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118-409: The firm of Bridgers & Paxton Consulting Engineers was founded in 1951 by Frank Bridgers (1922–2005) and Donald Paxton (1912–2007), both of whom were interested in the potential applications of solar energy . Initially operating out of a garage behind Bridgers' house, the two men conceived a new office building for their firm which would include an experimental solar heating system. They believed such

236-936: A 1,300 m (14,000 sq ft) collector in Coimbatore , India, used for drying marigolds. Solar distillation can be used to make saline or brackish water potable. The first recorded instance of this was by 16th-century Arab alchemists. A large-scale solar distillation project was first constructed in 1872 in the Chilean mining town of Las Salinas. The plant, which had solar collection area of 4,700 m (51,000 sq ft), could produce up to 22,700 L (5,000 imp gal; 6,000 US gal) per day and operate for 40 years. Individual still designs include single-slope, double-slope (or greenhouse type), vertical, conical, inverted absorber, multi-wick, and multiple effect. These stills can operate in passive, active, or hybrid modes. Double-slope stills are

354-528: A SCOP of 4.62 will give over 4kW of energy into a heating system for every kilowatt of energy that the heat pump uses itself to operate. When used for space heating, heat pumps are typically more energy-efficient than electric resistance and other heaters. Because of their high efficiency and the increasing share of fossil-free sources in electrical grids, heat pumps are playing a key role in climate change mitigation . Consuming 1 kWh of electricity, they can transfer 1 to 4.5 kWh of thermal energy into

472-422: A building is: W = Q C O P {\displaystyle W={\frac {Q}{\mathrm {COP} }}} where The coefficient of performance of a heat pump is greater than one so the work required is less than the heat transferred, making a heat pump a more efficient form of heating than electrical resistance heating. As the temperature of the higher-temperature reservoir increases in response to

590-523: A building. The carbon footprint of heat pumps depends on how electricity is generated , but they usually reduce emissions. Heat pumps could satisfy over 80% of global space and water heating needs with a lower carbon footprint than gas-fired condensing boilers : however, in 2021 they only met 10%. Heat flows spontaneously from a region of higher temperature to a region of lower temperature. Heat does not flow spontaneously from lower temperature to higher, but it can be made to flow in this direction if work

708-535: A conventional steam-generator to produce superheated steam for a turbine/generator as used in any conventional coal, oil, or nuclear power plant. A 100-megawatt turbine would need a tank about 9.1 metres (30 ft) tall and 24 metres (79 ft) in diameter to drive it for four hours by this design. Several parabolic trough power plants in Spain and solar power tower developer SolarReserve use this thermal energy storage concept. The Solana Generating Station in

826-634: A cooking container. These cookers reach temperatures of 315 °C (599 °F) and above but require direct light to function properly and must be repositioned to track the Sun. Solar concentrating technologies such as parabolic dish, trough and Scheffler reflectors can provide process heat for commercial and industrial applications. The first commercial system was the Solar Total Energy Project (STEP) in Shenandoah, Georgia, US where

944-439: A fan and the other which either directly heats the air inside the building or heats water which is then circulated around the building through radiators or underfloor heating which releases the heat to the building. These devices can also operate in a cooling mode where they extract heat via the internal heat exchanger and eject it into the ambient air using the external heat exchanger. Some can be used to heat water for washing which

1062-494: A field of 114 parabolic dishes provided 50% of the process heating, air conditioning and electrical requirements for a clothing factory. This grid-connected cogeneration system provided 400 kW of electricity plus thermal energy in the form of 401 kW steam and 468 kW chilled water and had a one-hour peak load thermal storage. Evaporation ponds are shallow pools that concentrate dissolved solids through evaporation . The use of evaporation ponds to obtain salt from seawater

1180-413: A flow temperature up to 80 °C (176 °F). As of 2023 about 10% of building heating worldwide is from ASHPs. They are the main way to phase out gas boilers (also known as "furnaces") from houses, to avoid their greenhouse gas emissions . Air-source heat pumps are used to move heat between two heat exchangers, one outside the building which is fitted with fins through which air is forced using

1298-490: A fuel in a boiler/furnace or by use of resistive electric heaters . Exhaust air heat pumps extract heat from the exhaust air of a building and require mechanical ventilation . Two classes exist: A solar-assisted heat pump (SAHP) is a machine that combines a heat pump and thermal solar panels and/or PV solar panels in a single integrated system. Typically these two technologies are used separately (or only placing them in parallel) to produce hot water . In this system

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1416-475: A full-scale steam engine powered by low-pressure water, enabling him to patent the entire solar engine system by 1912. Shuman built the world's first solar thermal power station in Maadi , Egypt , between 1912 and 1913. His plant used parabolic troughs to power a 45–52 kilowatts (60–70  hp ) engine that pumped more than 22,000 litres (4,800 imp gal; 5,800 US gal) of water per minute from

1534-403: A heat pump is typically a vapor-compression refrigeration device that includes a reversing valve and optimized heat exchangers so that the direction of heat flow (thermal energy movement) may be reversed. The reversing valve switches the direction of refrigerant through the cycle and therefore the heat pump may deliver either heating or cooling to a building. Because the two heat exchangers,

1652-564: A high altitude, where the temperature is low, water vapor condenses into clouds, which rain onto the Earth's surface, completing the water cycle . The latent heat of water condensation amplifies convection, producing atmospheric phenomena such as wind, cyclones and anticyclones . Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of 14 °C. By photosynthesis , green plants convert solar energy into chemically stored energy, which produces food, wood and

