Siphons are one of those physics phenomena that, like gyroscopes, non-Newtonian fluids, and electricity, seem almost magical. Thanks to atmospheric pressure, simply filling a tube with liquid and placing the end of the tube below the liquid level of a container allows it to flow against gravity, over a barrier, and down into another container without any extra energy inputs once the siphon is started. They’re not just tricks, though; siphons have practical applications as well, such as in siphon-powered hydroelectric turbine.
This is an iteration of [Beyond the Print]’s efforts to draw useful energy from a local dam with an uneconomic amount of water pressure and/or volume for a typical hydroelectric power station. One of his earlier attempts involved a water wheel but this siphon-based device uses a more efficient impeller design instead, and it also keeps the generator dry as well. Using 3″ PVC piping to channel the siphon, as well as a short length of thinner pipe to attach a shop vac for priming the siphon, water is drawn from the reservoir, up the pipe, and then down through the impeller which spins a small DC generator.
This design is generating about 9 V open-circuit, and we’d assume there’s enough power available to charge a phone or power a small microcontroller device. However, there’s a ton of room for improvement here. The major problem [Beyond the Print] is currently experiencing is getting air into the system and having the siphon broken, which he’s solved temporarily by adding a bucket at the outflow. This slows down the water though, so perhaps with any air leaks mitigated the power generation capabilities will be greatly increased.
for maximum throughput he needs that generator and turbine near the exit to the siphon. Let Gravity do the work.
When you’re pumpin’ you gottta work that head 😛😛😛
i am not that sure. Speed is probably constant in the pipe else there would be a vacuum somewhere.
That’s the thing, the length under the pump (head) causes a low pressure area just below the impeller which, when it approaches net positive suction head, will cause cavitation/boiling, which then destroys efficiency. If you put the impeller near the bottom you don’t need to worry about this (the increased pressure above the impeller is instead increasing the boiling point).
Great in theory or if the head is close to 30 feet. With his dimensions it’s a non issue.
Didn’t watch the YT… is this using the same ebike motor from the previous experiment?
yes he says he’s using the same motor as before.
I wonder how many years that generator has to run to make up for the electrons he burned(*) in that Tesla getting it there.
(*, yeah I know, but the electrons are 100% recycled. Darned ecofreaks, recycling everything.)
It’ll never undo the sociological harm of buying a Tesla.
he should put a foot valve at the intake so he can prime it without powered tools.
I would have welded it up out of iron to avoid leaks.
Siphon is lost due to air entering from the bottom end, not halfway. Thats why the bucket works that well. (The fact that the bucket works proves it) Siphon will be lost the minute the flow stalls and air rises from the bottom. Two solutions are a bucket or narrowing the end of the pipe. The bucket will be more efficiënt.
Grabby “I risked my life for this!!!” thumbnail = right-click “do not recommend channel”
Right? I’m all about hacks – being resourceful and creating something instead of buying an off the shelf solution is cool and fun. Creating something just for YouTube views / ad revenue is dumb and annoying.
Sounds like a small solar panel and battery would be better, cheaper, and easier to install.
Exactly this. In my opinion HaD has become far too enthralled with cute but mostly useless projects. I’m waiting for an article on some novel way to take cat pictures.
How about a camera to take pictures of cat intestines? There are two issues though, catching the cat and forcing an elastic rod up its ass.
I know that this is done to feed the algorithm, but these clickbait titles and the thumbnails with the creator pretending to be making a shocked face are the perfect recipe for unsubscribe/right-click “do not recommend channel” for me.
I truly hope these creators get out of this habit.
The creators who are the worst about it usually are the ones making vacuous content.
That tool he used to cut the pipe has a name and it’s not what he called it.
And why didnt he take the pipe out of the car before cutting it?
Cause nothing says “saving the planet” like a nice slice out of your fancy battery operated Golf Cart with touchscreen.
Since he didn’t bother to extract any power, he could have used a transformer (or inverter) to get 240V. Or 1kV. Or 1MV.
That would have been more impressive. Wouldn’t it?
TL;DR another yoootooob vid that isn’t worth spending any time on.
Used to work with a guy who had his own hydro system. There’s a name for these types of turbines, powered by the output suction. He learned a lot, about why you want high voltage (lower IR drop), how to keep leaves and sticks out of the intake (sloped grating) and how to deal with ice and drought. He kept at it, finally relocated, and I don’t think he ever got it running the way he wanted…it sure was a learning experience though. One thing he learned is that 10″ PVC pipe is way more expensive that he thought (and only sold in 10′ lengths)
I’m a bit confused here – what does atmospheric pressure got to do with it? I thought it was gravity “pulling” on the water and when the water column with the opening outside the container is “higher” then the one inside (which only goes to the current water level) and thus weights more -> it “falls down”, pulling more water behind it thanks to negative pressure.
