Heating, ventilation, and air conditioning (HVAC) systems are essential components of modern buildings, providing comfort and maintaining indoor air quality. However, these systems can also be sources of noise pollution if not properly maintained or designed. Typical noise complaints related to HVAC systems often stem from vibrations and mechanical issues that resonate through the building structure, creating disturbances for occupants. In particular, air conditioning units are frequent culprits when it comes to unwanted noise.
One common complaint is the sound of rattling or buzzing emanating from an AC unit. This is often due to loose parts or components within the system vibrating against each other during operation. Additionally, older equipment might generate more noise as wear and tear affect their performance. The whirring of motors and fans can also contribute to a consistent background hum that becomes particularly noticeable in quieter settings.
Another issue arises from ductwork transmitting sound throughout a building. When air moves through ducts at high speeds, it can create whooshing noises that travel into occupied spaces. Dust and debris buildup can reduce efficiency, making HVAC Repair a necessary service Ductwork repair to comply with Energy Information Administration efficiency standards. Poorly insulated ducts exacerbate this problem by allowing vibrations to transfer directly into walls or ceilings.
To address these noise concerns, one effective solution is the use of vibration dampeners in HVAC systems. Vibration dampeners are specialized components designed to absorb and reduce vibrations before they have a chance to propagate through structures. By isolating vibrating parts such as compressors or fan motors from their mounting surfaces, dampeners help minimize the transmission of mechanical energy that leads to noise.
The implementation of vibration dampeners dramatically improves the silence of an AC system by targeting one of the root causes of unwanted sound - mechanical vibration. These devices work by using materials with damping properties that dissipate vibrational energy as heat rather than transferring it further along solid pathways like metal brackets or supports.
Beyond enhancing acoustic comfort for building occupants, reducing HVAC-related noise has additional benefits such as extending equipment lifespan and improving overall system efficiency. By minimizing vibrations, mechanical stress on components is reduced which prevents premature wear and breakdowns.
Moreover, quieter HVAC systems contribute positively toward workplace productivity and residential satisfaction by eliminating distractions caused by persistent machine sounds. A silent environment fosters better concentration levels while also promoting relaxation in living spaces - two aspects crucial for both personal well-being and professional effectiveness.
In conclusion, addressing typical noise complaints associated with heating, ventilation, and cooling systems involves understanding their origins primarily linked with vibrations generated during operation processes within these machines themselves alongside structural factors like inadequate insulation measures around them too! Vibration dampeners provide an efficient solution aimed at mitigating this issue effectively ensuring enhanced quietude alongside longer-lasting machinery functionality ultimately leading toward improved occupant experience whether inside homes offices alike!
Understanding vibration in air conditioning units is crucial for enhancing the comfort and tranquility of indoor environments. Air conditioning systems, while essential for maintaining pleasant temperatures, can sometimes introduce unwanted noise and vibrations that disrupt the serenity of homes and offices. These vibrations often arise from the mechanical operations within the unit, including the compressor, fan motors, and refrigerant flow. Over time, such disturbances can not only become a nuisance but also lead to wear and tear on the equipment itself.
One effective solution to mitigate these issues is the use of vibration dampeners. These devices are designed to absorb and reduce the intensity of vibrations generated by air conditioning units. By implementing vibration dampeners, homeowners and businesses can significantly improve AC silence, leading to quieter operation and an overall more enjoyable atmosphere.
Vibration dampeners work by isolating the source of vibration from its surroundings. Typically made from materials like rubber or neoprene, these dampeners act as buffers between vibrating components and their mounts or support structures. When installed correctly, they absorb much of the energy produced by mechanical movements within an air conditioning unit, preventing it from transferring into floors, walls, or ceilings where it could amplify into audible noises.
The benefits of using vibration dampeners extend beyond mere noise reduction. By minimizing excessive vibrations, these devices help protect structural integrity both within the AC unit itself and in surrounding areas. This protection reduces maintenance needs over time as parts experience less strain due to constant agitation. Consequently, this leads to longer-lasting performance for cooling systems and potentially lower repair costs.
Moreover, improving AC silence with vibration dampeners contributes positively to energy efficiency. Quieter systems often indicate smoother operation without unnecessary friction or resistance among moving parts-conditions that typically translate into more efficient energy consumption patterns.
In conclusion, understanding how vibration affects air conditioning units sheds light on why solutions like vibration dampeners are invaluable additions for modern HVAC systems.
Air conditioning systems are essential for maintaining comfortable indoor environments, especially during hot weather. However, these systems can sometimes produce unwelcome noise, which may stem from vibrations within the unit. Understanding how these vibrations occur and contribute to noise problems is crucial in addressing the issue effectively.
Vibrations in air conditioning (AC) systems primarily originate from the mechanical components that operate during their functioning. The compressor, fans, and motors are key contributors to these vibrations. When an AC unit is running, its compressor pumps refrigerant through the system under high pressure. This action creates a pulsating effect that can lead to oscillations in various parts of the unit. Similarly, fans circulate air across evaporator and condenser coils; if they become unbalanced or misaligned, they can generate significant vibration. Motors powering these components also play a part; any imbalance or wear over time can exacerbate vibrational disturbances.
These vibrations transfer through the structure of the AC unit and into surrounding surfaces such as walls, floors, or ceilings. As a result, they manifest as audible noise-ranging from low hums to more intrusive rattles-that can disrupt household peace or office tranquility. In some cases, prolonged exposure to this noise might even cause stress or discomfort among occupants.
To mitigate these noise issues caused by vibrations, vibration dampeners serve as an effective solution. Vibration dampeners are materials or devices designed specifically to absorb and dissipate vibrational energy before it propagates into unwanted sound waves. By strategically placing dampeners at critical points within an AC system-such as around compressors or fan assemblies-they help reduce movement transmission significantly.
The science behind vibration dampeners lies in their ability to convert kinetic energy (from vibrations) into a less harmful form like heat through deformation processes within their structure. Materials like rubber compounds are commonly used due to their elasticity and damping properties that absorb shock efficiently without compromising structural integrity.
Implementing vibration dampeners not only improves acoustic comfort but also enhances overall system longevity by minimizing mechanical stress on components caused by excessive movements over time. With reduced operational noise levels achieved through effective damping solutions residents enjoy quieter environments while maintaining optimal cooling performance from their AC units-a perfect blend of comfort meets efficiency!
In conclusion: understanding how vibrations occur within air conditioning systems provides insight into tackling related noise problems efficiently using vibration dampening techniques!
Air conditioners are a staple in modern homes and offices, providing much-needed relief from oppressive heat. However, the whirring and humming noises they produce can be disruptive. Vibration dampeners play a pivotal role in mitigating these sounds, thereby improving the overall comfort of indoor environments.
At its core, an air conditioning unit functions through a series of mechanical operations that involve compressing refrigerants and circulating air. These processes inevitably generate vibrations which, if left unchecked, can lead to significant noise pollution. Here is where vibration dampeners come into play: designed specifically to absorb and reduce these vibrations before they manifest as audible sound.