1770-405: A high reduction of CO 2 emissions (in some cases more than 50%). Industrial heat pumps can heat up to 200 °C, and can meet the heating demands of many light industries . In Europe alone, 15 GW of heat pumps could be installed in 3,000 facilities in the paper, food and chemicals industries. The performance of a heat pump is determined by the ability of the pump to extract heat from

1888-417: A higher pressure, resulting in a higher temperature as well. The hot, compressed vapor is then in the thermodynamic state known as a superheated vapor and it is at a temperature and pressure at which it can be condensed with either cooling water or cooling air flowing across the coil or tubes. In heating mode this heat is used to heat the building using the internal heat exchanger, and in cooling mode this heat

2006-572: A large area of sunlight to a hot spot, often to drive a steam turbine . Photovoltaics (PV) were initially solely used as a source of electricity for small and medium-sized applications, from the calculator powered by a single solar cell to remote homes powered by an off-grid rooftop PV system. Commercial concentrated solar power plants were first developed in the 1980s. Since then, as the cost of solar panels has fallen, grid-connected solar PV systems ' capacity and production has doubled about every three years . Three-quarters of new generation capacity

2124-402: A low temperature environment (the source ) and deliver it to a higher temperature environment (the sink ). Performance varies, depending on installation details, temperature differences, site elevation, location on site, pipe runs, flow rates, and maintenance. In general, heat pumps work most efficiently (that is, the heat output produced for a given energy input) when the difference between

2242-416: A narrow, continuous band of windows running just below the roofline which light the drafting room, while the street-facing eastern elevation is windowless brick. The south wing is a low, flat-roofed structure containing office space. It is partially faced with brick, marking the original extent of the building; it was later extended with an addition in 1962. The main entrance is positioned at the intersection of

2360-450: A number of national publications including Architectural Forum , Life , Architectural Record , Progressive Architecture , and Popular Mechanics , and directly inspired a number of subsequent active solar heating systems. Despite some minor problems, the building's heating system operated successfully for six years, even during the particularly cold and cloudy month of January 1957, which recorded only three sunny days. However, it

2478-538: A portion of this energy. Use of solar for heating can roughly be divided into passive solar concepts and active solar concepts, depending on whether active elements such as sun tracking and solar concentrator optics are used. Thermal mass is any material that can be used to store heat—heat from the Sun in the case of solar energy. Common thermal mass materials include stone, cement, and water. Historically they have been used in arid climates or warm temperate regions to keep buildings cool by absorbing solar energy during

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2596-512: A reference to the energy retained by storing heat before turning it into electricity, versus converting heat directly into electricity. The molten salt mixtures vary. The most extended mixture contains sodium nitrate , potassium nitrate and calcium nitrate . It is non-flammable and non-toxic, and has already been used in the chemical and metals industries as a heat-transport fluid. Hence, experience with such systems exists in non-solar applications. The salt melts at 131 °C (268 °F). It

2714-527: A sealed chamber driven by a loudspeaker to achieve a temperature difference across the chamber. Electrocaloric heat pumps are solid state. The International Energy Agency estimated that, as of 2021, heat pumps installed in buildings have a combined capacity of more than 1000 GW. They are used for heating, ventilation, and air conditioning (HVAC) and may also provide domestic hot water and tumble clothes drying. The purchase costs are supported in various countries by consumer rebates. In HVAC applications,

2832-412: A small part in the near-ultraviolet . Most of the world's population live in areas with insolation levels of 150–300 watts/m , or 3.5–7.0 kWh /m per day. Solar radiation is absorbed by the Earth's land surface, oceans – which cover about 71% of the globe – and atmosphere. Warm air containing evaporated water from the oceans rises, causing atmospheric circulation or convection . When the air reaches

2950-406: A smaller footprint than window mounted air conditioners that just do cooling. In water heating applications, heat pumps may be used to heat or preheat water for swimming pools, homes or industry. Usually heat is extracted from outdoor air and transferred to an indoor water tank. Large (megawatt-scale) heat pumps are used for district heating . However as of 2022 about 90% of district heat

3068-488: A steam engine. In 1908 Shuman formed the Sun Power Company with the intent of building larger solar power plants. He, along with his technical advisor A.S.E. Ackermann and British physicist Sir Charles Vernon Boys , developed an improved system using mirrors to reflect solar energy upon collector boxes, increasing heating capacity to the extent that water could now be used instead of ether. Shuman then constructed

3186-548: A system would not only save money, but would also allow them to collect valuable data for future projects. In 1954, they were able to put some of their ideas into practice with an innovative heating and cooling system for the Simms Building , which took advantage of the building's south-facing glass curtain wall to provide solar heating in winter. However, additional heating or cooling was still required under most conditions. Bridgers and Paxton began serious design work on

3304-442: A tenth of their electricity from solar, with China making up more than half of solar growth. Almost half the solar power installed in 2022 was mounted on rooftops . Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. The concentrated heat is then used as a heat source for a conventional power plant. A wide range of concentrating technologies exists;

3422-422: Is a biannual solar-powered car race, where teams from universities and enterprises compete over 3,021 kilometres (1,877 mi) across central Australia from Darwin to Adelaide . In 1987, when it was founded, the winner's average speed was 67 kilometres per hour (42 mph) and by 2007 the winner's average speed had improved to 90.87 kilometres per hour (56.46 mph). The North American Solar Challenge and

3540-439: Is a classic example of passive solar design. The most recent approaches to solar design use computer modeling tying together solar lighting , heating and ventilation systems in an integrated solar design package. Active solar equipment such as pumps, fans, and switchable windows can complement passive design and improve system performance. Urban heat islands (UHI) are metropolitan areas with higher temperatures than that of

