RES PPT.pdf

RENEWABLE
ENERGY
SYSTEMS
IV B.Tech I Semester
(R19)
Course Teacher:
Dr. MAHABOOB SHAREEF SYED

UNIT – 1: FUNDAMENTALS OF ENERGY
SYSTEMS AND SOLAR ENERGY
UNIT – 2 : SOLAR PHOTOVOLTAIC SYSTEMS
UNIT – 3 : WIND ENERGY
UNIT – 4 : HYDRO AND TIDAL POWER SYSTEMS
UNIT – 5 : BIOMASS, FUEL CELLS AND
GEOTHERMAL SYSTEMS
Syllabus

Students should able to
Students Should be able to
 Analyze solar radiation data, extra terrestrial
radiation, and radiation on earth’s surface.
 Design solar thermal collectors, solar thermal
plants.
 Design solar photo voltaic systems
 Develop maximum power point techniques in solar
PV and wind energy systems.
 Explain wind energy conversion systems, wind
generators, power generation.
 Explain basic principle and working of hydro,
tidal, biomass, fuel cell and geothermal systems.
Course Outcomes

Fundamentals of Energy Systems and Solar
energy:
 Energy conservation principle
 Energy scenario (world and India)
 Various forms of renewable energy
 Solar radiation
 Outside earth’s atmosphere – Earth surface
 Radiation on tilted surfaces -Numerical problems.
Unit - 1

 The law of conservation of energy states that the
total energy of an isolated system remains constant.
 This law means that energy can neither be created
nor destroyed; rather, it can only be transformed or
transferred from one form to another.
 The energies are P.E, K.E, heat, sound, Chemical
etc.
 Relativity showed that mass is related to energy and
vice versa by E = mc2
Energy conservation
Principle

 Energy is one of the major inputs for the economic
development of any country.
Energy can be classified into several types based on the
following criteria:
 Primary and Secondary energy
 Commercial and Non commercial energy
 Renewable and Non-Renewable energy
 Conventional and Non-conventional energy
Energy Scenario
Introduction

1. Available free of cost
2. Cause no or very little pollution
3. Environment-friendly
4. Inexhaustible
5. Have low gestation period
6. Do not deplete natural resources
7. Can sustain energy supply for many generations.
Advantages of Renewable
Energy Sources

1. Available in dilute form in nature
2. Cost of harnessing energy is very high
3. Availability is uncertain
4. Difficulty in transporting such resources
Disadvantages of
Renewable Energy Sources

Types of Non Conventional
Energy Sources
 Tidal Energy, wave Energy
 Small Scale Hydro electric
(Mini & Micro)
 Chemical energy sources
 Hydrogen energy
 Magneto hydro dynamics
 Solar Energy (energy from sun)
 Wind energy
 Energy from Bio Mass
 Geothermal Energy
 Energy from Oceans
 OTEC

• The non-conventional sources of energy in the country are available
in abundance and their potential is need to be utilized.
• Particularly in a country like India where the basic economy of the
majority of the people about 73 percent is based on agriculture and
the demand of energy of rural population is less as compared to
urban settlements.
• Our coastal areas have a large potential of wind and solar energy
• “Bio-gas” is another source of energy which also has a big potential
as we have a bulk of live stock.
Potential of NCES

• Renewable energy account for 34.6% of the total installed power
capacity.
• Large hydro installed capacity was 45.399 GW, contributing to 13%
of the total power capacity.
• The remaining renewable energy sources accounted for 22% of the
total installed power capacity (77.641 GW).
• Wind power capacity was 36,625 MW, making India the fourth wind
power producer in the world.
• The government target of installing 20 GW of solar power by 2022 was
achieved four years ahead of schedule in January 2018, through both
solar parks as well as roof-top solar panels.
• India has set a new target of achieving 100 GW of solar power by 2022.
Energy Scenario in
INDIA

 Four of the top seven largest solar parks worldwide are in India including the second
largest solar park in the world at Kurnool, Andhra Pradesh, with a capacity of 1000
MW.
 The world's largest solar power plant, Bhadla Solar Park is being constructed in
Rajasthan with a capacity of 2255 MW.
 Biomass power from biomass combustion, biomass gasification reached 9.1 GW
installed capacity.
 India was the first country in the world to set up a ministry for NCSE in the early
1980s.
 Solar Energy Corporation of India for the development of solar energy.
 In the 2027 forecasts, India aims to have a renewable energy installed capacity of 275
GW, in addition to 72 GW of hydro-energy, 15 GW of nuclear energy and nearly
100 GW from “other zero emission” sources.
Energy Scenario in
INDIA

Students should able to Global Primary
Energy Reserves
Coal: The proven global coal reserve was estimated to be 9,84,453 million tonnes
by end of 2003. The USA had the largest share of the global reserve (25.4%)
followed by Russia (15.9%), China (11.6%). India was 4th in the list with 8.6%.
Oil: The global proven oil reserve was estimated to be 1147 billion barrels by the
end of 2003. Saudi Arabia had the largest share of the reserve with almost 23%.
Gas: The global proven gas reserve was estimated to be 176 trillion cubic metres
by the end of 2003. The Russian Federation had the largest share of the reserve
with almost 27%.
World oil and gas reserves are
estimated at just 45 years and 65
years respectively.
Coal is likely to last a little over
200 years Global Primary Energy
Consumption.
The global primary energy
consumption at the end of 2003
was equivalent to 9741 million
tonnes of oil equivalent.

Students should able to Global Primary
Energy Reserves
 Although 80 percent of the world's population lies in the developing countries,
their energy consumption amounts to only 40 percent of the world total energy
consumption.
 The high standards of living in the developed countries are attributable to high
energy consumption levels.
 Also, the rapid population growth in the developing countries has kept the per
capita energy consumption low compared with that of highly industrialized
developed countries.
 The world average energy consumption per person is equivalent to 2.2 tonnes
of coal.
 In industrialized countries, people use four to five times more than the world
average, and nine times more than the average for the developing countries.
An American uses 32 times more commercial energy than an Indian.

Students should able to Various forms of
Renewable Energy
Some nonconventional, renewable and inexpensive energy
sources are described below:
1. Solar energy
2. Wind energy
3. Tidal energy
4. Geothermal energy
5. Bio-mass based energy
6. Biogas
7. Energy from urban waste

• Solar energy is a Radiant energy emitted by the sun.
• Solar power is energy from the sun. Without it, there will be no life.
• Solar energy is considered as a serious source of energy for many years
because of the vast amounts of energy that is made freely available, if
harnessed by modern technology.
• Solar energy, radiant light and heat from the sun, has been harnessed by
humans since ancient times using a range of ever-evolving technologies.
• Solar energy technologies include
Solar heating, Solar photovoltaic, Solar thermal electricity
Solar architecture and artificial photosynthesis.
What is Solar Energy ?

• Solar technologies are broadly characterized as either Passive solar or
Active solar depending on the way they capture, convert and
distribute solar energy.
• Active solar techniques include the use of photovoltaic panels and
solar thermal collectors to harness the energy.
• Passive solar techniques include orienting a building to the Sun,
selecting materials with favorable thermal mass or light dispersing
properties, and designing spaces that naturally circulate air.
• The Sun is a sphere of hot gases with diameter 1.39*109 m and an avg
distance of 1.49*1011 m from the earth. The reaction at sun is:
• 4 1H1  2He4 + 26.7 Mev. The temperature at the sun is 5760 oK.
What is Solar Energy ?

Solar irradiance (SI) :
This is the power per unit area (W/m2), received from the Sun in the form of
electromagnetic radiation.
In order to report the radiant energy emitted into the surrounding environment
(J/m2), Solar irradiance is integrated over a given time period which is called
solar irradiation, solar exposure, solar insolation, or insolation.
Irradiance may be measured in space or at the Earth's surface after
atmospheric absorption and scattering.
This is a function of Distance from the Sun and the solar cycle– In Space.
Tilt of the measuring surface, the height of the sun above the horizon, and
atmospheric conditions - On earth’s surface.
Solar Radiation on
Earth’s Surface

The region above the atmosphere is called as extraterrestrial region and
the radiation which reaches to this is known as Extra terrestrial radiation
which can be calculated by:
ISC is solar constant which is solar radiation received per unit area = 1367 w/m3.
The region around the earth’s surface is called terrestrial region and the
radiation which reaches to this is known as terrestrial radiation.
Always extra terrestrial radiation is more than the terrestrial radiation.
Solar Radiation on
Earth’s Surface

The above effects have several impacts on the solar radiation received at the
Earth's surface.
These changes include variations in the overall power received, the spectral
content of the light and the angle from which light is incident on a surface.
In addition, a key change is that the variability of the solar radiation at a
particular location increases dramatically.
The variability is due to both local effects such as clouds and seasonal
variations, as well as other effects such as the length of the day at a
particular latitude.
Desert regions tend to have lower variations due to local atmospheric
phenomena such as clouds.
Equatorial regions have low variability between seasons.
Solar Radiation on
Earth’s Surface