Vibration dampeners work by isolating the source of vibration from the surrounding environment. Typically made from rubber or other resilient materials, these devices are strategically placed at key points within the AC system-such as around compressors or fans-to act as a buffer between vibrating components and their mounting surfaces. By absorbing energy from these movements, dampeners effectively diminish the intensity of vibrations transmitted throughout the unit's structure.
The benefits extend beyond mere noise reduction. Reducing vibrations also contributes to prolonging the lifespan of an air conditioning system. Constant vibrations can cause wear and tear on components over time, leading to maintenance issues or even premature failure. By minimizing this mechanical stress with vibration dampeners, there is less risk of damage and a subsequent decrease in repair costs.
Moreover, quieter operation enhances user experience significantly. Whether in residential settings where peace and quiet are valued for relaxation or in office environments where concentration is paramount, reduced noise levels contribute substantially to comfort and productivity.
In addition to structural improvements within individual units, advancements in vibration-dampening technology have led manufacturers to design next-generation models with enhanced silencers that incorporate sophisticated damping mechanisms directly into their construction process.
To conclude, while often overlooked during discussions about air conditioning efficiency or performance upgrades, vibration dampeners deserve recognition for their essential role in improving AC silence. Their ability not only reduces unwanted noise but also extends equipment longevity-making them invaluable assets both economically and environmentally for any space reliant on effective climate control solutions.
Vibration dampeners play a crucial role in improving the silence of air conditioning (AC) units by effectively reducing noise levels. These devices are designed to mitigate the vibrations produced by mechanical components within the AC system, which can otherwise lead to significant noise pollution. Understanding both the definition and purpose of vibration dampeners provides insight into their importance in enhancing indoor comfort and maintaining a peaceful environment.
At its core, a vibration dampener is a device or material used to absorb and reduce the energy generated by vibrations. In the context of air conditioning systems, these vibrations typically originate from moving parts such as compressors, fans, and motors. When these components operate, they generate vibrations that can travel through the structure of the unit and into surrounding areas, causing audible noise. This not only disrupts comfort but can also be quite intrusive in spaces requiring quietness like offices, bedrooms, or study rooms.
The primary purpose of vibration dampeners is to intercept these vibrations before they have an opportunity to propagate further. By doing so, they minimize the transfer of vibrational energy from one component to another or from the AC unit to its mounting surface. This reduction in energy transfer directly translates into lower noise levels emitted by the system.
There are various types of vibration dampeners utilized in AC systems. Commonly used materials include rubber pads, springs, or specialized isolators that serve as buffers between vibrating parts and their mounts. Each type offers different degrees of damping capabilities depending on factors such as frequency range and amplitude of vibrations encountered in specific applications.
Implementing effective vibration control strategies using dampeners results in numerous benefits beyond mere noise reduction. For instance, minimizing excessive vibrations contributes to prolonging equipment lifespan since it reduces wear and tear on mechanical components over time. Additionally improved acoustics create more pleasant environments conducive for concentration relaxation productivity without constant disruption background hums buzzing sounds commonly associated with running air conditioners
Furthermore embracing innovations related technologies continues optimize performance efficiency modern-day HVAC systems ensuring quieter operation overall satisfaction end-users Whether through advancements material science engineering designs manufacturers consistently strive develop solutions meet evolving needs consumers seeking peace mind alongside optimal functionality
In conclusion incorporating strategically placed quality-designed appropriate selection usage tailored requirements essential achieving desired outcomes when aiming enhance tranquility offered by cooling appliances Vibration dampening techniques stand testament human ingenuity addressing challenges posed conventional machinery thereby fostering harmonious coexistence technology everyday life
Vibration dampeners play a crucial role in the realm of HVAC systems, particularly in enhancing the operational silence of air conditioning units. These devices are designed to reduce or eliminate the vibrations that naturally occur when machinery operates. In an air conditioning system, vibrations can lead to noise pollution, decreased efficiency, and even long-term damage to equipment if not properly managed. By integrating vibration dampeners, these adverse effects can be mitigated, leading to quieter and more efficient operation.
There are several types of vibration dampeners commonly used in HVAC systems, each with its unique properties and applications. Rubber mounts are one of the most prevalent types due to their simplicity and effectiveness. Made from elastomeric materials, rubber mounts absorb vibrations by providing a cushion between moving parts and their supporting structures. This type is particularly useful for small to medium-sized air conditioning units where moderate levels of vibration need control.
Spring isolators are another variety frequently employed in larger HVAC installations. These devices use coiled springs to counteract vibrations by allowing controlled movement while absorbing kinetic energy generated by mechanical operations. Spring isolators are highly effective for heavy-duty equipment where significant vibrational forces might be present due to large compressors or fans.
For environments requiring precise vibration control, such as laboratories or hospitals, neoprene pads offer an ideal solution. Made from synthetic rubber known for its durability and resistance to environmental factors like temperature changes and chemicals, neoprene pads provide excellent damping capabilities across various frequencies of vibration.
Additionally, viscous dampers bring a sophisticated approach by utilizing fluid dynamics principles. They contain a viscous fluid within a sealed chamber; as components move against each other inside this chamber during operation, the fluid dissipates vibrational energy through shear action. Viscous dampers are especially beneficial in settings that demand high precision in controlling both amplitude and frequency variations.
Implementing these different types of vibration dampeners significantly contributes towards improving AC silence-a factor increasingly valued in residential areas as well as commercial establishments seeking comfort without compromising performance quality or experiencing premature wear on valuable assets caused by unchecked mechanical disturbances over time.
In conclusion, choosing appropriate vibration dampening solutions tailored specifically according to individual requirements ensures optimal functionality alongside enhanced auditory comfort provided by quieter environments facilitated through effectively reduced intrusive sound emissions produced inherently within active cooling mechanisms integral throughout modern-day life-supporting infrastructures essential worldwide today!
Vibration dampeners play a crucial role in enhancing the performance and comfort of air conditioning systems by significantly reducing the noise they produce. The constant hum or rattle from an AC unit can be not only distracting but also indicative of inefficiencies that could lead to wear and tear over time. To address this, engineers have turned their attention to exploring various materials and designs that can effectively dampen these vibrations, creating quieter and more efficient air conditioning systems.
One of the primary materials used for vibration dampening is rubber. Its inherent flexibility and ability to absorb shocks make it an ideal candidate for mitigating vibrations. Rubber pads are commonly placed under AC units to isolate them from the surfaces on which they rest, preventing the transfer of vibrations to walls or floors. This simple yet effective solution capitalizes on rubber's natural properties to transform kinetic energy into heat, thereby minimizing sound production.
Another innovative material employed in vibration dampening is viscoelastic polymers. These advanced materials possess both viscous and elastic characteristics, meaning they can deform under stress and return to their original shape without permanent deformation.
A central heating system provides warmth to a number of spaces within a building from one main source of heat.
