How Air Scrubbers Improve AC Performance

How Air Scrubbers Improve AC Performance

Office of Scientific and Technical Information

Common HVAC Issues and Their Impact on AC Performance



Common HVAC issues can significantly impact the performance of air conditioning systems, leading to inefficiencies and increased energy consumption. Understanding these issues is crucial for maintaining a comfortable indoor environment and ensuring that AC units operate at peak efficiency. One innovative solution that has been gaining attention for its ability to enhance AC performance is the integration of air scrubbers into HVAC systems.

Air conditioning systems are complex machines comprised of various components such as filters, coils, and fans, all of which require regular maintenance to function optimally. If your system turns on and off too frequently, HVAC Repair can help regulate performance HVAC installation to ensure your air filter stays clean and effective. Common problems include dirty or clogged filters, refrigerant leaks, malfunctioning thermostats, and blocked vents. Dirty filters restrict airflow, causing the system to work harder than necessary, while refrigerant leaks reduce cooling capacity and efficiency. Malfunctioning thermostats can lead to incorrect temperature readings, resulting in discomfort and wasted energy. Blocked vents impede proper air circulation throughout a building.

These issues not only affect comfort but also contribute to higher utility bills and increased wear on the system, potentially shortening its lifespan. Therefore, addressing common HVAC problems promptly is essential for maintaining efficient operation. However, even with routine maintenance practices in place, enhancing indoor air quality remains a challenge due to pollutants like dust, mold spores, bacteria, and allergens circulating within buildings.



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This is where air scrubbers come into play as an effective solution for improving both indoor air quality and AC performance. Air scrubbers are advanced filtration devices that remove contaminants from the air by using a series of filters combined with innovative technologies such as UV light or ionization processes. By eliminating particles that would otherwise accumulate on AC components like coils and fans over time, air scrubbers help ensure unobstructed airflow through the system.

Moreover, by reducing airborne contaminants before they reach sensitive parts of an AC unit or circulate freely in living spaces-air scrubbers not only protect equipment integrity but also promote healthier environments for occupants-a particularly important aspect considering increasing concerns about indoor pollution's health effects today more than ever before; thus making them invaluable additions especially beneficial amidst pandemic times when respiratory health takes precedence among everyday priorities worldwide alike!

In conclusion: integrating state-of-the-art solutions like those provided via installation(s) featuring cutting-edge technology known generally under umbrella term "air scrubbing" proves wise investment facilitating long-term benefits aligned towards sustainable future encompassing reduced costs alongside improved overall well-being attributed directly linked indirectly said improvements themselves seamlessly integrated existing infrastructure maximizing efficacy without compromising convenience adaptability thereof...

How Air Scrubbers Enhance Air Quality in HVAC Systems



In recent years, the quest for cleaner indoor air has intensified as people become more aware of the health implications of pollutants and allergens. As a result, many are turning to innovative technologies such as air scrubbers to enhance air quality within HVAC systems. These devices not only contribute to creating a healthier indoor environment but also play a crucial role in improving the overall performance of air conditioning (AC) systems.

Air scrubbers work by actively removing contaminants from the air that circulates through HVAC systems. They employ advanced filtration techniques and sometimes ultraviolet light or ionization processes to capture or neutralize particles such as dust, pollen, mold spores, bacteria, and even viruses. This leads to a significant reduction in airborne pollutants that can exacerbate allergies and respiratory issues.

The integration of air scrubbers into HVAC systems offers notable advantages beyond just purifying the air. By eliminating contaminants, these devices help maintain cleaner coils and ducts within AC units. Clean components are vital for optimal system performance; when dust and debris accumulate on coils or within ducts, they hinder airflow and force AC units to work harder than necessary. This increased workload can lead to higher energy consumption and potentially shorten the lifespan of the equipment due to wear and tear.

Moreover, improved airflow resulting from cleaner systems translates directly into enhanced cooling efficiency. When an AC unit operates under less strain with unobstructed pathways for air circulation, it cools spaces more effectively while consuming less energy. This not only results in lower utility bills but also contributes positively toward environmental conservation by reducing overall energy demand.

Another benefit of utilizing air scrubbers is their ability to prolong filter life within HVAC systems. By capturing particles before they reach traditional filters, scrubbers prevent premature clogging which often necessitates frequent replacements. Thus providing cost savings over time while ensuring consistently high levels of filtration efficiency throughout each filter's lifecycle.

In conclusion, incorporating air scrubbers into HVAC setups represents a forward-thinking approach towards achieving superior indoor air quality alongside bolstering AC system performance. Through effective removal of airborne pollutants coupled with maintenance benefits stemming from reduced component contamination-these devices stand out as valuable investments that align both health priorities with economic considerations for homeowners seeking maximum comfort without compromising sustainability objectives.

Citations and other links

The Role of Air Scrubbers in Reducing System Strain and Maintenance Needs

The Role of Air Scrubbers in Reducing System Strain and Maintenance Needs



Air conditioning systems are essential for maintaining comfort in both residential and commercial spaces, particularly during the sweltering summer months. However, these systems can often be burdened by the strain of continuous operation and the accumulation of airborne particles that reduce their efficiency. This is where air scrubbers come into play, offering a valuable solution to enhance AC performance while simultaneously reducing system strain and maintenance needs.

Air scrubbers are devices designed to remove contaminants from the air, including dust, pollen, mold spores, and other pollutants. By integrating an air scrubber into an HVAC system, it works continuously to purify the indoor air before it passes through the AC unit. This proactive approach significantly reduces the amount of debris that would otherwise accumulate on critical components such as coils and filters.

One of the primary benefits of using an air scrubber is its ability to alleviate system strain. When an AC unit operates with clean air flowing through it, there is less resistance against moving parts like fans and blowers. This reduction in mechanical stress means that components do not have to work as hard or consume more energy than necessary to maintain desired temperature levels. As a result, energy efficiency improves, leading to lower utility bills and a reduced carbon footprint.

Moreover, by keeping internal components cleaner for longer periods, air scrubbers help extend the lifespan of an AC system. Dust and dirt buildup can lead to corrosion or wear over time if not addressed promptly.

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With less frequent need for cleaning or replacement parts due to minimized contamination risks, homeowners and businesses alike can enjoy fewer interruptions caused by unexpected breakdowns or costly repairs.

In addition to prolonging equipment life spans and improving energy efficiency, air scrubbers contribute significantly towards better indoor air quality (IAQ). They effectively capture harmful pollutants that could otherwise circulate throughout living spaces via ductwork systems-this improvement in IAQ directly impacts occupant health by reducing allergy symptoms or respiratory issues linked with poor ventilation conditions.

Furthermore, investing in an air scrubber can lead to substantial long-term savings on maintenance costs. Routine checkups often reveal clogged filters or dirty coils requiring attention-a direct consequence of unfiltered particulates entering HVAC units unchecked over time without intervention strategies like those provided by advanced purification technologies present within modern-day scrubbing solutions today!

