Jump to content

Air source heat pump

From Wikipedia, the free encyclopedia
This article is about details of the most common type of heat pump. For more general information, see heat pump.

Heat pump on balcony of apartment

An air source heat pump (ASHP) is a heat pump that can absorb heat from air outside a building and release it inside; it uses the same vapor-compression refrigeration process and much the same equipment as an air conditioner, but in the opposite direction. ASHPs are the most common type of heat pump and, usually being smaller, tend to be used to heat individual houses or flats rather than blocks, districts or industrial processes.[1][2]

Air-to-air heat pumps provide hot or cold air directly to rooms, but do not usually provide hot water. Air-to-water heat pumps use radiators or underfloor heating to heat a whole house and are often also used to provide domestic hot water.

An ASHP can typically gain 4 kWh thermal energy from 1 kWh electric energy. They are optimized for flow temperatures between 30 and 40 °C (86 and 104 °F), suitable for buildings with heat emitters sized for low flow temperatures. With losses in efficiency, an ASHP can even provide full central heating with a flow temperature up to 80 °C (176 °F).[3]

As of 2023 about 10% of building heating worldwide is from ASHPs. They are the main way to phase out gas boilers (also known as "furnaces") from houses, to avoid their greenhouse gas emissions.[4]

Air-source heat pumps are used to move heat between two heat exchangers, one outside the building which is fitted with fins through which air is forced using a fan and the other which either directly heats the air inside the building or heats water which is then circulated around the building through radiators or underfloor heating which releases the heat to the building. These devices can also operate in a cooling mode where they extract heat via the internal heat exchanger and eject it into the ambient air using the external heat exchanger. Some can be used to heat water for washing which is stored in a domestic hot water tank.[5]

Air-source heat pumps are relatively easy and inexpensive to install, so are the most widely used type. In mild weather, coefficient of performance (COP) may be between 2 and 5, while at temperatures below around −8 °C (18 °F) an air-source heat pump may still achieve a COP of 1 to 4.[6]

While older air-source heat pumps performed relatively poorly at low temperatures and were better suited for warm climates, newer models with variable-speed compressors remain highly efficient in freezing conditions allowing for wide adoption and cost savings in places like Minnesota and Maine in the United States.[7]

Technology

[edit]
Air source heat pump

Air at any natural temperature contains some heat. An air source heat pump transfers some of this from one place to another, for example between the outside and inside of a building.

An air-to air system can be designed to transfer heat in either direction, to heat or cool the interior of the building in winter and summer respectively. Internal ducting may be used to distribute the air.[8] An air-to-water system only pumps heat inwards, and can provide space heating and hot water.[9] For simplicity, the description below focuses on use for interior heating.

The technology is similar to a refrigerator or freezer or air conditioning unit: the different effect is due to the location of the different system components. Just as the pipes on the back of a refrigerator become warm as the interior cools, so an ASHP warms the inside of a building whilst cooling the outside air.

The main components of a split-system (called split as there are both inside and outside coils) air source heat pump are:

  • An outdoor evaporator heat exchanger coil, which extracts heat from ambient air
  • One or more[10] indoor condenser heat exchanger coils. They transfer the heat into the indoor air, or an indoor heating system such as water-filled radiators or underfloor circuits and a domestic hot water tank.

Less commonly a packaged ASHP has everything outside, with hot (or cold) air sent inside through a duct.[11] These are also called monobloc and are useful for keeping flammable propane outside the house.[4]

An ASHP can provide three or four times as much heat as an electric resistance heater using the same amount of electricity.[12] Burning gas or oil will emit carbon dioxide and also NOx, which can be harmful to health.[13] An air source heat pump issues no carbon dioxide, nitrogen oxide or any other kind of gas. It uses a small amount of electricity to transfer a large amount of heat.

Most ASHPs are reversible and are able to either warm or cool buildings[14] and in some cases also provide domestic hot water. The use of an air-to-water heat pump for house cooling has been criticised.[15]

An internal view of the outdoor unit of an air source heat pump
A: indoor compartment, B: outdoor compartment, I: insulation, 1: condenser, 2: expansion valve, 3: evaporator, 4: compressor

Heating and cooling is accomplished by pumping a refrigerant through the heat pump's indoor and outdoor coils. Like in a refrigerator, a compressor, condenser, expansion valve and evaporator are used to change states of the refrigerant between colder liquid and hotter gas states.

When the liquid refrigerant at a low temperature and low pressure passes through the outdoor heat exchanger coils, ambient heat causes the liquid to boil (change to gas or vapor). Heat energy from the outside air has been absorbed and stored in the refrigerant as latent heat. The gas is then compressed using an electric pump; the compression increases the temperature of the gas.

Inside the building, the gas passes through a pressure valve into heat exchanger coils. There, the hot refrigerant gas condenses back to a liquid and transfers the stored latent heat to the indoor air, water heating or hot water system. The indoor air or heating water is pumped across the heat exchanger by an electric pump or fan.

The cool liquid refrigerant then re-enters the outdoor heat exchanger coils to begin a new cycle. Each cycle usually takes a few minutes.[12]

Most heat pumps can also operate in a cooling mode where the cold refrigerant is moved through the indoor coils to cool the room air.

As of 2024 tech other than vapour compression is insignificant in the market.[16]

Usage

[edit]

ASHPs are the most common type of heat pump and, usually being smaller, are generally more suitable to heat individual houses rather than blocks of flats, compact urban districts or industrial processes.[1] In dense city centres heat networks may be better than ASHP.[1] Air source heat pumps are used to provide interior space heating and cooling even in colder climates, and can be used efficiently for water heating in milder climates. A major advantage of some ASHPs is that the same system may be used for heating in winter and cooling in summer. Though the cost of installation is generally high, it is less than the cost of a ground source heat pump, because a ground source heat pump requires excavation to install its ground loop. The advantage of a ground source heat pump is that it has access to the thermal storage capacity of the ground which allows it to produce more heat for less electricity in cold conditions.

