YOUKO

YOUKO (The Feature Source Of Energy)
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2/24/2015 YOUKO (The Feature Source Of Energy)
Seminar On
YOUKO(The feature source of energy)
Guided by: Mr. N. Sreekanth Presented By: R. Vigneswar
Roll no: 113A1A0206
Contents:
 Abstract
 About Sun
 Energy From The Sun
 Energy That Falls On The Earth
 Energy That Is Usable
 Collection Of Energy
 Applications Of Collected Energy
 Storage Of Energy Collected
 Conclusion
Abstract:
In this presentation I’m going to tell you about the solar energy usage and applications
of solar energy, and storage methods. How much of energy is realizing from the sun in which
how much of energy is falling on the earth and how much of energy is utilizing by us.
About Sun:
The Sun is the star at the center of the Solar System. It is by far the most important
source of energy for life on Earth. The Sun is a nearly perfect spherical ball of hot plasma,
with internal convective motion that generates a magnetic field via a dynamo process. The
diameter of the Sun is about 109 times that of Earth, and it has a mass about 330,000 times
that of Earth, accounting for about 99.86% of the total mass of the Solar System. Chemically,
about three quarters of the Sun's mass consists of hydrogen, whereas the rest is mostly

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helium, and much smaller quantities of heavier elements, including oxygen, carbon, neon
and iron.
The Sun is a G-type main sequence star (G2V) based on spectral class and it is
informally designated as a yellow dwarf. It formed approximately 4.567 billion years ago
from the gravitational collapse of a region within a large molecular cloud. Most of the matter
gathered in the center, whereas the rest flattened into an orbiting disk that became the Solar
System. The central mass became increasingly hot and dense, eventually initiating
thermonuclear fusion in its core. It is thought that almost all stars form by this process. The
Sun is roughly middle age and has not changed dramatically for four billion years, and will
remain fairly stable for four billion more. However, after hydrogen fusion in its core has
stopped, the Sun will undergo severe changes and become a red giant. It is calculated that
the Sun will become sufficiently large to engulf the current orbits of Mercury, Venus, and
possibly Earth.
The enormous effect of the Sun on the Earth has been recognized since prehistoric
times, and the Sun has been regarded by some cultures as a deity. Earth's movement around
the Sun is the basis of the solar calendar, which is the predominant calendar in use today.
Name and etymology:
The English proper noun Sun developed from Old English sunne and may be related
to south. Cognates to English sun appear in other Germanic languages, including Old Frisian
sunne, sonne, Old Saxon sunna, Middle Dutch sonne, modern Dutch zon, Old High German
sunna, modern German Sonne, Old Norse sunna, and Gothic sunnō. All Germanic terms for
the Sun stem from ProtoGermanic *sunnōn. The Sun is viewed as a goddess in Germanic
paganism, Sól/Sunna. Scholars theorize that the Sun, as a Germanic goddess, may represent
an extension of an earlier ProtoIndoEuropean Sun deity due to Indo-European linguistic
connections between Old Norse Sól, Sanskrit Surya, Gaulish Sulis, Lithuanian Saulė, and
Slavic Solntse. The English weekday name Sunday stems from Old English (Sunnandæg;
"Sun's day", from before 700) and is ultimately a result of a Germanic interpretation of Latin
dies solis, itself a translation of the Greek ἡμέρα ἡλίου (hēméra hēlíou). The Latin name for
the Sun, Sol, is widely known but is not common in general English language use; The
adjectival form is the related word solar. The term sol is also used by planetary astronomers

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to refer to the duration of a solar day on another planet, such as Mars. A mean Earth solar
day is approximately 24 hours, whereas a mean Martian 'sol' is 24 hours, 39 minutes, and
35.244 seconds.
Characteristics:
The Sun is a G-type main sequence star that comprises about 99.86% of the mass of
the Solar System. Once regarded by astronomers as a small and relatively insignificant star,
the Sun has an absolute magnitude of +4.83. This is now estimated to be brighter than about
85% of the stars in the Milky Way, most of which are red dwarfs. The Sun is a Population I,
or heavy element rich, star. The formation of the Sun may have been triggered by shockwaves
from one or more nearby supernovae. This is suggested by a high abundance of heavy
elements in the Solar System, such as gold and uranium, relative to the abundances of these
elements in so called Population II, heavy element poor, stars. These elements could most
plausibly have been produced by endothermic nuclear reactions during a supernova, or by
transmutation through neutron absorption within a massive second generation star.
The Sun is by far the brightest object in the sky, with an apparent magnitude of −26.74.
This is about 13 billion times brighter than the next brightest star, Sirius, which has an
apparent magnitude of −1.46. The mean distance of the Sun to Earth is approximately 1
astronomical unit (about 150,000,000 km; 93,000,000 mi), though the distance varies as
Earth moves from perihelion in January to aphelion in July. At this average distance, light
travels from the Sun to Earth in about 8 minutes and 19 seconds. The energy of this sunlight
supports almost all life[d] on Earth by photosynthesis, and drives Earth's climate and weather.
The Sun's radius can be measured from its center to the edge of the photosphere, the
apparent visible surface of the Sun. The Sun is a near perfect sphere with an oblateness
estimated at about 9 millionths, which means that its polar diameter differs from its
equatorial diameter by only 10 Kilometers (6.2 mi). The centrifugal effect of the Sun's
rotation is 18 million times weaker than the surface gravity at the Sun's equator. The tidal
effect of the planets is even weaker and does not significantly affect the shape of the Sun. The
Sun rotates faster at its equator than at its poles. This differential rotation is caused by
convective motion due to heat transport and the Coriolis force due to the Sun's rotation. In a

