Extracting energy out of hydrogen and oxygen

  • Thread starter Jacquesl
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Main Question or Discussion Point

The best method of extracting energy out of hydrogen and oxygen

Which method will deliver the best energy output?

(1) Fuel cell
(2) Burning the hydrogen and oxygen and make some steam and send it to a turbine
(3) Internal combustion engine //piston like a car engine

And which method will be the best adorable
 

Answers and Replies

  • #2
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apparently the most efficient is Fuel Cell Technology, but it needs a lot of time to start being usefull due to the current infrastructure of the world. My second choice has to be ICE engines, hydrogen has a combustion efficiency of near 60% as compared to the 40% of gasoline. Steam running turbines comes last for me, its really not a practical/usefull/ or liked cycle, i wouldn't ever do it. anyway u sound very interested in this subject, may i ask why?
 
  • #3
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What’s the efficiency of electrolysis of water?
 
  • #4
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Depends on the cycle used. some cycles are joint heating + electrolysis and those are the most efficient. as for electrolysis as is u might want to look it up on the internet..
 
  • #5
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I have: on Wikipedia

“The energy efficiency of water electrolysis varies widely. Some report 50–70%[1], while others report 80–94%.[2] These values refer only to the efficiency of converting electrical energy into hydrogen's chemical energy. The energy lost in generating the electricity is not included. For instance, when considering a power plant that converts the heat of nuclear reactions into hydrogen via electrolysis, the total efficiency is more like 25–40%”

To me it have multiple answers
 
  • #6
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that's why i didn't give u an answer. Some researches say that u can go higher than 88% if u use a catalyst in the water solution to conduct electricity better, i don't remember what the catalyst Potassium i think. heating the water mixture results in lowering the amount of electricity needed to break the water molecules. another way would be to use heat and zinc which joins with the oxygen in the water resulting in free hydrogen, this is a reversible process where the zinc is merely a catalyst and breaks free in another process. so reaching above 70% in electrolysis is perfectly logical.but its still a researched area i think
 
  • #7
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Yip, I understand now, hydrogen has its hidden stuff. But still involving electricity + heat to get hydrogen will be better of because, almost no application makes good use of heat beside nuclear.

And involving zinc will produce Zinc Oxide (Zn0) that a waste, I would be better to make something self sustained hydrogen generator that will totally screw the world over.
 
  • #8
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yeah but there is a way to recover the ZnO cheaply.
 
  • #9
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heat??

Yip, I understand now, hydrogen has its hidden stuff. But still involving electricity + heat to get hydrogen will be better of because, almost no application makes good use of heat beside nuclear.
QUOTE]

Just wondering about this statement.... Heat is what drives any thermodynamic-type engine. What do you think moves a piston in an engine? Do you know of some type of coal power plant that doesn't use steam turbines much as a nuclear plant? Hydrogen is just one of the ways to store some potential chemical (and eventually thermal) energy. Much like ethanol, oil, etc.

I am not trying to pick on you Jacques -- but statements such as this IMO slow down our progress of moving towards alternative energy. We want to give up on wind, hydrogen, solar, etc. because it is too hard -- oil and nuclear are easy.
 
  • #10
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clarification

wxrocks;1272614 Just wondering about this statement.... Heat is what drives any thermodynamic-type engine. What do you think moves a piston in an engine? Do you know of some type of coal power plant that doesn't use steam turbines much as a nuclear plant? Hydrogen is just one of the ways to store some potential chemical (and eventually thermal) energy. Much like ethanol said:
what he meant about using heat is in the production of Hydrogen not in the use of hydrogen. the topic of the conversation was how to produce hydrogen in the most efficient way. and one of those ways was to use heat +electricity to produce the hydrogen in a very efficient manner
 
  • #11
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I am not trying to pick on you Jacques
Its ok, no problem.

I just don’t understand why no body can convert heat to useable electricity, but it takes huge amounts of electricity to product heat?

And the same with producing hydrogen, I’m seen on TV how thermite makes ice explode, because of the extreme heat that makes the hydrogen and oxygen splits.

So ways to split water:

(1) Extreme heat
(2) Electrolysis of water

Are there any other ways?
 
  • #12
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Chemical by removing it from other material, like from Methanol or something like that.
Heat doesn't produce electricity directly but its a combination of heat and pressure. and their are losses due to efficiencies.but heat always produces electricity, there's no better way to produce electricity than heat. and btw. it takes a huge amount of electricity to produce heat, and it takes a lot of heat to produce electricity.
 
