Using man-power to turn massive generator

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In summary: Welcome to PF!By having a very large distance (the large outer gear), you would produce a larger force, right? This force would turn the generator rotor which creates electricity. I really don't know how generators work. Is there an increasing resistance as more power is being generated from the generator?Lareg force moving very slowly, yes. Or, you could reverse the gearing and have a very weak force moving fast. But the total energy at the output will be the same as the amount of energy put in (or less).So, if a reasonably athletic person can generate 200W of power. There is no way I
  • #1
tmoney
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Hi

I just wanted to run this hypothetical power plant idea past you physics guys to see what kind of feedback I could get.

My general question is "Could man-power through the use of massive gears, be used to turn a very large generator.?"
The generators used in the Three Gorges Dam(http://en.wikipedia.org/wiki/Three_Gorges_Dam" [Broken]) can generate 700MW of power and are about 75 feet in diameter. What kind of force would it take to get this thing spinning? My idea is to build a massive "outer" gear lined with manned pushing posts around the entire circumference. The generator would be in the center. Through the use of many gears that get smaller and smaller, enventually ending up as the rotor of the generator, you could gain massive mechanical advantage. The men would push at a walking pace while the center rotor spun at a great rate. I am picturing 100, 200, 500 men, not sure. Any initial thoughts? I realize there are several unknowns in this. I just want to gets some thoughts rolling. Thanks

Here is a pic of the generator.
http://www.nancarrow-webdesk.com/warehouse/storage2/2008-w25/img.249065_t.jpg"


OOps, I just realized this should be under the engineering section, sorry
 
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  • #2
A reasonably athletic person can generate perhaps 200 W of mechanical power by pedaling a bike. So if you lined-up 3.5 million people on stationary bikes, you could run those generators with people. It is China!

I'm also not sure you understand what the term "mechanical advantage means". Whether it is a lever or a gear, when you multipy speed (distance) on one side, you have to multiply force on the other. So mechanical advantage yields no increase in power.

Welcome to PF!
 
  • #3
By having a very large distance (the large outer gear), you would produce a larger force, right? This force would turn the generator rotor which creates electricity. I really don't know how generators work. Is there an increasing resistance as more power is being generated from the generator?
 
  • #4
Lareg force moving very slowly, yes. Or, you could reverse the gearing and have a very weak force moving fast. But the total energy at the output will be the same as the amount of energy put in (or less).
 
  • #5
So, if a reasonably athletic person can generate 200W of power. There is no way I could, for example, get this 2400W generator going using just my power with the help of a very large and a very small gear.http://www.grainger.com/Grainger/items/6HJ87" [Broken]
 
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  • #6
No. Your problem isn't that you don't understand generators, it is that you don't understand what gears do: mechanical advantage. Read the wik link: http://en.wikipedia.org/wiki/Mechanical_advantage

In short, think about the example of a lever: one end moves a large distance with a small force and the other end moves a small distance with a large force. But the torque and work (or power or energy) done remains the same for both ends. Levers and gears multiply force, not energy.
 
  • #7
Ok. Thanks for the info. These forums are very informative.
 
  • #8
tmoney said:
So, if a reasonably athletic person can generate 200W of power. There is no way I could, for example, get this 2400W generator going using just my power with the help of a very large and a very small gear.http://www.grainger.com/Grainger/items/6HJ87" [Broken]

Not with gears, but you could possibly with a spring (or other energy storage and release mechanism). If you get on the treadmill and generate 200W fo energy for 10 hours, I suppose you could run a 2000W generator for 1 hour.
 
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  • #9
I have given thought to this concept as well, but from a bit of a different perspective...

Most of us pay taxes to keep prisoners locked up, and fed... so why not put them to work? Assemble a gearing system that links up dozens (maybe even hundreds) of bicycles, and connects them to a massive generator.

If you've got a prison of 800 men... you could divide them up into groups of 200, and schedule them to be always pedaling... say
200 men * 200 watts/hr * 24 hours a day = just under 1 megawatt/day...

this is just an example, and obviously not nearly enough power to power big cities... but surely there are some efficiencies to be gained in a large scale system like this... maybe?

anyway, just a thought.
 
  • #10
bigtruckdrive,

The watt is a unit of power, defined as energy per unit time. The unit "watt/hr" makes no sense. Neither does the unit "megawatt/day."

