Advanced energy engineering Module 5

1. ME403
Advanced Energy Engineering
Prepared by:
Dr. Rejeesh C R, Associate Professor,
Dept. of Mechanical Engineering
Federal Institute of Science and Technology
L-T-P-C
3-0-0-3
Module V
https://sites.google.com/site/rejeeshcrfisat

2. 2

3. Course Outcomes
3
Sl.
NO
DESCRIPTION
PO
MAPPING
1
Compare and contrast different types of layouts and working principles of steam,
hydro, nuclear, gas turbine and diesel power plants.
PO1
2
Understand the importance of solar energy and identify different components of
a solar power plant.
PO1
3
Understand the importance of wind energy and identify different types of wind
turbines and their components.
PO1
4
Understand the concept of power generation from biomass energy resources and
their future prospects and economics.
PO1
5
Understand the principle of power generation from various sources and
Hydrogen energy conversion systems.
PO1
6
Understand the renewable energy scenario, environmental effects of energy
conversion and choose sustainable energy for future.
PO1
After successful completion of this course, students will be able to

4. 4

5. What is Geothermal Energy?
• Geothermal energy is defined as heat from the Earth. It is a
clean, renewable resource that provides energy around the
world.
• It is considered a renewable resource because the heat
emanating from the interior of the Earth is essentially limitless.
• Geothermal is a natural form of nuclear power, as it originates
from radioactive decay.
5

6. Harnessing Geothermal
• Geothermal power emits from earth at a rate of 44 x 1012 W. This is
more than double the total power consumption of the world.
• The Earth’s crust acts as a massive insulating “blanket” that traps this
heat deep under the surface. Thus, the crust must be pierced to
release this heat.
• Unfortunately, this power is too spread out to effectively use it all.
• The distribution of geothermal energy, however, is not uniform.
Certain regions have an enormous geothermal resource
• Where the crust is thin or fractured, as at the edges of tectonic plates,
volcanoes, geysers and hot springs deliver this energy to the surface.
6

7. Crust
Upper Mantle
Mantle
Outer Core
Inner
Core
600oC
1200oC
4000oC
5000oC
Geothermal energy originates from the Earth’s core, which is estimated to
have a temperature of about 5000°C. This nearly constant temperature is
possible because of continuous radioactive decay, compression, and
because the core is very well insulated.
Origin of Geothermal Power
7

8. Geothermal Sources
 Hydro thermal
 Vapor dominated systems
 Liquid dominated systems
 Hot water fields
 Geopressured
 Hot dry rock or petrothermal
 Magma resources
 Volcanoes
8

9. Geothermal Sources
• Hot Water Reservoirs
– Heated underground water pools, very large in magnitude in the U.S.; not
appropriate for electricity but can be useful for space heating
• Natural Steam Reservoirs*
– e.g. The Geysers power plant (California). Highly desirable type of
resource for direct generation of electric, though very rare
• Geopressured Reservoirs*
– Hot, superheated brine solution saturated with natural gas. Useful for
both its heat content and natural gas
• Hot Dry Rock
– Hot rock can be used to heat a working fluid is forced through a series of
man-made channels and cycled. No technology yet exists to do this
• Hot Molten Rock (Lava)
– No technology yet exists to extract heat energy from lava
9

10. Estimated U.S. Geothermal Resources
Resource Type
Total Resource
(QBtu)
Potentially Usable
Resource (QBtu)
Hot Water 12,000 6,000
Natural Steam 180 45
Geopressurized 73,000 2,400
Hot Rock 1,410,000 14,100
Lava 3,500 35
* The U.S. consumes 98 QBtu of energy per year
10

11. Geothermal Energy in India
11

12. Geothermal Energy in India
• Geothermal provinces are estimated to produce 10,600 MW of
power (experts are confident only to the extent of 100 MW)
• Geothermal provinces in India: the Himalayas, Sohana, West
coast, Cambay, Son-Narmada-Tapi , Godavari, and Mahanadi.
• Reykjavík Geothermal will assist Thermax to set up a pilot
project in Puga Valley, Ladakh (Jammu & Kashmir).
• First operational commercial geothermal power plant is likely
to come up in AP with a capacity of 25 MW by Geosyndicate
Pvt Ltd.
12

13. Geothermal Power Plants
• There are three types of geothermal power plants
– Direct Dry Steam Plants
– Flash Cycle Plants
– Binary Closed Cycle Plants
13

14. Direct Dry Steam Power Plant
14

15. Direct Dry Steam Power Plant
• The oldest type of Geothermal power plant used.
• Geothermal reservoir containing pure steam is
required.
• Pure dry steam drives turbine.
• Very rare type of geothermal power plant.
• Operating at California, Italy, and Japan.
15

16. Dry Steam Power Plant
16

17. The Geysers (California)
17

18. Flash Cycle Plants
Uses superheated brine. When the brine enters a low pressure
chamber called a flash tank, it instantly vaporizes (flashes).
18

19. Flash Cycle Plants
• Commonly used geothermal power plant.
• Geothermal reservoirs containing both hot water & steam
is required.
• Pressure changing system is required.
• Operating at Hawaii, Nevada, Utah & some other places
19

20. Flash Cycle Plants
20

21. Binary Closed Cycle Plants
Binary closed cycle plants use a working fluid (i.e. Freon-12) to spin
a turbine. The working fluid cycles through a heat exchanger where
it is evaporated by hot water from a geothermal reservoir.
evaporator
condenser
hot
water
flow
direction
working
fluid
Cold
water
pump
21

