Geothermal energy comes from heat within the earth and can be used to generate electricity. The first geothermal power plant was built in 1904. There are three main types of geothermal power plants: dry steam, flash steam, and binary cycle. Dry steam plants use steam directly from reservoirs. Flash steam plants use hot water that flashes to steam to spin turbines. Binary cycle plants are used when resources are cooler and use a secondary fluid to extract heat. Sites must be near geothermal reservoirs and meet other criteria. Geothermal energy provides base load power but has high initial costs and can impact local environments.

2. INTRODUCTION
Geothermal comes from Greek
word,Geo(earth)+thermal(heat).
originates from the original
formation of the planet, from
radioactive decay of minerals,
and from solar energy absorbed
at the surface.
The first attempt to generate
electricity from this energy
source did not occur until the
20th century.
Prince Piero Ginori Conti tested
the first geothermal generator
on 4th July 1904.

3. INTRODUCTION contd..
Heat from the earth crust used as natural and constant
source as any other renewable sources.
Outer crust of earth has average thickness of 32 Km and
below that is magma.
As we go deeper, the temperature increase by 1◦c for
every 35 to 40m depth.
Taping heat is clean and sustainable way to reduce fossil
fuel use.
Worldwide, geothermal plants have the capacity to
generate about 10 GW as of 2007, and in practice generate
0.3% of global electricity demand
8000 MW installed capacity in 20 countries (2800 MW in
USA).
In California – 5% of electricity from geothermal.

4. Yellow spotted are some of the GPPs found around
world

5. SITE SELECTION
Slope limitations(less than 15%).
Location of site near the river is not suitable.
Absence of fault(cracks) in the earth’s crust.
Faraway from population Center.
Road accessibility.
Availability of advanced technologist.
Availability of hot springs and geysers.
The fluid temperature(180 degree Celsius) should
be available at depths not exceeding 3 Kms.

6. Principle of operation
GPP use steam produced from reservoir of hot
water found a couple of miles below the earth’s
surface to rotate the turbine that activate generator.
Various type of cycles have been suggested .
Two most important cycles, which are being used
in practice are:
1)Indirect condensing cycle.
2)Direct non-condensing cycle.

7. Indirect condensing cycle
Involves the use of heat exchanger.
About 15% to 20 % of stream power potential had to
be sacrifice in exchanger.
This cycle was considered economical, because of the
recovery of minerals and non-condensable gases.
Through advancement in technology and declining
attraction of mineral extraction, this cycle has been
rendered obsolete.
The steam after striking the turbine is condensed back
into water and injected back into the ground.

8. Direct non-condensing cycle
Simplest, cheapest and most widely used
geothermal cycle.
Bore steam either from direct bores or after
separation from wet bores is passed to the turbine
and exhausted to the atmosphere.
Water should be pumped into artificial volcanic
crater s and then turned into useful stream.
Geothermal power plant are unattended and don't
need full time supervision.
Stream temperature and stream line drains should
be closely monitored, for any indication of water.

9. Direct non-condensing cycle contd..
Rated turbine throttle pressure is maintained
by connecting sufficient number of wells to the
supply line of unit.
Unit should be inspected for every three years.
It can be operated at high annual load plant
load factor of order of 90%or more with proper
maintenance.

10. Types of Geothermal Power Plants
Geothermal technology has three varied ways of
taking geothermal energy, they are;
1)Dry Steam Power Plant;
Simplest.
Use steam directly as it comes out.
Suitable when geothermal steam is not mixed with
water.
Efficiency – 30 %.
Efficiency effected by presence of CO and hydrogen
sulphide.
Generates about 35 – 120 MW.

11. Fig. Dry steam power plant

12. 2)Flash Steam Power Plant
Use very hot steam (300° F) and hot water
resources.
Geothermal resource in liquid form.
Liquid changes into steam in flash tank.
Most common type.
Minute amounts of carbon dioxide, nitric
oxide, and sulfur are emitted, but almost 50
times less than at traditional, fossil-fuel power
plants.
Generates about 5 – 100 MW.

13. Fig. Flash steam power plant

14. 3)Binary Cycle Power Plant
Geothermal resource not hot enough to
produce steam.
Or contains too many chemical impurities.
Hot water is passed through a heat exchanger.
Secondary fluid vaporizes, turns the turbines,
which drives the generator.
Remaining fluid is condensed and returned to
the reservoir.
More expensive and has higher efficiency.
Generates about few hundred KW to 5 MW
typically.

15. Fig. Binary steam power plant

16. Complete layout of typical GPP

17. Combined operation of GPP
Composite power system can be supplied more
economically by combination of:
 Base load plant characterized by high fixed
cost and low variable cost.
 Peak load plant characterized by low fixed cost
and high variable cost.
In GPP all production cost are fixed cost, with zero
variable cost.
They are ideally rated as base load plants.
They can achieve annual plant load factor of 90%
or more, more than thermal and nuclear.
It is the least objectionable form of power
generation available at present.

18. Advantages of using Geothermal
Energy
Less area is required
Clean source of power
No fuel is required
Unhindered production of power
Additional capacity
Electrification of the remote places
Saving money

19. Disadvantages of using Geothermal
Energy
Unavailability of large/grouped geysers and hot
spring
Require of experts and expensive drilling
equipments
Construction of roads to faraway sites
Disruption of ground water level
Has environmental impact
Makes the area uninhabitable
Not truly renewable resources
Poor overall efficiency

20. Questions and
Recommendations
??
Presented by:
Sangchu
Pema Dorji
Sangay Dorji
Karma Dugyel
Tshewang Dorji