PASCO Specialty & Mfg. LOW DELTA T STIRLING ENGINE SE-8576A User Manual

I n s t r u c t i o n   S h e e t

012-06870B

®

The PASCO SE-8576A Low Delta T Stirling Engine is a 
jewel-like engine. Because of its precision components and 
careful construction, it can operate on temperature differ-
ences as small as four degrees celsius (4 °C). 

For example, when the room temperature is 22.2 °C (72 °F) 
or cooler, the heat from a warm hand is enough to power the 
engine. 

Stirling engines can be very efficient with some designs 
attaining efficiencies up to 50% of the Carnot Cycle effi-
ciency. The Carnot Cycle determines the maximum theoreti-
cal efficiency of a heat engine according to the formula:

where the temperature is measured in absolute degrees 
(kelvin (K) or rankine). 

The Low Delta T Stirling Engine operates as follows:

The bottom plate of the engine along with the clear acrylic 
cylinder, the top plate, and the graphite power piston make 
up a sealed system. When the air inside this system changes 
temperature, so does the pressure. 

Inside the clear acrylic cylinder is a large white foam dis-
placer. This displacer looks like a piston, but it has a 
3.125 mm (1/8” inch) gap around its outer edge. Air never 
pushes on the displacer; it flows around the displacer.

The engine can begin working when either the bottom plate 
or the top plate is heated or cooled to a temperature at least 
4 °C warmer or cooler than the other plate. A gentle spin on 
the flywheel is needed to start the engine.

As the foam displacer moves away from the warm side of the 
engine, air flows around the edge of the displacer toward the 
warm side and is heated. When the air is heated, it expands, 
which increases the pressure inside the entire engine. This 
increase in air pressure pushes up on the graphite power pis-
ton.

Next, the energy stored in the flywheel moves the displacer 
closer to the warm side of the engine, and the air once again 
flows around the edge of the displacer toward the cool side 
of the engine. 

When the air is cooled, it contracts, and the pressure drops 
throughout the engine. The pressure inside the engine 
becomes less than the pressure outside, and the graphite 
power piston is pushed down. The displacer moves back 
toward the cool side, the air is displaced toward the warm 
side, and the cycle starts all over again.

The foam displacer only moves the air back and forth from 
the warm side to the cool side of the engine. It does not do 
any work on the crankshaft. In other words, the connecting 

temp hot - temp cold

temp hot

--------------------------------------------------

% efficiency

=

Flywheel

Crankshaft

Graphite 

power piston

Foam 

displacer

Connecting 

rod

Connecting 

rod