Unit v geothermal energy ,renewable energy sources,ORO551

Geothermal energy
ORO551,annauniversity,ECE,PSNACET

syllabus
 Resources
 Types of wells
 Methods of harnessing the energy
 Potential in India
Ocean energy
 OTEC
 Principles utilization
 Setting of OTEC plants
 Thermodynamic cycles
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syllabus
Tidal and wave energy
 Potential and conversion techniques
 Mini hydal power plants and their economics
Direct energy conversion
 Need for DEC
 Carnot cycle
 Limitations
 Principles of DEC
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Resources
 Hydrothermal convective systems
1.Vapour dominated or dry steam fields
2.liquied dominated system or wet
steam fields
3.hot water fields
 Geo pressure resources
 Petro thermal or Hot dry rocks(HDR)
 Magma resources
 Volcanoes

Hydro thermal system
Water is heated by contact with the
hot rock
Vapour dominated system
The water is vaporized into the
steam (200 ^o C)
The pressure 7 kg/cm^3
Steam is the most suitable for use
in turbo electric power plants

Liquid dominated system
The hot water circulating and
trapped underground is at
temperature range of 175^0 to
315^0 Celsius

Geopressure systems
These resource occur in large, deep
sedimentary basins
The reservoiers contain moderately
high temperature water under high
pressure
Hot dry rocks (or) Petro thermal
system
These are very hot solid rocks
The temperature range 150 to 290^0
Celsius

Magma resources
Completely molten rock
Temperature range excess of
650^0 Celsius

The molten rock (magma)
Heat is conducted upward
Depth of wells range 600m to
2000m

Types of wells
 Production well
 Injection well
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Hydrothermal convective resources

Utilization of geothermal energy
 Heating water
 Electricity generation
 Air conditioning
 Green house heating

Hydrothermal convective region
MAGMA
SURFACE
PRODUCTION
WELL
INJECTION WELL
SOLID ROCK

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Hydrothermal convective resources
1.Vapour dominated
or
dry steam fields
2.liquied dominated system
or
wet steam fields
3.hot water fields

Vapour dominated system
Scheme of a vapour dominated power plant

Easily developed
Lowest cost
Least problems
Dry steam from the wells is
collected
Dry steam passed through the
turbine, which drives the electrical
generator

Vapour dominated system on T.S. diagram
Entropy ---
thermal energy for
conversion into
mechanical work

 1.The dry steam from the well 200^0 C
 2.Pressure drops through the well causes it to
slightly super heat at the well head
 3.The steam after expansion in the turbine
 4.Enters the condenser
 5.The mixture of the cooling water coming
from the cooling tower and turbine exhaust is
saturated vapour at this point
 6.That is pumped to the cooling tower.
 7.Disposal

Liquid dominated system-high temperature
1.The flashed steam system
2.The binary cycle system
3.Total flow system

The flashed steam system
Schematic of a liquid dominated single flash
steam system

 1.Water from the underground reservoir reaches
the well head
 2.Lower pressure
 3.Flash separators
 4.Dry saturated steam
 5. Saturated brine at 5 later reinjected to the
ground
 Brine means water strongly impregnated with
salt.

Double flashed steam system

Liquid dominated system-binary
cycle

Total flow concept

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Limitations of flashed steam system
Requires much larger total mass flow
rates through the well
There is a greater degree of ground
surface subsidence
Greater corrosion of piping ,well
casing, and other conduits
Many times temperature and pressure
of the water may not be sufficient to
produce the flash steam.

Hot dry rock resources or petro thermal
systems

Hot dry rock resources or petro thermal systems
 Composed of hot dry rock, no under ground water
 Moderate depth
 The thermal energy of HDR is extracted by
pumping water or other fluid
 More flexibility
 Many more studies are needed before
implementation

Geopressured resources
 High pressure of water up to 1350
atm.(137MPa) in the deepest layers
 Which reservoirs are referred to as
geopressured.
 "atm" in relation to pressures that are
relative
to mean atmospheric pressure at sea
level (1.013 bar).

 The mega pascal is a x 1000000 multiple of the
pascal unit which is the SI unit for pressure.
 1 mega pascal equals 1,000,000 pascals.
 Primarily used for higher range
pressure measurement due to its larger value
(e.g. 1 MPa = 10 bar).
 Mpa is to describe the pressure ranges and
ratings of hydraulic systems.