22. Binary Closed Cycle Plants
• Does not use steam directly to spin turbines.
• Only the heat of the underground water is used.
• Vapourized hydrocarbons are used to spin the turbine.
• Hydrocarbons having lower boiling point such as isopentane,
isobutane and propane can be used.
• No harmful gas is emitted to the atmosphere because the
underground water is never disclosed to outside.
• This’s the worldwide accepted power plant.
22

23. Binary Closed Cycle Plants
• Binary cycle plants are the most useful because it is not
necessary for the water to reach the extreme temperatures
that are experienced with dry steam and flash plants.
– The water in a binary cycle plants needs only to be above
the boiling temperature of the working fluid
• Considering that most geothermal water is of moderate
temperature (> 400oF), these are the most useful and most
viable types of geothermal plants.
23

24. Binary Closed Cycle Turbine At Chena Power Plant
in Alaska
24

25. Binary Closed Cycle Plants
25

26. Advantages of Geothermal
• Geothermal energy is a renewable energy source with virtually
limitless supply.
• Geothermal energy is relatively clean (Produces 12% of GHG emission
of fossil fuel plants)
• Geothermal energy can be used for cooling and heating homes.
• Not subject to the same fluctuations as solar or wind
• Smallest land footprint of any major power source
• Inherently simple and reliable and could be built underground.
• Can provide base load or peak power
• Already cost competitive in some areas (~$0.07 per kWh)
• Massive potential for the utilization of untapped sources
• New technologies show promise to utilize lower water temperatures.
26

27. Disadvantages of Geothermal
• High upfront costs associated with exploration and drilling
• Finite lifetime of useful energy production
– Continuous drop in thermal output overtime
– Once the thermal energy of a well is tapped, it requires a
“recharging” period that can take several years.
• Very location specific (e.g. Iceland)
• There are significant volumes of greenhouse gases and toxic
compounds such as hydrogen sulfide that are released when
geothermal reservoirs are tapped
– Foul smelling gases
– Pumps used to circulate working fluid consume fossil fuel
• Earthquakes induced by fracking.
27

28. What is tidal energy?
• Tidal power, sometimes called tidal energy, is a form of
hydropower that exploits the movement of water caused by
tidal currents or the rise and fall in sea levels due to the tides.
• Although not yet widely used, tidal power has potential for
future electricity generation and is more predictable than wind
energy and solar power.
28

29. History of Tidal
• Tidal energy is one of the oldest forms of energy used by
humans.
• Dating back to 787 A.D., tide mills were constructed, consisting
of a storage pond and a sluice (gate that controls water flow).
– During the incoming tide (flood), the sluice would open to
allow rising waters to fill the storage pond
– During the outgoing tide (ebb), the stored water would be
released over a waterwheel
• In the early 1960’s, the 1st commercial scale tidal power plant
with twenty four 10MW turbines was built in St. Malo, France.
29

30. What Causes Tides?
• http://www.pbs.org/wgbh/nova/earth/what-causes-the-tides.html
30

31. Principle of tide generation
• Tidal energy is a form of hydropower that converts the
differential head due to tides into useful energy.
• Only form of energy whose source is moon.
• Tides are produced by gravitational attraction of moon and
sun on the water of earth.
• 2 high tides and 2 low tides occur in a lunar day.
• Time delay between successive tides is 6hrs.
32

32. Range of a tide
Range is the difference between high and low water levels
denoted by R.
R = Elevation at high tide - Elevation at low tide
The range of tides varies from 4.5 m to 12.4 m.
33

33. high tide
low tide
34

34. What is tidal energy?
• Tidal power facilities harness the energy from the rise and fall
of tides.
• Two types of tidal plant facilities.
– Tidal barrages
– Tidal current turbines
• Tides are the rising and falling of Earth's ocean surface caused
by the tidal forces of the Moon and the Sun acting on the
oceans.
• The tidal force is the vectorial difference between the
gravitational force of the Earth and the gravitational force of
the Moon.
35

35. Tidal Barrages
• The ocean’s tides can be used to accumulate potential energy, which
can be converted to mechanical energy by turning a turbine in a
manner quite similar to hydropower.
• As the tides rise and fall daily, basins along the shoreline naturally fill
and empty. A complete tidal cycle takes 12.5 hours, so there are two
high tides and two low tides a day.
• Dam-like structures called barrages can be built across the mouths of
natural tidal basins with sluice gates. Water can be allowed to rise on
one side of the sluice until enough of a hydraulic head is built up to
power a turbine.
• The turbines are designed to work in either direction to maximize the
utilization of the changing tide.
36

36. Tidal Barrages
Barrages make use of the potential energy from the difference in
height (or head) between high and low tides. Barrages suffer from
the problems of very high civil infrastructure costs, few viable sites
globally and environmental issues.
37

37. 38

38. Rance River Tidal Power Station
• The first commercial tidal power
plant in the world is the La Rance
Tidal Barrage in France built in 1967.
• The average tidal range is 28 ft, with
a max of 44 ft. The barrage extends
2500 ft across.
• Produces 5.4 GWh of electricity per
year, which is only 18% of the
available energy in the basin.
39

39. Tidal stream systems make use of the kinetic energy from the
moving water currents to power turbines, in a similar way to wind
mills use moving air. This method is gaining in popularity because
of the lower cost and lower ecological impact.
Tidal current turbines
40

40. Tidal Turbines
• Efforts are underway to anchor turbines to the ocean floor to
harness tidal energy. This concept is proven, and in practice in a
handful of locations on a small scale.
• This form of generation has many advantages over its other tidal
energy rivals. Turbines are submerged in water and are therefore
out of sight. They don’t pose a problem for navigation and
shipping and require the use of much less material in
construction.
• Tidal turbines are vastly better than wind turbines in terms of
efficiency. A tidal turbine produces 4 times the power output per
square meter of sweep area as a wind turbine, with a
substantially smaller environmental impact.
41