The study and measurement of solar irradiance have several important
applications
 Prediction of energy generation from solar power plants.
 The heating and cooling loads of buildings.
 Climate modeling.
 Weather forecasting.
Solar Radiation on
Earth’s Surface

Students should able to Solar Radiation
Spectrum
Electro Magnetic Spectrum
 Solar energy is an electromagnetic radiation from
the Sun, what we’ve always known as light and
heat.
 It’s composition is: 6 – 7% ultraviolet light,
around 42% visible light and 51% near infra-red.
 99.9% of the sun’s output of energy occurs
between 250 and 2500 nanometers.
Solar radiation radiates from sun with different wave
length.
λ < 0.38 micro meters - UV radiation
0.38 < λ < 0.78 micro meters - Visible radiation
λ > 0.78 micro meters - Infrared radiation

Students should able to Direct & Diffuse
Radiation
The total solar radiation striking a collector has two components:
 Direct beam radiation and Diffuse radiation.
 Additionally, radiation reflected by the surface in front of a collector
contributes to the solar radiation received. But unless the collector is
tilted at a steep angle from the horizontal and the ground is highly
reflective, this contribution is small.
Direct beam radiation: As the name implies, it comes in a direct line from
the sun.
 For sunny days with clear skies, most of the solar radiation is direct
beam radiation.
 On overcast days, the sun is obscured by the clouds and the direct beam
radiation is zero.

Radiation
Diffuse radiation:
 It is scattered out of the direct beam by molecules, aerosols, and clouds.
 Because, it comes from all regions of the sky, it is also referred to as
Sky radiation.
 The portion of total solar radiation that is diffuse is about 10% to 20%
for clear skies and up to 100% for cloudy skies.

Radiation
The solar radiation that penetrates the earth‟s atmosphere
and reaches the surface differs in both amount and
character from radiation at the top of the atmosphere.
1. Oxygen and ozone absorbs nearly all the ultraviolet
radiation
2. Water vapor and CO2 absorb some of the energy in the
infrared range.
3. Part of the radiation is reflected back into the space,
especially by clouds.
3. Some part of the solar energy radiation is scattered by
droplets in the clouds by atmospheric molecules, and by
dust particles.

Definitions
Sun at Zenith: Position of the sun directly over head.
Air mass (m): It is the path length of radiation through the atmosphere,
considering the vertical path at sea level as unity.
It is the ratio of the path of the sun’s rays through the atmosphere to the
length of path when the sun is at the zenith.
m = 0 ; just above the earth’s atmosphere.
m = 1 ; when the sun is at zenith
m = 2 ; when the Zenith angle is 60o

Definitions

Declination (δ): it is the angle between the sun–earth centre line
and the projection of this line on the equatorial plane. Declinations
north of the equator are positive, and those south are negative.
Declination in degrees for any day of the year, can be defined
approximately by equation:
Definitions

Hour angle (h): The hour angle of a point on the earth’s surface is defined
as the angle through which the earth would turn to bring the meridian of the
point directly under the sun.
 The hour angle of point P as the angle measured on the earth’s equatorial
plane between the projection of OP and the projection of the sun–earth
centre to centre line.
 The hour angle at local solar noon is zero, with each 360/24 or 15° of
longitude equivalent to 1 h, afternoon hours being designated as
positive. Expressed symbolically, the hour angle in degrees can be
obtained from Apparent Solar Time(AST) as follows:
h = (AST-12)15
Definitions

Solar altitude angle(α): The solar altitude angle is the angle
between the sun’s rays and a horizontal plane.
tive.
Definitions
The mathematical expression for the solar altitude angle
depends on local latitude. Values north of the equator
are positive and those south are negative.
Zenith Angle (Ф) : It is complimentary angle of sun's
altitude angle. It is a vertical angle between the sun rays
and a line perpendicular to the horizontal plane through
the point.
Ф = 90o- α

Solar azimuth angle(z): The solar azimuth angle is the angle of the
sun’s rays measured in the horizontal plane from south for the
Northern Hemisphere or north for the Southern Hemisphere.
Angle of latitude: Latitudes measure an angle
up from the equator.
Definitions

Incidence and tilt angles: The solar incidence angle is the angle
between the sun’s rays and the normal on a surface.
For a horizontal plane, the incidence angle and the zenith angle are
the same.
Zs = Surface azimuth angle, the angle between
the normal to the surface from true south
Definitions
L = Local latitude
= Solar declination
= Tilt angle
= Surface azimuth angle
h= hour angle

Owing to the increasing number of solar applications it is
required to measure the solar radiation.
Solar radiation measurement devices:
1. Pyranometer
2. Pyrheliometer
3. Sunshine meter
Measurement of Solar
Radiation

This is used to measure global radiation on horizontal or
inclined planes.
Pyranometer
• A Pyranometer is a sensor that converts
the global solar radiation it receives
into an electrical signal that can be
measured. Pyranometers measure a
portion of the solar spectrum.
• A Pyranometer does not respond to
long-wave radiation.
• Pyranometers must also account for the
angle of the solar radiation.
• The most common types of
pyranometers used for measuring global
solar radiation are thermopiles and
silicon photocells.

Pyranometer
• Based on the Seebeck- or thermoelectric effect, a pyranometer
is operated based on the measurement of a temperature
difference between a clear surface and a dark surface.
• The black coating on the thermopile sensor absorbs solar
radiation, while the clear surface reflects it.
• The potential difference created in the thermopile owing to the
temperature gradient between the two surfaces reveals
information about the amount of solar radiation.
• The voltage produced by the thermopile can also be measured
using a potentiometer.

Pyrheliometer
• A pyrheliometer is a device that measures solar irradiance coming
directly from the sun.
• Traditionally pyrheliometers were mainly used for climatological
research and weather monitoring purposes, however recent worldwide
interest in solar energy has also led to an increased interest in
pyrheliometers.
• Pyrheliometers measure ‘direct solar radiation’ E:
• The amount of solar energy per unit area per unit time incident on a
plane normal to the position of the sun in the sky, coming directly
from the sun itself. This is also called ‘direct normal irradiance’,
often abbreviated to DNI.

Pyrheliometer
• A pyrheliometer needs to be mounted on a solar tracker.
• This direct radiation E, together with diffuse radiation Ed,
gives the total available amount of solar energy on the
Earth’s surface, the global irradiance Eg↓.
• Eg↓=E⋅cos(θ)+Ed
• where θ is the angle between the surface normal and the
position of the sun in the sky.
• To limit the measurement to the radiation coming only
directly from the sun, it is necessary to limit the field of
view of the instrument.

Pyrheliometer
• Working: Pyrheliometers are irradiance sensors that incorporate thermopiles (sensors based
on the Seebeck- or thermoelectric effect.).
• The main components of a pyrheliometer are a quartz window, a black absorber, a
thermopile, the pyrheliometer tube which defines the field of view and in some cases
additional electronics. Sights are included to enable the instrument to be pointed correctly.
The window on a pyrheliometer acts as a filter that transmits solar radiation with wavelengths
from roughly 200 nm to about 4000 nm but blocks thermal radiation with wavelengths longer
than 4 µm.
• The transmission τ of solar radiation through a window is ideally close to 100 %, but is in
practice closer to 95%. The window also serves to protect the black absorber and the
thermopile from the elements (rain, snow, etc.).

Pyrheliometer
The filtered radiation is absorbed by the black surface on the pyrheliometer and
converted into heat. If the transmission through the window is τ, the area of the black
surface is A and the absorption coefficient of the black surface is α then the heat
absorption can be calculated as follows:
Pabsorption=α⋅τ⋅A⋅ E
This creates a temperature gradient from the black surface through the thermopile to the
pyrheliometer body which acts as a heatsink. The temperature difference is given by:
ΔT=Rthermal⋅Pabsorption
Where Rthermal is the thermal resistance of the thermopile sensor. This thermal resistance
depends on the specific composition and geometry of the thermopile sensor.

Sunshine meter

 A sunshine recorder is a device that records the amount of
sunshine at a given location or region at any time. The results
provide information about the weather and climate as well as
the temperature of a geographical area.
 This information is useful in meteorology, science, agriculture,
tourism, and other fields. It has also been called a heliograph.
 There are two basic types of sunshine recorders.
One type uses the sun itself as a time-scale for the sunshine readings.
The other type uses some form of clock for the time scale.
Sunshine meter

 This recorder consists essentially of a glass sphere of 96 mm
diameter mounted concentrically in a section of a spherical metal
bowl, the diameter of which is such that the sun`s rays are
focused sharply on a card held in the grooves, in the bowl.
Sunshine meter
• Three overlapping pairs of grooves are
provided in the bowl to taken up cards
suitable for the different seasons of the
year.
• The sphere is made of uniform and well
annealed colorless glass and is
carefully ground and polished with
great precision.

