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humgen

Newbie

Joined: 22/12/2007
Location: United States
Posts: 1

Posted: 01:03am 22 Dec 2007

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Since wind and sun are both scarce commodities at times, here in northeast Ohio, I am building a human powered generator here at the farm, fashioned after the old windlasses that were used to raise the anchor on sailing ships. I can run the windlass at any RPM, up to 2000 rpm. I am setting up a 12 volt system, with 10 deep cycle, @400AH capacity batteries. Since the generator will be human powered, i want to minimize run time.
It seems sensible to run DC generators to produce the power to charge these batteries...but I know little about DC power generation. Can anyone help me with determining the optimum number of generators to mount on my windlass, and how to use them in conjunction with this battery bank, to produce maximun battery input in minimum run time? Thanks

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Gill

Senior Member

Joined: 11/11/2006
Location: Australia
Posts: 669

Posted: 04:25am 22 Dec 2007

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G'day humgen,
Firstly welcome to the Forum.
Your desire for human power sounds genuine though a little unrealistic if the size of your battery bank is any indication of what your expected usage will be like.
You fail to mention this critical information.

Might I suggest you build or modify an exercise bike for power generation first? This will give you a practical reference of what might be expected from our animal bodies when put to the task of generating electricity. Indeed your mostest in the leastest is likely to then change to modest and sustainable.

was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 1343

Posted: 06:39am 22 Dec 2007

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Hiya Humgen,
Welcome to the forum mate

Now as you say the sun and wind are scarce at times, have you thought about amophorus solar panels as they do still charge on overcast days. I have 14 kaneka thin film panels on our house that go thru a AERL900B mppt. Even on total overcast days I still see around 10-15 amps going into our 24 volts battery array. Only in winter when its raining for days on end do I need to run a 5kw genset to power my 80 amp staff&stanbury solid state smart charger.

I'm sure once you make a human powered generator within 2 weeks you'll regret it

. Go take a look at otherpower.com and the 10' axial flux genny, you can make the genny to have a cutin speed of less than 100 rpm and I'm sure that would also come in handy.

Just one more thing unless you've already bought an inverter go for a 24 or 48 volt system as 12 volt arrays need a second mortage just for buying thick copper wire to handle the huge currents needed for 12 volts.

Cheers Bryan

KiwiJohn
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Joined: 01/12/2005
Location: New Zealand
Posts: 691

Posted: 03:59am 24 Dec 2007

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Hi Humgen

I have played a little with a human powered generator for no particular reason except to see just what could be done and what I would learn.

The first lesson I learned was that every stage of mechanical gearing used my precious energy and even a sprocket and chain used a few percentage points and two stages is more than twice as lossy as one.

The second thing I learned is that just turning a typical generator at high speed is more than I could manage even with no electrical load!

Fortunately I had a few F&P under the bench which began to look very attractive. They dont need to turn very fast and are really easy to modify in various ways.

So I built a system on an old exercise bike with two stages of chain and sprocket gearing. Lets say 95% effiency with the chains that 95*95 = 90.25% (oh dear! Thats nearly 10% gone before I even started, oh well, it was the best I could do.)

Then I found that a certain minimum speed is required if there is not going to be a big strain when the pedals at top and bottom, so I left the exercycle flywheel on. I dont know how much drag there is from the flywheel but it must be appreciable.

Initial tests showed that the minimum speed I was spinning the F&P produced more watts than my legs were able to power for any period of time so I took my hacksaw and cut off a little more than half the stator coils. Dont you just love how easy F&Ps are to modify?

At the end of it all I have an easy to pedal human generator which I can comfortably 'ride' for extended periods of time and the real output is about 50 Watts!

Different gearing, different generator, different rider, the results would be different but I am quite confident that the results of my experiments show that for a normal person something in the order of 100 watts is all that can be expected and I have grave doubts about the claims of some of the systems that are described and even for sale on the 'Net.

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