In conclusion: The role played by dedicated filtration methods such as those implemented through high-quality industrial-grade scrubbing apparatuses cannot be understated when considering overall operational efficiencies achieved across various sectors reliant upon climate control infrastructure daily basis worldwide! Air scrubbing technology not only enhances immediate functional capabilities but also ensures sustainable environmentally friendly practices supporting healthier communities everywhere thus proving indispensable asset amidst ever-evolving global challenges faced collectively now more than ever before historically speaking conclusively so far ahead future generations benefit equally well too naturally enough surely indeed ultimately therefore finally undeniably absolutely positively completely totally altogether unequivocally universally indisputably unmistakably evidently obviously patently clearly self-evident axiomatically factually verifiably irrefutably beyond doubt question debate discussion argument contradiction objection refutation denial contention dispute controversy disagreement dissent opposition challenge contestation conflict quarrel squabble altercation tiff spat bickering wrangling feuding discord disharmony unrest strife turbulence turmoil chaos pandemonium bedlam uproar commotion clamor hullabaloo hubbub brouhaha ruckus melee fracas skirmish row scuffle encounter exchange clash incident episode affair matter concern issue subject topic theme motif narrative storyline plot tale chronicle account saga legend myth fable parable allegory exemplum anecdote report review summary analysis critique evaluation appraisal

The Role of Air Scrubbers in Reducing System Strain and Maintenance Needs
Energy Efficiency Benefits of Integrating Air Scrubbers with AC Units

Energy Efficiency Benefits of Integrating Air Scrubbers with AC Units

Energy Efficiency Benefits of Integrating Air Scrubbers with AC Units



In recent years, the conversation surrounding energy efficiency has become increasingly prominent as individuals and businesses alike seek to reduce their environmental impact and energy costs. One innovative approach gaining traction is the integration of air scrubbers with air conditioning (AC) units. This combination not only enhances indoor air quality but also significantly improves the performance of AC systems, offering a host of energy efficiency benefits.

Air scrubbers are advanced devices designed to remove contaminants, pollutants, and particles from the air. When integrated with AC units, they work in tandem to create a cleaner and healthier indoor environment. But beyond just purifying air, this integration offers substantial improvements in energy efficiency.

Firstly, by removing airborne particles such as dust, pollen, and other pollutants before they reach the AC system's filters or coils, air scrubbers can significantly reduce wear and tear on these components. Cleaner coils mean that the AC unit does not have to work as hard to cool or heat a space since there is less obstruction hindering airflow and heat exchange processes. This reduction in strain can lead to lower energy consumption because the system operates more efficiently.

Moreover, when an AC unit runs more smoothly without having to compensate for clogged filters or dirty components, it often results in less frequent cycling on and off-an operation that typically consumes more energy than sustained running at a steady state. Therefore, integrating an air scrubber helps maintain optimal performance levels for longer periods while consuming less electricity.

Another key benefit is that improving indoor air quality through effective scrubbing can allow occupants to set their thermostats slightly higher during cooling months or lower during heating months without sacrificing comfort. Clean air tends to feel fresher and cooler due to reduced humidity levels brought about by efficient filtration systems working alongside dehumidifiers within modern AC units. As a result, even small adjustments in thermostat settings can lead to significant savings in energy bills over time.

Furthermore, when considering long-term maintenance costs associated with HVAC systems, integrating an air scrubber shows its financial advantages yet again. By keeping internal components cleaner for extended periods between professional services or part replacements such as coil cleaning sessions-which itself requires substantial amounts of water-a property owner could witness notable reductions both financially speaking regarding upkeep expenses directly tied into maintaining their entire HVAC infrastructure operating optimally year-round!

Lastly-and perhaps most importantly-the combined effect provides peace-of-mind knowing your household breathes easier thanks largely due diligence taken towards improving overall health outcomes via mitigating potential respiratory issues caused primarily through exposure unto harmful allergens commonly found indoors today!

In conclusion: Integrating Air Scrubbers With Existing Households' Centralized Heating Ventilation Air Conditioning Systems represents undoubtedly wise choice those seeking maximize return investment minimizing ecological footprint simultaneously achieving enhanced functionality improved operational efficiencies respective residential commercial real estate holdings alike!

Case Studies: Improved Performance in Real-World Applications

Case Studies: Improved Performance in Real-World Applications



Air scrubbers have emerged as a significant advancement in enhancing the performance of air conditioning (AC) systems, particularly in real-world applications where air quality and energy efficiency are critical. As modern society becomes increasingly conscious of environmental impacts and indoor air quality, integrating technologies like air scrubbers into AC systems offers substantial benefits.

An air scrubber is a device that removes contaminants from the air, effectively improving indoor air quality by eliminating pollutants such as dust, pollen, mold spores, bacteria, and volatile organic compounds (VOCs). By incorporating air scrubbers into AC systems, these pollutants are captured before they circulate within the building environment. This not only contributes to healthier living and working spaces but also enhances the overall efficiency of AC units.

One of the primary ways air scrubbers improve AC performance is through reduced workload on the system. When airborne particles accumulate on coils and filters within an AC unit, it can lead to decreased efficiency due to restricted airflow and increased energy consumption as the system works harder to maintain desired temperatures. By removing these particles from circulation before they reach sensitive components of the AC system, air scrubbers help maintain optimal operation conditions, thereby reducing strain and extending the lifespan of equipment.

Moreover, improved filtration provided by air scrubbers can lead to significant energy savings. Cleaner coils result in better heat exchange rates within the AC system, allowing it to run more efficiently while consuming less power. In large-scale commercial buildings or industrial settings where HVAC costs constitute a considerable portion of operational expenses, this improvement in energy efficiency translates directly into cost savings.

Case studies highlight several real-world applications where implementing air scrubbers has led to measurable improvements in both environmental conditions and economic outcomes. For instance, office buildings equipped with advanced scrubbing technology have reported reductions in employee sick days attributed to better indoor air quality. Similarly, manufacturing facilities have noted enhanced product consistency due to stable temperature control facilitated by efficient AC operations unimpeded by dust accumulation.

In conclusion, incorporating air scrubbers into existing or new AC systems presents a compelling case for organizations seeking improved performance through enhanced indoor environments and sustainable practices. Not only do they promote healthful conditions by purifying incoming airflow but also contribute significantly towards operational efficiencies through extended equipment longevity and reduced energy consumption-a win-win scenario for both business stakeholders and building occupants alike.

Cost-Benefit Analysis of Installing Air Scrubbers in Existing Systems

Cost-Benefit Analysis of Installing Air Scrubbers in Existing Systems



Air scrubbers have become an increasingly popular addition to HVAC systems, particularly in settings where air quality is paramount.

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Their ability to remove harmful particles and improve the overall environment makes them a compelling option for businesses and homeowners alike. However, before diving into the installation of air scrubbers within existing systems, it is crucial to conduct a thorough cost-benefit analysis to determine their true value and impact on AC performance.

Firstly, understanding the costs involved in installing air scrubbers is essential. The initial investment can be substantial, depending on the size and complexity of the existing HVAC system. Installation may require modifications or upgrades to accommodate the new equipment, potentially increasing labor costs. Additionally, ongoing maintenance expenses should be factored in; while air scrubbers are designed for durability, they still require regular upkeep to function optimally.

