Energy+expert+group

The term "radiant energy" is most commonly used in the fields of [|radiometry], [|solar energy], [|heating] and [|lighting], but is also sometimes used in other fields (such as [|telecommunications]). In modern applications involving transmission of power from one location to another, "radiant energy" is sometimes used to refer to the electromagnetic waves //themselves//, rather than their //energy// (a property of the waves). In the past, the term "electro-radiant energy" has also been used.[|[4]] Historically, the propagation of electromagnetic radiation was presumed to rely on a medium filling all space, known as the[|aether].[|[5]][|[6]][|[7]] Electromagnetic waves were presumed to propagate through this medium by inducing transverse electric and magnetic stresses and strains, analogous to those induced by [|shear waves] propagating through a physical medium.[|[8]] In modern times, the propagation of electromagnetic waves has been shown not to require any physical medium, although some interpretations of [|general relativity] can be viewed as implying that space acts as a kind of non-physical "medium" for light Radiant energy is one of the energy sources that can be used to power an open system. Such an open system can be man-made (such as a solar energy collector), or natural, such as the Earth's atmosphere. In geophysics, transparent greenhouse gases trap the sun's radiant energy (at certain wavelengths), allowing it to penetrate deep into the atmosphere or all the way to the Earth's surface, where they are re-emitted as longer wavelength radiation (chiefly infrared radiation). Radiant energy is produced in the sun as a result of nuclear fusion. Radiant energy, as well as convective and conductive energy, is used for heating homes. It can be generated electrically by infrared lamps, or can be absorbed from sunlight and used to heat water. Since radiant energy is really just electromagnetic radiation under another name, it is the basis of a wide range of communication technologies using radiofrequency and microwave radiation. One of the earliest wireless telephones to be based on radiant energy was invented by Nikola Tesla. The device used transmitters and receivers whose resonances were tuned to the same frequency, allowing communication between them. In 1916, he recounted (see Anderson's book, below) an experiment he had done in 1896. He recalled that "Whenever I received the effects of a transmitter, one of the simplest ways [to detect the wireless transmissions] was to apply a magnetic field to currents generated in a conductor, and when I did so, the low frequency gave audible notes." The United States Patent Offices has a classification of radiant energy for patent applications (Class 250, a residual class for methods and apparatus involving radiant energy). This class provides for all methods and apparatus for using, generating, controlling or detecting radiant energy, combinations including such methods or apparatus, subcombinations of same and accessories therefore not classifiable elsewhere by the patent office. In the case of outdoor areas, the surrounding air is constantly moving, making conventional [|patio heaters] (also known as "mushroom heaters"), which rely partly on convection heating, impractical. The reason being, that once you heat the outside air, it will blow away with air movement. Outdoor radiant heaters allow specific spaces within an outdoor area to be targeted, warming only the people and objects in their path. The [|Romans] were the first people to use underfloor radiant heating systems. These systems were based on [|hypocausts], and used warm air for heat. The floor was set on top of many brick piles, leaving room for the hot air and steam produced by a [|furnace]to pass underneath the floor. The hot air then went up chimneys on the sides of the walls, so the hot air and steam never actually went into the living rooms. These systems were very expensive to build and maintain, so only the wealthy could afford them. In [|Korea], radiant underfloor heating has been in use for about 2000 years. [|Ondol], which means "warm stone," involves the use of stones and underground [|ducts] to help transport warm air from the kitchen to the rooms in the house. Most homes and buildings in Korea still use ondol, although they now use hot water and electric systems. The [|American] architect [|Frank Lloyd Wright]discovered ondol in the early 1900s and used it in many of his building designs. Wright also invented hot water underfloor systems.[|[1]] =**Radiant Barriers**= Radiant barriers are installed in homes—most commonly in attics—to reduce summer heat gain and winter heat loss, which helps lower heating and cooling costs. The barriers consist of a highly reflective material that reflects radiant heat rather than absorbing it. They don't, however, reduce heat conduction like thermal insulation materials.
 * Radiant energy** is the [|energy] of electromagnetic waves. Radiant [|energy] exists in a range of wavelengths that extends from Extremely Low Frequency (ELF) to gamma rays. The term is most commonly used in the fields of radiometry, solar energy, heating and lighting, but is also used less frequently in other fields (such as telecommunications). The quantity of radiant energy may be calculated by integrating radiant flux (or power) with respect to time and, like all forms of energy, its SI unit is the joule. In applications involving transmission of power from one location to another, "radiant energy" is sometimes used to refer to the electromagnetic waves themselves, rather than their energy (a property of the waves).
 * Radiant heating** is a technology for heating indoor and outdoor areas. Radiant heating consists of "radiant energy" being emitted from a heat source. Radiant heating heats a building through [|radiant heat], rather than other conventional methods including [|convection heating]. The technology has existed since the Roman use of [|Hypocaust] heating. Underfloor radiant heating has long been widespread in China and Korea. The heat energy is emitted from a warm element (floor, wall, overhead panel) and warms people and other objects in rooms rather than directly heating the air. The internal air temperature for radiant heated buildings may be lower than for a conventionally heated building to achieve the same level of body comfort (when adjusted so the perceived temperature is actually the same).

**How They Work**
Heat travels from a warm area to a cool area by a combination of conduction, convection, and radiation. Heat flows by //conduction//from a hotter location within a material or assembly to a colder location. Heat transfer by //convection// occurs when a liquid or gas is heated by a surface, becomes less dense, and rises (natural convection), or when a moving stream of air absorbs heat from a warmer surface (forced convection). //Radiant// heat travels in a straight line away from any surface and heats anything solid that absorbs the incident energy. Radiant heat transfer occurs because warmer surfaces emit more radiation than cooler surfaces. When the sun heats a roof, it's primarily the sun's radiant energy that makes the roof hot. A large portion of this heat travels by conduction through the roofing materials to the attic side of the roof. The hot roof material then radiates its gained heat energy onto the cooler attic surfaces, including the air ducts and the attic floor. A radiant barrier reduces the radiant heat transfer from the underside of the roof to the other surfaces in the attic.