  • #13
russ_watters
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The course of the discussion doesn't exactly fit the OP: are you asking about the use of hydrogen/oxygen for energy storage or just the efficiency of combustion of hydrogen and oxygen itself?

As an energy storage system, electrolysis->hydrogen/oxygen->fuel cells fall far short of ordinary batteries in terms of efficiency.
I just don’t understand why no body can convert heat to useable electricity, but it takes huge amounts of electricity to product heat?
I'm not following. The conversion of electricity to heat is exactly 100% efficient, but it is irreversible. Due to the laws of thermodynamics, conversion of heat to electricity involves some entropy loss. But obviously we can and do convert heat to useable electricity.
 
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  • #14
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it takes a huge amount of electricity to produce heat, and it takes a lot of heat to produce electricity.
What sounds logic in a way I don’t want to belief, but maybe there a lacking something nobody yet know that can be added to the laws of thermodynamics, that makes the energy more, it’s like a oxidizer in a fire, the more oxygen the bigger your faster it burns, probably the same with fuel cell, if your use hydrogen and Stored oxygen from a tank you get a boost


To my understanding, using that heat to produce steam and then transfer it to a steam turbine, will have the highest effect in energy gain, thermocouples won’t be that nice.

I’m actually asking both:

hydrogen/oxygen for energy storage //the best method of doing

and then the efficiency of combustion of hydrogen and oxygen might play a big key role
 
  • #15
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Russ what is the comparison in efficiency between a PEM fuel cell and an ICE combustion., both using Hydrogen.
 
  • #16
mrjeffy321
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[...] between a PEM fuel cell and an ICE combustion., both using Hydrogen.
A fuel cell will output electrical energy (+ heat) and an ICE will deliver an output of mechanical energy (+ heat). Which is it that you want to use? I think it would only be fair to compare the efficiencies when comparing the energy ouput in the same form, so at least one of the outputs (either from the ICE or the fuel cell) is going to have to be put through another (lossy) conversion.

PEM fuel cells have an efficiency of about 35% to 60% (chemical to electrical),
http://www.rmi.org/sitepages/pid556.php [Broken]
http://americanhistory.si.edu/fuelcells/pem/pemmain.htm

Whereas ICEs have efficiencies probably on the order of about 30-40% or so, I would think, but I have seen estimates much lower,
http://www.fueleconomy.gov/feg/atv.shtml
says 15% conversion from chemical to 'moving you car down the road', saying that 62.4% is lost during the initial combustion process and then with further loses down the line.
 
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  • #17
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well unfortunately its to give electricity, so i guess a PEM would be better for such a use.
 
  • #18
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It’s just to bad that the big fuel cells only comes in units of +- 88kw, for car purpose only and each unit will cost a banks money.
 
  • #19
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that's why battery powered cars are too heavy, because u got stacks and stacks over each other, that includes fuel cells too
 
  • #20
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No doubt. My brain are out of ideas. :(
 
  • #21
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I have a question as well on your comment Jacques about the cost of producing electricity to split out the hydrogen from water.
What about using waste (trash) to create heat in order to produce the electricity needed to create the hydrogen fuel?
 
  • #22
russ_watters
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If that cost less than getting electricity the normal ways, wouldn't power plants already do it?
 
  • #23
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Actually, Russ, power plants cannot use waste to produce electricity due to EPA rules at this time. However, residential or car use would not be under the EPA's eyes. Using heat produced by burning trash to spin a generator (no matter how small) would be effective and then running the residual heat through a series of water wash and charcoal scrubber would seem very efficient if one could figure out how to minimize it and place it in the trunk. Then you just make a stop and dump some trash in every time you need to charge the battery you use for the hydrogen release. I can' remember what it was that would take half the electricity to release the hydrogen other than water, though??? Does that make sense?
 
  • #24
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My thought on the hydrogen extraction was that it takes about 1.23 Hz to get hydrogen out of water (H20), but hydrogen combined with something else is half as easy to pull out (about 0.5 Hz) but I can't remember what it was. I understand what you are saying about being the carrier. Thank you.
 
  • #25
mrjeffy321
Science Advisor
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My thought on the hydrogen extraction was that it takes about 1.23 Hz to get hydrogen out of water (H20), but hydrogen combined with something else is half as easy to pull out (about 0.5 Hz) but I can't remember what it was. I understand what you are saying about being the carrier. Thank you.
What are you talking about? Hertz? Frequency has nothing to do with it.
 

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