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DGoncz@aol.com
science forum Guru Wannabe
Joined: 25 Oct 2005
Posts: 122
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 Posted: Sat Jun 24, 2006 1:39 am Post subject:
Collected 12 kj of sweat energy the other day
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Hello, spr.
I took my Lightning Thunderbolt recumbent equipped with Wilderness EV
600 W capacity front hub in parallel with a bank of (series wired)
ultracapitors (8 x Maxwell PC 2500 @ 2700 F each) and a voltmeter for a
ride the other day. Initial EE was zero on the voltmeter. During the
ride, the voltmeter rose to over 12 volts and was back to around 9 VDC
at return, when the switch was shut off. Later, I demonstrated the
ability of that energy to power the wheel, indoors.
Here are my calculations:
E = 1/2 * C * V^2
= 1/2 * (1/8 * 2700 F) * (9 V)^2
~= 12 kj
What an incredible ride! At one point I was coasting over a rise with
what seemed to be the wind at my back. It was the EE, though. There was
no wind. My longest coast was some 500 yards, but the terrain was not
level so I can't say exactly what happened.
There is a total of 20 V of capacity in those 8 2.5 V cells. On a
push, they can store 2.7 VDC. At 20 V I am figuring around 50 kj. At a
drain rate of 100 w I should be able to coast around 500 sec or nearly
8 minutes for maybe something like three laps. We'll see.
I will try the local track on a clear day soon. We have rain all
weekend here. :(
I think this is the first self-recharging human/electric hybrid, and I
intend to exhibit it in Boston in 2009, in the spring, most likely, in
a more fully developed form, with brake, tail, turn, and head lights. I
have an additional 8 caps and there are some awesome hills right around
the corner.
Remember you heard it here first, in news:sci.physics.research....
Doug Goncz
Replikon Research
Falls Church, VA 22044-0394 |
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DGoncz@aol.com
science forum Guru Wannabe
Joined: 25 Oct 2005
Posts: 122
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| Posted: Sat Jun 24, 2006 9:13 pm Post subject:
Re: Collected 12 kj of sweat energy the other day
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I wrote:
| Quote: |
I will try the local track on a clear day soon. We have rain all
weekend here. 
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Well, this morning was clear enough, so I went to the track, but it was
closed.
On a few small hills the stiffness of the system was impressive. By
changing by only two gears I went from pushing hard uphill to pushing
easily with little change in speed. The transition from storing to
delivering energy is seamless, as expected.
I did a test in Dr. Majweski's lab with a motor and parallel chemical
battery years ago and found the stiffness (watts per delta mph) of that
system unacceptable. Thinking it over, such a curve would have a slope
at the crossover voltage, and less extreme slopes farther from
crossover, due to I^2*R losses. I think I feel those losses.
The 8 cells are charged to 11.74 volts total with a population standard
deviation of 9.6 millivolts on individual voltages, or less than 0.01%.
That's pretty good balance, even though the balancing resistors (one
across each cell) are only 5% tolerance. That's over 20 kilojoules at
that voltage.
Assuming 0.01% standard deviation at any charge, which seems reasonable
given the circuit topology, if this pack were charged to 20 volts, the
probability of any cell exceeding the design limit of 2.7 V is around
2x10^-30. That's important.
Beyond 2.7V any cell would begin to pressurize and could vent
acetonitrile. The cells are mounted in a zippered rack bag on a rack
behind the seat so that in this event, the chance of cyanosis is
lessened.
My brother sold me his 3x7 Sachs hub so I am building a hybrid
transmission (a new wheel, the hub, cogs, and front chain rings) with
almost a decade (1000%) of range. Thanks, bro. Of interest is the
system's ability to redirect pedaling power to storage during a descent
in which the power rate is already high. The goal is to store the
energy of descent instead of warming the atmosphere behind the bicycle
with that energy. It's a large volume of air with a very small
temperature differential, but it's a lot of energy.
Doug |
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Tom Roberts
science forum Guru
Joined: 24 Mar 2005
Posts: 1399
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| Posted: Sat Jun 24, 2006 9:13 pm Post subject:
Re: Collected 12 kj of sweat energy the other day
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Doug Goncz wrote:
I think you GREATLY underestimate the effort of riding a bicycle.
Today I rode my Cannondale touring bike at an average speed of 17.5 MPH
for just over 2 hours and 50 minutes (68 miles, as indicated on my bike
computer; 1.5 hours of rest stops are not included). So I was riding
about 14,000 seconds. My average effort while riding was surely more
than 0.01 horsepower, which would total 104 kiloJoules. I'm quite sure
that is an underestimate, probably by a rather large factor.
