Using man-power to turn massive generator

[pallidin]

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.

 

[Dale]

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.

 

[QuantumPion]

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

 

[Maroki]

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.

 

[Dale]

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.

 

[DaleSwanson]

The CO2 animals exhale should be a net neutral as far as total CO2 in the atmosphere goes. The CO2 came from plants which captured the CO2 that was already in the atmosphere. The plants would have released that CO2 when they decayed if they weren't eaten.

The only carbon which affects the global total CO2 levels is carbon which is either being sequestered long term, or being released from long term sequestering, in other words, fossil fuels. Modern farming certainly uses lots of external energy provided mainly by fossil fuels, so it is still valid to say that humans consuming extra food will raise the CO2 levels. To answer how much the levels will raise one needs to find out how much fossil fuel was burned to produce the extra food.

As for the amount of energy needed to produce food, a brief search shows widely varying numbers. Many sites seem to cite one study in particular. It may be a good idea to read through it if you have an interest:

http://dieoff.org/page55.htm

 

[Maroki]

Thank you Dale, this is a nice and constructive approach I think may really help. I will read that and be back ASAP.

 

[Dale]

Modern farming certainly uses lots of external energy provided mainly by fossil fuels, so it is still valid to say that humans consuming extra food will raise the CO2 levels. To answer how much the levels will raise one needs to find out how much fossil fuel was burned to produce the extra food.

Yes. That and also you need to consider what the impact of agricultural land use is. E.g. if you clear cut an acre of rainforest in order to plant food you have a huge carbon impact from that also.

 

[DaleSwanson]

Yes. That and also you need to consider what the impact of agricultural land use is. E.g. if you clear cut an acre of rainforest in order to plant food you have a huge carbon impact from that also.

Good point, I over looked that originally, probably because I was thinking mostly in terms of the US where I don't think it is as likely to happen. It were certainly be harder to estimate the impact of converting forest to crops, since it is a one time only event. I suppose you could find numbers for how much forest is being converted to crops annually worldwide and then figure out how much less carbon the living crops hold than the living forest.

 

[Maroki]

Howuuu…..Thanks to both Dales...here "[URL in this report dated 1994 there is every thing one should know, analysing, expanding and unfortunately confirming, the models already perfectly foreseen back in 1972 by The_Limits_to_Growth..."[URL

And here ……. "[URL

…..“In a very real sense, we are literally eating fossil fuels. However, due to the laws of thermodynamics, there is not a direct correspondence between energy inflow and outflow in agriculture. Along the way, there is a marked energy loss. Between 1945 and 1994, energy input to agriculture increased 4-fold while crop yields only increased 3-fold.11 Since then, energy input has continued to increase without a corresponding increase in crop yield. We have reached the point of marginal returns.”

More over ….
“there are two separate forms of (human) energy input: Endosomatic energy and Exosomatic energy. Endosomatic energy is generated through the metabolic transformation of food energy into muscle energy in the human body. Exosomatic energy is generated by transforming energy outside of the human body, such as burning gasoline in a tractor. This assessment allowed the authors to look at fossil fuel input alone and in ratio to other inputs.
Prior to the industrial revolution, virtually 100% of both endosomatic and exosomatic energy was solar driven. Fossil fuels now represent 90% of the exosomatic energy used in the United States and other developed countries.17 The typical exo/endo ratio of pre-industrial, solar powered societies is about 4 to 1. The ratio has changed tenfold in developed countries, climbing to 40 to 1. And in the United States it is more than 90 to 1.18 The nature of the way we use endosomatic energy has changed as well.
The vast majority of endosomatic energy is no longer expended to deliver power for direct economic processes. Now the majority of endosomatic energy is utilized to generate the flow of information directing the flow of exosomatic energy driving machines. Considering the 90/1 exo/endo ratio in the United States, each endosomatic kcal of energy expended in the US induces the circulation of 90 kcal of exosomatic energy. As an example, a small gasoline engine can convert the 38,000 kcal in one gallon of gasoline into 8.8 KWh (Kilowatt hours), which equates to about 3 weeks of work for one human being.19” ….
…..10 kcal of exosomatic energy are required to produce 1 kcal of food delivered to the consumer in the U.S. food system. This includes packaging and all delivery expenses, but excludes household cooking).20 The U.S. food system consumes ten times more energy than it produces in food energy. This disparity is made possible by non renewable fossil fuel stocks. …..”

Therefore I would like to conclude that since most of the energy we consume the way we do it now is causing from one side the running down of natural resources and from the other side, pollution and climate change, whether we like it or not, we will have to better structure our mind in order to make good use of every single calorie, the sooner we do that and the less pain we will have facing the next coming revolution.

 

[Maroki]

The answer of my friends, is blown in the wind...?

 

[ettecar99]

I see this thread ended long ago but giving this a shot...

Going back to the original question of using gears to power a large generator... What I have been wondering about is whether I could put together 1 or 2 of the 250 watt solar panel kits and use it to power a small electrical motor which would be used to turn something like a 3-8 kw generator for my home. This would cost significantly less than outfitting my house with enough solar to produce the same amount of electricity but would likely need a gearing system to spin the big generator fast enough. I am assuming I am missing something here or this would be common practice?

I have spun a 5 kw gen by hand and can light a light bulb, it isn't difficult to turn, but needs to be spun pretty fast to hit full output obviously.

OK you smart people, what do you think? :-)

 

[russ_watters]

Welcome to PF!

Mechanical power in = electrical power out. You can't get something for nothing.

That generator that you spun by hand that was connected to one light bulb: try connecting 10 light bulbs to it and see if it is harder to spin.