A central heating system has a furnace that converts fuel or electricity to heat through processes. The heat is circulated through the building either by fans forcing heated air through ducts, circulation of low-pressure steam to radiators in each heated room, or pumps that circulate hot water through room radiators. Primary energy sources may be fuels like coal or wood, oil, kerosene, natural gas, or electricity.
Compared with systems such as fireplaces and wood stoves, a central heating plant offers improved uniformity of temperature control over a building, usually including automatic control of the furnace. Large homes or buildings may be divided into individually controllable zones with their own temperature controls. Automatic fuel (and sometimes ash) handling provides improved convenience over separate fireplaces. Where a system includes ducts for air circulation, central air conditioning can be added to the system. A central heating system may take up considerable space in a home or other building, and may require supply and return ductwork to be installed at the time of construction.
Central heating differs from space heating in that the heat generation occurs in one place, such as a furnace room or basement in a house or a mechanical room in a large building (though not necessarily at the geometrically "central" point). The heat is distributed throughout the building, typically by forced-air through ductwork, by water circulating through pipes, or by steam fed through pipes. The most common method of heat generation involves the combustion of fossil fuel in a furnace or boiler.
In much of the temperate climate zone, most detached housing has had central heating installed since before the Second World War. Where coal was readily available (i.e. the anthracite coal region in northeast Pennsylvania in the United States) coal-fired steam or hot water systems were common. Later in the 20th century, these were updated to burn fuel oil or gas, eliminating the need for a large coal storage bin near the boiler and the need to remove and discard coal ashes.
A cheaper alternative to hot water or steam heat is forced hot air. A furnace burns fuel oil or gas, which heats air in a heat exchanger, and blower fans circulate the warmed air through a network of ducts to the rooms in the building. This system is cheaper because the air moves through a series of ducts instead of pipes, and does not require a pipe fitter to install. The space between floor joists can be boxed in and used as some of the ductwork, further lowering costs.
Electrical heating systems occur less commonly and are practical only with low-cost electricity or when ground source heat pumps are used. Considering the combined system of thermal power station and electric resistance heating, the overall efficiency will be less than for direct use of fossil fuel for space heating.[1]
Some other buildings utilize central solar heating, in which case the distribution system normally uses water circulation.
Alternatives to such systems are gas heaters and district heating. District heating uses the waste heat from an industrial process or electrical generating plant to provide heat for neighboring buildings. Similar to cogeneration, this requires underground piping to circulate hot water or steam.
Use of the ondol has been found at archaeological sites in present-day North Korea. A Neolithic Age archaeological site, circa 5000 BC, discovered in Sonbong, Rason, in present-day North Korea, shows a clear vestige of gudeul in the excavated dwelling (Korean: 움집).
The main components of the traditional ondol are an agungi (firebox or stove) accessible from an adjoining room (typically kitchen or master bedroom), a raised masonry floor underlain by horizontal smoke passages, and a vertical, freestanding chimney on the opposite exterior wall providing a draft. The heated floor, supported by stone piers or baffles to distribute the smoke, is covered by stone slabs, clay and an impervious layer such as oiled paper.
Early ondols began as gudeul that provided the heating for a home and for cooking. When a fire was lit in the furnace to cook rice for dinner, the flame would extend horizontally because the flue entry was beside the furnace. This arrangement was essential, as it would not allow the smoke to travel upward, which would cause the flame to go out too soon. As the flame would pass through the flue entrance, it would be guided through the network of passages with the smoke. Entire rooms would be built on the furnace flue to create ondol floored rooms.[2]
Ondol had traditionally been used as a living space for sitting, eating, sleeping and other pastimes in most Korean homes before the 1960s. Koreans are accustomed to sitting and sleeping on the floor, and working and eating at low tables instead of raised tables with chairs.[3] The furnace burned mainly rice paddy straws, agricultural crop waste, biomass or any kind of dried firewood. For short-term cooking, rice paddy straws or crop waste was preferred, while long hours of cooking and floor heating needed longer-burning firewood. Unlike modern-day water heaters, the fuel was either sporadically or regularly burned (two to five times a day), depending on frequency of cooking and seasonal weather conditions.
The ancient Greeks originally developed central heating. The temple of Ephesus was heated by flues planted in the ground and circulating the heat which was generated by fire. Some buildings in the Roman Empire used central heating systems, conducting air heated by furnaces through empty spaces under the floors and out of pipes (called caliducts)[4] in the walls—a system known as a hypocaust.[5][6]
The Roman hypocaust continued to be used on a smaller scale during late Antiquity and by the Umayyad caliphate, while later Muslim builders employed a simpler system of underfloor pipes.[7]
After the collapse of the Roman Empire, overwhelmingly across Europe, heating reverted to more primitive fireplaces for almost a thousand years.
In the early medieval Alpine upland, a simpler central heating system where heat travelled through underfloor channels from the furnace room replaced the Roman hypocaust at some places. In Reichenau Abbey a network of interconnected underfloor channels heated the 300 m2 large assembly room of the monks during the winter months. The degree of efficiency of the system has been calculated at 90%.[8]
In the 13th century, the Cistercian monks revived central heating in Christian Europe using river diversions combined with indoor wood-fired furnaces. The well-preserved Royal Monastery of Our Lady of the Wheel (founded 1202) on the Ebro River in the Aragon region of Spain provides an excellent example of such an application.
The three main methods of central heating were developed in the late 18th to mid-19th centuries.[9]
William Strutt designed a new mill building in Derby with a central hot air furnace in 1793, although the idea had been already proposed by John Evelyn almost a hundred years earlier. Strutt's design consisted of a large stove that heated air brought from the outside by a large underground passage. The air was ventilated through the building by large central ducts.
In 1807, he collaborated with another eminent engineer, Charles Sylvester, on the construction of a new building to house Derby's Royal Infirmary. Sylvester was instrumental in applying Strutt's novel heating system for the new hospital. He published his ideas in The Philosophy of Domestic Economy; as exemplified in the mode of Warming, Ventilating, Washing, Drying, & Cooking, ... in the Derbyshire General Infirmary in 1819. Sylvester documented the new ways of heating hospitals that were included in the design, and the healthier features such as self-cleaning and air-refreshing toilets.[10] The infirmary's novel heating system allowed the patients to breathe fresh heated air whilst old air was channeled up to a glass and iron dome at the centre.[11]
Their designs proved very influential. They were widely copied in the new mills of the Midlands and were constantly improved, reaching maturity with the work of de Chabannes on the ventilation of the House of Commons in the 1810s. This system remained the standard for heating small buildings for the rest of the century.
