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I’m from Cape Town. My daughter is doing a geothermal energy power plant for her science project and we are battling to get the turbine with the DC motor to spin when steam hits it. The Dc motor is not loose enough so won’t turn to generate electricity to our small LED light. Please can you help.

We have literally tried everything (9V, 3V and 5V. The voltage is not the issue) it’s the amount of pressure needed to turn the wind mill. Is there anything you can make other than the DC Motor that will turn with the light pressure of steam? I can send a video so you can get an idea of our intentions. Anyone that lives in Cape Town. ☺️

enter image description here

Transistor
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Jaclyn
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  • I think that this kind of vane made with a folded paper is not efficient. This is the format of a professionally used vane. But even with another kind of vane, a DC motor is not efficient as a dynamo... A real dynamo would require more power than this vapor propeled axe could give... couldn't you try another kind of eco-friendly energy, like, solar energy? – mguima Oct 22 '17 at 22:38
  • looks like you need either more pressure or more volume of steam. You may be able to find a lighter motor, but you still need enough the energy in the steam that you need to light the LED * the transfer efficiency, which will be horrible with this setup. try a nozzle on the steam exit that accelerates the steam and puts is a lot closer to the vane. Be careful you don't build up too much pressure though. – Trevor_G Oct 22 '17 at 22:41
  • What have done in the meantime until we figure this out is make a look pretty as she needed photos for tomorrow ... we have honestly tried all of which you have both said... I’m now thinking I should find a new DC motor or an engineer who can loosen the turning part of the motor... it will work if it is loose... if I blow on it , it does turn and the light does go on but it’s not reliable and can sometimes stick... hmm the joys of parenting . And suggestions regarding what I can buy or maybe a steam turbine could work? – Jaclyn Oct 22 '17 at 22:52
  • Mguima... I unfortunately can’t change it... I wish she didn’t choose something so difficult although she is the only one doing geothermal which is a good thing. – Jaclyn Oct 22 '17 at 22:54
  • Jaclyn, if it works blowing, try the tube solution (idea 2), put the steam release point below the vane. As you dont have time, keep this vane... With some luck, the upstream of steam will keep accelerating the axe until the maximum speed is reached. Good luck... ;-) – mguima Oct 22 '17 at 22:58
  • A tiny pager or vibrator motor from a cell phone. And or use the motor to turn on a transistor. The concept is the same even though you are using it as a sensor instead of a power supply. – Passerby Oct 22 '17 at 23:20
  • Why not just change the gear ratio of the turbine? Perhaps you could get a hold of some lego gears. – Bort Oct 23 '17 at 02:22
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    Steam goes everywhere, or more specifically, it goes where there is lower pressure - in your picture, that is everywhere. You lose most of the force. Use a container and pistons, save yourself. Remember a proper valve, or you’ll have a weird experience. Just route steam like you’d route water. – user2497 Oct 23 '17 at 08:13
  • maybe a stepper motor would work better / by the way, i live in cape town :P – Makoto Oct 23 '17 at 15:19

3 Answers3

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This is more a problem of aerodynamics than an electrical problem. When you vent a bottle of steam that way, it loses most of its energy right at the vent.

So you have to use a turbine roughly the size of the vent to get the most of the energy from the steam. It doesn't have to be such a convoluted design, a simple wheel with 8 straight flaps is sufficient. But remember, it has to be tiny.

Your DC electrical generator has a cogging torque which you had to overcome first to run from a standstill. In addition, you have to speed up against the inertia of the rotor mass. Both is going to be hard for an arrangement using improvised (non-optimized) parts.

Again, use the tiniest DC motor/generator you can get your hands on. Go to a model railroading store, they sell such stuff and can show you motors with a small to neglible cogging torque. With such a motor, your arrangement should work.

Janka
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    Also, increase the pressure of the steam –  Oct 22 '17 at 23:22
  • Agree with the answer - it would be almost on-topic over at Physics.SE. But even there this probably would be seen as engineering more than science. That said, I'd use a funnel in reverse (could be paper) so the steam hits the full surface of the current wind mill. IOW, don't scale down, scale up. The burner looks like it can produce sufficient heat. – MSalters Oct 23 '17 at 11:45
  • I agree it is more physics but the topic for science expo for the grd 5’s is Energy and the pics show solar, wind energy etc ... so my daughter chose geothermal lol just to make it harder for us parents ... – Jaclyn Oct 23 '17 at 17:58
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You could try enclosing the turbine so the steam only has one way to go...

Use some transparency type material so you can see through it and cut it something like this...

enter image description here

Add tabs to that so it's easier to hold/tape together..

The best design would offset the windmill up from the centre and you would blow the steam in, across the top circle in this image, and allow it to escape through a larger hole or slot bottom left in the top circle. That way the steam can also expand as it goes around the turbine. This should get you more efficient energy transfer.

You can also try adding a Venturi air pump mixer to the steam nozzle. That is basically feeding the steam jet through a larger pipe which will suck air in behind the steam as it is pushed through the pipe by the nozzle. You do of course lose energy from the steam during the process but you may make up for that with the added volume.

enter image description here

Obviously the more, and higher pressure steam you can make the better. Try and find a much larger beaker.

One more thing. Make sure you have a resistor in series with the LED. It will take lots of current and the motor will act much more like a brake without one.

Trevor_G
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Instead of steam - fan arrangement try to use Stirling engine.
It is more effective, anyway can be harder to build at home. You can find Stirling engine with little power generator, like this one

smajli
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