3658-409: Is a device that consumes energy (usually electricity) to transfer heat from a cold heat sink to a hot heat sink. Specifically, the heat pump transfers thermal energy using a refrigeration cycle , cooling the cool space and warming the warm space. In cold weather, a heat pump can move heat from the cool outdoors to warm a house (e.g. winter); the pump may also be designed to move heat from the house to

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3776-525: Is a heating/cooling system for buildings that use a type of heat pump to transfer heat to or from the ground, taking advantage of the relative constancy of temperatures of the earth through the seasons. Ground-source heat pumps (GSHPs) – or geothermal heat pumps (GHP), as they are commonly termed in North America – are among the most energy-efficient technologies for providing HVAC and water heating , using far less energy than can be achieved by burning

3894-450: Is a passive solar ventilation system composed of a vertical shaft connecting the interior and exterior of a building. As the chimney warms, the air inside is heated, causing an updraft that pulls air through the building. Performance can be improved by using glazing and thermal mass materials in a way that mimics greenhouses. Deciduous trees and plants have been promoted as a means of controlling solar heating and cooling. When planted on

4012-441: Is challenging; a feasible alternative is hydrogen production from protons, though use of water as the source of electrons (as plants do) requires mastering the multielectron oxidation of two water molecules to molecular oxygen. Some have envisaged working solar fuel plants in coastal metropolitan areas by 2050 – the splitting of seawater providing hydrogen to be run through adjacent fuel-cell electric power plants and

4130-455: Is expected to be available before the 2030s or 2040s. Vapor-compression uses a circulating refrigerant as the medium which absorbs heat from one space, compresses it thereby increasing its temperature before releasing it in another space. The system normally has eight main components: a compressor , a reservoir, a reversing valve which selects between heating and cooling mode, two thermal expansion valves (one used when in heating mode and

4248-575: Is from fossil fuels . In Europe, heat pumps account for a mere 1% of heat supply in district heating networks but several countries have targets to decarbonise their networks between 2030 and 2040. Possible sources of heat for such applications are sewage water, ambient water (e.g. sea, lake and river water), industrial waste heat , geothermal energy , flue gas , waste heat from district cooling and heat from solar seasonal thermal energy storage . Large-scale heat pumps for district heating combined with thermal energy storage offer high flexibility for

4366-763: Is generally limited to the toy market as the surface-area to payload-weight ratio is relatively high. The Squad Solar is a Neighborhood Electric Vehicle that has a solar roof and can be plugged into a normal 120 volt outlet to be charged. Solar chemical processes use solar energy to drive chemical reactions. These processes offset energy that would otherwise come from a fossil fuel source and can also convert solar energy into storable and transportable fuels. Solar induced chemical reactions can be divided into thermochemical or photochemical . A variety of fuels can be produced by artificial photosynthesis . The multielectron catalytic chemistry involved in making carbon-based fuels (such as methanol ) from reduction of carbon dioxide

4484-399: Is kept liquid at 288 °C (550 °F) in an insulated "cold" storage tank. The liquid salt is pumped through panels in a solar collector where the focused irradiance heats it to 566 °C (1,051 °F). It is then sent to a hot storage tank. This is so well insulated that the thermal energy can be usefully stored for up to a week. When electricity is needed, the hot salt is pumped to

4602-588: Is one of the oldest applications of solar energy. Modern uses include concentrating brine solutions used in leach mining and removing dissolved solids from waste streams. Clothes lines , clotheshorses , and clothes racks dry clothes through evaporation by wind and sunlight without consuming electricity or gas. In some states of the United States legislation protects the "right to dry" clothes. Unglazed transpired collectors (UTC) are perforated sun-facing walls used for preheating ventilation air. UTCs can raise

4720-405: Is performed. The work required to transfer a given amount of heat is usually much less than the amount of heat; this is the motivation for using heat pumps in applications such as the heating of water and the interior of buildings. The amount of work required to drive an amount of heat Q from a lower-temperature reservoir such as ambient air to a higher-temperature reservoir such as the interior of

4838-566: Is produced. An increasing share of low-carbon energy sources such as wind and solar will lower the impact on the climate. In most settings, heat pumps will reduce CO 2 emissions compared to heating systems powered by fossil fuels . In regions accounting for 70% of world energy consumption , the emissions savings of heat pumps compared with a high-efficiency gas boiler are on average above 45% and reach 80% in countries with cleaner electricity mixes. These values can be improved by 10 percentage points, respectively, with alternative refrigerants. In

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4956-576: Is recommended by the World Health Organization as a viable method for household water treatment and safe storage. Over two million people in developing countries use this method for their daily drinking water. Solar energy may be used in a water stabilization pond to treat waste water without chemicals or electricity. A further environmental advantage is that algae grow in such ponds and consume carbon dioxide in photosynthesis, although algae may produce toxic chemicals that make

5074-411: Is rejected via the external heat exchanger. The condensed, liquid refrigerant, in the thermodynamic state known as a saturated liquid , is next routed through an expansion valve where it undergoes an abrupt reduction in pressure. That pressure reduction results in the adiabatic flash evaporation of a part of the liquid refrigerant. The auto-refrigeration effect of the adiabatic flash evaporation lowers

5192-489: Is solar, with both millions of rooftop installations and gigawatt-scale photovoltaic power stations continuing to be built. In 2023, solar power generated 5.5% (1,631 TWh) of global electricity and over 1% of primary energy , adding twice as much new electricity as coal. Along with onshore wind power , utility-scale solar is the source with the cheapest levelised cost of electricity for new installations in most countries. As of 2023, 33 countries generated more than