Students should able to Environmental impact
of solar power in India.
• Even though solar power plants don't emit harmful gases, or CO2
which results in greenhouse effect, it still causes damage to the
environment.
• The potential environmental impacts associated with solar power can
be classified according to numerous categories, some of which are land
use impacts, ecological impacts, impacts to water, air and soil, and
other impacts such as socioeconomic ones can vary greatly depending
on the technology, which includes two broad categories: (i)
Photovoltaic (PV) solar cells or, (ii) Concentrating solar thermal plants
(CSP).

• Impacts on land use: Depending on their location, larger utility-scale solar facilities can
raise concerns about land degradation and habitat loss.
• Total land area requirements vary depending on the technology, the topography of the
site, and the intensity of the solar resource. The land used for installing solar power
plants cannot be used for any other purpose, due to this, the amount of usable lands will
reduce dramatically.
• Impacts on soil, air and water resources: The construction of solar facilities on vast areas
of land imposes clearing and grading, resulting in soil compaction, alteration of drainage
channels and increased erosion. Central tower systems require consuming water for
cooling, which is a concern in arid settings, as an increase in water demand may strain
available water resources as well as chemical spills from the facilities which may result
in the contamination of groundwater or the ground surface. Concentrating solar thermal
plants (CSP), like all thermal electric plants, require water for cooling. Water use
depends on the plant design, plant location, and the type of cooling system

• Hazardous materials: The PV cell manufacturing process includes a
number of hazardous materials, most of which are used to clean and
purify the semiconductor surface. These chemicals, similar to those
used in the general semiconductor industry, include hydrochloric acid,
sulfur acid, nitric acid, hydrogen fluoride, trichloroethane, and acetone.

Students should able to UNIT – 2
SOLAR PHOTOVOLTAIC
SYSTEMS
• Solar photovoltaic cell, module, array – construction
• Efficiency of solar cells
• Developing technologies
• Cell I-V characteristics
• Equivalent circuit of solar cell – Series resistance – Shunt resistance
• Applications and systems – Balance of system components
• System design: storage sizing
• PV system sizing
• Maximum power point techniques:
Perturb and observe (P&O) technique
Hill climbing technique.

Students should able to Introduction to Solar
Photovoltaic System
For hundreds of years, people have wanted to harness the
sun’s power for weapons, heating, and many other uses to
make their lives more comfortable.
Actually, the first solar water heating collector appears to
have been built in the 18th Century by a Swiss scientist who
constructed a simple wooden box with a glass top and a black
base. It trapped solar energy, and the collector reached a
temperature of 190 degrees Fahrenheit.
Solar energy will certainly play an important role in the future
energy needs of our planet, but it’s also here today and ready
for hundreds of uses in homes, businesses, and industry.

Students should able to Introduction to Solar
Photovoltaic System
• The sun is an inexhaustible power supply.
• It brings enough energy to our planet every single day to
meet a full year’s worth of energy for everyone on Earth.
• Millions of people around the world use solar energy
because it is the only available, reliable power source for
many of their basic needs such as lighting and water
pumping.
Global warming, acid rain and toxic air emissions, has in
recent years turned a great deal of attention to environmentally
friendly solar energy systems

Students should able to Advantages of PV
System
• It converts solar energy directly into electrical energy
without going through the thermal / mechanical
conversion.
• This system has no moving parts.
• This power is more reliable, modular, durable and
maintenance free.
• This is compatible with almost all environments and have
the life span of more than 20 years.
• This system can be located at the place of use, therefore no
need of transmission and distribution network.

Students should able to Components of PV
Systems
• Photo Voltaic cell
• Inverter
• Battery
• The basic conversion device is solar photo voltaic cell /
Solar cell.
• It is an electrical current source driven by solar radiation.
• A solar cell is the most expensive components in a solar PV
system.
• It can produce 1-2 kWH per Sq.m per day in an ordinary
sun shine.

Working of PV Cell

Working of PV Cell
• Solar panels convert the sunlight's photon
energy into electricity.
• Sunlight is composed of photons, or particles of
radiant solar energy.
• These photons contain various amounts of
energy depending on the wavelength of the solar
spectrum.
• The photons strike a solar cell, some are
absorbed while others are reflected.
• When the material absorbs sufficient photon
energy, electrons within the solar cell material
dislodge from their atoms.

Working of PV Cell
• The electrons migrate to the front surface of the solar cell,
which is manufactured to be more receptive to the free
electrons.
• When many electrons, each carrying a negative charge,
travel toward the front surface of the cell, the resulting
imbalance of charge between the cell's front and back
surfaces creates a voltage potential like the negative and
positive terminals of a battery. When the two surfaces are
connected through an external load, electricity flows.

PV Cell, Module, Array
• Individual solar cells vary in size from about 1 cm to about 10 cm across.
• A cell of this size can only produce 1 or 2 watts, which isn't enough
power for most applications.
• To increase power output, cells are electrically connected into a module.
• Modules are connected to form an array.
• The term "array" refers to the entire generating plant, whether it is made
up of one or several thousand modules.
• Large banks of solar cells maximise the amount of solar energy they can
generate.
• The performance of a photovoltaic array is dependent upon sunlight.
• Climate (e.g. clouds, fog) has a significant effect on the amount of solar
energy received by a PV array and, in turn, its performance.

• To increase their utility, a number of individual PV cells are
interconnected together in a sealed, weather proof package
called a Panel (Module).
• For example, a 12 V Panel (Module) will have 36 cells
connected in series and a 24 V Panel (Module) will have 72
PV Cells connected in series.
• To achieve the desired voltage and current, Modules are
wired in series and parallel into what is called a PV Array.

 The cells are very thin and fragile so they are sandwiched
between a transparent front sheet, usually glass, and a backing
sheet, usually glass or a type of tough plastic.
 This protects them from breakage and from the weather.
 An aluminum frame is fitted around the module to enable easy
fixing to a support structure.
 PV / Solar cells are wired in series and in parallel to form a PV /
Solar Panel (Module).
 The number of series cells indicates the voltage of the Panel
(Module), whereas the number of parallel cells indicates the
current.

 The Equivalent circuit of a practical PV cell is shown below.
 The current I at the output terminals is equal to the light-
generated current IL (Iph), less the diode current ID and the
shunt-leakage current ISH.
 The series resistance Rs represents the internal resistance to
the current flow, and depends on the PN junction depth,
impurities, and contact resistance.
Equivalent Circuit of
PV Cell

 The shunt resistance RSH is inversely related to the leakage
current to ground.
 In an ideal PV cell, Rs = 0 (no series loss), and RSH = ∞ (no
leakage to ground).
 In a typical silicon cell, Rs varies from 0.05 to 0.10 Ω and RSH
from 200 to 300 Ω.
 The PV conversion efficiency is sensitive to small variations in
Rs, but is insensitive to variations in RSH.
 A small increase in Rs can decrease the PV output significantly.
PV Cell

 The current in a diode increases exponentially if the applied
voltage is more than cut-in voltage.
 Diode current equation is expressed by:
 VT = KT/q
 K = Boltzman Constant
 T = Temperature rise.
 q = Charge
 Current flowing through load I = IL – ID – ISH.
PV Cell

 The shunt resistance takes the leakage current generated at
the junction. If RSH is high, the PV cell is said to be
qualitative one otherwise it is said to be defective one.
I = IL – ID – ISH.
PV Cell

 The current and voltage (I-V) characteristics of a particular
photovoltaic (PV) cell, module or array giving a detailed
description of its solar energy conversion ability and efficiency.
 Knowing the electrical I-V characteristics of a solar cell, or panel
is critical in determining the device’s output performance and
solar efficiency.
 The intensity of the solar radiation that hits the cell controls the
current (I), while the increases in the temperature of the solar cell
reduces its voltage (V).
I-V Characteristics

 Solar cells produce direct current (DC) electricity and current
times voltage equals power, so we can create solar cell I-V curves
representing the current versus the voltage for a photovoltaic
device.
 Solar Cell I-V Characteristics Curves are basically a graphical
representation of the operation of a solar cell or module
summarizing the relationship between the current and voltage at
the existing conditions of irradiance and temperature.
 I-V curves provide the information required to configure a solar
system so that it can operate as close to its optimal peak power
point (MPP) as possible.
I-V Characteristics