Furthermore, if you want prisoners to produce mechanical energy, you'll need to provide them an equal amount of chemical energy, as food. (Actually, even more, since human muscles are not 100% efficient.) The big problem is that human food is considerably more expensive, per unit of energy, than many other forms of energy.

A gallon of gasoline contains 35,000 Calories and costs about $4. A pint of Ben & Jerry's ice cream contains about 1,200 Calories and costs almost as much. You'd be much better off sparing the prisoners and just burning gasoline.

- Warren
 
  • #11
hah, i guess that is a good point. hadn't thought of that.

I guess you'd have the prisoners putting out a decent amount of CO2 as well...

Although I wonder, if the energy they are burning is from a low cost food source, like rice or pasta, this might be more feasible?

It seems to me that this is a resource we should take advantage of! lol
 
  • #12
Your calculation produced 1 megawatt-hour per day of energy or 40 kilowatts of power. That's not very much. Just as a benchmark, commercial office space runs around 5 watts per square foot in the summer. So your 40 kW gives you enough power to run 8,000 square feet of office space.
 
  • #13
Ya, seems like the power produced would be negligible. If anything I supposed this generated power could be use to power the prison...
 
  • #14
I think it's a good concept. I have long held the position that there should be no such thing as "hard labor" as a separate sentence for convicted criminals. It should be understood as part of their sentence that they will work rather than sit around living off of taxpayer's money. But, I suppose that putting them on bicycles to power an air compressor so a jack hammer can split rocks is inherently less effecient than putting a sledge hammer in their hands and having them whack away.

Still, the comparrison to gasoline does not take into account the fact that, if these men do not use their energies to do work, they are still going to burn those callories, so you don't save that energy by not putting them to work. There must be some practical way of using all this manpower to defray some of the expense of operating the prison.
 
  • #15
I had thought of the prison idea as well, and these guys would already be eating and burning calories bench pressing or beating up their cell mates. You might as well harness those calories.

I like the idea of man-generated electricity. The human animal doesn't need electricity to survive. Humans have produced a society that requires electricity. It should be Human's that do the work to produce it instead of harnessing various forces of nature.
 
  • #16
tmoney said:
I had thought of the prison idea as well, and these guys would already be eating and burning calories bench pressing or beating up their cell mates. You might as well harness those calories.

I like the idea of man-generated electricity. The human animal doesn't need electricity to survive. Humans have produced a society that requires electricity. It should be Human's that do the work to produce it instead of harnessing various forces of nature.

Humans are very weak an inefficient at producing energy mechanically. But with just a few watts of electrical energy, our brains can devise ways of harnessing other sources of energy far greater.

Instead of putting a thousand prisoners to work moving boulders, you should stuff them in the library and force them to learn physics & engineering. :)
 
  • #17
Hmm, good observation. I guess we have created a monster that we can no longer feed, and we are took weak to do what it does for us.
 
  • #18
Hi guys, my first post! I really enjoyed reading this thread, it's funny and intelligent - a great combination.

I found this site trying to work out the power a person can generate (not just consume).. you know how it is, ideas, nothing to do, calculator itching for numbers..

My physics is a little rusty so I really enjoyed reading this post. It looks like a few keen minds are as rusty as me and the perhaps improper use of some of the terms used is caused by not fully understanding them. Things like what power, leverage or a KW/h actually is.

What roused my interest is the 200W a 'reasonably fit' person can produce. Am I right to think you mean this in a calorie/joule - energy ratio per hour?

An average althetic male will use about 1700 cals a second (612Kcal hour) playing squash - intense physical exersion. A watt is the SI derived unit of power, equal to one joule of energy per second. Ergo 1W = 1J/s. 1 calorie = 4.18400 joules (4.2W) which equates to 7112.8W or about 7Kw second for the squash player. As Watts and Joules are time oriented, we can't multiply this out to infer a human will generate 25MW/h! I understand this healthy person is capped out at 7Kw/h (I said I was rusty).

I can only understand from tmoney's original question (also with reference to https://www.physicsforums.com/showthread.php?t=299004" Force Needed to Turn Generator at Maximum Output post) that from 6 hours (hard labour a day) would equate to (7Kw/h * 6 hours) 42KW/h day.

