The document discusses geothermal and ocean energy, emphasizing how geothermal energy originates from the Earth's heat and can be harnessed for sustainable power through various methods like geothermal heat pumps and different types of power plants. It also covers ocean thermal energy conversion (OTEC), a process that generates electricity by exploiting the temperature difference between deep cold ocean water and warm surface water, highlighting its potential benefits for energy and freshwater production. Overall, both energy sources are highlighted as clean, renewable options for reducing air pollution and providing reliable energy.

1. UNIT –IV
GEOTHERMAL &
OCEAN ENERGY

2. GEOTHERMAL
Scientists theorize that 15 billion years ago, when the universe was
first forming, all matter exploded and released huge amounts of
energy. It is this energy that still fuels the sun. It also produces the heat
energy found inside the earth, which can be harnessed to create what is
called geothermal power.
The earth is in a constant state of change with shifting tectonic plates,
erupting volcanoes, and ongoing modification of its internal structures.
There are several methods for utilizing geothermal power being
explored and developed, but the changing nature of the energy source
complicates the process. New technologies are being developed to
address these issues, however, which gives new promise for
geothermal power as a viable energy source
When the earth was first forming, about 5 billion years ago, an
immense amount of energy was released. Some of this energy was

3. Earth's heat-called geothermal energy-escapes as steam at a hot
springs
Geothermal energy is the heat from the Earth. It's clean and
sustainable. Resources of geothermal energy range from the shallow
ground to hot water and hot rock found a few miles beneath the Earth's
surface, and down even deeper to the extremely high temperatures of
molten rock called magma.

5. RESOURCES OF GEOTHERMAL
Almost everywhere, the shallow ground or upper 10 feet of the Earth's
surface maintains a nearly constant temperature between 50° and 60°F
(10° and 16°C). Geothermal heat pumps can tap into this resource to
heat and cool buildings.
A geothermal heat pump system consists of a heat pump, an air
delivery system (ductwork), and a heat exchanger-a system of pipes
buried in the shallow ground near the building. In the winter, the heat
pump removes heat from the heat exchanger and pumps it into the
indoor air delivery system.
In the summer, the process is reversed, and the heat pump moves heat
from the indoor air into the heat exchanger. The heat removed from
the indoor air during the summer can also be used to provide a free

6. In the United States, most geothermal reservoirs of hot water are
located in the western states, Alaska, and Hawaii. Wells can be drilled
into underground reservoirs for the generation of electricity. Some
geothermal power plants use the steam from a reservoir to power a
turbine/generator, while others use the hot water to boil a working
fluid that vaporizes and then turns a turbine. Hot water near the
surface of Earth can be used directly for heat. Direct-use applications
include heating buildings, growing plants in greenhouses, drying
crops, heating water at fish farms, and several industrial processes
such as pasteurizing milk.
Hot dry rock resources occur at depths of 3 to 5 miles everywhere
beneath the Earth's surface and at lesser depths in certain areas. Access

11. TYPES OF WELLS
Drilled wells
It is constructed by either cable tool (percussion) or rotary-drilling
machines. Drilled wells that penetrate unconsolidated material require
installation of casing and a screen to prevent inflow of sediment and
collapse.
They can be drilled more than 1,000 feet deep. The space around the
casing must be sealed with grouting material of either neat cement or
bentonite clay to prevent contamination by water draining from the
surface downward around the outside of the casing.

13. DRIVEN WELLS
 Driven wells are constructed by driving a small-diameter pipe into
shallow water-bearing sand or gravel. Usually a screened well point is
attached to the bottom of the casing before driving.
These wells are relatively simple and economical to construct, but
they can tap only shallow water and are easily contaminated from
nearby surface sources because they are not sealed with grouting
material. Hand-driven wells usually are only around 30 feet deep;
machine-driven wells can be 50 feet deep or more.