The English writer Hugh Plat proposed a steam-based central heating system for a greenhouse in 1594, although this was an isolated occurrence and was not followed up until the 18th century. Colonel Coke devised a system of pipes that would carry steam around the house from a central boiler, but it was James Watt the Scottish inventor who was the first to build a working system in his house.[12]
A central boiler supplied high-pressure steam that then distributed the heat within the building through a system of pipes embedded in the columns. He[clarification needed] implemented the system on a much larger scale at a textile factory in Manchester. Robertson Buchanan wrote the definitive description of these installations in his treatises published in 1807 and 1815. Thomas Tredgold's work Principles of Warming and Ventilating Public Buildings, delineated the method of the application of hot steam heating to smaller, non-industrial buildings. This method had superseded the hot air systems by the late 19th century.
Early hot water systems were used in Ancient Rome for heating the Thermæ.[13] Another early hot water system was developed in Russia for central heating of the Summer Palace (1710–1714) of Peter the Great in Saint Petersburg. Slightly later, in 1716, came the first use of water in Sweden to distribute heating in buildings. Mårten Triewald, a Swedish engineer, used this method for a greenhouse at Newcastle upon Tyne. Jean Simon Bonnemain (1743–1830), a French architect,[14] introduced the technique to industry on a cooperative, at Château du Pêcq, near Paris.
However, these scattered attempts were isolated and mainly confined in their application to greenhouses. Tredgold originally dismissed its use as impractical, but changed his mind in 1836, when the technology went into a phase of rapid development.[15]
Early systems had used low pressure water systems, which required very large pipes. One of the first modern hot water central heating systems to remedy this deficiency was installed by Angier March Perkins in London in the 1830s. At that time central heating was coming into fashion in Britain, with steam or hot air systems generally being used.
Perkins' 1832 apparatus distributed water at 200 degrees Celsius (392 °F) through small diameter pipes at high pressure. A crucial invention to make the system viable was the thread screwed joint, that allowed the joint between the pipes to bear a similar pressure to the pipe itself. He also separated the boiler from the heat source to reduce the risk of explosion. The first unit was installed in the home of Governor of the Bank of England John Horsley Palmer so that he could grow grapes in England's cold climate.[16]
His systems were installed in factories and churches across the country, many of them remaining in usable condition for over 150 years. His system was also adapted for use by bakers in the heating of their ovens and in the making of paper from wood pulp.
Franz San Galli, a Prussian-born Russian businessman living in St. Petersburg, invented the radiator between 1855 and 1857, which was a major step in the final shaping of modern central heating.[17][18] The Victorian cast iron radiator became widespread by the end of the 19th century as companies, such as the American Radiator Company, expanded the market for low cost radiators in the US and Europe.
The energy source selected for a central heating system varies by region. The primary energy source is selected on the basis of cost, convenience, efficiency and reliability. The energy cost of heating is one of the main costs of operating a building in a cold climate. Some central heating plants can switch fuels for reasons of economy and convenience; for example, a home owner may install a wood-fired furnace with electrical backup for occasional unattended operation.
Solid fuels such as wood, peat or coal can be stockpiled at the point of use, but are inconvenient to handle and difficult to automatically control. Wood fuel is still used where the supply is plentiful and the occupants of the building don't mind the work involved in hauling in fuel, removing ashes, and tending the fire. Pellet fuel systems can automatically stoke the fire, but still need manual removal of ash. Coal was once an important residential heating fuel but today is uncommon, and smokeless fuel is preferred as a substitute in open fireplaces or stoves.
Liquid fuels are petroleum products such as heating oil and kerosene. These are still widely applied where other heat sources are unavailable. Fuel oil can be automatically fired in a central heating system and requires no ash removal and little maintenance of the combustion system. However, the variable price of oil on world markets leads to erratic and high prices compared to some other energy sources. Institutional heating systems (office buildings or schools, for example) can use low-grade, inexpensive bunker fuel to run their heating plants, but capital cost is high compared to more easily managed liquid fuels.
Natural gas is a widespread heating fuel in North America and northern Europe. Gas burners are automatically controlled and require no ash removal and little maintenance. However, not all areas have access to a natural gas distribution system. Liquefied petroleum gas or propane can be stored at the point of use and periodically replenished by a truck-mounted mobile tank.
Some areas have low cost electric power, making electric heating economically practical. Electric heating can either be purely resistance-type heating or make use of a heat pump system to take advantage of low-grade heat in the air or ground.
A district heating system uses centrally located boilers or water heaters and circulates heat energy to individual customers by circulating hot water or steam. This has the advantage of a central highly efficient energy converter that can use the best available pollution controls, and that is professionally operated. The district heating system can use heat sources impractical to deploy to individual homes, such as heavy oil, wood byproducts, or nuclear fission. The distribution network is more costly to build than for gas or electric heating, and so is only found in densely populated areas or compact communities.
Not all central heating systems require purchased energy. A few buildings are served by local geothermal heat, using hot water or steam from a local well to provide building heat. Such areas are uncommon. A passive solar system requires no purchased fuel but needs to be carefully designed for the site.
Heater outputs are measured in kilowatts or BTUs per hour. For placement in a house, the heater, and the level of output required for the house, needs to be calculated. This calculation is achieved by recording a variety of factors – namely, what is above and below the room you wish to heat, how many windows there are, the type of external walls in the property and a variety of other factors that will determine the level of heat output that is required to adequately heat the space. This calculation is called a heat loss calculation and can be done with a BTU Calculator. Depending on the outcome of this calculation, the heater can be exactly matched to the house.[19][20][21]
Heat output can be measured by heat cost allocators, so that each unit can be individually billed even though there is only one centralized system.
Circulating hot water can be used for central heating. Sometimes these systems are called hydronic heating systems.[22]
Common components of a central heating system using water-circulation include:
The circulating water systems use a closed loop; the same water is heated and then reheated. A sealed system provides a form of central heating in which the water used for heating circulates independently of the building's normal water supply.
An expansion tank contains compressed gas, separated from the sealed-system water by a diaphragm. This allows for normal variations of pressure in the system. A safety valve allows water to escape from the system when pressure becomes too high, and a valve can open to replenish water from the normal water supply if the pressure drops too low. Sealed systems offer an alternative to open-vent systems, in which steam can escape from the system, and gets replaced from the building's water supply via a feed and central storage system.
Heating systems in the United Kingdom and in other parts of Europe commonly combine the needs of space heating with domestic hot-water heating. These systems occur less commonly in the USA. In this case, the heated water in a sealed system flows through a heat exchanger in a hot-water tank or hot-water cylinder where it heats water from the regular potable water supply for use at hot-water taps or appliances such as washing machines or dishwashers.
Hydronic radiant floor heating systems use a boiler or district heating to heat water and a pump to circulate the hot water in plastic pipes installed in a concrete slab. The pipes, embedded in the floor, carry heated water that conducts warmth to the surface of the floor, where it broadcasts heat energy to the room above. Hydronic heating systems are also used with antifreeze solutions in ice and snow melt systems for walkways, parking lots and streets. They are more commonly used in commercial and whole house radiant floor heat projects, whereas electric radiant heat systems are more commonly used in smaller "spot warming" applications.
