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Solar air conditioning, or "solar-powered air conditioning", refers to any
air conditioning Air conditioning, often abbreviated as A/C or AC, is the process of removing heat from an enclosed space to achieve a more comfortable interior environment (sometimes referred to as 'comfort cooling') and in some cases also strictly controlling ...
(cooling) system that uses
solar power Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV) or indirectly using concentrated solar power. Photovoltaic cells convert light into an electric current using the photovoltaic e ...
. This can be done through
passive solar In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...
design,
solar thermal energy Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to generate thermal energy for use in industry, and in the residential and commercial sectors. Solar thermal collectors are classified by the United St ...
conversion, and
photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
conversion (sunlight to electricity). The U.S. Energy Independence and Security Act of 2007 created 2008 through 2012 funding for a new solar air conditioning research and development program, which should develop and demonstrate multiple new technology innovations and
mass production Mass production, also known as flow production or continuous production, is the production of substantial amounts of standardized products in a constant flow, including and especially on assembly lines. Together with job production and batch ...
economies of scale In microeconomics, economies of scale are the cost advantages that enterprises obtain due to their scale of operation, and are typically measured by the amount of output produced per unit of time. A decrease in cost per unit of output enables ...
.


History

In the late 19th century, the most common fluid for absorption cooling was a solution of
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
and water. Today, the combination of
lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...
bromide A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retardant ...
and water is also in common use. One end of the system of expansion/condensation pipes is heated, and the other end gets cold enough to make ice. Originally, natural gas was used as a heat source in the late 19th century. Today,
propane Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used a ...
is used in recreational vehicle absorption chiller refrigerators. Hot water solar thermal energy collectors can also be used as the modern "free energy" heat source. A National Aeronautics and Space Administration (NASA) sponsored report in 1976 surveyed solar energy system applications of air conditioning. Techniques discussed included both solar powered (absorption cycle and heat engine /
Rankine cycle The Rankine cycle is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat sourc ...
) and solar related (heat pump) along with an extensive bibliography of related literature.