15. DUG WELLS
Historically, dug wells were excavated by hand shovel to below the
water table until incoming water exceeded the digger’s bailing rate.
The well was lined with stones, bricks, tile, or other material to
prevent collapse, and was covered with a cap of wood, stone, or
concrete tile.
Because of the type of construction, bored wells can go deeper
beneath the water table than can hand-dug wells. Dug and bored wells
have a large diameter and expose a large area to the aquifer. These
wells are able to obtain water from less-permeable materials such as
very fine sand, silt, or clay.
Disadvantages of this type of well are that they are shallow and lack
continuous casing and grouting, making them subject to contamination

17. METHODS OF HARNESSING THE ENERGY
Dry Steam Plants
Flash Steam Plants
Binary Cycle Plants
geothermal heat pumps
Dry Steam Reservoirs
Wet Steam Reservoirs
Hot Water Reservoirs

19. DRY STEAM PLANTS
which use geothermal steam directly. Dry steam power plants use very
hot (>455 °F, or >235 °C) steam and little water from the geothermal
reservoir.
The steam goes directly through a pipe to a turbine to spin a generator
that produces electricity. This type of geothermal power plant is the
oldest, first being used at Lardarello, Italy, in 1904. An example of a
dry steam generation operation is at the Geysers in North California,
shown at right (Green Jobs, 2002).

21. FLASH STEAM PLANTS
which use high pressure hot water to produce steam when thepressure
is reduced. Flash steam power plants use hot water (>360 ºF, or >182
ºC) from the geothermal reservoir. When the water is pumped to the
generator, it is released from the pressure of the deep reservoir. The
sudden drop in pressure causes some of the water to vaporize to steam,
which spins a turbine to generate electricity.
Both dry steam and flash steam power plants emit small amounts of
carbon dioxide, nitric oxide, and sulfur, but generally 50 times less
than traditional fossil-fuel power plants.16 Hot water not flashed into
steam is returned to the geothermal reservoir through injection wells
(Green Jobs, 2002).

23. BINARY CYCLE PLANTS
which use moderate-temperature water (225 to 360 ºF, or 107 to 182 ºC)
from the geothermal reservoir. In binary systems, hot geothermal fluids are
passed through one side of a heat exchanger to heat a working fluid in a
separate adjacent pipe.
The working fluid, usually an organic compound with a low boiling point
such as Iso-butane or Iso-pentane, is vaporized and passed through a turbine
to generate electricity. An ammonia-water working fluid is also used in what
is known as the Kalina Cycle.
Makers claim that the Kalina Cycle system boosts geothermal plant
efficiency by 20-40% and reduces plant construction costs by 20-30%,
thereby lowering the cost of geothermal power generation (Green Jobs,
2002). The Mammoth Pacific binary geothermal power plant, located at the
Casa Diablo geothermal field, is pictured at right (Idaho National
Engineering and Environmental Laboratory, 2004).

25. GEOTHERMAL HEAT PUMPS.
The earth’s surface layer remains at an almost constant temperature
between 10 to 16C (50 to 50F). In this method, geothermal heat pumps
use a system of buried pipes linked to a heat exchanger and ductwork
into buildings.
In winter the relatively warm earth transfers heat into the buildings
and in summer the buildings transfer heat to the ground or uses some
of it to heat water. These heat pumps function as both air-conditioning
and heating systems in one (Green Jobs, 2002)

28. DRY STEAM RESERVOIRS
Dry steam reservoirs use the water in the earth's crust, which is heated
by the mantle and released through vents in the form of steam. Dry
steam reservoir geothermal plants have pipes that are drilled into the
site and used to trap the steam.
The steam is then used to turn turbines connected to a generator to
produce electricity. This is a highly efficient system for making
electricity and has been used by humans for many decades.
A large dry steam reservoir near Larderello, Italy, has powered local
electric railroads for about one hundred years.

29. WET STEAM RESERVOIRS
Sometimes, however, dry steam reservoirs do not refill themselves in
a very consistent manner. They can also have a lower temperature,
which results in a less effective combination of water droplets and
steam mixed together. Geothermal operators have found a solution to
these problems by building wet steam reservoirs.
For a wet steam reservoir to work, a well is drilled into the geothermal
site to release the steam, which can be anywhere from six hundred to
fifteen hundred feet deep. After the steam that is piped up passes
through and turns the turbines in the power plant on the surface, it is
sent into a condenser, which cools it. This cooled water can then be
pumped back into the wells. The water is heated again by the mantle
and released as steam. The steam turns the turbines again and produces