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frame of reference defined by the stars, the rotational period is approximately 25.6 days at
the equator and 33.5 days at the poles. Viewed from Earth as it orbits the Sun, the apparent
rotational period of the Sun at its equator is about 28 days. The Sun does not have a definite
boundary, and in its outer parts its density decreases exponentially with increasing distance
from its center. The solar interior is not directly observable, and the Sun itself is opaque to
electromagnetic radiation. However, just as seismology uses waves generated by earthquakes
to reveal the interior structure of Earth, the discipline of helioseismology makes use of
pressure waves (infrasound) traversing the Sun's interior to measure and visualize its inner
structure. Computer modeling of the Sun is also used as a theoretical tool to investigate its
deeper layers. During a total solar eclipse, when the disk of the Sun is covered by that of the
Moon, the Sun's surrounding atmosphere, the corona, can be seen. As the corona expands
outward into space, creating the solar wind, a stream of charged particles. The spatial extent
of the influence of the solar wind defines the heliosphere, a "bubble" in the interstellar
medium that is roughly 100 astronomical units in radius, the largest continuous structure
in the Solar System.[40][41] The outer boundary of the heliosphere is the heliopause.
Structure:

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Core:
The core of the Sun extends from the center to about 20–25% of the solar radius. It
has a density of up to 150 g/cm3 (about 150 times the density of water) and a temperature
of close to 15.7 million kelvin (K). By contrast, the Sun's surface temperature is approximately
5,800 K. Recent analysis of SOHO mission data favors a faster rotation rate in the core than
in the rest of the radiative zone. Through most of the Sun's life, energy is produced by nuclear
fusion through a series of steps called the p–p (proton– proton) chain; This process converts
hydrogen into helium. Only 0.8% of the energy generated in the Sun comes from the CNO
cycle. The core is the only region in the Sun that produces an appreciable amount of thermal
energy through fusion; 99% of the power is generated within 24% of the Sun's radius, and
by 30% of the radius, fusion has stopped nearly entirely. The rest of the Sun is heated by this
energy that is transferred outwards, respectively, through the radiative and convection
zones. The energy produced by fusion in the core must then travel through many successive
layers to the solar photosphere before it escapes into space as sunlight or the kinetic energy
of particles. The proton–proton chain occurs around 9.2 × 1037 times each second in the
core. Because this reaction uses four free protons (hydrogen nuclei), it converts about 3.7 ×
1038 protons to alpha particles (helium nuclei) every second (out of a total of ~8.9 × 1056
free protons in the Sun), or about 6.2 × 1011 kg/s. Fusing hydrogen into helium releases
around 0.7% of the fused mass as energy, so the Sun releases energy at the mass–energy
conversion rate of 4.26 million metric tons per second, 384.6 yotta watts (3.846 × 1026 W),
or 9.192 × 1010 megatons of TNT per second. Theoretical models of the Sun's interior
indicate a power density of approximately 276.5 W/m3, a value that more nearly
approximates reptile metabolism than a thermonuclear bomb. Peak power production in the
Sun has been compared to the volumetric heat generated in an active compost heap. The
tremendous power output of the Sun is not due to its high power per volume, but instead due
to its large size. The fusion rate in the core is in a self-correcting equilibrium: a slightly
higher rate of fusion would cause the core to heat up more and expand slightly against the
weight of the outer layers, reducing the fusion rate and correcting the perturbation; And a
slightly lower rate would cause the core to cool and shrink slightly, increasing the fusion
rate and again reverting it to its present level.

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Radiative zone:
From the core out to about 0.7 solar radii, thermal radiation is the primary means of
energy transfer. This zone is not regulated by thermal convection; However the temperature
drops from approximately 7 to 2 million kelvin with increasing distance from the core. This
temperature gradient is less than the value of the adiabatic lapse rate and hence cannot drive
convection. Energy is transferred by radiation—ions of hydrogen and helium emit photons,
which travel only a brief distance before being reabsorbed by other ions. The density drops
a hundredfold (from 20 g/cm3 to only 0.2 g/cm3) from 0.25 solar radii to the top of the
radiative zone.
Tachocline:
The radiative zone and the convective zone are separated by a transition layer, the
Tachocline. This is a region where the sharp regime change between the uniform rotation of
the radiative zone and the differential rotation of the convection zone results in a large
shear—a condition where successive horizontal layers slide past one another. The fluid
motions found in the convection zone above, slowly disappear from the top of this layer to
its bottom, matching the calm characteristics of the radiative zone on the bottom. Presently,
it is hypothesized (see Solar dynamo) that a magnetic dynamo within this layer generates the
Sun's magnetic field.
Convective zone:
In the Sun's outer layer, from its surface to approximately 200,000 km below (70% of
the solar radius from the center), the temperature is lower than in the radiative zone and
heavier atoms are not fully ionized. As a result, radiative heat transport is less effective. The
density of the plasma is low enough to allow convective currents to develop. Material heated
at the Tachocline picks up heat and expands, thereby reducing its density and allowing it to
rise. As a result, thermal convection develops as thermal cells carry the majority of the heat
outward to the Sun's photosphere. Once the material diffusively and radiatively cools just
beneath the photospheric surface, its density increases, and it sinks to the base of the
convection zone, where it picks up more heat from the top of the radiative zone and the
convective cycle continues. At the photosphere, the temperature has dropped to 5,700 K and

