Solar-Miller (tm) configuration of Stirling engine. The regenerators (inside between displacer and crankshaft) and radiator ( on top of the two displacers drawn in red) have been removed for clarity.
Support this project directly at paypal.me/CleanStirling
|Note how all moving parts are
enclosed and protected from dust, dirt, combustion products, heat, mold
||Certain details that allow this design to function have been withheld
most efficient working fluid is hydrogen gas. Most any gas
work. Avoid using air with oxygen, because it combines with
lubricants and then burns explosively.
|Note also, how this engine was
designed as a pressure vessel to work at high power densities.
||Contribute to funding the building of this engine paypal.me/CleanStirling
If you are unfamiliar with
the Stirling engine, use
search engine and you will discover that the Stirling engine is a very
promising technology that has never lived up to its potential because
of the high costs to manufacture, the low power output, and the
unresponsiveness of the engines. This design solves the power
density and costs issues.
These engines prefer to
run at one continuous speed which is
only moderately influenced by fuel input. Do not expect to
your Stirling engine. Consequently, do not attempt to utilize
Stirling engine where there is the need for sudden acceleration, such
as in non hybrid cars or aircraft. You don't want to be
your homebuilt airplane, stall, and then expect the Stirling engine to
save you. The response is simply too slow. Non
aircraft propulsion is the best example of the wrong application for
this engine. Instead, choose the right application and you
love the economy and quiet operation that are the hallmark of the
Imagine an engine that
runs without the noise
fuel exploding out of the exhaust valves, instead, the fuel is burned
quietly similar to a gas log fireplace or your water heater.
complex plumbing of either fuel or air supply is needed. The
and fuel follow simple plumbing to the area where the heat is needed,
they combine continuously, efficiently, completely, cleanly and the
gases are then plumbed away. No complex ignition system or
circuits are required. With the Stirling's
flow, air and fuel valves don't open and close every time the
piston completes a stroke. Instead of controlling air, fuel,
each stroke of the piston, the Stirling controls the heat energy of the
fuel after the fuel and air are combined. Moving the working
inside from the heating area to the cooling area is much simpler and
more efficient than creating heat exactly where and when it is needed
for each stroke of the piston and then wasting most of it out the
exhaust ports. This is the most difficult part of
Stirling operation to grasp; Air can be heated and cooled
(causing expansion and contraction) over 1500 times a minute.
Search u tube.com for videos that prove that this is true and that
engines actually work. Once you grasp this concept, the
Stirling's simplicity will enchant the engineer in you.
The internal combustion engine has, until now, overshadowed the Stirling engine in performance with the ability to process chemical energy into motion at a much higher rate and in a more compact form. A four cylinder gasoline powered internal combustion engine can convert a gallon of gas into work in under 15 minutes. The Stirling engine has always had a bottleneck in the energy input that prevented compact high volume throughput of energy. This design directly addresses that bottleneck as well as some of the complexities that made the Stirling engine expensive to produce.
A traditional design for reference.
compare to the internal combustion engine.
Fewer parts finaly means lower costs, (just as soon as we get the volume )
Parts that the Stirling engine doesn't need:
seperate starter, (utilizes the alternator),
fuel injection system (burns like a Coleman (R) stove),
complex ignition system (just one piezo electric spark to start the heat source),
high pressure fuel pump,
oil pressure monitor,
check engine light,
catalytic converter ( catalyst used in combustion area),
Maintenance that the Stirling doesn't need:
spark plug changes,
timing belts, valve adjustments,
check engine light
Stirling engines run on any heat source, from geothermal to solar to propane to wood. Anything that produces heat can potentially power this engine. Consequently, if you have waste heat, why not use it to power your lights and heat your water?
Stirling engines are quiet and reliable. If you need a portable generator for a mobile home, off the grid homes and offices or trade shows, consider the Stirling. The cooling cycle of the engine can be plumbed to provide you with hot water.
a Stirling engine in reverse, causes it to pump
heat from the hot side to the cold side. This is how
cryocoolers work to convert air into a liquid. This design
used as a heat pump, either cooling or heating fluids as
If you have need of refrigeration and don't have electricity, this
design can be adapted to produce power from fuel on one side and heat
pumping on the other. If you have a noise issue with
refrigeration, or want to use non polluting refrigerant gases , this
might be the ticket.
Just as important as when Stirling engines make sense is
recognizing when they don't. Stirlings are only moderately
responsive to fuel input. Do not use this engine where
responsiveness is an issue.