5310-399: Is stored in a domestic hot water tank. Air-source heat pumps are relatively easy and inexpensive to install, so are the most widely used type. In mild weather, coefficient of performance (COP) may be between 2 and 5, while at temperatures below around −8 °C (18 °F) an air-source heat pump may still achieve a COP of 1 to 4. A ground source heat pump (also geothermal heat pump)

5428-513: Is the box cooker first built by Horace de Saussure in 1767. A basic box cooker consists of an insulated container with a transparent lid. It can be used effectively with partially overcast skies and will typically reach temperatures of 90–150 °C (194–302 °F). Panel cookers use a reflective panel to direct sunlight onto an insulated container and reach temperatures comparable to box cookers. Reflector cookers use various concentrating geometries (dish, trough, Fresnel mirrors) to focus light on

5546-420: Is the dominant application of solar hot water with an installed capacity of 18 GW th as of 2005. In the United States, heating, ventilation and air conditioning (HVAC) systems account for 30% (4.65 EJ/yr) of the energy used in commercial buildings and nearly 50% (10.1 EJ/yr) of the energy used in residential buildings. Solar heating, cooling and ventilation technologies can be used to offset

5664-726: The Gossamer Penguin made the first piloted flights powered solely by photovoltaics. This was quickly followed by the Solar Challenger which crossed the English Channel in July 1981. In 1990 Eric Scott Raymond in 21 hops flew from California to North Carolina using solar power. Developments then turned back to unmanned aerial vehicles (UAV) with the Pathfinder (1997) and subsequent designs, culminating in

5782-460: The Helios which set the altitude record for a non-rocket-propelled aircraft at 29,524 metres (96,864 ft) in 2001. The Zephyr , developed by BAE Systems , is the latest in a line of record-breaking solar aircraft, making a 54-hour flight in 2007, and month-long flights were envisioned by 2010. From March 2015 to July 2016, Solar Impulse , an electric aircraft , successfully circumnavigated

5900-488: The Nile River to adjacent cotton fields. Although the outbreak of World War I and the discovery of cheap oil in the 1930s discouraged the advancement of solar energy, Shuman's vision, and basic design were resurrected in the 1970s with a new wave of interest in solar thermal energy. In 1916 Shuman was quoted in the media advocating solar energy's utilization, saying: We have proved the commercial profit of sun power in

6018-462: The biomass from which fossil fuels are derived. The total solar energy absorbed by Earth's atmosphere, oceans and land masses is approximately 122 PW·year = 3,850,000  exajoules (EJ) per year. In 2002 (2019), this was more energy in one hour (one hour and 25 minutes) than the world used in one year. Photosynthesis captures approximately 3,000 EJ per year in biomass. The potential solar energy that could be used by humans differs from

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6136-506: The refrigerant enters the evaporator with a lower vapor content. This can be achieved by cooling the liquid refrigerant after condensation. The gaseous refrigerant condenses on the heat exchange surface of the condenser. To achieve a heat flow from the gaseous flow center to the wall of the condenser, the temperature of the liquid refrigerant must be lower than the condensation temperature. Additional subcooling can be achieved by heat exchange between relatively warm liquid refrigerant leaving

6254-554: The Cerro Dominador plant is capable of generating around 110 MW of power. The plant has an advanced storage system enabling it to generate electricity for up to 17.5 hours without direct solar radiation, which allows it to provide a stable electricity supply without interruptions if required. The Project secured up to 950 GW·h per year sale. Another project is the María Elena plant is a 400 MW thermo-solar complex in

6372-563: The Commission Regulation (EU) No. 813/2013. A heat pump's operating performance in cooling mode is characterized in the US by either its energy efficiency ratio (EER) or seasonal energy efficiency ratio (SEER), both of which have units of BTU/(h·W) (note that 1 BTU/(h·W) = 0.293 W/W) and larger values indicate better performance. The carbon footprint of heat pumps depends on their individual efficiency and how electricity

6490-504: The Equator-facing side of a building because they will interfere with winter solar availability. They can, however, be used on the east and west sides to provide a degree of summer shading without appreciably affecting winter solar gain . Solar cookers use sunlight for cooking, drying, and pasteurization . They can be grouped into three broad categories: box cookers, panel cookers, and reflector cookers. The simplest solar cooker

6608-540: The Roman emperor Tiberius . The first modern greenhouses were built in Europe in the 16th century to keep exotic plants brought back from explorations abroad. Greenhouses remain an important part of horticulture today. Plastic transparent materials have also been used to similar effect in polytunnels and row covers . Development of a solar-powered car has been an engineering goal since the 1980s. The World Solar Challenge

6726-525: The Solar Building in early 1954, and it was constructed between March and August 1956. Stanley & Wright were the architects for the building. Its total cost was $ 58,500, of which the heating and cooling system made up about $ 15,000—roughly twice the cost of a conventional system. However, Bridgers and Paxton believed the reduced operating costs would save money in the long run. The novel building attracted considerable attention, receiving write-ups in

6844-407: The Solar Building. In early 1974, Penn State researcher Stanley Gilman received a National Science Foundation grant to restore the building's solar heating system and operate it as part of a multi-year field study intended to identify optimal design criteria for such systems. Following the conclusion of the project, the solar heating system remained in use. Bridgers & Paxton eventually outgrew

6962-499: The Sun. Active solar techniques use photovoltaics, concentrated solar power , solar thermal collectors , pumps, and fans to convert sunlight into useful output. Passive solar techniques include selecting materials with favorable thermal properties, designing spaces that naturally circulate air, and referencing the position of a building to the Sun. Active solar technologies increase the supply of energy and are considered supply side technologies, while passive solar technologies reduce

