Why heat pumps are a cost-effective and climate-friendly solution to extreme heat waves and cold winters.
Summer is only weeks away in the Northern Hemisphere, but temperature records have already been broken as heatwaves scorch regions from Scandinavia to Japan to the United States. Heatwaves hit India and Pakistan early this year, with weeks of scorching temperatures during deadly heat waves in March and April.
As cooling becomes increasingly necessary for comfort and safety in buildings worldwide due to climate change, approximately 3.3 billion air conditioning units are expected to be installed in the next few decades. As our friends at Canary Media pointed out in a recent episode Carbon copy podcast, 18,000 central air conditioners are installed in US homes every week. But for the millions of homes and businesses that need cooling in the summer and heating in the winter, a heat pump can serve both needs very efficiently as a double-duty comfort machine.
These quiet and powerful all-electric devices have been in the news a lot recently, including when President Joe Biden invoked the Defense Production Act to bolster U.S. energy security, accelerate production of heat pumps and other clean energy technologies to combat climate change. works. In this article, we’ll explain some of the most common types of heat pumps, how the technology works, and how heat pumps can save people money on heating and cooling while reducing and leading the way in planet-warming greenhouse gas emissions. to healthier indoor and outdoor air quality.
Heat pumps: A two-way solution for year-round comfort
Heat pumps differ from traditional HVAC devices in at least two major ways. First, many heat pumps can work in both heating and cooling mode – filling the role of both an air conditioner and a furnace. Second, a heat pump operating in heating mode has one important, energy-saving advantage over a traditional gas or electric furnace: the heat pump simply moves more heat than generating through fossil fuel combustion or electrical resistance. This key differentiator allows heat pumps to achieve higher efficiency levels.
The basic principles of a heat pump are similar to those of a domestic refrigerator. Both technologies use a refrigerant to transfer heat from one side of the system to the other. When a standard residential heat pump operates in cooling mode (Figure 1), a low-pressure, low-temperature refrigerant absorbs heat from the indoor air, which is released when the refrigerant is compressed and passed through an external heat exchanger. (This transfer of heat releases some warm air into your kitchen as your refrigerator chills your food and drinks.)
In heating mode, the coolant flow is reversed. The refrigerant absorbs heat from the outside air and evaporates inside the sealed system. Importantly, the refrigerants used in heat pumps have very low boiling points and efficiently absorb heat even from cold winter weather. This heat can then be transferred to the indoor environment by compressing the steam and passing it through an internal coil, where it releases some of the heat.
Because a heat pump simply moves heat instead of creating heat, it can produce up to four times more heat energy (kWh) than it uses for electricity, resulting in lower energy use and running costs than electric resistance heaters. As shown below, heat pumps are also far superior to gas furnaces. Essentially, heat pumps help homeowners avoid burning gas indoors, eliminating any potential risks of carbon monoxide poisoning or dangerous gas leaks and explosions. Eliminating fossil fuel combustion also greatly benefits outdoor air quality and health. Fossil fuel air pollution is responsible for one in five deaths worldwide, according to a study by the Harvard TH Chan School of Public Health.
Types of heat pumps
Air source heat pumps (as shown in Figure 1) transfer heat from indoor air to outdoor air or vice versa. Ground source heat pumps (Figure 3) work in a similar way, the main difference being that the systems use the ground as an open medium for heat exchange, which is relatively stable in temperature, making them an excellent solution for very cold climates.
Heat pumps can be ducted (with heated or cooled air forced through a series of ducts to reach different areas of the building) or ductless, commonly known as a mini-split system. The mini-split has multiple internal compartments for precise heating and cooling of specific rooms or zones.
In addition to heat pumps for heating and cooling indoor air, there are other common household appliances such as high-efficiency water heaters and dryers that use heat pump technology. By harvesting thermal energy from the ambient air, such as in an insulated garage or utility room, high-performance heat pump water heaters in the US boast four times the efficiency of a conventional water heater.
Are heat pumps for everyone?
Heat pumps have long been popular in temperate climates, but are often dismissed as unsuitable for cold winters. However, technological advances in recent years have made cold climate heat pumps a practical solution even in sub-zero conditions. Heat pumps now play an important role in climate action plans everywhere from Colorado to Maine. A recent RMI analysis of Wisconsin’s climate and energy mix shows that heat pumps in this northern state can save households hundreds of dollars a year over electric or propane furnaces. And it’s not just the US: colder countries like Norway have some of the highest heat pump adoption rates in Europe.
Although heat pumps are more efficient to operate, their initial cost has been a persistent barrier to wider adoption. However, there are many scenarios where a heat pump can be competitive on purchase price. For example, new all-electric homes are generally less expensive to build than mixed-fuel (electric and gas) homes, since the infrastructure needed to bring gas to a new building can cost about $5,000 for a single-family home. Going all-electric also protects homeowners from volatile fossil fuel prices that can be affected by global disasters like Russia’s invasion of Ukraine.
Heat pumps are also a money-saving solution for homeowners looking to add or upgrade their air conditioning and heating systems. A study by the Wisconsin Public Service Commission found that the total cost of a furnace and air conditioner starts at $6,600, while a heat pump system costs $2,300 (ductless) or $4,200 (ducted). In regions like the Pacific Northwest, where air conditioning needs used to be rare, consumers can install a heat pump to cope with increasingly hot summers while replacing an old or inefficient furnace.
Electric utilities can contribute to the energy, cost and carbon savings of heat pumps for everyone by subsidizing or otherwise incentivizing the purchase and installation of heat pumps. Government leaders around the world must act quickly to protect people from intensifying heat waves and other weather events by developing policies and programs that ensure efficient, healthy and fully electric homes, especially for our most vulnerable citizens and communities. We also need to invest in building and training a clean energy workforce that can get the job done.
Switching to a heat pump today is a win-win for household energy savings, human health and comfort, and the climate, and these benefits will only increase as the electricity grid goes green and more people demand clean heating and cooling solutions.
© 2021 Rocky Mountain Institute. Published with permission. Originally published on RMI Outlet. By John Matson
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