30. HOT WATER RESERVOIRS
Geothermal plants built over hot water reservoirs are more common
than either dry steam or wet steam reservoir plants. Although the water
in a hot water reservoir does not reach high enough temperatures to
become steam, it is still valuable. The water itself does not produce
electricity, but instead is piped through a network of pipes into the
walls of nearby homes and businesses. The heat from the pipes
radiates into the rooms, heating the air. Pipes return the water to the
hot water reservoir to be reheated and introduced back into the system.
Reykjavik, Iceland, is surrounded by hot water reservoir sites and is
also home to about eighty-five thousand people. Almost 80 percent of
the homes in this town are heated using hot water reservoir water.
There are about 180 locations in the United States that use hot water

31. POTENTIAL IN INDIA
Geothermal power plants operated in at least 24 countries in 2010, and
geothermal energy was used directly for heat in at least 78
countries. These countries currently have geothermal power plants
with a total capacity of 10.7 GW, but 88% of it is generated in just
seven countries: the United States, the Philippines, Indonesia, Mexico,
Italy, New Zealand, and Iceland.
The most significant capacity increases since 2004 were seen in
Iceland and Turkey. Both countries doubled their capacity. Iceland has
the largest share of geothermal power contributing to electricity supply
(25%), followed by the Philippines (18%).
 The number of countries utilizing geothermal energy to generate
electricity has more than doubled since 1975, increasing from 10 in

32. Although geothermal power development slowed in 2010, with global
capacity reaching just over 11 GW, a significant acceleration in the
rate of deployment is expected as advanced technologies allow for
development in new countries.
Heat output from geothermal sources increased by an average rate of
almost 9% annually over the past decade, due mainly to rapid growth
in the use of ground-source heat pumps. Use of geothermal energy for
combined heat and power is also on the rise.
India has reasonably good potential for geothermal; the potential
geothermal provinces can produce 10,600 MW of power (but experts
are confident only to the extent of 100 MW).
But yet geothermal power projects has not been exploited at all, owing
to a variety of reasons, the chief being the availability of plentiful coal
at cheap costs. However, with increasing environmental problems with

33. APPLICATIONS OF GEOTHERMAL ENERGY
Space/District Heating: Schemes utilizing geothermal heat provide
over 80% of the central heating needs of Reykjavik city in Iceland and
are employed in many towns in USA, Poland and Hungary. The World
Bank is currently supporting a program in Poland for using hot water
from unsuccessful oil wells to displace the use of coal for district
heating (World Bank Group, 2004).
Agriculture and Aquaculture: In temperate and colder climates,
greatly improved plant and fish growth can be achieved by heating
soils, greenhouses and fish ponds using geothermal heat. One example
of this is the largely successful Osearian Farm, Kenya (World Flowers,
2005).

35. BENEFITS OF GEOTHERMAL ENERGY
Minimize air pollution: Current geothermal fields produce only
about one-sixth of the carbon dioxide that a natural gas fueled
electrical generating power plant produces and none of the nitrous
oxide (NOx) or sulfur bearing (SOx) gases. New state of the art
geothermal binary and combined cycle plants produce virtually no air
emissions. Each 1,000 MW of new geothermal power will offset 1.9
million pounds per year of noxious and toxic air pollution emissions in
Western skies and offset about 7.8 billion pounds per year of climate
affecting CO2 emissions from gas fired plants or much larger amounts
from coal fired plants (USGS, 2004).

Renewable energy source: All types of geothermal energy are
renewable as long as the rate of heat extraction from the earth does not

36. OCEAN ENERGY

37. OCEAN THERMAL ENERGY CONVERSION(OTEC)
Ocean Thermal Energy Conversion (OTEC) is a process that can produce
electricity by using the temperature difference between deep cold ocean
water and warm tropical surface waters. OTEC plants pump large quantities
of deep cold seawater and surface seawater to run a power cycle and
produce electricity. OTEC is firm power (24/7), a clean energy source,
environmentally sustainable and capable of providing massive levels of
energy.
Recently, higher electricity costs, increased concerns for global warming,
and a political commitment to energy security have made initial OTEC
commercialization economically attractive in tropical island communities
where a high percentage of electricity production is oil based. Even within
the US, this island market is very large; globally it is many times larger. As
OTEC technology matures, it should become economically attractive in the
southeast US.