7080-462: The U.S. has six hours of storage by molten salt. In Chile, The Cerro Dominador power plant has a 110 MW solar-thermal tower, the heat is transferred to molten salts . The molten salts then transfer their heat in a heat exchanger to water, generating superheated steam, which feeds a turbine that transforms the kinetic energy of the steam into electric energy using the Rankine cycle . In this way,

7198-513: The US) or Seasonal Performance Factor (in Europe) are ratings of heating performance. The SPF is Total heat output per annum / Total electricity consumed per annum in other words the average heating COP over the year. Window mounted heat pumps run on standard 120v AC outlets and provide heating, cooling, and humidity control. They are more efficient with lower noise levels, condensation management, and

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7316-462: The United States, 70% of houses could reduce emissions by installing a heat pump. The rising share of renewable electricity generation in many countries is set to increase the emissions savings from heat pumps over time. Heating systems powered by green hydrogen are also low-carbon and may become competitors, but are much less efficient due to the energy loss associated with hydrogen conversion, transport and use. In addition, not enough green hydrogen

7434-657: The Universal Exposition in Paris, Augustin Mouchot successfully demonstrated a solar steam engine but could not continue development because of cheap coal and other factors. In 1897, Frank Shuman , a US inventor, engineer and solar energy pioneer built a small demonstration solar engine that worked by reflecting solar energy onto square boxes filled with ether, which has a lower boiling point than water and were fitted internally with black pipes which in turn powered

7552-420: The amount of solar energy present near the surface of the planet because factors such as geography, time variation, cloud cover, and the land available to humans limit the amount of solar energy that we can acquire. In 2021, Carbon Tracker Initiative estimated the land area needed to generate all our energy from solar alone was 450,000 km — or about the same as the area of Sweden , or the area of Morocco , or

7670-596: The area of California (0.3% of the Earth's total land area). Solar technologies are categorized as either passive or active depending on the way they capture, convert and distribute sunlight and enable solar energy to be harnessed at different levels around the world, mostly depending on the distance from the Equator. Although solar energy refers primarily to the use of solar radiation for practical ends, all types of renewable energy, other than geothermal power and tidal power , are derived either directly or indirectly from

7788-696: The building, moving to a new location in 1985. The Solar Building was added to the New Mexico State Register of Cultural Properties in 1985 and the National Register of Historic Places in 1989. The building was considered "exceptionally significant", justifying its inclusion in the National Register even though it was only 33 years old at the time. The Solar Building is a one-story, International Style building consisting of two main sections. The north wing, containing

7906-545: The capture of solar energy to optimize the productivity of plants. Techniques such as timed planting cycles, tailored row orientation, staggered heights between rows and the mixing of plant varieties can improve crop yields. While sunlight is generally considered a plentiful resource, the exceptions highlight the importance of solar energy to agriculture. During the short growing seasons of the Little Ice Age , French and English farmers employed fruit walls to maximize

8024-421: The cold refrigerant mixture. At the same time, the circulating air is cooled and thus lowers the temperature of the enclosed space to the desired temperature. The evaporator is where the circulating refrigerant absorbs and removes heat which is subsequently rejected in the condenser and transferred elsewhere by the water or air used in the condenser. To complete the refrigeration cycle , the refrigerant vapor from

8142-551: The collection of solar energy. These walls acted as thermal masses and accelerated ripening by keeping plants warm. Early fruit walls were built perpendicular to the ground and facing south, but over time, sloping walls were developed to make better use of sunlight. In 1699, Nicolas Fatio de Duillier even suggested using a tracking mechanism which could pivot to follow the Sun. Applications of solar energy in agriculture aside from growing crops include pumping water, drying crops, brooding chicks and drying chicken manure. More recently

8260-754: The condenser and evaporator, must swap functions, they are optimized to perform adequately in both modes. Therefore, the Seasonal Energy Efficiency Rating (SEER in the US) or European seasonal energy efficiency ratio of a reversible heat pump is typically slightly less than those of two separately optimized machines. For equipment to receive the US Energy Star rating, it must have a rating of at least 14 SEER. Pumps with ratings of 18 SEER or above are considered highly efficient. The highest efficiency heat pumps manufactured are up to 24 SEER. Heating seasonal performance factor (in

8378-429: The condenser and the cooler refrigerant vapor emerging from the evaporator. The enthalpy difference required for the subcooling leads to the superheating of the vapor drawn into the compressor. When the increase in cooling achieved by subcooling is greater that the compressor drive input required to overcome the additional pressure losses, such a heat exchange improves the coefficient of performance. One disadvantage of

8496-434: The costs of mitigating global warming .... these advantages are global". The Earth receives 174  petawatts (PW) of incoming solar radiation ( insolation ) at the upper atmosphere . Approximately 30% is reflected back to space while the rest, 122 PW, is absorbed by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly spread across the visible and near-infrared ranges with

8614-479: The day and radiating stored heat to the cooler atmosphere at night. However, they can be used in cold temperate areas to maintain warmth as well. The size and placement of thermal mass depend on several factors such as climate, daylighting, and shading conditions. When duly incorporated, thermal mass maintains space temperatures in a comfortable range and reduces the need for auxiliary heating and cooling equipment. A solar chimney (or thermal chimney, in this context)

8732-425: The day and releasing it at night when the outside temperatures were lower. Most of the time, the water in the tank could be kept cool using only an evaporative cooler . If the water in the tank got too warm, the heat pump would go back into operation in order to continue transferring heat from the cold water stream into the tank. It was also possible to operate in cooling mode during the day while storing hot water from

