1. Stirling
Engine

2. History
Inventor: Robert Stirling (1790 -
1878)
Sought to replace the steam
turbines of his days due to frequent
explosion caused by unsustainable
high pressure killing and injuring
workers
Invented Stirling engine in 1816
which could not explode and
produce more power than steam
engine used.

3. What is Stirling Engine ?
Device that converts heat energy to mechanical power by alternately
compressing and expanding a fixed quantity of working fluid at
different temperatures.
Regeneration as alternative.
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4. Why Stirling Engine?
Best teaching and learning for any engineering students device
especially in the field of thermodynamics.
Unique technology.
An innovation with hundreds of application.
An innovation with a mission to save the earth.
Fuel independency.

5. Main Components
• Power piston – small tightly sealed piston that moves up when the gas
inside the engine expands
• Displacer – larger piston and it is very loose in its cylinder so air can move
easily between the heated cooled sections of the engine as the displacer
moves up and down
• These piston move by the action of compression and expansion.
• Difference in pressure causes the piston to move and produce power.

6. Stirling Engine

7. Working Principle
I. One side of the engine is continuously heated while the other side is
continuously cooled.
II. First, the air moves to the hot side, where it is heated and it expands
pushing up on a piston.
III. Then the air moves through the regenerator to the cold side, where it
cools off and contracts pulling down on the piston.
IV. Temperature change inside the engine produces the pressure change
needed to push on the piston and make the engine run.

8. Configurations
There are three major types of Stirling engines, that are distinguished
by the way they move the air between the hot and cold areas:
• The alpha configuration
• The beta configuration
• The gamma configuration

9. The alpha configuration
• There are two cylinders.
• The expansion cylinder (red) is
maintained at a high temperature
• while the compression cylinder (blue)
is cooled.
• The passage between the two
cylinders contains the regenerator.

10. Beta type Stirling engine
• There is only one cylinder, hot at
one end and cold at the other.
• A loose fitting displacer shunts
the air between the hot and
cold ends of the cylinder.
• A power piston at the end of the
cylinder drives the flywheel.

11. The gamma configuration
• The Stirling gamma configuration
is simply a Stirling beta engine in
which the power piston is not
mounted coaxially with the
displacer piston but in a separate
cylinder.
• This avoids the complications of
the of the displacer piston linkage
passing through the power piston.

12. Double - Acting Stirling (Swash Plate) Engine
• This configuration has fewer mechanical parts than the other designs
and is more suitable for higher power applications.

13. Efficiency
Theoretically
 Stirling engine efficiency = Carnot efficiency
 Unfortunately working fluid or gas is not ideal this causes the
efficiency to be lower than Carnot efficiency.
 In fact, Stirling engine efficiency depends on
 Temperature ratio (proportionally)
 Pressure ratio (inversely proportional)
 Specific heat ratio (inversely proportional)

14. Advantages
Various heat sources (solar, geothermal, nuclear energy, waste heat, biological)
Environmental friendly
Heat is external and the burning of a fuel-air mixture can be more accurately
controlled.
Operates at relatively low pressure and thus are much safer than typical steam
turbines
Less manpower needed to operate any type of commercial Stirling engine.

15. Disadvantages
• The price : its cost is probably the most important problem, it is not yet
competitive with other means well established.
• The ignorance of this type of engine by the general public. Only a few
fans know it exists. It is therefore necessary to promote it.
• The variety of models prevents standardization and, consequently,
lower prices.
• Sealing problems
• Heat transfers with a gas are delicate and often require bulky
apparatuses.
• The lack of flexibility.

16. Applications
Water pump stations
Combined heat and power plant
Solar power generation
Stirling cyrocoolers
Heat pump
Marine engines
Nuclear power
Aircraft engines
Micro CHP
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17. Applications
WATER PUMP STATION
 A Stirling engine used for pumping water
can be configured so that the water cools
the compression space. This is most
effective when pumping cold water.

18. Applications
STIRLING CYROCOOLERS
 Any Stirling engine will also work in reverse as a heat pump. When
a motion is applied to the shaft, a temperature difference appears
between the reservoirs.
 NUCLEAR POWER
 Replacing the steam turbines of the nuclear power plant with
Stirling engine might simplify the plant, yield greater efficiency,
and reduce the radioactivity by products.

19. Conclusion
• The Stirling engine is noted for its high efficiency compared to steam
engines, quiet operation, and the ease with which it can use almost
any heat source.
• This engine is currently exciting interest as the core component of
micro combined heat and power (CHP) units, in which it is more
efficient and safer than a comparable steam engine.
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