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A solar collector is a device for extracting the energy of the sun directly into a more usable or storable form. The energy in sunlight is in the form of electromagnetic radiation from the infrared (long wavelength) to the ultraviolet (short) wavelengths. The solar energy striking the earth's surface at any one time depends on weather conditions as well as location and orientation of the surface, but overall, it averages about 1000 watts per square meter on a clear day with the surface facing the sun. Image File history File links Download high resolution version (1026x768, 1495 KB) Summary Photographed by Alan Mak on September 3rd, 2005. ...
Image File history File links Download high resolution version (1026x768, 1495 KB) Summary Photographed by Alan Mak on September 3rd, 2005. ...
A laundromat (U.S.), launderette (British), Washette (Southeastern U.S.) or washateria (Southwestern U.S.) is a store where clothes are washed and dried. ...
State nickname: The Golden State Other U.S. States Capital Sacramento Largest city Los Angeles Governor Arnold Schwarzenegger (R) Senators Dianne Feinstein (D) Barbara Boxer (D) Official language(s) English Area 410,000 km² (3rd) - Land 404,298 km² - Water 20,047 km² (4. ...
The Sun is the star at the centre of our Solar system. ...
Electromagnetic radiation can be conceptualized as a self propagating transverse oscillating wave of electric and magnetic fields. ...
Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ...
Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ...
 Solar collectors installed on rooftops in Xian, China. A typical solar thermal collector does not store energy but uses fluid circulation (usually water or an antifreeze solution) to transfer the heat for direct use or storage in an insulated reservoir. Water/glycol has a high thermal capacity and is convenient to handle. The direct radiation is captured using a dark colored surface which absorbs the radiation and conducts it to the transfer fluid. Metal makes a good conductor, and copper or aluminium is best. By coating the surface with a high absorption / low emission coating, the conversion of solar radiation to heat can be optimised. Special "selective surface" materials can be chosen to reduce heat-loss due to emission in conjunction with using a glass plate cover to reduce losses due to infra-red (long wavelength) emissions. Image File history File links Download high resolution version (1024x768, 135 KB)Image of rooftops mounted solar collectors in Xian, China. ...
Image File history File links Download high resolution version (1024x768, 135 KB)Image of rooftops mounted solar collectors in Xian, China. ...
A Solar thermal collector absorbs sunlight to provide heat. ...
Heat capacity (abbreviated Cth or just C, also called thermal capacity) is the ability of matter to store heat. ...
Radiation has a variety of different meanings. ...
Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) in a cloud of electrons. ...
General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ...
General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ...
In solar thermal collectors, a selective surface is chosen based on the ratio of radiation-absorption (alpha) to radiation-emission (epsilon), with a higher ratio meaning better performance. ...
The word emission generally means sending something out. ...
As it heats up, thermal losses from the collector itself will reduce its efficiency. Most of this emitted radiation is of longer wavelength (infra-red). This is countered in two ways. First, a glass plate is placed above the collector plate which will trap the radiated heat within the airspace below it. This exploits the so-called greenhouse effect, which is in this case a property of the glass - it readily transmits solar radiation in the visible and ultraviolet spectrum, but does not transmit the lower frequency infra-red re-radiation very well. The glass plate also traps air in the space, thus reducing heat losses by convection. The collector housing is also insulated below and laterally to reduce its heat loss. The second way efficiency is improved is by cooling the absorber plate - this is done by ensuring that coldest available heat transfer fluid is circulated through the absorber, and with a sufficient flow rate - the fluid carries away the absorbed heat so cooling the absorber. The warmed fluid leaving the collector is either directly stored, or else passes through a heat exchanger to warm another tank of water, or used to heat a building directly. The temperature differential across an efficient solar collector is usually only 10 or 20°C - a large differential may seem impressive, but is in fact an indication of a less efficient design. In physics, mechanical efficiency is the effectiveness of a simple machine. ...
The greenhouse effect, first discovered by Joseph Fourier in 1824, is the process by which an atmosphere warms a planet. ...
A heat exchanger is a device for transferring heat from one fluid to another, where the fluids are separated by a solid wall so that they never mix. ...
The solar heating system consists of the collector described above; a heat transfer circuit that includes the fluid and the means to circulate it; and a storage system including a heat exchanger (if the fluid cirulating through the collector is not the same liquid being used to heat the object of the system. The system may or may not include secondary distribution of heat among different storage reservoirs or users of the heat. The system can be used to warm domestic hot water, to heat a swimming pool, to heat water for a radiator or floor-coil heating circuit, to heat an industrial dryer, to provide input energy for a cooling system, et cetera. The heat is normally stored in insulated storage tanks full of water. Heat storage is usually intended to cover a day or two's requirements, but other concepts exist including seasonal storage (where summer solar energy is used for winter heating by just raising the temperature by a few degrees of several million liters of water (numerous pilot housing projects in Germany and elsewhere use this concept).
For solar heating of domestic hot water, two common system types are thermosyphon and pumped. In the thermosyphon system, a storage tank is placed above the collector. As the water in the collector is heated, it will rise and naturally start to circulate to the tank. This draws in colder water from the bottom of the tank. This system is self regulating and requires no moving parts or external energy, so is very attractive. Its main drawback is the need for the tank to be placed at a level higher than the collector, which may prove to be physically difficult. A pumped system uses a pump to circulate the water, so the tank can be positioned independently of the collector location. This system requires external energy to run the pump (though this can be solar, since the water should only be circulated when there is incident sunlight). It also requires control electronics to measure the temperature gradient across the collector and modulate the pump accordingly. Manual pump used to obtain water A pump is a mechanical device used to move liquids or gases. ...
Two digital voltmeters The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. ...
For the musical use of modulation, see modulation (music). ...
Solar collectors can be mounted on a roof but need to face the sun, so a north facing roof in the southern hemisphere, and a south-facing roof in the northern hemisphere are ideal. Collectors are usually also angled to suit the latitude of the location. Where sunshine is readily available, a 2 to 10 square metre array will provide all the hot water heating required for a typical family house. Such systems are a key feature of sustainable housing, since water and space heating is usually the largest single consumer of energy in households. Latitude, sometimes denoted by the Greek letter φ, gives the location of a place on Earth north or south of the Equator. ...
An autonomous building is a building designed to have very little to no networked services. ...
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