ocean and geothermal

1. OCEAN & GEOTHERMAL
ENERGY
UNIT 4

2. CONTENT
• Introduction of Ocean Energy
• Types of OTEC
• Wave Energy
• Tidal Energy
• Geothermal Energy
• Geothermal Types
• Advantages & Disadvantages
• Conclusion

3. INTRODUCTION
• Ocean thermal energy conversion is a process that can produce electricity by using the
temperature difference between deep cold ocean water and warm tropical surface water
• OTEC is an energy technology that converts solar radiation to electric power
• OTEC utilizes the world’s largest solar radiation collector
• The ocean contains enough energy power all of the world’s electrical needs
• Oceans cover more than 70% of earth’s surface, making them the world’s largest solar
collectors
• OTEC is a renewable energy technology that converts solar radiation into electrical power
by use of world oceans.
• OTEC process uses temperature difference between cold deep water (5ºc) & warm
surface water (27ºc) to power a turbine to generate electricity.

4. TYPES
There are three types of electricity conversion system
• Closed, OTEC cycle power plant
• Open, OTEC cycle power plant
• Hybrid OTEC cycle power plant

5. CLOSED LOOP OTEC CYCLE
• In the closed cycle OTEC system, warm sea water vaporize a working fluid, such as
ammonia, flowing through a heat exchanger
• The vapour expands at moderate pressures and turns a turbine coupled to a generator
that produces electricity
• The vapour is then condensed in heat exchanger (condenser) using cold seawater
pumped from the ocean’s depths through a Coldwater pipe.
• The condensed working fluid is pumped back to the evaporator to repeat the cycle.
• The working fluid remains in a closed system and circulates continuously.
• The heat exchangers (evaporator and condenser) are a large and crucial component of the
closed cycle power plant, both in terms of actual size and capital cost.

6. CLOSED LOOP OTEC CYCLE

7. OPEN LOOP OTEC CYCLE
• In an open cycle OTEC, the sea water is itself used to generate heat without any kind of
intermediate fluid.
• Open cycle OTEC uses the tropical oceans warm surface water to make electricity
• The open cycle consists of the following steps:
• Flash evaporation of a fraction of the warm seawater by reduction of pressure below the
saturation value corresponding to its temperature
• Expansion of the vapour through a turbine to generate power.
• Heat transfer to the cold seawater sink resulting in condensation of the working fluid
• Compression of the non condensable gases (air released from the seawater streams at
the low operating pressure) to pressures required to discharge them from the system.

8. OPEN LOOP OTEC CYCLE

9. HYBRID LOOP OTEC CYCLE
• A hybrid cycle combines the features of both the closed cycle and open cycle systems
• In a hybrid OTEC system, warm seawater enters a vacuum chamber where it is flash
evaporated into steam, which is similar to the open cycle evaporation process
• The steam vaporizes the working fluid of a closed cycle loop on the other side of an
ammonia vaporizer
• The vaporized fluid then drives a turbine that produces electricity. The steam condenses
within the heat exchanger and provides desalinated water.

10. WAVE ENERGY
• 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
i. the wind speed
ii. the length of time for which the wind blows
iii. the distance over which the wind blows, or fetch
• Therefore, coasts that have exposure to the prevailing wind direction and that face long
expanses of open ocean have the greatest wave energy levels

11. WAVE ENERGY
• The strongest winds blow between 30 degree and 60 degree in latitude
• Western coastlines at these latitudes experience the most powerful waves
• 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
• Wave energy conversion devices are designed for optimal operation at a particular depth
range

12. TIDAL POWER
• Tidal power also called tidal energy, is a form of hydropower that converts the energy of
tides into useful forms of power, mainly electricity
• Cause of tides: gravitational force of sun, moon and earth’s rotation
• Two tidal cycles per day: 12 hours, 25 minutes
• Tidal range – large at coastal regions with high depth gradient
• water can be stored in an estuary during high tide
• Release during low tide, through turbines