38. PRINCIPLES OF OTEC
Ocean Thermal Energy Conversion (OTEC) is a marine renewable
energy technology that harnesses the solar energy absorbed by the
oceans to generate electric power. The sun’s heat warms the surface
water a lot more than the deep ocean water, which creates the ocean’s
naturally available temperature gradient, or thermal energy.
OTEC uses the ocean’s warm surface water with a temperature of
around 25°C (77°F) to vaporize a working fluid, which has a low-
boiling point, such as ammonia. The vapor expands and spins a turbine
coupled to a generator to produce electricity. The vapor is then cooled
by seawater that has been pumped from the deeper ocean layer, where
the temperature is about 5°C (41°F). That condenses the working fluid
back into a liquid, so it can be reused. This is a continuous electricity
generating cycle.

40. UTILIZATION OF OTEC
Fresh Water: The first by-product is fresh water. A small hybrid 1
MW OTEC is capable of producing some 4,500 cubic meters of fresh
water per day, enough to supply a population of 20,000 with fresh
water. OTEC-produced fresh water compares very favourably with
standard desalination plants, in terms of both quality and production
costs.
Food: A further by-product is nutrient rich cold water from the deep
ocean. The cold “waste” water from the OTEC is utilised in two ways.
Primarily the cold water is discharged into large contained ponds, near
shore or on land, where the water can be used for multi-species
mariculture producing harvest yields which far surpass naturally
occurring cold water upwelling zones, just like agriculture on land.
Cooling: The cold water is also available as chilled water for cooling

42. BENEFITS OF OTEC
The distinctive feature of OTEC is the potential to provide baseload
electricity, which means day and night (24/7) and year-round. This is a
big advantage for for instance tropical islands that typically has a
small electricity network, not capable of handling a lot of intermittent
power.
Next to producing electricity, OTEC also offers the possibility of co-
generating other synergistic products, like fresh water, nutrients for
enhanced fish farming and seawater cooled greenhouses enabling food
production in arid regions. Last but not least, the cold water can be
used in building air-conditioning systems. Energy savings of up to
90% can be realized.
The vast baseload OTEC resource could help many tropical and
subtropical (remote) regions to become more energy self-sufficient

44. SETTING OF OTEC PLANTS
Requirements:
Feasibility of technology and operational necessities
Status of the technology and its future market potential
Contribution of the technology to protection of the environment
Climate
Financial requirements and costs
Clean Development Mechanism market status

46. HYBRID OTEC

47. FEASIBILITY OF TECHNOLOGY AND
OPERATIONAL NECESSITIES
Resource
The total energy available is one or two orders of magnitude higher
than other ocean energy options such as wave power; but the small
magnitude of the temperature difference makes energy extraction
comparatively difficult and expensive, due to low thermal efficiency.
The opportunities for OTEC extraction improve closer to the equator
in the tropics, but it should still be understood that the technology is
quite far from commercial application and relatively little research is
done on it globally.
Location
The best OTEC locations are those that have high surface
temperatures and access to cold deep water such as Hawaii. Without

48. Technical Requirements
• The installation of an OTEC system would require a significant
component of fabrication for the necessary piping and also marine
operations for the installation. Specialised low pressure generation
equipment would likely need to be purchased from abroad, but at this
stage there is no company is manufacturing such equipment. Much of
the onshore work (assuming the system is located on land) would be
similar to that required in a conventional thermal power station
regarding pipework, electrical work etc.
• Maintenance of OTEC systems is hard to determine at such an early
stage of development. As it stands OTEC systems have not
necessarily overcome the issues of biofouling, heat exchanger
degradation and sealing. Broadly the maintenance requirements of an
onshore OTEC plant should not be dissimilar from a conventional
thermal plant.