A steam heating system takes advantage of the high latent heat which is given off when steam condenses to liquid water. In a steam heating system, each room is equipped with a radiator which is connected to a source of low-pressure steam (a boiler). Steam entering the radiator condenses and gives up its latent heat, returning to liquid water. The radiator in turn heats the air of the room, and provides some direct radiant heat. The condensate water returns to the boiler either by gravity or with the assistance of a pump. Some systems use only a single pipe for combined steam and condensate return. Since trapped air prevents proper circulation, such systems have vent valves to allow air to be purged. In domestic and small commercial buildings, the steam is generated at relatively low gauge pressure, less than 15 psi (100 kPa).[citation needed]
Steam heating systems are rarely installed in new single-family residential construction owing to the cost of the piping installation. Pipes must be carefully sloped to prevent trapped condensate blockage. Compared to other methods of heating, it is more difficult to control the output of a steam system. However, steam can be sent, for example, between buildings on a campus to allow use of an efficient central boiler and low cost fuel. Tall buildings take advantage of the low density of steam to avoid the excessive pressure required to circulate hot water from a basement-mounted boiler. In industrial systems, process steam used for power generation or other purposes can also be tapped for space heating. Steam for heating systems may also be obtained from heat recovery boilers using otherwise wasted heat from industrial processes.[23]
Electric heating or resistance heating converts electricity directly to heat. Electric heat is often more expensive than heat produced by combustion appliances like natural gas, propane, and oil. Electric resistance heat can be provided by baseboard heaters, space heaters, radiant heaters, furnaces, wall heaters, or thermal storage systems.
Electric heaters are usually part of a fan coil which is part of a central air conditioner. They circulate heat by blowing air across the heating element which is supplied to the furnace through return air ducts. Blowers in electric furnaces move air over one to five resistance coils or elements which are usually rated at five kilowatts. The heating elements activate one at a time to avoid overloading the electrical system. Overheating is prevented by a safety switch called a limit controller or limit switch. This limit controller may shut the furnace off if the blower fails or if something is blocking the air flow. The heated air is then sent back through the home through supply ducts.
In larger commercial applications, central heating is provided through an air handler which incorporates similar components as a furnace but on a larger scale.
A data furnace uses computers to convert electricity into heat while simultaneously processing data.
An air source heat pump can be used to air condition the building during hot weather, and to warm the building using heat extracted from outdoor air in cold weather. Air-source heat pumps are generally uneconomic for outdoor temperatures much below freezing. In colder climates, geothermal heat pumps can be used to extract heat from the ground. For economy, these systems are designed for average low winter temperatures and use supplemental heating for extreme low temperature conditions. The advantage of the heat pump is that it reduces the purchased energy required for building heating; often geothermal source systems also supply domestic hot water. Even in places where fossil fuels provide most electricity, a geothermal system may offset greenhouse gas production since most of the heat is supplied from the surrounding environment, with only 15–30% as electrical consumption.[24]
Public and commercial properties are directly and indirectly responsible for 30% of the final energy consumed around the world, including almost 55% of global electricity consumption.[25] Heating is currently responsible for around 45% of building emissions, and still relying on fossil fuels for supplying more than 55% of its final energy consumption.[25]
Around 4.3 Gt of CO2 were released to the atmosphere in 2019 for heating in buildings when accounting for emissions from direct fossil fuel combustion as well as from upstream electricity and heat generation. This represents nearly 12% of global energy and process-related CO2 emissions.[25]
From an energy-efficiency standpoint considerable heat gets lost or goes to waste if only a single room needs heating, since central heating has distribution losses and (in the case of forced-air systems particularly) may heat some unoccupied rooms without need. In such buildings which require isolated heating, one may wish to consider non-central systems such as individual room heaters, fireplaces or other devices. Alternatively, architects can design new buildings which can virtually eliminate the need for heating, such as those built to the Passive House standard.
However, if a building does need full heating, combustion central heating may offer a more environmentally friendly solution than electric resistance heating. This applies when electricity originates from a fossil fuel power station, with up to 60% of the energy in the fuel lost (unless utilized for district heating) and about 6% in transmission losses. In Sweden proposals exist to phase out direct electric heating for this reason (see oil phase-out in Sweden). Nuclear, wind, solar and hydroelectric sources reduce this factor.
In contrast, hot-water central heating systems can use water heated in or close to the building using high-efficiency condensing boilers, biofuels, or district heating. Wet underfloor heating has proven ideal. This offers the option of relatively easy conversion in the future to use developing technologies such as heat pumps and solar combisystems, thereby also providing future-proofing.
Typical efficiencies for central heating (measured at the customer's purchase of energy) are:
Oil storage tanks, especially underground storage tanks, can also impact the environment. Even if a building's heating system was converted from oil long ago, oil may still be impacting the environment by contaminating soil and groundwater. Building owners can find themselves liable to remove buried tanks and the remediation costs.
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A heat pump is a device that uses electricity to transfer heat from a colder place to a warmer place. Specifically, the heat pump transfers thermal energy using a heat pump and refrigeration cycle, cooling the cool space and warming the warm space.[1] In winter a heat pump can move heat from the cool outdoors to warm a house; the pump may also be designed to move heat from the house to the warmer outdoors in summer. As they transfer heat rather than generating heat, they are more energy-efficient than heating by gas boiler.[2]
A gaseous refrigerant is compressed so its pressure and temperature rise. When operating as a heater in cold weather, the warmed gas flows to a heat exchanger in the indoor space where some of its thermal energy is transferred to that indoor space, causing the gas to condense into a liquid. The liquified refrigerant flows to a heat exchanger in the outdoor space where the pressure falls, the liquid evaporates and the temperature of the gas falls. It is now colder than the temperature of the outdoor space being used as a heat source. It can again take up energy from the heat source, be compressed and repeat the cycle.
Air source heat pumps are the most common models, while other types include ground source heat pumps, water source heat pumps and exhaust air heat pumps.[3] Large-scale heat pumps are also used in district heating systems.[4]
The efficiency of a heat pump is expressed as a coefficient of performance (COP), or seasonal coefficient of performance (SCOP). The higher the number, the more efficient a heat pump is. For example, an air-to-water heat pump that produces 6kW at a SCOP of 4.62 will give over 4kW of energy into a heating system for every kilowatt of energy that the heat pump uses itself to operate. When used for space heating, heat pumps are typically more energy-efficient than electric resistance and other heaters.