8850-445: The evaporator is again a saturated vapor and is routed back into the compressor. Over time, the evaporator may collect ice or water from ambient humidity . The ice is melted through defrosting cycle. An internal heat exchanger is either used to heat/cool the interior air directly or to heat water that is then circulated through radiators or underfloor heating circuit to either heat or cool the buildings. Heat input can be improved if

8968-458: The fine glass surfaces of solar power plants. Metal grills would allow a high percentage of sunlight to enter the mirrors and solar panels while also preventing most damage. Sunlight has influenced building design since the beginning of architectural history. Advanced solar architecture and urban planning methods were first employed by the Greeks and Chinese , who oriented their buildings toward

9086-728: The first solar-powered crossing of the Pacific Ocean, and the Sun21 catamaran made the first solar-powered crossing of the Atlantic Ocean in the winter of 2006–2007. There were plans to circumnavigate the globe in 2010. In 1974, the unmanned AstroFlight Sunrise airplane made the first solar flight. On 29 April 1979, the Solar Riser made the first flight in a solar-powered, fully controlled, man-carrying flying machine, reaching an altitude of 40 ft (12 m). In 1980,

9204-403: The gas to condense to its liquid state. The liquified refrigerant flows to a heat exchanger in the outdoor space where the pressure falls, the liquid evaporates and the temperature of the gas falls. It is now colder than the temperature of the outdoor space being used as a heat source. It can again take up energy from the heat source, be compressed and repeat the cycle. Air source heat pumps are

9322-476: The globe. It is a single-seat plane powered by solar cells and capable of taking off under its own power. The design allows the aircraft to remain airborne for several days. A solar balloon is a black balloon that is filled with ordinary air. As sunlight shines on the balloon, the air inside is heated and expands, causing an upward buoyancy force, much like an artificially heated hot air balloon . Some solar balloons are large enough for human flight, but usage

9440-406: The ground is a constant temperature source, a ground-source heat pump is not subjected to large temperature fluctuations, and therefore is the most energy-efficient type of heat pump. The "seasonal coefficient of performance" (SCOP) is a measure of the aggregate energy efficiency measure over a period of one year which is dependent on regional climate. One framework for this calculation is given by

9558-456: The ground. The body of water does, however, need to be large enough to be able to withstand the cooling effect of the unit without freezing or creating an adverse effect for wildlife. The largest water-source heat pump was installed in the Danish town of Esbjerg in 2023. A thermoacoustic heat pump operates as a thermoacoustic heat engine without refrigerant but instead uses a standing wave in

9676-451: The heat flowing into it, the coefficient of performance decreases, causing an increasing amount of work to be required for each unit of heat being transferred. The coefficient of performance, and the work required by a heat pump can be calculated easily by considering an ideal heat pump operating on the reversed Carnot cycle : This is the theoretical amount of heat pumped but in practice it will be less for various reasons, for example if

9794-714: The heat from solar concentrators to drive the steam reformation of natural gas thereby increasing the overall hydrogen yield compared to conventional reforming methods. Thermochemical cycles characterized by the decomposition and regeneration of reactants present another avenue for hydrogen production. The Solzinc process under development at the Weizmann Institute of Science uses a 1 MW solar furnace to decompose zinc oxide (ZnO) at temperatures above 1,200 °C (2,200 °F). This initial reaction produces pure zinc, which can subsequently be reacted with water to produce hydrogen. Heat pump A heat pump

9912-618: The heat source and the heat sink is small. When using a heat pump for space or water heating, therefore, the heat pump will be most efficient in mild conditions, and decline in efficiency on very cold days. Performance metrics supplied to consumers attempt to take this variation into account. Common performance metrics are the SEER (in cooling mode) and seasonal coefficient of performance (SCOP) (commonly used just for heating), although SCOP can be used for both modes of operation. Larger values of either metric indicate better performance. When comparing

10030-581: The incoming air temperature up to 22 °C (40 °F) and deliver outlet temperatures of 45–60 °C (113–140 °F). The short payback period of transpired collectors (3 to 12 years) makes them a more cost-effective alternative than glazed collection systems. As of 2003, over 80 systems with a combined collector area of 35,000 square metres (380,000 sq ft) had been installed worldwide, including an 860 m (9,300 sq ft) collector in Costa Rica used for drying coffee beans and

10148-502: The integration of variable renewable energy . Therefore, they are regarded as a key technology for limiting climate change by phasing out fossil fuels . They are also a crucial element of systems which can both heat and cool districts . There is great potential to reduce the energy consumption and related greenhouse gas emissions in industry by application of industrial heat pumps, for example for process heat . Short payback periods of less than 2 years are possible, while achieving

10266-471: The main drafting room as well as the solar heating equipment, made up the main portion of the original building. It has an irregular quadrilateral cross-section with the roof and south wall both angled (at 20 and 30 degrees, respectively) in order to provide a high southern exposure for the solar collectors. The wing is framed by seven structural steel bents , spaced 18 feet (5.5 m) apart and filled in with wooden ceiling joists and masonry. The north wall has

10384-657: The modifications, the system remains mostly intact as originally designed. Solar energy Solar energy is the radiant energy from the Sun 's light and heat , which can be harnessed using a range of technologies such as solar electricity , solar thermal energy (including solar water heating ) and solar architecture . It is an essential source of renewable energy , and its technologies are broadly characterized as either passive solar or active solar depending on how they capture and distribute solar energy or convert it into solar power. Active solar techniques include