49. Legal/Regulatory
The installation of a commercial OTEC plant in a modern setting
would require a rigorous programme of consultation and
environmental impact assessments. Regulatory experience could
possibly be drawn from schemes such as geothermal power plants,
large geothermal ground heat pumps or the deep water lake cooling
systems such as the one installed in New York, US (Cornell,
2006). There is unlikely to be any kind of established regulatory
framework in any country possibly with the exception of the US due
to their experience with the Keahole Point project in Hawaii.
Social Acceptance
There is very little experience with public acceptance of OTEC
systems due to the extremely limited number of projects completed to
date. It is reasonable to expect that public perception of OTEC would
be largely positive as long as the environmental issues were well
understood and managed. The plant has an onshore footprint not

50. STATUS OF THE TECHNOLOGY AND
ITS FUTURE MARKET POTENTIAL
There are very few OTEC installations around the world. At Keahole
Point in Hawaii the US Government has had a small test facility
operating since 1974, a small plant was installed and operated on the
island of Naru by a Japanese firm and the southern state of Tamil Nadu
in India also investigated the possibility of a floating OTEC platform;
however all these developments date from a number of decades ago.
After a significant research focus in the USA in the 1980’s following
the oil crisis of the mid seventies, there has been a significant decline
in the level of attention given to OTEC systems. There are plans in the
USA to build a 1MW OTEC facility in Hawaii (HBEDT, 2009) where
much of the prior research into OTEC systems has taken
place. Research is also continuing into pipeline fabrication techniques

51. CONTRIBUTION OF THE TECHNOLOGY TO
PROTECTION OF THE ENVIRONMENT
The environmental impacts of OTEC systems are largely unknown.
The main concerns around the technology would be the effect on the
local ocean surface ecosystem due to the release of large volumes of
cooler water and the possibility that marine creatures were drawn into
the piping that feeds the OTEC plant.
Only during the course of further development, EIA studies and larger
projects will the marine energy community be able to gain a firmer
idea of any potential impacts on marine life.

52. CLIMATE
OTEC systems directly contribute to climate change mitigation by
providing a completely renewable energy source free of GHG
emissions (beyond the initial GHG gases associated with
construction).
However, the relative lack of development of OTEC schemes and
their low efficiencies means the total installed capacity will likely
remain very small in the short to medium term meaning that their
overall contribution to mitigation with the next decades will be
relatively small.

53. CLEAN DEVELOPMENT MECHANISM MARKET
STATUS
The information is kindly provided by the UNEP Risoe Centre Carbon
Markets Group.

55. THERMODYNAMIC CYCLES
• A thermodynamic cycle is a series of thermodynamic processes which
returns a system to its initial state.
• Properties depend only on the thermodynamic state and thus do not
change over a cycle.
• Variables such as heat and work are not zero over a cycle, but rather
depend on the process. The first law of thermodynamics dictates that
the net heat input is equal to the net work output over any cycle.
• The repeating nature of the process path allows for continuous
operation, making the cycle an important concept in
thermodynamics.

56. DIFFERENT PROCESSES
Isobaric
Isometric
Adiabatic
ΔT ≠ 0 but Q = 0
Isothermal
ΔT = 0 but Q ≠ 0
Cyclic

57. TYPES OF CYCLES
Heat Engine
Rankine
Gas Power Systems
 Brayton
Internal Combustion Engines
 Otto, Diesel,Stirling, Atckison
Refrigeration
Heat Pump
Air Conditioning

58. HEAT ENGINE (RANKINE CYCLE)
Heat addition and ejection are isobaric (and not isothermal)
Working fluid is alternatively vaporized and condensed

59. GAS POWER SYSTEMS (BRAYTON CYCLE)

60. INTERNAL COMBUSTION ENGINES
OTTO CYCLE
Octane rating- measure of the resistance of gasoline and other fuels to
detonate at constant volume

61. DIESEL CYCLE
 Highest efficiency due to
compression ration
 low speed engines can exceed
50%
 Diesel Cetanes
 combustion quality during
compression ingnition

62. STIRLING CYCLE
 Similar to Otto cycle
 replace adiabatic per isothermals
 Used in Micro CHP

63. ATKISON CYCLE
four-stroke cycle to occur in a single turn of the crankshaft
designed to bypass patents covering the existing Otto cycle engines

64. REFRIGERATION CYCLE(VAPOR COMPRESSION
CYCLE)

65. HEAT PUMP

66. AIR CONDITIONING

68. TIDAL ENERGY
Tidal power, also called tidal energy, is a form of hydropower that
converts the energy of tides into useful forms of power - mainly
electricity.
Tides are the waves caused due to the gravitational pull of the moon
and also sun(though its pull is very low).
During high tide, the water flows into the dam and during low tide,
water flows out which result in turning the turbine.