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the density to only 0.2 g/m3 (about 1/6,000th the density of air at sea level). The thermal
columns in the convection zone form an imprint on the surface of the Sun as the solar
granulation and supergranulation. The turbulent convection of this outer part of the solar
interior sustains "small-scale" dynamo action over the near surface volume of the Sun. The
Sun's thermal columns are Bénard cells and take the shape of hexagonal prisms.
Photosphere:
The visible surface of the Sun, the photosphere, is the layer below which the Sun
becomes opaque to visible light. Above the photosphere visible sunlight is free to propagate
into space, and its energy escapes the Sun entirely. The change in opacity is due to the
decreasing amount of H− ions, which absorb visible light easily. Conversely, the visible light
we see is produced as electrons react with hydrogen atoms to produce H− ions. The
photosphere is tens to hundreds of kilometers thick, being slightly less opaque than air on
Earth. Because the upper part of the photosphere is cooler than the lower part, an image of
the Sun appears brighter in the center than on the edge or limb of the solar disk, in a
phenomenon known as limb darkening. The spectrum of sunlight has approximately the
spectrum of a blackbody radiating at about 6,000K, interspersed with atomic absorption
lines from the tenuous layers above the photosphere. The photosphere has a particle density
of ~1023 m−3 (about 0.37% of the particle number per volume of Earth's atmosphere at sea
level). The photosphere is not fully ionized—the extent of ionization is about 3%, leaving
almost all of the hydrogen in atomic form. During early studies of the optical spectrum of
the photosphere, some absorption lines were found that did not correspond to any chemical
elements then known on Earth. In 1868, Norman Lockyer hypothesized that these absorption
lines were caused by a new element that he dubbed helium, after the Greek Sun god Helios.
Twenty-five years later, helium was isolated on Earth.
Atmosphere:
The parts of the Sun above the photosphere are referred to collectively as the solar
atmosphere. They can be viewed with telescopes operating across the electromagnetic
spectrum, from radio through visible light to gamma rays, and comprise five principal zones:
the temperature minimum, the chromosphere, the transition region, the corona, and the
heliosphere. The coolest layer of the Sun is a temperature minimum region about 500 km

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above the photosphere, with a temperature of about 4,100 K. This part of the Sun is cool
enough to allow the existence of simple molecules such as carbon monoxide and water,
which can be detected via their absorption spectra. The chromosphere, transition region, and
corona are much hotter than the surface of the Sun. The reason is not well understood, but
evidence suggests that Alfven waves may have enough energy to heat the corona. Above the
temperature minimum layer is a layer about 2,000 km thick, dominated by a spectrum of
emission and absorption lines. It is called the chromosphere from the Greek root Chroma,
meaning color, because the chromosphere is visible as a colored flash at the beginning and
end of total solar eclipses. The temperature in the chromosphere increases gradually with
altitude, ranging up to around 20,000 K near the top. In the upper part of the chromosphere
helium becomes partially ionized. Above the chromosphere, in a thin (about 200 km)
transition region, the temperature rises rapidly from around 20,000 K in the upper
chromosphere to coronal temperatures closer to 1,000,000 K. The temperature increase is
facilitated by the full ionization of helium in the transition region, which significantly
reduces radiative cooling of the plasma. The transition region does not occur at a well-
defined altitude. Rather, it forms a kind of nimbus around chromospheric features such as
spicules and filaments, and is in constant, chaotic motion. The transition region is not easily
visible from Earth's surface, but is readily observable from space by instruments sensitive to
the extreme ultraviolet portion of the spectrum.
The corona is the next layer of the Sun. The low corona, near the surface of the Sun,
has a particle density around 1015–1016 m−3. The average temperature of the corona and
solar wind is about 1,000,000– 2,000,000 K; However, in the hottest regions it is 8,000,000–
20,000,000 K. Although no complete theory yet exists to account for the temperature of the
corona, at least some of its heat is known to be from magnetic reconnection. The corona is
the extended atmosphere of the Sun, which has a volume much larger than the volume
enclosed by the Sun's photosphere. Waves at the outer surface of the corona that randomly
blow even further from the Sun is called the solar wind, and is one of the ways the Sun
influences the whole Solar System. The heliosphere, the tenuous outermost atmosphere of
the Sun, is filled with the solar wind plasma. This outermost layer of the Sun is defined to
begin at the distance where the flow of the solar wind becomes superalfvénic—that is, where
the flow becomes faster than the speed of Alfven waves, at approximately 20 solar radii (0.1
AU). Turbulence and dynamic forces in the heliosphere cannot affect the shape of the solar