Home batteries can mitigate the risk of power cuts and like ASHPs are becoming more popular.[17] Some ASHPs can be coupled to solar panels as primary energy source, with a conventional electric grid as backup source.[citation needed]

Thermal storage solutions incorporating resistance heating can be used in conjunction with ASHPs. Storage may be more cost-effective if time of use electricity rates are available. Heat is stored in high density ceramic bricks contained within a thermally-insulated enclosure;[18] storage heaters are an example. ASHPs may also be paired with passive solar heating. Thermal mass (such as concrete or rocks) heated by passive solar heat can help stabilize indoor temperatures, absorbing heat during the day and releasing heat at night, when outdoor temperatures are colder and heat pump efficiency is lower.

Replacing gas heating in existing houses

[edit]

Good home insulation is important.[19] As of 2023 ASHPs are bigger than gas boilers and need more space outside, so the process is more complex and can be more expensive than if it was possible to just remove a gas boiler and install an ASHP in its place.[4][20] If running costs are important choosing the right size is important because an ASHP which is too large will be more expensive to run.[21]

It can be more complicated to retrofit conventional heating systems that use radiators/radiant panels, hot water baseboard heaters, or even smaller diameter ducting, with ASHP-sourced heat. The lower heat pump output temperatures means radiators (and possibly pipes) may have to be replaced with larger sizes, or a low temperature underfloor heating system installed instead.[22]

Alternatively, a high temperature heat pump can be installed and existing heat emitters can be retained, however as of 2023 these heat pumps are more expensive to buy and run so may only be suitable for buildings which are hard to alter or insulate, such as some large historic houses.[23]

ASHP are claimed to be healthier than fossil-fuelled heating such as gas heaters by maintaining a more even temperature and avoiding harmful fumes risk.[19] By filtering the air and reducing humidity in hot humid summer climates, they are also said to reduce dust, allergens, and mold, which poses a health risk.[24]

In cold climates

[edit]
The outdoor unit of an air source heat pump operating in freezing conditions

Operation of normal ASHPs is generally not recommended below −10 °C.[25] However, ASHPs designed specifically for very cold climates (in the US, these are certified under Energy Star[26]) can extract useful heat from ambient air as cold as −30 °C (−22 °F) but electric resistance heating may be more efficient below −25 °C.[25] This is made possible by the use of variable-speed compressors, powered by inverters.[26] Although air source heat pumps are less efficient than well-installed ground source heat pumps (GSHPs) in cold conditions, air source heat pumps have lower initial costs and may be the most economic or practical choice.[27] A hybrid system, with both a heat pump and an alternative source of heat such as a fossil fuel boiler, may be suitable if it is impractical to properly insulate a large house.[28] Alternatively multiple heat pumps or a high temperature heat pump may be considered.[28]

In some weather conditions condensation will form and then freeze onto the coils of the heat exchanger of the outdoor unit, reducing air flow through the coils. To clear this condensation, the unit operates a defrost cycle, switching to cooling mode for a few minutes and heating the coils until the ice melts. Air-to-water heat pumps use heat from the circulating water for this purpose, which results in a small and probably undetectable drop in water temperature;[29] for air-to-air systems, heat is either taken from the air in the building or using an electrical heater.[30] Some air-to-air systems simply stop the operation of the fans of both units and switch to cooling mode so that the outdoor unit returns to being the condenser such that it heats up and defrosts.

As discussed above, typical ASHPs struggle to perform efficiently at low temperatures. While GSHPs connected to hydronic heating systems can operate in such conditions, their installation is costly and material-intensive.[31] A novel alternative, the ground-source air heat pump (GSAHP), combines a conventional ASHP with a heat collector, known as a ground heat exchanger (GHE) or borehole exchanger, buried in the ground. A GSAHP includes three main components: a horizontal or vertical GHE, a heat pump unit, and a fan. The heat pump unit has an evaporator, compressor, and condenser. Heat is collected from the ground using an antifreeze solution circulated through pipes in the GHE, transferring thermal energy to the refrigerant in the heat pump unit. The refrigerant then undergoes a heat pump cycle, being compressed and heated before delivering thermal energy to a refrigerant-to-air heat exchanger. A fan then blows the heated air into the indoor space.

Unlike GSHPs, GSAHPs do not require hydronic systems to distribute heat through pipes. Instead, GSAHPs use a fan to transfer heat directly into the indoor environment, whereas GSHPs rely on underfloor heating or wall-mounted radiators. Installation costs for GSAHPs are intermediate between ASHP and GSHP systems; while they eliminate the need for indoor pipework, they still require drilling or digging for the GHE. GSAHPs are also distinct from ground-coupled heat exchangers or earth tubes, which do not typically use compressors or chemicals to function.

Electricity usage significantly influences the climate impacts of heat pump systems. A study found that the coefficient of performance of GSAHPs is approximately 35% higher than that of conventional ASHPs in a school building.[32] This efficiency advantage arises from the GSAHP’s ability to extract heat from the ground, where temperatures remain relatively stable, especially during winter. Over a heat pump’s life cycle, the operation phase contributes about 84% of the total climate impacts, primarily due to electricity consumption.[33] Consequently, a higher COP in cold conditions delivers substantial environmental benefits alongside cost savings. These advantages are most notable in colder climates, where the efficiency of ASHPs typically declines.