69. Ocean tides are the periodic rise and fall of ocean water level
occurs twice in each lunar day.
During one lunar day (24.83 H) the ocean water level rises twice
and fall twice.
Time interval between a consecutive low tide and high tide is
6.207 hrs.
Tidal range is the difference between the consecutive high tide
and low tide.

72. • Single Basin Scheme: This scheme has one barrage and one water
storage basin, one way system, the incoming tide is allowed to fill the
basin through sluice ways during the tide and the impounded water is
used to generate electricity by letting the water flow from basin to the
sea through the turbines during single basin schemes is intermittent
generation power.

73. • Double Basin Scheme: In the double basin scheme, there are two
basins on the landward side with the powerhouse located at the
interconnecting waterway between the two basins.

75. Advantages of Tidal Energy
1) It is an inexhaustible source of energy.
2) Tidal energy is environment friendly energy and doesn't produce greenhouse
gases.
3) As 71% of Earth’s surface is covered by water, there is scope to generate this
energy on large scale.
4) We can predict the rise and fall of tides as they follow cyclic fashion.
5) Efficiency of tidal power is far greater as compared to coal, solar or wind
energy. Its efficiency is around 80%.
6) Although cost of construction of tidal power is high but maintenance costs are
relatively low.
7) Tidal Energy doesn’t require any kind of fuel to run.
8) The life of tidal energy power plant is very long.
9) The energy density of tidal energy is relatively higher than other renewable
energy sources.

76. Disadvantages of Tidal Energy
1) Cost of construction of tidal power plant is high.
2) There are very few ideal locations for construction of plant and they too are
localized to coastal regions only.
3) Intensity of sea waves is unpredictable and there can be damage to power
generation units.
4) Influences aquatic life adversely and can disrupt migration of fish.
5) The actual generation is for a short period of time. The tides only happen
twice a day so electricity can be produced only for that time.
6) Frozen sea, low or weak tides, straight shorelines, low tidal rise or fall are
some of the obstructions.
7) Usually the places where tidal energy is produced are far away from the
places where it is consumed. This transmission is expensive and difficult.

78. WAVE ENERGY
Waves are generated by the wind as it blows across the sea surface.
Energy is transferred from the wind to the waves.
Wave energy is sometimes confused with tidal energy, which is quite
different.
Waves travel vast distances across oceans at great speed. The longer
and stronger the wind blows over the sea surface, the higher, longer,
faster and more powerful the sea is.

79. COMPARING TO OTHER RENEWABLE ENERGY
SOURCES
Northern CA: 30 kilowatt per m wave crest
(with storms 1 Megawatt per m)
Solar energy: 300 watts per m2
Wind energy: 800 watts per m2

80. TYPES OF DEVICES FOR WAVE ENERGY
Surface Attenuator(pelamis)
Oscillating Water Column (limpet)
Point Absorber Buoy
Overtopping Device
Oscillating Wave Surge Converter
Tidal Energy

81. SURFACE ATTENUATOR
81

82. 82

83. OSCİLLATİNG WATER COLUMN
83

84. OVERTOPPİNG DEVİCE
84

85. POİNT ABSORBER BUOY
85

86. 86

87. BENEFITS OF OCEAN WAVE ENERGY
 Why better than other renewable energies
Available 24/7 on 365 days - therefore power produced from them is
much steadier and more predictable – waves can be accurately
predicted 48 hours in advance and therefore forecast energy output
(BUT irregularity in wave ampitude, and direction)
Good data on waves from wave monitoring bouys
Wave energy contains 1000 times the kinetic energy of wind (can
produce the same amount of power in less space)

88. ADVANTAGES OF WAVE ENERGY
Renewable: The best thing about wave energy is that it will never run
out. Unlike fossil fuels, which are running out.The waves flow back
from the shore, but they always return.
Environment Friendly: Also unlike fossil fuels, creating power from
waves creates no harmful byproducts such as gas, waste and pollution.
The energy is free - no fuel needed, no waste produced.
Not expensive to operate and maintain.
Can produce a great deal of energy.
88

