1. Stirling Motor
Displacer Piston Controller
Project Sponser; EcoGen
Contact; Alan Holsapple

2. The Technology
• EcoGen is developing a novel Stirling Motor
based on a patent pending technology which
promises to increase the efficiency of the
motor relative to current production engines
while decreasing the manufacturing costs
dramatically.

3. Stirling Engines
• External combustion, flexible fuel source
• Closed cycle, helium or H2 working gas
Robert Stirling patented this hot air • High thermal efficiency
engine with economizer (regenerator)
in the early 19th century. • Low noise and vibration
Historically, cheap IC engines have
displaced nearly all engine • Low maintainence
applications, however due to it’s high • Low emissions
efficiency, the Stirling is making a
comeback. • High cost of manufacturing
The free piston Stirling developed by
Infinia Corp at right is being used for
m-CHP applications, and others are
being developed for high efficiency
power generation applications .
The high cost of manufacturing is a
key inhibitor to the mass scale
commercialization of the Stirling
engine.

4. EcoGen’s Motor Description

5. Induction Control Coil
• Circumferential orientation at cylinder wall
• PM’s embedded in Displacer
• Current; pos / neg (act as motor / generator)
• Simple, low cost materials

6. Displacer X-Section
• Graphalloy bearings
• Haxagonal alignment
• Stacked Perf-plate or
brazed tube design
• Mock regenerator
with porous material

7. Control Algorithm
• Cold Start / ramp frequency
• Run / bracket frequency
• Retard or advance phase angle
• Shut down cycle, soak back protection

8. PLC and Power Electronics
• Power requirements
• Feedback signal analysis
• PWM vs FM or other current control
• The primary function of the controller is to
align the frequency of the displacer relative to
the power piston

9. Project Goals
• Prototype hardware configuration for
displacer piston controller
• Preliminary algorithm for prototype motor
control
• Spring size / rate down select
• Test data, results and report