Noise

[edit]

An air source heat pump requires an outdoor unit containing moving mechanical components including fans which produce noise. Modern devices offer schedules for silent mode operation with reduced fan speed. This will reduce the maximum heating power but can be applied at mild outdoor temperatures without efficiency loss. Acoustic enclosures are another approach to reduce the noise in a sensitive neighbourhood. In insulated buildings, operation can be paused at night without significant temperature loss. Only at low temperatures, frost protection forces operation after a few hours. Proper siting is also important.[34]

In the United States, the allowed night-time noise level is 45 A-weighted decibels (dBA).[35] In the UK the limit is set at 42 dB measured from the nearest neighbour[36] according to the MCS 020 standard[37] or equivalent.[38] In Germany the limit in residential areas is 35, which is usually measured by European Standard EN 12102.[39]

Another feature of air source heat pumps (ASHPs) external heat exchangers is their need to stop the fan from time to time for a period of several minutes in order to get rid of frost that accumulates in the outdoor unit in the heating mode. After that, the heat pump starts to work again. This part of the work cycle results in two sudden changes of the noise made by the fan. The acoustic effect of such disruption is especially powerful in quiet environments where background night-time noise may be as low as 0 to 10dBA. This is included in legislation in France. According to the French concept of noise nuisance, "noise emergence" is the difference between ambient noise including the disturbing noise, and ambient noise without the disturbing noise.[40][41] By contrast a ground source heat pump has no need for an outdoor unit with moving mechanical components.

Efficiency ratings

[edit]

The efficiency of air source heat pumps is measured by the coefficient of performance (COP). A COP of 4 means the heat pump produces 4 units of heat energy for every 1 unit of electricity it consumes. Within temperature ranges of −3 °C (27 °F) to 10 °C (50 °F), the COP for many machines is fairly stable. Approximately TheoreticalMaxCOP = (desiredIndoorTempC + 273) ÷ (desiredIndoorTempC - outsideTempC).[citation needed][42][better source needed]

In mild weather with an outside temperature of 10 °C (50 °F), the COP of efficient air source heat pumps ranges from 4 to 6.[43] However, on a cold winter day, it takes more work to move the same amount of heat indoors than on a mild day.[44] The heat pump's performance is limited by the Carnot cycle and will approach 1.0 as the outdoor-to-indoor temperature difference increases, which for most air source heat pumps happens as outdoor temperatures approach −18 °C (0 °F).[citation needed]Heat pump construction that enables carbon dioxide as a refrigerant may have a COP of greater than 2 even down to −20 °C, pushing the break-even figure downward to −30 °C (−22 °F).[citation needed] A ground source heat pump has comparatively less of a change in COP as outdoor temperatures change, because the ground from which they extract heat has a more constant temperature than outdoor air.

The design of a heat pump has a considerable impact on its efficiency. Many air source heat pumps are designed primarily as air conditioning units, mainly for use in summer temperatures. Designing a heat pump specifically for the purpose of heat exchange can attain greater COP and an extended life cycle. The principal changes are in the scale and type of compressor and evaporator.

Seasonally adjusted heating and cooling efficiencies are given by the heating seasonal performance factor (HSPF) and seasonal energy efficiency ratio (SEER) respectively. In the US the legal minimum efficiency is 14 or 15 SEER and 8.8 HSPF.[26]

Variable speed compressors are more efficient because they can often run more slowly and because the air passes through more slowly giving its water more time to condense, thus more efficient as drier air is easier to cool. However, they are more expensive and more likely to need maintenance or replacement.[24] Maintenance such as changing filters can improve performance by 10% to 25%.[45]

Refrigerant types

[edit]
This section is an excerpt from Heat pump § Refrigerant choice.[edit]

Pure refrigerants can be divided into organic substances (hydrocarbons (HCs), chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), hydrofluoroolefins (HFOs), and HCFOs), and inorganic substances (ammonia (NH
3), carbon dioxide (CO
2), and water (H
2O)[46]).[47] Their boiling points are usually below −25 °C.[48]

In the past 200 years, the standards and requirements for new refrigerants have changed. Nowadays low global warming potential (GWP) is required, in addition to all the previous requirements for safety, practicality, material compatibility, appropriate atmospheric life,[clarification needed] and compatibility with high-efficiency products. By 2022, devices using refrigerants with a very low GWP still have a small market share but are expected to play an increasing role due to enforced regulations,[49] as most countries have now ratified the Kigali Amendment to ban HFCs.[50] Isobutane (R600A) and propane (R290) are far less harmful to the environment than conventional hydrofluorocarbons (HFC) and are already being used in air-source heat pumps.[51] Propane may be the most suitable for high temperature heat pumps.[52] Ammonia (R717) and carbon dioxide (R-744) also have a low GWP. As of 2023 smaller CO
2 heat pumps are not widely available and research and development of them continues.[53] A 2024 report said that refrigerants with GWP are vulnerable to further international restrictions.[54]

Until the 1990s, heat pumps, along with fridges and other related products used chlorofluorocarbons (CFCs) as refrigerants, which caused major damage to the ozone layer when released into the atmosphere. Use of these chemicals was banned or severely restricted by the Montreal Protocol of August 1987.[55]

Replacements, including R-134a and R-410A, are hydrofluorocarbons (HFC) with similar thermodynamic properties with insignificant ozone depletion potential (ODP) but had problematic GWP.[56] HFCs are powerful greenhouse gases which contribute to climate change.[57][58] Dimethyl ether (DME) also gained in popularity as a refrigerant in combination with R404a.[59] More recent refrigerants include difluoromethane (R32) with a lower GWP, but still over 600.

refrigerant 20-year GWP 100-year GWP
R-290 propane[60] 0.072 0.02
R-600a isobutane 3[61]
R-32[60] 491 136
R-410a[62] 4705 2285
R-134a[62] 4060 1470
R-404a[62] 7258 4808