On the benefit side of the equation, one of the most significant advantages of installing air scrubbers is their ability to enhance indoor air quality dramatically. They effectively remove contaminants such as dust, pollen, mold spores, bacteria, and even some viruses from circulating through an AC system. This improvement not only contributes to healthier living or working environments but can also lead to reduced allergy symptoms and respiratory issues among occupants.

Moreover, by ensuring cleaner air passes through AC units consistently, air scrubbers help maintain system efficiency. When filters within an HVAC system are less burdened with debris and particles due to pre-filtration by air scrubbers, there tends to be less strain on the system's components. Consequently, this can extend the lifespan of both filters and mechanical parts like fans and coils while potentially reducing energy consumption since cleaner systems operate more efficiently.

Another invaluable benefit lies in compliance with regulatory standards or guidelines related to indoor air quality that might affect commercial establishments or public buildings. By proactively addressing these concerns through advanced filtration technologies like air scrubbers, organizations demonstrate commitment towards health regulations - possibly avoiding fines or sanctions.

In conclusion, conducting a cost-benefit analysis reveals that while there are upfront costs associated with integrating air scrubbers into existing HVAC systems - including purchase price and installation fees - these must be weighed against long-term gains achieved from improved AC performance along with enhanced environmental conditions inside properties. Not only do they contribute significantly toward better health outcomes for occupants by purifying circulated airflow but also aid operational efficiencies over time which could translate into appreciable savings down-the-line when considering decreased repair needs alongside potential reductions seen across utility bills owing largely due efficient operation achieved via clean operating machinery utilized throughout all seasons year-round ultimately making this strategic investment worthwhile consideration any forward-thinking organization looking capitalize upon innovations poised transform industry forevermore today tomorrow beyond!

A condensing boiler
Hot water central heating unit, using wood as fuel

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.

Overview

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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.

The four different generations of district heating systems and their energy sources

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.

History

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Ancient Korea

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An illustration of the ondol system

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 (Korean움집).

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.

Ancient Rome and Greece

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Ruins of the hypocaust under the floor of a Roman villa at La Olmeda, Province of Palencia (Castile and León, Spain)

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.

Modern central heating systems

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The three main methods of central heating were developed in the late 18th to mid-19th centuries.[9]

Hot air

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Sylvester's warm-air stove, 1819

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.

Steam

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Thomas Tredgold, a noted engineer and authority on central heating systems in the early 19th 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.

Hot water

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The Summer Palace in St. Petersburg had an early system of hydrologic central heating.

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.

Details of furnace and expansion tube from Perkins' 1838 Patent

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.

Energy sources

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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.

Calculating output of heater required

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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]

Billing

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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.

Types of central heating

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Water heating

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Active indirect water heater

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:

  • A supply of fuel, electric power or district heating supply lines
  • A boiler (or a heat exchanger for district heating) which heats water in the system
  • Pump to circulate the water
  • Radiators through which the heated water passes in order to release heat into rooms.

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.

Expansion tank in a sealed system
A straight braided filling loop used to add water to a sealed central heating system in the UK

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.

 

Steam heating

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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

[edit]

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.

Heat pumps

[edit]
External heat exchanger of an air source heat pump

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]

Environmental aspects

[edit]

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:

  • 65–97% for gas-fired heating;
  • 80–89% for oil-fired and
  • 45–60% for coal-fired heating.[26]

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.

See also

[edit]

References

[edit]
  1. ^ "energy.og – Electrical Resistance Heating". Retrieved 2015-01-15.
  2. ^ "History of Radiant Heating & Cooling Systems" (PDF). Healthyheating.com. Archived from the original (PDF) on 2017-12-04. Retrieved 2016-05-19.
  3. ^ Donald N., Clark (2000). Culture and Customs of Korea. GreenwoodPress. p. 94. ISBN 0313304564.
  4. ^ Harris, Cyril M. (2013-02-28). Illustrated Dictionary of Historic Architecture. Courier Corporation. ISBN 9780486132112.
  5. ^ "BBC - Romans - Technology". BBC. Archived from the original on 2007-10-18. Retrieved 2008-03-24.
  6. ^ "Hypocaust". Encyclopedic. Britannica Online. 2009. Retrieved 2009-01-29.
  7. ^ Hugh N. Kennedy, Hugh (1985). "From Polis To Madina: Urban Change In Late Antique And Early Islamic Syria". Past & Present (106). Oxford University Press: 3–27 [10–1]. doi:10.1093/past/106.1.3.
  8. ^ Hägermann & Schneider 1997, pp. 456–459
  9. ^ Robert Bruegmann. "Central Heating and Ventilation:Origins and Effects on Architectural Design" (PDF).
  10. ^ Sylvester, Charles (1819). The philosophy of domestic economy: as exemplified in the mode of warming ... p.48 et al.
  11. ^ Elliott, Paul (2000). "The Derbyshire General Infirmary and the Derby Philosophers: The Application of Industrial Architecture and Technology to Medical Institutions in Early-Nineteenth-Century England". Medical History. 46 (1): 65–92. doi:10.1017/S0025727300068745. PMC 1044459. PMID 11877984.
  12. ^ Patrick Mitchell (2008). Central Heating, Installation, Maintenance and Repair. WritersPrintShop. p. 5. ISBN 9781904623625.
  13. ^ Fawkes, F. A. (1881). "antiquity+of+hot-water+heating" "Horticultural Buildings: Their Construction, Heating, Interior Fittings, &c., with Remarks on Some of the Principles Involved and Their Application. (123 Illustrations.)".
  14. ^ Emmanuelle Gallo: "Jean Simon Bonnemain (1743–1830) and the Origins of Hot Water Central Heating" in Proceedings of the Second International Congress on Construction History (2006-06-17), pages 1043–1060; retrieved from http://halshs.archives-ouvertes.fr/halshs-00080479/en/ on 2007-02-05
  15. ^ Adam Gopnik (2012). "1". Winter: Five Windows on the Season. Quercus. ISBN 9781780874463.
  16. ^ McConnell, A. (2004). "Perkins, Angier March (1799–1881)". Oxford Dictionary of National Biography. Oxford University Press. Accessed 14 August 2007 (subscription required).
  17. ^ Family Sangalli / San Galli
  18. ^ The hot boxes of San Galli Archived 2010-02-07 at the Wayback Machine (in Russian)
  19. ^ Warmteverliesberekening
  20. ^ Warmteverliesberekening: software
  21. ^ Heat loss calculation
  22. ^ 2012 ASHRAE Handbook: Heating, Refrigeration, and Air Conditioning. 2012, ISBN 978 1936 504 251: Page 13.1
  23. ^ 2012 ASHRAE Handbook: Heating, Refrigeration, and Air Conditioning. 2012, ISBN 978 1936 504 251: chapter 11
  24. ^ Cooper, D. (2021-05-27). "The UK is sabotaging its own plan to decarbonize heating". Engadget. Archived from the original on 2021-05-27. Retrieved 2021-11-23.
  25. ^ a b c "Is cooling the future of heating? – Analysis". IEA. 13 December 2020. Retrieved 2023-04-27.  This article incorporates text available under the CC BY 4.0 license.
  26. ^ EERE Consumer's Guide: Selecting Heating Fuel and System Types

