Annual mean insolation, at the top of Earth's atmosphere (top) and at the planet's surface.

US annual average solar energy received by a latitude tilt photovoltaic cell.

Insolation (INcident SOLar radiATION) is a measure of solar radiation energy received on a given surface area in a given time. It is commonly expressed as average irradiance in watts per square meter (W/m²) or kilowatt-hours per square meter per day (kW·h/(m²·day)), or in the case of photovoltaics it is commonly measured as kWh/kWp•y (kilowatt hours per year per kilowatt peak rating). The surface may be a planet or a terrestrial object inside the atmosphere, or any object exposed to solar rays including spacecraft. Some of the solar radiation will be absorbed, causing radiant heating of the object, and the remainder will be reflected. The proportion of radiation reflected or absorbed depends on the object's reflectivity or albedo. Sometimes, as in the text below, a long-term average intensity of incoming solar radiation will be given in units such as watts per square meter (W/m² or W·m^-2) and called insolation, with the duration (such as daily, annual, or historical) stated or only implied. Look up insulation in Wiktionary, the free dictionary. ... Image File history File links Download high resolution version (691x737, 17 KB) Summary Insolation (w/m2), annual mean. ... Image File history File links Download high resolution version (691x737, 17 KB) Summary Insolation (w/m2), annual mean. ... Air redirects here. ... Image File history File links Download high resolution version (1501x1164, 263 KB) Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (1501x1164, 263 KB) Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Solar irradiance spectrum at top of atmosphere. ... Irradiance, radiant emittance, and radiant exitance are radiometry terms for the power of electromagnetic radiation at a surface, per unit area. ... Photovoltaic tree in Styria, Austria Photovoltaics, or PV for short, is a solar power technology that uses solar cells or solar photovoltaic arrays to convert light from the sun directly into electricity. ... The Space Shuttle Discovery as seen from the International Space Station. ... In optics, reflectivity is the reflectance (the ratio of reflected power to incident power, generally expressed in decibels or percentage) at the surface of a material so thick that the reflectance does not change with increasing thickness; , the intrinsic reflectance of the surface, irrespective of other parameters such as the... For other uses, see Albedo (disambiguation). ...

Projection effect

The insolation into a surface is largest when the surface directly faces the Sun. As the angle increases between the direction normal to the surface and the direction of the rays of sunlight, the insolation is reduced in proportion to the cosine of the angle. This is known in optics as Lambert's cosine law. This 'projection effect' is the main reason why the polar regions are much colder than equatorial regions on Earth. On an annual average the poles receive less insolation than does the equator, because at the poles the Earth's surface is angled away from the Sun. In mathematics, the trigonometric functions are functions of an angle, important when studying triangles and modeling periodic phenomena. ... Lamberts cosine law says that the total radiant power observed from a Lambertian surface is directly proportional to the cosine of the angle θ between the observers line of sight and the surface normal. ... Location of the polar regions Northern Hemisphere permafrost (permanently frozen ground) in purple. ... The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the northern hemisphere and the Tropic of Capricorn in the southern hemisphere. ...

Earth's insolation

Direct insolation is the solar radiation that is transmitted directly through the atmosphere to the earth's surface without interacting with atmospheric components. Diffuse insolation is the solar radiation that is scattered or reflected by atmospheric components. Direct insolation is the solar radiation that is transmitted directly through the atmosphere to the earths surface without interacting with atmospheric components. ... Diffuse insolation is the solar radiation that is scattered or reflected by atmospheric components (clouds, for example) to the earths surface. ...

Over the course of a year the average solar radiation arriving at the top of the Earth's atmosphere is roughly 1366 ^[1] watts per square meter (see solar constant). The radiant power is distributed across the entire electromagnetic spectrum, although most of the power is in the visible light portion of the spectrum. The Sun's rays are attenuated as they pass though the atmosphere, thus reducing the insolation at the Earth's surface to approximately 1000 watts per square meter for a surface perpendicular to the Sun's rays at sea level on a clear day. For other uses, see Watt (disambiguation). ... A square metre (US spelling: square meter) is by definition the area enclosed by a square with sides each 1 metre long. ... Solar irradiance spectrum at top of atmosphere. ... Although some radiations are marked as N for no in the diagram, some waves do in fact penetrate the atmosphere, although extremely minimally compared to the other radiations The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... This article is about Physics. ... Atmospheres redirects here. ...

