Category Photovoltaics is the process of converting

DIRECT AND DIFFUSE RADIATION

Sunlight passing through the earth’s atmosphere is attenuated, or reduced, by about 30% by the time it reaches the earth’s surface due to such effects as (Gast, 1960;

Iqbal, 1983):

1. Rayleigh scattering by molecules in the atmosphere, particularly at short wavelengths (~^-4 dependence)

2. Scattering by aerosols and dust particles.

3. Absorption by atmospheric gases such as oxygen, ozone, water vapour and carbon dioxide (CO2).

The latter produces the absorption bands apparent in Fig. 1.3. Wavelengths below

0. 3 pm are strongly absorbed by ozone. Depletion of ozone from the atmosphere allows more of this short wavelength light to reach the earth, with consequent harmful effects on biological systems...

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THE SUN AND ITS RADIATION

The sun is a hot sphere of gas heated by nuclear fusion reactions at its centre (Quaschning, 2003). Internal temperatures reach a very warm 20 million K. As indicated in Fig. 1.2, the intense radiation from the interior is absorbed by a layer of hydrogen ions closer to the sun’s surface. Energy is transferred by convection through this optical barrier and then re-radiated from the outer surface of the sun, the photosphere. This emits radiation approximating that from a blackbody with a temperature of nearly 6000 K, as shown in Fig. 1.3.

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Figure 1.3...

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THE CHARACTERISTICS OF SUNLIGHT

1.1 PARTICLE-WAVE DUALITY

Our understanding of the nature of light has changed back and forth over the past few centuries between two apparently conflicting viewpoints. A highly readable account of the evolution of quantum theory is given in Gribben (1984). In the late 1600s, Newton’s mechanistic view of light as being made up of small particles prevailed. By the early 1800s, experiments by both Young and Fresnel had shown interference effects in light beams, indicating that light was made up of waves. By the 1860s, Maxwell’s theories of electromagnetic radiation were accepted, and light was understood to be part of a wide spectrum of electromagnetic waves with different wavelengths...

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Photovoltaics is the process of converting

S. R. Wenham M. A. Green M. E. Watt R. Corkish

Photovoltaics is the process of converting sunlight directly into electricity using solar cells. The first photovoltaic device was demonstrated in 1839 by Edmond Becquerel, as a young 19 year old working in his father’s laboratory in France. However, the understanding and exploitation of this effect was to depend on some of the most important scientific and technological developments of the 20th century. One is the development of quantum mechanics, one of the major intellectual achievements of the 20th century. Another, dependent on the first, is the development of semiconductor technology, which has been responsible for the pervasive electronics revolution and the photonics revolution now gathering pace...

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