 The graph shows the current-voltage ( I-V ) characteristics of a typical silicon PV cell
operating under normal conditions.
 The power delivered by a solar cell is the product of current and voltage (IxV).
 If the multiplication is done, point for point, for all voltages from short-circuit to
open-circuit conditions, the power curve above is obtained for a given radiation level.
 With the solar cell open-circuited, that is not connected to any load, the current will
be at its minimum (zero) and the voltage across the cell is at its maximum, known as
open circuit voltage Voc.
 At the other extreme, when the solar cell is short circuited, that is the positive and
negative leads connected together, the voltage across the cell is at its minimum (zero)
but the current flowing out of the cell reaches its maximum, known as the solar cells
Short circuit current ISC.
I-V Characteristics

Sizing Objectives:
 Sizing is the basis for PV system electrical designs, and establishes the
sizes and ratings of major components needed to meet a certain
performance objective
 The sizing of PV systems may be based on any number of factors,
depending on the type of system and its functional requirements.
Sizing Principles : The sizing principles for interactive and stand-alone
PV systems are based on different design and functional requirements.
Utility-Interactive Systems (without energy storage):
1. Provide supplemental power to facility loads.
2. Failure of PV system does not result in loss of loads.
Stand-Alone Systems (with energy storage):
1. Designed to meet a specific electrical load requirement.
2. Failure of PV system results in loss of load.
System design: storage
sizing – PV system sizing

Sizing Stand-Alone Systems
The sizing objective for any type of stand-alone PV system is a critical balance between energy supply and
demand.
 The PV array must provide enough energy to meet the load plus system losses under the worst case
conditions.
 Consequently, the efficiency of the electrical loads is a critical concern.
 Stand-alone PV systems can be considered a type of banking system.
 The battery is the bank account.
The PV array produces energy (income)
Charges the battery (deposits),
Electrical loads consume energy
(withdrawals).

 Fill factor represents the quality of a given PV cell.
 It is defined as the ratio of maximum Power to the theoritial power.
1. Stand-alone PV systems are sized to meet specific load
requirements, and involve the following key steps:

2.Load Analysis:
The daily DC energy required is used to size the battery and PV array.
The peak AC power demand dictates the size of inverter required.
3.Critical Design Analysis:
4.Selecting the System DC Voltage:
5.Selecting an Inverter:
Nominal system DC voltage
AC output voltage
Peak AC power required for cumulative load
Surge current requirements, if any
Additional features (battery charger, etc.)

6.System Availability:
7.Sizing the Battery:
• Desired days of storage to meet system loads with no recharge from
PV
• Temperature and discharge rates
• System losses and efficiencies
• The system voltage defines the number of series-connected battery
cells required.
• The total capacity needed defines the number of parallel battery
strings required.

8.Autonomy:
9.Factors Affecting Battery Sizing:
10.Sizing the Battery:
Battery sizing is based on rated capacity and specified limits of
operation.
11. Sizing the PV Array:
12.PV Array Battery Charging:

Fill Factor & Efficiency
of Solar Cell
Fill factor represents the quality of a given PV cell.
It is defined as the ratio of maximum Power to the theoretical
power.
FF = 1 will be obtained under ideal condition
Efficiency of a solar cell : It is defined as the ratio of
maximum power generated by the PV cell to the power
received from solar radiation.

Maximum Power Point
Tracking (MPPT)
What is MPPT ?
• PV modules still have relatively low conversion efficiency. Therefore,
controlling maximum power point tracking (MPPT) for the solar array is
essential in a PV system.
• The amount of power generated by a PV depends on the operating voltage
of the array.
• A PV’s maximum power point (MPP) varies with solar insulation and
temperature.
• MPPT or Maximum Power Point Tracking is an algorithm that included in
charge controllers used for extracting maximum available power from PV
module under certain conditions.
• The voltage at which PV module can produce maximum power is called
‘maximum power point’.

Maximum Power Point
Tracking (MPPT)
How MPPT works?
• The major principle of MPPT is to extract the maximum
available power from PV module by making them operate
at the most efficient voltage (maximum power point).
• MPPT checks output of PV module, compares it to battery
voltage then fixes what is the best power that PV module
can produce to charge the battery and converts it to the best
voltage to get maximum current into battery.
• MPPT is most effective under Cold weather, cloudy or
hazy days.

Maximum Power Point
Tracking (MPPT)
MPPT solar charge controller:
• A MPPT solar charge controller is the charge controller embedded
with MPPT algorithm to maximize the amount of current going into
the battery from PV module.
• MPPT is a DC to DC converter which operates by taking DC input
from PV module, changing it to AC and converting it back to a
different DC voltage and current to exactly match the PV module to
the battery.
• Boost converter
• Buck converter
• MPPT algorithm can be applied to both of them depending on
system design.

Maximum Power Point
Tracking (MPPT)
The general block diagram for MPPT:

Buck Converter

BOOST Converter

MPP Tracking

Perturb and Observe
(P&O) method
• It is most simple approach which moves
operating point towards the maximum
power point by varying the PV output
voltage.
• In this technique, a minor perturbation is
introduced to cause the power variation of
the PV module.
• The PV output power is periodically
measured and compared with the previous
power.
• If the output power increases, the same
process is continued otherwise
perturbation is reversed.

Perturb and Observe
(P&O) method
• This way, the operating point of the MPP and oscillates
around it in steady - state condition.
• Large perturbation step sizes yield fast tracking of the
MPP under varying atmospheric conditions but results in
reduced average power conversion due to large
oscillations around MPP.
• Hence, a trade off between faster response and steady-
state oscillations is required.
• Moreover, the perturbation is not generic.
• In order to overcome all this a high performance P&O
technique is proposed.

Hill Climbing Method

General Algorithm for
MPPT

 Sources of wind energy
 Wind patterns
 Types of turbines
 –Horizontal axis and vertical axis machines
 Kinetic energy of wind
 Betz coefficient – Tip–speed ratio – Efficiency – Power output of
wind turbine
 Selection of generator(synchronous, induction)
 Maximum power point tracking
 Wind farms – Power generation for utility grids
Unit-3
Wind Energy

 Wind energy is electricity created from the naturally flowing air
in the Earth's atmosphere.
 Wind power or wind energy describes the process by which the
wind is used to generate mechanical power or electricity.
 Wind turbines converts the kinetic energy in the wind into
mechanical power that will be converted to electrical energy.
 As a renewable resource that won't get depleted through use, its
impact on the environment and climate crisis is significantly
smaller than burning fossil fuels.
Introduction

Advantages of Wind
Energy
1. Wind Energy Is Renewable & Sustainable
2. It’s also Environmentally Friendly
3. It Can Reduce Fossil Fuel Consumption
4. Wind Energy is Free
5. Both Industrial & Domestic Wind Turbines Exist
6. Wind Energy Can Provide Power For Remote Locations
7. Wind Technology is Becoming Cheaper
8. It Is Also Low Maintenance
9. It Has Low Running Costs
10. Wind Energy Has Huge Potential
11. It Can Increase Energy Security
12. The Wind Energy Industry Creates Jobs

1. The Wind Fluctuates
2. Installation is Expensive
3. Wind Turbines Pose a Threat to Wildlife
4. Wind Turbines Create Noise Pollution
5. They also create Visual Pollution
Disadvantages of Wind
Energy

Wind power status in
INDIA
Installed wind capacity by state as of 31st March
2021
State Total Capacity (MW)
Tamil Nadu 9608.04
Gujarat 8561.82
Maharashtra 5000.33
Karnataka 4938.60
Rajasthan 4326.82
Andhra Pradesh 4096.65
Madhya Pradesh 2519.89
Telangana 128.10
Kerala 62.50
Others 4.30
Total 39247.05
• There is a growing number of wind
energy installations in states across India.
Wind power generation capacity in India
has significantly increased in recent
years.
• As of 1st July 2022, the total installed
wind power capacity was 40.788 GW, the
fourth largest installed wind power
capacity in the world.
• Wind power capacity is mainly spread
across the Southern, Western and
Northern Western regions.

i. The wind energy conversion system should be placed
in the area where the winds are strong and consistent.
ii. The site should be near to the transportation
facilities such as road and railway facilities
iii. The environmental conditions should not effect the
turbine blades and electrical apparatus.
iv. The site selected should be near to the consumer
terminals.
v. The land cost should be low with suitable ground
conditions
vi. Site of the wind energy conversion system must be at
high altitude when compared to the remaining area.
Site selection of wind
energy

i. Pressure Gradient Force: This is the force generated due to
the differences in horizontal pressure, and it operates from
the high pressure area to a low pressure area.
ii. Coriolis Force: Due to the earth’s rotation winds in the
northern hemisphere get deflected to the right of their path
and those in the southern hemisphere to their left. The
Coriolis force changes wind direction but not its speed.
iii. Frictional Force: The irregularities of the earth’s surface
offer resistance to the wind motion in the form of friction.
This force determines the angle at which air will flow as well
as the speed at which it will move and may also alter wind
direction.
iv. Wind speed also varies as it passes through mountain gaps.
v. Climate disturbances caused by rains, thunders etc.
Factors affecting the
distribution of wind energy
on the earth surface

Intertropical Convergence Zone (ITCZ)- The Intertropical
Convergence Zone is also known as Equatorial Convergence Zone
or the Inter tropical Front.
Global Wind Patterns
It forms when southeast
and northeast trade
winds converge in a low
pressure zone, near the
equator.
It usually appears as a
band of clouds and
comes with
thunderstorms, which
are short but produce
extreme amounts of
rain.

