ECEg-4242
ENERGY CONVERSION AND RURAL
ELECTRIFICATION
CHAPTER FIVE
SOLAR POWER STATION
THE SUN
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The Sun does emit X-rays, ultraviolet, visible light , infrared , and even
Radio waves. When ultraviolet radiation is not absorbed by the atmosphere
or other protective coating, it can cause damage to the skin known as
sunburn or trigger an adaptive change in human skin pigmentation.
The sunlight that reaches the ground consists of nearly 50% visible light,
45% infrared radiation, and smaller amounts of ultraviolet light and other
forms of electromagnetic radiation.
This radiation can be converted either into: thermal energy or into electrical
energy.
WHAT IS SOLAR ENERGY?
Solar energy is the energy received by the earth from the sun. This energy is in the
form of solar radiation, which makes the production of solar electricity possible.
World Energy Conservation predicted estimation about the rate of utilization of
energy resources shows that the coal deposits will deplete within the next 200 to
300 years and petroleum deposits will deplete in next few decades.
The most advantage using Solar Energy is that this is distributed over a wide
geographical area, ensuring that developing regions such as Ethiopia have access
to electricity generation at a stable cost for the long-term future.
The huge consumption of fossil fuels has caused visible damage to
the environment in various forms.
SOLAR THERMAL SYSTEM
INTRODUCTION
Solar thermal systems have been around for many years to provide hot
water for domestic, commercial, and industrial use.
Solar irradiation heats a collector and transfer fluid, which transfers
thermal energy to storage or direct use.
This is achieved by solar collectors
The collector may be flat-plate, evacuated tube, parabolic trough, or
concentrator with reflecting mirrors (heliostats).
SOLAR COLLECTORS
Solar collector is a mechanical device which captures the radiant solar energy
and converts it to useful thermal energy
solar collectors are categorized into two main types:
a) stationary collectors and b) sun tracking collectors,
Stationary collectors are fixed in their position and do not track the sun.
Three types of collectors are explained in this category:
Flat plate collector (FPC)
Stationary compound parabolic collector (CPC)
Evacuated tube collector (ETC)
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Sun tracking collectors as the name of these types, trace the sun
during the day to collect more energy compared to stationary type.
Four main types of sun tracking collectors would be described.
Parabolic through collector
Linear Fresnel reflector
Parabolic dish reflector
Heliostat field collector
FLAT-PLATE COLLECTORS
Its operation is based on radiation passing a transparent layer and then set on an
absorber layer that absorbs the sun energy as heat energy.
The absorbed heat is then transferred to a kind of medium fluid that could be
water, water plus antifreeze additive, or air in the tubes to increase its temperature
for direct thermal use.
The underside of the absorber plate and inside of the housing are well insulated to
reduce conduction losses..
Most widely used kind of collectors in the world for domestic solar water heating
and solar space heating applications
Used typically for temperature requirements up to 75 ºC
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Figure of An example of flat plate collector (FPC)
It must be facing south in the northern
Hemisphere and north in the southern.
The optimum tilt angle of the
collector is depended on the latitude of the
location with angle variations
of 10–15 degrees
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COMPOUND PARABOLIC COLLECTORS
These kind of collectors have the ability to absorb virtually all the light
emitted to the mouth of them.
These collectors are able to accept a large proportion of diffuse radiation
incident on their apertures and concentrate it without tracking the sun [3].
Should be fixed in a specific angle called acceptance angle based on its
position,.
For stationary CPC collectors mounted in this mode the minimum
acceptance angle is equal to 47 degrees.
This angle covers the declination of the sun from summer to winter
solstices.
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diagram of a compound parabolic collector (CPC)
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diagram of a compound parabolic collector (CPC)
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diagram of a compound parabolic collector (CPC)
EVACUATED TUBE COLLECTORS (ETC)
These solar collectors consist of a heat pipe inside a vacuum sealed tube
The vacuum envelope reduces convection and conduction losses, so the
collectors can operate to higher temperatures than flat plate collectors.
The pipe, which is a sealed copper pipe, is then attached to a black copper fin
that fills the tube (absorber plate) protruding from the top of each tube is a
metal tip attached to the sealed pipe (condenser).
The heat pipe contains a small amount of fluid such as methanol that undergoes
an evaporating-condensing cycle.
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PARABOLIC THROUGH COLLECTORS
Parabolic through can effectively produce heat up to temperatures about 400 C.
This collector is contained of a parabolic mirror and a metal black tube covered
with a glass tube to reduce heat losses.
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• . The collector can be orientated in an east–west direction, tracking the sun
from north to south, or orientated in a north–south direction and tracking the
sun from east to west. The collectors in south-north direction during the year
collect more energy but the collectors in west-east direction are better just in
summers.