If the tube’s wall/form strength is close to negligible it would just collapse under the negative pressure and it wouldn’t work??
Would a siphon not work in a vacuum?
https://en.wikipedia.org/wiki/Siphon?useskin=vector
^^ looked that up between writing 1. and 2. – seems it’s got nothing to do with atmospheric pressure.
barf-worty HaD commenting system – waht happend to my 1. and 2. at the start of two of those ^^ lines there?
ONE.DOT If the tube’s wall/form strength is close to negligible it would just collapse under the negative pressure and it wouldn’t work??
TWO.DOT Would a siphon not work in a vacuum?
And another thing: isn’t the atmospheric pressure “pressing” on the water level in the upper basin lower than the one pressing on the water level inside the open end of the tube?
I mean it has to be lower by definition and air pressure is higher the lower you get…
There are many silly things in this. The atmospheric pressure bit would mean you can fill a long vertical pipe with water, unplug the bottom, and the water would all shoot out the top? At the bottom of the siphon you have all the momentum of the water flowing in the pipe. At the top you have none. At the bottom you can have water hammer with an compressible fluid. At the top you can have it with cavitation – and a collapsed or broken pipe. More on the NEWS at 8.
Yes, exactly – it is nonsense. That is why I brought it up and am pretty sure atmospheric pressure has nothing to do with it.
The rest of your reply seems just as nonsensical… please see some of my replies below.
At the bottom of the siphon you have all the PRESSURE of the water in the pipe. At the top you have lower pressure (negative pressure in relative terms).
There’s no such thing as negitive pressure. There simply ‘less than atmospheric’ pressure.
If you experiment, you’ll find that the max height of a siphon is determined by the height where suction pressure exceeds atmospheric pressure. Above that, you simply create a vacuum at the top of the tube.
Sigh – yes, there’s no ABSOLUTE negative pressure. But there is RELATIVE negative pressure.
Please take a look at https://de.wikipedia.org/wiki/Heber_(Ger%C3%A4t)#Prinzip (specifically the diagram/illustration).
With the valve at the top close please tell me how the atmospheric pressure has anything to do with the different pressure on both sides of the valve (see the calculations).
And I have a thought experiment for you with two reservoir (1) elevated water filled and (2) lower and empty:
A) connect water filled hose to the bottom of (1) and put the other end with a closed valve in (2). Then open the valve.
B) put a loop in the hose. What about the water flowing up one half of it?
C) pull the loop above the water level of (1). What now?
D) repeat A) to C) but with the hose attached to the side at half the water height in (1).
C) repeat A) to C) but this time with the hose going over the edge of (1) and then into the water. (Like a normal siphon setup).
What happens in each of those? Why?
Has the atmosphere anything to do with it? I so why (now)?
What’s the difference?
No you don’t. You just boil of enough of the liquid the fill the space OR the tube collapses in on itself (which you can blame on atmospheric pressure – or more precise on the pressure gradient between the low pressure inside and “high” pressure outside exceeding the pipes/tubes specs).
I’ve used “vacuum” here wrong too.
Vacuum = completely empty space, not a single atom in there.
Same reason you can’t pull water from a well more than 10 meters deep: Atmospheric pressure must be high enough to push the water, and atmospheric pressure is only sufficient to push water up 10 meters (on earth, near sea level, if you want to be pedantic about it).
The counterargument “But my well is 200 feet deep!” I will leave to the utterer to ponder.
Would a siphon work in zero-G @1at inside the ISS?
At what pressure would it start working?…
Would a siphon work with mercury or water on the moon inside a bubble pressurized just enough so the respective liquid doesn’t evaporate?
The outside pressure must be high enough for the working liquids boiling point (at the given outside temperature) to be above the maximum relative negative pressure in the top bend of the siphon.
It doesn’t do any work. It’s not pushing any water anywhere.
Well that’s just wrong. The outside pressure has nothing to to with the boiling point inside that bent…
Where exactly do you think the pressure differential that makes a siphon work comes from?
From the different pressures of water at different depths/heights and a partially “closed” system thanks to the tube.
Imagine this with a typical siphon setup with two water reservoirs – one elevated relative to the other:
A) take two identical tubes with a closed valve at one end each and fill them with water.
B) Put the shorter tube in the upper reservoir with its open end, same with the longer on in the lower reservoir.
C) Put both valves at the same level above both reservoirs.
Now answer me this: What pressure “is” on the water side of each valve?