Sources

[edit]
  • Hägermann, Dieter; Schneider, Helmuth (1997). Propyläen Technikgeschichte. Landbau und Handwerk, 750 v. Chr. bis 1000 n. Chr (2nd ed.). Berlin. ISBN 3-549-05632-X.cite book: CS1 maint: location missing publisher (link)

Further reading

[edit]
  • Adams, Sean Patrick. Home Fires: How Americans Kept Warm in the 19th Century (Johns Hopkins University Press, 2014), 183 pp
[edit]

 

 

There are various types of air conditioners. Popular examples include: Window-mounted air conditioner (Suriname, 1955); Ceiling-mounted cassette air conditioner (China, 2023); Wall-mounted air conditioner (Japan, 2020); Ceiling-mounted console (Also called ceiling suspended) air conditioner (China, 2023); and portable air conditioner (Vatican City, 2018).

Air conditioning, often abbreviated as A/C (US) or air con (UK),[1] is the process of removing heat from an enclosed space to achieve a more comfortable interior temperature and in some cases also controlling the humidity of internal air. Air conditioning can be achieved using a mechanical 'air conditioner' or by other methods, including passive cooling and ventilative cooling.[2][3] Air conditioning is a member of a family of systems and techniques that provide heating, ventilation, and air conditioning (HVAC).[4] Heat pumps are similar in many ways to air conditioners, but use a reversing valve to allow them both to heat and to cool an enclosed space.[5]

Air conditioners, which typically use vapor-compression refrigeration, range in size from small units used in vehicles or single rooms to massive units that can cool large buildings.[6] Air source heat pumps, which can be used for heating as well as cooling, are becoming increasingly common in cooler climates.

Air conditioners can reduce mortality rates due to higher temperature.[7] According to the International Energy Agency (IEA) 1.6 billion air conditioning units were used globally in 2016.[8] The United Nations called for the technology to be made more sustainable to mitigate climate change and for the use of alternatives, like passive cooling, evaporative cooling, selective shading, windcatchers, and better thermal insulation.

History

[edit]

Air conditioning dates back to prehistory.[9] Double-walled living quarters, with a gap between the two walls to encourage air flow, were found in the ancient city of Hamoukar, in modern Syria.[10] Ancient Egyptian buildings also used a wide variety of passive air-conditioning techniques.[11] These became widespread from the Iberian Peninsula through North Africa, the Middle East, and Northern India.[12]

Passive techniques remained widespread until the 20th century when they fell out of fashion and were replaced by powered air conditioning. Using information from engineering studies of traditional buildings, passive techniques are being revived and modified for 21st-century architectural designs.[13][12]

An array of air conditioner condenser units outside a commercial office building

Air conditioners allow the building's indoor environment to remain relatively constant, largely independent of changes in external weather conditions and internal heat loads. They also enable deep plan buildings to be created and have allowed people to live comfortably in hotter parts of the world.[14]

Development

[edit]

Preceding discoveries

[edit]

In 1558, Giambattista della Porta described a method of chilling ice to temperatures far below its freezing point by mixing it with potassium nitrate (then called "nitre") in his popular science book Natural Magic.[15][16][17] In 1620, Cornelis Drebbel demonstrated "Turning Summer into Winter" for James I of England, chilling part of the Great Hall of Westminster Abbey with an apparatus of troughs and vats.[18] Drebbel's contemporary Francis Bacon, like della Porta a believer in science communication, may not have been present at the demonstration, but in a book published later the same year, he described it as "experiment of artificial freezing" and said that "Nitre (or rather its spirit) is very cold, and hence nitre or salt when added to snow or ice intensifies the cold of the latter, the nitre by adding to its cold, but the salt by supplying activity to the cold of the snow."[15]

In 1758, Benjamin Franklin and John Hadley, a chemistry professor at the University of Cambridge, conducted experiments applying the principle of evaporation as a means to cool an object rapidly. Franklin and Hadley confirmed that the evaporation of highly volatile liquids (such as alcohol and ether) could be used to drive down the temperature of an object past the freezing point of water. They experimented with the bulb of a mercury-in-glass thermometer as their object. They used a bellows to speed up the evaporation. They lowered the temperature of the thermometer bulb down to −14 °C (7 °F) while the ambient temperature was 18 °C (64 °F). Franklin noted that soon after they passed the freezing point of water 0 °C (32 °F), a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about 6 mm (14 in) thick when they stopped the experiment upon reaching −14 °C (7 °F). Franklin concluded: "From this experiment, one may see the possibility of freezing a man to death on a warm summer's day."[19]

The 19th century included many developments in compression technology. In 1820, English scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate.[20] In 1842, Florida physician John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital in Apalachicola, Florida. He hoped to eventually use his ice-making machine to regulate the temperature of buildings.[20][21] He envisioned centralized air conditioning that could cool entire cities. Gorrie was granted a patent in 1851,[22] but following the death of his main backer, he was not able to realize his invention.[23] In 1851, James Harrison created the first mechanical ice-making machine in Geelong, Australia, and was granted a patent for an ether vapor-compression refrigeration system in 1855 that produced three tons of ice per day.[24] In 1860, Harrison established a second ice company. He later entered the debate over competing against the American advantage of ice-refrigerated beef sales to the United Kingdom.[24]

First devices

[edit]
Willis Carrier, who is credited with building the first modern electrical air conditioning unit

Electricity made the development of effective units possible. In 1901, American inventor Willis H. Carrier built what is considered the first modern electrical air conditioning unit.[25][26][27][28] In 1902, he installed his first air-conditioning system, in the Sackett-Wilhelms Lithographing & Publishing Company in Brooklyn, New York.[29] His invention controlled both the temperature and humidity, which helped maintain consistent paper dimensions and ink alignment at the printing plant. Later, together with six other employees, Carrier formed The Carrier Air Conditioning Company of America, a business that in 2020 employed 53,000 people and was valued at $18.6 billion.[30][31]

In 1906, Stuart W. Cramer of Charlotte, North Carolina, was exploring ways to add moisture to the air in his textile mill. Cramer coined the term "air conditioning" in a patent claim which he filed that year, where he suggested that air conditioning was analogous to "water conditioning", then a well-known process for making textiles easier to process.[32] He combined moisture with ventilation to "condition" and change the air in the factories; thus, controlling the humidity that is necessary in textile plants. Willis Carrier adopted the term and incorporated it into the name of his company.[33]

Domestic air conditioning soon took off. In 1914, the first domestic air conditioning was installed in Minneapolis in the home of Charles Gilbert Gates. It is, however, possible that the considerable device (c. 2.1 m × 1.8 m × 6.1 m; 7 ft × 6 ft × 20 ft) was never used, as the house remained uninhabited[20] (Gates had already died in October 1913.)

