Unit iv wind energy

UNIT IV
Wind Energy
syllabus
WIND ENERGY
 Sources and potentials
 Horizontal and vertical axis wind mills
 Performance characteristics
 Betz criteria
1/9/2020 1unit iv wind energy,ORO551, annauniversity

Syllabus(contd)
BIOMASS
 Principles of bio conversion
 Anaerobic/aerobic digestion
 Types of bio gas digesters
 Gas yield
 Combustion characteristics of bio gas
 Utilization for cooking
 I.C engine operation
 Economic aspects

Sources and potentials of wind
energy
 Wind energy is an indirect form of solar
energy
 One percentage of solar radiation is
converted into wind energy
 Wind resource potential in India is 34,043
MW for power generation according to
recent assessment.

Installed capacity as on march 2018
State Total capacity (MW)
TAMIL NADU 8197
GUJARATH 5613
MAHARASTRA 4784
KARNATAKA 4509
RAJASTHAN 4298
ANDHRA PRADESH 3963
MADHYA PRADESH 2520
TELENGANA 101
KERELA 53
OTHERS 04
TOTAL 34043

Sources and potentials of wind
energy(contd)
 Wind energy in india may be considered cost
effective alternative to conventional sources of
electrical power.

Wind turbines (OR) Wind mills
 Wind turbines are machines that generate electricity
from the kinetic energy of the wind.
 Today, turbines can be used to generate large amounts
of electrical energy in wind farms both onshore and
offshore

Factors involved in site selection
for wind mills
 The availability of wind with sufficient kinetic
energy
 The magnitude of wind velocity should be high
 The wind availability should be throughout the
year
 The site should be free from obstacles
 Availability of vast open land at a lower land cost
 The construction materials should be available
and cheaper

Factors involved in site
selection for wind mills(contd)
 Availability of skilled workers
 Away from the populated places but not away
from load centre.
 No possibility of storms, floods, earthquakes,
volcanoes, etc.

Advantages of wind mills
 Free of energy cost,
 No pollution,
 No water required,
 low operating costs etc

Disadvantages of wind mills
 Fluctuation in wind speed,
 occupies more land,
 Noisy

Types of wind mills
BASED ON NO. OF ROTOR BLADES:
 Single blade
 Multi-blade rotors
BASED ON AXIS OF ROTATION :
 Horizontal Axis wind mills (or) turbine (HAWT)
 Vertical Axis wind mills (or) turbine (VAWT)

Horizontal axis wind turbine

Parts of wind turbine

 More popular
 The axis of the rotor's rotation is parallel to the wind
stream and the ground.
 Most HAWTs today are two- or three-bladed,
though some may have fewer or more blades.

There are two kinds of Horizontal Axis Wind Turbines:
1. Upwind wind turbine
2. Downwind wind turbine.

Advantages of Horizontal axis wind
turbine
 Higher stability
 The turbine collects the maximum amount of wind
energy
 The ability to pitch the rotor blades in a storm so that
damage is minimized
 The tall tower allows the access to stronger wind
 Self-starting
 Cheaper because of higher production volume

Disadvantages of Horizontal
axis wind turbine
 It has difficulties operating near the ground
 The tall towers and long blades
 Hard to transport from one place to another
 They need a special installation procedure
 They can cause a navigation problem when placed
offshore

Vertical axis wind turbine

 The vertical axis wind turbine is an old technology,
dating back to almost 4,000 years ago.
 The rotor of the VAWT rotates vertically around its
axis
 This is not as efficient as a HAWT,

 This does offer benefits in low wind situations wherein
HAWTs have a hard time operating.
 It tends to be easier and safer to build,
 This can be mounted close to the ground and handle
turbulence better than the HAWT.
 its maximum efficiency is only 30%,

Types of vertical axis wind turbine
 Darrieus Turbine
 Giromill Turbine
 Savonius Turbine

Comparison between HAWT and
VAWT
HAWT VAWT
Higher cost Lower cost
Less noisy More noisy
More power from wind Less power from wind
Technology fully developed Technology under developed
More efficient Less efficient
Smooth output Fluctuating output
Low starting torque High starting torque
Operates moderate wind speed Operates even in low wind speeds

Terms Used In Wind Energy
1.Wind speed:
The speed at which the wind is flowing.
2. Cut-in speed:
The minimum speed of turbine at which the
turbine starts developing power. e.g. 5 m/s
3. Cut-off (Furling) speed:
The maximum speed of turbine at which the
turbine stops developing power. e.g. 30 m/s .Its for
safe operation of wind turbine.