41. 42

42. 43

43. Siemens “SeaGen (S)” Tidal Turbine
44

44. Advantages
• Renewable and clean
• Tides are predictable
• There is a vast potential for energy generation
• With tidal turbines, the structures are out of sight
• Less required material for tidal turbines than wind
45

45. Disadvantages
• Like wind and solar, tidal power is intermittent
– In addition, the hydraulic head obtained from tides is also variable
• Tides do not align with peak energy demand times
• With regard to barrages, some of the environmental impacts of
dams are present with this technology as well, though to a much
lower extent
• VERY, VERY, VERY EXPENSIVE
– Only produces 1/3 of the electricity that a hydropower plant of
equal size would produce
– Wave power sites produce low energy output
46

46. Classification of tidal power plants
Tidal power plants are classified on the basis of number of basin
used for the power generation.
They are further subdivided as one way or two way system as per
the cycle of operation for power generation.
Various types of tidal power plants are as follows:
1. Single basin, single effect tidal power plant
2. Single basin, double effect tidal power plant
3. Double basin tidal power plant
47

47. single basin one way tidal power
plant
In this plant a basin is allowed to get filled during the flood tide.
during the ebb tide, water flows from the basin to the sea through
the turbine and generates power.
The power is available for a short duration during ebb tide.
48

48. Single basin, double effect tidal
power plant
In single basin two way tidal power plant the power is generated
both during flood tide as well as ebb tide.
The direction of flow through the turbines during the ebb and flood
tides alternates but machine acts as a turbine for either direction
of flow.
49

49. Single basin, double effect tidal plant
• A two flow( reverse flow) low head turbine housed along with the generator is
installed in the dam structure.
• Electric generator and a number of turbine components are enclosed in a
water tight bulb. Turbine is kept submerged in water.
• During the high tide period the water level in the sea is higher than the water
level in the tidal basin. Hence the water flows from sea into the tidal basin
through the water turbine, as the level of water in the sea is more than the
level in the tidal basin. The generator connected with the turbine produces
electricity.
• During the low tide period the water flows from tidal basin to the sea through
the turbine as the level of water in the tidal basin is higher than the level of
water in the sea. The generator coupled with the turbine generates electricity.
• The generation of power stops when the level of water in the sea and tidal
basin are equal.
• In Kerala, tidal system at Vizhinjam is an example.
50

50. Double basin plant
In this plant one basin is intermittently filled by flood tide and
other is intermittently drained by ebb tide.
51

51. Double basin plant
Figure shows a double basin one way tidal power plant. In this plant
one basin is intermittently filled by flood tide and other is
intermittently drained by ebb tide.
52

52. Ocean Thermal Energy Conversion
(OTEC)
• The world’s oceans constitute a vast natural reservoir for
receiving and storing heat energy from the sun.
• Nearly 75% of the surface area of Earth is water. Due to the high
heat capacity of water, the water near the surface is maintained
at significant higher temperatures than water at greater depth.
• It is possible to extract energy from the oceans through the use
of heat engines in order to exploit the temperature differences
between warm surface water and the cold, deep water.
53

53. Closed-Cycle OTEC System
• Closed-cycle systems have been considered for OTEC.
– In such a system, a low heat capacity working fluid passes
through a heat exchanger (evaporator) which
– The vapor passes through an expansion valve and forces the
rotation of a turbine
– Cold water from the depths cools the condenses the
working fluid via heat exchanger, and the process repeats.
54

54. Ocean Thermal Energy Conversion
Solar heating of upper layer of ocean water combined with earth's rotation
produces large convection currents while the deep water remains relatively cold.
These temperature difference could be used to generate electrical energy. 55

55. Ocean Thermal Energy
• Earlier OTEC systems had an overall efficiency of only 1-3% (theoretical max.
efficiency lies between 6-7%), however newer designs operate closer to the
theoretical maximum efficiency.
• Based on closed Rankine cycle with ammonia as the working fluid. Relies on
temperature difference between deep sea water (7°C) and water surface (28°C).
• It consists of a vaporizer, turbine generator, condenser and pump. A low boiling
point liquid (ammonia/R134a), is fed to the vaporizer as working fluid. The upper
layers of ocean water heated by solar energy flows through the vaporizer.
• As a result, ammonia evaporates and flows to the turbine at high pressure and
propels it. Later, the low pressure exit ammonia vapour passes through a
condenser and is condensed to liquid ammonia.
• A large dia. intake pipe, submerged in the ocean for a depth of 1 kilometre or
more, brings cold water to the condenser. liquid ammonia is then pumped back
to the evaporator and the cycle repeats thereafter.
• In India, a floating 1 MW plant is commissioned at south east of Tuticorin, where
an ocean depth of 1200m is available from 40 km off the main land.
56

56. Ocean Thermal Energy
Advantages:
• It is steady and can be operated continuously.
• No waste products are involved.
• It has simple assembly and fewer accessories.
Disadvantages:
• Installation, maintenance and power transmission costs
are high.
• Low overall efficiency.
• High pumping costs.
57

57. 58
Ocean Thermal Energy

58. 59
Ocean Thermal Energy

59. Wave Energy
Where does wave energy originate?
– Differential warming of the earth causes pressure differences in the
atmosphere, which generate winds.
– As winds move across the surface of open bodies of water, they
transfer some of their energy to the water and create waves
The amount of energy transferred and the size of the resulting
wave depend on
– the wind speed
– the length of time for which the wind blows
– the distance over which the wind blows, or fetch
Therefore, coasts that have exposure to prevailing wind direction that face
vast expanses of open ocean have the greatest wave energy levels.
60