Photovoltaic (PV) solar cooling

Photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
can provide either indirect solar air conditioning power or, now, directly power to air conditioners.  Indirect photovoltaic power for air conditioners consists of whole-house or whole-building solar which, traditionally for most users, has also meant net metering to the grid.  Solar in this case is inverted to
alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...
(AC) to run the appliances in the house or building, including the air conditioner(s).  The advantage of this is the air conditioners don’t need any special electronics to accommodate solar, so it’s a simple implementation.  The disadvantage is that these air conditioners usually have a
SEER In the United States, 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, a trade association, in its 2008 standard AHR ...
value of 14 or less, and the supplied solar has some loss from the power conversion of DC (
direct current Direct current (DC) is one-directional flow of electric charge. An electrochemical cell is a prime example of DC power. Direct current may flow through a conductor such as a wire, but can also flow through semiconductors, insulators, or even ...
) solar to AC even before it reaches the air conditioners.  Another disadvantage is that these air conditioners cannot run when the grid is down, since, in effect, the net-metered home or building is a node on the grid, and utilities need to prevent backfeeding power into a dead grid when the grid’s down. And, now, air conditioners, like many home appliances (e.g., TVs, computers) are beginning to run on DC power.  So, whole-building solar for such units needs to be inverted to alternating current, and then rectified back to direct current, further increasing inefficiencies. Off-grid solar arrays instead use batteries to supply whole-house or whole-building solar.  Such systems employ a voltage controller to manage battery charging, and then the battery power is inverted to provide alternating current for the home or building.  Since they’re not grid tied or net metered, they can operate after a storm or other event brings down grid power.  However, the power, once again, must be converted from DC from the solar panels and batteries to AC by inversion to run power remotely to the appliances. More recently, true solar-powered photovoltaic air conditioners heat pumps have been developed.  Such units run using DC power, and, as such, they can and do make use of the inherent DC power generated by photovoltaic solar panels.  One mini split version of this units employs a 48v DC power bus and a 48v battery array, usually 4 x 12v batteries in series (e.g.
Hotspot Energy
.  Unlike the whole-house battery system, though, these batteries only run the air conditioner. The advantage of these systems is that, with enough solar and battery capacity, they can run at night or when it’s cloudy.  Another mini split version allows the solar panels to be plugged directly to the outside part of the unit, uses a 310v DC power bus, and offers optional 120v plug-in backup grid power
Airspool
to be leveraged to fill in any lack of solar power available. The advantage of these inverter DC air conditioners is the lower cost, while the disadvantage is that they have no way to run without solar unless they're plugged in. Both of these systems make use
variable refrigerant flow Variable refrigerant flow (VRF), also known as variable refrigerant volume (VRV), is an HVAC technology invented by Daikin Industries, Ltd. in 1982. Like ductless minisplits, VRFs use refrigerant as the cooling and heating medium. This refrigera ...
technology, with high-efficiency variable-speed DC motors and compressors to require very little run power, and both also offer heat in addition to air conditioning.  A third type of unit is available for larger, usually commercial, buildings and offers both grid and battery backup as well as optional net metering. Like the two smaller units, these units are VRF, but unlike them, there’s an option to run heating in one part of the building and air conditioning in another part, making use of one outside/condensing unit and multiple inside/evaporative units located in different areas of the building to condition that areas based on specific user needs. Photovoltaic can be combined with geothermal technology, too.  An efficient geothermal air conditioning system would require a smaller, less-expensive photovoltaic system. A high-quality
geothermal heat pump A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that uses a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through ...
installation can have a
SEER In the United States, 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, a trade association, in its 2008 standard AHR ...
in the range of 20 (±). A 29 kW (100,000 BTU/h) SEER 20 air conditioner would require less than 5 kW while operating. There are also new non-compressor-based electrical air conditioning systems with a SEER above 20 coming on the market. New versions of phase-change indirect evaporative coolers use nothing but a fan and a supply of water to cool buildings without adding extra interior humidity (such as at McCarran Airport Las Vegas Nevada). In dry arid climates with relative humidity below 45% (about 40% of the continental U.S.) indirect evaporative coolers can achieve a SEER above 20, and up to SEER 40. A 29 kW (100,000 BTU/h) indirect evaporative cooler would only need enough photovoltaic power for the circulation fan (plus a water supply). A less-expensive partial-power photovoltaic system can reduce (but not eliminate) the monthly amount of electricity purchased from the
power grid An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
for air conditioning (and other uses). With American state government subsidies of $2.50 to US$5.00 per photovoltaic watt, the amortized cost of PV-generated electricity can be below $0.15 per kWh. This is currently cost effective in some areas where power company electricity is now $0.15 or more. Excess PV power generated when air conditioning is not required can be sold to the
power grid An electrical grid is an interconnected network for electricity delivery from producers to consumers. Electrical grids vary in size and can cover whole countries or continents. It consists of:Kaplan, S. M. (2009). Smart Grid. Electrical Power ...
in many locations, which can reduce or eliminate annual net electricity purchase requirement. (See
Zero-energy building A Zero Energy Building (ZEB), also known as a Net Zero Energy (NZE) building, is a building with net zero energy consumption, meaning the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy ...
) Superior
energy efficiency Energy efficiency may refer to: * Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process ** Electrical efficiency, useful power output per electrical power consumed ** Mechanical efficiency, a ra ...
can be designed into new construction (or retrofitted to existing buildings). Since the U.S. Department of Energy was created in 1977, their
Weatherization Assistance Program The Low Income Home Energy Assistance Program (LIHEAP, pronounced "lie" "heap") is a United States federal social services program first established in 1981 and funded annually through Congressional appropriations. The mission of LIHEAP is to as ...
has reduced heating-and-cooling load on 5.5 million low-income affordable homes an average of 31%. A hundred million American buildings still need improved weatherization. Careless conventional construction practices are still producing inefficient new buildings that need weatherization when they are first occupied.