Possible engine fuel source
"...it was a pit fire with poop. The pot doesn't smell like poop, it smells like a mesquite fire because the cows like to eat the mesquite beans from the trees."
The Stirling engine has been around in various forms since 1817 when Robert Stirling patented his first design. Even earlier variations of this device are speculated to have been employed to move massive doors in Roman temples over 2000 years ago. Current designs are found in cryocooling, home energy generation, solar power generation, submarine propulsion, and space craft power generation. Attempts to utilize the Stirling engine in automobiles were unsuccessful. This may have been due to a tendency to treat the Stirling engine as a poor substitute for the internal combustion engine. A more appropriate alternative is to treat the Stirling engine as a unique power source; certainly, its distinctive characteristics recommend it to a variety of applications entirely outside the realm of the internal combustion engine. Just as the electric motor and the turbine are each uniquely suited for certain tasks, so too is the sterling engine. Two variables have heretofore inhibited the widespread adoption of the Stirling engine - cost and power density. Lower manufacturing costs and increased power output, give the Solar-Miller (tm) Stirling engine a competitive edge over all previous applications..
A quick word on maintenance and repair. little. That is right, these engines are sealed at the factory, you can't open them beyond re-pressurizing the working gas. The bearings are located away from the heat source and have very little stress on them. The output shaft seal, if you are using a sealed one can be changed without accessing the inside of the engine. If you manage to break the output shaft, or drop something on the case that bends it, or drill a hole into it, well, they don't cost that much. On the other hand, if you recover the engine after it has been submerged in water, simply hose it off and you are good to go.
And they are designed to be recycled.
Simply eliminate the
bottleneck to power input and
the extra parts. The Stirling engine was designed in 1817
two pistons, which requires multiple seals and actuators while limiting
the surface area which can transmit heat to the working fluid.
This design rotates the displacer instead of reciprocating it.Suddenly there is no more limit on the surface area for heat energy transfer, no springs, no internal seals, no separate actuators, no reason not to power both sides of the power piston, no exposed external moving parts and only one external seal on the output shaft which can itself be sealed with an internal alternator.
concept by Robert Stirling
Solar Miller Layout
Heat transfer area is in red
The displacers are in
red. The heat transfer area is the entire length of the
A simple redesign has eliminated most of the problems of a Stirling engine. Power output can be formally addressed at each step of the power conversion process and the layout easily customized to the job. Stirling engines convert heat into mechanical motion. This design allows the heat exchanger to be optimized for the heat source and the stroke adjusted to achieve the desired torque. Applications in which even power output and high efficiency, such as the hybrid automobile and electricity generation, are ideal for the Stirling engine as well as new applications like distillation and refrigeration. The internal combustion engine, the electric motor and the turbine all have their market niches. And now the Stirling is ready for a larger role
@ gmail. com (omit the spaces)
|Hobbyists, drop us a note to show how you are doing. More detailed plans are available for a nominal fee.|
|fractalogic @ gmail. com (omit spaces)|
Copyright (c) 2011
|Predict in horsepower, the power output of a Solar-Miller (tm) Style Stirling Engine|
|Change the green boxes to achieve the desired output|
|Fill Pressure PSI||0||200||500||psi|
|Heat exchanger length||25|
|Swept Volume||156.25||Cubic inch||2.56||liter|
|Dead space||20||Cubic inch||0.33||liter|
|Volume @||TDC||176.3||Cubic inch||2.89||liter|
|@||1/2 way||232.8||Cubic inch||3.81||liter|
|Piston Position||Pressure Delta|
|temp drop from moving piston|
|What temp alone would do this||TDC||149.08||149.08||149.08|
|pressure differential on piston|
|cold||Delta other side of piston||(Mechanically equalized Miller cycle)|
|P=nRT/V||fill pressure 1||fill pressure 2||Fill pressure 3|
|cycle||PSI||Delta PSI||PSI||Delta PSI||PSI||Delta PSI|
|Pressure on piston||Area||28.3||Sq In||SI|
|psi in foot/lbs for 1/6 of rotation|
|Efficiency||21%||=||mech x||heat trans x||Carnot|
|Wild As Guess||(Th-Tc)/Th|
|1 HP = 33000 ft/lbs/min||33000|
|1 mole= 24.47 liter at 25 deg C (298K)|
|1 cubic inches =||0.01639||liter|
|1 linear inch=||2.54||cm|