How heat pumps of the 1800s are becoming ...
How heat pumps of the s are becoming ...
It was an engineering problem that had bugged Zhibin Yu for years &#; but now he had the perfect chance to fix it. Stuck at home during the first UK lockdown of the Covid-19 pandemic, the thermal engineer suddenly had all the time he needed to refine the efficiency of heat pumps: electrical devices that, as their name implies, move heat from the outdoors into people&#;s homes.
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The pumps are much more efficient than gas heaters, but standard models that absorb heat from the air are prone to icing up, which greatly reduces their effectiveness.
Yu, who works at the University of Glasgow, UK, pondered the problem for weeks. He read paper after paper. And then he had an idea. Most heat pumps waste some of the heat that they generate &#; and if he could capture that waste heat and divert it, he realized, that could solve the defrosting issue and boost the pumps&#; overall performance. &#;I suddenly found a solution to recover the heat,&#; he recalls. &#;That was really an amazing moment.&#;
Yu&#;s idea is one of several recent innovations that aim to make 200-year-old heat pump technology even more efficient than it already is, potentially opening the door for much greater adoption of heat pumps worldwide. To date, only about 10% of space heating requirements around the world are met by heat pumps, according to the International Energy Agency, or IEA. But due to the current energy crisis and growing pressure to reduce fossil fuel consumption in order to combat climate change, these devices are arguably more crucial than ever.
Since his lockdown brainstorming, Yu and his colleagues have built a working prototype of a heat pump that stores leftover heat in a small water tank. In a paper published in the summer of , they describe how their design helps the heat pump to use less energy. Plus, by separately rerouting some of this residual warmth to part of the heat pump exposed to cold air, the device can defrost itself when required, without having to pause heat supply to the house.
The idea relies on the very principle by which heat pumps operate: If you can seize heat, you can use it. What makes heat pumps special is the fact that instead of just generating heat, they also capture heat from the environment and move it into your house &#; eventually transferring that heat to radiators or forced-air heating systems, for instance. This is possible thanks to the refrigerant that flows around inside a heat pump. When the refrigerant encounters heat &#; even a tiny amount in the air on a cold day &#; it absorbs that modicum of warmth.
A compressor then forces the refrigerant to a higher pressure, which raises its temperature to the point where it can heat your house. It works because an increase of pressure pushes the refrigerant molecules closer together, increasing their motion. The refrigerant later expands again, cooling as it does so, and the cycle repeats. The entire cycle can run in reverse, too, allowing heat pumps to provide cooling when it&#;s hot in summer.
The magic of a heat pump is that it can move multiple kilowatt-hours of heat for each kWh of electricity it uses. Heat pump efficiencies are generally measured in terms of their coefficient of performance, or COP. A COP of 3, for example, means 1 kWh of juice yields 3 kWh of warmth &#; that&#;s effectively 300% efficiency. The COP you get from your device can vary depending on the weather and other factors.
It&#;s a powerful concept, but also an old one. The British mathematician, physicist and engineer Lord Kelvin proposed using heat pump systems for space heating way back in . The first heat pump was designed and built a few years later and used industrially to heat brine in order to extract salt from the fluid. In the s, members of the British Parliament discussed heat pumps when coal stocks were running low. And in the years following the -74 oil crisis, heat pumps were touted as an alternative to fossil fuels for heating. &#;Hope rests with the future heat pump,&#; one commentator wrote in the Annual Review of Energy.
Now the world faces yet another reckoning over energy supplies. When Russia, one of the world&#;s biggest sources of natural gas, invaded Ukraine in February , the price of gas soared &#; which in turn shoved heat pumps into the spotlight because with few exceptions they run on electricity, not gas. The same month, environmentalist Bill McKibben wrote a widely shared blog post titled &#;Heat pumps for peace and freedom&#; in which, referring to the Russian president, he argued that the U.S. could &#;peacefully punch Putin in the kidneys&#; by rolling out heat pumps on a massive scale while lowering Americans&#; dependence on fossil fuels. Heat pumps can draw power from domestic solar panels, for instance, or a power grid supplied predominantly by renewables.
Running the devices on green electricity can help to fight climate change, too, notes Karen Palmer, an economist and senior fellow at Resources for the Future, an independent research organization in Washington, D.C., who coauthored an analysis of policies to enhance energy efficiency in the Annual Review of Resource Economics. &#;Moving towards greater use of electricity for energy needs in buildings is going to have to happen, absent a technology breakthrough in something else,&#; she says.
This video illustrates the principle behind heat pumps. CREDIT: THIS OLD HOUSEThe IEA estimates that, globally, heat pumps have the potential to reduce carbon dioxide emissions by at least 500 million metric tons in , equivalent to the annual CO2 emissions produced by all the cars in Europe today.
