Sri Ramakrishna College of Arts & Science, Coimbatore, Department of Physics

1. Geothermal Resources
UNIT IV

2. GTS
Geothermal resources are reservoirs of hot water / Steam that exists at varying temperatures and depths
below the Earth's surface.
There are three geothermal power plant technologies being used to convert hydrothermal fluids to
electricity - The type of conversion used (selected in development) depends on the state of the fluid (steam
or water) and its temperature.
Dry steam,
Flash steam and
Binary cycle.

3. Hydrothermal Resources
Hydrothermal, refers to heated water resources, which can be found in
hydrothermal resources that are naturally occurring.
They are created by groundwater and favorable rock characteristics,
such as open fractures or fissures, that allow the flow of fluids between.
With the high(er) temperatures of the rocks, the fluids are heated and
can be derived either as hot water or steam, if the temperature is high
enough. So the fluid, or steam carry the heat which can then be used on
the surface for either heat applications, or for electricity generation.
These hydrothermal resources range in temperature from a few degrees
above the ambient conditions on the surface to temperatures beyond
350 degrees Celsius.
Hydrothermal resources can be found in volcanic settings (such as in
Indonesia), in sedimentary settings (such as the German Molasse Basin)
and hot wet rocks (e.g. fractured granite with water resources).

4. Geothermal System

5. Geothermal Sources
Hydrothermal convective system
o Vapour Dominated System – Dry Steam field
o Liquid Dominated System – Wet Steam Fields
o Hot-Water fields
Geopressured resources
Petro-thermal or Hot Dry rocks
Magma Resources
Volcanoes

6. Dry
Steam
Power
Plant

7. Dry Steam Power Plant
Dry steam plants use hydrothermal fluids that are primarily steam.
The steam travels directly to a turbine, which drives a generator that
produces electricity. The steam eliminates the need to burn fossil fuels to
run the turbine (also eliminating the need to transport and store fuels).
These plants emit only excess steam and very minor amounts of gases.
Dry steam power plants systems were the first type of geothermal power
generation plants built (they were first used at Lardarello in Italy in 1904).
Steam technology is still effective today at currently in use at The
Geysers in northern California, the world's largest single source of
geothermal power.

8. Flash
Steam
Power
Plant

9. Flash Steam Power Plant
Flash steam plants are the most common type of geothermal
power generation plants in operation today.
Fluid at temperatures greater than 360°F (182°C) is pumped under
high pressure into a tank at the surface held at a much lower
pressure, causing some of the fluid to rapidly vaporize, or "flash."
The vapor then drives a turbine, which drives a generator.
If any liquid remains in the tank, it can be flashed again in a second
tank to extract even more energy.

10. Binary
Cycle
Power
Plant

11. Binary Cycle Power Plant
Binary cycle geothermal power generation plants differ from Dry Steam and Flash
Steam systems in that the water or steam from the geothermal reservoir never comes
in contact with the turbine/generator units.
Low to moderately heated (below 400°F) geothermal fluid and a secondary (hence,
"binary") fluid with a much lower boiling point that water pass through a heat
exchanger.
Heat from the geothermal fluid causes the secondary fluid to flash to vapor, which
then drives the turbines and subsequently, the generators.
Binary cycle power plants are closed-loop systems, and virtually nothing (except water
vapor) is emitted to the atmosphere.
Because resources below 300°F represent the most common geothermal resource, a
significant proportion of geothermal electricity in the future could come from binary-
cycle plants.

12. Advantages
Cost effective
Reliable and stable
Sustainable
Environment friendly
It is immune to fuel cost fluctuations
It is renewable
Low emissions
High efficiency of energy conversion
Little maintenance of the system
Very less noise pollution
Independent on weather unlike solar energy
Massive potential
Small land footprint
Clean source of energy

13. Disadvantages
Drilling and exploitation of it is
expensive
Environmental concerns due to
release of greenhouse gases during
extraction
Land requirement for geothermal
system installation is high
Geothermal power plants may
affect stability of land
Cost of power produced is high
It is location specific
Energy transportation cost is high
since geothermal power plants are
often located on remote locations
Pumps required for extracting it
may require external power, which
may possibly come from burning
fossil fuels

14. Applications
Important applications of geothermal energy are :
Space heating and cooling.
Generation of electrical power.
Industrial process heat.
Other applications includes desalination of water, heavy water production, extraction
of minerals from geothermal fluids, timber seasoning etc.
However, the geothermal energy is presently utilized mainly for power generation and
space heating purposes only.

