Most of the Energy From the Sun Travels to Earth in the Form of
Most of the Energy From the Sun Travels to Earth in the Form of
Effigy one. The Dominicus is the major source of energy and vital to life on Globe, but much of its light is reflected. Solar free energy acts as a primary energy menstruum that can exist harnessed.[one]
Most all of the Earth'due south free energy input comes from the sun. Not all of the sunlight that strikes the elevation of the atmosphere is converted into energy at the surface of the Earth. The Solar free energy to the Earth refers to this energy that hits the surface of the Earth itself. The amount of energy that reaches the the Earth provides a useful understanding of the energy for the Earth equally a system. This energy goes towards weather, keeping the temperature of the Globe at a suitable level for life, and powers the entire biosphere. Additionally, this solar energy tin be used for solar power either with solar thermal power plants or photovoltaic cells.
Calculating Solar Energy to Surface
Energy from Lord's day to Earth
The Sunday is generally considered to produce a constant amount of ability (although there are small variances in the output energy depending on sunspot cycles) with a surface intensity of [math]vi.33 \times 10^7 \frac{W}{m^two} [/math], expressed in units of power per unit expanse. Equally the Dominicus's rays spread into space this radiations becomes less and less intense equally an inverse square law.[two] The average radiation intensity that hits the edge of the Earth'due south temper is known as the solar constant, or [math]I_{sc}[/math]. Although this value is called a constant it varies past about 7% between January 4th (perihelion), when the Earth is closest to the lord's day, and July 4th (aphelion), when the Earth is furthest away.[iii] Therefore a yearly average is used and is adamant to exist [math]1367 \frac{West}{thou^2}[/math].[ii] To determine this value from solar flux, the altitude from the Earth to the Sun is used. Every bit well, the full solar flux - not solar flux per unit expanse - must be determined. So the total solar flux from the Sun is divided by the surface expanse of a sphere that has a radius equal to the distance from the Earth to the Sun. This accounts for the "spreading" of the solar free energy. The expression to determine this value is:
To determine the boilerplate corporeality of solar energy that reaches the Earth, we must consider what the Globe "looks similar" to the Dominicus. When looking at Earth from the Dominicus, only 1 half of the Globe can be seen. Thus to make an advisable estimate of the average corporeality of solar energy over the entire area of the Earth the value for [math]I_{sc}[/math] must exist divided past 2.
Figure two. How the intensity of sunlight on Earth varies with lattitude.[4]
In addition to this, the total solar irradiance is the maximum ability delivered to a surface assuming that the path of incoming light is perpendicular to that surface. Due to the fact that the Earth is a sphere, simply places near the equator come up shut to this perpendicular angle. At all other locations on the Globe, incoming sunlight is at some angle. With this decreasing bending, the average solar irradiance decreases as well. To account for this, the solar irradiance level is again halved, leaving a final boilerplate solar irradiance of approximately [math]I_{sc}^{'} = 340 \frac{W}{chiliad^2}[/math].[5]
This value, which represents the average solar irradiance hitting Globe'southward outer atmosphere, does not nevertheless account for losses due to reflection and absorption, which is discussed in the following section.
Energy Captivated past the Globe
Not all of the solar energy that reaches the Earth's atmosphere is absorbed by the Earth. This is due to something known equally the Earth's energy budget.[half-dozen] This budget accounts for the fact that some of the free energy incident on the outer atmosphere of the planet is immediately reflected dorsum into infinite.
Figure 3. Percent of incoming radiation from the Sunday that is reflected and absorbed by the surface of the Earth, the atmosphere, and clouds.[7]
Due to reflection by the atmosphere, clouds, and World'southward surface we tin approximate that 70% of solar free energy incident on the edge of the Globe'south atmosphere is actually absorbed by the Earth. Taking this into account, the actual boilerplate amount of solar energy absorbed past the Globe amounts to:
Energy to the Surface
Free energy that is absorbed by the World is not the same as the energy incident on the Earth'southward surface. On a perfectly clear or clement day, when the Sunday is directly overhead (or at the "zenith"), solar irradiation is yet reduced due to assimilation (16%) and reflection (6%) by particles in Globe's atmosphere. These particles include carbon dioxide (CO2), Oxygen (O2), Ozone (O3) and water vapor (H2O).[viii]
Figure iv. Solar radiation spectrum for directly light at both the top of the Earth'due south atmosphere and at body of water level.[9]
This 22% reduction of solar irradiation will be college on boilerplate because the Sunday is non always at the zenith. To standardize this measurement, a unit chosen Air Mass is used to define the solar spectrum that is incident at various altitudes and weather condition on World. Air Mass 0, or AM0 spectrum is the solar radiation outside the temper and represents a power density of [math]1367\frac{West}{m^ii}[/math]. AM1.v is regarded as "normal" air mass and represents a ability density of [math]m\frac{West}{chiliad^two}[/math].[eight]
The quantity of [math]1000 \frac{W}{m^2}[/math] is divers as a unit of radiation, called "1 sun", and is commonly used as a standard to examination and rate photovoltaic cells and solar panels. This means that a solar panel rated at 250 watts volition output this rated power when exposed to a solar ability density of [math]1000 \frac{West}{chiliad^two}[/math]. Although this corporeality of energy is quite meaning, it does not mean that solar free energy can easily provide all of our primary free energy. Bug with solar free energy include cloudy days and the lack of a reasonable way to shop "excess" energy nerveless on sunny days. Equally well, this assumes that solar panels are 100% efficient at converting solar energy into electricity or another usable form of energy, which is non the case. Although solar ability is 1 important type of renewable energy source, it is of import to investigate the benefits and drawbacks of this type of energy.[ten]
References
- ↑ Pixabay. (August 19, 2015). Sunlight [Online]. Available: http://pixabay.com/en/sunlight-heaven-daylight-summer-422710/
- ↑ ii.0 2.i ITACA. (April four, 2015). The Sun every bit a Source of Energy [Online]. Bachelor: http://www.itacanet.org/the-sun-equally-a-source-of-free energy/office-two-solar-energy-reaching-the-earths-surface/
- ↑ For some fun information on perihelion and aperihelion see NASA's page (accessed April 20th, 2015): https://solarsystem.nasa.gov/scitech/display.cfm?ST_ID=2517
- ↑ NASA World Observatory. (April 13, 2018). Sunlight Angle [Online]. Bachelor: https://earthobservatory.nasa.gov/Features/EnergyBalance/page2.php
- ↑ NASA Earth Observatory. (April 27, 2015). Climate and World's Energy Budget [Online]. Available: http://earthobservatory.nasa.gov/Features/EnergyBalance/
- ↑ Oklahoma Climatological Survey. (April four, 2015). Earth's Energy Budget [Online]. Available: http://okfirst.mesonet.org/train/meteorology/EnergyBudget.html
- ↑ Created internally by a member of the Energy Education team
- ↑ 8.0 eight.1 C. Julian Chen. (April 13, 2018). Physics of Solar Energy, 1st ed. Hoboken, NJ, The states.: John Wiley & Sons, 2011
- ↑ Wikimedia Commons. (Apr 16, 2018). Solar Spectrum [Online]. Available: https://commons.wikimedia.org/wiki/File:Solar_Spectrum.png
- ↑ National Geographic. (April 4, 2015). Solar Free energy [Online]. Available: http://surroundings.nationalgeographic.com/environment/global-warming/solar-power-contour/
Most of the Energy From the Sun Travels to Earth in the Form of
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