Despite their long history and potential virtues, heat pumps have struggled to become commonplace in some countries. One reason is cost: The devices are substantially more expensive than gas heating units and, because natural gas has remained relatively cheap for decades, homeowners have had little incentive to switch.
There has also long been a perception that heat pumps won&#;t work as well in cold climates, especially in poorly insulated houses that require a lot of heat. In the U.K., for example, where houses tend to be rather drafty, some homeowners have long considered gas boilers a safer bet because they can supply hotter water (around 140 to 160 degrees Fahrenheit), to radiators, which makes it easier to heat up a room. By contrast, heat pumps tend to be most efficient when heating water to around 100 degrees Fahrenheit.
The cold-climate problem is arguably less of an issue than some think, however, given that there are multiple modern air source devices on the market that work well even when outside temperatures drop as low as minus 10 degrees Fahrenheit. Norway, for example, is considered one of the world leaders in heat pump deployment. Palmer has a heat pump in her U.S. home, along with a furnace as backup. &#;If it gets really cold, we can rely on the furnace,&#; she says.
Innovations in heat pump design are leading to units that are even more efficient, better suited to houses with low levels of insulation and &#; potentially &#; cheaper, too. For example, Yu says his and his colleagues&#; novel air source heat pump design could improve the COP by between 3 and 10%, while costing less than existing heat pump designs with comparable functionality. They are now looking to commercialize the technology.
Yu&#;s work is innovative, says Rick Greenough, an energy systems engineer now retired from De Montfort University in the U.K.. &#;I must admit this is a method I hadn&#;t actually thought of,&#; he says.
And there are plenty more ideas afoot. Greenough, for instance, has experimented with storing heat in the ground during warmer months, where it can be exploited by a heat pump when the weather turns cool. His design uses a circulating fluid to transfer excess heat from solar hot-water panels into shallow boreholes in the soil. That raises the temperature of the soil by around 22 degrees Fahrenheit, to a maximum of roughly 66 degrees Fahrenheit, he says. Then, in the winter, a heat pump can draw out some of this stored heat to run more efficiently when the air gets colder. This technology is already on the market, offered by some installers in the U.K., notes Greenough.
But most current heat pumps still only generate relatively low output temperatures, so owners of drafty homes may need to take on the added cost of insulation when installing a heat pump. Fortunately, a solution may be emerging: high-temperature heat pumps.
&#;We said, &#;Hey, why not make a heat pump that can actually one-on-one replace a gas boiler without having to really, really thoroughly insulate your house?&#;&#; says Wouter Wolfswinkel, program manager for business development at Swedish energy firm Vattenfall, which manufactures heat pumps. Vattenfall and its Dutch subsidiary Feenstra have teamed up to develop a high-temperature heat pump, expected to debut in .
In their design, they use CO2 as a refrigerant. But because the heat-pump system&#;s hot, high-pressure operating conditions prevent the gas from condensing or otherwise cooling down very easily, they had to find a way of reducing the refrigerant&#;s temperature in order for it to be able to absorb enough heat from the air once again when it returns to the start of the heat pump loop. To this end, they added a &#;buffer&#; to the system: a water tank where a layer of cooler water rests beneath hotter water above. The heat pump uses the lower layer of cooler water from the tank to adjust the temperature of the refrigerant as required. But it can also send the hotter water at the top of the tank out to radiators, at temperatures up to 185 degrees Fahrenheit.
The device is slightly less efficient than a conventional, lower temperature heat pump, Wolfswinkel acknowledges, offering a COP of around 265% versus 300%, depending on conditions. But that&#;s still better than a gas boiler (no more than 95% efficient), and as long as electricity prices aren&#;t significantly higher than gas prices, the high temperature heat pump could still be cheaper to run. Moreover, the higher temperature means that homeowners needn&#;t upgrade their insulation or upsize radiators right away, Wolfswinkel notes. This could help people make the transition to electrified heating more quickly.
A key test was whether Dutch homeowners would go for it. As part of a pilot trial, Vattenfall and Feenstra installed the heat pump in 20 households of different sizes in the town of Heemskerk, not far from Amsterdam. After a few years of testing, in June they gave homeowners the option of taking back their old gas boiler, which they had kept in their homes, or of using the high temperature heat pump on a permanent basis. &#;All of them switched to the heat pump,&#; says Wolfswinkel.