I see one obvious flaw (aside from my maths) in the fact that we would expell 7112.8W a second just to do the work so any device used to capture the energy would be less efficient. Some of the most efficient alternators are about 80%, but it's interesting to imagine how much real-power can be produced from pure grunt. In honesty my interest comes from thinking the gym in itself is a waste of time and quite literally - energy. It would be interesting to save it up and use it at home squashing the electricity bill, staying fit, or do I just need to get out more? :smile:
 
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  • #19
"Could man-power through the use of massive gears, be used to turn a very large generator.?"You're going to require cheep labour fir that...so why not go to India to try it?

can generate 700MW

Considering the efficiency of this thing is not 100% you're going to require men so as to generate this much amount of energy in a limited time interval.
Feed them well! :)
 
  • #20
The image says not for public use.
 
  • #21
No body discusses the man's old friends, Bulls and Elephants. What if they are substituted as prime movers? I hope it would dropm the workers figures in million to some less number. Other than that it would help save wild life.
 
  • #22
robotbender said:
What roused my interest is the 200W a 'reasonably fit' person can produce. Am I right to think you mean this in a calorie/joule - energy ratio per hour?
Welcome to PF.

A calorie/joule doesn't make any sense to me. No, 200W is 200W. It is the power that they generate (ie, by pedaling a bike).
An average althetic male will use about 1700 cals a second (612Kcal hour) playing squash...
You have an extra zero in there: 612000/3600=170 cal/s.
A watt is the SI derived unit of power, equal to one joule of energy per second. Ergo 1W = 1J/s.
Yes.
1 calorie = 4.18400 joules (4.2W)...
Now you are mixing power and energy. 1 cal is 4.18 J or 4.18 w-s.
...which equates to 7112.8W or about 7Kw second for the squash player.
Same error carried forward: 170 cal/s *4.18 J/cal = 710 J/s or 710 W
As Watts and Joules are time oriented, we can't multiply this out to infer a human will generate 25MW/h! I understand this healthy person is capped out at 7Kw/h (I said I was rusty).
You're realizing there is a time element there, but using it incorrectly. There is no such thing as a MW/h or KW/h. MW and KW are already a rate, in terms of seconds. To get power, you multiply by time. Energy from a power plant is measured in KWh or MWh, which is killowatt-hours or megawatt-hours: 1000 and 1000000 J/s-h.
I can only understand from tmoney's original question (also with reference to https://www.physicsforums.com/showthread.php?t=299004" Force Needed to Turn Generator at Maximum Output post) that from 6 hours (hard labour a day) would equate to (7Kw/h * 6 hours) 42KW/h day.
Again, these units are wrong and the decimal error is carried forward: 700 W for 6 hours is .7*6 = 4.2 KWh per day.
 
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  • #23
I don't take anything for granted, and I don't believe everything I am told. I like to put things to the test. So does anyone have an idea, for some way to test this theory?

I would think using a controll, of one man, healthy enough to turn a turbine or generator of
some kind, to see how much energy he can produce by turning a lever let's say, would be simple enough. however
Not all men are equall.
And I don't like the idea of using a bycicle, to see how much energy is produced. (you are only using your legs)

what I would like to see, is a small wind turbine on the ground, positioned so blades were parellel to the ground, and see how many men it would take to turn the blades of the turbine.
Unless someon has a calcutlon they coudl run to show that this would be an impossible act?

I would even be up for planing an event at some location, gathering some able bodies up,
and testing this theory.
 
  • #24
Any elliptical machine will use both your arms and legs and already tells you the power output. If you don't believe it you can hook it or a bike up to a generator. There is no need to get convoluted and complicated.

I'm not sure you will get many people who don't believe what their exercise bike is telling them so you may need to just do this yourself.
 
  • #25
russ_watters said:
Any elliptical machine will use both your arms and legs and already tells you the power output. If you don't believe it you can hook it or a bike up to a generator. There is no need to get convoluted and complicated.

I'm not sure you will get many people who don't believe what their exercise bike is telling them so you may need to just do this yourself.

