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Summer is just a few weeks into the northern hemisphere, but temperature records have already been shattered as heatwaves sweep across Scandinavia, Japan and the US.The heat in India and Pakistan came early this year, lasting weeks of heat during deadly heatwaves in March and April.
Due to climate change, cooling is increasingly a necessity for the comfort and safety of buildings around the world, with 3.3 billion air conditioners projected to be installed in the next few decades.As our friends at Canary Media pointed out in a recent episode of the Carbon Copy podcast, 18,000 central air conditioners are installed in American 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 super-efficiently serve both needs as a double comfort machine.
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 speed up U.S. manufacturing of heat pumps and other clean energy technologies to enhance energy security, fight 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 bills, while reducing planet-warming greenhouse gas emissions and leading the way for healthier indoor and outdoor air quality.
Heat pumps differ from traditional HVAC equipment in at least two ways.First, many heat pumps can operate in both heating and cooling modes—both acting as air conditioners and stoves.Second, heat pumps operating in heating mode have an important energy-saving advantage over conventional gas or electric furnaces: heat pumps simply move heat, rather than generating it through fossil fuel combustion or electrical resistance.This key differentiator enables heat pumps to reach higher levels of efficiency.
The basic principle of a heat pump is similar to that of a domestic refrigerator.Both technologies use refrigerants to transfer heat from one side of the system to the other.When a standard residential heat pump operates in cooling mode (Exhibit 1), low-pressure, low-temperature refrigerant absorbs heat from the indoor air and is released outdoors as the refrigerant is compressed and passed through an outdoor heat exchanger.(This heat transfer is why the refrigerator releases some warm air into the kitchen as it cools food and drinks.)
In heating mode, the flow of refrigerant is reversed.The refrigerant absorbs heat from outside and evaporates inside the sealed system.Crucially, the refrigerants used in heat pumps have a very low boiling point and can effectively absorb heat even from cold winter air.The heat can then be transferred to the indoor environment by compressing the vapor and passing it through an internal coil, where it releases some of the heat.
Because a heat pump just moves heat rather than producing it, it produces more than four times the thermal energy (measured in kilowatt-hours) as it consumes the electricity, resulting in lower energy usage and operating costs than electrical resistance heaters.As you can see in the graph below, heat pumps also perform significantly better than gas furnaces.Importantly, heat pumps help home and building owners avoid burning gases indoors, eliminating any potential risk of carbon monoxide poisoning or dangerous gas leaks and explosions.Eliminating fossil fuel combustion also has great benefits for outdoor air quality and health.Fossil fuel air pollution is responsible for one in five deaths globally, according to a study by Harvard’s TH Chan School of Public Health.
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Air source heat pumps (shown in Figure 1) transfer heat from indoor air to outdoor air and vice versa.Ground source heat pumps (Figure 3) operate in a similar manner, with the main difference being that the systems use a relatively stable temperature ground surface as the outdoor heat exchange medium – making them an excellent solution for very cold climates.
Exhibit 3: Horizontal Ground Source Heat Pump Sources: NYSERDA, Building Energy Exchange, and Steven Winters Associates’ Heat Pump Planner
Heat pumps can be ducted (heated or cooled air is forced through a series of pipes to different areas of the building) or ductless, often referred to as small split systems.Mini-splits feature multiple indoor units to precisely heat and cool specific rooms or areas.
In addition to heat pumps used to heat and cool indoor air, other common household appliances, such as high-efficiency water heaters and dryers, can also use heat pump technology.By harvesting thermal energy from ambient air, such as in an insulated garage or utility room, America’s best-performing heat pump water heaters are four times more efficient than conventional water heaters.
Heat pumps have long been popular in mild climates, but are often considered unsuitable for cold winters.However, technological advancements in recent years have made cold-climate heat pumps a practical solution, even in sub-zero conditions.Heat pumps now feature prominently in climate action plans from Colorado to Maine.A recent RMI analysis of Wisconsin’s climate and energy mix shows that heat pumps in the north of the state can save homes hundreds of dollars a year compared to electric or propane furnaces.It’s not just the US: Cold countries like Norway have the highest heat pump adoption rates in Europe.
Although heat pumps operate more efficiently, their upfront cost has been a barrier to wider adoption.However, in many cases heat pumps can compete on purchase price.For example, building an all-electric new home is often cheaper than building a hybrid (electric plus natural gas) home because the infrastructure required to bring natural gas into a new building can cost around $5,000 for a single-family home.Going all-electric would also insulate homeowners from volatility in fossil fuel prices that could be affected by global disasters such as Russia’s invasion of Ukraine.
Heat pumps are also a money-saving solution for homeowners looking to add or upgrade both air conditioning and heating systems.A Wisconsin Public Service Commission study found that the total cost of a furnace and air conditioner starts at $6,600, while a heat pump system can cost as little as $2,300 (without ducts) or $4,200 (with ducts).In areas such as the Pacific Northwest, where air conditioning was rarely needed before, consumers can install heat pumps to cope with increasingly hot summers while replacing aging or inefficient furnaces.
Electric utilities can help everyone unlock the energy, cost, and carbon savings of heat pumps by subsidizing or otherwise incentivizing their purchases and installations.Government leaders around the world should act swiftly to protect people from growing heatwaves and other extreme weather events by advancing policies and programs that ensure efficient, healthy and fully powered homes – especially for our most vulnerable citizens and communities. influences.We must also invest in building and training a clean energy workforce that can get the job done.
Switching to a heat pump today is a win for home energy savings, human health and comfort, and the climate, and these benefits will only increase as the grid becomes greener and a growing population demands clean heating and cooling solutions .
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