Global Wind Patterns
The Four Major Wind Systems and Wind Belts:
Polar Easterlies- Polar Easterlies can be found at the north and
south poles and they are cold and dry because of where it is located,
which is at high latitudes. This type of wind system forms when
cool air, at the poles, and then transfers to the equator. Polar
Easterlies are located 60-90 degrees latitude in both the southern and
northern hemispheres.
Tropical Easterlies- Tropical Easterlies take direction in an east to
west flow because of the rotation of the Earth. As air from the
equator rises, it gets warmer and when it cools down, it comes back
down to the equator. Tropical easterlies are located 0-30 degrees
latitude in both hemispheres.
Prevailing Westerlies- Prevailing Westerlies are located in the 30-60
degrees latitude in the northern and southern hemispheres. They
blow from west to east and occur in the clement part of the Earth.

i. Wind energy conversion systems (WECS) are designed
to convert the energy of wind movement into
mechanical power.
ii. With wind turbine generators, the mechanical energy is
converted into electricity.
iii. In windmills this electrical energy is used to do works
such as pumping water, mill grains, or drive machinery.
iv. The life span of modern wind turbines is now 20-25
years.
v. The cost of wind power has continued to decline
through technological development, increased
production level, and the use of larger turbines.
Wind Energy Conversion
System (WECS)

i. The major components of a typical wind energy conversion system
include a wind turbine, a generator, interconnection apparatus, and
control systems.
ii. Generators used for wind turbines will be synchronous generators,
permanent magnet synchronous generators, and induction generators,
including the squirrel-cage type and wound rotor type.
iii. For small to medium power wind turbines, permanent magnet
generators and squirrel-cage induction generators are often used
because of their reliability and cost advantages.
iv. Interconnection apparatuses are devices to achieve power control, soft
start, and interconnection functions.
v. Very often, power electronic converters are used as such devices.
vi. For certain high power wind turbines, effective power control can be
achieved with double PWM (pulse-width modulation) converters
which provide a bidirectional power flow between the turbine
generator and the utility grid.
System (WECS)

System (WECS)

i. HAWT are the common type of wind turbine.
ii. HAWT have the main rotor shaft and electrical generator at
the top of a tower, and they must be pointed into the wind.
iii. Small turbines are pointed by a simple wind vane placed with
the rotor, while large turbines generally use a wind sensor
coupled with a servo motor to turn the turbine into the wind.
iv. Most large wind turbines have a gearbox, which turns the slow
rotation of the rotor into a faster rotation to drive an
electrical generator.
v. Wind turbine blades are made stiff to prevent the blades from
being pushed into the tower by high winds.
vi. Additionally, in high winds the blades can be allowed to bend
which reduces their swept area and thus their wind resistance.
vii. Most of the HAWTs are upwind machines.
Horizontal Axis Wind Turbine (HAWT)
Types of Wind Turbine:

Advantages of HAWT:
i. The tall tower base allows access to stronger wind in sites.
In some wind shear sites, every ten meters up the wind
speed can increase by 20% and the power output by 34%.
ii. High efficiency, since the blades always move
perpendicularly to the wind, receiving power through the
whole rotation.
Horizontal Axis Wind
Turbine (HAWT)

Disadvantages of HAWT:
i. Massive tower construction is required to support the heavy
blades, gearbox, and generator.
ii. Components of a horizontal axis wind turbine being lifted
into position.
iii. Downwind variants suffer from fatigue and structural
failure caused by turbulence when a blade passes through
the tower’s wind shadow
iv. HAWTs require an additional yaw control mechanism to
turn the blades toward the wind.
v. HAWTs generally require a braking or yawing device in
high winds to stop the turbine from spinning and destroying
or damaging itself.
Horizontal Axis Wind
Turbine (HAWT)

i. The VAWT is a type of wind turbine and it is most frequently
used for residential purposes.
ii. This turbine includes the rotor shaft and two or three blades
where the rotor shaft moves vertically.
iii. The generator is placed at the bottom of the tower whereas the
blades are covered around the shaft.
iv. The rotors in the turbine revolve around a vertical shaft by
using vertically oriented blades.
v. The wind operates the rotor which is connected to the
generator, so the generator converts the energy from
mechanical to electrical.
vi. Vertical axis wind turbine components are blade, shaft,
bearing, frame & blade support.
Vertical Axis Wind
Turbines (VAWT)

i. They can produce electricity in any wind direction.
ii. Strong supporting tower in not needed because generator, gearbox
and other components are placed on the ground.
iii. Low production cost as compared to horizontal axis wind turbines.
iv. As there is no need of pointing turbine in wind direction to be
efficient. so yaw drive and pitch mechanism is not needed.
v. Easy installation as compared to other wind turbine.
vi. Easy to transport from one place to other.
vii. Low maintenance costs and suitable in urban areas.
viii. Low risk for humans and birds because blades moves at relatively
low speeds.
ix. They are particularly suitable for areas with extreme weather
conditions, like in the mountains.
VAWT Advantages

1. As only one blade of the wind turbine works at a time, efficiency is
very low compared to HAWTS.
2. They need an initial push to start; this initial push that to make the
blades start spinning on their own must be started by a small motor.
3. When compared to horizontal axis wind turbines they are very less
efficient because of the additional drag created when their blades
rotate.
4. They have relative high vibration because the air flow near the
ground creates turbulent flow.
5. Because of vibration, bearing wear increases which results in the
increase of maintenance costs.
6. They can create noise pollution.
7. VAWTs may need guy wires to hold it up.
VAWT
Disadvantages

Wind Turbine Parts
and Functions
Foundation: It is a large and heavy structured block of
concrete that must hold the whole turbine and the forces
that affect it.
Tower: The tower in most modern turbines is round tubular
steel of a diameter of 3–4 m, with a height of 75–110 m,
depending on the size of the turbine and its location.
The rule of thumb for a turbine tower is that it has the same
height as the diameter of the circle its blades make when
rotating.
Normally, the taller a turbine is, it is subject to more of the
wind with higher speed.

Wind Turbine Parts
and Functions
Rotor: The rotor is the rotating part of a turbine; it consists of (mostly) three blades and the central part
that the blades are attached to, the hub.
The three-blade rotor has the best efficiency and other advantages.
Blades are not solid; they are hollow and are made of composite material to be light and strong.
They are not flat and have a twist between their root and their tip.
The blades can rotate up to 90° about their axes. This motion is called blade pitch.
Hub: The function of the hub is to hold the blades and make it possible for them to rotate with respect to
the rest of the turbine body.
Generator: The generator is the component that converts the mechanical energy of the rotor, harnessed
from wind to electrical energy.
In general, the choice of generator is synchronous or asynchronous (induction) generator.

Wind Turbine Parts
and Functions
Nacelle: The nacelle is housing on top of the tower that accommodates all the components that need to
be on a turbine top.
A major turbine part among these components is the generator and the turbine shaft that transfers the
harvested power from wind to the generator through a gearbox.
The gearbox is a vital component of wind turbines; it resides in the nacelle.
A gearbox increases the main shaft speed from around 12–25 rpm to a speed suitable for its
generator.
For this reason, the shaft on the generator side is called “high-speed shaft.”
Because a turbine must follow the wind and adjust its orientation to the wind direction, its rotor needs
to rotate with respect to the tower.
This rotation is called yaw motion in which the nacelle and the rotor revolve about the tower axis.

