iPedia Free Information Center

Information about Insolation

Not to be confused with insulation.


Enlarge picture
Annual mean insolation, at the top of Earth's atmosphere (top) and at the planet's surface.
Enlarge picture
US annual average solar energy received by a latitude tilt photovoltaic cell.
Insolation (from INcoming SOLar radiATION) is a measure of solar energy received on a given surface area in a given time. It is commonly expressed in kilowatt-hours per square meter per day (kW•h/m²/day). 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 Wm-2) and called insolation, with the duration (such as daily, annual, or historical) stated or only implied.

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.

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.

Over the course of a year the average solar radiation arriving at the top of the Earth's atmosphere is 1366 watts per square meter[1] (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.

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.

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.

Applications

In spacecraft design and planetology, it is the primary variable affecting equilibrium temperature and global climate.

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).

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.

In the fields of civil engineering and hydrology, numerical models of snowmelt runoff use observations of insolation. This permits estimation of the rate at water is released from a melting snowpack. Field measurement is accomplished using a pyranometer.

See also

References

External links

Insulation may mean:
  • Building insulation, added to buildings for comfort and energy efficiency
  • Electrical insulation, materials used to inhibit the conduction of electricity

..... Click the link for more information.
spacecraft is a vehicle or device designed for spaceflight. On a sub-orbital spaceflight, a spacecraft enters outer space but then returns to the planetary surface (such as Earth) without making a complete orbit.
..... Click the link for more information.
In optics and heat transfer, reflectivity is the fraction of incident radiation reflected by a surface. In full generality it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength.
..... Click the link for more information.
The albedo of an object is the extent to which it reflects light, defined as the ratio of reflected to incident electromagnetic radiation. It is a unitless measure indicative of a surface's or body's diffuse reflectivity.
..... Click the link for more information.
trigonometric functions (also called circular functions) are functions of an angle. They are important in the study of triangles and modeling periodic phenomena, among many other applications.
..... Click the link for more information.
Lambert's cosine law in optics says that the radiant intensity observed from a "Lambertian" surface is directly proportional to the cosine of the angle θ between the observer's line of sight and the surface normal.
..... Click the link for more information.
polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica.
..... Click the link for more information.
tropics are the geographic region of the Earth centered on the equator and limited in latitude by the Tropic of Cancer in the northern hemisphere, at approximately 23°30' (23.5°) N latitude, and the Tropic of Capricorn in the southern hemisphere at 23°30' (23.5°) S latitude.
..... Click the link for more information.
Direct insolation is the solar radiation that is transmitted directly through the atmosphere to the earth's surface without interacting with atmospheric components.

External links

  • National Science Digital Library - Direct Insolation

..... Click the link for more information.
Diffuse insolation is the solar radiation that is scattered or reflected by atmospheric components (clouds, for example) to the earth's surface.

External links

  • National Science Digital Library - Diffuse Insolation

..... Click the link for more information.
WATT

City of license Cadillac, Michigan
Broadcast area [1]
Branding NewsTalk 1240
First air date 1945
Frequency 1240 kHz
Format News-Talk-Sports
Power 1,000 watts
Class C
Owner MacDonald Garber Broadcasting
..... Click the link for more information.
square metre (also spelled meter, see spelling differences) is the SI derived unit of area, with symbol m². It is defined as the area of a square whose sides measure exactly one metre.
..... Click the link for more information.
electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. The "electromagnetic spectrum" (usually just spectrum) of an object is the frequency range of electromagnetic radiation with wavelengths from thousands of kilometers down to fractions of
..... Click the link for more information.
visible spectrum (or sometimes optical spectrum) is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light.
..... Click the link for more information.
Attenuation is the reduction in amplitude and intensity of a signal. Signals may be attenuated exponentially by transmission through a medium, in which case attenuation is usually reported in dB with respect to distance traveled through the medium.
..... Click the link for more information.
atmosphere is a layer of gases that may surround a material body of sufficient mass.[1] The gases are attracted by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low.
..... Click the link for more information.
Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon.
..... Click the link for more information.
Air or Earth's atmosphere is a layer of gases surrounding the planet Earth.

Air may also refer to:
  • Air (1977 video game), an air combat based mainframe computer game
  • Air (band), a French electronic music duo

..... Click the link for more information.
flux, both with rigorous mathematical frameworks.
  • In the study of transport phenomena (heat transfer, mass transfer and fluid dynamics), flux is defined as the amount that flows through a unit area per unit time, the volumetric flow rate.

..... Click the link for more information.
spacecraft is a vehicle or device designed for spaceflight. On a sub-orbital spaceflight, a spacecraft enters outer space but then returns to the planetary surface (such as Earth) without making a complete orbit.
..... Click the link for more information.
Planetary science, also known as planetology and closely related to planetary astronomy, is the science of planets, or planetary systems, and the solar system.
..... Click the link for more information.
thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, and chemical equilibrium. The local state of a system at thermodynamic equilibrium is determined by the values of its intensive parameters, as pressure, temperature, etc.
..... Click the link for more information.
trillion fold).]]

Temperature is a physical property of a system that underlies the common notions of hot and cold; something that is hotter generally has the greater temperature. Temperature is one of the principal parameters of thermodynamics.
..... Click the link for more information.
Climate is the average and variations of weather over long periods of time. Climate zones can be defined using parameters such as temperature and rainfall.
..... Click the link for more information.
Architecture is the art and science of designing buildings and structures. A wider definition often includes the design of the total built environment: from the macrolevel of town planning, urban design, and landscape architecture to the microlevel of construction details and,
..... Click the link for more information.
Northern Hemisphere or northern hemisphere[1] is the half of a planet that is north of the equator—the word hemisphere literally means 'half ball'. It is also that half of the celestial sphere north of the celestial equator.
..... Click the link for more information.
analemma (pronounced IPA: /ˌænəˈlɛmə/, Latin for the pedestal of a sundial) is a curve representing the angular offset of a celestial body (usually the Sun) from its mean position
..... Click the link for more information.
Solar energy is energy from the sun. It supports life on Earth and drives the Earth's weather. Solar energy predominantly arrives in the form of infrared, visible and ultraviolet light, and is either returned back to space or is absorbed.
..... Click the link for more information.
Civil engineering is a professional engineering discipline that deals with the design and construction of the physical and natural built environment, including works such as bridges, roads, canals, dams and buildings.
..... Click the link for more information.
Hydrology (from Greek: Yδωρ, hudōr, "water"; and λόγος, logos, "knowledge") is the study of the movement, distribution, and quality of water throughout the Earth, and thus addresses both the hydrologic cycle and water resources.
..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
Herod_Archelaus


page counter