In some situations, home-by-home installations of heat pumps might be less efficient than building one large system to serve a whole neighborhood. For about a decade, Star Renewable Energy, based in Glasgow, has been building district systems that draw warmth from a nearby river or sea inlet, including a district heating system connected to a Norwegian fjord. A Scandinavian fjord might not be the first thing that comes to mind if you say the word &#;heat&#; &#; but the water deep in the fjord actually holds a fairly steady temperature of 46 degrees Fahrenheit, which heat pumps can exploit.
Via a very long pipe, the district heating system draws in this water and uses it to heat the refrigerant, in this case ammonia. A subsequent, serious increase of pressure for the refrigerant &#; to 50 atmospheres &#; raises its temperature to 250 degrees Fahrenheit. The hot refrigerant then passes its heat to water in the district heating loop, raising the temperature of that water to 195 degrees Fahrenheit. The sprawling system provides 85% of the hot water needed to heat buildings in the city of Drammen.
&#;That type of thing is very exciting,&#; says Greenough.
Not every home will be suitable for a heat pump. And not every budget can accommodate one, either. Yu himself says that the cost of replacing the gas boiler in his own home remains prohibitive. But it&#;s something he dreams of doing in the future. With ever-improving efficiencies, and rising sales in multiple countries, heat pumps are only getting harder for their detractors to dismiss. &#;Eventually,&#; says Yu, &#;I think everyone will switch to heat pumps.&#;
Chris Baraniuk is a freelance science journalist and nature lover who lives in Belfast, Northern Ireland. His work has been published by the BBC, the Guardian, New Scientist, Scientific American and Hakai Magazine, among other publications.
This article originally appeared in Knowable Magazine, an independent journalistic endeavor from Annual Reviews. Sign up for the newsletter.
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Evolution of the heat pump | Heat Pump History | Goodman
Like phones, televisions, and even cars, today&#;s split heat pump systems are very different from the originals installed in homes decades ago. Over time, their indoor comfort effectiveness and energy-efficient heat transfer properties have allowed heat pumps to grow in popularity - gaining approval from homeowners across the country.
Evolution of the Heat Pump
Every generation is shaped by world events and major cultural, political, and economic influences. These events have also impacted the evolution and popularity of the split system heat pump. Let&#;s look at the generational breakdown of the evolution of the split system, air-source heat pump:
Baby Boomer (born approximately between and )
:In the and 60s, heat pumps were becoming an electric heating option for the residential marketplace. By the late s, the average Baby Boomer was in their 20s and purchasing their first home. Suburban neighborhoods continued to expand across the country. Although air conditioners were available in some of these new homes, heat pumps were not a conventional heat source.
According to the US Census, only 1.8% of homes used electricity as a source of heat.1 Nearly 81% used some form of &#;fuel&#; to keep their home warm in the cold months of the year.1 By the US Census, 7.7% of households used electricity as a source of heat.1
Generation X (born approximately between and )
: By the s, an oil crisis was in full swing with many Generation Xers witnessing the full brunt of its impacts. As a result of the crisis, the heat pump became a more popular choice for heating and cooling homes because they used electricity instead of fuel.2 The decreased supply of fuel increased the cost, which may have played a significant factor in this growth. By , 18.4% of homes used electricity as a source of heat, more than doubling the rate of the previous decade.3
Before , the heat pump may have been merely an available alternative to fuel. Heat pumps, which have energy-efficient heat transfer properties, had a Seasonal Energy Efficiency Rating (SEER) of 6 or less and a Heating Seasonal Performance Factor (HSPF) of below 5. Energy-efficiency and conservation didn&#;t seem to be the primary objective. By , the energy conservation movement was in full swing, and Generation X&#;s push for more energy-efficient products was evident. As a result, the U.S. Department of Energy (DOE) raised the minimum energy-efficiency standards of heat pumps to 10 SEER/ 6.8 HSPF.
Millennial (born approximately between and )
: By the early s, the average Millennial was a teenager, and energy efficiency was a mainstream concept. During this time, nearly 67% of the population were used fuels as a heat source and 30.3% used electricity 4 Yet, energy conservation and minimizing environmental impacts continued to be an actionablepriority. In , the DOE raised the minimum required SEER/HSPF standards for split system heat pumps from 10 SEER/6.8 HSPF to 13 SEER/7.7 HSPF nationwide.
By , Millennials became the largest sector in the U.S. labor force, and the DOE once again raised the minimum SEER/HSPF requirement for split system heat pumps.5
Generation Z ( to early s)
: Born during a time of technological innovation, Generation Z is accustomed to accessing information at their fingertips. In , smart thermostats, such as the Google Nest, started populating the marketplace and indoor comfort could be controlled from mobile devices. As a result, some segments of Generation Z will never live in an environment with any other form of indoor temperature control.