Devices with R-290 refrigerant (propane) are expected to play a key role in the future.[52][63] The 100-year GWP of propane, at 0.02, is extremely low and is approximately 7000 times less than R-32. However, the flammability of propane requires additional safety measures: the maximum safe charges have been set significantly lower than for lower flammability refrigerants (only allowing approximately 13.5 times less refrigerant in the system than R-32).[64][65][66] This means that R-290 is not suitable for all situations or locations. Nonetheless, by 2022, an increasing number of devices with R-290 were offered for domestic use, especially in Europe.[citation needed]

At the same time,[when?] HFC refrigerants still dominate the market. Recent government mandates have seen the phase-out of R-22 refrigerant. Replacements such as R-32 and R-410A are being promoted as environmentally friendly but still have a high GWP.[67] A heat pump typically uses 3 kg of refrigerant. With R-32 this amount still has a 20-year impact equivalent to 7 tons of CO2, which corresponds to two years of natural gas heating in an average household. Refrigerants with a high ODP have already been phased out.[citation needed]

Impact on decarbonization and electricity supply

[edit]

Heat pumps are key to decarbonizing home energy use by phasing out gas boilers.[20][12] As of 2024 the IEA says that 500 million tonnes of CO2 emissions could be cut by 2030.[68]

As wind farms are increasingly used to supply electricity to some grids, such as Canada's Yukon Territory, the increased winter load matches well with the increased winter generation from wind turbines, and calmer days result in decreased heating load for most houses even if the air temperature is low.[69]

Heat pumps could help stabilize grids through demand response.[70] As heat pump penetration increases some countries, such as the UK, may need to encourage households to use thermal energy storage, such as very well insulated water tanks.[71] In some countries, such as Australia, integration of this thermal storage with rooftop solar would also help.[72]

Although higher cost heat pumps can be more efficient a 2024 study concluded that for the UK "from an energy system perspective, it is overall cost-optimal to design heat pumps with nominal COP in the range of 2.8–3.2, which typically has a specific cost lower than 650 £/kWth, and simultaneously to invest in increased capacities of renewable energy generation technologies and batteries, in the first instance, followed by OCGT and CCGT with CCS."[73]

Economics

[edit]

Cost

[edit]

As of 2023 buying and installing an ASHP in an existing house is expensive if there is no government subsidy, but the lifetime cost will likely be less than or similar to a gas boiler and air conditioner.[74][75] This is generally also true if cooling is not required, as the ASHP will likely last longer if only heating.[76] The lifetime cost of an air source heat pump will be affected by the price of electricity compared to gas (where available), and may take two to ten years to break even.[74] The IEA recommends governments subsidize the purchase price of residential heat pumps, and some countries do so.[77]

Market

[edit]

In Norway,[78] Australia and New Zealand most heating is from heat pumps. In 2022 heat pumps outsold fossil fuel based heating in the US and France.[77] In the UK, annual heat pump sales have steadily grown in recent years with 26,725 heat pumps sold in 2018, a figure which has increased to 60,244 heat pumps sales in 2023.[79] ASHPs can be helped to compete by increasing the price of fossil gas compared to that of electricity and using suitable flexible electricity pricing.[20] In the US air-to-air is the most common type.[80] As of 2023 over 80% of heat pumps are air source.[12] In 2023 the IEA appealed for better data - especially on air-to-air.[77]

Maintenance and reliability

[edit]

While many of the maintenance needs for air source heat pumps remain the same as for conventional air conditioning and furnace installations, such as regular air filter replacements and cleaning of both the indoor evaporator and outdoor condenser coils, there are additional maintenance measures unique to the operation of air source heat pumps.[81][82][83] As a heat pump running in cooling mode operates essentially the same as a conventional air conditioning system, these measures primarily concern the performance of ASHPs during the winter, and most significantly in colder climates.[84][85]

In colder climates, where the compressor works harder to extract heat from the outside air, it is critical to the performance of an ASHP that the buildup of ice and frost on the outdoor coil be prevented, as this acts as an insulation layer and decreases the rate of heat exchange by blocking the continuous flow of air over the outdoor coil.[86] To prevent this, it is necessary to keep the outdoor coil clean of any dirt or grime, as this can trap moisture from the air, which freezes over the coil.[87] As well, it is necessary to keep the fins surrounding the condenser coil and air intake grill of the outdoor unit free of any debris, such as leaves, that could further block the flow of air and decrease heat exchange.[88][89] This works to minimize the need for frequent defrost cycling that puts the heat pump into a cooling mode to send heated refrigerant to the condenser coil to melt accumulated ice.[90] This can cause pressure fluctuations in the refrigerant lines that lead to refrigerant leaks and diminish performance.[91][92]

When heating performance drops, an ASHP can be kept reliable through its auxiliary heating strip that provides an additional source of heat through electrical resistance to compensate for any missed heating, which comes at the cost of being significantly less efficient.[93][94]

It is thought that ASHP need less maintenance than fossil fuelled heating, and some say that ASHPs are easier to maintain than ground source heat pumps due to the difficulty of finding and fixing underground leaks. Installing too small an ASHP could shorten its lifetime (but one which is too large will be less efficient).[95] However others say that boilers require less maintenance than ASHPs.[96] A Consumer Reports survey found that "on average, around half of heat pumps are likely to experience problems by the end of the eighth year of ownership".[97]

History

[edit]

Modern chemical refrigeration techniques developed after the proposal of the Carnot cycle in 1824. Jacob Perkins invented an ice-making machine that used ether in 1843, and Edmond Carré built a refrigerator that used water and sulfuric acid in 1850. In Japan, Fusanosuke Kuhara, founder of Hitachi, Ltd., made an air conditioner for his own home use using compressed CO2 as a refrigerant in 1917.[98]

In 1930 Thomas Midgley Jr. discovered dichlorodifluoromethane, a chlorinated fluorocarbon (CFC) known as freon. CFCs rapidly replaced traditional refrigerant substances, including CO2 (which proved hard to compress for domestic use[99]), for use in heat pumps and refrigerators. But from the 1980s CFCs began to lose favor as refrigerant when their damaging effects on the ozone layer were discovered. Two alternative types of refrigerant, hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs), also lost favor when they were identified as greenhouse gases (additionally, HCFCs were found to be more damaging to the ozone layer than originally thought). The Vienna Convention for the Protection of the Ozone Layer, the Montreal Protocol and the Kyoto Protocol call for the complete abandonment of such refrigerants by 2030.

