The equator

sunlight

Earth receives different amounts of solar energy at different latitudes, with the most at the equator and the least at the poles.

Neptune

The Earth absorbs most of the energy reaching its surface, a small fraction is reflected. In total approximately 70% of incoming radiation is absorbed by the atmosphere and the Earth’s surface while around 30% is reflected back to space and does not heat the surface.

Be aware that this nominal ratio is given for standard test conditions (STC) : radiation=1000 W/m2, cell temperature=25 celcius degree, Wind speed=1 m/s, AM=1.5. The unit of the nominal power of the photovoltaic panel in these conditions is called “Watt-peak” (Wp or kWp=1000 Wp or MWp=1000000 Wp).

Solar constant, the total radiation energy received from the Sun per unit of time per unit of area on a theoretical surface perpendicular to the Sun’s rays and at Earth’s mean distance from the Sun. The value of the constant is approximately 1.366 kilowatts per square metre.

The solar constant actually varies by +/-3% because of the Earth’s slightly elliptical orbit around the Sun. The Sun-Earth distance is smaller when the Earth is at perihelion (first week in January) and larger when the Earth is at aphelion (first week in July).

The specific value at Earth of 1,361 W/m2 is called the “solar constant”. In order to calculate the total amount of energy arriving at Earth, we need to know how much area is being lit. KS = solar insolation (“solar constant”) = 1,361 watts per square meter. RE = radius of Earth = 6,371 km = 6,371,000 meters.

The solar constant is used to quantify the rate at which energy is received upon a unit surface such as a solar panel. In this context, the solar constant provides a total measurement of the sun’s radiant energy as it is absorbed at a given point. Solar constants are used in various atmospheric and geological sciences.

Above the earth’s atmosphere, solar radiation has an intensity of approximately 1380 watts per square meter (W/m2). This value is known as the Solar Constant.

ANS :The intensity of solar radiation incident on unit cross-sectional area of earth exposed perpendicularly to the rays of sun at an average distance is called solar constant. Its value is 1.353 kW/m2.

Average annual solar radiation arriving at the top of the Earth’s atmosphere is roughly 1361 W/m2. The Sun’s rays are attenuated as they pass through the atmosphere, leaving maximum normal surface irradiance at approximately 1000 W/m2 at sea level on a clear day.

Therefore, the solar radiation is concentrated over a smaller surface area, causing warmer temperatures. At higher latitudes, the angle of solar radiation is smaller, causing energy to be spread over a larger area of the surface and cooler temperatures.

forty panels

noon

July

Earth’s Energy Balance 3. Most of the atmosphere is relatively transparent to solar radiation, with the most notable exception being clouds. At the surface, snow and ice have a high albedo and consequently absorb little incoming radiation.

So not only are there the obvious intensity changes in ground solar radiation level during the day, going to zero at night, but the spectrum of the radiation changes through each day because of the changing absorption and scattering path length.

Gamma rays

Solar Radiation at the Earth’s Surface

• atmospheric effects, including absorption and scattering;
• local variations in the atmosphere, such as water vapour, clouds, and pollution;
• latitude of the location; and.
• the season of the year and the time of day.