89. DİSADVANTAGES OF WAVE ENERGY
Suitable to Certain Locations:The biggest disadvantage to getting your
energy from the waves is location. Only power plants and towns near
the ocean will benefit directly from it.
Effect on marine Ecosystem :As clean as wave energy is, it still
creates hazards for some of the animals near it.
Depends on the waves - sometimes you'll get loads of energy,
sometimes almost nothing.
Needs a suitable site, where waves are consistently strong.
Must be able to withstand very rough weather. 89

91. POTENTIALAND CONVERSION TECHNIQUES
CLOSED-CYCLE
Closed-cycle systems use fluids with a low boiling point, such as
ammonia, to rotate a turbine to generate electricity. Warm surface
seawater is pumped through a heat exchanger, where the low-boiling-
point fluid is vaporized. The expanding vapor turns the turbo-
generator. Cold deep seawater—which is pumped through a second
heat exchanger—then condenses the vapor back into a liquid that is
then recycled through the system.
In 1979, the Natural Energy Laboratory and several private-sector
partners developed the mini OTEC experiment, which achieved the
first successful at-sea production of net electrical power from closed-
cycle OTEC. The mini OTEC vessel was moored 1.5 miles (2.4 km)
off the Hawaiian coast and produced enough net electricity to

92. OPEN-CYCLE
• Open-cycle systems use the tropical oceans' warm surface water to
make electricity. When warm seawater is placed in a low-pressure
container, it boils. The expanding steam drives a low-pressure turbine
attached to an electrical generator. The steam, which has left its salt
behind in the low-pressure container, is almost pure, fresh water. It is
condensed back into a liquid by exposure to cold temperatures from
deep-ocean water.
• In 1984, the Solar Energy Research Institute (now the National
Renewable Energy Laboratory) developed a vertical-spout
evaporator to convert warm seawater into low-pressure steam for
open-cycle plants. Energy conversion efficiencies as high as 97% were
achieved. In May 1993, an open-cycle OTEC plant at Keahole Point,
Hawaii, produced 50,000 watts of electricity during a net power-
producing experiment.

93. HYBRID
• Hybrid systems combine the features of closed- and open-cycle
systems. In a hybrid system, warm seawater enters a vacuum chamber,
where it is flash-evaporated into steam, similar to the open-cycle
evaporation process. The steam vaporizes a low-boiling-point fluid (in
a closed-cycle loop) that drives a turbine to produce electricity.

94. MINI-HYDEL POWER PLANT
• Micro hydro or Micro hydel is a type of hydroelectric power that
typically produce up to 100 kW of electricity using the natural flow of
water.
• These installations can provide power to an isolated home or small
community, or are sometimes connected to electric power networks.
• There are many of these installations around the world, particularly in
developing nations as they can provide an economical source of
energy without the purchase of fuel.

95.  Turbines converts the flow and pressure energy into
mechanical energy. Turbines are basically of two types i.e. Reaction &
Impulse and Depending upon the head of the available water further
divide in three categories i.e. High, Medium & Low head.
 According to site specification (i.e. head and flow) we
choose the turbine to use in micro- hydro power plant.
TURBINES

96. TURBINE TYPE FLOW HEAD
Pelton wheel Low High ( > 70 feet)
Turgo Medium
Medium (25-75
feet)
Cross Flow High Low (<25 feet)

97. Theoretical Power
P = 9.81 × ρ × Q × H
Where :
ρ = Density of water, kg/m3
Q = Flow Rate, m3/s
H = Head, meters
MATHEMATICALANALYSIS

98. OPERATING PRINCIPLE
Water from the reservoir flows due to
gravity to drive the turbine.
Turbine is connected to a generator.
Power generated is transmitted over power
lines.

