The scientific consensus around climate change is that greenhouse gases (GHGs) emitted by human activities are creating a very serious problem. As a result, most major global regions have adopted targets for reduction of GHG emissions, notably carbon dioxide (CO2). The largest source of CO2 emissions comes from the burning of fossil fuels for generating electricity, powering vehicles, and providing heat. Heating, ventilation, and air conditioning (HVAC) equipment plays a large role in CO2 emissions, as it accounts for roughly 40% of total building energy consumption.
Thus, increasing the efficiency of HVAC equipment is a clear way to address GHG emissions. But, it’s not the only way HVAC equipment can help. Indeed, in a recent report, the World Resources Institute points out that non-energy and non-CO2 emissions account for 22% of all U.S. GHG emissions and are expected to rise. The report goes on to recommend the reduction of hydroflourocarbons (HFCs), which are used as refrigerants in HVAC equipment. However, when it comes to HVAC, what HFCs should be replaced by is not entirely clear.
Within an HVAC system, refrigerant needs to be evaporated, condensed, and be compressed in such a way that the system can provide cool air. As a result, the band of temperature and pressure in which refrigerant changes phase between liquid and gas is narrow. Within a building, even the best HVAC systems may leak at some point in their lifetime. So, refrigerant needs to be non-toxic and non-flammable to keep building occupants safe. These requirements were met by chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). However, the proliferation of these refrigerants introduced a new problem: ozone depletion. While HFCs have solved the problem of ozone depletion, they are a GHG that traps heat in the atmosphere, contributing to climate change. The next generation of refrigerant needs to solve all of these problems.
So far, finding one refrigerant that is functional, safe, and doesn’t have severe impacts on the environment has been difficult. Potential candidates that have a lower the global warming potential than HFCs include R-32, which is mildly flammable, and CO2, which doesn’t fully change phase. Both have been commercialized. R-32 has been available in Japan since 2012. CO2 is being used as a standalone refrigerant in Europe and has recently been deployed in the United States. While challenges still remain, the development of these refrigerants presents the promise of reduced GHG emissions.
Tags: Building Innovations, Building Systems, Carbon Emissions, Climate Change, Greenhouse Gas
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