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1. Applications of Different Energy sources
2. Flat-plate collectors Flat-plate collectors are in wide use
for domestic household hot-water heating and for space heating. The
basic parts noted are a full-aperture absorber, transparent or
translucent cover sheets, and an insulated box. The absorber is
usually a sheet of high-thermal- conductivity metal with tubes or
ducts either integral or attached. Its surface is painted or coated
to maximize radiant energy absorption and in some cases to minimize
radiant emission. The cover sheets, called glazing, let sunlight
pass through to the absorber but insulate the space above the
absorber to prohibit cool air from flowing into this space.
3. Flat-plate collectors The insulated box provides structure
and sealing and reduces heat loss from the back or sides of the
collector. Flat-plate collectors will absorb energy coming from all
directions above the absorber. Because of this characteristic,
flat-plate collectors do not need to track the sun.
4. Parabolic trough collectors Parabolic trough collectors use
trough-shaped reflectors that concentrate sunlight on a receiver
tube running along the reflector's focal line, achieving much
higher temperatures than flat- plate collectors. These systems
usually include a mechanical control system that keeps the trough
reflector pointed at the sun throughout the day. Parabolic-trough
concentrating systems can provide hot water and steam, and are
generally used in commercial and industrial applications.
5. Parabolic trough collectors Compound parabolic concentrating
collectors (CPCCs) use mirrored surfaces to concentrate the sun's
energy on an absorber called a receiver, similar to parabolic
trough collectors. CPCCs achieve moderate concentration and
moderately high temperatures but, unlike parabolic trough
collectors, they can collect both direct and diffuse sunlight and
don't require an automated sun-tracking system. CPCCs are being
investigated for use in commercial applications where higher
temperatures are required.
6. Parabolic dish collectors Parabolic dish concentrating
systems use parabolic dish shaped mirrors to focus incoming solar
radiation onto a receiver that is positioned at the focal point of
the dish. Fluid in the receiver is heated to high temperatures,
around 750oC. This fluid is then used to generate electricity in a
small Stirling or Brayton cycle engine, which is attached to the
receiver. Parabolic dish systems are the most efficient of all
solar technologies, at approximately 25% efficient, compared to
around 20% for other solar thermal technologies.
7. Parabolic dish collectors
8. Solar Cell / Photovoltaic Cell A slab (or wafer) of pure
silicon is used to make a PV cell. The top of the slab is very
thinly diffused with an n dopant such as phosphorous. On the base
of the slab a small amount of a p dopant, typically boron, is
diffused. The phosphorous gives the wafer of silicon an excess of
free electrons; it has a negative character. This is called the
n-type silicon (n = negative). The n-type silicon is not chargedit
has an equal number of protons and electronsbut some of the
electrons are not held tightly to the atoms. They are free to move
to different locations within the layer. The boron gives the base
of the silicon a positive character, because it has a tendency to
attract electrons. The base of the silicon is called p-type silicon
(p = positive). The p-type silicon has an equal number of protons
and electrons; it has a positive character but not a positive
charge.
9. Solar Cell / Photovoltaic Cell Where the n-type silicon and
p-type silicon meet, free electrons from the n-layer flow into the
p-layer for a split second, then form a barrier to prevent more
electrons from moving between the two sides. This point of contact
and barrier is called the p-n junction. If the PV cell is placed in
the sun, photons of light strike the electrons in the p-n junction
and energize them, knocking them free of their atoms.
10. Solar Cell / Photovoltaic Cell A conducting wire connects
the p-type silicon to an electrical load, such as a light or
battery, and then back to the n-type silicon, forming a complete
circuit. As the free electrons are pushed into the n-type silicon
they repel each other because they are of like charge. The wire
provides a path for the electrons to move away from each other.
This flow of electrons is an electric current that travels through
the circuit from the n-type to the p-type silicon.
11. Hydropower Hydroelectric power comes from water at work,
water in motion. To generate electricity, water must be in motion.
This is kinetic (moving) energy. When flowing water turns blades in
a turbine, the form is changed to mechanical (machine) energy. The
turbine turns the generator rotor which then converts this
mechanical energy into another energy form -- electricity. Since
water is the initial source of energy, it is called hydroelectric
power or hydropower for short.
12. Hydropower Dams store water for later release for such
purposes as irrigation, domestic and industrial use, and power
generation. The reservoir acts much like a battery, storing water
to be released as needed to generate power. The dam creates a head
or height from which water flows. A pipe (penstock) carries the
water from the reservoir to the turbine. The fast-moving water
pushes the turbine blades, something like a pinwheel in the wind.
The waters force on the turbine blades turns the rotor, the moving
part of the electric generator. When coils of wire on the rotor
sweep past the generators stationary coil (stator), electricity is
produced.
13. Flat Plate Solar Collectors
14. Concentrating Solar Collectors
15. Dish Collectors
16. Solar Cell
17. Natural Circulation Water Heating System A simple, small
capacity, natural circulation system, suitable for domestic
purposes is shown in figure. Two main components; the liquid flat-
plate collector and the storage tank, located above the level of
the collector. As the water is heated by the solar energy, it flows
automatically to the top of the water and it is replaced by cold
water from the bottom of the tank.
18. Natural Circulation Water Heating System Hot water for use
is withdrawn from the top of the tank. Whenever this is done, cold
water automatically enters at the bottom. Most of the systems have
capacities of 100 or 200 litres per day, and use one or two flat
plate collectors having a surface area of 2m2 each. The temperature
of the hot water delivered ranges from 50 to 70OC.
19. Power generation using flat plate collectors Solar thermal
power cycle can be classified as low (about 100OC), medium (about
maximum up to 400OC) and high (above 400OC) temperature cycle. Low
temperature systems use flat-plate collectors or solar ponds for
collecting solar energy. The energy of the sun is collected by
water flowing through the array of flat-plate collectors. The hot
water at temperatures close to 100OC is stored in a well-insulated
thermal storage tank. From here, it flows through a vapor generator
through which the working fluid is also passed. The working fluid
(low boiling point temperature) vapor at about 90OC at few
atmospheric pressure leaves the vapor generator and flowing through
a prime mover (turbine), a condenser and a liquid pump.
20. Power generation using flat plate collectors A power
generator is coupled with turbine and electric power is produced by
generator. Up to 50KW power can be produced by this system .
21. Photovoltaic System Application The system is an integrated
assembly of modules and other components designed to provide a
particular services, either alone or in conjunction of backup
supply. A such simplest system for street lighting is shown in
figure. The modules or array supplying a dc loads which can be
stored in the battery. During at night, the dc power is supplied by
controller through Inverter (which converts dc to ac voltage) to
the light (load).
22. Nuclear Power Plant The main components of a nuclear power
plant are nuclear reactor, heat exchanger (steam generator),
turbine, electric generator and condenser. The heat liberation in
the reactor due to the nuclear fission of the fuel is taken up by
the coolant circulating through the reactor core. Hot coolant
leaves the reactor at top and then flows through the tubes of steam
generator (boiler) and passes on its heat to the feed water. The
steam produced is passed through the turbine and after work has
been done by the expansion of steam in the turbine steam leaves the
turbine and flows to the condenser. Pumps are provided to maintain
the flow of coolant, condensate and feed water. The electric
generator connected with the turbine produces the electric
power.