By , the majority of Generation Z was enrolled in school and nearly 12.1 million households used electric heat pumps for indoor comfort.6
By the first waves of Generation Z were absorbed into the workforce and first-time home ownership was a reality for a few in their mid-20s. Meanwhile, heating and cooling equipment manufacturers continued to embrace technology-based, energy-efficiency advancements such as inverter technology. Heat pumps installations were increasing and shipments of air source heat pumps continued to escalate at a record pace.7
Generation Alpha (early s to s)
:This young generation is growing up in a fully digital world where it's commonplace for technology to set expectations. By , the heating and cooling industry continues to evolve and heat pump adoption numbers continue to rise.
Based on the data, advancements in heat pump technology are resulting in greater adoption across the U.S. as a heating and cooling equipment source. From to , according to Air Conditioning, Heating, and Refrigeration Institute (AHRI) data, there was nearly a 68% jump in shipments of heat pumps from U.S. manufacturers.8
NOTE: AHRI defines a shipment as when a unit transfers ownership from a manufacturer.8
As communities across the country are engaging in decarbonization and sustainability efforts, generations of citizens are embracing heat pumps and electrification. The Inflation Reduction Act of included a 10-year, historic plan to encourage customers to invest in energy-saving retrofits and replace inefficient HVAC systems. This legislation includes significant rebates and increased tax incentives for homeowners to replace fossil-fuel systems with eligible, high-efficiency ENERGY STAR® products. As part of this policy, qualified homeowners may be eligible for up to a $2,000 tax credit for eligible heat pumps. In the coming decade, Generation Alpha will certainly be influenced by the current decarbonization policies and the push for heat pump adoption.
What will indoor comfort expectations be like for a generation where technology sets expectations?
There may come a time when homeowners &#;expect&#; their heat pump to directly communicate status updates either to them, or their HVAC professional. Will their notion of &#;normal&#; extend to home heating and cooling equipment? Only time will tell!
More Heat Pump Options
Historically, air source heat pumps were only installed for homes in milder climates. However, in recent years, technology and engineering has allowed heat pumps to create a cozy, comfortable, electric heating alternative for homes in colder regions. Today&#;s cold climate heat pumps systems are now being installed from Alaska to Florida.9
Unlike the heat pump systems of the past, some of today&#;s models are equipped with inverter technology, like the Amana® brand S Series Heat Pump. Heat pumps with inverter technology are designed to control and modulate the electrical current running into the compressor&#;s motor, the heart of the indoor comfort system. This energy-saving technology allows the heat pump to adjust how much energy is needed to maintain indoor comfort. If looking to reduce Co2 emissions by investing in a heat pump, consider one that includes the benefits of inverter technology.
Additional advancements, including design and engineering evolutions, smart controls, and other mechanics that simplify installation have also impacted the indoor comfort and energy costs associated with residential heat pumps.
"Smart" Home Comfort
Numerous smart thermostats now offer a wide range of control features and connectivity with virtual assistants and smartphones, making it easier to align your heat pump operation with your lifestyle. As technology continues to become more integrated into heating and cooling equipment, the future of heat pumps will most likely evolve.
Imagine a technician contacting you because they received a diagnosis notification from your heat pump. This technician could potentially arrive at your home for a repair or proactive maintenance before you ever experience an uncomfortable temperature in your home. Future generations may never know what it is like to walk into a hot or cold home on a sweltering or frigid day! Isn&#;t that a comforting thought!
1, 3, 4 United States Census Bureau. (, October 31). Historical Census of Housing Tables. Retrieved from Census of Housing: https://www.census.gov/data/tables/time-series/dec/coh-fuels.html.
2 Cormany, Charles. The Perfect Solution, and Why it is Not Working. 19 January . http://www.efficiencyfirstca.org/news//01/19/perfect-solution-and-why-it-not-working. 30 July .
5 Pew Research Center. The Generations Defined. 8 May . https://www.pewresearch.org/fact-tank//04/11/millennials-largest-generation-us-labor-force/ 15 Feb .
6. U.S. Energy Information Administration, U.S. households&#; heating equipment choices are diverse and vary by climate region, April 6, . https://www.eia.gov/todayinenergy/detail.php?id=
7. AHRI, Monthly Shipments Feb 12, https://www.ahrinet.org/sites/default/files/-02/DecStatisticalRelease_4.pdf
8. International Energy Agency, Heat Pumps, September https://www.iea.org/reports/heat-pumps
9. Vanessa Stevens, Colin Craven, Robbin Garber-Slaght. Air Source Heat Pumps in Southeast Alaska. Fairbanks: Cold Climate Housing Research Center, . http://www.cchrc.org/sites/default/files/docs/ASHP_final_0.pdf
If you want to learn more, please visit our website Commercial Air Source Heat Pump.
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