99. OPERATING PRINCIPLE
A water turbine that cover the energy of flowing or
falling water into mechanical energy that drives a
generator, which generates electrical power. This is
a heart of hydropower power plant.
A control mechanism to provide stable electrical
power. It is called governor.
Electrical transmission line to deliver the power to
its destination.
Micro hydro in northwest Vietnam

100. CONSTRUCTION
Construction details of a microhydro plant are site-
specific. Sometimes an existing mill-pond or other
artificial reservoir is available and can be adapted for
power production. In general, microhydro systems are
made up of a number of components.
The most important include the intake where water is
diverted from the natural stream, river, or perhaps a
waterfall. An intake structure such as a catch box is
required to screen out floating debris and fish, using a
screen or array of bars to keep out large objects.
In temperate climates this structure must resist ice as
well. The intake may have a gate to allow the system
to be dewatered for inspection and maintenance.

101. HEAD AND FLOW
CHARACTERISTICS
Microhydro systems are typically set up in areas capable of producing
up to 100 kilowatts of electricity. This can be enough to power a home
or small business facility. This production range is calculated in terms
of "head" and "flow". The higher each of these are, the more power
available.
"Head" is the pressure measurement of falling water expressed as a
function of the vertical distance the water falls. This change in
elevation is usually measured in feet or meters. A drop of at least 2 feet
is required or the system may not be feasible.
 When quantifying head, both gross and net head must be considered.
Gross head approximates power accessibility through the vertical
distance measurement alone whereas net head subtracts pressure lost

102. TURBINE TYPES

103. USES
Microhydro systems are very flexible and can be deployed in a
number of different environments.
 They are dependent on how much water flow the source (creek, river,
stream) has and the velocity of the flow of water.
Energy can be stored in battery banks at sites that are far from a
facility or used in addition to a system that is directly connected so
that in times of high demand there is additional reserve energy
available.
 These systems can be designed to minimize potential damage
regularly caused by large dams or other mass hydroelectric generation
sites.

104. POTENTIAL FOR RURAL DEVELOPMENT
In relation to rural development, the simplicity and low relative cost of micro
hydro systems open up new opportunities for some isolated communities in need
of electricity.
With only a small stream needed, remote areas can access lighting and
communications for homes, medical clinics, schools, and other facilities.
Microhydro can even run a certain level of machinery supporting small
businesses. Regions along the Andes mountains and in Sri Lanka and China
already have similar, active programs.
One seemingly unexpected use of such systems in some areas is to keep young
community members from moving into more urban regions in order to spur
economic growth.
 Also, as the possibility of financial incentives for less carbon intensive processes
grows, the future of microhydro systems may become more appealing.

105. COST
The cost of a micro hydro plant can be between 1,000 and 20,000 U.S
dollars

106. MERITS
• Microhydro power is generated through a process that utilizes the
natural flow of water. This power is most commonly converted into
electricity.
• With no direct emissions resulting from this conversion process, there
are little to no harmful effects on the environment, if planned well,
thus supplying power from a renewable source and in a sustainable
manner.
• Microhydro is considered a "run-of-river" system meaning that water
diverted from the stream or river is redirected back into the same
watercourse.Adding to the potential economic benefits of microhydro
is efficiency, reliability, and cost effectiveness.

107. DEMERITS
Microhydro systems are limited mainly by characteristics of the site.
The most direct limitation comes from small sources with minuscule
flow.
Likewise, flow can fluctuate seasonally in some areas. Lastly, though
perhaps the foremost disadvantage is the distance from the power
source to the site in need of energy.
This distributional issue as well as the others are key when
considering using a microhydro system.

108.  New computerized control systems and improved turbines
may allow more electricity to be generated from existing facilities in
the future.
 Small scale and low head hydro capacity will probably
increase in the future. Low head turbines, and standardized turbine
production, lowers the costs of hydro-electric power at sites with low
heads.
FUTURE OF MICRO-HYDRO POWER PLANT

110.  http://www.microhydropower.net
 http://www.ieee.org
https://www.slideshare.net
http://www.mwit.ac.th
https://energy.gov/eere/energybasics/articles/ocean-thermal-energy-conversion-basics.
Read more: http://www.scienceclarified.com/scitech/Energy-Alternatives/Geothermal-
Power.html#ixzz4c22Q4Lvs
• BOOKS…
Micro Hydro Power Handbook vol. 1,2
by. J. D. McKinney & Prof. C. C. Warnick
Power Plant Engg. by. P. K. NAG
Electrical Machinery by, Dr. P. S. Bimbhra
REFERENCES…