• The pitch angle of the blade is controlled by rotating from
its root where it is connected to the hub.
• This mechanism is provided through thr hub using a
hydraulic jack in the nacelle. The control system
continuously adjust the pitch to obtain optimal performance.
Pitch Angle Control Mechanism

i. The yaw control mechanism comprises a motor and drive.
ii. The main purpose of this arrangement is to move the nacelle
and blades according to the wind direction.
iii. It enables the wind turbine to capture the maximum available
wind.
iv. During the nacelle movement, a fair chance of cable twisting
occurs inside the tower.
Yaw Control Mechanism

Dutch Windmill:
i. Man has used Dutch windmills for a long time. In fact the
grain grinding windmills that were widely used in Europe
since the middle ages were Dutch. These windmills were
operated on the thrust exerted by the wind.
ii. The blades, generally four, were inclined at an angle to the
plane of rotation.
iii. The wind being deflected by the blades exerted a force in
the direction of rotation.
iv. The blades were made of sails or wooden slats.
Types of HAWT

Types of VAWT
The Vertical-Axis Wind Turbine (VAWT) is a wind turbine that has its main rotational axis oriented in the
vertical direction. The two types of vertical-axis wind turbines are:
Darrieus wind turbine: which turns a shaft using lift forces
Savonius wind turbine: whose cups are pushed by direct wind forces.

i. Savonius wind turbine includes the blades which are arranged
around the vertical shaft within a helix form.
ii. One of the most significant features of this turbine is the solid
wind-receiving area.
iii. These turbines mainly rely on the mechanism of flow
resistance to make the rotors active which means, the dynamic
force of the wind against the turbine blades thrust the rotor
into revolution.
iv. Simultaneously, the reverse side of the blades meets an
aerodynamic resistance force.
v. This is like when running or cycling, we experience the
airflow coming opposite to us.
vi. Because of this, these turbines can simply turn fast like the
wind speed.
Savonius Wind Turbine

i. Darrieus wind turbine name is taken from the French inventor
namely; Georges Darrieus.
ii. It is also called an egg-beater.
iii. These turbines include curved & long wings where each end of
these wings is connected to the top & base of the rotor shaft.
iv. These types of wind turbines use the aerodynamic force of the
lift to revolve.
v. By flowing around the construction, the wind will create suction
on the front face of the wind turbine to drive the wings to
revolve.
vi. Like Savonius turbines, these turbines do not experience as
much drag due to the shape of wings.
vii. Once the revolution begins, these turbines will go faster to
rotate faster than the speed of the wind.
Darrieus wind turbine

Power extraction
from Wind
• Wind turbine is used to harness useful
mechanical power from wind.
• The rotor of the turbine collects energy from the
whole area swept by the rotor.
• For the purpose of simple analysis a smooth
laminar flow with no perturbations is assumed.
• A horizontal axis wind turbine, which is most
commonly used, is considered. The rotor may
be considered as an actuator disk across which
there is reduction of pressure as energy is
extracted.
• As air mass flow rate must be same everywhere
within the stream tube the speed must decrease
as air expands.
• The stream tube model shown in below figures:

There are four types of wind turbine generators (WTGs) which
can be considered for the various wind turbine systems, those
are:
i. Direct Current (DC) Generators
ii. Alternating Current (AC) Synchronous Generators
iii. AC Asynchronous Generators, and
iv. Switched Reluctance Generators.
 Each of these generators can be run at fixed or variable speed.
 Due to the dynamic nature of wind power, it is ideal to operate the
WTGs at variable speed.
 Operating a generator at variable speed reduces the physical stress
on the turbine blades and drive.
Types of Generators in
Wind Turbines

i. This is very unusual except in the situations of low power
demand.
ii. A DC wind generator system has a wind turbine, a DC
generator, inverter, a transformer, a controller, and a power grid.
iii. For shunt-wound DC generators, the field current increases with
operational speed, whereas the balance between the wind
turbine drive torque determines the actual speed of the wind
turbine.
iv. Electricity is extracted through brushes, which connect the
commutator that is used to convert the generated AC power into
DC output and are relatively costly.
DC Generator

i. AC synchronous wind turbine generators can take constant or DC
excitations from either permanent magnets or electromagnets.
ii. When the wind turbine drives the rotor, three-phase power is produced
in the stator windings that are connected to the grid via transformers
and power converters.
iii. In the case of fixed-speed synchronous generators, the rotor speed
needs to be at exactly the synchronous speed.
iv. When using fixed-speed synchronous generators, random fluctuations
of wind speed and periodic disturbances happen due to tower-shading
effects.
v. These generators more complex, costly, and prone to failure.
AC Synchronous
Generator

i. Modern wind power systems use induction machines, extensively in
wind turbine applications.
ii. The induction generators are classified into two types: fixed-speed
induction generators (FSIGs) with squirrel cage rotors, and doubly-fed
induction generators (DFIGs) with wound rotors.
iii. Generally, induction generators are simple, reliable, inexpensive, and
well-designed.
iv. Squirrel cage induction generators (SCIGs) can be used in variable
speed wind turbines.
v. In such cases, the output voltage, however, can not be controlled, and
the external supply of reactive power is required.
AC Asynchronous
Generator

Wind Efficiency : It is defined as the ratio of power extracted by wind
turbine to the power available in the wind.
The maximum efficiency that can be extracted by wind turbine is: 59.25 %
Tip Speed Ratio : It is the ratio of speed of the tip of the rotor blade
to the speed of the wind.
In order to extract maximum power from the wind, choosing of number of
blades as well as their connection to the hub is very important.
Definitions

Blade Time (tb): It is time taken by each blade to occupy the position of
preceding blade. If a turbine is having ‘n’ number of blades
Wind time (tw) : It is the time taken by the wind to pass through the turbine
blades, which is given by:
Where, d is the length of wind passed through the blades.
uo speed of the wind.
Definitions

i. The Tip Speed Ratio (often known as the TSR) is of vital importance
in the design of wind turbine generators.
ii. If the rotor of the wind turbine turns too slowly, most of the wind will
pass undisturbed through the gap between the rotor blades.
iii. Alternatively if the rotor turns too quickly, the blurring blades will
appear like a solid wall to the wind.
iv. Therefore, wind turbines are designed with optimal tip speed ratios to
extract as much power out of the wind as possible.
v. The tip speed ratio is given by dividing the speed of the tips of the
turbine blades by the speed of the wind
–for example if a 20 mph wind is blowing on a wind turbine and the tips of
its blades are rotating at 80 mph, then the tip speed ration is 80/20 = 4.
 The optimum tip speed ratio depends on the number of blades in the wind
turbine rotor. A two-bladed rotor has an optimum tip speed ratio of around
6, a three-bladed rotor around 5, and a four-bladed rotor around 3.
Tip Speed Ratio (TSR)

Biomass Energy: Fuel classification
– Pyrolysis
– Direct combustion of heat
– Different digesters and sizing.
Fuel cell: Classification of fuel for fuel cells
– Fuel cell voltage
– Efficiency
– V-I characteristics.
Geothermal: Classification
– Dry rock and hot acquifer
– Energy analysis
– Geothermal based electric power generation
Unit-5: Biomass, fuel cells
and geothermal systems

Biomass - Introduction
What is Biomass?
Plant material, either raw or processed
Such examples include:
 Fast-growing trees and grasses, like hybrid poplars or
grass
 Agricultural residues, like corn stover, rice straw, wheat
straw, or used vegetable oils
 Wood waste, such as sawdust and tree prunings, paper
trash and yard clippings

How can Biomass
produce useful energy?
 Biomass is used to meet a variety of energy needs, including generating
electricity, heating homes, fueling vehicles and providing process heat for
industrial facilities.
 Various forms of biomass energy account for nearly 4 percent of all
energy consumed in the U.S. and 45 percent of renewable energy used
in the U.S.
 Biomass can also be combined with coal in existing coal plants to
produce cleaner emissions; this is called Co firing.
 Liquid fuel that is made from solid biomass can be used in piston-
driven engines, high-efficiency gas turbine generators or fuel cells.

Generating Electricity
 Direct Combustion
 Burned to produce steam, the steam turns a turbine and
the turbine drives a generator, producing electricity.
Because of potential ash build-up, only certain types of
biomass materials are used for direct combustion.
 Gasification
 Gasifiers are used to convert biomass into a
combustible gas (biogas). The biogas is then used to
drive a high-efficiency, combined-cycle gas turbine.

Advantages of
Biomass
• Environmentally Friendly
• It can be used in a wide variety of processes such as the
production of clean transportation fuels, electricity and
chemicals.
• With proper use, it can reduce the dependency on
conventional fuels.
• it can help to reduce the production of harmful greenhouse
gases.
• It will help to create jobs.
• Less land will be needed to meet the demand, this in turn
free up land for other uses.
• Farmers will get more money due to selling of their waste.

Disadvantages of
Biomass
 Commercialization of biomass is costly.
Government subsidies are necessary for businesses
to survive, due to expensive pretreatment.
 The pretreatment process, a necessary step to
convert the biomass into a useful fuel, is
inefficient because during fermentation of sugars,
almost half of the usable energy is lost.
 The resulting fuel, has a lower energy content than
gasoline.
 It requires 15-30% more volume for the same
amount of energy as gasoline.
 High transportation costs due to high water content.