I hear what you are saying. I could measure what my own output would be. But my problem with this theory is that we are bassing these calculations, on what one man can do. I am terrible at explaing these things, but I will try:
I can peddle my bike at a maximum sustained speed of 17 miles an hour, on flat ground.
In our equations, we are assuming that if we add another man to the bike, we can now go 17 x 2 = 34 miles an hour.
But this is not true. Haveing a tandum bike does not meen you go twice as fast.
The reason being is you are limited by the bike itself. the gears are too small, there is greater wind resistance, ect.

In essence, what we would have to do is make the the gears bigger.

Let's say you have (2) men in a room with a stationary bike. no wind. no road friction.
It would stand to reason that (2) men, could move the same gear, that is twice the size of the gear, that a single man can move.

What I am saying, is that (2) men could move a gear that is 2 1/2 times the size.
Maybe even more.
 
  • #26
markplans2 said:
I hear what you are saying. I could measure what my own output would be. But my problem with this theory is that we are bassing these calculations, on what one man can do. I am terrible at explaing these things, but I will try:
I can peddle my bike at a maximum sustained speed of 17 miles an hour, on flat ground.
In our equations, we are assuming that if we add another man to the bike, we can now go 17 x 2 = 34 miles an hour.
But this is not true. Haveing a tandum bike does not meen you go twice as fast.
The reason being is you are limited by the bike itself. the gears are too small, there is greater wind resistance, ect.

In essence, what we would have to do is make the the gears bigger.

Let's say you have (2) men in a room with a stationary bike. no wind. no road friction.
It would stand to reason that (2) men, could move the same gear, that is twice the size of the gear, that a single man can move.

What I am saying, is that (2) men could move a gear that is 2 1/2 times the size.
Maybe even more.

It's possible that the human body could be more efficient at pushing a lever with high force at low speed (I have no idea if this is the case). However the maximum product of the two (force * speed = power) is still limited by what the average human body can continually produce due to physiology.
 
  • #27
The most efficient way to harness human-generated energy, imo, is to put people in warm clothes when it's cold and have them do exercise or labor to warm themselves. I have experimented with this and found that I can live comfortably as low as 40F with a warm coat and hat/cap. Compare the amount of calories/joules/btus necessary to bring a house from 40F to 65F and the amount your body needs to generate to keep you feeling toasty in a sweater or coat with hat and gloves? If you're doing exercise or labor, you might even need to shed some of the clothes.
 
  • #28
Hallo every one, I was very surprised and happy at the same time to find out there is a Forum investigating about this interesting issue on which I’m thinking since some time. For this reason I just got registered and wander if we could continue to analyze and expand the subject more in details, scientifically in all aspects related to the use of man-power to produce electricity, not only for prisoners but also for poor communities where having access to few kWh of electricity it could mean much more the better welfare.
I personally would be very interested to study the idea of introducing this opportunity into prisons, (that it shouldn’t be an obligation to my opinion) I’m convinced there would be a number of interesting advantages, such as:

1. producing something (you said 4-5 kWh, maybe by using a more efficient equipment it could be increased ?) it would be good for the environment and the society while reducing the prisoner public cost.
2. while the man is physically at work pedaling, with legs and/or even with arms, at the same time he could still use the brain and apparently without disturbing his concentration with good result for both mind and body activities.
3. the activity is proved of being an important health factor, “Mens sana in corpore sano” (healthy mind in healthy body) there should be experiments already done that can tell us more about it.
4. More chance for him to understand how to behave in order to reduce his penalty, to learn more about social relation and how to plan his future after being released.
5. He will be, mentally and physically busy in doing something good for him self and the society, reduce stress on him as well as on the every one else around him and feel less useless
Many other positive aspects could be listed if you like……
Thanks for your attention and Regards
Maroki
 
  • #29
Jeez, just use hamsters or rabbits.
Or maybe horses... horsepower :)
 
  • #30
Well… you missed to mention the donkey-power or the mule-power….which, you should know, are the most efficient among them all, but in all cases, palladin…..instead of funny nonsense why not opposing scientific or at least reasonable questions, if you have any?
 
  • #31
Maroki said:
Well… you missed to mention the donkey-power or the mule-power….which, you should know, are the most efficient among them all, but in all cases, palladin…..instead of funny nonsense why not opposing scientific or at least reasonable questions, if you have any?

Well... human powered generation of usable force has been around for a very long time.
On a low-scale level, say, a hand-crank radio or flashlight all is good. Or paddles for a canoe.
On a scale exceeding this it becomes functional ridiculous; given current technological alternatives.
 