Because of their high efficiency and the increasing share of fossil-free sources in electrical grids, heat pumps are playing a role in climate change mitigation.[5][6] Consuming 1 kWh of electricity, they can transfer 1[7] to 4.5 kWh of thermal energy into a building. The carbon footprint of heat pumps depends on how electricity is generated, but they usually reduce emissions.[8] Heat pumps could satisfy over 80% of global space and water heating needs with a lower carbon footprint than gas-fired condensing boilers: however, in 2021 they only met 10%.[4]
Heat flows spontaneously from a region of higher temperature to a region of lower temperature. Heat does not flow spontaneously from lower temperature to higher, but it can be made to flow in this direction if work is performed. The work required to transfer a given amount of heat is usually much less than the amount of heat; this is the motivation for using heat pumps in applications such as the heating of water and the interior of buildings.[9]
The amount of work required to drive an amount of heat Q from a lower-temperature reservoir such as ambient air to a higher-temperature reservoir such as the interior of a building is: where
The coefficient of performance of a heat pump is greater than one so the work required is less than the heat transferred, making a heat pump a more efficient form of heating than electrical resistance heating. As the temperature of the higher-temperature reservoir increases in response to the heat flowing into it, the coefficient of performance decreases, causing an increasing amount of work to be required for each unit of heat being transferred.[9]
The coefficient of performance, and the work required by a heat pump can be calculated easily by considering an ideal heat pump operating on the reversed Carnot cycle:
This is the theoretical amount of heat pumped but in practice it will be less for various reasons, for example if the outside unit has been installed where there is not enough airflow. More data sharing with owners and academics—perhaps from heat meters—could improve efficiency in the long run.[11]
Milestones:
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.[20]
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).[21]
As of 2023[update] 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.[22]
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.[23]
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.[24]
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.[25]A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that use a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through the seasons. Ground-source heat pumps (GSHPs)—or geothermal heat pumps (GHP), as they are commonly termed in North America—are among the most energy-efficient technologies for providing HVAC and water heating, using less energy than can be achieved by use of resistive electric heaters.
Efficiency is given as a coefficient of performance (CoP) which is typically in the range 3-6, meaning that the devices provide 3-6 units of heat for each unit of electricity used. Setup costs are higher than for other heating systems, due to the requirement of installing ground loops over large areas or of drilling bore holes, hence ground source is often installed when new blocks of flats are built.[26] Air-source heat pumps have lower set-up costs.Exhaust air heat pumps extract heat from the exhaust air of a building and require mechanical ventilation. Two classes exist:
A solar-assisted heat pump (SAHP) is a machine that combines a heat pump and thermal solar panels and/or PV solar panels in a single integrated system.[27] Typically these two technologies are used separately (or only placing them in parallel) to produce hot water.[28] In this system the solar thermal panel performs the function of the low temperature heat source and the heat produced is used to feed the heat pump's evaporator.[29] The goal of this system is to get high coefficient of performance (COP) and then produce energy in a more efficient and less expensive way.
It is possible to use any type of solar thermal panel (sheet and tubes, roll-bond, heat pipe, thermal plates) or hybrid (mono/polycrystalline, thin film) in combination with the heat pump. The use of a hybrid panel is preferable because it allows covering a part of the electricity demand of the heat pump and reduce the power consumption and consequently the variable costs of the system.A water-source heat pump works in a similar manner to a ground-source heat pump, except that it takes heat from a body of water rather than the ground. The body of water does, however, need to be large enough to be able to withstand the cooling effect of the unit without freezing or creating an adverse effect for wildlife.[30] The largest water-source heat pump was installed in the Danish town of Esbjerg in 2023.[31][32]
A thermoacoustic heat pump operates as a thermoacoustic heat engine without refrigerant but instead uses a standing wave in a sealed chamber driven by a loudspeaker to achieve a temperature difference across the chamber.[33]
Electrocaloric heat pumps are solid state.[34]
The International Energy Agency estimated that, as of 2021, heat pumps installed in buildings have a combined capacity of more than 1000 GW.[4] They are used for heating, ventilation, and air conditioning (HVAC) and may also provide domestic hot water and tumble clothes drying.[35] The purchase costs are supported in various countries by consumer rebates.[36]
In HVAC applications, a heat pump is typically a vapor-compression refrigeration device that includes a reversing valve and optimized heat exchangers so that the direction of heat flow (thermal energy movement) may be reversed. The reversing valve switches the direction of refrigerant through the cycle and therefore the heat pump may deliver either heating or cooling to a building.
Because the two heat exchangers, the condenser and evaporator, must swap functions, they are optimized to perform adequately in both modes. Therefore, the Seasonal Energy Efficiency Rating (SEER in the US) or European seasonal energy efficiency ratio of a reversible heat pump is typically slightly less than those of two separately optimized machines. For equipment to receive the US Energy Star rating, it must have a rating of at least 14 SEER. Pumps with ratings of 18 SEER or above are considered highly efficient. The highest efficiency heat pumps manufactured are up to 24 SEER.[37]
Heating seasonal performance factor (in the US) or Seasonal Performance Factor (in Europe) are ratings of heating performance. The SPF is Total heat output per annum / Total electricity consumed per annum in other words the average heating COP over the year.[38]
Window mounted heat pumps run on standard 120v AC outlets and provide heating, cooling, and humidity control. They are more efficient with lower noise levels, condensation management, and a smaller footprint than window mounted air conditioners that just do cooling.[39]
In water heating applications, heat pumps may be used to heat or preheat water for swimming pools, homes or industry. Usually heat is extracted from outdoor air and transferred to an indoor water tank.[40][41]
Large (megawatt-scale) heat pumps are used for district heating.[42] However as of 2022[update] about 90% of district heat is from fossil fuels.[43] In Europe, heat pumps account for a mere 1% of heat supply in district heating networks but several countries have targets to decarbonise their networks between 2030 and 2040.[4] Possible sources of heat for such applications are sewage water, ambient water (e.g. sea, lake and river water), industrial waste heat, geothermal energy, flue gas, waste heat from district cooling and heat from solar seasonal thermal energy storage.[44] Large-scale heat pumps for district heating combined with thermal energy storage offer high flexibility for the integration of variable renewable energy. Therefore, they are regarded as a key technology for limiting climate change by phasing out fossil fuels.[44][45] They are also a crucial element of systems which can both heat and cool districts.[46]
There is great potential to reduce the energy consumption and related greenhouse gas emissions in industry by application of industrial heat pumps, for example for process heat.[47][48] Short payback periods of less than 2 years are possible, while achieving a high reduction of CO2 emissions (in some cases more than 50%).[49][50] Industrial heat pumps can heat up to 200 °C, and can meet the heating demands of many light industries.[51][52] In Europe alone, 15 GW of heat pumps could be installed in 3,000 facilities in the paper, food and chemicals industries.[4]
The performance of a heat pump is determined by the ability of the pump to extract heat from a low temperature environment (the source) and deliver it to a higher temperature environment (the sink).[53] Performance varies, depending on installation details, temperature differences, site elevation, location on site, pipe runs, flow rates, and maintenance.
In general, heat pumps work most efficiently (that is, the heat output produced for a given energy input) when the difference between the heat source and the heat sink is small. When using a heat pump for space or water heating, therefore, the heat pump will be most efficient in mild conditions, and decline in efficiency on very cold days. Performance metrics supplied to consumers attempt to take this variation into account.