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corona within, because the information can only travel at the speed of Alfven waves. The
solar wind travels outward continuously through the heliosphere, forming the solar
magnetic field into a spiral shape, until it impacts the heliopause more than 50 AU from the
Sun. In December 2004, the Voyager 1 probe passed through a shock front that is thought
to be part of the heliopause. Both of the Voyager probes have recorded higher levels of
energetic particles as they approach the boundary. The heliosphere extends to the outer
fringe of the Solar System, farther than the orbit of Pluto, is defined to end at the heliopause,
which is the end of influence from the Sun, and is the boundary with the interstellar medium.
Photons and neutrinos:
High-energy gamma ray photons initially released with fusion reactions in the
core are almost immediately absorbed by the solar plasma of the radiative zone, usually after
traveling only a few millimeters. Reemission happens in a random direction and usually at a
slightly lower energy. With this sequence of emissions and absorptions, it takes a long time
for radiation to reach the Sun's surface. Estimates of the photon travel time range between
10,000 and 170,000 years. In contrast, it takes only 2.3 seconds for the neutrinos, which
account for about 2% of the total energy production of the Sun, to reach the surface. Because
energy transport in the Sun is a process that involves photons in thermodynamic equilibrium
with matter, the time scale of energy transport in the Sun is longer, on the order of
30,000,000 years. This is the time it would take the Sun to return to a stable state, if the rate
of energy generation in its core were suddenly changed.
Each gamma ray in the Sun's core is converted into several million photons of visible
light before escaping into space. Neutrinos are also released by the fusion reactions in the
core, but, unlike photons, they rarely interact with matter, so almost all are able to escape the
Sun immediately. For many years measurements of the number of neutrinos produced in the
Sun were lower than theories predicted by a factor of 3. This discrepancy was resolved in
2001 through the discovery of the effects of neutrino oscillation: the Sun emits the number
of neutrinos predicted by the theory, but neutrino detectors were missing 2∕3 of them because
the neutrinos had changed flavor by the time they were detected.

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Energy from the Sun:
The Earth receives 174 peta-watts (PW) of incoming solar radiation (insolation) at the
upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed
by clouds, oceans and land masses. The spectrum of solar light at the Earth's surface is mostly
spread across the visible and near infrared ranges with a small part in the near ultraviolet.
Earth's land surface, oceans and atmosphere absorb solar radiation, and this raises their
temperature. Warm air containing evaporated water from the oceans rises, causing
atmospheric circulation or convection. When the air reaches a high altitude, where the
temperature is low, water vapor condenses into clouds, which rain onto the Earth's surface,
completing the water cycle. The latent heat of water condensation amplifies convection,
producing atmospheric phenomena such as wind, cyclones and anticyclones. Sunlight
absorbed by the oceans and land masses keeps the surface at an average temperature of 14°C.
By photosynthesis green plants convert solar energy into chemical energy, which produces
food, wood and the biomass from which fossil fuels are derived.
The total solar energy absorbed by Earth's atmosphere, oceans and land masses is
approximately 3,850,000 exa-joules (EJ) per year. In 2002, this was more energy in one
hour than the world used in one year. Photosynthesis captures approximately 3,000 EJ per
year in biomass. The technical potential available from biomass is from 100–300 EJ/year. The

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amount of solar energy reaching the surface of the planet is so vast that in one year it is about
twice as much as will ever be obtained from all of the Earth's nonrenewable resources of
coal, oil, natural gas, and mined uranium combined, Solar energy can be harnessed at
different levels around the world, mostly depending on distance from the equator.
Early commercial adaption:
In 1897, Frank Shuman, a U.S. inventor, engineer and solar energy pioneer built a
small demonstration solar engine that worked by reflecting solar energy onto square boxes
filled with ether, which has a lower boiling point than water, and were fitted internally with
black pipes which in turn powered a steam engine. In 1908 Shuman formed the Sun Power
Company with the intent of building larger solar power plants. He, along with his technical
advisor A.S.E. Ackermann and British physicist Sir Charles Vernon Boys, developed an
improved system using mirrors to reflect solar energy upon collector boxes, increasing
heating capacity to the extent that water could now be used instead of ether. Shuman then
constructed a full scale steam engine powered by low pressure water, enabling him to patent
the entire solar engine system by 1912.
Shuman built the world’s first solar thermal power station in Maadi, Egypt, between
1912 and 1913. Shuman’s plant used parabolic troughs to power a 45–52 kilowatts (60–
70hp) engine that pumped more than 22,000litres (4,800 imp gal; 5,800 US gal) of water
per minute from the Nile River to adjacent cotton fields. Although the outbreak of World
War I and the discovery of cheap oil in the 1930s discouraged the advancement of solar
energy, Shuman’s vision and basic design were resurrected in the 1970s with a new wave of
interest in solar thermal energy. In 1916 Shuman was quoted in the media advocating solar
energy's utilization, saying:

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We have proved the commercial profit of sun power in the tropics and have more
particularly proved that after our stores of oil and coal are exhausted the human race can
receive unlimited power from the rays of the sun.
Applications of solar technology:
Solar energy refers primarily to the use of solar radiation for practical ends. However,
all renewable energies, other than geothermal and tidal, derive their energy from the sun.
Solar technologies are broadly characterized as either passive or active depending on the
way they capture, convert and distribute sunlight. Active solar techniques use photovoltaic
panels, pumps, and fans to convert sunlight into useful outputs. Passive solar techniques
include selecting materials with favorable thermal properties, designing spaces that
naturally circulate air, and referencing the position of a building to the Sun. Active solar
technologies increase the supply of energy and are considered supply side technologies,
while passive solar technologies reduce the need for alternate resources and are generally
considered demand side technologies.
Architecture and urban planning:
Sunlight has influenced building design since the beginning of architectural history.
Advanced solar architecture and urban planning methods were first employed by the Greeks
and Chinese, who oriented their buildings toward the south to provide light and warmth.
The common features of passive solar architecture are orientation relative to the Sun,
compact proportion (a low surface area to volume ratio), selective shading (overhangs) and
thermal mass. When these features are tailored to the local climate and environment they
can produce well it spaces that stay in a comfortable temperature range. Socrates' Megaron
House is a classic example of passive solar design. The most recent approaches to solar design
use computer modeling tying together solar lighting, heating and ventilation systems in an
integrated solar design package. Active solar equipment such as pumps, fans and switchable
windows can complement passive design and improve system performance. Urban heat
islands (UHI) are metropolitan areas with higher temperatures than that of the surrounding
environment. The higher temperatures are a result of increased absorption of the Solar light

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by urban materials such as asphalt and concrete, which have lower albedos and higher heat
capacities than those in the natural environment. A straightforward method of counteracting
the UHI effect is to paint buildings and roads white and plant trees. Using these methods, a
hypothetical "cool communities" program in Los Angeles has projected that urban
temperatures could be reduced by approximately 3 °C at an estimated cost of US$1 billion,
giving estimated total annual benefits of US$530 million from reduced air conditioning costs
and healthcare savings.
Agriculture and horticulture:
Agriculture and horticulture seek to optimize the capture of solar energy in order to
optimize the productivity of plants. Techniques such as timed planting cycles, tailored row
orientation, staggered heights between rows and the mixing of plant varieties can improve
crop yields. While sunlight is generally considered a plentiful resource, the exceptions
highlight the importance of solar energy to agriculture. During the short growing seasons of
the Little Ice Age, French and English farmers employed fruit walls to maximize the collection
of solar energy. These walls acted as thermal masses and accelerated ripening by keeping
plants warm. Early fruit walls were built perpendicular to the ground and facing south, but
over time, sloping walls were developed to make better use of sunlight. In 1699, Nicolas Fatio
de Duillier even suggested using a tracking mechanism which could pivot to follow the Sun.
Applications of solar energy in agriculture aside from growing crops include pumping water,
drying crops, brooding chicks and drying chicken manure. More recently the technology has
been embraced by vinters, who use the energy generated by solar panels to power grape
presses. Greenhouses convert solar light to heat, enabling year round production and the
growth (in enclosed environments) of specialty crops and other plants not naturally suited
to the local climate. Primitive greenhouses were first used during Roman times to produce
cucumbers year round for the Roman emperor Tiberius. The first modern greenhouses were
built in Europe in the 16th century to keep exotic plants brought back from explorations
abroad. Greenhouses remain an important part of horticulture today, and plastic transparent
materials have also been used to similar effect in poly-tunnels and row covers.

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Transport and reconnaissance:
Development of a solar powered car has been an engineering goal since the 1980s.
The World Solar Challenge is a biannual solar powered car race, where teams from
universities and enterprises compete over 3,021 kilometers (1,877 mi) across central
Australia from Darwin to Adelaide. In 1987, when it was founded, the winner's average
speed was 67 kilometers per hour (42 mph) and by 2007 the winner's average speed had
improved to 90.87 kilometers per hour (56.46 mph). The North American Solar Challenge
and the planned South African Solar Challenge are comparable competitions that reflect an
international interest in the engineering and development of solar powered vehicles.
Some vehicles use solar panels for auxiliary power, such as for air conditioning, to
keep the interior cool, thus reducing fuel consumption.
In 1975, the first practical solar boat was constructed in England. By 1995, passenger
boats incorporating PV panels began appearing and are now used extensively. In 1996,
Kenichi Horie made the first solar powered crossing of the Pacific Ocean, and the sun21
catamaran made the first solar powered crossing of the Atlantic Ocean in the winter of
2006–2007. There were plans to circumnavigate the globe in 2010.

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In 1974, the unmanned Astro Flight Sunrise plane made the first solar flight. On 29
April 1979, the Solar Riser made the first flight in a solar powered, fully controlled, man
carrying flying machine, reaching an altitude of 40 feet (12 m). In 1980, the Gossamer
Penguin made the first piloted flights powered solely by photovoltaic. This was quickly
followed by the Solar Challenger which crossed the English Channel in July 1981. In 1990
Eric Scott Raymond in 21 hops flew from California to North Carolina using solar power.
Developments then turned back to unmanned aerial vehicles (UAV) with the Pathfinder
(1997) and subsequent designs, culminating in the Helios which set the altitude record for a
non-rocket propelled aircraft at 29,524 meters (96,864 ft.) in 2001. The Zephyr, developed
by BAE Systems, is the latest in a line of record breaking solar aircraft, making a 54hour flight
in 2007, and month long flights were envisioned by 2010.
A solar balloon is a black balloon that is filled with ordinary air. As sunlight shines on
the balloon, the air inside is heated and expands causing an upward buoyancy force, much
like an artificially heated hot air balloon. Some solar balloons are large enough for human
flight, but usage is generally limited to the toy market as the surface area to pay load weight
ratio is relatively high.
Solar thermal:
Solar thermal technologies can be used for water heating, space heating, and space
cooling and process heat generation.