I’d argue it’s exactly the same (negative) pressure as a water column of the same height difference has in (positive) pressure (each reservoir’s water level compared to the level inside the tube).
I just thought about an even better (thought) experiment:
Upper water reservoir is filled water to 20cm.
Inside the reservoir is a siphon pipe which starts at the bottom, goes up 10cm and then straight down outside of the reservoir with a closed valve at the end.
Then you open the valve. What Happens?
Can we agree that the water is flowing because of gravity alone? At least for the top 10cm?
Why should this suddenly change between 0 and 10cm just because there’s an upward bow in the pipe?
(Excluding conditions outside this scope. Like the pipe being to big for the surface strength of the liquid(?) or the liquid having such low ??? that the “negative” pressure at the top bow of the syphon pipe is enough to cause it to boil/vaporize.)
This is the kind of physics thought experiment I love.
First off, I’ll point out any real liquid has a finite vapor pressure, so in a vacuum it won’t work anyway because the liquid will just cavitate or boil or whatever you’d call it and otherwise just have vapor/gas and it won’t work. (liquids “boil” when ambient pressure equals vapor pressure).
I think that explains the magic 10 m mentioned here somewhere- that is about 1 atm of pressure so at that level of vacuum, the water will just boil at room temperature and not really be a liquid and the thing breaks down.
you can also call it a negative pressure if you want, as long as you define the “0” point. For sure though, you cannot have a negative absolute pressure. Just a negative relative one which does help think through a lot of things, and lots of meters are calibrated wtih 1atm as “zero” and a vacuum as a negative number right there on the scale.
If we use some non-real liquid, I think the best analogy is to put a pile of chain on a roof that has like a small wall running around it. If you dangle the chain off the side of the building, once the chain dangling exceeds however high the small wall is, give or take, the pile of chain will pull itself “up” over the wall while the rest falls down the side, sucking the chain with it as it goes. And that would work in a vacuum for sure. I think that is a fair analogy of how a siphon works.
So based on that I’d guess atmospheric pressure has zero to do with a siphon.
I could be way off but that is at least a fun thing to think about. Thanks!
You can’t pull water the way you can pull a chain, the air pressure is the replacement for the pull between the chain elements. The breaking force of the chain limits the height the same way as air pressure limits the siphon — one could say, the breaking force of the water chain is about zero, and the air pressure adds an offset to that.
The chain-siphon analogy is useful do a degree but not “right enough”.
Trying to think about this in that way leads to “tensile-strength” of the liquid… Uhhhh?
After reading almost the whole English Wikipedia article on this yesterday I’ve thought about this quite a bit – including the chain example. See my thought experiments above.
IMHO the article is half nonsense (especially if you compare it to the German one).
I have no idea why the graphic to that shows anything regarding “atmospheric pressure”. Pretty damn sure the mercury would flow fine with a normal pipe connecting just the two beakers (without an opening to the outside.)
The siphon works, until somewhere on the flow path the pressure drops to absolute zero (which is atmospheric pressure minus hydrostatic pressure). If you take the highest point further up, the fluid stops flowing and forms a void.
https://de.wikipedia.org/wiki/Barometer has more pictures than the english version. In principle the siphon is two barometers in both reservoirs, you connect them where (the higher standing) fluid is, and it flows; you connect the two voids, and nothing happens. The atmospheric pressure (or water pressure in Pascal’s siphon) determines in balance with the gravity and the fluid density the height at which the void begins.
You need a siphon… why? Just a pipe at the bottom would solve all those “problems”
Because it’s someone else’s dam, and the guy is just doing it for a youtube video. A siphon isn’t practical for a water turbine because it isn’t self-starting, so it’s only for the clicks.
That someone else isn’t going to be happy either when they find out that someone put a “hole” through their dam and defeated its purpose. Even if it doesn’t seem like much and there seems to be plenty of water now with the weir running over, a lot of water will be lost through a 3″ pipe over time when it’s dry season.
First part is obvious for these types of things, ergo didn’t watch video. assumed (you know what “they” say) it was his own dam. Seems like poaching someone else’s water is a great way to get, um, I want to say shot? If he had permission to steal neighbor’s water, then a hole in the bottom still makes sense. But your first explanation (youtube for clicks) is definitely the winner.
Nice project. Free power!
I would say have a set of smaller pipes (like 10x 1inch) for the siphon function with valves to prevent air leakage and have those 10 piped go into one big pipe witch hold the generator part.
It could have an ‘ autostart’ function using a battery powered arduino that monitors the water flow in the smaller pipes and activate a air pump to get the water flow stared again.