In 1989, amid international concern about the effects of chlorofluorocarbons and hydrochlorofluorocarbons on the ozone layer, scientist Gustav Lorentzen and SINTEF patented a method for using CO2 as a refrigerant in heating and cooling. Further research into CO2 refrigeration was then conducted at Shecco (Sustainable HEating and Cooling with CO2) in Brussels, Belgium, leading to increasing use of CO2 refrigerant technology in Europe.[99]

In 1993 the Japanese company Denso, in collaboration with Gustav Lorentzen, developed an automobile air conditioner using CO2 as a refrigerant. They demonstrated the invention at the June 1998 International Institute of Refrigeration/Gustav Lorentzen Conference.[100] After the conference, CRIEPI (Central Research Institute of Electric Power Industry) and TEPCO (The Tokyo Electric Power Company) approached Denso about developing a prototype air conditioner using natural refrigerant materials instead of freon. Together they produced 30 prototype units for a year-long experimental installation at locations throughout Japan, from the cold climate of Hokkaidō to hotter Okinawa. After this successful feasibility study, Denso obtained a patent to compress CO2 refrigerant for use in a heat pump from SINTEF in September 2000. During the early 21st century CO2 heat pumps, under the EcoCute patent, became popular for new-build housing in Japan but were slower to take off elsewhere.[101]

Manufacturing

[edit]

Demand for heat pumps increased in the first quarter of the 21st century in the US and Europe, with governments subsidizing them to increase energy security and decarbonisation. Europeans tend to use air-to-water (also called hydronic) systems which utilize radiators, rather than the air-to-air systems more common elsewhere. Asian countries made three-quarters of heat pumps globally in 2021.[102]

See also

[edit]