Geothermal cooling

Earth sheltering An earth shelter, also called an earth house, earth bermed house, or underground house, is a structure (usually a house) with earth (soil) against the walls, on the roof, or that is entirely buried underground. Earth acts as thermal mass, making ...
or
earth cooling tubes A ground-coupled heat exchanger is an underground heat exchanger that can capture heat from and/or dissipate heat to the ground. They use the Earth's near constant subterranean temperature to warm or cool air or other fluids for residential, agric ...
can take advantage of the ambient temperature of the earth to reduce or eliminate conventional air conditioning requirements. In many climates where the majority of humans live, they can greatly reduce the buildup of undesirable summer heat, and also help remove heat from the interior of the building. They increase construction cost, but reduce or eliminate the cost of conventional air conditioning equipment. Earth cooling tubes are not cost effective in hot humid tropical environments where the ambient Earth temperature approaches human temperature comfort zone. A
solar chimney :''This article refers to a device for ventilation. For the power generation technology, see Solar updraft tower.'' A solar chimney often referred to as a thermal chimney is a way of improving the natural ventilation of buildings by using convect ...
or
photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
-powered fan can be used to exhaust undesired heat and draw in cooler, dehumidified air that has passed by ambient Earth temperature surfaces. Control of humidity and condensation are important design issues. A
geothermal heat pump A ground source heat pump (also geothermal heat pump) is a heating/cooling system for buildings that uses a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through ...
uses ambient earth temperature to improve SEER for heat and cooling. A deep well recirculates water to extract ambient earth temperature, typically at of water per metric ton per minute. These "open loop" systems were the most common in early systems, however water quality could cause damage to the coils in the heat pump and shorten the life of the equipment. Another method is a closed loop system, in which a loop of tubing is run down a well or wells, or in trenches in the lawn, to cool an intermediate fluid. When wells are used, they are back-filled with bentonite grout or another grout material to ensure good thermal conductivity to the earth. In the past the fluid of choice was a 50/50 mixture of propylene glycol because it is non-toxic unlike ethylene glycol (which is used in car radiators). Propylene glycol is viscous, and would eventually gum up some parts in the loop(s), so it has fallen out of favor. Today , the most common transfer agent is a mixture of water and ethyl alcohol (ethanol). Ambient earth temperature is much lower than peak summer air temperature, and much higher than the lowest extreme winter air temperature. Water is 25 times more thermally conductive than air, so it is much more efficient than an outside air heat pump, (which becomes less effective when the outside temperature drops in winter). The same type of geothermal well can be used without a heat pump but with greatly diminished results. Ambient earth temperature water is pumped through a shrouded radiator (like an automobile radiator). Air is blown across the radiator, which cools without a compressor-based air conditioner. Photovoltaic solar electric panels produce electricity for the water pump and fan, eliminating conventional air-conditioning utility bills. This concept is cost-effective, as long as the location has ambient earth temperature below the human thermal comfort zone (not the tropics).


Solar open-loop air conditioning using desiccants

Air can be passed over common, solid desiccants (like
silica gel Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other l ...
or
zeolite Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ・y where is either a metal ion or H+. These pos ...
) or liquid desiccants (like lithium bromide/chloride) to draw moisture from the air to allow an efficient mechanical or
evaporative cooling An evaporative cooler (also known as evaporative air conditioner, swamp cooler, swamp box, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning sy ...
cycle. The desiccant is then regenerated by using
solar thermal energy Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to generate thermal energy for use in industry, and in the residential and commercial sectors. Solar thermal collectors are classified by the United St ...
to dehumidify, in a cost-effective, low-energy-consumption, continuously repeating cycle. A
photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
system can power a low-energy air circulation fan, and a motor to slowly rotate a large disk filled with desiccant.
Energy recovery ventilation Energy recovery ventilation (ERV) is the energy recovery process in residential and commercial HVAC systems that exchanges the energy contained in normally exhausted air of a building or conditioned space, using it to treat (precondition) the in ...
systems provide a controlled way of ventilating a home while minimizing energy loss. Air is passed through an " enthalpy wheel" (often using silica gel) to reduce the cost of heating ventilated air in the winter by transferring heat from the warm inside air being exhausted to the fresh (but cold) supply air. In the summer, the inside air cools the warmer incoming supply air to reduce ventilation cooling costs. This low-energy fan-and-motor ventilation system can be cost-effectively powered by
photovoltaics Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
, with enhanced natural
convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...
exhaust up a
solar chimney :''This article refers to a device for ventilation. For the power generation technology, see Solar updraft tower.'' A solar chimney often referred to as a thermal chimney is a way of improving the natural ventilation of buildings by using convect ...
- the downward incoming air flow would be forced convection (
advection In the field of physics, engineering, and earth sciences, advection is the transport of a substance or quantity by bulk motion of a fluid. The properties of that substance are carried with it. Generally the majority of the advected substance is al ...
). A desiccant like
calcium chloride Calcium chloride is an inorganic compound, a salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide. Ca ...
can be mixed with water to create a recirculating waterfall that dehumidifies a room using solar thermal energy to regenerate the liquid, and a PV-powered low-rate water pump to circulate liquid. Active solar cooling wherein solar thermal collectors provide input energy for a desiccant cooling system. There are several commercially available systems that blow air through a desiccant impregnated medium for both the dehumidification and the regeneration cycle. The solar heat is one way that the regeneration cycle is powered. In theory packed towers can be used to form a
counter-current flow Countercurrent exchange is a mechanism occurring in nature and mimicked in industry and engineering, in which there is a crossover of some property, usually heat or some chemical, between two flowing bodies flowing in opposite directions to each ...
of the air and the liquid desiccant but are not normally employed in commercially available machines. Preheating of the air is shown to greatly enhance desiccant regeneration. The packed column yields good results as a dehumidifier/regenerator, provided pressure drop can be reduced with the use of suitable packing.