The actual figure varies with the Sun angle at different times of year, according to the distance the sunlight travels through the air, and depending on the extent of atmospheric haze and cloud cover. Ignoring clouds, the average insolation for the Earth is approximately 250 watts per square meter (6 (kW·h/m²)/day), taking into account the lower radiation intensity in early morning and evening, and its near-absence at night. Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ... Look up air in Wiktionary, the free dictionary. ...

The insolation of the sun can also be expressed in Suns, where one Sun equals 1000 W/m² at the point of arrival. One Sun is a unit of power flux, not a standard value for actual insolation. Sometimes this unit is referred to as a Sol, not to be confused with a sol, meaning one solar day on, for example, a different planet, such as Mars.^{[citation needed]} flux in science and mathematics. ...

Applications

In spacecraft design and planetology, it is the primary variable affecting equilibrium temperature and global climate. The Space Shuttle Discovery as seen from the International Space Station. ... Planetary science, also known as planetology or planetary astronomy, is the science of planets and the solar system, and incorporates an interdisciplinary approach drawing from diverse sciences. ... In thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, and chemical equilibrium. ... For other uses, see Temperature (disambiguation). ... Global climate is a concept that has never been defined, but roughly speaking it is meant to express the average temperature, average precipitation, average intensity of winds and similar features of Earths atmosphere and the whole planets surface. ...

In construction, insolation is an important consideration when designing a building for a particular climate. It is one of the most important climate variables for human comfort and building energy efficiency.^[2]

The projection effect can be used in architecture to design buildings that are cool in summer and warm in winter, by providing large vertical windows on the equator-facing side of the building (the south face, in the northern hemisphere): this maximizes insolation in the winter months when the Sun is low in the sky, and minimizes it in the summer when the noonday Sun is high in the sky. (The Sun's north/south path through the sky spans 47 degrees through the year). This article is about building architecture. ... Northern hemisphere highlighted in yellow. ... Theoretical rendering of the analemma, looking east in the northern hemisphere. ...

Insolation figures are used as an input to worksheets to size solar power systems for the location where they will be installed.^[3] The figures can be obtained from an insolation map or by city or region from insolation tables that were generated with historical data over the last 30-50 years. Photovoltaic panels are rated under standard conditions to determine the Wp rating (watts peak),^[4] which can then be used with the insolation of a region to determine the expected output, along with other factors such as tilt, tracking and shading (which can be included to create the installed Wp rating).^[5] Insolation values range from 800 to 950 in Norway to 2200-2400 kWh/kWp•y in Thailand and Israel. Solar power describes a number of methods of harnessing energy from the light of the sun. ...

In the fields of civil engineering and hydrology, numerical models of snowmelt runoff use observations of insolation. This permits estimation of the rate at which water is released from a melting snowpack. Field measurement is accomplished using a pyranometer. The Falkirk Wheel in Scotland. ... Water covers 70% of the Earths surface. ... A pyranometer is a type of actinometer used to measure broadband solar irradiance on a planar surface. ...

See also

• Albedo
• Flux
• Power density
• Sun chart

For other uses, see Albedo (disambiguation). ... flux in science and mathematics. ... In engineering, specific power (sometimes also power per unit mass or power density) refers to the amount of power delivered by an energy source, divided by some measure of the sources size or mass. ... A sun chart is a graph of solar azimuth and solar altitude for a particular latitude, by time of day and for one or more days of the year. ...

References

For other uses, see 5th October (Serbia). ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ...

External links

Look up insolation in Wiktionary, the free dictionary.

• Global Insolation Map
• National Science Digital Library - Insolation
• San Francisco Solar Map
• Yesterday‘s Australian Solar Radiation Map