Geothermal potential in india
340 known thermal area in india
Each hot or warm springs
113 spring area discovered
46 high temperature type – which
could generate 1838MW
59 intermediate type (90 ^0 c to
150^0 c)
Roughly 10% of total power
production in india

Geothermal potential in india
State capacity
JAMMU AND KASHMIR
PUGA VALLEY 20 MW
KARNATAKA,BENGALORE,HAL 5 KW

Big questions
1.Explain the various geothermal resources
2.Dicuss about various types of hydro thermal systems
3.Explain the vapour dominated system
4.Discuss about the various types of liquid dominated
system
5.Short note the following
a. Geothermal potential in India
b.Geopressured resources
c.Petro thermal systems or HDR systems
d.Limitations of flashed steam system

OTEC
Principles utilization
Setting of OTEC plants
Thermo dynamic cycles

introduction
 The ocean can produce two types
of energy
 Thermal energy from the sun's heat,
and mechanical energy from the tides
and waves.
 Oceans cover more than 70% of Earth's
surface,
 Ocean is the world's largest solar
collectors.

Ocean thermal electric conversion(OTEC)
 The temperature gradient can be utilized in a
heat engine to generate power, this is called
ocean thermal electric conversion(OTEC)

Methods of Ocean thermal electric power generation
 1.Open cycle or Claude cycle
 2.Closed cycle or Anderson cycle

1.Open cycle or Claude cycle

 Sea water as the working fluid
 Low pressured steam passed through
the turbine
 Turbine extracts energy from the steam
 Vapour is cooled in the condenser
 Cooled water discharged into the ocean

 1.warm water 27^0 c,pressure of 0.03619kg/cm^2
 2.25^0 c,pressure 0.03213 kg/cm^2,mixture of water
and steam of very low quality
 3.low pressure,high specific volume

2.Closed cycle or Anderson cycle

 Heat exchanger is known as evaporaters
 Large volume of water is needed
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Big questions
 Discuss about the open cycle OTEC system
 Explain the anderson OTEC cycle
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Potential and conversion techniques
Mini hydal power plants and their economics

Tidal energy
 Tide is a periodic rise and fall of the water level of sea
 Action of the sun and moon on the water of the earth
 Renewable in nature

Principle of tidal power generation

Basic principle of tidal power

 Tides are produced mainly by the gravitational
attraction of the moon and the sun on the water
of the solid earth and the oceans
 A-High tide point
 B-Low tide point
 A to B – 6 hours
 B to C – 6 hours
 The difference between the high and low water
levels is called range of the tide.

Components of tidal power plants
 The power house
 The dam or barrage or basin
 Sluice ways from the basins to the sea and vice
versa

Operation methods of utilization of tidal energy

Operation methods of utilization of tidal energy
 Single basin arrangement
 Double basin arrangement

Single basin arrangement
 Single ebb cycle system
 Single tide cycle system
 Double cycle system

Single basin operation

Double basin operation

wave energy -advantages
 Naturally concentrated and transported
 It is free
 Renewable energy source
 Wave power devices are in small size
 Pollution free

Wave energy-disadvantages
 The energy available only in the ocean
 Extraction device must be operated in a marine
environment
 Complicated structure
 More Capital investment
 High maintenance cost
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Wave conversion devices
 Floats
 High level reservoir wave machine
 The dolphin type wave power machine

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Application
 Irrigation
 Lighting
 Educational purposes

Components of a hydroelectric
scheme
 Diversion and intake
 Desilting chamber
 Water conductor system
 Forebay /balancing reservoir
 Surge tank
 Penstock
 Power house
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Need for DEC
Carnot cycle
Limitations
Principles of DEC

Need for DEC
 A direct energy conversion device
converts one form of energy to another
through a single process.
 For example, a solar cell is a direct
energy conversion device that converts
optical electromagnetic radiation to
electricity.

 Direct energy conversion is a fascinating
topic because it does not fit neatly into a
single discipline.
 Energy conversion is fundamental to the
fields of electrical engineering,
 It is also fundamental to mechanical
engineering, physics, chemistry, and
other branches of science and
engineering.

PRINCIPLES OF DIRECT ENERGY CONVERSION PROCESS

Carnot cycle
 Sadi Carnot was a French physicist who proposed
an “ideal” cycle for a heat engine in 1824
 This would produce the best efficiency since
 η = 1 – (QL/QH).


V

Questions
 Discuss about the need for direct energy
conversion devices
 Discuss about the various principles of DEC
 Explain the Carnot cycle in engines
 What are the limitations of Carnot cycle ?
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unit v geothermal energy,ORO551,annauniversity,ECE,psnacet
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Unit v geothermal energy ,renewable energy sources,ORO551

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