In 1931, H.H. Schultz and J.Q. Sherman developed what would become the most common type of individual room air conditioner: one designed to sit on a window ledge. The units went on sale in 1932 at US$10,000 to $50,000 (the equivalent of $200,000 to $1,200,000 in 2024.)[20] A year later, the first air conditioning systems for cars were offered for sale.[34] Chrysler Motors introduced the first practical semi-portable air conditioning unit in 1935,[35] and Packard became the first automobile manufacturer to offer an air conditioning unit in its cars in 1939.[36]

Further development

[edit]

Innovations in the latter half of the 20th century allowed more ubiquitous air conditioner use. In 1945, Robert Sherman of Lynn, Massachusetts, invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air.[37] The first inverter air conditioners were released in 1980–1981.[38][39]

In 1954, Ned Cole, a 1939 architecture graduate from the University of Texas at Austin, developed the first experimental "suburb" with inbuilt air conditioning in each house. 22 homes were developed on a flat, treeless track in northwest Austin, Texas, and the community was christened the 'Austin Air-Conditioned Village.' The residents were subjected to a year-long study of the effects of air conditioning led by the nation’s premier air conditioning companies, builders, and social scientists. In addition, researchers from UT’s Health Service and Psychology Department studied the effects on the "artificially cooled humans." One of the more amusing discoveries was that each family reported being troubled with scorpions, the leading theory being that scorpions sought cool, shady places. Other reported changes in lifestyle were that mothers baked more, families ate heavier foods, and they were more apt to choose hot drinks.[40][41]

Air conditioner adoption tends to increase above around $10,000 annual household income in warmer areas.[42] Global GDP growth explains around 85% of increased air condition adoption by 2050, while the remaining 15% can be explained by climate change.[42]

As of 2016 an estimated 1.6 billion air conditioning units were used worldwide, with over half of them in China and USA, and a total cooling capacity of 11,675 gigawatts.[8][43] The International Energy Agency predicted in 2018 that the number of air conditioning units would grow to around 4 billion units by 2050 and that the total cooling capacity would grow to around 23,000 GW, with the biggest increases in India and China.[8] Between 1995 and 2004, the proportion of urban households in China with air conditioners increased from 8% to 70%.[44] As of 2015, nearly 100 million homes, or about 87% of US households, had air conditioning systems.[45] In 2019, it was estimated that 90% of new single-family homes constructed in the US included air conditioning (ranging from 99% in the South to 62% in the West).[46][47]

Operation

[edit]

Operating principles

[edit]
A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor

Cooling in traditional air conditioner systems is accomplished using the vapor-compression cycle, which uses a refrigerant's forced circulation and phase change between gas and liquid to transfer heat.[48][49] The vapor-compression cycle can occur within a unitary, or packaged piece of equipment; or within a chiller that is connected to terminal cooling equipment (such as a fan coil unit in an air handler) on its evaporator side and heat rejection equipment such as a cooling tower on its condenser side. An air source heat pump shares many components with an air conditioning system, but includes a reversing valve, which allows the unit to be used to heat as well as cool a space.[50]

Air conditioning equipment will reduce the absolute humidity of the air processed by the system if the surface of the evaporator coil is significantly cooler than the dew point of the surrounding air. An air conditioner designed for an occupied space will typically achieve a 30% to 60% relative humidity in the occupied space.[51]

Most modern air-conditioning systems feature a dehumidification cycle during which the compressor runs. At the same time, the fan is slowed to reduce the evaporator temperature and condense more water. A dehumidifier uses the same refrigeration cycle but incorporates both the evaporator and the condenser into the same air path; the air first passes over the evaporator coil, where it is cooled[52] and dehumidified before passing over the condenser coil, where it is warmed again before it is released back into the room.[citation needed]

Free cooling can sometimes be selected when the external air is cooler than the internal air. Therefore, the compressor does not need to be used, resulting in high cooling efficiencies for these times. This may also be combined with seasonal thermal energy storage.[53]

Heating

[edit]

Some air conditioning systems can reverse the refrigeration cycle and act as an air source heat pump, thus heating instead of cooling the indoor environment. They are also commonly referred to as "reverse cycle air conditioners". The heat pump is significantly more energy-efficient than electric resistance heating, because it moves energy from air or groundwater to the heated space and the heat from purchased electrical energy. When the heat pump is in heating mode, the indoor evaporator coil switches roles and becomes the condenser coil, producing heat. The outdoor condenser unit also switches roles to serve as the evaporator and discharges cold air (colder than the ambient outdoor air).

Most air source heat pumps become less efficient in outdoor temperatures lower than 4 °C or 40 °F.[54] This is partly because ice forms on the outdoor unit's heat exchanger coil, which blocks air flow over the coil. To compensate for this, the heat pump system must temporarily switch back into the regular air conditioning mode to switch the outdoor evaporator coil back to the condenser coil, to heat up and defrost. Therefore, some heat pump systems will have electric resistance heating in the indoor air path that is activated only in this mode to compensate for the temporary indoor air cooling, which would otherwise be uncomfortable in the winter.

Newer models have improved cold-weather performance, with efficient heating capacity down to −14 °F (−26 °C).[55][54][56] However, there is always a chance that the humidity that condenses on the heat exchanger of the outdoor unit could freeze, even in models that have improved cold-weather performance, requiring a defrosting cycle to be performed.

The icing problem becomes much more severe with lower outdoor temperatures, so heat pumps are sometimes installed in tandem with a more conventional form of heating, such as an electrical heater, a natural gas, heating oil, or wood-burning fireplace or central heating, which is used instead of or in addition to the heat pump during harsher winter temperatures. In this case, the heat pump is used efficiently during milder temperatures, and the system is switched to the conventional heat source when the outdoor temperature is lower.

Performance

[edit]

The coefficient of performance (COP) of an air conditioning system is a ratio of useful heating or cooling provided to the work required.[57][58] Higher COPs equate to lower operating costs. The COP usually exceeds 1; however, the exact value is highly dependent on operating conditions, especially absolute temperature and relative temperature between sink and system, and is often graphed or averaged against expected conditions.[59] Air conditioner equipment power in the U.S. is often described in terms of "tons of refrigeration", with each approximately equal to the cooling power of one short ton (2,000 pounds (910 kg) of ice melting in a 24-hour period. The value is equal to 12,000 BTUIT per hour, or 3,517 watts.[60] Residential central air systems are usually from 1 to 5 tons (3.5 to 18 kW) in capacity.[citation needed]

The efficiency of air conditioners is often rated by the seasonal energy efficiency ratio (SEER), which is defined by the Air Conditioning, Heating and Refrigeration Institute in its 2008 standard AHRI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment.[61] A similar standard is the European seasonal energy efficiency ratio (ESEER).[citation needed]

Efficiency is strongly affected by the humidity of the air to be cooled. Dehumidifying the air before attempting to cool it can reduce subsequent cooling costs by as much as 90 percent. Thus, reducing dehumidifying costs can materially affect overall air conditioning costs.[62]

Control system

[edit]

Wireless remote control

[edit]
A wireless remote controller
The infrared transmitting LED on the remote
The infrared receiver on the air conditioner

This type of controller uses an infrared LED to relay commands from a remote control to the air conditioner. The output of the infrared LED (like that of any infrared remote) is invisible to the human eye because its wavelength is beyond the range of visible light (940 nm). This system is commonly used on mini-split air conditioners because it is simple and portable. Some window and ducted central air conditioners uses it as well.

