakage rates by equipment type. This is a good starting point for estimating annual leakage rates for new equipment without historical data.
Figure 3 estimates emissions from the disposal of the equipment. It is important to note that disposal emissions should only be included if the equipment is disposed of during the reporting period.
For each refrigerant, the emissions can be multiplied by the refrigerant’s GWP to determine the carbon dioxide equivalent (CO2e) for all refrigerant usage. This last step illustrates the importance of using low-GWP equipment.
How to manage:
Management and reduction of refrigerant-based emissions hinges upon reducing refrigerant leaks over the life cycle of the system, as well as selecting equipment that utilizes low-GWP refrigerants that will reduce the impact of the refrigerant if the system does leak.
The best way to manage and reduce greenhouse gas emissions from refrigerants is by selecting low-GWP refrigerants. Phasing out high-GWP refrigerants, like R22, should be the first step for any health care organization. Some refrigeration equipment can accept a “drop-in” refrigerant that typically has a lower GWP. This typically reduces the refrigerant capacity of the equipment.
Selecting systems that utilize low-GWP refrigerants and minimize overall refrigerant charges are important to overall greenhouse gas emissions reduction. Developing an organization wide plan to mitigate existing leaks and prevent future leaks is critical to reducing emissions as well as maintaining high indoor air quality within buildings.
To summarize, the following steps should be followed to reduce greenhouse emissions from refrigerants:
- Select low-, ultra-low- and zero-GWP refrigerants.
- Minimize refrigerant charge in systems.
- Incorporate language in construction requirements that support leak-free installation by manufacturers and contractors.
- Identify leakage “hot spots” in refrigeration systems and take action to mitigate known issues.
- Create a refrigerant measurement and verification plan for leak testing to help identify leaks quickly and manage overall system operations.
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