References

[edit]
  1. ^ a b c "Why Britain's homes will need different types of heat pump". The Economist. ISSN 0013-0613. Retrieved 19 February 2024.
  2. ^ "What is an Air-Source Heat Pump? A Complete Guide In 2024". NEWNTIDE. 24 October 2024. Retrieved 30 September 2024.
  3. ^ Le, Khoa; Huang, M.J.; Hewitt, Neil (2018). "Domestic High Temperature Air Source Heat Pump: Performance Analysis Using TRNSYS Simulations". International High Performance Buildings Conference. West Lafayette, IN, USA: 5th International High Performance Buildings Conference at Purdue University: 1. Retrieved 20 February 2022.
  4. ^ a b c "Heat pumps show how hard decarbonisation will be". The Economist. ISSN 0013-0613. Retrieved 14 September 2023.
  5. ^ Lawrence, Karen. "Air source heat pumps explained". Which?. Archived from the original on 4 October 2022. Retrieved 4 October 2022.
  6. ^ Canada, Natural Resources (22 April 2009). "Heating and Cooling With a Heat Pump". natural-resources.canada.ca. Retrieved 22 February 2024.
  7. ^ "Heat pumps do work in the cold – Americans just don't know it yet". Grist. 9 May 2022. Archived from the original on 9 May 2022. Retrieved 9 May 2022.
  8. ^ "The 9 Types of Heat Pumps". ACHR News. Retrieved 15 September 2023.
  9. ^ Lawrence, Karen; Massey, Jake (14 July 2023). "Air source heat pumps explained". Which?.
  10. ^ "Ductless Mini-Split Heat Pumps". Energy.gov. Retrieved 14 September 2023.
  11. ^ "Air-Source Heat Pumps". Energy.gov. Retrieved 14 September 2023.
  12. ^ a b c d "Everything you need to know about the wild world of heat pumps". MIT Technology Review. Retrieved 19 September 2023.
  13. ^ "Gas boilers and NOx: the hidden emitter" (PDF). Energy & Climate Intelligence Unit. October 2020. Retrieved 20 January 2024.
  14. ^ The Contribution of Reversible Air-to-Air Heat Pumps to the UK's Obligation under the Renewable Energy Directive (2009/28/EC) - A Delta-ee Report for the Department for Business, Energy and Industrial Strategy (PDF) (Report). Delta Energy & Environment. 2017. virtually all air-air heat pumps sold today are reversible (p.7)
  15. ^ Hendra, Graham (5 May 2021). "Four reasons not cool your house using a heat pump". Renewable Heating Hub. Retrieved 23 December 2023.
  16. ^ "Annex 53 Advanced Cooling/Refrigeration Technologies 2 page summary". HPT - Heat Pumping Technologies. Retrieved 19 February 2024.
  17. ^ Ambrose, Jillian (14 August 2023). "UK homes install 'record number' of solar panels and heat pumps". The Guardian. ISSN 0261-3077. Retrieved 16 September 2023.
  18. ^ Franklin Energy Services, LLC (2011). "Air Source Heat Pump Efficiency Gains from Low Ambient Temperature Operation Using Supplemental Electric Heating: Thermal Storage Supplemental Heating Systems" (PDF). Minnesota Division of Energy Resources; Minnesota Department of Commerce. p. 9. Archived from the original (PDF) on 11 June 2014. Retrieved 15 October 2014.
  19. ^ a b "Advice | I tried, and failed, to install a heat pump. Here's how to do it right". Washington Post. 28 February 2023. Retrieved 19 February 2024.
  20. ^ a b c Harris, B. (14 July 2023). "Heat pumps" (PDF). UK Parliament . Retrieved 20 January 2024.
  21. ^ "Here's How to Pick the Right Size Heat Pump for Your Home". CNET. Retrieved 18 September 2023.
  22. ^ "Do Heat Pumps Work with Radiators? | Heat Pump House". heatpumphouse.com. Retrieved 19 February 2024.
  23. ^ Jackman, Josh (28 January 2022). "High Temperature Heat Pumps | Are They Worth It?". The Eco Experts. Retrieved 17 September 2023.
  24. ^ a b "Single Stage vs. Two Stage vs. Variable Speed For Heat Pump/Air Conditioner". How to Choose Best HVAC Systems. 4 April 2018. Retrieved 19 February 2024.
  25. ^ a b "Cold climate air source heat pumps". www.hydro.mb.ca. Retrieved 15 September 2023.
  26. ^ a b c "Can Heat Pumps Actually Work in Cold Climates?". Consumer Reports. 2 August 2022. Retrieved 15 September 2023.
  27. ^ "Are Air Source Heat Pumps A Threat To Geothermal Heat Pump Suppliers?". Forbes. Retrieved 15 October 2014.
  28. ^ a b "Hybrid heat pumps". Energy Saving Trust. Retrieved 30 September 2023.
  29. ^ "How to defrost a heat pump in winter". Evergreen Energy. February 2018. Retrieved 14 September 2021.
  30. ^ "Defrost Cycle of a Heat Pump". International Association of Home Inspectors. Retrieved 14 September 2021.
  31. ^ Mattinen, Maija K.; Nissinen, Ari; Hyysalo, Sampsa; Juntunen, Jouni K. (February 2015). "Energy Use and Greenhouse Gas Emissions of Air‐Source Heat Pump and Innovative Ground‐Source Air Heat Pump in a Cold Climate". Journal of Industrial Ecology. 19 (1): 61–70. doi:10.1111/jiec.12166. ISSN 1088-1980.
  32. ^ Kim, Euiyoung; Lee, Jaekeun; Jeong, Youngman; Hwang, Yujin; Lee, Sangheon; Park, Naehyun (1 July 2012). "Performance evaluation under the actual operating condition of a vertical ground source heat pump system in a school building". Energy and Buildings. 50: 1–6. doi:10.1016/j.enbuild.2012.02.006. ISSN 0378-7788.
  33. ^ Greening, Benjamin; Azapagic, Adisa (1 March 2012). "Domestic heat pumps: Life cycle environmental impacts and potential implications for the UK". Energy. Sustainable Energy and Environmental Protection 2010. 39 (1): 205–217. doi:10.1016/j.energy.2012.01.028. ISSN 0360-5442.
  34. ^ "HEAT PUMPS & NOISE: A NEIGHBOURLY INSTALLATION GUIDE" (PDF).
  35. ^ "Monica S. Hammer, Tracy K. Swinburn, and Richard L. Neitzel "Environmental Noise Pollution in the United States: Developing an Effective Public Health Response" Environmental Health Perspectives V122,I2,2014". Archived from the original on 2 July 2016. Retrieved 25 January 2016.
  36. ^ "How Noisy Are Heat Pumps?". Heat Pumps UK. 11 April 2022. Retrieved 14 September 2023.