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Water heating:
Solar hot water systems use sunlight to heat water. In low geographical latitudes
(below 40 degrees) from 60 to 70% of the domestic hot water use with temperatures up to
60 °C can be provided by solar heating systems. The most common types of solar water
heaters are evacuated tube collectors (44%) and glazed flat plate collectors (34%) generally
used for domestic hot water; and unglazed plastic collectors (21%) used mainly to heat
swimming pools.
As of 2007, the total installed capacity of solar hot water systems is approximately 154
giga watts (207,000,000 hp). China is the world leader in their deployment with 70 GW
(94,000,000 hp) installed as of 2006 and a long term goal of 210 GW (280,000,000 hp) by
2020. Israel and Cyprus are the per capita leaders in the use of solar hot water systems with
over 90% of homes using them. In the United States, Canada and Australia heating swimming

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pools is the dominant application of solar hot water with an installed capacity of 18 GW as
of 2005.
Heating, cooling and ventilation:
In the United States, heating, ventilation and air conditioning (HVAC) systems account
for 30% (4.65 EJ) of the energy used in commercial buildings and nearly 50% (10.1 EJ) of
the energy used in residential buildings. Solar heating, cooling and ventilation technologies
can be used to offset a portion of this energy. Thermal mass is any material that can be used
to store heat—heat from the Sun in the case of solar energy. Common thermal mass materials

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include stone, cement and water. Historically they have been used in arid climates or warm
temperate regions to keep buildings cool by absorbing solar energy during the day and
radiating stored heat to the cooler atmosphere at night. However they can be used in cold
temperate areas to maintain warmth as well. The size and placement of thermal mass depend
on several factors such as climate, day lighting and shading conditions. When properly
incorporated, thermal mass maintains space temperatures in a comfortable range and
reduces the need for auxiliary heating and cooling equipment. A solar chimney (or thermal
chimney, in this context) is a passive solar ventilation system composed of a vertical shaft
connecting the interior and exterior of a building. As the chimney warms, the air inside is
heated causing an updraft that pulls air through the building. Performance can be improved
by using glazing and thermal mass materials in a way that mimics greenhouses. Deciduous
trees and plants have been promoted as a means of controlling solar heating and cooling.
When planted on the southern side of a building in the northern hemisphere or the northern
side in the southern hemisphere, their leaves provide shade during the summer, while the
bare limbs allow light to pass during the winter. Since bare, leafless trees shade 1/3 to 1/2 of
incident solar radiation, there is a balance between the benefits of summer shading and the
corresponding loss of winter heating. In climates with significant heating loads, deciduous
trees should not be planted on the Equator facing side of a building because they will
interfere with winter solar availability. They can, however, be used on the east and west sides
to provide a degree of summer shading without appreciably affecting winter solar gain.
Water treatment:

19 | P a g e
Solar distillation can be used to make saline or brackish water potable. The first
recorded instance of this was by 16thcentury Arab alchemists. A large-scale solar distillation
project was first constructed in 1872 in the Chilean mining town of Las Salinas. The plant,
which had solar collection area of 4,700 m2 (51,000 sq. ft.), could produce up to 22,700 L
(5,000 imp gal; 6,000 US gal) per day and operate for 40 years.[62] Individual still designs
include single slope, double slope (or greenhouse type), vertical, conical, inverted absorber,
multiwick, and multiple effect. These stills can operate in passive, active, or hybrid modes.
Double slope stills are the most economical for decentralized domestic purposes, while active
multiple effect units are more suitable for large-scale applications. Solar water disinfection
(SODIS) involves exposing water filled plastic polyethylene terephthalate (PET) bottles to
sunlight for several hours. Exposure times vary depending on weather and climate from a
minimum of six hours to two days during fully overcast conditions. It is recommended by
the World Health Organization as a viable method for household water treatment and safe
storage. Over two million people in developing countries use this method for their daily
drinking water. Solar energy may be used in a water stabilization pond to treat waste water
without chemicals or electricity. A further environmental advantage is that algae grow in
such ponds and consume carbon dioxide in photosynthesis, although algae may produce
toxic chemicals that make the water unusable.
Process heat:
Solar concentrating technologies such as parabolic dish, trough and Scheffler
reflectors can provide process heat for commercial and industrial applications. The first
commercial system was the Solar Total Energy Project (STEP) in Shenandoah, Georgia, USA
where a field of 114 parabolic dishes provided 50% of the process heating, air conditioning
and electrical requirements for a clothing factory. This grid connected cogeneration system
provided 400 kW of electricity plus thermal energy in the form of 401 kW steam and 468
kW chilled water, and had a one hour peak load thermal storage. Evaporation ponds are
shallow pools that concentrate dissolved solids through evaporation. The use of evaporation
ponds to obtain salt from sea water is one of the oldest applications of solar energy. Modern
uses include concentrating brine solutions used in leach mining and removing dissolved
solids from waste streams. Clothes lines, clotheshorses, and clothes racks dry clothes through