60. What is Wave Energy?
• Some of the kinetic (motional) energy in the wind is
transformed into waves once the wind hits the ocean
surface.
• Wind energy ultimately forms due to solar energy and its
influence on high and low pressure.
• The density of the energy that is transported under the
waves under the ocean surface is about five times higher
compared to the wind energy 20 meter (about 65 feet)
above.
• In other words, the amount of energy in a single wave is
very high.
61

61. Wave Energy Technologies
• Waves retain energy differently depending on water depth
– Lose energy slowly in deep water
– Lose energy quickly as water becomes shallower because of
friction between the moving water particles and the sea bed
• In order to extract this energy, wave energy conversion devices
must create a system of reacting forces, in which two or more
bodies move relative to each other, while at least one body
interacts with the waves.
• Wave energy conversion devices are designed for optimal
operation at a particular depth range.
62

62. Classification of wave power plants
Depending on the location
 Off shore or deep water
 Shoreline plants
Depending on the position w.r.t sea level
 Floating
 submerged
 partly submerged
Depending on the actuating motion used in capturing wave
power.
 Heaving float type
 Oscillating water column type
 Surge devices
63

63. Wave Energy Technologies
Therefore, devices can be characterized in terms of their placement
or location.
– At the shoreline
– Near the shoreline
– Off-shore
 The availability of wave power at deep ocean sites is 3-8 times that of
adjacent coastal sites. However the cost of construction, operation and
transmission is large.
 Shore line devices are relatively easier to maintain and install.
 One wave energy conversion system that has proven successful at each
of these locations is the OSCILLATING WATER COLUMN.
64

64. On-shore technologies
Advantages
• Easier to access for construction
and maintenance
• Less installment costs and grid
connection charges
• Could be incorporated into
harbor walls or water breaks,
performing a dual service for the
community.
Disadvantages
• Limited number of suitable
sites/high competition for use of
the shoreline
• Environmental concerns for on-
shore devices may be greater
• Much less energy available to on-
shore devices because water
depth usually decreases closer to
the shore
On-shore versus Off-shore
In spite of the success of this technology in an on-shore application, most
wave energy experts agree that off-shore or near-shore devices offer
greater potential than shoreline devices.
65

65. Classification of wave power plants
Depending on the position w.r.t sea level
 Floating
 submerged
 partly submerged
66

66. Advanced types of wave power
67

67. Classification of wave power plants
Depending on the actuating motion used in capturing wave
power.
 Heaving float type
 Oscillating water column type
 Surge devices
68

68. Heaving float or buoy systems
69
It utilizes a large float/buoy placed on ocean’s water surface that
rise and fall with the waves.
The resulting vertical motion is used to operate the piston of an air
pump through linkage.
The pump may be anchored or moored to the sea bed.
Several float operated air pumps
are used to store energy in a
compressed air storage.
The compressed air is used to
generate electricity through an air
turbine coupled to a generator.

69. Surge devices
70
When a moving wave is constricted,
a surge is produced raising its
amplitude. Such a device is known
as tapered channel device.
It comprises of a gradually
narrowing channel with wall heights
typically 3m to 5m above sea level.
The waves enter from the wide end of the channel, and as they
propagate towards narrower region, the wave heights get
amplified and spill over the walls to a reservoir which provides a
stable water supply to a low head turbine. This can be
implemented successfully at low tide sites only.

70. Oscillating water column device
71
It comprises of a partly submerged concrete or steel structure which has an
opening to the sea below the water line, thereby enclosing a column of air
above a column of water.
The column fills with water as the wave rises and empties as it descends. In the
process, air inside the column is alternately compresses and de-pressurizes the
air column. The air is then allowed to flow through a turbine, which drives the
generator.
The axial flow Wells turbine, invented in
the 1970’s, is the best known turbine for
this kind of application.
A 150 kW prototype OWC with harbor
walls was built onto the breakwater of
the Vizhinjam Fisheries harbour, near
Thiruvananthapuram in India. But this
project is not operational at present.

71. Principle of OWC Wave Energy
• In this simple example the
wave rises into a chamber.
The rising water forces the air
out of the chamber. The
moving air spins a turbine
which can turn a generator.
• When the wave drops, this
creates a vacuum in the
chamber, causing air to flow
in the opposite direction
• The kinetic energy of moving waves can be used to power a
turbine.
72

72. Oscillating Water Column
An Oscillating Water Column (OWC) consists of a partially
submerged structure that opens to the ocean below the water
surface. This structure is called a wave collector.
This design creates a water column in the central chamber of the
collector, with a volume of air trapped above it.
The type of turbine used is a key element to the conversion
efficiency of an OWC.
Traditional turbines function by gas or liquid flowing in one
direction and at a constant velocity.
When the flow is not always from the same direction or at a
constant velocity – such as in the OWC – traditional turbines
become ineffective.
73

73. Oscillating Water Column
• As a wave enters the collector,
the surface of the water
column rises and compresses
the volume of air above it.
• The compressed air is forced
into an aperture at the top of
the chamber, moving past a
turbine.
• As the wave retreats, the air is
drawn back through the
turbine due to the reduced
pressure in the chamber.
74

74.  In 1940, Bela Karlovitz received the 1st patent in Magneto
hydrodynamic generation.
 The Magneto hydrodynamic (MHD) generator is a device that converts
thermal energy of a fuel into electrical energy.
 The word magneto hydro dynamics (MHD) is derived from magneto-
meaning magnetic field, and hydro-meaning liquid, and -dynamics
meaning movement.
 Hannes Alfvén worked a lot on MHD generation, for which he received
the Nobel Prize in Physics in 1970.
 Magneto hydrodynamics (MHD) is the academic discipline which
studies the dynamics of electrically conducting fluids. Examples of
such fluids include plasmas, liquid metals, and salt water.
MHD Power Generation
Introduction
75

