Optimizing Miniature Dynamo Systems for Efficient Energy Generation

[WiseGreatTrixie]

So..What would be the most efficient miniature dynamo system?

So my question to you, on the small scale, what would be the most efficient dynamo system? Small scale meaning a handheld size device. I know energy can be generated using Faraday's law, when you move a magnet near a coil it generates electricity. But how much, and which configuration would be optimum? Its been a while since I went to engineering school so I would like to learn a few things. Which is more important, should we focus on the Joules (weight energy) and physical force to turn a dynamo wheel, or is simply the moving of the magnet important, and the speed in which it moves? Is it better to turn a dynamo wheel using Joules, or is it better to have a moving magnet, light as a feather, exerting no force on the dynamo, and just magnetically generating electricity in the coils?

And, where would I get and purchase one of these devices, these dynamo devices?

For example, the system energy I wish to transfer into the dynamo, is 0.02 Joules.
The speed at which a magnet could move (in order to generate electricity) is .51 m/s.
How much energy could I get from this?

I would like a reference, specifically how much energy does it take to generate a electromagnetic field equivalent to the strength of a fridge magnet that lasts for 10 seconds?

 

[CWatters]

I'm sure there must be papers on the efficiency of hand cranked generators. I didn't look hard but Google found one detailing tests of two slightly different hand cranked generators...

http://www.google.co.uk/url?sa=t&rc...77Dpv3Mx6vMOgf4hg&sig2=DmtpC4HYvgc5v998nO3Zbg

Test results in Figure 3 indicated peak system efficiencies around 50% while Palm Power units were operated at mid-range torques and at a cranking speed of 120 rpm (2 revolutions per second). In this range of operating points, the device generates 8 to 11 watts of electrical power. The average male soldier can reasonably be expected to crank a Palm Power unit for about 5 minutes in this range.

So it seems at least 50% efficiency is achievable.

For example, the system energy I wish to transfer into the dynamo, is 0.02 Joules.

That's not much energy. Is that all you have available or all you need to generate? 1 Watt is 1 Joule per second so this particular generator can deliver 8-10 Joules per second. More than 500 times what you need?

 

[WiseGreatTrixie]

I would like to at least power a fridge magnet but I can't find any reference on google on how much energy that needs. (An electromagnetic equivalent.)

 

[CWatters]

https://en.wikipedia.org/wiki/Gauss_(unit)

50 gauss a typical refrigerator magnet

Then to design your electromagnet perhaps see pages like..

http://nbviewer.jupyter.org/github/tiggerntatie/emagnet-py/blob/master/solenoids/thin_solenoid.ipynb

Once you have the required dimensions for the electromagnet work out the resistance of the wire (eg from number if turns and wire gauge). Then you can work out the voltage and power needed to maintain the field.

PS: One tesla is equal to 10^4 gauss

 

[WiseGreatTrixie]

I thank you. However, I would like to know how much energy a fridge magnet has? Otherwise I will have to set up testing and test several paperclips to measure the max load of a fridge magnet vs. my custom magnet.

 

[CWatters]

It's not easy to predict exactly how much weight a magnet can lift. Calculated figures can vary from actual by a large amount. There is a equation for a magnet an a steel plate but you will get different results with paper clips...

http://www.engineersedge.com/calculators/magnet-lifting/magnetic_force_calculator.htm

 

[anorlunda]

I thank you. However, I would like to know how much energy a fridge magnet has? Otherwise I will have to set up testing and test several paperclips to measure the max load of a fridge magnet vs. my custom magnet.

You are talking in the wrong units. A magnet does not store energy as a battery does. A magnet can exert a force. Force and energy are different things.

 

[NascentOxygen]

Dynamo question has been answered, now the thread is unravelling.