4. Power of wind,
P = 0.5 ρ A V3.
Where A – Swept area of rotors,
V-Velocity of wind ,
ρ– Density of air

5. Betz’ limit or law:
The theoretical maximum possible power can be
extracted from the wind energy.
Its value is 59.3% of power available in the wind.

6. Power co-efficient
Power co-efficient is the ratio of power output of
the turbine to the power available in the wind.
Power co-efficient = Power output of the
turbine/power available in
the wind

Performance characteristics

Performance
characteristics(contd.,)
 The ideal efficiency of 59.3% is based on Betz’s
limit.
 The single rotor, Darrius rotor, multi-blade rotors
etc are given in the graph
 The range of speed ratio with the power co-eff is
compared.
 The three blade rotor machine performs better in
the speed ratio as well as power developed.

Performance
characteristics(contd.,)
 The Savonius rotor works at lower speed ratio but
the power co-efficient is also very low.

Factors Affecting Performance of wind
turbine
various factors such as
1. location,
2. geographical factors,
3. mechanics,
4. rotor shape/ size, etc
Output can be regulated by
1. constant or variable rotational speed,
2. adjustable and non-adjustable blades.

Power equation and Betz criteria

Power equation and Betz criteria(contd.,)

 A German physicist Albert Betz
concluded in 1919 that no wind turbine
can convert more than 16/27 (59.3%) of
the kinetic energy of the wind into
mechanical energy turning a rotor.
 This is known as the Betz Limit or Betz'
Law.

BIOMASS
 Principles of bio conversion
 Anaerobic/aerobic digestion
 Types of bio gas digesters
 Gas yield
 Combustion characteristics of bio gas
 Utilization for cooking
 I.C engine operation
 Economic aspects

Introduction
Bioenergy is the general term for
energy derived from materials such as
wood, straw or animal wastes
Bioenergy can be converted into the
following
1.biofuels
2.charcoal
3.biodiesel
1/9/2020 unit iv wind energy,ORO551, annauniversity 46

Bioenergy cycle

Carbon cycle

Biomass sources

Biomass sources
 Tropical crops wastes
1.Bagasse
2.Rise husks
 Animal wastes
1.Animal manure
2.Sewage sludge
3.Poultry litter
 Municipal solid waste

Principles of bio conversion

Thermo-chemical conversion
Energy is produces by applying heat and chemical
processes.
1. Combustion process
2. Pyrolysis Process
3. Gasification process
4. Liquefaction process

Combustion process

Combustion process(contd,.)
 Combustion is an exothermic chemical reaction,
in which biomass is burned in the presence of air.
 The chemical energy which is stored in the
biomass is converted in the mechanical and
electrical energies.

Pyrolysis Process

Pyrolysis Process( contd,.)
It is the process of conversion of
biomass to liquid (bio-oil), solid
(charcoal) and gaseous (fuel gases)
products by heating in the absence
of air at 500 °C.

Gasification process
In biomass gasification, charcoal,
wood chips, energy crops, forestry
residues, agricultural waste and
other wastes are transformed into
flammable gases at high
temperature (800-1000°C).

The Fischer–Tropsch reactor
process is a collection of chemical
reactions that converts a mixture
of CO and H2 into
liquid Hydrocarbons

Liquefaction process
It is the process in which
biomass is converted into liquid
phase at low temperatures (250-
350 °C) and high pressures (100-
200 bar).

Liquefaction process(contd,.)