75. MHD Power Generation
• An MHD generator is a magnetohydrodynamic converter that
transforms thermal energy and kinetic energy into electricity.
• MHD generators are different from traditional electric generators in that
they operate at high temperatures without moving parts.
• The hot exhaust gas of an MHD generator can heat the boilers of a
steam power plant, increasing overall efficiency.
• MHD was developed as a topping cycle to increase the efficiency of
electric generation, especially when burning coal or natural gas.
• An MHD generator, like a conventional generator, relies on moving a
conductor through a magnetic field to generate electric current.
• It uses hot conductive ionized gas (a plasma) as the moving conductor.
The mechanical dynamo, in contrast, uses the motion of mechanical
devices to accomplish this.
76

76.  In MHD generator, the solid conductors are replaced by a
gaseous conductor, an ionized gas.
 If such a gas is passed at a high velocity through a powerful
magnetic field, a current is generated and can be extracted by
placing electrodes in suitable position in the stream.
 Follows Faraday’s principle. “An electric conductor moving
through a magnetic field induces electric field and current.”
PRINCIPLE OF MHD POWER GENERATION
77

77. Continue….
78

78. Construction
S
N
combustion
Chamber V
Ionized Gas
Working
fluid
Water cooler Thermal resistance sealing
Magnet
Stream
out
Load
output
Nozzle
Electrode
Inlet
79

79.  MHD generator consist of a combustion chamber and generator
chamber.
 The fluid conductor is passed into the combustion chamber
where they are ionized at very high temperature.
 There is a nozzle through which the ionized gas pass into the
generator chamber.
 The generator chamber consist of powerful magnet and a
number of oppositely located electrode pair inserted in the
channel to conduct the electrical current generated to an
external load.
 Both combustion and generator chambers are surrounded by a
heat resistance material and water cooler.
Continue….
80

80.  The gaseous (fluid) conductor is passed into the combustion
chamber through inlet.
 By using a fuel like oil (or) natural gas (or) coal, the fluid
conductor is heated to a plasma state and hence it is ionized.
 The temperature in the combustion chamber is around 2000°K
to 2400°K.
 The heat generated in the combustion chamber removes the
outermost electrons in the fluid conductor.
 Therefore, the gas particle acquires the charge.
Working
81

81.  The charged gas particles with high velocity enters into the
generator chamber via nozzle.
 The positive and negative charge moves to corresponding
electrodes and constitute the current.
 The direction of current is perpendicular to both the direction
of moving gas particle and to the magnetic field.
 The electrodes are connected to an external circuit to get a
load output.
 The current produced in the MHD generator are direct current
(DC).
 This DC current can be converted into alternative current (AC)
using an inverter attached with the external circuit.
Continue…
82

82. Open cycle MHD system
83

83. Open cycle MHD system
84

84. Closed cycle MHD system
85

85. Closed cycle MHD system
86

86.  The on and off time is about second.
 There are no moving parts, it is very reliable to use.
 The MHD generator has high thermal efficiency
 It is a direct conversion device.
 They have a better fuel utilization
 It can produce large amount of power
 The size of the plant is small
Advantages
87

87. They need high pure superconductor.
Working temperature is very high as about 2000°K to
2400°K.
The loss of power if very high
The components get high corrosion due to high
working temperature.
Disadvantages
88

88.  The MHD generators are used to power submarines
and aircrafts.
 Electrical power production for domestic applications
 They are used in rocket for space application
 They can be used as power plants in industry and
uninterrupted power supply system
Application
89

89. Fuel cell
• A fuel cell is an electrochemical device that produces electricity
without combustion by combining hydrogen and oxygen to
produce water and heat.
• Discovered by German Scientist C F Shoenbein.
• First developed by William Grove
• In 1839, Grove was experimenting on electrolysis (the process by
which water is split into hydrogen and oxygen by an electric
current), when he observed that combining the same elements
could also produce an electric current.
90

90. Advantages over conventional
energy sources
• They produce zero or very low emissions, especially Green
House Gases (GHGs) depending on the fuel used.
• Have few moving parts and thus require minimal maintenance,
reducing life cycle costs of energy production.
• Modular in design, offering flexibility in size and efficiencies in
manufacturing can be utilized for combined heat and power
purposes, further increasing the efficiency of energy production
91

91. Working Principle
• A fuel cell is a device that uses hydrogen (or hydrogen-rich fuel)
and oxygen to create electricity by an electrochemical process.
• A single fuel cell consists of an electrolyte sandwiched between
two thin electrodes (a porous anode and cathode).
• Hydrogen, or a hydrogen-rich fuel, is fed to the anode where a
catalyst separates hydrogen's negatively charged electrons from
positively charged ions (protons).
• At the cathode, oxygen combines with electrons and, in some
cases, with species such as protons or water, resulting in water or
hydroxide ions, respectively.
92

92. Working Principle
• The electrons from the anode side of the cell cannot pass through the
membrane to the positively charged cathode; they must travel around
it via an electrical circuit to reach the other side of the cell.
• This movement of electrons is an electrical current.
• The amount of power produced by a fuel cell depends upon several
factors, such as fuel cell type, cell size, the temperature at which it
operates, and the pressure at which the gases are supplied to the cell.
• Still, a single fuel cell produces enough electricity for only the smallest
applications. Therefore, individual fuel cells are typically combined in
series into a fuel cell stack.
• A typical fuel cell stack may consist of hundreds of fuel cells.
93

