Gravity as an energy source?

[Energia]

I also have searched the Net very extensively on this topic. Have not came across any posting. Hydro-electric energy storage in principle is the same thing and they are used widely to store massive amount of energy by the Power Utility sectors. The problem is that for it to work one requires two adjacent lakes at different heights and it's efficiency is around 70% (multiplicative of the efficiencies of hydro-turbines and pumps). I have this idea of hauling very large mass of (1000s of tons) scrap lead (from car batteries) top of grand canyon (more than a mile up) and use electirc motor /generator (could be one unit acually..I have to think). The system can store massive amount of energy in a very tiny place and the efficiency can be more than 85%. It can be used anywhere where there are such great vertical fall or even on mountain slopes (the efficiency will be slightly reduced because of friction)

[gcol]

Have corresponded with a farmer in Portugal intending to use wind power to haul weights up a tower or hill, and there is a chap who drives his lorry up a hill and generates power as it runs down again.

 

I think such systems work at small scales if you have the space, but water is more practical commercially.

[JustStuit]

I also have searched the Net very extensively on this topic. Have not came across any posting. Hydro-electric energy storage in principle is the same thing and they are used widely to store massive amount of energy by the Power Utility sectors. The problem is that for it to work one requires two adjacent lakes at different heights and it's efficiency is around 70% (multiplicative of the efficiencies of hydro-turbines and pumps). I have this idea of hauling very large mass of (1000s of tons) scrap lead (from car batteries) top of grand canyon (more than a mile up) and use electirc motor /generator (could be one unit acually..I have to think). The system can store massive amount of energy in a very tiny place and the efficiency can be more than 85%. It can be used anywhere where there are such great vertical fall or even on mountain slopes (the efficiency will be slightly reduced because of friction)

Conservation of Energy will say it takes at least as much energy to bring the weight up as it will exert when pulled down by gravity. Also, more will we wasted in heat, sound, etc. Therefore, you would need a more than 100% efficient system to make it work.

[ecoli]

My idea was actually something along the lines of having some sort of generator that created energy while people walked over it, or something. Maybe build a city over it. I don't know how feasible this is, though.

 

There was a house like this that some engineers built for a competition (don't remember which one) The floor tiles all had springs, so the mechanical energy of people walking across the rooms could be harvested...

 

They had other things like that too.

[Klaynos]

There was a house like this that some engineers built for a competition (don't remember which one) The floor tiles all had springs' date=' so the mechanical energy of people walking across the rooms could be harvested...

 

They had other things like that too.[/quote']

 

Always makes me wonder how much energy they cost to create... especailly for a single or few projects....

[swansont]

There was a house like this that some engineers built for a competition (don't remember which one) The floor tiles all had springs' date=' so the mechanical energy of people walking across the rooms could be harvested...

 

They had other things like that too.[/quote']

 

The problem with that is that harvesting human energy is incredibly inefficient. You'd likely get more energy by directly burning the food instead of eating it and doing the exercise.

[Kyle]

What about launching objects out of and into gravitational fields?

This has bothered me for a long time and I may even have posted it here before. Suppose I take a very large mass and I use a certain amount of force to get it out of Earth's noticeable gravitational field, then aim it towards a much larger field like Jupiter (where I have previously placed a device that can harvest kinetic energy as objects fall). If you can put aside the difficulty in doing so, I get this large mass to land on my machine and I am able to contain all of its falling energy. Wouldn't I have more energy than I put in, since the weight of the object is greater in the larger field?

[Kyrisch]

That's highly impractical because Jupiter's intense gravitational field will make placing anything there incredibly hard not to mention the lack of solid ground to place it on. Not only that, but even if it harvests the energy we would have to bring it back to Earth to get at that energy.

 

And what does that mean? A whole lot of wasted energy mucking around in space.

[Kyle]

I think you've missed the point of the question. There are a ton of assumptions, I understand. It's not practical, this too I understand. But how do the Physics work out?

[Kyrisch]

I think that mucking around in space to plant and retrieve the harvester will take enormous amounts of energy -- way too much for gravity, a very weak for, to reconcile for.

[Sisyphus]

Yeah, the physics works out. In theory, you'd get positive energy out of moving something from Earth to Jupiter. In practice, of course, its nonsense.

[Kyle]

The feasibility of this set-up is irrelevant.

I'm wondering if science allows for the system. Would more energy actually be extracted than what was put in, if we forget about all the external details like how the machine gets there, how the energy gets back? Hopefully someone can look at this hypothetically instead of being unflinchingly realistic.

 

EDIT

Yeah, the physics works out. In theory, you'd get positive energy out of moving something from Earth to Jupiter. In practice, of course, its nonsense.

Thank you!

[DrCloud]

I still don’t understand where the energy comes from...

 

This business with the steel ball and the magnet is an interesting puzzle, and we need a good classical physicist to help out, because it's a little confusing to me, too. Swanson's brief comment helps, but here's more detail, via a couple of things to consider.

 

First, energy is just force applied over a distance. So the steel ball gains gravitational potential energy relative to the surface it started on because the force applied by the magnet to the ball acts over the lifting distance.

 

Second, suppose we do this same thing in the absence of gravity. Then the steel ball would accelerate because of the force acting on its mass and come to a stop when it smacks the magnet, dissipating its kinetic energy as heat. With gravity, it does the same thing (or not), depending on the relative strengths of the force on the ball from the magnetic field and from gravity. In a sense, then, all that gravity is doing is reducing the effectiveness of the magnetic field in accelerating the ball -- decreasing the magnetic field's strength, in effect.

 

So your puzzling question comes down to this: when a magnet accelerates a mass, which results in kinetic energy, where did that energy come from? Where was it in the first place (energy, after all, needs to be conserved in this little thought experiment)?