Liquefaction process(contd,.)
Fermentation is a
metabolic process that produces
chemical changes in organic
substrates through the action of
enzymes

Bio-Chemical conversion
 Biochemical conversion makes use of
the enzymes of bacteria and other living
organisms to break down biomass and
convert it into fuels.
1.Anaerobic digestion process
2. fermentation

Anaerobic digestion process

 This is a process in which organic
material directly converted to a gas
which is termed as biogas.
 It is mixture of methane, carbon dioxide
and other gases like hydrogen sulphide
in small quantities.

 Biomass is converted in anaerobic
environment by bacteria,
 which produces a gas having an energy
of 20-40% of lower heating value of the
feedstock.

Fermentation process

 Fermentation is an anaerobic process
that breaks down the glucose within
organic materials.
 It is a series of chemical reactions that
convert sugars to ethanol.

 The basic fermentation process involves
the conversion of a plant’s glucose (or
carbohydrate) into an alcohol or acid.

Biogas
 The biogas is used for cooking, domestic
lighting and heating, run I.C. Engines
and generation of electricity for use in
agriculture and rural industry.
 Family biogas plants usually of 2-3 m^3
capacity.

Biogas
 Biogas contains
 55-65% methane,
 30-40% carbon dioxide
 The rest being H2,H2S and some N2
 Biogas can be produced from the
decomposition of animal, plant and human
waste.

Raw materials
 Cow dung
 Sewage
 Crop residues
 Vegetable wastes
 Water hyacinth
 Poultry droppings
 Pig manure

Advantages
 The initial investment is low for the
construction of biogas plant.
 The technology is very suitable for rural areas.
 Biogas is locally generated and can be easily
distributed for domestic use.
 Biogas reduces the rural poor from
dependence on traditional fuel sources, which
lead to deforestation

Advantages
 The use of biogas in village helps in improving
the sanitary condition and checks
environmental pollution.
 The by-products like nitrogen rich manure
can be used with advantage.
 Biogas reduces the drudgery of women and
lowers incidence of eye and lung diseases

Biogas generation
 Digestion is biological process that occurs in
the absence of oxygen and in the presence of
anaerobic organisms at temperatures (35-70ºc)
and atmospheric pressure.
 The container in which, this process takes
place is known as digester.

Biogas generation
 Most organic materials undergo a natural
anaerobic digestion in the presence of moisture
and absence of oxygen and produce biogas.
 The biogas so obtained is a mixture of methane
(CH4): 55-65% and Carbon dioxide (CO2): 30-40%.

Anaerobic digestion:
 The treatment of any slurry or sludge
containing a large amount of organic
matter utilizing bacteria and other
organisms under anaerobic condition is
commonly referred as anaerobic
digestion or digestion.

Anaerobic digestion(phases)
The three stages are
(i). The enzymatic hydrolysis,
(ii). Acid formation and
(iii). Methane formation.

The enzymatic hydrolysis
Where the fats, starches and proteins contained
in cellulosic biomass are broken down into simple
compounds

Acid formation
 The micro organisms of facultative and anaerobic
group collectively called as acid farmers,hydrolyse
and ferment, are broken to simple compounds
into acids

Methane formation
 Where organic acids are converted into
methane(CH4) and carbon dioxide(CO2).
(C6H10O5)n + nH2O ==== 3nCO2+3nCH4

Advantages of anaerobic digestion
1.Calorific value of gas
2.New sludge production
3.Stable sludge
4.Low running cost
5.Low odour
6.Stability
7.Value of sludge

Classification of biogas plants
1. Continuous and batch types
2. The dome and drum types
3. Different variations in the drum type

Continuous and batch types

Types of biogas plants(digesters)

Utilization of biogas
1. House hold cooking
2. Lighting
3. Operating small engines
4. Utilizing power for pumping water
5. Grinding flour

IC ENGINE OPERATION USING BIOGAS

Utilization for cooking
BIOGAS PRETREATMENT
GASSIFICATION
COOKING

Unit iv wind energy

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