Biomass Hierarchy
Biomass
Energy
Consumption
Wood
Wood
Fuel
Wood
Byproducts
Wood
waste
Waste
Solid
Waste
Landfill
Mass
Burning
Manufacturing
Process
Waste
Alcohol fuels
Ethanol

The basic thermo-chemical process to convert biomass into
more valuable and/or convenient product is known as
pyrolysis.
It is the thermal decomposition of biomass occurring in the
absence of oxygen. It is the fundamental chemical reaction
that is the precursor of both the combustion and gasification
processes and occurs naturally in the early stage. The products
of pyrolysis include biochar, bio-oil and gases including
methane, hydrogen, carbon monoxide, and carbon dioxide.
Pyrolysis

Biomass Conversion
Technologies

Biochemical conversion utilizes bacteria and enzymes to break
down biomass molecules.
Anaerobic/Aerobic Digestion
 In anaerobic digestion, the bacteria access oxygen from the
biomass itself, not from the air, to produce methane and
carbon dioxide.
 Aerobic digestion, or composting, breaks down biomass in
the presence of oxygen while using microorganisms that
take the oxygen from the air, producing carbon dioxide,
heat, and a solid digestate.
BIOCHEMICAL
CONVERSION

Fermentation:
 Fermentation converts the biomass partially into sugars
using acids and/or enzymes. The sugars can be converted
into ethanol or other chemicals with the addition of yeast.
 The principal products of fermentation are liquids.
Enzymatic/Acid Hydrolysis:
 Cellulosic ethanol, which would rely upon the conversion of
the non-starch/sugar portions of biomass (lignocellulose),
has not been as successful as the pretreatment of the
feedstocks through hydrolysis.
 It has proven to be less efficient and economical
BIOCHEMICAL
CONVERSION

Thermochemical conversion processes include combustion, gasification,
pyrolysis, and solvent liquefaction.
Combustion:
• Combustion was one of the first advanced uses of biomass conversion.
• Combustion is an exothermic (heat-producing) reaction between oxygen and
the hydrocarbon in biomass.
• The biomass is converted into heat, water, and carbon dioxide.
• Biomass combustion remains a major source of energy production
throughout the world and has replaced coal as a renewable source of energy
in many power plants.
• The advantages of combustion include the extreme simplicity of process
operation: burning.
• The biomass combustion is discouraged due to the release of polluting
contaminations, gasification and other processes may be favored due to
lower concentrations of CO2, SO2, NOx and solid waste in the end products
THERMO CHEMICAL
CONVERSION

Gasification:
 Gasification is defined as a high-temperature conversion of
carbonaceous materials into a combustible gas mixture
under reducing conditions.
 Through gasification, a heterogeneous solid material can be
converted into gaseous fuels intermediate that can be used
for heating, industrial processes, electricity generation, and
liquid fuel production.
THERMO CHEMICAL
CONVERSION
Gasification of biomass has four key steps:
1. Heating & Drying 2. Pyrolysis
3. Gas Solid Reactions 4. Gas Phase Reactions

Hydrothermal
Liquefaction
 Hydrothermal liquefaction is a relatively low-temperature, a
high-pressure process that produces bio-oil from relatively
wet biomass in the presence of a catalyst and hydrogen.
 Biomass with high water content may be directly utilized
without energy-intensive pretreatment and converted into a
bio-oil and platform chemicals.
 The bio-oil has certain similarities to petroleum crude and
can be upgraded to the whole distillate range of petroleum-
derived fuel products.
 Hydrothermal liquefaction is essentially pyrolysis in hot
liquid water.
 Liquefaction’s main use case involves the conversion of
bio-organic waste with high water content, including wet
primary and secondary sludges.

Factors Affecting
Anaerobic Digestion
Digestion
Basic factors Environmental
factors
Time
Bacteria
Food
Contact
Toxics
pH
Temperature

Bio Gas plants are classified in to
1. Batch Type
2. Continuous Type
a. Fixed Dome Type (Constant Volume)
b. Floating Drum Type (Constant Pressure)
Classification of Bio Gas
plant

 Batch type plant is charged at 50–60 days interval.
 Once charged, it starts supplying the gas after 8–10 days and continues to do so for about
40–50 days till the process of digestion is completed.
 Afterwards it is emptied and recharged.
 A battery of digesters are charged and emptied one by one in a synchronous manner to
maintain regular supply of gas through common gasholder.
Batch Type Bio Gas
plant
 The installation and operation of
such plants are capital and labor
intensive and are not economical
unless operated on large scale.
 Such plants are installed in
European countries and do not suit
to conditions in Indian rural areas.

Continuous Type Bio Gas plant
 The plant is fed daily with certain quantity of biomass.
 The gas produced is stored in the plant or in a separate gasholder and remains available for
use as required.
 The biomass while slowly passing through the digester is completely digested and the
digested slurry is rejected through an outlet.
 The period during which the biomass remains in the digester is known as retention period,
which depends mainly on the type of biomass and operating temperature.
 The plant operates continuously and stopped only for maintenance or for removal of sludge.
 A thin dry layer often formed at the top of slurry is known as scum.
 The scum tends to prevent the escape of gas from slurry.
 The scum layer is broken by slowly stirring the slurry.
 This also helps in digestion process due to better mixing.
 Such plants are convenient for individual owners as feeding pattern matches with daily waste
generation and do not require its storage.
 These types of plants are very popular in India and China.

Floating drum (KVIC )
type biogas plant
 This is popularly called Gobar gas plant.
 Floating-drum plants consist of an underground
digester (cylindrical or dome-shaped) and a moving
gas-holder.
 The gas-holder floats either directly on the
fermentation slurry or in a water jacket of its own.
 The gas is collected in the gas drum, which rises or
moves down, according to the amount of gas stored.
 The gas drum is prevented from tilting by a guiding
frame.
 When biogas is produced, the drum moves up and
when it is consumed, the drum goes down.
 If the drum floats in a water jacket, it cannot get
stuck, even in substrate with high solid content.

Floating drum type
biogas plant
Advantages: Simple, easily understood operation, constant
gas pressure, volume of stored gas visible directly, few
mistakes in construction.
Disadvantages:
 High construction cost of floating-drum, many steel parts
liable to corrosion, resulting in short life, regular maintenance
costs due to painting.
 In spite of these disadvantages, floating-drum plants are
always to be recommended in cases of doubt.
 The drum won’t stick, even if the substrate has a high solids
content.
 Floating-drums made of glass-fibre reinforced plastic and high
density polyethylene have been used successfully, but the
construction cost is higher than with steel.

Fixed drum (Janta) type biogas plant
 The fixed dome type bio gas plant consists
of a closed underground digester tank
made up of bricks which has a dome
shaped roof also made up of bricks.
 This dome shape roof of the digester tank
functions as gas holder and has an outlet
pipe at the top to supply gas to homes.
 The slurry is prepared by mixing water in
cattle dung in equal proportion in mixing
tank.

Fixed drum type
biogas plant
 The slurry is then sent into the digester tank with the help of inlet chamber.
 It should be noted that slurry is fed into the digester tank up to the point where
the dome of the roof starts.
 Inside the digester tank, the complex carbon compounds present in the cattle
dung breaks into simpler substances by the action of anaerobic microorganisms
in the presence of water.
 This anaerobic decomposition of complex carbon compounds present in cattle
dung produces bio gas and gets completed in about 60 days.
 The bio gas so produced starts to collect in dome shaped roof of bio gas plant
and is supplied to homes through pipes.
 The spent slurry is replaced from time to time with fresh slurry to continue the
production of bio gas.

Fixed drum type
biogas plant
Advantages:
 Fixed dome biogas units have low construction cost, no moving parts, no
rusting steel parts, hence long life (20 years or more), underground
construction, affording protection from winter cold and saving space,
creates employment locally.
Disadvantages:
 Gas pressure fluctuates substantially and is often very high, low digester
temperatures.
 Fixed-dome plants can be recommended only where construction can be
supervised by experienced biogas technicians.

