The document provides an overview of solar energy, explaining its origin from the sun and how it can be converted into electricity through technologies like photovoltaics and concentrated solar power. It details various methods of harnessing solar energy, including solar thermal technologies and the components of solar cells that facilitate the conversion process. Additionally, it discusses the structure and functioning of photovoltaic cells, highlighting their role in generating electricity from sunlight.

1. CHAPTER FIVE
SOLAR ENERGY
BY: MESFIN MEGRA1/28/2018 1

2. WHAT IS SOLAR ENERGY?
❖Originates with the thermo-nuclear fusion reactions
occurring in the sun.
❖Represents the entire electromagnetic radiation.
❖This energy consists of radiant light and heat energy
from the sun.
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3. CONT.….
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4. WHAT IS SOLAR POWER?
❖Solar power is the conversion of sunlight into electricity
either directly by using photovoltaics or concentrated
solar power.
❖A solar cell, or photovoltaic cell (PV), is a device that
converts light into electric current using the photoelectric
effect.
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5. SOLAR RADIATION
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6. CONT.….
❖ Solar Insolation is the amount of solar radiation
reaching earth. also called incident solar radiation.
❖ Maximum value is 1000 KW/M2.
❖ Components of solar radiation:
Direct radiation
Diffuse radiation
Reflect radiation1/28/2018 6

7. CONT.….
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8. CONT.….
❖ The surface receives about 47% of the total solar
energy that reaches the earth. Only this amount is
usable
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9. HOW SOLAR ENERGY IS USED?
❖Solar energy can be used for different purposes:
❖Solar thermal
❖Solar heating
❖Water heater
❖Solar cocking
❖Photovoltaic cells
❖Electricity generation using solar concentrator1/28/2018 9

10. SOLAR THERMAL ENERGY
❖Solar thermal technologies involve harvesting energy from
the sun for heating water or producing electric power.
❖Solar collectors are used for this purpose:
❖Flat plate collector
❖Evacuated tube collector
❖Integral collector –storage system
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11. FLAT PLATE COLLECTORS
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12. EVACUATED TUBE COLLECTORS
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13. INTEGRAL COLLECTOR
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14. ELECTRICITY FROM SOLAR ENERGY
❖Solar power is described as the conversion of sunlight
into electricity.
❖Sunlight can be changed to electricity with the use of:
❖Directly using photovoltaic cell (PV cells)
❖Indirectly by concentrated solar power (CSPs)
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15. CONCENTRATED SOLAR POWERS
❖Concentrating solar power system is made up of lenses,
mirrors, and tracking systems focusing a large amount of
sunlight into a smaller beam.
❖The concentrated light heat up a working fluid and is
then used as the heat source for power generation or
energy storage.
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16. CONCENTRATED SOLAR POWERS
❖The sunlight from the sun will heat the fluid and produce
steam.
❖The steam drives a turbine and generates power in the
same way as conventional power plants.
❖The most developed methods for CSP are solar trough,
parabolic dish, and solar power tower.
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17. SOLAR POWER TOWER
❖General idea is to collect the light from many reflectors
spread over a large area at one central point to achieve
high temperature.
❖Capital cost is greater than coal fired power plant,
despite the no cost for fuel, ash disposal, and stack
emissions.
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18. SOLAR POWER TOWER
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19. PARABOLIC DISHES AND TROUGHS
❖Focus sunlight on a smaller receiver for each device; the
heated liquid drives a steam engine to generate electricity.
❖Because they work best under direct sunlight, parabolic
dishes and troughs must be steered throughout the day in
the direction of the sun.
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20. PARABOLIC DISHES AND TROUGHS
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23. SOLAR CELLS AND PHOTOVOLTAICS
❖Photovoltaic cells are capable of directly converting
sunlight into electricity.
❖A simple wafer of silicon with wires attached to the
layers. current is produced based on types of silicon (n-
and p-types) used for the layers. each cell=0.5 volts.
❖Battery needed as storage.
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24. HOW DOES A CELL BECOME A MODULE?
❖A solar cell is the basic building block of a PV system.
❖A typical cell produces .5 to 1V of electricity.
❖Solar cells are combined together to become modules
or if large enough, known as an array.
❖A structure to point the modules towards the sun is
necessary, as well as electricity converters, which convert
DC power to AC.1/28/2018 24

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26. THE PHOTOELECTRIC EFFECT
❖The photoelectric effect relies on the principle that
whenever light strikes the surface of certain metals
electrons are released.
❖In the p-n junction the n-type wafer treated with
phosphorus has extra electrons which flow into the holes
in the p-type layer that has been treated with boron.
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28. STRUCTURE OF A SOLAR CELL
❖A typical solar cell is a multi-layered unit consisting of a:
❖Cover - a clear glass or plastic layer that provides outer
protection from the elements. transparent adhesive - holds
the glass to the rest of the solar cell.
❖Anti-reflective coating - this substance is designed to
prevent the light that strikes the cell from bouncing off so
that the maximum energy is absorbed into the cell.
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29. CONT.….
❖Front contact - transmits the electric current.
❖n-type semiconductor layer - this is a thin layer of
silicon which has been mixed (process called doping)
with phosphorous.
❖p-type semiconductor layer - this is a thin layer of
silicon which has been mixed or doped with boron.
❖Back contact - transmits the electric current.1/28/2018 29

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