93. Classification of Fuel Cells
Fuel cells are classified primarily by the kind of electrolyte they employ.
This determines the kind of chemical reactions that take place in the cell,
the kind of catalysts required, the temperature range in which the cell
operates, the fuel required, and other factors.
Based on the type of Electrolyte
1. Alkaline Fuel cell (AFC)
2. Phosphoric Acid Fuel cell (PAFC)
3. Polymer Electrolytic Membrane Fuel Cell (PEMFC)
 Solid Polymer Fuel Cell (SPFC) and
 Proton Exchange Membrane Fuel cell (PEMFC)
4. Molten Carbonate Fuel Cell (MCFC)
5. Solid Oxide Fuel Cell (SOFC)
94

94. Alkaline Fuel Cells (AFC)
• The alkaline fuel cell uses an alkaline electrolyte such as 40% aqueous
potassium hydroxide.
• In alkaline fuel cells, negative ions travel through the electrolyte to the
anode where they combine with hydrogen to generate water and
electrons.
• AFCs were one of the first fuel cell technologies developed, and they
were the first type widely used in the U.S. space program to produce
electrical energy and water onboard spacecraft.
• These fuel cells use a solution of potassium hydroxide in water as the
electrolyte and can use a variety of non-precious metals as a catalyst
at the anode and cathode.
• High-temperature AFCs operate at temperatures between 100ºC and
250ºC (212ºF & 482ºF). However, more-recent AFC designs operate
at lower temperatures of roughly 23ºC to 70ºC (74ºF to 158ºF).
95

95. Alkaline Fuel Cells (AFC)
• AFCs are high-performance fuel cells due to the rate at which chemical
reactions take place in the cell. They are also very efficient, reaching
efficiencies of 60% in space applications.
• The disadvantage of this fuel cell type is that it is easily poisoned by carbon
dioxide (CO2).
• In fact, even the small amount of CO2 in the air can affect the cell's operation,
making it necessary to purify both the hydrogen and oxygen used in the cell.
• CO2 can combine with KOH to form potasium carbonate which will increase the
resistance. This purification process is costly. Susceptibility to poisoning also
affects the cell's lifetime, further adding to cost.
• Cost is less of a factor for remote locations such as space or under the sea.
However, to effectively compete in most mainstream commercial markets, these
fuel cells will have to become more cost effective.
• AFC stacks have been shown to maintain sufficiently stable operation for more
than 8,000 operating hours.
96

96. Alkaline Fuel Cells (AFC)
97

97. Molten Carbonate Fuel Cells (MCFC)
• The molten carbonate fuel cell uses a molten carbonate salt as the
electrolyte. It has the potential to be fuelled with coal- derived fuel gases,
methane or natural gas.
• These fuel cells can work at up to 60% efficiency. In molten carbonate fuel
cells, negative ions travel through the electrolyte to the anode where they
combine with hydrogen to generate water and electrons.
• MCFCs are currently being developed for natural gas and coal-based
power plants for electrical utility, industrial, and military applications.
• MCFCs are high-temperature fuel cells that use an electrolyte composed of
a molten carbonate salt mixture suspended in a porous, chemically inert
ceramic lithium aluminum oxide (LiAlO2) matrix.
• Since they operate at high temperatures of 650ºC and above, nonprecious
metals can be used as catalysts at the anode and cathode, to reduce cost.
98

98. Molten Carbonate Fuel Cells (MCFC)
• Unlike alkaline, phosphoric acid, and PEM fuel cells, MCFCs don't
require an external reformer to convert more energy-dense fuels to
hydrogen.
• Due to the high operating temperatures, these fuels are converted to
hydrogen within the fuel cell itself by a process called internal reforming,
which also reduces cost.
• Although they are more resistant to impurities than other fuel cell types,
ways to make MCFCs resistant enough to impurities from coal, such as
sulfur and particulates are under research.
• The primary disadvantage of MCFC is durability. High temperature
operation and corrosive nature of electrolyte accelerates component
breakdown and corrosion, decreasing cell life.
• Corrosion-resistant materials for components as well as fuel cell designs
are explored to increase cell life without decreasing performance.
99

99. Molten Carbonate Fuel Cells (MCFC)
100

100. Phosphoric Acid Fuel Cells (PAFC)
• The phosphoric acid fuel cell (PAFC) is considered the "first
generation" of modern fuel cells. It is one of the most mature cell
types and the first to be used commercially.
• They are 85% efficient when used for the co-generation of
electricity and heat, but less efficient at generating electricity
alone (37 to 42%).
• PAFCs are also less powerful than other fuel cells, given the same
weight and volume. As a result, these fuel cells are typically large
and heavy. PAFCs are also expensive.
• Like PEM fuel cells, PAFCs require an expensive platinum catalyst,
which raises the cost of the fuel cell.
101

101. Phosphoric Acid Fuel Cells (PAFC)
• A phosphoric acid fuel cell (PAFC) consists of an anode and a
cathode made of a finely dispersed platinum catalyst on carbon
and a silicon carbide structure that holds the phosphoric acid
electrolyte.
• In PAFC, protons move through the electrolyte to the cathode to
combine with oxygen and electrons, producing water and heat.
• PAFC use liquid phosphoric acid as an electrolyte— the acid is
contained in a Teflon-bonded silicon carbide matrix—and porous
carbon electrodes containing a platinum catalyst.
• This type of fuel cell is typically used for stationary power
generation, but some PAFCs have been used to power large
vehicles such as city buses PAFCs are more tolerant of impurities
102