13. TIDAL POWER
PLANT LOCATION
• Tidal mills built on inlets branching off tidal estuaries
• Average Tidal range : the higher, the better
• Feasibility of plant construction & basin closure
• Environmental consequences

14. TIDAL POWER
Why do the tides come and go?
• It is all to do with the gravitational force of the Moon and Sun, and also the rotation of
the Earth
• The gravitational force of the moon causes the oceans to bulge along an axis pointing
directly at the moon. The magnitude of this attraction depends on the mass of the object
and its distance away

15. TIDAL POWER
SPRING TIDES
• When the sun and moon are in a line their gravitational attraction on the earth combine
and cause a “spring” tides

16. TIDAL POWER
NEAP TIDES
• When they are as positioned in 90° from each other, their gravitational attraction each
pulls water in different directions, causing a “neap” tides

17. TIDAL POWER
1) TIDAL BARRAGE
• It’s a huge dam built across a river estuary. When the tide goes in and out, the water
flows through tunnels in the dam.

18. TIDAL POWER
2) TIDAL CURRENT TURBINES
• Make use of the kinetic energy of moving
water to power turbines, in a similar way to
wind turbines that use wind to power turbines.
• Operate during flood and ebb tides.
• Consists of a rotor, gearbox, and a generator.
These three parts are mounted onto a support
structure. There are three main types:
i. Gravity structure
ii. Piled structure
iii. Floating structure

19. TIDAL POWER
2) TIDAL CURRENT TURBINES
• GRAVITY STRUCTURES are massive steel or concrete structures attached to the base of
the units to achieve stability by their own inertia.
• PILED STRUCTURES are pinned to the seabed by one or more steel or concrete piles. The
piles are fixed to the seabed by hammering if the ground conditions are sufficiently soft
or by pre-drilling, positioning and grouting if the rock is harder.
• FLOATING STRUCTURES provide a potentially more convincing solution for deep water
locations.

20. TIDAL POWER
3) DYNAMIC TIDAL POWER PLANT
• Dynamic tidal power or DTP is a new and untested method of tidal power generation. It
would involve creating large dam-like structure extending from the coast straight to the
ocean, with a perpendicular barrier at the far end, forming a large 'T' shape.
• A single dam can accommodate over 8 GW (8000 MW) of installed capacity.
• A DTP dam is a long dam of 30 to 60 km which is built perpendicular to the coast, running
straight out into the ocean, without enclosing an area.
• Other concerns include: shipping routes, marine ecology, sediments, and storm surges.

21. TIDAL POWER
ECONOMICS:
• Tidal energy is not cost competitive because it is generally not commercially available.
• When selecting a spot to set up a tidal energy station it is important to make sure that it
will be economically feasible.
• To set up a tidal facility with an average annual output of 1050 MW would cost about 1.2
billion dollars, not including maintenance and running costs.
• This is far more expensive than coal and oil.

22. OTEC APPLICATION
• Ocean thermal energy conversion systems have many applications
• OTEC can be used to generate electricity, desalinate water, support deep water marine
and provide refrigeration and air conditioning as well as aid in crop growth and mineral
extraction
ELECTRICITY PRODUCTION:
• Two basic OTEC system design have been demonstrated to generate electricity: closed
cycle and open cycle
• The details are discussed in the above slide

23. OTEC APPLICATION
DESALINATED WATER:
• Desalinated water can be produced in open or hybrid cycle plants using surface
condensers
• A surface condenser can be used to recover part of the steam in the cycle and to reduce
the overall size of the heat exchangers
• One way to produce large quantities of desalinated water without incurring the cost of an
open cycle turbine is to use a hybrid system
• In a hybrid system, desalinated water is produced by vacuum flash distillation and power
is produced by a closed cycle loop