Wired controller

[edit]
Several wired controllers (Indonesia, 2024)

A wired controller, also called a "wired thermostat," is a device that controls an air conditioner by switching heating or cooling on or off. It uses different sensors to measure temperatures and actuate control operations. Mechanical thermostats commonly use bimetallic strips, converting a temperature change into mechanical displacement, to actuate control of the air conditioner. Electronic thermostats, instead, use a thermistor or other semiconductor sensor, processing temperature change as electronic signals to control the air conditioner.

These controllers are usually used in hotel rooms because they are permanently installed into a wall and hard-wired directly into the air conditioner unit, eliminating the need for batteries.

Types

[edit]
 
Types Typical Capacity* Air supply Mounting Typical application
Mini-split small – large Direct Wall Residential
Window very small – small Direct Window Residential
Portable very small – small Direct / Ducted Floor Residential, remote areas
Ducted (individual) small – very large Ducted Ceiling Residential, commercial
Ducted (central) medium – very large Ducted Ceiling Residential, commercial
Ceiling suspended medium – large Direct Ceiling Commercial
Cassette medium – large Direct / Ducted Ceiling Commercial
Floor standing medium – large Direct / Ducted Floor Commercial
Packaged very large Direct / Ducted Floor Commercial
Packaged RTU (Rooftop Unit) very large Ducted Rooftop Commercial

* where the typical capacity is in kilowatt as follows:

  • very small: <1.5 kW
  • small: 1.5–3.5 kW
  • medium: 4.2–7.1 kW
  • large: 7.2–14 kW
  • very large: >14 kW

Mini-split and multi-split systems

[edit]
Evaporator, indoor unit, or terminal, side of a ductless split-type air conditioner

Ductless systems (often mini-split, though there are now ducted mini-split) typically supply conditioned and heated air to a single or a few rooms of a building, without ducts and in a decentralized manner.[63] Multi-zone or multi-split systems are a common application of ductless systems and allow up to eight rooms (zones or locations) to be conditioned independently from each other, each with its indoor unit and simultaneously from a single outdoor unit.

The first mini-split system was sold in 1961 by Toshiba in Japan, and the first wall-mounted mini-split air conditioner was sold in 1968 in Japan by Mitsubishi Electric, where small home sizes motivated their development. The Mitsubishi model was the first air conditioner with a cross-flow fan.[64][65][66] In 1969, the first mini-split air conditioner was sold in the US.[67] Multi-zone ductless systems were invented by Daikin in 1973, and variable refrigerant flow systems (which can be thought of as larger multi-split systems) were also invented by Daikin in 1982. Both were first sold in Japan.[68] Variable refrigerant flow systems when compared with central plant cooling from an air handler, eliminate the need for large cool air ducts, air handlers, and chillers; instead cool refrigerant is transported through much smaller pipes to the indoor units in the spaces to be conditioned, thus allowing for less space above dropped ceilings and a lower structural impact, while also allowing for more individual and independent temperature control of spaces. The outdoor and indoor units can be spread across the building.[69] Variable refrigerant flow indoor units can also be turned off individually in unused spaces.[citation needed] The lower start-up power of VRF's DC inverter compressors and their inherent DC power requirements also allow VRF solar-powered heat pumps to be run using DC-providing solar panels.

Ducted central systems

[edit]

Split-system central air conditioners consist of two heat exchangers, an outside unit (the condenser) from which heat is rejected to the environment and an internal heat exchanger (the evaporator, or Fan Coil Unit, FCU) with the piped refrigerant being circulated between the two. The FCU is then connected to the spaces to be cooled by ventilation ducts.[70] Floor standing air conditioners are similar to this type of air conditioner but sit within spaces that need cooling.

Central plant cooling

[edit]
Industrial air conditioners on top of the shopping mall Passage in Linz, Austria

Large central cooling plants may use intermediate coolant such as chilled water pumped into air handlers or fan coil units near or in the spaces to be cooled which then duct or deliver cold air into the spaces to be conditioned, rather than ducting cold air directly to these spaces from the plant, which is not done due to the low density and heat capacity of air, which would require impractically large ducts. The chilled water is cooled by chillers in the plant, which uses a refrigeration cycle to cool water, often transferring its heat to the atmosphere even in liquid-cooled chillers through the use of cooling towers. Chillers may be air- or liquid-cooled.[71][72]

Portable units

[edit]

A portable system has an indoor unit on wheels connected to an outdoor unit via flexible pipes, similar to a permanently fixed installed unit (such as a ductless split air conditioner).

Hose systems, which can be monoblock or air-to-air, are vented to the outside via air ducts. The monoblock type collects the water in a bucket or tray and stops when full. The air-to-air type re-evaporates the water, discharges it through the ducted hose, and can run continuously. Many but not all portable units draw indoor air and expel it outdoors through a single duct, negatively impacting their overall cooling efficiency.

Many portable air conditioners come with heat as well as a dehumidification function.[73]

Window unit and packaged terminal

[edit]
Through-the-wall PTAC units, University Motor Inn, Philadelphia

The packaged terminal air conditioner (PTAC), through-the-wall, and window air conditioners are similar. These units are installed on a window frame or on a wall opening. The unit usually has an internal partition separating its indoor and outdoor sides, which contain the unit's condenser and evaporator, respectively. PTAC systems may be adapted to provide heating in cold weather, either directly by using an electric strip, gas, or other heaters, or by reversing the refrigerant flow to heat the interior and draw heat from the exterior air, converting the air conditioner into a heat pump. They may be installed in a wall opening with the help of a special sleeve on the wall and a custom grill that is flush with the wall and window air conditioners can also be installed in a window, but without a custom grill.[74]

Packaged air conditioner

[edit]

Packaged air conditioners (also known as self-contained units)[75][76] are central systems that integrate into a single housing all the components of a split central system, and deliver air, possibly through ducts, to the spaces to be cooled. Depending on their construction they may be outdoors or indoors, on roofs (rooftop units),[77][78] draw the air to be conditioned from inside or outside a building and be water or air-cooled. Often, outdoor units are air-cooled while indoor units are liquid-cooled using a cooling tower.[70][79][80][81][82][83]

Types of compressors

[edit]
 
Compressor types Common applications Typical capacity Efficiency Durability Repairability
Reciprocating Refrigerator, Walk-in freezer, portable air conditioners small – large very low (small capacity)

medium (large capacity)

very low medium
Rotary vane Residential mini splits small low low easy
Scroll Commercial and central systems, VRF medium medium medium easy
Rotary screw Commercial chiller medium – large medium medium hard
Centrifugal Commercial chiller very large medium high hard
Maglev Centrifugal Commercial chiller very large high very high very hard

Reciprocating

[edit]