Common performance metrics are the SEER (in cooling mode) and seasonal coefficient of performance (SCOP) (commonly used just for heating), although SCOP can be used for both modes of operation.[53] Larger values of either metric indicate better performance.[53] When comparing the performance of heat pumps, the term performance is preferred to efficiency, with coefficient of performance (COP) being used to describe the ratio of useful heat movement per work input.[53] An electrical resistance heater has a COP of 1.0, which is considerably lower than a well-designed heat pump which will typically have a COP of 3 to 5 with an external temperature of 10 °C and an internal temperature of 20 °C. Because the ground is a constant temperature source, a ground-source heat pump is not subjected to large temperature fluctuations, and therefore is the most energy-efficient type of heat pump.[53]
The "seasonal coefficient of performance" (SCOP) is a measure of the aggregate energy efficiency measure over a period of one year which is dependent on regional climate.[53] One framework for this calculation is given by the Commission Regulation (EU) No. 813/2013.[54]
A heat pump's operating performance in cooling mode is characterized in the US by either its energy efficiency ratio (EER) or seasonal energy efficiency ratio (SEER), both of which have units of BTU/(h·W) (note that 1 BTU/(h·W) = 0.293 W/W) and larger values indicate better performance.
Pump type and source | Typical use | 35 °C (e.g. heated screed floor) |
45 °C (e.g. heated screed floor) |
55 °C (e.g. heated timber floor) |
65 °C (e.g. radiator or DHW) |
75 °C (e.g. radiator and DHW) |
85 °C (e.g. radiator and DHW) |
---|---|---|---|---|---|---|---|
High-efficiency air-source heat pump (ASHP), air at −20 °C[55] | 2.2 | 2.0 | †| †| †| †| |
Two-stage ASHP, air at −20 °C[56] | Low source temperature | 2.4 | 2.2 | 1.9 | †| †| †|
High-efficiency ASHP, air at 0 °C[55] | Low output temperature | 3.8 | 2.8 | 2.2 | 2.0 | †| †|
Prototype transcritical CO 2 (R744) heat pump with tripartite gas cooler, source at 0 °C[57] |
High output temperature | 3.3 | †| †| 4.2 | †| 3.0 |
Ground-source heat pump (GSHP), water at 0 °C[55] | 5.0 | 3.7 | 2.9 | 2.4 | †| †| |
GSHP, ground at 10 °C[55] | Low output temperature | 7.2 | 5.0 | 3.7 | 2.9 | 2.4 | †|
Theoretical Carnot cycle limit, source −20 °C | 5.6 | 4.9 | 4.4 | 4.0 | 3.7 | 3.4 | |
Theoretical Carnot cycle limit, source 0 °C | 8.8 | 7.1 | 6.0 | 5.2 | 4.6 | 4.2 | |
Theoretical Lorentzen cycle limit (CO 2 pump), return fluid 25 °C, source 0 °C[57] |
10.1 | 8.8 | 7.9 | 7.1 | 6.5 | 6.1 | |
Theoretical Carnot cycle limit, source 10 °C | 12.3 | 9.1 | 7.3 | 6.1 | 5.4 | 4.8 |
The carbon footprint of heat pumps depends on their individual efficiency and how electricity is produced. An increasing share of low-carbon energy sources such as wind and solar will lower the impact on the climate.
heating system | emissions of energy source | efficiency | resulting emissions for thermal energy |
---|---|---|---|
heat pump with onshore wind power | 11 gCO2/kWh[58] | 400% (COP=4) | 3 gCO2/kWh |
heat pump with global electricity mix | 436 gCO2/kWh[59] (2022) | 400% (COP=4) | 109 gCO2/kWh |
natural-gas thermal (high efficiency) | 201 gCO2/kWh[60] | 90%[citation needed] | 223 gCO2/kWh |
heat pump electricity by lignite (old power plant) and low performance |
1221 gCO2/kWh[60] | 300% (COP=3) | 407 gCO2/kWh |
In most settings, heat pumps will reduce CO2 emissions compared to heating systems powered by fossil fuels.[61] In regions accounting for 70% of world energy consumption, the emissions savings of heat pumps compared with a high-efficiency gas boiler are on average above 45% and reach 80% in countries with cleaner electricity mixes.[4] These values can be improved by 10 percentage points, respectively, with alternative refrigerants. In the United States, 70% of houses could reduce emissions by installing a heat pump.[62][4] The rising share of renewable electricity generation in many countries is set to increase the emissions savings from heat pumps over time.[4]
Heating systems powered by green hydrogen are also low-carbon and may become competitors, but are much less efficient due to the energy loss associated with hydrogen conversion, transport and use. In addition, not enough green hydrogen is expected to be available before the 2030s or 2040s.[63][64]
This section needs additional citations for verification. (May 2021)
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Vapor-compression uses a circulating refrigerant as the medium which absorbs heat from one space, compresses it thereby increasing its temperature before releasing it in another space. The system normally has eight main components: a compressor, a reservoir, a reversing valve which selects between heating and cooling mode, two thermal expansion valves (one used when in heating mode and the other when used in cooling mode) and two heat exchangers, one associated with the external heat source/sink and the other with the interior. In heating mode the external heat exchanger is the evaporator and the internal one being the condenser; in cooling mode the roles are reversed.
Circulating refrigerant enters the compressor in the thermodynamic state known as a saturated vapor[65] and is compressed to a higher pressure, resulting in a higher temperature as well. The hot, compressed vapor is then in the thermodynamic state known as a superheated vapor and it is at a temperature and pressure at which it can be condensed with either cooling water or cooling air flowing across the coil or tubes. In heating mode this heat is used to heat the building using the internal heat exchanger, and in cooling mode this heat is rejected via the external heat exchanger.
The condensed, liquid refrigerant, in the thermodynamic state known as a saturated liquid, is next routed through an expansion valve where it undergoes an abrupt reduction in pressure. That pressure reduction results in the adiabatic flash evaporation of a part of the liquid refrigerant. The auto-refrigeration effect of the adiabatic flash evaporation lowers the temperature of the liquid and-vapor refrigerant mixture to where it is colder than the temperature of the enclosed space to be refrigerated.
The cold mixture is then routed through the coil or tubes in the evaporator. A fan circulates the warm air in the enclosed space across the coil or tubes carrying the cold refrigerant liquid and vapor mixture. That warm air evaporates the liquid part of the cold refrigerant mixture. At the same time, the circulating air is cooled and thus lowers the temperature of the enclosed space to the desired temperature. The evaporator is where the circulating refrigerant absorbs and removes heat which is subsequently rejected in the condenser and transferred elsewhere by the water or air used in the condenser.
To complete the refrigeration cycle, the refrigerant vapor from the evaporator is again a saturated vapor and is routed back into the compressor.
Over time, the evaporator may collect ice or water from ambient humidity. The ice is melted through defrosting cycle. An internal heat exchanger is either used to heat/cool the interior air directly or to heat water that is then circulated through radiators or underfloor heating circuit to either heat or cool the buildings.