24. OTEC APPLICATION
REFRIGERATION AND AIR CONDITIONING:
• The cold [5°C (41ºF)] seawater made available by an OTEC system creates an opportunity
to provide large amounts of cooling to operations that are related to or close to the plant.
• The low-cost refrigeration provided by the cold seawater can be used to upgrade or
maintain the quality of indigenous fish, which tend to deteriorate quickly in warm tropical
regions.
• The cold seawater delivered to an OTEC plant can be used in hilled-water coils to provide
air conditioning for buildings

25. OTEC APPLICATION
MINERAL EXTRACTION:
• The ocean contains 57 trace elements in salt dissolved in
• The Japanese recently began investigating the concept of combining the extraction of
uranium dissolved in sea water with wave-energy technology
• They found that developments in other technologies were improving the viability of
mineral extraction processes that employ ocean energy.

26. ADVANTAGES OF OTEC
• Helps in producing fuels such as hydrogen, ammonia, and Methanol
• Produces base load electrical energy
• Produces desalinated water for industrial, agricultural, and residential uses .
• Is a resource for on-shore and near-shore Mari culture operations .
• Provides air-conditioning for buildings
• Provides moderate-temperature refrigeration .
• Has significant potential to provide clean, cost-effective electricity for the future.
• Food Aquaculture products can be cultivated in discharge water
• Eco- friendly
• Minimal maintenance costs compared to other power production plants
• Specially beneficial for small islands as they can become self sufficient
• OTEC helps in mining

27. DISADVANTAGES OF OTEC
• OTEC produced electricity at present would cost more than electricity generated from
fossils fuels at their current costs.
• No energy company put money in this project because it only had been tested in a very
small scale
• Construction of OTEC plants and lying of pipes in coastal waters may cause localized
damage to reefs and near-shore marine Ecosystem
• OTEC plant construction and operation may affect commercial and recreational fishing.
• Electrical hazards,
• Rotating machinery,
• Use of compressed gases,
• Heavy material-handling equipment, and
• Shop and maintenance hazards.

28. GEOTHERMAL ENERGY
• It’s simply the heat energy of the Earth,
Generated by various natural process,
Such as :
1. Heat from when the planet formed and
which has not yet been lost.
2. Decay of radioactive Elements.
3. Friction.

29. GEOTHERMAL ENERGY
Reservoirs can be suspected in the area where we find :-
• Geyser
• Boiling Mud Point
• Volcano
• Hot Springs
The rising hot water & steam is trapped in permeable & porous rocks to form a Geothermal
Reservoirs.
Reservoirs can be discovered by
• Testing the soil
• Analyzing underground
Temperature

30. GEOTHERMAL ENERGY
EXTRACTION AND USES :
The heat energy can be brought to earth surface by following ways..
• Directly from hot springs/ geysers
• Geothermal Heat Pump
USES ARE BROADLY CLASSIFIED AS :-
• Direct use
• Indirect use

31. GEOTHERMAL ENERGY
DIRECT USE :
• Hot springs use as spas.
• Heating water at fish farm.
• Provide heat for buildings.
• Raising plants for greenhouses, drying
crops.
• Provides heat to Industrial process.

32. GEOTHERMAL ENERGY
INDIRECT USE :
• Electricity Generation

33. GEOTHERMAL ENERGY
THERE ARE THREE TYPES OF POWER PLANT :-
• Dry steam power plant
• Flash steam power plant
• Binary cycle power plant

34. GEOTHERMAL ENERGY
DRY STEAM POWER PLANT :
• The oldest type of Geothermal power plant used since 1904.
• Geothermal Reservoir containing pure steam is required.
• Pure dry Steam drives turbine.
• Use steam piped directly from a geothermal reservoir to turn the generator turbines.
• Very rare type of Geothermal power plant.
• Operating at California, Italy & Japan

35. GEOTHERMAL ENERGY
DRY STEAM POWER PLANT :

36. GEOTHERMAL ENERGY
FLASH STEAM POWER PLANT :
• Commonly used Geothermal power plant.
• Take high-pressure hot water from deep inside the earth and convert it to steam to drive
the generator turbines.
• When the steam cools, it condenses to water and is injected back into the ground to be
used over and over again.
• Geothermal reservoirs containing both hot water & steam is required.
• Pressure changing system is required.
• Operating at Hawaii, Nevada, Utah & some other places.

