Hydrogen Fuel: Generating Electricity with Water

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Discussion Overview

The discussion revolves around the feasibility of generating electricity through a closed-loop system involving the electrolysis of water to produce hydrogen and oxygen, followed by the combustion of hydrogen in the oxygen to release energy, which is then used to power an electric generator. The conversation touches on theoretical efficiency, energy losses, and practical limitations of such a system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant proposes a closed-loop system where water is electrolyzed into hydrogen and oxygen, and the hydrogen is then burned to generate electricity.
  • Another participant questions whether the energy produced in step 5 can effectively sustain the process in step 1, suggesting a lack of energy surplus.
  • A third participant argues that due to the symmetrical nature of the reaction, even with perfect efficiency, the energy output will never exceed the energy input.
  • A later reply provides calculations based on Faraday's constant, indicating that while idealized efficiency might suggest a 102% return, real-world factors such as heat loss and inefficiencies reduce this to about 50% efficiency.
  • The same reply notes that while the theoretical return may seem promising, practical limitations mean that the system would eventually run out of gas.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility and efficiency of the proposed system. There is no consensus on whether the energy output can sustain the process or whether the efficiency calculations presented are sufficient to support the idea.

Contextual Notes

Participants acknowledge that the calculations are based on idealized conditions and that real-world efficiencies are significantly lower due to various losses, including heat. The discussion highlights the complexity of energy conversion processes and the challenges in achieving a sustainable system.

Who May Find This Useful

Individuals interested in renewable energy systems, electrolysis, thermodynamics, and energy efficiency may find this discussion relevant.

chound
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Is it possible to create a structure where
1)water is electrolysed into oxygen and hydrogen
2)Hydrogen is burnt in the same oxygen obtained from step 1
3)This releases lot of energy and forms water
4)This energy can be used to rotate the armature of an electric generator
5)Electricity can be produced
6)The water in step 3 can be used in step 1 :zzz:
 
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Yup, yup, yup, yup, yup, and yup. Will "5" take care of "1"? Nope.
 
Since the reaction is symmetrical (water+energy=hydrogen+oxygen=water+energy, etc, etc, etc.), even if you had perfect efficiency, you'd still never get more energy out than you put in.
 
Let's do the math here and see what falls out. Per Faradays constant of electrolysis, it takes about 96,500 coulombs to generate 1 mole of hydrogen gas. After a couple of crunches, it appears to require about 32.9 kilowatts to generate 1 kilogram of hydogen gas. The electrical energy equivalent of a kilogram of hydrogen gas is 33.5 kilowatts. That looks promising, 102% efficiency!

Aye, but there is a rub, as usual. Those are idealized numbers - i.e., they assume 100% efficiency. You can take 17% straight off the top in heat loss. Now the numbers look like this 32.9 x 1.17 and 33.5 x 0.83 = 38.5 kw to get 29.1 kw.. down to 75% efficiency. And this is at laboratory efficiencies. In the real world, the true loss is about 1/3, so the real world efficiency is in the neighborhood of 50%. The bad news is you will run out of gas. The good news is it ain't all that bad a return.
 
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