 

It seems pretty clear that the kinetic energy must have started out as potential energy, potential energy stored in the magnetic field and its interactions with the crystal structure of the atoms of iron in the ball, right? As the ball accelerates, that potential energy is converted to kinetic energy; this means that the closer the ball is to the magnet to begin with, the less magnetic potential energy there is -- that is, the field isn't constant in space, something we already knew. So this is consistent.

 

With this in mind, we can add gravity. With gravity, the ball doesn't accelerate so fast, because the magnetic potential energy is being converted both to kinetic energy and to gravitational potential energy.

 

I hesitate to say "QED", but I think I may have persuaded myself, at least. Maybe we can get a real physicist to weigh in. HPH

[CPL.Luke]

the only reasonable method of harvesting energy from the gravitational potential that I can think of would be to fly out to the asteroid belt (or the oort cloud) and destabalise a few asteroids orbits so that they fall back towards the sun (passing by the earth). then either slam the asteroids into each other and harvest the heat or slow them down with a powerful magnetic field and get the energy out of that somehow.

[pHoToN_gUrL]

could gravity be used as a feasible source of energy?

Gravity can be used as a source of energy but it is not efficient since you have to spend energy to obtain the gravitational potentional energy to begin with. And once the gravitational potentional energy is converted to kinetic energy to do work, some energy is always lost to heat, sound, etc. You can't even obtain the same amount of energy back. But here is some inefficient ways of using gravity to do work:

1. Counterweights allow us to move very heavy objects easily. They do this by offsetting the object's weight, using gravity acting on the counterweight.

2. Falling water, driven by the force of gravity, can be used to turn water wheels and turbines, to grind grain or generate electricity.

3. Many clocks, such as my father-in-law's cuckoo clock, are driven by a system of falling weights. The energy comes directly from gravity.

[pHoToN_gUrL]

I have a theory on Gravity, and how we can use it positively. But first I need assurance that it will never used for evil. Will you take my word seriously?

May be....May be not

Ideas are wellcome as long as they are based on scientific facts.

To begin with, evil does not sound TOO scientific so may be you should try the another place hun where they accept what ever they hear and won't ask you to prove your point SCIENTIFICALLY.

[wpenrose]

Sorry if this has already been posted, but this has been bugging me for a while and a search didn't turn up anything. We keep talking about alternative energy sources everywhere when there is a constant energy around us all the time. What I want to know is, could gravity be used as a feasible source of energy?

 

Yes. It's called hydroelectric power.

 

Dangerous Bill

[lxxvii24]

hmmm you guysve got wuite a lot down ur sleeves... i start by sayin am a fan of generating electricity from gravity. but lyk a friend stated eaerlier, G is small making the force generated small and also the amount of gravity depends on the forcees in connection which is m1 and m2.... no one seem to be makin mention of the masses.... if we talk off massive sizes then comes the question of gravity being significant.... according to newton's definition gravity exists btw any two particles.... tiny masses tiny impact

[pHoToN_gUrL]

hmmm you guysve got wuite a lot down ur sleeves... i start by sayin am a fan of generating electricity from gravity. but lyk a friend stated eaerlier, G is small making the force generated small and also the amount of gravity depends on the forcees in connection which is m1 and m2.... no one seem to be makin mention of the masses.... if we talk off massive sizes then comes the question of gravity being significant.... according to newton's definition gravity exists btw any two particles.... tiny masses tiny impact

 

 

what do you mean the amount of gravity depends on forces in connection? gravity IS a force it self, so what's the connection?

gravity is significant when massive objects are involved, but the point is that you can't use gravity to do work unless you first store it as potentioal enegry. And the storing process is a work it self so the catch is that the entire process would not turn out to be efficient.

But what i am most curious about at this point is that, how would you go about generating electricity from gravity?

[YT2095]

But what i am most curious about at this point is that' date=' how would you go about generating electricity from gravity?[/quote']

 

you Can`t directly, you can only exploit it as a storage medium for work already input.

 

 

the really IS No Such Thing as a Free Lunch

[gcol]

you Can`t directly' date=' you can only exploit it as a storage medium for work already input.

[/quote']

 

How about dropping an iron slug through a coil. If the slug comes to rest inside the coil, have you not converted its gravity induced kinetic energy directly into electrical work? (silly thought perhaps, but there you are.)

[YT2095]

an Iron slug? or a Magnet?

 

a magnet + movement would indeed create electricity inside the coil, the Gravity hasn`t created it though.

[pHoToN_gUrL]

How about dropping an iron slug through a coil. If the slug comes to rest inside the coil, have you not converted its gravity induced kinetic energy directly into electrical work? (silly thought perhaps, but there you are.)

I think this makes sense , but won't you have to move the iron up first and then drop it? which means you need to do work first...so would it be efficient to make electricity this way?

[pHoToN_gUrL]

" If a falling mass could be made to convert its gravitational acceleration into electricity which was then used to create a magnetic field that opposed the pull of gravity, it might be bounced up and down on the repulsion of its own magnetic field. Again a small driver pulse might create a huge displacement of mass that could be put to use doing mechanical work. More advanced units might be constructed like two railguns muzzle to muzzle vertically with a mass bounced between them. If a unit of this type were constructed in a shaft, then a loss of containment at the bottom would drop the mass harmlessly down the shaft while a loss of containment at the top would put a payload in orbit. Imagine putting satellites up by dropping them."

 

taken from ==> http://www.virtualchaos.org/science/free.html

[pHoToN_gUrL]

an Iron slug? or a Magnet?

 

a magnet + movement would indeed create electricity inside the coil' date=' the Gravity hasn`t created it though.[/quote']

gravity caused the movement and hence the electricity, right?