20 | P a g e
evaporation by wind and sunlight without consuming electricity or gas. In some states of the
United States legislation protects the "right to dry" clothes.
Unglazed transpired collectors (UTC) are perforated sun facing walls used for
preheating ventilation air. UTCs can raise the incoming air temperature up to 22 °C (40 °F)
and deliver outlet temperatures of 45– 60 °C (113–140 °F). The short payback period of
transpired collectors (3 to 12 years) makes them a more cost effective alternative than glazed
collection systems. As of 2003, over 80 systems with a combined collector area of 35,000
square meters (380,000 sq. ft.) had been installed worldwide, including an 860 m2 (9,300
sq. ft.) collector in Costa Rica used for drying coffee beans and a 1,300 m2 (14,000 sq. ft.)
collector in Coimbatore, India, used for drying marigolds.
Cooking:
Solar cookers use sunlight for cooking, drying and pasteurization. They can be
grouped into three broad categories: box cookers, panel cookers and reflector cookers. The
simplest solar cooker is the box cooker first built by Horace de Saussure in 1767. A basic box
cooker consists of an insulated container with a transparent lid. It can be used effectively
with partially overcast skies and will typically reach temperatures of 90–150 °C (194–302
°F). Panel cookers use a reflective panel to direct sunlight onto an insulated container and
reach temperatures comparable to box cookers. Reflector cookers use various concentrating
geometries (dish, trough, Fresnel mirrors) to focus light on a cooking container. These

21 | P a g e
cookers reach temperatures of 315 °C (599 °F) and above but require direct light to function
properly and must be repositioned to track the Sun.
Electricity production:
Solar power is the conversion of sunlight into electricity, either directly using
photovoltaics (PV), or indirectly using concentrated solar power (CSP). CSP systems use lenses
or mirrors and tracking systems to focus a large area of sunlight into a small beam. PV
converts light into electric current using the photoelectric effect. Commercial CSP plants
were first developed in the 1980s. Since 1985 the eventually 354 MW SEGS CSP installation,
in the Mojave Desert of California, is the largest solar power plant in the world. Other large
CSP plants include the 150 MW Solnova Solar Power Station and the 100 MW Andasol solar
power station, both in Spain. The 250 MW Agua Caliente Solar Project, in the United States,
and the 221 MW Charanka Solar Park in India, are the world’s largest photovoltaic plants.
Solar projects exceeding 1 GW are being developed, but most of the deployed photovoltaics
are in small rooftop arrays of less than 5 kW, which are grid connected using net metering
and/or a feeding tariff.
Concentrated solar power:

22 | P a g e
Concentrating Solar Power (CSP) systems use lenses or mirrors and tracking systems
to focus a large area of sunlight into a small beam. The concentrated heat is then used as a
heat source for a conventional power plant. A wide range of concentrating technologies
exists; The most developed are the parabolic trough, the concentrating linear Fresnel
reflector, the Stirling dish and the solar power tower. Various techniques are used to track
the Sun and focus light. In all of these systems a working fluid is heated by the concentrated
sunlight, and is then used for power generation or energy storage.
Photovoltaics:
A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current
using the photoelectric effect. The first solar cell was constructed by Charles Fritts in the
1880s. In 1931 a German engineer, Dr Bruno Lange, developed a photo cell using silver
selenide in place of copper oxide. Although the prototype selenium cells converted less than
1% of incident light into electricity, both Ernst Werner von Siemens and James Clerk

23 | P a g e
Maxwell recognized the importance of this discovery. Following the work of Russell Ohl in
the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the
crystalline silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached
efficiencies of 4.5–6%. By 2012 available efficiencies exceed 20% and the maximum
efficiency of research photovoltaics is over 40%.
Fuel production:
Solar chemical processes use solar energy to drive chemical reactions. These processes
offset energy that would otherwise come from a fossil fuel source and can also convert solar
energy into storable and transportable fuels. Solar induced chemical reactions can be divided
into thermochemical or photochemical. A variety of fuels can be produced by artificial
photosynthesis. The multi electron catalytic chemistry involved in making carbon based fuels