Passive solar cooling

In this type of cooling solar thermal energy is not used directly to create a cold environment or drive any direct cooling processes. Instead, solar building design aims at slowing the rate of
heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...
into a building in the summer, and improving the removal of unwanted heat. It involves a good understanding of the mechanisms of
heat transfer Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...
:
heat conduction Conduction is the process by which heat is transferred from the hotter end to the colder end of an object. The ability of the object to conduct heat is known as its ''thermal conductivity'', and is denoted . Heat spontaneously flows along a te ...
,
convective heat transfer Convection (or convective heat transfer) is the heat transfer, transfer of heat from one place to another due to the movement of fluid. Although often discussed as a distinct method of heat transfer, convective heat transfer involves the combin ...
, and
thermal radiation Thermal radiation is electromagnetic radiation generated by the thermal motion of particles in matter. Thermal radiation is generated when heat from the movement of charges in the material (electrons and protons in common forms of matter) is ...
, the latter primarily from the sun. For example, a sign of poor thermal design is an attic that gets hotter in summer than the peak outside air temperature. This can be significantly reduced or eliminated with a
cool roof Reflective surfaces or ground-based albedo modification (GBAM) is a solar radiation management method of enhancing the Earth's albedo (the ability to reflect the visible, infrared and ultraviolet wavelengths of the sun, reducing heat transfer to ...
or a
green roof A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage ...
, which can reduce the roof surface temperature by 70 °F (40 °C) in summer. A
radiant barrier A radiant barrier is a type of building material that reflects thermal radiation and reduces heat transfer. Because thermal energy is also transferred by conduction and convection, in addition radiation, radiant barriers are often supplemented wit ...
and an air gap below the roof will block about 97% of downward radiation from roof cladding heated by the sun. Passive solar cooling is much easier to achieve in new construction than by adapting existing buildings. There are many design specifics involved in passive solar cooling. It is a primary element of designing a
zero energy building A Zero Energy Building (ZEB), also known as a Net Zero Energy (NZE) building, is a building with net zero energy consumption, meaning the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy c ...
in a hot climate.


