Potential energy of water from electrolysis

[Buckleymanor]

Quote by Simon Bridge.
I don't think it adds anything to think about the magnet approach - it's another red herring.
You still need a net input of energy - which has to come from someplace else.

With regards to the magnet approach it is a red herring if you have to input the extra energy to raise it in the first place.
The above link might be of interest if it works, the link that is, as it might be possible to use the
water directly on it's return to produce electricity instead of a water wheel device.
The whole cycle should be more efficient.

 

[Simon Bridge]

That's also a red herring - the energy generation part of the cycle doesn't matter.
Do you really think that this can be made into a closed mill?

 

[CWatters]

The idea is to exploit their natural buoyancy... and it's a red herring: it's the energy needed to get/produce the gas at the bottom that is key to this ... you have to expand some gas against the surrounding air as well as break apart the molecular bonds of the water molecule.

I agree, but I have a question...

Imagine two different chemical reactions, one creating and expanding a bubble of Nitrogen and the other an equal size bubble of hydrogen. The pressure inside each bubble should be the same because the same volume of air is displaced (I think).

However the resulting hydrogen bubble has greater bouyancy than that of the Nitrogen bubble, so does that mean it would take more energy to expand the bubble of hydrogen than the bubble of nitrogen? It seems to me as if it would but I can't quite see why if the pressure and change of volume is the same.

 

[Buckleymanor]

You still need a net input of energy - which has to come from someplace else.
Jun6-13 11:39 PM


That's also a red herring - the energy generation part of the cycle doesn't matter.


Do you really think that this can be made into a closed mill?

I gave you a net input of energy from someplace else and it turns out now, to be a red herring as the energy part of the cycle according to you doesn't matter.
So there is no chance it being made into a closed mill.

 

[Simon Bridge]

I gave you a net input of energy from someplace else and it turns out now, to be a red herring as the energy part of the cycle according to you doesn't matter.

The energy generation phase is not a net input of energy, it's a net extraction of energy. The net input has to come from outside the cycle ... the details of how any energy is generated from inside the cycle is a red herring and it is not just my opinion, it's the law of conservation of energy.

Do you understand how the "water battery" in the video works? It's called a "Kelvin's Thunderstorm".
http://amasci.com/emotor/kelvin.html
... you have to separate the charges in the water somehow - which is where I'm guessing you think the external energy comes in? Aside from that, the energy for the electricity comes from the gravitational potential pulling the charged droplets from the end of the dripper - that does come from inside the cycle.... so: is it your contention that energy generated from within the cycle could, in principle, be used to keep the cycle going as well as provide useful work?

 

[Simon Bridge]

I agree, but I have a question...

Imagine two different chemical reactions, one creating and expanding a bubble of Nitrogen and the other an equal size bubble of hydrogen. The pressure inside each bubble should be the same because the same volume of air is displaced (I think).

It's easier to picture s you do this in water rather than in air - I made a long post about this.

The pressures would be the same - at all volumes.
The quantity of hydrogen and nitrogen in the bubble for the same volume and pressure may be different - though they are both diatomic. But if we use the ideal gas approximation, a bubble of hydrogen will be more buoyant than a bubble of nutrogen because the mass of hydrogen is much less.

However the resulting hydrogen bubble has greater bouyancy than that of the Nitrogen bubble, so does that mean it would take more energy to expand the bubble of hydrogen than the bubble of nitrogen?

No. The buoyancy force comes from the difference in pressure around the bubble vs the mass inside - not the energy used to make the bubble. In each case, the energy to expand the bubble is at least the same as the gravitational potential difference between the place the bubble is made and the top of the fluid.

It seems to me as if it would but I can't quite see why if the pressure and change of volume is the same.

It seems intuitive that something accelerating more must have had more energy put into it - but your analysis is correct: same volume, same pressure, same energy to expand.

The energy for the faster rise of the hydrogen comes from the descent of the same volume of regular air (or whatever the fluid is) - since the mass difference between hydrogen and air is greater than that for nitrogen and air, the hydrogen's ascent is faster.

You can model this for two ideal gasses with different mass per particle. PV=nRT ... creating the gas bubble involves changing the value of n in such a way that the pressure is constant ... and dW=P(V)dV

There are also wrinkles to do with gasses being compressable and pressure changing with altitude etc.

I'm half-expecting this thread to get locked real soon.
I cannot over-stress the usefulness of Simanek's buoyancy pages ... read through them several times.

 

[CWatters]

Thanks.

 

[Buckleymanor]

The energy generation phase is not a net input of energy, it's a net extraction of energy. The net input has to come from outside the cycle ... the details of how any energy is generated from inside the cycle is a red herring and it is not just my opinion, it's the law of conservation of energy.

Do you understand how the "water battery" in the video works? It's called a "Kelvin's Thunderstorm".
http://amasci.com/emotor/kelvin.html
... you have to separate the charges in the water somehow - which is where I'm guessing you think the external energy comes in? Aside from that, the energy for the electricity comes from the gravitational potential pulling the charged droplets from the end of the dripper - that does come from inside the cycle.


... so: is it your contention that energy generated from within the cycle could, in principle, be used to keep the cycle going as well as provide useful work?

Energy generated from within the cycle would not be able to keep the cycle going as well as provide usefull work, without breaking conservation laws.
If you were to combine the two main features of the proposed mill the use of hydrogen and it's use in a cell and the recovery of electricity using Kelvin's Thunderstorm.

A hydrogen fuel cell operating at 25°C has a maximum theoretical efficiency of 83%, even though the fuel cell is extracting all the electrical energy possible

So presumably you would have to find around 20% from Kelvin's Thunderstorm to keep the cycle going and provide usefull work, which does not seem like much but I am not sure how efficeint the Thunderstorm can be or how reliable the theoretical efficeincy of the fuel cell is.

 

[russ_watters]

So presumably you would have to find around 20% from Kelvin's Thunderstorm to keep the cycle going and provide usefull work, which does not seem like much but I am not sure how efficeint the Thunderstorm can be or how reliable the theoretical efficeincy of the fuel cell is.

Ok, that's enough of this thread. You are looking for perpetual motion here because you are assuming Kelvin's Thunderstorm itself is a free energy device by producing electricity without an input of mechanical energy. You should stop looking for something that doesn't exist. Thread locked.