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Laser Powered Stirling Engine

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RussW

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I am working on a project to laser heat a Stirling Engine with a generator mounted to it. I have available 4.5 to 5 VDC and 20 mA. What parts would give me the highest temperarure beam? I am not too concerned about cost in trying to prove a concept but I am financing this out of my own pocket. It has been explained to me that the beam itself has no temperature until the photons have been absorbed. Any advice on how to achieve the highest temperature with only 5 vdc and 20 mA would be most appreciated.
 
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bobhaha

bobhaha

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Why are you restricted to 20mA? A typical laser diode will need to be running >100mA to even produce enough heat to sting the skin.

You would be looking at anywhere from 3 - 5W laser output in order to heat the medium (possibly water) enough to turn to steam, while also counteracting heat dissipation due to the water tank acting as a heat sink and also to heat the mass fast enough for use in a model.

Of course this all depends on size...

You will need to explain a little better what your intentions are... (size, material, etc...) and increase your current range if you would like a chance to get this to work.

-Adrian
 
lasersbee

lasersbee

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If your setup was 100% efficient... 5V @ 20mA = 0.1 Watts......

You may need to push the wattage a bit higher depending
on the power requirements of your particular Stirling Engine.

@ Bob...
A Stirling Engine can use heat directly... no need to boil water
to create pressure like a Steam Engine... ;)


Jerry
 
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Bluefan

Bluefan

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Laser diodes usually have an efficiency less than 50%, it would actually be more efficient to use the heat from the laser diode and and let the light escape than the other way around.
 
rhd

rhd

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It's an interesting project -

What I'm not clear on is whether you were wanting to use lasers to POWER the engine, or were looking to use the engine to power a laser. The desired spec of "4.5 to 5 VDC and 20 mA" makes me think that you were hoping to use the engine's electrical output (some generate electricity via a small motor) to power a laser? Many of the stirling engine kits I've seen power a small LED with the electricity they generate, and the specs of those LEDs are probably similar to the parameters you gave. You weren't hoping for a self-sustaining (free energy) build were you? ;)

At any rate, if you're just trying to power the engine itself, I think it would be doable (and cool looking) with a couple 445nm lasers running at ~1.5W each. Depending on your engine design, you'll probably want to have the heat-input area painted black, so that it transfers as much of the beam's power as possible.
 
bobhaha

bobhaha

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lasersbee said:
If your setup was 100% efficient... 5V @ 20mA = 0.1 Watts......

You may need to push the wattage a bit higher depending
on the power requirements of your particular Stirling Engine.

@ Bob...
A Stirling Engine can use heat directly... no need to boil water
to create pressure like a Steam Engine... ;)


Jerry
Click to expand...

Oh man... and I knew that too! :banghead: I must have been distracted.... Yeah we'll go with that!

Thanks Jerry
 
Benm

Benm

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RussW said:
Any advice on how to achieve the highest temperature with only 5 vdc and 20 mA would be most appreciated.
Click to expand...

Glue a 25 ohm resistor to the hot part of your stirling engine and apply voltage.

If you must use a laser you could shine it onto the hot part (after painting that black), but the efficiency of lasers at these power levels is very low - at 5V/20mA i'd expect 5 mW optical power at best... not much compared to the 100 mW the resistor delivers.
 
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RussW

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According to the videos we may be able to get 100 mA. Here are some videos to help explain.

http://www.youtube.com/watch?v=IDu1kbS9GhY

http://www.youtube.com/watch?v=-8G4GgryJZQ

Variation of KYG stirling engine - YouTube

http://www.youtube.com/watch?v=euG6PssT5pc&feature=mfu_in_order&list=UL

http://www.youtube.com/watch?v=aTq6nBCJyVg&feature=mfu_in_order&list=UL

ƒXƒ^�[ƒŠƒ“ƒOƒTƒCƒNƒ‹�EƒIƒ“ƒ‰ƒCƒ“

I don't think we are talking perpetual because we are operating using a temperature differential which would use the ambient air temperature as a form of potential energy.

Once again thanks for the info and any advice is appreciated.

Just as a reminder we are looking for the most heat with maybe 100mA and 5 vdc.

Also I am a novice to the world of lasers so please forgive my ignorance.
 
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Bionic-Badger

Bionic-Badger

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100mA is not going to produce much power, probably not even enough to burn or even hurt your skin. People can barely pop black balloons with weak lasers like that. You'll need a laser that is a few orders of magnitude more powerful to run something like at Stirling engine, at least one the size of the one you've shown.

To give you a better picture of how much energy is needed, here is a Stirling engine running via a large Fresnel lens and sunlight:


That Fresnel lens is about 1 m^2 in area, which means it is essentially concentrating a kilowatt of energy onto that spot to cause the Stirling engine to operate, much of which is far infrared heat energy, not just visible light.

Compare that to your 5V 100mA laser at 100% efficiency, which is 0.5W. Half a watt is more than three orders of magnitude less powerful than the output of that Fresnel lens above. You're not going to cause any Stirling engine to operate short of one smaller than a thumbtack--if you could manufacture one.
 
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millirad

millirad

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The smaller the stirling engine is and the more powerful the radiant source, will determine whether you sink or swim. ;-)
 
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millirad

millirad

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Here's something related...............................

Single particle is the smallest Stirling engine yet - physics-math - 12 December 2011 - New Scientist

The 200-year-old Stirling engine has inspired a power generator made of a single particle just 3 micrometres wide.

Overshadowed by its steam and internal combustion brethren, the Stirling engine is a quiet, efficient alternative that compresses a fixed amount of gas inside a cylinder.

As it is compressed, the gas heats up and expands, pushing a piston, before cooling due to the loss of energy, only to be compressed again.

In their tiny mimic, Clemens Bechinger and Valentin Blickle at the University of Stuttgart, Germany, replaced the cylinder with a laser that confines the motion of a 3-micrometre-wide lump of melamine in water.
Pent-up particle

A zap of heat from another laser builds up tension in this optical "trap": like a compressed gas, the particle is aching to break free. Widening the trap by modifying the first laser lets it do so, expending the pent-up energy.

"The use of a laser source to provide the required rapid localised heating on the microscopic scale appears to be novel," says Alan Tucker, leader of the Stirling Cycle Research Group at the University of Canterbury in Christchurch, New Zealand. He calls the technique sophisticated but says that he "struggles" to envision any practical applications.

But Bechinger says that the microscopic engine is allowing his team to investigate the balance between maximum power and maximum efficiency on the nanoscale – which could in turn inform the design of future micromechanical machines.

Journal Reference: Nature Physics, DOI: 10.1038/nphys2163
Click to expand...
 
Bluefan

Bluefan

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I've seen a stirling engine run sitting op top of a cup of hot water. 0.5W is still too little, but not 3 orders of magnitude off.
 
Bionic-Badger

Bionic-Badger

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It definitely depends on the size of the engine. The Stirling engine running on a cup of hot water was tiny and with a large surface area on top of the cup. Plus water takes quite a bit of energy to bring up to temp. If you're going to run one like the solar video above, you're still looking at a kilowatt.
 
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