102. Phosphoric Acid Fuel Cells (PAFC)
103

103. Polymer electrolyte membrane
fuel cells (PEMFC)
• In polymer electrolyte membrane (PEM) fuel cells, protons move
through the electrolyte to the cathode to combine with oxygen and
electrons, producing water and heat.
• PEMFC uses a polymeric membrane as the electrolyte, with platinum
electrodes. These cells operate at relatively low temperatures.
• These cells are best suited for cars, for buildings and smaller applications.
• PEM fuel cells—also called proton exchange membrane fuel cells—
deliver high power density and offer the advantages of low weight and
volume, compared to other fuel cells.
• PEM fuel cells use a solid polymer as an electrolyte and porous carbon
electrodes containing a platinum catalyst. They only use hydrogen,
oxygen from the air, and water to operate and do not require corrosive
fluids like some fuel cells.
104

104. PEM fuel cells (PEMFC)
• Polymer electrolyte membrane fuel cells operate at relatively low
temperatures, around 80°C (176°F).
• They are typically fueled with pure hydrogen supplied from storage
tanks or onboard reformers.
• Low temperature operation allows them to start quickly (less warm-up
time) and results in less wear on system components, resulting in better
durability.
• However, it requires that a noble metal catalyst (typically platinum) to
separate the hydrogen's electrons and protons, adding to system cost.
• The platinum catalyst is also extremely sensitive to CO poisoning,
making it necessary to employ an additional reactor to reduce CO in the
fuel gas if the hydrogen is derived from an alcohol or hydrocarbon fuel.
• This also adds cost. Developers are currently exploring platinum/
ruthenium catalysts that are more resistant to CO.
105

105. PEM fuel cells (PEMFC)
106

106. Solid Oxide Fuel Cells (SOFC)
• Work at higher temperatures.
• They use a solid ceramic electrolyte, such as zirconium oxide
stabilised with yttrium oxide, instead of a liquid and operate at
800 to 1,000°C.
• In SOFC, negative ions travel through the electrolyte to the anode
where they combine with hydrogen to generate water and
electrons.
• Efficiencies of around 60% and are expected to be used for
generating electricity and heat in industry and potentially for
providing auxiliary power in vehicles.
• Since electrolyte is a solid, the cells need not be constructed in
the plate-like configuration typical of other fuel cell types.
107

107. Solid Oxide Fuel Cells (SOFC)
• High temperature operation removes the need for precious-
metal catalyst, thereby reducing cost.
• They are not poisoned by carbon monoxide (CO), which can
even be used as fuel.
• Sulphur resistant - This allows SOFCs to use gases made from
coal.
• Scientists are currently exploring the potential for developing
lower-temperature SOFCs operating at or below 800ºC that
have fewer durability problems and cost less.
108

108. Solid Oxide Fuel Cells (SOFC)
109

109. Solid Oxide Fuel Cells (SOFC)
110

110. Fuel cell power plant
111

111. Hydrogen
• The first element on the periodic table.
• Odourless and colourless gas.
• Density: 0.837 kg/m3, Ignition temperature: 5000C, boiling
point: -2530C.
• Consists of only one proton and one electron.
• The lightest, most explosive and most abundant element on
Earth.
• These characteristics make it useful for lifting and as an
explosive i.e. the Hydrogen Bomb.
112

112. Why hydrogen energy?
No carbon-containing
products
Can be generated from water
using renewable energy
Hydrogen has a high energy
density
Used to power fuel
cell vehicles
Wind power
Electrolysis
Water
High efficiency
Hydrogen has a high energy
density
142 MJ per
kg of H2!
113

113. Hydrogen Power
• When hydrogen is used as an energy source, the only byproducts
are water and heat.
• Hydrogen is a renewable energy source.
• Once obtained, hydrogen can power virtually everything powered
by fossil fuels.
• Hydrogen is more powerful than gasoline: liquid hydrogen has a
BTU (British Thermal Unit) of 60,000 per pound, where gasoline
has 18,000 per pound. (1BTU=1.05kJ)
• NASA has used hydrogen as rocket fuel since the 1940’s, Primary
fuel while in space and for making drinking water.
• 1 pound H + O = 9 pounds water.
• This process generates a byproduct of usable electricity.
114

114. Hydrogen Power
• The hydrogen economy is the door to a new world free of pollution and
economic and political instability
• With technological advancements and expansion of the hydrogen
economy, the dream of a world free of fossil fuels can become a reality
• Hydrogen can be produced using diverse, domestic resources including
fossil fuels, such as natural gas and coal (with carbon sequestration);
nuclear; biomass; and other renewable energy technologies, such as
wind, solar, geothermal, and hydro-electric power.
• The overall challenge to hydrogen production is cost reduction.
• cost-competitive transportation is a key driver for energy independence
and therefore the hydrogen economy.
• Hydrogen must be comparable to conventional fuels and technologies on
a per-mile basis in order to succeed in the commercial marketplace.
115

115. Fuel cell degradation
Usually platinum – can degrade
in the presence of impurities
(such as hydrogen sulphide or
carbon monoxide)
116

116. UK Hydrogen Economy in 2030
1.6 million fuel cell vehicles on
the road in the UK
1,100 hydrogen refuelling
stations in operation
254,000 tonnes of hydrogen
produced a year
A report by UK H2Mobility (2013)
117

117. Methods of Hydrogen Production
• Fossil Fuel Based Hydrogen Production
• Steam Reforming of Natural Gas
• Water-Based Hydrogen Production:
Electrolysis, Photo electrolysis, Photobiological
• Other Methods of Hydrogen Generation:
Biomass Gasification and Pyrolysis
118