Comparison of Floating Drum and Fixed Dome Type
Plants

Selection of construction sites are mainly governed by the following factors:
 The site should facilitate easy construction works.
 The selected site should be such that the construction cost is minimized.
 The selected site should ensure easy operation and maintenance activities like feeding of
plant, use of main gas valve, composing and use of slurry, checking of gas leakage,
draining condensed water from pipeline etc.
 The site should guarantee plant safety.
 To make plant easier to operate and avoid wastage of raw materials, especially the
dung/swine manure, plant must be as close as possible to the cattle shed.
 The site should be in slightly higher elevation than the surrounding, which helps in
avoiding water logging. This also ensures free flow of slurry from overflow outlet to the
composting pit.
Site Selection for Biogas plant

 For effective functioning of bio-digesters, right temperature (20-35°C) has to be maintained
inside the digester. Therefore it is better to avoid damp and cool place – Sunny site is
preferable.
 To mix dung and water or flush swine manure to the digester, considerable quantity of
water is required. If water source is far, the burden of fetching water becomes more.
 The well or ground water source should be at least 10 meter away from the biodigester.
 If longer gas pipe is used the cost will be increased as the conveyance system becomes
costly, and also increases the risk of gas leakage.
 The main gas valve which is fitted just above the gas holder should be opened and closed
before and after the use of biogas.
 The site should be at sufficient distance from trees to avoid damage from roots.
 Type of soil should have enough bearing capacity to avoid the possibility of sinking of
structure.
Site Selection for Biogas plant

Size Selection for
Biogas plant
Sizing of biogas plant follows based on three parameters
 Daily feed
 Retention time
 Digester volume
• The biogas plant size is dependent on the average daily feed stock and
expected hydraulic retention time of the material in the biogas system.
• Capacity of the plant should be designed based on the availability of
raw materials.
• Capacity of the plant indicates the quantity of gas produced in a day.
• Based on the study, 1 kg of cow dung along with equal quantity of water
(1:1) under anaerobic conditions in a day produces 40 litres of biogas.

 A fuel cell is a device that converts the chemical energy of a
fuel directly into electricity by electrochemical reactions.
 It uses the chemical energy of hydrogen or other fuels to
cleanly and efficiently produce electricity.
 If hydrogen is the fuel, the products are electricity, water, and
heat.
 Fuel cells are unique in terms of the variety of their potential
applications; they can provide power for systems as large as a
utility power station and as small as a laptop computer.
Fuel Cells

Differences between
Fuel Cells and Battery
S.No Conventional cell (Battery) Fuel cell
1 Batteries store chemical energy Fuel cell do not store chemical
energy
2 Reactants are within the cell Reactants are supplied continuously
3 Products remain within the cell Products are continuously removed
from the cell
4 Harmful waste products are
formed
Harmful waste products are not
formed
5 They can be recharged They cannot be recharged
6 Efficiency is less Efficiency is more

 Low-to-Zero Emissions
 High Efficiency
 Reliability
 Fuel Flexibility
 Energy Security
 Durability
 Scalability
 Quiet Operation as it does not have any mechanical part.
Advantages of Fuel
Cells

1. Fuel cells are expensive in nature.
2. Fuel cells are difficult to store as the fuel used in the cells
require a particular temperature and pressure level to be
maintained.
3. Fuel cells are comparatively less durable.
4. The average lifespan of fuel cells is not quite high
Disadvantages And
Applications
Applications:
• Transportation
• Material Handling Equipment
• Backup Power Generation
• Electronic Gadgets
• Spacecrafts

 A fuel cell typically consists of two electrodes, namely, an
anode and cathode separated by an electrolyte membrane.
 The organic fuel that can be used in a fuel cell to produce
electricity includes hydrogen, methane, ethane, ethanol, etc.
 These fuels underdo combustion and release energy in the
form of heat.
 Most of such reactions produce water and carbon-di-oxide as
by-products and are prominently redox reactions.
 Redox reactions involve the transfer of electrons that leads to
the conversion of chemical energy into electrical energy.
 An electrolyte material is present between the electrodes.
 Fuel is supplied to both the electrodes individually.
Working Principle of Fuel
Cell

 For instance, let us say that in a fuel cell the hydrogen is fed to
the anode, while air is fed to the cathode.
 Here, the catalyst present at the anode side of the cell tends to
break the hydrogen molecules into smaller particles, i.e.,
protons and electrons.
 Both the elements try to move towards the cathode following
different paths.
 The electrons reach the cathode following an external path,
thereby producing the current, whereas the protons travel
through the electrolyte membrane and reach the cathode to
combine with oxygen molecules and electrons to produce
water and heat as by-products
Working Principle of Fuel
Cell

Characteristics of Fuel
Cells
 The VI characteristic of a fuel cell is shown in
Fig the operating point is fixed in range BC of
the characteristics where voltage regulation is
best and
 the output voltage is roughly around 0.6–0.8 V.
 At no load, the terminal voltage is equal to the
theoretical open circuit voltage.
 As the cell is loaded (current is supplied to
load), voltage and hence efficiency drops
significantly.
 The departure of output voltage from ideal emf
is mainly due to following reasons.
 1. Activation Polarization (Chemical
Polarization)
 2. Resistance Polarization
 3. Concentration Polarization

Activation Polarization
(Chemical Polarization)
 This is related to activation energy barrier for the
electron transfer process at the electrode.
 Certain minimum activation energy is required to be
supplied so that sufficient number of electrons is
emitted.
 At low current densities significant numbers of
electrons are not emitted.
 This energy is supplied by the output of the cell,
resulting in potential loss.
 It can be reduced by an effective electrochemical
catalyst and also by increasing the operating
temperature.

Resistance Polarization
 At larger current there is additional contribution
from internal electrical resistance of the cell.
 The internal resistance is composed mainly of
resistance of bulk electrolyte and interface
contact resistance between electrode and
electrolyte.
 The resistance polarization can be reduced by: (a)
using more concentrated (i.e. high conductivity)
electrolyte, (b) increasing the operating
temperature, and (c) using proper shape and
spacing of electrolyte to reduce the contact
resistance.

Concentration
Polarization
 This type of polarization tends to limit the
current drawn from the cell.
 This is related to mass transport within the cell
and may further be subdivided into two parts.
(a) Electrolyte polarization
(b) Gas side polarization

Hydrogen Fuel Cell
 A fuel cell is a lot like a battery.
 It has two electrodes where the reactions take place and
an electrolyte which carries the charged particles from
one electrode to the other.
 In order for a fuel cell to work, it needs hydrogen (H2)
and oxygen (O2).
 The hydrogen enters the fuel cell at the anode.
 A chemical reaction strips the hydrogen molecules of
their electrons and the atoms become ionized to form H+.
 The electrons travel through wires to provide a current to
do work.
 The oxygen enters at the cathode, usually from the air.
 The oxygen picks up the electrons that have completed
their circuit.
 The oxygen then combines with the ionized hydrogen
atoms (H+), and water (H2O) is formed as the waste
product which exits the fuel cell.

Hydrogen Fuel Cell
 The electrolyte plays an essential role as well.
 It only allows the appropriate ions to pass between the anode
and cathode.
 If other ions were allowed to flow between the anode and
cathode, the chemical reactions within the cell would be
disrupted.
 The reaction in a single fuel cell typically produces only about
0.7 volts.
 Therefore, fuel cells are usually stacked or connected in some
way to form a fuel cell system that can be used in cars,
generators, or other products that require power.
 The reactions involved in a fuel cell are as follows:
 Anode side (an oxidation reaction): 2H2=>4H+ + 4e-
 Cathode side (a reduction reaction): O2+4H++4e−=>2H2O
 Net reaction (the "redox" reaction): 2H2+O2=>2H2O

Geothermal Energy
 Geothermal energy originates from earth’s interior in the
form of heat.
 Volcanoes, geysers, hot springs and boiling mud pots are
visible evidence of the great reservoirs of heat that lies
within earth.
 Although the amount of thermal energy within the earth is
very large, useful geothermal energy is limited to certain
sites only, as it is not feasible to access and extract heat
from a very deep location.
 The sites where it is available near the surface and is
relatively more concentrated, its extraction and use may be
considered feasible.
 These sites are known as geothermal fields.

Geothermal Energy
 As per US Geological Survey, the entire heat content of the
earth’s crust up to a depth of 10 km above 15 °C is defined
as geothermal resource.
 As such the geothermal resource is estimated to be more
than 2.11 × 1025 J, which is equivalent to 109 MTOE
(million tons of oil equivalent).
 This is a huge amount of energy, enough to supply our
energy needs at current rates for 3,50,000 years.
 Thus it is considered an inexhaustible and renewable
source.
 However, it is a low-grade thermal energy form and its
economic recovery is not feasible everywhere on the
surface of the earth.

Advantages
Geothermal Energy
(i) it is a reliable and cheap source of energy
(ii) it is available 24 hours per day
(iii) its availability is independent of weather
(iv) it has inherent storage feature so no extra storage facility
required
(v) Geothermal plants require little land area
(vi) feasibility of modular approach represents lot of
opportunities for development of relatively quick, cost-
effective geothermal projects.

Disadvantages
Geothermal Energy
(i) It is site specific – there are not many places where you can build a
geothermal power station
(ii) Generally, energy is available as low grade heat
(iii) Continuous extraction of heated ground water may leads to
subsidence (setting or slumping) of land
(iv) Geothermal fluid also brings with it the dissolved gases and solute (as
high as 25 kg/m3) which leads to air and land pollution
(v) Drilling operation leads to noise pollution
(vi) The available thermal energy cannot be distributed easily over long
distances
(vii) Corrosive and abrasive geothermal fluid reduces the life of the plant.

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