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  • #32
Maroki said:
1. producing something (you said 4-5 kWh, maybe by using a more efficient equipment it could be increased ?) it would be good for the environment and the society while reducing the prisoner public cost.
It wouldn't really be good for the environment. Humans generate a lot of CO2 when producing mechanical work, and the fuel for humans requires a lot of fossil fuels to produce, distribute, and prepare.
 
  • #33
DaleSpam said:
It wouldn't really be good for the environment. Humans generate a lot of CO2 when producing mechanical work, and the fuel for humans requires a lot of fossil fuels to produce, distribute, and prepare.

Yeah you would be better off just burning food in a boiler to run a steam turbine then feeding it to people to do manual labor. :p
 
  • #34
a lot of CO2, when producing mechanical work?…yes ok, but how much?
maybe you do know that before the industrial revolution, before carbon fossil fuel came into the scene I mean, a farmer or one man could produce four (4) calories per each calorie spend in his work;
and maybe you do know also that thanks to the carbon fossil fuel now one man can produce many times more finished products then before (hundreds or even thousands times) but for each calorie it is burned ten (10) calories.
How much of CO2 is producing this type of mechanical work?
Let us go into numbers if possible please.
 
  • #35
Maroki said:
How much of CO2 is producing this type of mechanical work?
Let us go into numbers if possible please.
I am sure you can find the numbers with a bit of research.
 
<h2>1. How does using man-power to turn a massive generator work?</h2><p>Using man-power to turn a massive generator involves having a group of people work together to rotate a large wheel attached to the generator. This rotation creates mechanical energy which is then converted into electricity by the generator.</p><h2>2. What are the benefits of using man-power to turn a massive generator?</h2><p>One of the main benefits of using man-power to turn a massive generator is that it does not require any fossil fuels or electricity to operate. This makes it a sustainable and eco-friendly option for generating electricity. Additionally, it can be used in remote or off-grid areas where traditional power sources may not be available.</p><h2>3. How much man-power is needed to turn a massive generator?</h2><p>The amount of man-power needed to turn a massive generator depends on the size and capacity of the generator. Generally, a group of 10-20 people can produce enough energy to power small appliances or devices. However, larger generators may require more people or specialized equipment to turn them.</p><h2>4. Are there any limitations to using man-power to turn a massive generator?</h2><p>One limitation of using man-power to turn a massive generator is that it can only generate a limited amount of electricity. This makes it more suitable for small-scale or emergency use rather than powering large buildings or cities. Additionally, it may not be practical for long-term use as it can be physically demanding for the individuals involved.</p><h2>5. Can man-power generated electricity be stored for later use?</h2><p>Yes, man-power generated electricity can be stored in batteries or other energy storage systems for later use. This can be helpful in situations where the generator needs to be turned off or when there is excess energy being produced. However, the amount of energy that can be stored may be limited and may require additional equipment or resources.</p>

1. How does using man-power to turn a massive generator work?

Using man-power to turn a massive generator involves having a group of people work together to rotate a large wheel attached to the generator. This rotation creates mechanical energy which is then converted into electricity by the generator.

2. What are the benefits of using man-power to turn a massive generator?

One of the main benefits of using man-power to turn a massive generator is that it does not require any fossil fuels or electricity to operate. This makes it a sustainable and eco-friendly option for generating electricity. Additionally, it can be used in remote or off-grid areas where traditional power sources may not be available.

3. How much man-power is needed to turn a massive generator?

The amount of man-power needed to turn a massive generator depends on the size and capacity of the generator. Generally, a group of 10-20 people can produce enough energy to power small appliances or devices. However, larger generators may require more people or specialized equipment to turn them.

4. Are there any limitations to using man-power to turn a massive generator?

One limitation of using man-power to turn a massive generator is that it can only generate a limited amount of electricity. This makes it more suitable for small-scale or emergency use rather than powering large buildings or cities. Additionally, it may not be practical for long-term use as it can be physically demanding for the individuals involved.

5. Can man-power generated electricity be stored for later use?

Yes, man-power generated electricity can be stored in batteries or other energy storage systems for later use. This can be helpful in situations where the generator needs to be turned off or when there is excess energy being produced. However, the amount of energy that can be stored may be limited and may require additional equipment or resources.

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