Now this is not a recumbent, and this is on the relatively flat terrain
of northern Illinois, with very light wind. Still, it's an order of
magnitude larger than your number.
Your computation only gave the stored electrical energy at the end of
your ride. But in your description you indicated the motor had assisted
you during the ride. So the total "sweat energy" you expended exceeds
the amount left in the capacitor at the end.
For a 100 kg rider+bike (I'm within 10% of that), your 12 kJ of energy
corresponds to an altitude change of only about 13 meters. Somehow I
don't think that sort of assist will foster a revolution in bicycle riding.
Tom Roberts |
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DGoncz@aol.com
science forum Guru Wannabe
Joined: 25 Oct 2005
Posts: 122
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| Posted: Sun Jun 25, 2006 2:20 am Post subject:
Re: Collected 12 kj of sweat energy the other day
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Tom Roberts wrote:
| Quote: | Doug Goncz wrote:
~= 12 kj
I think you GREATLY underestimate the effort of riding a bicycle.
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No, I am clear on the applied power levels required.
| Quote: |
Today I rode my Cannondale touring bike at an average speed of 17.5 MPH
for just over 2 hours and 50 minutes (68 miles, as indicated on my bike
computer; 1.5 hours of rest stops are not included). So I was riding
about 14,000 seconds. My average effort while riding was surely more
than 0.01 horsepower, which would total 104 kiloJoules. I'm quite sure
that is an underestimate, probably by a rather large factor.
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Your output was probably more than 100 watts at that speed, well over
1/10 HP.
| Quote: |
Now this is not a recumbent, and this is on the relatively flat terrain
of northern Illinois, with very light wind. Still, it's an order of
magnitude larger than your number.
But of course! 12 kj, as you wrote below is only the amount left at the |
end. There were at least eight cycles of storing and delivering energy
in that ride. The caps are rated to 100,000 cycles.
| Quote: |
Your computation only gave the stored electrical energy at the end of
your ride. But in your description you indicated the motor had assisted
you during the ride. So the total "sweat energy" you expended exceeds
the amount left in the capacitor at the end.
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Yep. I expended much more than 12 kj. Actually, at a muscular
efficiency of 25% or so, much, much more. Say, hundreds of kilocalories
of food energy. You'll agree it all depends on what you count, doesn't
it?
| Quote: |
For a 100 kg rider+bike (I'm within 10% of that), your 12 kJ of energy
corresponds to an altitude change of only about 13 meters. Somehow I
don't think that sort of assist will foster a revolution in bicycle riding.
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Actually, you have to feel it. The hills just kind of even out. Yes, I
agree that at g, the figures you give are correct, but the pack has a
capacity of over 50 kj, and a second pack, as noted, is available.
Of secondary interest is to be able to get light output without
charging batteries, and to operate a computer nav system.
Thanks for your interest, Tom! You're a strong rider.
Doug |
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DGoncz@aol.com
science forum Guru Wannabe
Joined: 25 Oct 2005
Posts: 122
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| Posted: Thu Jul 06, 2006 3:32 am Post subject:
Re: Collected 12 kj of sweat energy the other day
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Today I took a ride to a local slope, descended with the
self-recharging ultracapacitor rig on my bicycle engaged, made some
voice notes on the way, and returned. Overall, I'd say the system is
too stiff; at the end of the hill I had too much EE, too little
voltage, and too little KE. I think I need to reduce C (capacitance). I
think my C is around 10 times too large.
I need to think about partitioning EE and KE as PE or applied pedal
power is converted, and whether C might relate to m (mass of the rider,
bike, etc.) .
I think it might be possible to choose C to achieve EE = KE, given the
motor characteristics and m, ignoring drags for the moment.
The generator constant of this motor is around 3/2 or 5/3 volts/mph,
around 75 or 80 volts per krpm with the 16 inch wheel. On free running
at 7.5 V we see a draw of around 300 ma, so the bearing drag is less
than 3 watts and since at stall the current jumps to at least 1.5 A,
the terminal resistance is less than 5 ohms.
I am unable to relate the generator constant and the torque constant by
the square root of the terminal resistance in the proper units. I have
a Maxon motor catlog handy with reference formulas. This is not a Maxon
motor.
Help from any reader here would be appreciated.
Doug Goncz
Replikon Research
Seven Corners, VA 22044-0394 |
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