Heat input can be improved if the refrigerant enters the evaporator with a lower vapor content. This can be achieved by cooling the liquid refrigerant after condensation. The gaseous refrigerant condenses on the heat exchange surface of the condenser. To achieve a heat flow from the gaseous flow center to the wall of the condenser, the temperature of the liquid refrigerant must be lower than the condensation temperature.
Additional subcooling can be achieved by heat exchange between relatively warm liquid refrigerant leaving the condenser and the cooler refrigerant vapor emerging from the evaporator. The enthalpy difference required for the subcooling leads to the superheating of the vapor drawn into the compressor. When the increase in cooling achieved by subcooling is greater that the compressor drive input required to overcome the additional pressure losses, such a heat exchange improves the coefficient of performance.[66]
One disadvantage of the subcooling of liquids is that the difference between the condensing temperature and the heat-sink temperature must be larger. This leads to a moderately high pressure difference between condensing and evaporating pressure, whereby the compressor energy increases.[citation needed]
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)[67]).[68] Their boiling points are usually below −25 °C.[69]
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,[70] as most countries have now ratified the Kigali Amendment to ban HFCs.[71] 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.[72] Propane may be the most suitable for high temperature heat pumps.[73] Ammonia (R717) and carbon dioxide (R-744) also have a low GWP. As of 2023[update] smaller CO
2 heat pumps are not widely available and research and development of them continues.[74] A 2024 report said that refrigerants with GWP are vulnerable to further international restrictions.[75]
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.[76]
Replacements, including R-134a and R-410A, are hydrofluorocarbons (HFC) with similar thermodynamic properties with insignificant ozone depletion potential (ODP) but had problematic GWP.[77] HFCs are powerful greenhouse gases which contribute to climate change.[78][79] Dimethyl ether (DME) also gained in popularity as a refrigerant in combination with R404a.[80] More recent refrigerants include difluoromethane (R32) with a lower GWP, but still over 600.
refrigerant | 20-year GWP | 100-year GWP |
---|---|---|
R-290 propane[81] | 0.072 | 0.02 |
R-600a isobutane | 3[82] | |
R-32[81] | 491 | 136 |
R-410a[83] | 4705 | 2285 |
R-134a[83] | 4060 | 1470 |
R-404a[83] | 7258 | 4808 |
Devices with R-290 refrigerant (propane) are expected to play a key role in the future.[73][84] 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).[85][86][87] 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.[88] 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]
Financial incentives aim to protect consumers from high fossil gas costs and to reduce greenhouse gas emissions,[89] and are currently available in more than 30 countries around the world, covering more than 70% of global heating demand in 2021.[4]
Food processors, brewers, petfood producers and other industrial energy users are exploring whether it is feasible to use renewable energy to produce industrial-grade heat. Process heating accounts for the largest share of onsite energy use in Australian manufacturing, with lower-temperature operations like food production particularly well-suited to transition to renewables.
To help producers understand how they could benefit from making the switch, the Australian Renewable Energy Agency (ARENA) provided funding to the Australian Alliance for Energy Productivity (A2EP) to undertake pre-feasibility studies at a range of sites around Australia, with the most promising locations advancing to full feasibility studies.[90]
In an effort to incentivize energy efficiency and reduce environmental impact, the Australian states of Victoria, New South Wales, and Queensland have implemented rebate programs targeting the upgrade of existing hot water systems. These programs specifically encourage the transition from traditional gas or electric systems to heat pump based systems.[91][92][93][94][95]
In 2022, the Canada Greener Homes Grant[96] provides up to $5000 for upgrades (including certain heat pumps), and $600 for energy efficiency evaluations.
Purchase subsidies in rural areas in the 2010s reduced burning coal for heating, which had been causing ill health.[97]
In the 2024 report by the International Energy Agency (IEA) titled "The Future of Heat Pumps in China," it is highlighted that China, as the world's largest market for heat pumps in buildings, plays a critical role in the global industry. The country accounts for over one-quarter of global sales, with a 12% increase in 2023 alone, despite a global sales dip of 3% the same year.[98]
Heat pumps are now used in approximately 8% of all heating equipment sales for buildings in China as of 2022, and they are increasingly becoming the norm in central and southern regions for both heating and cooling. Despite their higher upfront costs and relatively low awareness, heat pumps are favored for their energy efficiency, consuming three to five times less energy than electric heaters or fossil fuel-based solutions. Currently, decentralized heat pumps installed in Chinese buildings represent a quarter of the global installed capacity, with a total capacity exceeding 250 GW, which covers around 4% of the heating needs in buildings.[98]
Under the Announced Pledges Scenario (APS), which aligns with China's carbon neutrality goals, the capacity is expected to reach 1,400 GW by 2050, meeting 25% of heating needs. This scenario would require an installation of about 100 GW of heat pumps annually until 2050. Furthermore, the heat pump sector in China employs over 300,000 people, with employment numbers expected to double by 2050, underscoring the importance of vocational training for industry growth. This robust development in the heat pump market is set to play a significant role in reducing direct emissions in buildings by 30% and cutting PM2.5 emissions from residential heating by nearly 80% by 2030.[98][99]
To speed up the deployment rate of heat pumps, the European Commission launched the Heat Pump Accelerator Platform in November 2024.[100] It will encourage industry experts, policymakers, and stakeholders to collaborate, share best practices and ideas, and jointly discuss measures that promote sustainable heating solutions.[101]
Until 2027 fixed heat pumps have no Value Added Tax (VAT).[102] As of 2022[update] the installation cost of a heat pump is more than a gas boiler, but with the "Boiler Upgrade Scheme"[103] government grant and assuming electricity/gas costs remain similar their lifetime costs would be similar on average.[104] However lifetime cost relative to a gas boiler varies considerably depending on several factors, such as the quality of the heat pump installation and the tariff used.[105] In 2024 England was criticised for still allowing new homes to be built with gas boilers, unlike some other counties where this is banned.[106]
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This section needs to be updated. The reason given is: talks about 2023 in future tense.(January 2025)
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The High-efficiency Electric Home Rebate Program was created in 2022 to award grants to State energy offices and Indian Tribes in order to establish state-wide high-efficiency electric-home rebates. Effective immediately, American households are eligible for a tax credit to cover the costs of buying and installing a heat pump, up to $2,000. Starting in 2023, low- and moderate-level income households will be eligible for a heat-pump rebate of up to $8,000.[107]
In 2022, more heat pumps were sold in the United States than natural gas furnaces.[108]
In November 2023 Biden's administration allocated 169 million dollars from the Inflation Reduction Act to speed up production of heat pumps. It used the Defense Production Act to do so, because according to the administration, energy that is better for the climate is also better for national security.[109]
Photovoltaic-thermal direct expansion solar assisted heat pump (PV/T-DX-SAHP) system enables to benefit the waste heat for evaporation of refrigerant in PV/T collector-evaporator, while providing better cooling for PV cells (Yao et al., 2020).