Physics of solar energy and its applications - Solar Energy Sciences and Engineering Applications - page 2

radiant energy with a range of wavelengths and intensities, a nuclear fusion-fission-
fusion reaction is happening inside the core of the Sun. The nuclear processes of the Sun
create tremendous amounts of energy which are sometimes devastating due to the
power of nuclear processes. The power generated by the Sun is almost endless and the
human benefit from it is expected to last for countless generations to come.
The energy generated in the Sun is transmitted to its surface through convection
and radiation. From the surface, the energy is transmitted to its surroundings through
solar radiation. This is a consequence of space being a vacuum from which both
conductive and convective modes of energy transmission are eliminated. The solar
energy available in the upper atmosphere of the Earth is almost constant and depends
on the motions and distance between the Earth and the Sun associated with the constant
rotation and revolution of the Earth around the Sun and the nuclear activities of the
Sun. As the Earth has a layer of atmosphere, the available solar energy in the upper
atmosphere of the Earth is reduced in transmission before it reaches the surface of the
Earth, depending on the weather and climatic conditions, surface locations and local
activities such as heavy smokes from wildfires.
The net energy of the Sun, reaching the surface of the Earth in the form of radiant
energy, has different intensities. The intensities depend on the radiant energy wave
spectrum. The radiant energy wave spectrum is generally classified as short wave (0
to 300 nanometer), infrared (300 to 750 nanometer) and long wave (750 nanometer
and above). With these different radiant energy wave spectrum energy intensities,
utilization of solar energy is very interesting and for different applications depends on
a variety of techniques and methods.
The radiant energy from the Sun has been naturally utilized by different terrestrial
living organisms for millions of years. Early humans utilized solar energy in different
applications including food production, cloth making and others. As modern civi-
lization demands more energy, alternative sources can be investigated and attention
to solar energy and its provider, the Sun, becomes an interesting topic for the mod-
ern world. There are many concepts, methods, ideas and practical solutions both for
simple and for more advanced utilization of radiant energy from the Sun. As global
demand is for clean energy sources which are potentially renewable and inexhaustible,
solar energy becomes the center of attention.
Demand for conventional energy sources has increased tremendously since the start
of the industrial revolution. Conventional energy sources are carbon-based, including
coal, oil and gas, and burning these sources creates large amounts of carbon dioxide
which is a so-called greenhouse gas. The greenhouses gases are responsible for the
increase of the Earth's temperature through trapping the Sun's radiant energy as it
reflects from the surface of the Earth. Hence, massive consumption of carbon-based
conventional energy sources has major future effects - depletion of the energy stock
resulting in increased prices, political issues related to energy shortage and increase of
the Earth temperature as human demand for better comfort increases. Moreover there
are other effects on biological and agricultural production.
As the population, urbanization, industrialization and demand for better human
comfort increase, it is expected that the demand for energy consumption will
increase. The rapid increase in demand for energy is associated with rapid industrial-
ization of the developing world. China and India are expected to contribute a bigger
share in the rapid increase of energy consumption. Latin America and South East Asia