Following the time-honored YouTube tradition of ordering cheap stuff online and playing with it while the camera runs, [Monta Elkins] bought a Stirling engine that drives a DC motor used as a generator. How much electrical juice can this thing provide, running on just denatured alcohol? (Will it blend?)
The answer is probably not really a spoiler: it generates enough to run “Blink.ino” on a stock Arduino, at least when powered directly through the 5 V rail. [Monta] recorded an open-circuit voltage of around 5 V, and a short-circuit current of around 100 mA at a measured few hundred millivolts. While he didn’t log enough of the points in-between to make a real power curve, we’re guessing the generator might be a better match for 3.3 V electronics. The real question is whether or not it can handle the peaky demands of an ESP8266. Serious questions, indeed!
The video is a tad long, but it’s more than made up for by the sight of an open flame vibro-botting itself across his desk while [Monta] is trying to cool the cold side down with a melting ice cube. Which got us thinking, naturally. If you just had two of the Stirling engines…
Probably easier to get the same amount of power from a peltier stove.
The thing that Peltier elements generate most is hacker’s tears:
http://hackaday.com/2016/05/19/beautiful-kegerator-built-the-hard-way/
I don’t know anything about this particular Stirling engine, but supposedly they can be built to be around 2x as efficient as internal-combustion engines, so in the 50% range. The tradeoff is size, vibration, cost, and maintenance. But for scooting around your desk, they’re ideal!
My impression is that thermoelectric generators are in the 10% range and lower. If you don’t want the hassle of a Stirling engine, or the size or weight or… then by all means. But bear in mind that you’ll need a 5x bigger fire to compensate.
Actually most efficient internal combustion engine is more than 50%
The flame in the video clip is easily 75 Watt, so a 10% TEG should do a lot better than what he has right now.
75W with 80% of the heat missing the end of the tube.
“I don’t know anything about this particular Stirling engine, but supposedly they can be built to be around 2x as efficient as internal-combustion engines, so in the 50% range. ” – The 50% is true only for machines with very high pressures and temperatures. I agree that the flame in the video will have least 75W (most likely more), so the efficiency of such models is not more than one percent or so. Still, kind of impressive that the arduino runs.
From the linked article: “… a comment I had seen somewhere on the Internet began to sink in: all projects involving peltier devices ultimately end in disappointment.“
I’m going to disagree – they’re not even close to energy efficient, but we use them for spot-cooling in the lab and are cheap, handy and tiny. Also good for demonstrations in front of semi-comatose undergrads.
This post isn’t a disappointment either – it powers something (and seems to indicate that AvE has permanently broken the boring video-narration barrier), which is all it was intended to do.
If you want real power generation from a Stirling, stand in line – a whole succession of manufacturers from Dean Kamen’s partnership with Deka to Victron’s “Whisper Gen” have gone on their face economically with really well-done Stirling generators. People would rather spend thousands less for the generating device and just put up with the noise and exhaust of an I/C engine, or they go to cheap solar panels plus Tesla-esque battery banks which are completely quiet with little waste heat to deal with (and usually a tax break in the mix).
Stirling computes, it just doesn’t compete.
Small Sterling engines aren’t very efficient, neither are TEGs. If you just use a standard Peltier element you get 4% out as electricity. Purposebuildt TEG elements are better though. What about an alcohol fuel cell?
https://www.youtube.com/watch?v=XsD8aI6nPV0
Probably easier to get the same amount of power from the wall plug.
You know.. the route is the goal and such…
I assume the goal is to convert a flame into electricity.
If the goal is specifically to convert ethanol to electricity though, fuel cell might do better.
Heat to electricity. The AVR chip can run from 1.8V to 6V, so even with the slightly dynamic input it can still run. But power draw wise, the MSP430 would be a better fit.
Would be cool to control the flame fuel flow from the microcontroller. Not sure how well the AVR could measure it’s own voltage compared to the internal static reference.
dald: As long as the input voltage is high enough to cover the dropout voltage for the internal reference, there should be no problem having it measure its own voltage. You could then write the program such that it goes to sleep whenever the voltage drops below a threshold, waking up every second or so just to check the voltage. This gives the engine time to build up some revs in its flywheel. And like you say, you can also use the controller to regulate the flame, perhaps with a kerosene lamp type of wick adjuster connected to a servo.
If the goal is to convert ethanol to electricity, there is an easier way. Drink ethanol, turn generator (with something like a hand crank or a generator on a bicycle). Also not very efficient, but you get to consume the ethanol.
How hard is it to un-de-nature industrial ethanol?
“How hard is it to un-de-nature industrial ethanol?”
Pretty hard. Of course it depends on what they denature it with, but from what I’ve read, the most common denaturant is gasoline, but there are also other poisons used with boiling temperatures close to that of ethanol. Bottom line is, it’s easier to ferment and distill ethanol than to clean up denatured ethanol. This is by design – the only way industry could produce ethanol and not pay the liquor tax was to prove to the treasury department that they could make it undrinkable, even to hackers. I’m sure if you had a good enough fraction still (a pot still would not do it, no matter how many times you ran it through), you could separate the ethanol from the poison, but like I said, easier (and safer) to start from scratch.
So what you’re saying is that you need to find an osmosis membrane to differentiate the molecular sizes….
https://www.pelam.de/product_info.php?cPath=28_109&products_id=530
FlameDuino? An Arduino can’t any more “steam punk” than that.
Floats my boat :-)
Maybe a FlameShield……………..
It would be more steam punk, if it used steam.
I should see if my dad still has some Mammod engines, fire up a Mammoduino.
Ethanol? I would rather drink it.
I think it’s denatured / poisoned. You have to pay tax on it unless they add the poison. Humans are very strange.
Hook the arduino up to a magneto on a bike, drink your alcohol & pedal. Still alcohol powered.
:)
Though he says rubbing alcohol, which would most commonly be IPA here.
It would be cool to see a MPP connected to it and estimate the power.
Why does the it slow down more with the LED reversed? Shouldn’t it not conduct at all and therefore not slow down the engine?
That’s because it is not really just an LED. Notice the changing colors and blinking. There’s a whole integrated circuit die of some sort inside that LED like package which supports those features. I couldn’t tell you much about what the actual schematic of that device would look like but it is not a simple diode and that is why it conducts in reverse.
Because that’s not just an LED. It’s a pair of red and blue LEDs being driven by an electronic circuit. That circuit has a reverse diode in parallel with it to protect the circuit from being powered backward.
Nice. It looks like the flame could be reduced somewhat and still get lots of output. I wonder if tea light candles would be suitable as a heat source?
I have one of the sit-on-your-hot-coffee Stirling engines, but it doesn’t drive anything. Except my imagination.
Because of the “butterfly effect”, theres no predicting how your hot-coffee Stirling engine has altered the course of history. You comment about it for one, and the wave of people reading about it… ;)
Yah, I nearly had the cure for canceraids then was like “Ooo, new comment.”
I have a Arduino connect to my car, probably qualifys as a gasoline powered Arduino. It’s also a plug in hybrid, which brings it full circle back to electrical powered. The grid I’m on is nuclear, solar and natural gas powered. This seems like a stretch, now if the Arduino could do something electronic engineery for the engine that would be cool.
You mean it isn’t running an MPG gauge? DAGS MPGduino.
I prefer to be ethanol powered myself :)
Agree. Ethanol, or methane, depending on age.