10502-454: The most common models, while other types include ground source heat pumps , water source heat pumps and exhaust air heat pumps . Large-scale heat pumps are also used in district heating systems. The efficiency of a heat pump is expressed as a coefficient of performance (COP), or seasonal coefficient of performance (SCOP). The higher the number, the more efficient a heat pump is. For example, an air-to-water heat pump that produces 6kW at

10620-512: The most developed are the parabolic trough, the solar tower collectors, the concentrating linear Fresnel reflector, and the Stirling dish. Various techniques are used to track the Sun and focus light. In all of these systems, a working fluid is heated by the concentrated sunlight, and is then used for power generation or energy storage. Designs need to account for the risk of a dust storm , hail , or another extreme weather event that can damage

10738-422: The most economical for decentralized domestic purposes, while active multiple effect units are more suitable for large-scale applications. Solar water disinfection (SODIS) involves exposing water-filled plastic polyethylene terephthalate (PET) bottles to sunlight for several hours. Exposure times vary depending on weather and climate from a minimum of six hours to two days during fully overcast conditions. It

10856-508: The need for alternative resources and are generally considered demand-side technologies. In 2000, the United Nations Development Programme , UN Department of Economic and Social Affairs, and World Energy Council published an estimate of the potential solar energy that could be used by humans each year. This took into account factors such as insolation, cloud cover, and the land that is usable by humans. It

10974-471: The northern Chilean region of Antofagasta employing molten salt technology. Solar power , also known as solar electricity, is the conversion of energy from sunlight into electricity , either directly using photovoltaics (PV) or indirectly using concentrated solar power . Solar panels use the photovoltaic effect to convert light into an electric current . Concentrated solar power systems use lenses or mirrors and solar tracking systems to focus

11092-785: The opposite direction. ASHPs are the most common type of heat pump and, usually being smaller, tend to be used to heat individual houses or flats rather than blocks, districts or industrial processes. Air-to-air heat pumps provide hot or cold air directly to rooms, but do not usually provide hot water. Air-to-water heat pumps use radiators or underfloor heating to heat a whole house and are often also used to provide domestic hot water . An ASHP can typically gain 4 kWh thermal energy from 1 kWh electric energy. They are optimized for flow temperatures between 30 and 40 °C (86 and 104 °F), suitable for buildings with heat emitters sized for low flow temperatures. With losses in efficiency, an ASHP can even provide full central heating with

11210-414: The other when used in cooling mode) and two heat exchangers, one associated with the external heat source/sink and the other with the interior. In heating mode the external heat exchanger is the evaporator and the internal one being the condenser; in cooling mode the roles are reversed. Circulating refrigerant enters the compressor in the thermodynamic state known as a saturated vapor and is compressed to

11328-440: The outside unit has been installed where there is not enough airflow. More data sharing with owners and academics—perhaps from heat meters —could improve efficiency in the long run. Milestones: An air source heat pump (ASHP) is a heat pump that can absorb heat from air outside a building and release it inside; it uses the same vapor-compression refrigeration process and much the same equipment as an air conditioner , but in

11446-408: The panels. Gilman made additional modifications to the system in the 1970s, including changing the working fluid in the collector loop to ethylene glycol (in order to prevent freezing) and re-soldering the collector panels for better thermal contact. Gilman also installed an automated control system and upgraded the air handling equipment to allow individual temperature control for each office. Despite

11564-444: The performance of heat pumps, the term performance is preferred to efficiency , with coefficient of performance (COP) being used to describe the ratio of useful heat movement per work input. An electrical resistance heater has a COP of 1.0, which is considerably lower than a well-designed heat pump which will typically have a COP of 3 to 5 with an external temperature of 10 °C and an internal temperature of 20 °C. Because

11682-571: The planned South African Solar Challenge are comparable competitions that reflect an international interest in the engineering and development of solar powered vehicles. Some vehicles use solar panels for auxiliary power, such as for air conditioning, to keep the interior cool, thus reducing fuel consumption. In 1975, the first practical solar boat was constructed in England. By 1995, passenger boats incorporating PV panels began appearing and are now used extensively. In 1996, Kenichi Horie made

11800-561: The pure water by-product going directly into the municipal water system. In addition, chemical energy storage is another solution to solar energy storage. Hydrogen production technologies have been a significant area of solar chemical research since the 1970s. Aside from electrolysis driven by photovoltaic or photochemical cells, several thermochemical processes have also been explored. One such route uses concentrators to split water into oxygen and hydrogen at high temperatures (2,300–2,600 °C or 4,200–4,700 °F). Another approach uses

11918-404: The solar collectors and heat pump to heat the building at night. Minor changes were made to the system during its operational life. One of the first problems that arose was corrosion of the collector panels, which originally had integral flow channels formed from two bonded sheets of aluminum. After leaks started to develop, the flow channels were replaced with copper tubing attached to the back of

12036-406: The solar thermal panel performs the function of the low temperature heat source and the heat produced is used to feed the heat pump's evaporator. The goal of this system is to get high COP and then produce energy in a more efficient and less expensive way. A water-source heat pump works in a similar manner to a ground-source heat pump, except that it takes heat from a body of water rather than

12154-414: The south to provide light and warmth. The common features of passive solar architecture are orientation relative to the Sun, compact proportion (a low surface area to volume ratio), selective shading (overhangs) and thermal mass . When these features are tailored to the local climate and environment, they can produce well-lit spaces that stay in a comfortable temperature range. Socrates ' Megaron House

12272-477: The southern side of a building in the northern hemisphere or the northern side in the southern hemisphere, their leaves provide shade during the summer, while the bare limbs allow light to pass during the winter. Since bare, leafless trees shade 1/3 to 1/2 of incident solar radiation, there is a balance between the benefits of summer shading and the corresponding loss of winter heating. In climates with significant heating loads, deciduous trees should not be planted on