15. CHEMICAL ENERGY
Unit IV

16. CHEMICAL ENERGY
• Involves development of fuel cells and batteries for
• Running small and commercial vehicles in the beginning and then heavy
vehicles
• Rural(100-500 population) electrification through rechargeable batteries
(windmills)
• The Department of Non Conventional Energy Sources (DNES) is promoting
R&D in chemical and electrochemical sources of energy

17. FUEL CELLS
A fuel cell uses the chemical energy of hydrogen or other fuels to cleanly and efficiently produce
electricity.
If hydrogen is the fuel, the only products are electricity, water, and heat.
Fuel cells are unique in terms of the variety of their potential applications; they can use a wide
fuels and feedstocks and can provide power for systems as large as a utility power station and as
a laptop computer.
Fuel cells can be used in a wide range of applications, providing power for applications across
sectors, including transportation, industrial/commercial/residential buildings, and long-term
storage for the grid in reversible systems.

18. COMPONENTS OF A
FUEL CELL
• Fuel Electrode – Anode
• Oxidant or Air Electrode – Cathode
• Electrolyte
• Electrodes – Porous –Nickel and
Carbon are generally used Pl can
can also be used

19. FUEL CELL WORKING
Fuel cells work like
batteries, but they do
not run down or need
recharging.
They produce
electricity and heat as
long as fuel is
supplied.
A fuel cell consists of two
electrodes—a negative
electrode (or anode) and
a positive electrode (or
cathode)—sandwiched
around an electrolyte.
A fuel, such as
hydrogen, is fed to the
anode, and air is fed to
the cathode.
In a hydrogen fuel cell, a
catalyst at the anode
separates hydrogen
molecules into protons
and electrons, which take
different paths to the
cathode.
The electrons go
through an external
circuit, creating a flow
of electricity.
The protons migrate
through the electrolyte to
the cathode, where they
unite with oxygen and the
electrons to produce
water and heat

20. HYDROGEN PRODUCTION
• To produce hydrogen, it must be separated from the other elements in the
molecules where it occurs. There are many different sources of hydrogen and ways
for producing it for use as a fuel.
• Thermochemical Processes.
• Electrolytic Processes.
• Direct Solar Water Splitting Processes.
• Biological Processes.

21. THERMOCHEMICAL PROCESS
Thermoche
mical
Processes
Westinghouse
electrochemica
thermal sulfur
cycle
Ispra Mark 13
cycle
Iodine-Sulphur
cycle
Fossil Fuel
Methods
Solar Energy
Methods
• Bio Photolysis
• Photo
electrolysis
Some thermal processes use the energy in various resources, such as natural gas, coal, or biomass, to
release hydrogen from their molecular structure.

22. HYDROGEN
PRODUCTION
CYCLES
• Possible thermal reactions which could
yield hydrogen are given

23. ELECTROLYTIC PROCESSES
Electrolysis
Tank Type
Electrolyzer
Filter Press
Electrolyzer

24. DIRECT
SOLAR
WATER
SPLITTING
PROCESSES
Bio photolysis is the production of hydrogen from water by
sunlight energy using biological systems.
Several approaches are possible using either isolated cellular
components or algae cultures.
Technical and economic considerations restrict practical
applications to algae cultures
The only algae system demonstrated to meet the basic
requirements of bio photolysis uses nitrogen starved
cultures of nitrogen–fixing heterocystous blue–green algae.
Photosynthetic bacteria could be used for hydrogen
production from wastes.
Biophotolysis and photofermentation are biochemical
reactions driven by photonic energy to produce hydrogen by
using water as the material resource.

25. DIRECT SOLAR WATER SPLITTING
PROCESSES
Photoelectrolysis describes electrolysis by the direct
use of light; that is to say, the conversion of light into
electrical current and then the transformation of a
chemical entity (H2O, H2S, etc.) into useful chemical
energy (such as H2) using that current
In photoelectrochemical (PEC) water splitting,
hydrogen is produced from water using sunlight and
specialized semiconductors called
photoelectrochemical materials, which use light
energy to directly dissociate water molecules into
hydrogen and oxygen.

26. HYDROGEN TECHNOLOGY
DEVELOPMENT IN INDIA
• Department of Non-Conventional Energy Sources – supported 22 R&D projects
• Production of hydrogen by photo electrolysis of water using solar energy
• Production of hydrogen blue green algae and by certain bacterial species
• Storage of hydrogen through metal halides/ non-metal hydrides
• Problems relating to utilization of hydrogen as fuel – development of suitable engine /
burner etc
• Liquid hydrogen production, utilisation and

27. ADVANTAGES
Fuel cells can operate at higher efficiencies than
combustion engines and can convert the
chemical energy in the fuel directly to electrical
energy with efficiencies capable of exceeding
60%.
Fuel cells have lower or zero emissions
compared to combustion engines.
Hydrogen fuel cells emit only water, addressing
critical climate challenges as there are no
carbon dioxide emissions.
There also are no air pollutants that create
smog and cause health problems at the point
of operation.
Fuel cells are quiet during operation as they
have few moving parts.