Solar closed-loop absorption cooling

Closed-loop air conditioning commonly uses the following materials for water-based absorption: *
Ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous was ...
* Lithium Bromide * Lithium Chloride * Silica Gel * Zeolite An alternative to water-based systems is to use methanol with activated carbon. Active solar cooling uses solar thermal collectors to provide solar energy to thermally driven chillers (usually adsorption or absorption chillers). Solar energy heats a fluid that provides heat to the generator of an absorption chiller and is recirculated back to the collectors. The heat provided to the generator drives a cooling cycle that produces chilled water. The chilled water produced is used for large commercial and industrial cooling.
Solar thermal energy Solar thermal energy (STE) is a form of energy and a technology for harnessing solar energy to generate thermal energy for use in industry, and in the residential and commercial sectors. Solar thermal collectors are classified by the United St ...
can be used to efficiently cool in the summer, and also heat domestic hot water and buildings in the winter. Single, double or triple iterative absorption cooling cycles are used in different solar-thermal-cooling system designs. The more cycles, the more efficient they are. Absorption chillers operate with less noise and vibration than compressor-based chillers, but their capital costs are relatively high. Efficient absorption chillers nominally require water of at least . Common, inexpensive flat-plate
solar thermal collector A solar thermal collector collects heat by absorbing sunlight. The term "solar collector" commonly refers to a device for solar hot water heating, but may refer to large power generating installations such as solar parabolic troughs and sola ...
s only produce about water. High temperature flat plate, concentrating (CSP) or evacuated tube collectors are needed to produce the higher temperature transfer fluids required. In large scale installations there are several projects successful both technical and economical in operation worldwide including, for example, at the headquarters of
Caixa Geral de Depósitos Caixa Geral de Depósitos (CGD) () is a Portuguese state-owned banking corporation, and the largest bank in Portugal, established in Lisbon in 1876. CGD now has presence in 23 countries spanning four continents through branches, representative ...
in Lisbon with solar collectors and 545 kW cooling power or on the Olympic Sailing Village in Qingdao/China. In 2011 the most powerful plant at Singapore's new constructed
United World College United World Colleges (UWC) is an international network of schools and educational programmes with the shared aim of "making education a force to unite people, nations and cultures for peace and a sustainable future." The organization was founde ...
will be commissioned (1500 kW). These projects have shown that flat plate solar collectors specially developed for temperatures over (featuring double glazing, increased backside insulation, etc.) can be effective and cost-efficient. Where water can be heated well above , it can be stored and used when the sun is not shining. The Audubon Environmental Center at the Ernest E. Debs Regional Park in Los Angeles has an example solar air conditioning installation, which failed fairly soon after commissioning and is no longer being maintained. The
Southern California Gas The Southern California Gas Company (trading as SoCalGas) is a utility company based in Los Angeles, California, and a subsidiary of Sempra Energy. It is the primary provider of natural gas to Los Angeles and Southern California. Overview Its ...
Co. (The Gas Company) is also testing the practicality of solar thermal cooling systems at their Energy Resource Center (ERC) in
Downey, California Downey is a city located in Southeast Los Angeles County, California, United States, southeast of downtown Los Angeles. It is considered part of the Gateway Cities. The city is the birthplace of the Apollo space program. It is also the home of ...
. Solar Collectors from
Sopogy Sopogy was a solar thermal technology supplier founded in 2002 at the Honolulu, Hawaii-based clean technology incubator known as Energy Laboratories. The company began its research on concentrating solar thermal energy to produce solar steam and t ...
and Cogenra were installed on the rooftop at the ERC and are producing cooling for the building's air conditioning system.
Masdar City Masdar City ( ar, مدينة مصدر, Madīnat Maṣdar, lit=Source City) is a planned city project in Abu Dhabi, in the United Arab Emirates. Its core is being built by Masdar, a subsidiary of Mubadala Development Company, with the majority ...
in the
United Arab Emirates The United Arab Emirates (UAE; ar, اَلْإِمَارَات الْعَرَبِيَة الْمُتَحِدَة ), or simply the Emirates ( ar, الِْإمَارَات ), is a country in Western Asia (The Middle East). It is located at th ...
is also testing a double-effect absorption cooling plant using
Sopogy Sopogy was a solar thermal technology supplier founded in 2002 at the Honolulu, Hawaii-based clean technology incubator known as Energy Laboratories. The company began its research on concentrating solar thermal energy to produce solar steam and t ...
parabolic trough collectors, Mirroxx Fresnel array and TVP Solar high-vacuum solar thermal panels. A
FedEx Ground FedEx Ground, a subsidiary of the FedEx Corporation, is an American ground package delivery company headquartered in Moon Township, Pennsylvania, a suburb of Pittsburgh. The company began as Roadway Package System (RPS), founded in 1985 by t ...
sorting facility in
Davenport, Florida Davenport is a city in Polk County, Florida, United States. The population was 9,040 at the 2020 census. While the city of Davenport itself is very small, the area north of the city close to Interstate 4 and US 27 is experiencing explosive growth ...
uses a solar thermal air conditioning system to feed cool air into truck trailers parked at loading doors. For 150 years, absorption chillers have been used to make ice (before the electric light bulbs were invented). This ice can be stored and used as an "ice battery" for cooling when the sun is not shining, as it was in the 1995
Hotel New Otani Tokyo The Hotel New Otani Tokyo is a large hotel located in Tokyo, Japan operated by New Otani Hotels and opened in 1964. The hotel currently has 1,479 rooms and 39 restaurants. It has hosted numerous heads of state and is home to a 400-year-old gar ...
in Japan. Mathematical models are available in the public domain for ice-based thermal energy storage performance calculations. The ISAAC Solar Icemaker is an intermittent solar ammonia-water absorption cycle. The ISAAC uses a
parabolic trough A parabolic trough is a type of solar thermal collector that is straight in one dimension and curved as a parabola in the other two, lined with a polished metal mirror. The sunlight which enters the mirror parallel to its plane of symmetry is foc ...
solar collector with a compact and efficient design to produce ice with no fuel or electric input, as well as with no moving parts.