12390-861: The surrounding environment. The higher temperatures result from increased absorption of solar energy by urban materials such as asphalt and concrete, which have lower albedos and higher heat capacities than those in the natural environment. A straightforward method of counteracting the UHI effect is to paint buildings and roads white and to plant trees in the area. Using these methods, a hypothetical "cool communities" program in Los Angeles has projected that urban temperatures could be reduced by approximately 3 °C at an estimated cost of US$ 1  billion, giving estimated total annual benefits of US$ 530  million from reduced air-conditioning costs and healthcare savings. Agriculture and horticulture seek to optimize

12508-409: The technology has been embraced by vintners , who use the energy generated by solar panels to power grape presses. Greenhouses convert solar light to heat, enabling year-round production and the growth (in enclosed environments) of specialty crops and other plants not naturally suited to the local climate. Primitive greenhouses were first used during Roman times to produce cucumbers year-round for

12626-402: The temperature of the liquid and-vapor refrigerant mixture to where it is colder than the temperature of the enclosed space to be refrigerated. The cold mixture is then routed through the coil or tubes in the evaporator. A fan circulates the warm air in the enclosed space across the coil or tubes carrying the cold refrigerant liquid and vapor mixture. That warm air evaporates the liquid part of

12744-414: The total installed capacity of solar hot water systems was approximately 436 thermal gigawatt (GW th ), and China is the world leader in their deployment with 309 GW th installed, taken up 71% of the market. Israel and Cyprus are the per capita leaders in the use of solar hot water systems with over 90% of homes using them. In the United States, Canada, and Australia, heating swimming pools

12862-699: The tropics and have more particularly proved that after our stores of oil and coal are exhausted the human race can receive unlimited power from the rays of the Sun. Solar hot water systems use sunlight to heat water. In middle geographical latitudes (between 40 degrees north and 40 degrees south), 60 to 70% of the domestic hot water use, with water temperatures up to 60 °C (140 °F), can be provided by solar heating systems. The most common types of solar water heaters are evacuated tube collectors (44%) and glazed flat plate collectors (34%) generally used for domestic hot water; and unglazed plastic collectors (21%) used mainly to heat swimming pools. As of 2015,

12980-460: The two wings. The building's active solar heating system employed an array of 56 solar thermal collectors with a total area of 800 square feet (74 m). The array was positioned on a south-facing exterior wall which was angled at 30 degrees to the vertical in order to catch the maximum amount of winter sunlight. The collectors were custom-fabricated aluminum panels with built-in flow channels for water to pass through. The surface of each collector

13098-765: The use of photovoltaic systems , concentrated solar power , and solar water heating to harness the energy. Passive solar techniques include designing a building for better daylighting , selecting materials with favorable thermal mass or light-dispersing properties, and organize spaces that naturally circulate air . In 2011, the International Energy Agency said that "the development of affordable, inexhaustible and clean solar energy technologies will have huge longer-term benefits. It will increase countries' energy security through reliance on an indigenous, inexhaustible, and mostly import-independent resource, enhance sustainability , reduce pollution , lower

13216-444: The warmer outdoors in warm weather (e.g. summer). As they transfer heat rather than generating heat, they are more energy-efficient than other ways of heating or cooling a home. A gaseous refrigerant is compressed so its pressure and temperature rise. When operating as a heater in cold weather, the warmed gas flows to a heat exchanger in the indoor space where some of its thermal energy is transferred to that indoor space, causing

13334-458: The water in the tank and delivering the "waste" heat to the hot water stream. The heat pump could continue to function as long as the tank temperature remained above 35 °F (2 °C). In summer, the system could also provide cooling by circulating cold water through the building rather than hot water. In this mode, the storage tank became a reservoir for cold water, which allowed the system to save energy in milder weather by storing heat during

13452-423: The water in the tank would be warm enough to directly heat the building by circulating it through radiant panels in the floor and ceiling. If the temperature in the tank dropped due to prolonged cloudy weather, a heat pump could be employed to maintain the hot water supply to the panels. The heat pump was a standard commercial water chiller unit, but with heating rather than cooling as its intended purpose—chilling

13570-456: The water unusable. Molten salt can be employed as a thermal energy storage method to retain thermal energy collected by a solar tower or solar trough of a concentrated solar power plant so that it can be used to generate electricity in bad weather or at night. It was demonstrated in the Solar Two project from 1995 to 1999. The system is predicted to have an annual efficiency of 99%,

13688-442: Was coated with low-reflectivity black paint and a layer of glass to capture the maximum amount of thermal energy. In sunny weather, water passing through the collectors would reach a maximum temperature of 140 °F (60 °C) before being deposited in a 6,000-gallon insulated underground tank which provided a hot water reserve for up to three days of cloudy weather. Under normal conditions (about 90% of an average heating season),

13806-440: Was not as economical as Bridgers and Paxton had hoped, mainly due to the extremely low cost of fuel at the time. When the building was expanded in 1962, the solar collector was abandoned in favor of a conventional boiler system, though the equipment was left intact for possible future use. This decision paid off just a few years later, when the 1973 oil crisis caused a renewed interest in solar energy and brought fresh attention to

13924-461: Was stated that solar energy has a global potential of 1,600 to 49,800 exajoules (4.4 × 10 to 1.4 × 10  kWh) per year (see table below) . Quantitative relation of global solar potential vs. the world's primary energy consumption : Source: United Nations Development Programme – World Energy Assessment (2000) Solar thermal technologies can be used for water heating, space heating, space cooling and process heat generation. In 1878, at

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