CONT
The biggest application of this type of system is the Southern California power
plants, known as solar electric generating systems (SEGS) which have a total
installed capacity of 354 MW
LINEAR FRESNEL REFLECTOR
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The greatest advantage of this type of system is that it utilizes flat or
elastically curved reflectors which are cheaper compared to parabolic
glass reflectors. Additionally, this type is mounted close to the ground,
causing minimizing the structural requirements. Linear Fresnel collector
is based on many mirrors focusing gleams of light to the receiver tube
which is surrounded by secondary reflector. There are different designs
of this kind of collector. In the basic design there is just one absorber
tube, but there are new designs which hold on two or more tubes
PARABOLIC DISH REFLECTOR
Parabolic dish reflector, known as distributed-receiver system, tracks the
sun in two axes during the day and focus the sunlight irradiated to the dish
to a focal point.
Figure 7 is illustrating a dish collector. The dish structure must follow the
sun to reflect the beam to the thermal receiver. The receiver absorbs the
radiant solar energy, converting it into thermal energy in a circulating fluid.
The thermal energy can then either be converted into electricity using an
engine-generator coupled directly to the receiver, or it can be transported
through pipes to a central power-conversion system.
CONT..
These collectors can exceed the temperature about 1500 degrees
centigrade and they are the most efficient of all collector systems.
They typically have a concentration ratio (the averaged radiant flux
over the dish area, divided by the insolation incident on the receiver
aperture) in the range of 600–2000, and thus are
highly efficient at thermal-energy absorption and power
conversion systems.
CONT..
HELIOSTAT FIELD COLLECTOR
Heliostats are slightly concave tracking mirrors locating around a
tower which there is a receiver on its head. Figure 8 is showing a
schematic view of heliostat field collector .
CONT..
In this plant large amounts of solar energy would be concentrated into
the cavity of a receiver to be sent to a steam-generator to produce steam
at high temperature and pressure. The heat energy absorbed by the
receiver is transferred to a circulating fluid that can be stored and later
used to produce power during the night.
The concentration ratios of this type of collector is between 300 and
1500 .
These kind of plants use the area from 50 to 150 𝑚2 and sometimes they
utilize thermal storage systems. In some cases hybrid plants are made
which use both solar and fossil energy in the thermal storage system.
Solar Photovoltaic
Systems
INTRODUCTION
A common way for property owners to take advantage of solar energy is with a photovoltaic
(PV) solar system. With a solar PV system, solar panels convert sunlight right into
electricity that can be used immediately, stored in a solar battery.
Solar panels convert solar energy into usable electricity through a process known as the
photovoltaic effect.
Incoming sunlight strikes a semiconductor material (typically silicon) and knocks electrons
loose, setting them in motion and generating an electric current that can be captured
with wiring. This current is known as direct current (DC) electricity and must be
converted to alternating current (AC) electricity using a solar inverter.
This conversion is necessary because the electric grid operates using AC electricity, as
do most household electric appliances.
BASIC PRINCIPLES OF PHOTOVOLTAIC
EQUIVALENT CIRCUIT OF SINGLE SOLAR CELL
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IV CHARACTERISTICS OF A SOLAR CELL
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I-V AND P-V CURVE CHARACTERISTICS OF A SOLAR CELL
EXAMPLE
SOLUTION
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TERMINOLOGIES OF A SOLAR CELL
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EXAMPLES
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TYPES OF SOLAR PANELS
AMORPHOUS
SERIES AND PARALLEL CONNECTIONS OF PANELS
Components of solar panel
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Solar Charge Controller : regulates the voltage and current coming from the PV
panels going to battery and prevents battery overcharging and extends the battery
life.
Inverter: converts DC output of PV panels into a clean AC current for the inputs
of AC appliances
Battery: stores energy for supplying to electrical appliances during night time
and when there is a demand.
Load: is electrical appliances that connected to solar PV system such as lights,
radio, TV, computer, refrigerator, etc
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The primary functions of a storage battery in a PV system are:
a. Energy Storage Capacity and Autonomy
b. Voltage and Current Stabilization
c. Supply Surge Currents
The number of days the battery storage capacity is available to
operate the electrical loads directly from the battery, without any energy
input from the PV array is called days of “autonomy” in a standalone
PV system.
SIZE THE BATTERY OR BATTERY BANK
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BATTERY BANK CONNECTION
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SOLAR CHARGE CONTROLLER
SOLAR CHARGE CONTROLLER SIZING
DC-DC CONVERTERS
DC-AC INVERTERS
CONNECTING THE INVERTER
OFF-GRID INVERTER SPECIFICATIONS
DESIGN OF SOLAR HOME SYSTEM (SHS) AS PER REQUIREMENT
OF CUSTOMER
STEPS IN SYSTEM SIZING PROCESS
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STEP 2: SELECTION OF SOLAR PV MODULE
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STEP 3: SELECTION OF BATTERY SIZING
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STEP 4: CHARGE CONTROLLER SIZING
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INVERTER SIZING
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GENERALLY
STEP 6:WIRE SIZING
II. SELECTION OF THE WIRE SIZE FOR SOLAR HOME SYSTEM
WIRE JOINING THE SOLAR MODULE AND CHARGE CONTROLLER ‘A’
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INSTALLATION OF SOLAR MODULE
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ARRAY INSTALLATION AND WIRING
PARALLEL CONNECTION OF SOLAR PANELS
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