Geothermal Energy
What is Geothermal Energy ?
 It’s simply the heat energy of the earth, generated
by various natural processes, such as Decay of
radioactive elements
 The source of heat energy is radioactive decay
and the crust of the earth acts as a thermal
insulator to prevent heat from escaping to space.
The deeper you go, the hotter it is !!!
Geothermal Reservoirs
Reservoirs can be suspected in the areas
where we find
1.
2.
3.
4.
Geyser
Boiling mud pot
Volcano
Hot springs
Geothermal Reservoirs (cont.)
• The rising hot water & steam
is trapped in permeable &
porous rocks to form a
geothermal reservoir.
• Reservoirs can be discovered
by
– testing the soil
– Analyzing underground
temperature
Extraction & uses
• The heat energy can be extracted to earth
surface by following ways..
– Directly from hot springs
– Geothermal heat pump
• Uses are broadly classified as:– direct use
– indirect use
Direct use of Geothermal Energy
•
•
•
•
Hot springs, used as spas.
Heating water at fish farms.
Provide heat for buildings.
Provides heat to industrial processes.
Indirect use of Geothermal Energy
• Electricity Generation:
Electricity Generation (cont.)
There are 3 types of power plants:Dry steam power plant
Flash steam power plant
Binary cycle power plant
Dry Steam power plant
 It takes steam out of fractures in the ground and uses it
to directly drive the generator turbines, where natural
steam erupted from the Earth.
 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.
Dry Steam power plant
Flash steam power plant
 It 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.
 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
Flash steam power plant
Binary cycle power plant (cont.)
 It transfer the heat from geothermal hot water to a
secondary fluid which is lower boiling point than water.
This causes the secondary fluid to turn to vapor, which then
drives a turbine. Most geothermal power plants in the
future will be binary plants.




Does not use steam directly to spin turbines.
Only the heat of the underground water is used.
Vaporized hydrocarbons are used to spin the turbine.
Hydrocarbons having lower boiling point than water are used
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.
Binary cycle power plant
Cost
 Direct use of geothermal energy is absolutely
cheaper than other energy sources.
 Cost of electricity generation depends upon
certain factors:
– Temperature and depth of resource
– Type of resource (steam, liquid, mix)
– Available volume of resource
– Size and technology of plant
Advantages
It can be extracted without burning a fossil fuel such as coal, gas,
or oil.
Geothermal fields produce only about one-sixth of the carbon
dioxide that a relatively clean natural-gas-fuelled power plant
produces.
Unlike solar and wind energy, geothermal energy is always
available, 365 days a year.
It's also relatively inexpensive; savings from direct use can be as
much as 80 percent over fossil fuels.
Disadvantages
• Not widespread source of energy
• May release harmful gases- like hydrogen
sulfide
• Disposal of some geothermal fluids- which may
contain low levels of toxic materials
• Earthquakes
OCEAN WAVE ENERGY
What is Wave Energy?
Wave energy (or wave power) is the transport
and capture of energy by ocean surface waves.
The energy captured is then used for all different
kinds of useful work, including electricity
generation, pumping of water.
Wave energy is also a type of renewable energy
and is the largest estimated global resource form
of ocean energy
How can we get Energy from the ocean
There are three basic ways to tap the ocean for its
energy. We can use
1. The ocean's waves.
2. The ocean's high and low tides .
3. Temperature differences in the water.
 Kinetic energy (movement) exists in the moving
waves of the ocean.
 That energy can be used to power a turbine. 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 goes down, air flows through the
turbine and back into the chamber through doors
that are normally closed.
Technology
• There are multiple different technologies used
for Wave energy. There are four main types of
technology used;
• Absorbers:
• Attenuators
• Oscillation water columns
• Overtopping and Inverted
Point Absorbers:
Point Absorbers extract energy from the rise
and fall of the waves with a buoy. Once the
energy is extracted it is then converted to
electrical energy with a generator.
Attenuators wave Energy
• Attenuators capture energy by being placed perpendicular
to the length of the wave, this causes the attenuator to
contentiously flex where segments are connected. This
connection is then connected to hydraulic pumps which
convert the energy.
Oscillating Water Column (OWC)
Overtopping – “Wave Dragon”
Cont.…
Available Energy Flux vs Ocean Depth
Damaging Waves Occurrence vs Ocean
Depth
Cost vs Ocean Depth?(Reading assignement )
Tidal Energy
Two types of tidal plant facilities
 Tidal barrages
 Tidal stream generator
Tidal barrages
• Tidal barrages make use of the potential
energy in the difference in height between high
and low tides.
Tidal stream generator
• Make use of the kinetic energy of moving
water to power turbines.
• A similar way to wind turbines that use wind
to power turbines
Mizan - Tepi University
College of Engineering and Technology
Department of Electrical and Computer Engineering
Energy Conversion and rural Electrification
Assignment
1. What are the existing hydropower , wind power , solar power , nuclear power , thermal
power and Geothermal in Ethiopia with its installed capacity and completed year
2. How many hydropower, wind power, solar power, thermal power, nuclear power
Geothermal power potential is available in Et
hiopian for the production of electric
energy.
3. How much percent of hydropower, wind power, solar power, nuclear power, thermal
power and Geothermal is developed in Ethiopia while compare to their existing
potentials.
4. How much percent of the hydropower plant contribute for the total power demand in
Ethiopia? Describe using pie chart.