This compressor consists of a crankcase, crankshaft, piston rod, piston, piston ring, cylinder head and valves. [citation needed]

Scroll

[edit]

This compressor uses two interleaving scrolls to compress the refrigerant.[84] it consists of one fixed and one orbiting scrolls. This type of compressor is more efficient because it has 70 percent less moving parts than a reciprocating compressor. [citation needed]

Screw

[edit]

This compressor use two very closely meshing spiral rotors to compress the gas. The gas enters at the suction side and moves through the threads as the screws rotate. The meshing rotors force the gas through the compressor, and the gas exits at the end of the screws. The working area is the inter-lobe volume between the male and female rotors. It is larger at the intake end, and decreases along the length of the rotors until the exhaust port. This change in volume is the compression. [citation needed]

Capacity modulation technologies

[edit]

There are several ways to modulate the cooling capacity in refrigeration or air conditioning and heating systems. The most common in air conditioning are: on-off cycling, hot gas bypass, use or not of liquid injection, manifold configurations of multiple compressors, mechanical modulation (also called digital), and inverter technology. [citation needed]

Hot gas bypass

[edit]

Hot gas bypass involves injecting a quantity of gas from discharge to the suction side. The compressor will keep operating at the same speed, but due to the bypass, the refrigerant mass flow circulating with the system is reduced, and thus the cooling capacity. This naturally causes the compressor to run uselessly during the periods when the bypass is operating. The turn down capacity varies between 0 and 100%.[85]

Manifold configurations

[edit]

Several compressors can be installed in the system to provide the peak cooling capacity. Each compressor can run or not in order to stage the cooling capacity of the unit. The turn down capacity is either 0/33/66 or 100% for a trio configuration and either 0/50 or 100% for a tandem.[citation needed]

Mechanically modulated compressor

[edit]

This internal mechanical capacity modulation is based on periodic compression process with a control valve, the two scroll set move apart stopping the compression for a given time period. This method varies refrigerant flow by changing the average time of compression, but not the actual speed of the motor. Despite an excellent turndown ratio – from 10 to 100% of the cooling capacity, mechanically modulated scrolls have high energy consumption as the motor continuously runs.[citation needed]

Variable-speed compressor

[edit]

This system uses a variable-frequency drive (also called an Inverter) to control the speed of the compressor. The refrigerant flow rate is changed by the change in the speed of the compressor. The turn down ratio depends on the system configuration and manufacturer. It modulates from 15 or 25% up to 100% at full capacity with a single inverter from 12 to 100% with a hybrid tandem. This method is the most efficient way to modulate an air conditioner's capacity. It is up to 58% more efficient than a fixed speed system.[citation needed]

Impact

[edit]

Health effects

[edit]
Rooftop condenser unit fitted on top of an Osaka Municipal Subway 10 series subway carriage. Air conditioning has become increasingly prevalent on public transport vehicles as a form of climate control, and to ensure passenger comfort and drivers' occupational safety and health.

In hot weather, air conditioning can prevent heat stroke, dehydration due to excessive sweating, electrolyte imbalance, kidney failure, and other issues due to hyperthermia.[8][86] Heat waves are the most lethal type of weather phenomenon in the United States.[87][88] A 2020 study found that areas with lower use of air conditioning correlated with higher rates of heat-related mortality and hospitalizations.[89] The August 2003 France heatwave resulted in approximately 15,000 deaths, where 80% of the victims were over 75 years old. In response, the French government required all retirement homes to have at least one air-conditioned room at 25 °C (77 °F) per floor during heatwaves.[8]

Air conditioning (including filtration, humidification, cooling and disinfection) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where proper atmosphere is critical to patient safety and well-being. It is sometimes recommended for home use by people with allergies, especially mold.[90][91] However, poorly maintained water cooling towers can promote the growth and spread of microorganisms such as Legionella pneumophila, the infectious agent responsible for Legionnaires' disease. As long as the cooling tower is kept clean (usually by means of a chlorine treatment), these health hazards can be avoided or reduced. The state of New York has codified requirements for registration, maintenance, and testing of cooling towers to protect against Legionella.[92]

Economic effects

[edit]

First designed to benefit targeted industries such as the press as well as large factories, the invention quickly spread to public agencies and administrations with studies with claims of increased productivity close to 24% in places equipped with air conditioning.[93]

Air conditioning caused various shifts in demography, notably that of the United States starting from the 1970s. In the US, the birth rate was lower in the spring than during other seasons until the 1970s but this difference then declined since then.[94] As of 2007, the Sun Belt contained 30% of the total US population while it was inhabited by 24% of Americans at the beginning of the 20th century.[95] Moreover, the summer mortality rate in the US, which had been higher in regions subject to a heat wave during the summer, also evened out.[7]

The spread of the use of air conditioning acts as a main driver for the growth of global demand of electricity.[96] According to a 2018 report from the International Energy Agency (IEA), it was revealed that the energy consumption for cooling in the United States, involving 328 million Americans, surpasses the combined energy consumption of 4.4 billion people in Africa, Latin America, the Middle East, and Asia (excluding China).[8] A 2020 survey found that an estimated 88% of all US households use AC, increasing to 93% when solely looking at homes built between 2010 and 2020.[97]

Environmental effects

[edit]
Air conditioner farm in the facade of a building in Singapore

Space cooling including air conditioning accounted globally for 2021 terawatt-hours of energy usage in 2016 with around 99% in the form of electricity, according to a 2018 report on air-conditioning efficiency by the International Energy Agency.[8] The report predicts an increase of electricity usage due to space cooling to around 6200 TWh by 2050,[8][98] and that with the progress currently seen, greenhouse gas emissions attributable to space cooling will double: 1,135 million tons (2016) to 2,070 million tons.[8] There is some push to increase the energy efficiency of air conditioners. United Nations Environment Programme (UNEP) and the IEA found that if air conditioners could be twice as effective as now, 460 billion tons of GHG could be cut over 40 years.[99] The UNEP and IEA also recommended legislation to decrease the use of hydrofluorocarbons, better building insulation, and more sustainable temperature-controlled food supply chains going forward.[99]

Refrigerants have also caused and continue to cause serious environmental issues, including ozone depletion and climate change, as several countries have not yet ratified the Kigali Amendment to reduce the consumption and production of hydrofluorocarbons.[100] CFCs and HCFCs refrigerants such as R-12 and R-22, respectively, used within air conditioners have caused damage to the ozone layer,[101] and hydrofluorocarbon refrigerants such as R-410A and R-404A, which were designed to replace CFCs and HCFCs, are instead exacerbating climate change.[102] Both issues happen due to the venting of refrigerant to the atmosphere, such as during repairs. HFO refrigerants, used in some if not most new equipment, solve both issues with an ozone damage potential (ODP) of zero and a much lower global warming potential (GWP) in the single or double digits vs. the three or four digits of hydrofluorocarbons.[103]

Hydrofluorocarbons would have raised global temperatures by around 0.3–0.5 °C (0.5–0.9 °F) by 2100 without the Kigali Amendment. With the Kigali Amendment, the increase of global temperatures by 2100 due to hydrofluorocarbons is predicted to be around 0.06 °C (0.1 °F).[104]