  37. ^ "Microgeneration Installation Standard MCS 020" (PDF). MCS. Retrieved 17 March 2024.
  38. ^ "Noise and Neighbours: The rules regarding noise from heat pump outdoor units - MCS 020 or equivalent". Checkmark. Retrieved 17 March 2024.
  39. ^ "Petition No 0922/2020 by F.B. (German) on low-frequency noise limit values" (PDF).
  40. ^ "Hiil innovating Justice "How to determine acceptable levels of noise nuisance (France)". Archived from the original on 12 February 2017. Retrieved 25 January 2016.
  41. ^ "Code de la santé publique – Article R1334-33 (in French)". Retrieved 8 February 2016.
  42. ^ "Is there some theoretical maximum coefficient of performance (COP) for heat pumps and chillers?". Physics Stack Exchange. Retrieved 19 February 2024.
  43. ^ "Wärmepumpen mit Prüf- / Effizienznachweis (heat pumps with efficiency validation)". BAFA (Federal Office for Economic Affairs and Export Control in Germany). Retrieved 20 February 2022.
  44. ^ "Air Source Heat Pumps". ICAX. Retrieved 20 January 2024.
  45. ^ "Operating and Maintaining Your Heat Pump". Energy.gov. Retrieved 19 February 2024.
  46. ^ Chamoun, Marwan; Rulliere, Romuald; Haberschill, Philippe; Berail, Jean Francois (1 June 2012). "Dynamic model of an industrial heat pump using water as refrigerant". International Journal of Refrigeration. 35 (4): 1080–1091. doi:10.1016/j.ijrefrig.2011.12.007. ISSN 0140-7007.
  47. ^ Wu, Di (2021). "Vapor compression heat pumps with pure Low-GWP refrigerants". Renewable and Sustainable Energy Reviews. 138: 110571. doi:10.1016/j.rser.2020.110571. ISSN 1364-0321. S2CID 229455137. Archived from the original on 24 September 2023. Retrieved 17 November 2022.
  48. ^ "Everything you need to know about the wild world of heat pumps". MIT Technology Review. Archived from the original on 1 August 2023. Retrieved 19 September 2023.
  49. ^ Miara, Marek (22 October 2019). "Heat Pumps with Climate-Friendly Refrigerant Developed for Indoor Installation". Fraunhofer ISE. Archived from the original on 20 February 2022. Retrieved 21 February 2022.
  50. ^ Rabe, Barry G. (23 September 2022). "Pivoting from global climate laggard to leader: Kigali and American HFC policy". Brookings. Archived from the original on 4 October 2022. Retrieved 4 October 2022.
  51. ^ Itteilag, Richard L. (9 August 2012). Green Electricity and Global Warming. AuthorHouse. p. 77. ISBN 9781477217405. Archived from the original on 23 November 2021. Retrieved 1 November 2020.
  52. ^ a b "Propane-powered heat pumps are greener". The Economist. 6 September 2023. ISSN 0013-0613. Archived from the original on 17 September 2023. Retrieved 17 September 2023.
  53. ^ "Smart CO2 Heat Pump". www.dti.dk. Archived from the original on 30 January 2023. Retrieved 17 September 2023.
  54. ^ "Annex 53 Advanced Cooling/Refrigeration Technologies 2 page summary". HPT - Heat Pumping Technologies. Retrieved 19 February 2024.
  55. ^ "Handbook for the Montreal Protocol on Substances that Deplete the Ozone Layer – 7th Edition". United Nations Environment Programme – Ozone Secretariat. 2007. Archived from the original on 30 May 2016. Retrieved 18 December 2016.
  56. ^ "Refrigerants – Environmental Properties". The Engineering ToolBox. Archived from the original on 14 March 2013. Retrieved 12 September 2016.
  57. ^ R-410A#Environmental effects.
  58. ^ Ecometrica.com (27 June 2012). "Calculation of green house gas potential of R-410A". Archived from the original on 13 July 2015. Retrieved 13 July 2015.
  59. ^ "R404 and DME Refrigerant blend as a new solution to limit global warming potential" (PDF). 14 March 2012. Archived from the original (PDF) on 14 March 2012.
  60. ^ a b IPCC_AR6_WG1_Ch7 2021, 7SM-26
  61. ^ LearnMetrics (12 May 2023). "List of Low GWP Refrigerants: 69 Refrigerants Below 500 GWP". LearnMetrics. Archived from the original on 10 June 2023. Retrieved 13 September 2023.
  62. ^ a b c "Global warming potential (GWP) of HFC refrigerants". iifiir.org. Archived from the original on 24 September 2023. Retrieved 13 September 2023.
  63. ^ Everitt, Neil (15 September 2023). "Qvantum plant has 1 million heat pump capacity". Cooling Post. Archived from the original on 24 September 2023. Retrieved 17 September 2023.
  64. ^ Miara, Marek (22 October 2019). "Heat Pumps with Climate-Friendly Refrigerant Developed for Indoor Installation". Fraunhofer ISE. Archived from the original on 20 February 2022. Retrieved 21 February 2022.
  65. ^ "Refrigerant Safety - About Refrigerant Safety, Toxicity and Flammability". Checkmark. Retrieved 17 April 2024.
  66. ^ "A2L – Mildly Flammable Refrigerants". ACR Journal. 1 September 2015. Retrieved 17 April 2024.
  67. ^ US Environmental Protection Agency, OAR (14 November 2014). "Phaseout of Ozone-Depleting Substances (ODS)". US EPA. Archived from the original on 24 September 2015. Retrieved 16 February 2020.
  68. ^ "Heat Pumps - Energy System". IEA. Retrieved 19 February 2024.
  69. ^ "An Evaluation of Air Source Heat Pump Technology in Yukon" (PDF). Government of Yukon's Energy Solution Centre and Yukon Energy, Mines and Resources. 31 May 2013. Retrieved 15 October 2014.
  70. ^ "The added value of heatpumps for grid stability via demand response". HPT - Heat Pumping Technologies. Retrieved 15 September 2023.
  71. ^ "How heat pumps can keep homes warm without frying the power grid". eng.ox.ac.uk. Retrieved 15 September 2023.
  72. ^ Li, Yuanyuan; Rosengarten, Gary; Stanley, Cameron; Mojiri, Ahmad (10 December 2022). "Electrification of residential heating, cooling and hot water: Load smoothing using onsite photovoltaics, heat pump and thermal batteries". Journal of Energy Storage. 56: 105873. Bibcode:2022JEnSt..5605873L. doi:10.1016/j.est.2022.105873. ISSN 2352-152X. S2CID 253858807.