Solar cooling systems utilizing concentrating collectors

The main reasons for employing concentrating collectors in solar cooling systems are: high efficient air-conditioning through coupling with double/triple effect chillers; and solar refrigeration serving industrial end-users, possibly in combination with process heat and steam. Concerning industrial applications, several studies in the recent years highlighted that there is a high potential for refrigeration (temperatures below 0 °C) in different areas of the globe (e.g., the Mediterranean, Central America). However, this can be achieved by ammonia/ water absorption chillers requiring high temperature heat input at the generator, in a range (120 ÷ 180 °C) which can only be satisfied by concentrating solar collectors. Moreover, several industrial applications require both cooling and steam for processes, and concentrating solar collectors can be very advantageous in the sense that their use is maximized


Zero-energy buildings

Goals of
zero-energy building A Zero Energy Building (ZEB), also known as a Net Zero Energy (NZE) building, is a building with net zero energy consumption, meaning the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy ...
s include
sustainable Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livin ...
,
green building Green building (also known as green construction or sustainable building) refers to both a structure and the application of processes that are environmentally responsible and resource-efficient throughout a building's life-cycle: from planni ...
technologies that can significantly reduce, or eliminate, net annual energy bills. The supreme achievement is the totally
off-the-grid Off-the-grid or off-grid is a characteristic of buildings and a lifestyle designed in an independent manner without reliance on one or more public utilities. The term "off-the-grid" traditionally refers to not being connected to the electrical gr ...
autonomous building An autonomous building is a building designed to be operated independently from infrastructural support services such as the electric power grid, gas grid, municipal water systems, sewage treatment systems, storm drains, communication services, ...
that does not have to be connected to utility companies. In hot climates with significant
degree day A degree day is a measure of heating or cooling. Total degree days from an appropriate starting date are used to plan the planting of crops and management of pests and pest control timing. Weekly or monthly degree-day figures may also be used wi ...
s of cooling requirement, leading-edge solar air conditioning will be an increasingly important
critical success factor Critical success factor (CSF) is a management term for an element that is necessary for an organization or project to achieve its mission. To achieve their goals they need to be aware of each key success factor (KSF) and the variations between the ...
.


See also

*
Passive house "Passive house" (german: Passivhaus) is a voluntary standard for energy efficiency in a building, which reduces the building's ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or coo ...
*
Passive solar building design In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design because, unli ...
*
Solar powered refrigerator A solar-powered refrigerator is a refrigerator which runs on energy directly provided by sun, and may include photovoltaic or solar thermal energy. Solar-powered refrigerators are able to keep perishable goods such as meat and dairy cool in hot ...


Notes


References


External links


Cooling with Solar Heat: Growing Interest in Solar Air Conditioning
{{DEFAULTSORT:Solar Air Conditioning Chemical processes Heating, ventilation, and air conditioning Solar architecture Solar thermal energy Renewable energy