118. Fossil Fuel Based Hydrogen Production
• Produced from coal, gasoline, methanol and natural gas
• The fossil fuel that has the best hydrogen to carbon ration is
natural gas or methane- CH4.
• Not emission free
• The cost of natural gas has tripled in recent years
• Will have to rely on imports to supply the natural gas
• Natural gas is not renewable
Issues with Natural Gas in Hydrogen
Production
119

119. Steam Reforming of Natural Gas
• Steam reforming of natural gas involves 2 steps
• 1st Step: Expose natural gas to high temperature steam
• 2nd Step: Expose carbon monoxide to high temperature steam
• The resulting hydrogen and carbon dioxide is sequestered and
stored in tanks
• Most commonly used method.
120

120. 121
• Steam reforming, also known as steam methane reforming, involves reacting
a hydrocarbon with steam at high temperature (700 to 1,0000C) in the
presence of a metal catalyst, yielding CO and H2. Of the processes used to
make H2, steam reforming is the most widely practiced by industry and can
utilize a variety of carbon feedstocks, ranging from natural gas to naphtha,
liquid petroleum gas (LPG), or refinery off-gas. Steam reforming, in its
simplest form using methane as a feedstock, follows the general reaction
(1.3)
• Water shift gas reactions form CO2 and H2 using water and CO at elevated
temperature, as shown in equation 1.4. The reaction may be used with
catalysts, which can become poisoned by S if concentrations are high in the
feed gas. The water shift gas reaction is used as a secondary means of
processing syngas when greater amounts of H2 are desired from gasification.
(1.4)
  2
2
4 3H
CO
O
H
CH gas 


  2
2
2 CO
H
O
H
CO gas 


Methods of producing hydrogen fuel
121

121. 122
• Partial oxidation is the basic gasification reaction, breaking down a
hydrogenated carbon feedstock (typically coal or petroleum coke) using heat in
a reducing environment, producing CO and H2. A number of techniques are
utilized to separate H2 from the CO in syngas or to enrich the H2 content of the
syngas. These include H2 membranes, liquid adsorption of CO2 or other gas
impurities, and the water shift gas reaction.
• Autothermal reforming is a term used to describe the combination of steam
reforming and partial oxidation in a chemical reaction. It occurs when there is
no physical wall separating the steam reforming and catalytic partial oxidation
reactions. In autothermal reforming, a catalyst controls the relative extent of
the partial oxidation and steam reforming reactions. Advantages of
autothermal reforming are that it operates at lower temperatures than the
partial oxidation reaction and results in higher H2 concentration.
2
2
2
2
H
y
xCO
O
x
H
C y
x 


Methods of producing hydrogen fuel
122

122. Methods of producing hydrogen fuel
123

123. Methods of producing hydrogen fuel
124

124. Biomass Gasification and Pyrolysis
• Biomass is first converted into a gas through high-temperature
gasifying, resulting in a vapour.
• The vapor condensed into oils, which are steam reformed to
generate hydrogen.
• The feedstock can consist of woodchips, plant material, and
agricultural and municipal wastes.
• When biological waste is used as a feedstock-completely
renewable, sustainable method of hydrogen generation.
125

125. Electrolysis
• Use electricity to split water into its constituent elements and is
accomplished by passing an electric current through water.
• Produces very pure hydrogen (used in pharmaceutical, electronics
and food industries) and is very expensive, relative to steam
reformation due to the electrical input
• However, when coupled with a renewable energy source (for the
electrical input) electrolysis can provide a completely clean and
renewable source of energy.
• The direct conversion of sunlight into electricity using a
photoelectrolyzer placed in water.
• The photovoltaics and the semiconductor power the electrolyzer by
generating electricity from the sunlight.
• When exposed to sunlight, begins to generate hydrogen which is then
collected and stored.
Photoelectrolysis
126

126. Storage of hydrogen energy
127

127. Hydrogen Storage
• Hydrogen storage is the main technological problem with the hydrogen
economy.
• Due to its poor energy density per volume (although it has good energy
density per weight), hydrogen requires a large storage tank.
• If the tank is of the same size, more hydrogen will be compressed into
the tank making it heaver AND losing energy to the compression step.
• An alternative is to store hydrogen in its liquid state
• Liquid hydrogen’s boiling point of -423.1888 0F
• Low Temperature -> high energy loss
• The tanks must be well-insulated to prevent boil-off.
• Ice may form around the tank and corrode it further if the insulation
fails. Such insulation is expensive and delicate.
Liquid Hydrogen
128

128. Issues and Problems
One Major Issue is Safety:
1. legislators will have to create new processes for people to follow when
they must handle an incident involving a fuel cell vehicle or generator
2. Engineers will have to design safe, reliable hydrogen delivery systems
(i.e. fueling stations)
Then Cost
1. Expensive: proton exchange systems, precious metal catalysts, gas
diffusion layers and bipolar plates
2. To be priced competitively, fuel cell systems must cost $35/kW
3. Currently, high volume production is at $110/kW
4. One way to lower cost -> reduce need for platinum or find an
alternative.
129

129. Issues and Problems
Another is Durability:
1. Cell membranes must be durable and function at extreme temperatures.
2. cars start and stop frequently - important for membranes to remain
stable under cycling temperatures.
3. The membranes used now tend to degrade when fuel cells are turned on
and off.
Then infrastructure
1. Must have infrastructure for hydrogen generation and delivery.
2. Includes production plants, pipelines and truck transport, and fueling
stations
3. The development of a marketable fuel cell vehicle may drive the
development of an infrastructure to support it.
130

130. Merits & Demerits
131

131. Merits & Demerits
132

132. Application of hydrogen energy
133

133. 134
Thank You