  73. ^ Olympios, Andreas V.; Hoseinpoori, Pooya; Markides, Christos N. (14 February 2024). "Toward optimal designs of domestic air-to-water heat pumps for a net-zero carbon energy system in the UK". Cell Reports Sustainability. 1 (2): 100021. doi:10.1016/j.crsus.2024.100021. ISSN 2949-7906.
  74. ^ a b "How Much Does Heat Pump Installation Cost? (2023 Guide)". ASHI. Retrieved 30 September 2023.
  75. ^ Chung, E. (26 September 2023). "Will switching to a heat pump save you money? Here's how to find out". CBC/Radio-Canada. Retrieved 20 January 2024.
  76. ^ "Heat pumps vs. AC — Why Upfront Costs Can Be Misleading". carbonswitch.com. Retrieved 30 September 2023.
  77. ^ a b c "Global heat pump sales continue double-digit growth – Analysis". IEA. 31 March 2023. Retrieved 15 September 2023.
  78. ^ Rosenow, Jan; Gibb, Duncan; Nowak, Thomas; Lowes, Richard (October 2022). "Heating up the global heat pump market". Nature Energy. 7 (10): 901–904. Bibcode:2022NatEn...7..901R. doi:10.1038/s41560-022-01104-8. ISSN 2058-7546. S2CID 252141783.
  79. ^ "Source: Heat Pump Association". Heat Pumps. Retrieved 14 June 2024.
  80. ^ "A Heat Pump Might Be Right for Your Home. Here's Everything to Know". The New York Times. 6 June 2023. ISSN 0362-4331. Retrieved 18 September 2023.
  81. ^ "AIR SOURCE HEAT PUMP MAINTENANCE TIPS" (PDF). New York State Clean Heat.
  82. ^ "AIR SOURCE HEAT PUMPS. MAINTENANCE CONSIDERATIONS FOR HOMES" (PDF). Save on Energy. Independent Electricity System Operator.
  83. ^ "YOUR GUIDE TO Air-Source Heat Pumps" (PDF). Clean Energy Lives Here. Massachusetts Clean Energy Center.
  84. ^ "Heating, Ventilation and Air Conditioning. What Kind of HVAC System You Have and How to Use It" (PDF). Energy Saving Recipe. Southface Energy Institute.
  85. ^ "HEAT PUMP BEST PRACTICES. INSTALLATION GUIDE FOR EXISTING HOMES" (PDF). HOME PERFORMANCE STAKEHOLDER COUNCIL | HEAT PUMP BEST PRACTICES GUIDE. 2019.
  86. ^ Milev, George; Al-Habaibeh, Amin; Fanshawe, Simon; Luke Siena, Francesco (1 December 2023). "Investigating the effect of the defrost cycles of air-source heat pumps on their electricity demand in residential buildings". Energy and Buildings. 300. doi:10.1016/j.enbuild.2023.113656.
  87. ^ Jingdong, Liu; Wei, Wang; Yuying, Sun; Shiming, Deng (April 2018). "Operating performances of a space heating ASHP unit with a foul outdoor coil following a prolonged cooling operationPerformances opérationnelles d'une pompe à chaleur aérothermique pour le chauffage d'espace dont le serpentin extérieur est encrassé suite à une opération de refroidissement prolongée". International Journal of Refrigeration. 88: Pages 614-625. doi:10.1016/j.ijrefrig.2018.01.013.
  88. ^ Nawaz, Kashif; Elatar, Ahmed; Fricke, Brian (31 March 2018). "A Critical Literature Review of Defrost Technologies for Heat Pumps and Refrigeration Systems" (PDF). Energy and Transportation Sciences Division. Oak Ridge National Laboratory. US DEPARTMENT OF ENERGY under contract DE-AC05-00OR22725.
  89. ^ "HEAT PUMP 101: HOW TO TAKE CARE OF YOUR HEAT PUMP" (PDF). Novia Scotia Power.
  90. ^ Johnson, R.K. (September 2013). "Measured Performance of a Low Temperature Air Source Heat Pump" (PDF). The National Renewable Energy Laboratory. On behalf of the U.S. Department of Energy’s Building America Program. Office of Energy Efficiency and Renewable Energy. NREL Contract No. DE-AC36-08GO28308.
  91. ^ Jianhui, Niu; Guoyuan, Ma; Shuxue, Xu (20 January 2020). "Experimental study on the performance of air source heat pump system with multiple parallel outdoor units". Wiley Online Library. International Journal of Energy Research. doi:10.1002/er.5098.
  92. ^ Long, Zhang; Jiankai, Dong; Yiqiang, Jiang; Yang, Yao (15 November 2014). "A novel defrosting method using heat energy dissipated by the compressor of an air source heat pump". Applied Energy. 133: 101–111. doi:10.1016/j.apenergy.2014.07.039.
  93. ^ Higa, Randall; Horwitz, Matt; Buendia, Jose; McHugh, Jon; Haile, James; Heinemeier, Kristin (2024). "Yeah, But It's a Dry Cold: Applicability of Cold Climate Heat Pumps in California" (PDF). Summer Study on Energy Efficiency in Buildings. ACEE.
  94. ^ Mendon, Vrushali; Keene, Kevin; Rosenberg, Sam; Rotondo, Julia; Brambley, Dr. Michael; Young, Jim; Kazmi, Ali Akber; Delgoshaei, Dr. Payam (2024). "Rising Up to the Challenge: Cold Climate Heat Pumps in the Field" (PDF). Summer Study on Energy Efficiency in Buildings. ACEE.
  95. ^ "Which Heat Pump is the Best for Reliability & Efficiency 2023?". www.ecohome.net. Retrieved 18 September 2023.
  96. ^ "Heat Pump vs. Furnace: Which Heat Source Is Right for Your Home?". CNET. Retrieved 18 September 2023.
  97. ^ "Most and Least Reliable Heat Pump Brands". Consumer Reports. 7 April 2023. Retrieved 18 September 2023.
  98. ^ Fusanosuke Kuhara used CO2 gas compressed Cryocooler in 1917. Archived 2022-07-10 at the Wayback Machine 2nd Page numbered 28, right side line 3-6. Fusanosuke Kuhara attached CO2 gas compressed Cryocooler with approx. 6,400kcal/h in his home in 1917. In Japanese: 冷凍機が冷房用として使用されたのは1917年久原房之助が神戸の私邸に約6400kcal/h炭酸ガス圧縮機を取り付け、室内を冷やしたのが最初といわれています。
  99. ^ a b The rediscovery of CO2 Archived 2007-10-07 at the Wayback Machine SHECCO
  100. ^ Natural Working Fluids '98, IIR - Gustav Lorentzen Conference: CiNii Archived 2024-02-27 at the Wayback Machine
  101. ^ Kuwajima, Hiroto (8 September 2023). "Panasonic Amps Up Production of Eco Cute Water Heaters | JAPAN Forward". japan-forward.com. Retrieved 28 May 2024.
  102. ^ "Who Wants to Become a Heat-Pump Billionaire?". The Washington Post.

Sources

[edit]

IPCC reports

[edit]
Retrieved from "https://en.wikipedia.org/w/index.php?title=Air_source_heat_pump&oldid=1258097036"