24 | P a g e
(such as methanol) from reduction of carbon dioxide is challenging; A feasible alternative is
hydrogen production from protons, though use of water as the source of electrons (as plants
do) requires mastering the multi electron oxidation of two water molecules to molecular
oxygen. Some have envisaged working solar fuel plants in coastal metropolitan areas by
2050 – the splitting of sea water providing hydrogen to be run through adjacent fuel cell
electric power plants and the pure water byproduct going directly into the municipal water
system. Another vision involves all human structures covering the earth's surface (i.e., roads,
vehicles and buildings) doing photosynthesis more efficiently than plants.
Hydrogen production technologies been a significant area of solar chemical research
since the 1970s. Aside from electrolysis driven by photovoltaic or photochemical cells,
several thermochemical processes have also been explored. One such route uses
concentrators to split water into oxygen and hydrogen at high temperatures (2,300–2,600°C
or 4,200–4,700°F). Another approach uses the heat from solar concentrators to drive the
steam reformation of natural gas thereby increasing the overall hydrogen yield compared to
conventional reforming methods. Thermochemical cycles characterized by the
decomposition and regeneration of reactants present another avenue for hydrogen
production. The Sol zinc process under development at the Weizmann Institute uses a 1 MW
solar furnace to decompose zinc oxide (ZnO) at temperatures above 1,200°C (2,200°F). This
initial reaction produces pure zinc, which can subsequently be reacted with water to
produce hydrogen.
Energy storage methods:
Thermal mass systems can store solar energy in the form of heat at domestically useful
temperatures for daily or inter seasonal durations. Thermal storage systems generally use
readily available materials with high specific heat capacities such as water, earth and stone.
Well-designed systems can lower peak demand, shift time of use to off-peak hours and
reduce overall heating and cooling requirements.
Phase change materials such as paraffin wax and Glauber's salt are another thermal
storage media. These materials are inexpensive, readily available, and can deliver

25 | P a g e
domestically useful temperatures (approximately 64 °C or 147 °F). The "Dover House" (in
Dover, Massachusetts) was the first to use a Glauber's salt heating system, in 1948.
Solar energy can be stored at high temperatures using molten salts. Salts are an
effective storage medium because they are low-cost, have a high specific heat capacity and
can deliver heat at temperatures compatible with conventional power systems. The Solar Two
used this method of energy storage, allowing it to store 1.44 terajoules (400,000 kWh) in its
68 cubic meters (2,400 cu ft.) storage tank with an annual storage efficiency of about 99%.
Off-grid PV systems have traditionally used rechargeable batteries to store excess
electricity. With grid tied systems, excess electricity can be sent to the transmission grid,
while standard grid electricity can be used to meet shortfalls. Net metering programs give
household systems a credit for any electricity they deliver to the grid. This is handled by
'rolling back' the meter whenever the home produces more electricity than it consumes. If
the net electricity use is below zero, the utility then rolls over the kilowatt hour credit to the
next month. Other approaches involve the use of two meters, to measure electricity
consumed vs. electricity produced. This is less common due to the increased installation cost
of the second meter. Most standard meters accurately measure in both directions, making a
second meter unnecessary.
Pumped storage hydroelectricity stores energy in the form of water pumped when
energy is available from a lower elevation reservoir to a higher elevation one. The energy is

26 | P a g e
recovered when demand is high by releasing the water, with the pump becoming a
hydroelectric power generator.
Development, deployment and economics:
Beginning with the surge in coal use which accompanied the Industrial Revolution,
energy consumption has steadily transitioned from wood and biomass to fossil fuels. The
early development of solar technologies starting in the 1860s was driven by an expectation
that coal would soon become scarce. However development of solar technologies stagnated
in the early 20th century in the face of the increasing availability, economy, and utility of
coal and petroleum.
The 1973 oil embargo and 1979 energy crisis caused a reorganization of energy
policies around the world and brought renewed attention to developing solar technologies.
Deployment strategies focused on incentive programs such as the Federal Photovoltaic
Utilization Program in the US and the Sunshine Program in Japan. Other efforts included the

27 | P a g e
formation of research facilities in the US (SERI, now NREL), Japan (NEDO), and Germany
(Fraunhofer Institute for Solar Energy Systems ISE).
Commercial solar water heaters began appearing in the United States in the 1890s.
These systems saw increasing use until the 1920s but were gradually replaced by cheaper
and more reliable heating fuels. As with photovoltaics, solar water heating attracted renewed
attention as a result of the oil crises in the 1970s but interest subsided in the 1980s due to
falling petroleum prices. Development in the solar water heating sector progressed steadily
throughout the 1990s and growth rates have averaged 20% per year since 1999. Although
generally underestimated, solar water heating and cooling is by far the most widely deployed
solar technology with an estimated capacity of 154 GW as of 2007.
The International Energy Agency has said that solar energy can make considerable
contributions to solving some of the most urgent problems the world now faces:
The development of affordable, inexhaustible and clean solar energy technologies will
have huge longer term benefits. It will increase countries’ energy security through reliance
on an indigenous, inexhaustible and mostly import independent resource, enhance
sustainability, reduce pollution, lower the costs of mitigating climate change, and keep fossil
fuel prices lower than otherwise. These advantages are global. Hence the additional costs of
the incentives for early deployment should be considered learning investments; They must
be wisely spent and need to be widely shared.

28 | P a g e
In 2011, a report by the International Energy Agency found that solar energy
technologies such as photovoltaics, solar hot water and concentrated solar power could
provide a third of the world’s energy by 2060 if politicians commit to limiting climate
change. The energy from the sun could play a key role in decarbonizing the global economy
alongside improvements in energy efficiency and imposing costs on greenhouse gas emitters.
"The strength of solar is the incredible variety and flexibility of applications, from small scale
to big scale".
We have proved ... that after our stores of oil and coal are exhausted the human race can
Receive unlimited power from the rays of the sun.
—Frank Shuman, New York Times, July 2, 1916

29 | P a g e
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