Open Systems

[LibreEnergia]

Moving the piston is doing nothing more than enlarging the tank the gas is stored in-->but the amount of gas never changes,thus the energy contained within that gas also never changes-->joules per ltr remains.

That is where you go wrong..

the product of P1V1 = P2V2 is only true IF the temperature of the gas remains constant.

Remember, the ideal gas law says p1V1/T1 = p2V2/T2 ... and that's why the subject is called thermo-*dynamics*. There are many ways to expand or compress gas and what happens to the net internal energy of the working fluid depends on the cycle chosen. Your assumptions would only be true for reversible adiabatic processes.

Good luck getting any net work out of such a system, or even building it in the first place.

[tinman]

  I might be blind but how does the environment give energy to this system?

Profitis, who gets taxed?  Well, the extra energy required to compress the gas comes from power supply. The piston work comes from there, the power supply. Unless someone has proven that pressure has little effect on the power required from electrolyis.

No-the extra energy drawn from the power supply when the pressure rises is disipated as heat energy due to the resistance dropping between the electrodes in the electrolisis cell. As the resistance has dropped,then the current increases,and as the current has increased,then so dose the heat produced by the cell.

[tinman]

That is where you go wrong..

the product of P1V1 = P2V2 is only true IF the temperature of the gas remains constant.

Remember, the ideal gas law says p1V1/T1 = p2V2/T2 ... and that's why the subject is called thermo-*dynamics*. There are many ways to expand or compress gas and what happens to the net internal energy of the working fluid depends on the cycle chosen. Your assumptions would only be true for reversible adiabatic processes.

Good luck getting any net work out of such a system, or even building it in the first place.

Here is the problem you have with the !ideal gas law!-HHO is not an ideal gas.
Second thing to remember is that regardless of volume and pressure,the mass !n!(the number of moles) of gas is constant. So regardless of pressure or volume the mass(moles of gas)remain the same. 241.8KJ of energy is produced for every mole of H2 burned.

I repeat--> the mass (moles of gas)remain a constant regardless of pressure or volume
1 mole of H2 will produce 241.8KJ of energy when burned.
Moving the piston with the gas pressure dose not change the mass of the gas-->dose not change the mole amount of gas,and dose not change the stored energy within that fixed mass of gas.
PV is not gas mass(moles of gas) amount.

So as i said,the stored energy within the gas dose NOT change because of a change in PV.

The PV can change without effecting the stored energy within the gas-->the given P can perform work upon the piston without effecting the mass(mole)amount of the gas. As the moles of gas has remained the same,then the energy contained within that gas is unchanged when subject to a pressure drop.

[pomodoro]

No-the extra energy drawn from the power supply when the pressure rises is disipated as heat energy due to the resistance dropping between the electrodes in the electrolisis cell. As the resistance has dropped,then the current increases,and as the current has increased,then so dose the heat produced by the cell.

What about the energy used to compress the  gas? Potential energy stored in the gas can only come from the battery. Surely the electrolysis stops as the pressure rises, as the Nernst equation demands more voltage due to a higher partial pressure of the gasses?  Yes some of the energy goes into heat, the rest into potential energy (pressure) of the gas?

[MarkE]

And the temperature would change why?
The gas temperature will remain at room temperature,as the pressure in the cylinder dose not go any higher that the source that feeds it.

LE's explanation was generic.  One can traverse in either direction.  In your case, you have a certan amount of battery energy that results in broken chemical bonds and a certain amount of energy in the form of PE in the gas.  You then propose to expand the cylinder.  Your earliest proposition was that process could deliver external work without removing any of the chemical potential of the gas, which everyone agrees on, but also without losing potential energy from the gas, which multiple people have tried to educate you is flat wrong.  As Pomodoro has pointed out you can just set the electrolysis aside as whatever energy goes into breaking the bonds you can get back.  Now, all you have is a hot gas engine that you assert can deliver free energy.