Alternatives to continual air conditioning include passive cooling, passive solar cooling, natural ventilation, operating shades to reduce solar gain, using trees, architectural shades, windows (and using window coatings) to reduce solar gain.[citation needed]

Social effects

[edit]

Socioeconomic groups with a household income below around $10,000 tend to have a low air conditioning adoption,[42] which worsens heat-related mortality.[7] The lack of cooling can be hazardous, as areas with lower use of air conditioning correlate with higher rates of heat-related mortality and hospitalizations.[89] Premature mortality in NYC is projected to grow between 47% and 95% in 30 years, with lower-income and vulnerable populations most at risk.[89] Studies on the correlation between heat-related mortality and hospitalizations and living in low socioeconomic locations can be traced in Phoenix, Arizona,[105] Hong Kong,[106] China,[106] Japan,[107] and Italy.[108][109] Additionally, costs concerning health care can act as another barrier, as the lack of private health insurance during a 2009 heat wave in Australia, was associated with heat-related hospitalization.[109]

Disparities in socioeconomic status and access to air conditioning are connected by some to institutionalized racism, which leads to the association of specific marginalized communities with lower economic status, poorer health, residing in hotter neighborhoods, engaging in physically demanding labor, and experiencing limited access to cooling technologies such as air conditioning.[109] A study overlooking Chicago, Illinois, Detroit, and Michigan found that black households were half as likely to have central air conditioning units when compared to their white counterparts.[110] Especially in cities, Redlining creates heat islands, increasing temperatures in certain parts of the city.[109] This is due to materials heat-absorbing building materials and pavements and lack of vegetation and shade coverage.[111] There have been initiatives that provide cooling solutions to low-income communities, such as public cooling spaces.[8][111]

Other techniques

[edit]

Buildings designed with passive air conditioning are generally less expensive to construct and maintain than buildings with conventional HVAC systems with lower energy demands.[112] While tens of air changes per hour, and cooling of tens of degrees, can be achieved with passive methods, site-specific microclimate must be taken into account, complicating building design.[12]

Many techniques can be used to increase comfort and reduce the temperature in buildings. These include evaporative cooling, selective shading, wind, thermal convection, and heat storage.[113]

Passive ventilation

[edit]
The ventilation system of a regular earthship
Dogtrot houses are designed to maximise natural ventilation.
A roof turbine ventilator, colloquially known as a 'Whirly Bird' is an application of wind driven ventilation.

Passive ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural forces.

There are two types of natural ventilation occurring in buildings: wind driven ventilation and buoyancy-driven ventilation. Wind driven ventilation arises from the different pressures created by wind around a building or structure, and openings being formed on the perimeter which then permit flow through the building. Buoyancy-driven ventilation occurs as a result of the directional buoyancy force that results from temperature differences between the interior and exterior.[114]

Since the internal heat gains which create temperature differences between the interior and exterior are created by natural processes, including the heat from people, and wind effects are variable, naturally ventilated buildings are sometimes called "breathing buildings".

Passive cooling

[edit]
 
A traditional Iranian solar cooling design using a wind tower

Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption.[115][116] This approach works either by preventing heat from entering the interior (heat gain prevention) or by removing heat from the building (natural cooling).[117]

Natural cooling utilizes on-site energy, available from the natural environment, combined with the architectural design of building components (e.g. building envelope), rather than mechanical systems to dissipate heat.[118] Therefore, natural cooling depends not only on the architectural design of the building but on how the site's natural resources are used as heat sinks (i.e. everything that absorbs or dissipates heat). Examples of on-site heat sinks are the upper atmosphere (night sky), the outdoor air (wind), and the earth/soil.

Passive cooling is an important tool for design of buildings for climate change adaptation – reducing dependency on energy-intensive air conditioning in warming environments.[119][120]
A pair of short windcatchers (malqaf) used in traditional architecture; wind is forced down on the windward side and leaves on the leeward side (cross-ventilation). In the absence of wind, the circulation can be driven with evaporative cooling in the inlet (which is also designed to catch dust). In the center, a shuksheika (roof lantern vent), used to shade the qa'a below while allowing hot air rise out of it (stack effect).[11]

Daytime radiative cooling

[edit]
Passive daytime radiative cooling (PDRC) surfaces are high in solar reflectance and heat emittance, cooling with zero energy use or pollution.[121]

Passive daytime radiative cooling (PDRC) surfaces reflect incoming solar radiation and heat back into outer space through the infrared window for cooling during the daytime. Daytime radiative cooling became possible with the ability to suppress solar heating using photonic structures, which emerged through a study by Raman et al. (2014).[122] PDRCs can come in a variety of forms, including paint coatings and films, that are designed to be high in solar reflectance and thermal emittance.[121][123]

PDRC applications on building roofs and envelopes have demonstrated significant decreases in energy consumption and costs.[123] In suburban single-family residential areas, PDRC application on roofs can potentially lower energy costs by 26% to 46%.[124] PDRCs are predicted to show a market size of ~$27 billion for indoor space cooling by 2025 and have undergone a surge in research and development since the 2010s.[125][126]

Fans

[edit]

Hand fans have existed since prehistory. Large human-powered fans built into buildings include the punkah.

The 2nd-century Chinese inventor Ding Huan of the Han dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered by prisoners.[127]: 99, 151, 233  In 747, Emperor Xuanzong (r. 712–762) of the Tang dynasty (618–907) had the Cool Hall (Liang Dian 涼殿) built in the imperial palace, which the Tang Yulin describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song dynasty (960–1279), written sources mentioned the air conditioning rotary fan as even more widely used.[127]: 134, 151 

Thermal buffering

[edit]

In areas that are cold at night or in winter, heat storage is used. Heat may be stored in earth or masonry; air is drawn past the masonry to heat or cool it.[13]

In areas that are below freezing at night in winter, snow and ice can be collected and stored in ice houses for later use in cooling.[13] This technique is over 3,700 years old in the Middle East.[128] Harvesting outdoor ice during winter and transporting and storing for use in summer was practiced by wealthy Europeans in the early 1600s,[15] and became popular in Europe and the Americas towards the end of the 1600s.[129] This practice was replaced by mechanical compression-cycle icemakers.

Evaporative cooling

[edit]
An evaporative cooler

In dry, hot climates, the evaporative cooling effect may be used by placing water at the air intake, such that the draft draws air over water and then into the house. For this reason, it is sometimes said that the fountain, in the architecture of hot, arid climates, is like the fireplace in the architecture of cold climates.[11] Evaporative cooling also makes the air more humid, which can be beneficial in a dry desert climate.[130]

Evaporative coolers tend to feel as if they are not working during times of high humidity, when there is not much dry air with which the coolers can work to make the air as cool as possible for dwelling occupants. Unlike other types of air conditioners, evaporative coolers rely on the outside air to be channeled through cooler pads that cool the air before it reaches the inside of a house through its air duct system; this cooled outside air must be allowed to push the warmer air within the house out through an exhaust opening such as an open door or window.[131]

See also

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