37. GEOTHERMAL ENERGY
FLASH STEAM POWER PLANT :

38. GEOTHERMAL ENERGY
BINARY STEAM POWER PLANT :
• Transfer the heat from geothermal hot water to another liquid. The heat causes the
second liquid to turn to steam which is used to drive a generator turbine.
• Only the ground water is used.
• Vaporized hydrocarbons are used to spin the turbines.
• Hydrocarbons having lower boiling point such as isopentane, isobutane and propane can
be used.
• No harmful gases are emitted to the atmosphere because the underground water is never
disclosed outside.
• This’s the worldwide accepted power plant.

39. GEOTHERMAL ENERGY
BINARY STEAM POWER PLANT :

40. GEOTHERMAL ENERGY
ADVANTAGES :
• Geothermal energy is generally considered environmentally friendly and does not cause
significant amounts of pollution.
• Geothermal reservoirs are naturally replenished and therefore renewable (it is not
possible to exhaust the resources).
• Massive potential – upper estimates show a worldwide potential of 2 terawatts (TW).
• Excellent for meeting the base load energy demand (as opposed to other renewable’s
such as wind and solar).
• Great for heating and cooling – even small households can benefit.
• Harnessing geothermal energy does not involve any fuels, which means less cost
fluctuations and stable electricity prices.
• Geothermal energy is available everywhere, although only some resources are profitably
exploitable.
• Recent technological advancements (e.g. enhanced geothermal systems) have made
more resources exploitable and lowered costs.

41. GEOTHERMAL ENERGY
DISADVANTAGES :
• There are some minor environmental issues associated with geothermal power.
• Geothermal power plants can in extreme cases cause earthquakes.
• There are heavy upfront costs associated with both geothermal power plants and
geothermal heating/cooling systems.
• Very location specific (most resources are simply not cost-competitive).
• Geothermal power is only sustainable (renewable) if the reservoirs are properly
managed.

42. GEOTHERMAL ENERGY
• The first geothermal power plant is established in 1911 in Larderello, Italy.
• Currently only 24 countries are able to produce electricity from geothermal energy in
large scale producing a total of 11,700 MW of electricity.
• But it only comprises for about less than 0.4% of the worlds electricity consumption.
• This is mainly due to the fact that there is 75-80% chance of failure for exploratory well
digging and geothermal energy is not available at all places.
• Due to these facts developing countries like India is unable to install a geothermal power
plant due to high risk and unavailability of geothermal energy.
• To support the establishment of geothermal power plants the International Geothermal
Association(IGA) and International Renewable Energy Alliance(REN alliance) has funded
more than 10 projects and more than 65 countries are its members
• So in order to overcome these limitations research is going on at IGA,Bocham,Germany to
produce geothermal power more efficiently at low installation costs

43. CONCLUSION
• Ocean thermal energy conversion is a potential source of renewable energy that creates
no emissions. It is fuel free.
• It has a low environmental impact, can supply pure water for both drinking and
agriculture purposes.
• Can supply refrigeration and cooling and can provide a coastal community with reliable
energy.
• It is predicted that in the year 2040, the world will consume 820 quadrillion Btu of energy.
• Geothermal heating system can replace fossil fuel heating system in a particular area.
• Annual cost for common heating purpose can be reduced by more than 60 %
• Continued energy shortages have created added interest in geothermal energy for power
generation.
• Potential exists to provide all energy requirement of the world.
• Geothermal Energy appears to be a partial solution to our energy needs.