Why heat pumps are a cost-effective and climate-friendly solution for extreme heat waves and cold winters.
Summer in the Northern Hemisphere is only a few weeks old, but temperature records have already toppled as heatwaves bake the regions from Scandinavia to Japan until the United States. The heat hit India and Pakistan early this year, with weeks of scorching temperatures during deadly heat waves in March and April.
As climate change makes cooling a necessity for comfort and safety in buildings around the world, it is estimated that 3.3 billion air conditioning units are expected to be installed in the coming decades. As our friends at Canary Media noted in a recent episode of the cc’tje podcast, 18,000 central air conditioning units have been installed in American homes every week. But for millions of homes and businesses that need cooling in the summer and heating in the winter, a heat pump can provide both super-efficient and double-acting comfort machines.
These quiet and powerful all-electric devices have been in the news a lot lately, including when President Joe Biden invoked the Defense Production Act to accelerate U.S. production of heat pumps and other clean energy technologies to enhance energy security, combat climate change and create jobs. In this article, we’ll break down 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 greenhouse gas emissions that warm the planet and leading the way for healthier air quality. inside and outside.
Heat pumps: a two-way solution for year-round comfort
Heat pumps differ from traditional HVAC appliances in at least two important ways. First, many heat pumps can operate in both heating and cooling modes, fulfilling the role of both air conditioner and furnace. And second, a heat pump running in heating mode has one crucial, energy-saving advantage over a traditional gas or electric oven: the heat pump. moves heat instead of creating it by burning fossil fuels or electrical resistance. This important differentiator enables heat pumps to achieve much higher efficiency levels.
Figure 1: A heat pump in cooling mode. Source: EPA
The basic principles of a heat pump are similar to those of a household refrigerator. Both technologies use a refrigerant to move heat from one side of the system to the other. When a standard residential heat pump runs in cooling mode (Figure 1), a low-pressure, low-temperature refrigerant absorbs heat from the indoor air, which is released to the outside when the refrigerant is compressed and passed through an outdoor heat exchanger. (This heat transfer is why your refrigerator releases some warm air into your kitchen as it cools your food and drinks.)
In heating mode, the refrigerant flow reverses. The refrigerant absorbs heat from outside and evaporates in the sealed system. Crucially, the refrigerants used in heat pumps have a very low boiling point and can efficiently absorb heat, even from cold winter air. That heat can then be moved to the interior environment by compressing the vapor and passing it through an internal coil, where it releases some of its heat.
Because a heat pump only displaces heat rather than generates heat, it can produce more than four times as much heat energy (in kWh) as it consumes in electricity, resulting in lower energy consumption and lower operating costs than electric resistance heaters. As shown below, heat pumps also significantly outperform gas stoves. Importantly, heat pumps help home and building owners avoid burning gas indoors, eliminating any risks of carbon monoxide poisoning or dangerous gas leaks and explosions. And eliminating the burning of fossil fuels also has huge benefits for outdoor air quality and health. According to a study by the Harvard TH Chan School of Public Health, air pollution from fossil fuels is responsible for: one in five deaths worldwide.
Figure 2: Heat pump efficiency versus gas furnace efficiency. Source: RMI
Types of heat pumps
Air-to-water heat pumps (as shown in Figure 1) transfer heat from the indoor air to the outdoor air, or vice versa. geothermal heat pumps (Figure 3) works the same way, with the main difference that the systems use the ground, which is relatively stable in temperature, as the outdoor medium for heat exchange – making them a great solution for very cold climates.
Figure 3: A horizontal ground source heat pump. Source: heat pump planner by NYSERDA, Building Energy Exchange and Steven Winters Associates
heat pumps can be ducted (with heated or cooled air forced through a series of ducts to reach different parts of the building) or ductless, commonly known as a mini split system. A mini split has multiple indoor units for accurate heating and cooling of specific rooms or zones.
In addition to heat pumps for heating and cooling the indoor air, there are also other common household appliances such as high-efficiency boilers and dryers that use heat pump technology. By extracting heat energy from the ambient air, such as in an insulated garage or utility room, it delivers peak performance heat pump boilers in the United States boast of efficiency four times as much as a conventional boiler.
Are heat pumps for everyone?
Heat pumps have long been popular in mild climates, but are often dismissed as ill-suited for cold winters. However, due to technological advances in recent years, heat pumps in cold climates have become a practical solution, even at sub-zero temperatures. Heat pumps now play a prominent 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 that northern state can save households hundreds of dollars a year over electric or propane furnaces. And it’s not just the United States: cold countries like Norway have some of the highest heat pump adoption rates in Europe.
Despite the fact that heat pumps are more efficient to operate, the initial cost has been a persistent barrier to wider application. However, there are many scenarios in which a heat pump can compete on purchase price. For example, building new houses completely electrically is generally cheaper than building mixed fuel (electricity plus gas) homes, because 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, which can be impacted by global catastrophes like the Russian invasion of Ukraine.
Heat pumps are also a money-saving solution for homeowners who want to add or upgrade air conditioning and heating systems at the same time. A study by the Wisconsin Public Service Commission discovered that the combined cost of an oven and air conditioner starts at $6,600, while a heat pump system costs just $2,300 (without pipe) or $4,200 (with piped). In regions such as the Pacific Northwest, where the need for air conditioning was previously rare, consumers can install a heat pump to cope with the increasingly hot summers while replacing an aging or inefficient oven.
Electric utilities can help unlock the energy, cost and carbon savings of heat pumps for everyone by subsidizing or otherwise incentivising their purchase and installation. Government leaders around the world must act quickly to protect people from increasing heat waves and other extreme 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 is a victory today for household energy savings, human health and comfort, and the climateand those benefits will only increase as the grid becomes greener and more populations require clean heating and cooling solutions.
© Rocky Mountain Institute 2021. Published with permission. Originally posted on RMI output. By John Matson
Do you appreciate CleanTechnica’s originality and cleantech news coverage? Consider becoming one CleanTechnica member, supporter, technician or ambassador — or a patron on Patreon.
