Extracting energy out of hydrogen and oxygen

  • Thread starter Jacquesl
  • Start date
  • #1
136
1
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
150
0
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
136
1
What’s the efficiency of electrolysis of water?
 
  • #4
150
0
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
136
1
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
150
0
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
136
1
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
150
0
yeah but there is a way to recover the ZnO cheaply.
 
  • #9
131
0
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
150
0
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
136
1
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
150
0
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
Mentor
21,502
8,544
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.
 
Last edited:
  • #14
136
1
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
150
0
Russ what is the comparison in efficiency between a PEM fuel cell and an ICE combustion., both using Hydrogen.
 
  • #16
mrjeffy321
Science Advisor
876
1
[...] 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.
 
Last edited by a moderator:
  • #17
150
0
well unfortunately its to give electricity, so i guess a PEM would be better for such a use.
 
  • #18
136
1
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
150
0
that's why battery powered cars are too heavy, because u got stacks and stacks over each other, that includes fuel cells too
 
  • #20
136
1
No doubt. My brain are out of ideas. :(
 
  • #21
3
0
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
Mentor
21,502
8,544
If that cost less than getting electricity the normal ways, wouldn't power plants already do it?
 
  • #23
3
0
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
3
0
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
876
1
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.
 
  • #26
chemisttree
Science Advisor
Homework Helper
Gold Member
3,686
691
What's the frequency, Kenneth?
 
  • #27
Lok
555
23
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

This thread is degenerating a bit.

In theory all methods are fine but in practice all have losses.
H2 and O2 are too corrosive to burn in a chamber and they produce a hot flame of 1600 Co which can melt steel (translated as intense surface corrosion).

The fuel cell is best imo and i've built a small one at home of 0.6-0.7V(big losses, no platinum). It should be cheap to build nowadays.

Hydrogen production and storage are the biggest problems of the three. It will take a lot of energy to store a fraction of that energy into hydrogen gas.
Oxigen comes free as it is basically algae excrement :P.
 
  • #28
apparently, an advantage of using an ICE instead of a fuelcell with hydrogen is that fuelcells require very pure hydrogen, but an engine will burn any old crap...
 
  • #29
Lok
555
23
apparently, an advantage of using an ICE instead of a fuelcell with hydrogen is that fuelcells require very pure hydrogen, but an engine will burn any old crap...

Fuel cells do not require pure hidrogen, not that pure hydrogen is that hard to get. Engines are actually more fussy about purity, I mean a constant purity that it is set.
 
  • #30
mheslep
Gold Member
317
728
In theory all methods are fine but in practice all have losses.
H2 and O2 are too corrosive to burn in a chamber and they produce a hot flame of 1600 Co which can melt steel (translated as intense surface corrosion).
. Gas turbines using hydrogen have been built. There have also been several demonstrations of burning hydrogen directly in otherwise unmodified internal combustion engines. Hydrogen and natural gas flame temperatures are very similar.
 
  • #31
Lok
555
23
Hydrogen and natural gas flame temperatures are very similar.

This usually explains why steel (not pig iron) took so much time to be truly molten. It melts at about 1500 plus give Celsius.From a historical point of view where natural gas was very abundant. No.
 
  • #32
mheslep
Gold Member
317
728
... It melts at about 1500 plus give Celsius.From a historical point of view where natural gas was very abundant. No.
Yes. There's a lot of engineering in the heat management of gas turbine engines. Heat resistant metals or ceramics are used, and the combustion gasses are rapidly expanded which cools them.
http://www.energymanagertraining.com/power_plants/Gas_Turbines.htm [Broken]
http://www.netl.doe.gov/technologie...shelf/igcc-h2-sygas/Using H2 as a GT Fuel.pdf
 
Last edited by a moderator:
  • #33
1,565
7
Fuel cells do not require pure hidrogen, not that pure hydrogen is that hard to get. Engines are actually more fussy about purity, I mean a constant purity that it is set.

This is incorrect. Fuel cells are very easily poisoned by CO and H2S. CO and sulfur based impurities bond with the platinum on the anode side of the cell removing reactions sites for the hydrogen. CO can be easily removed by applying a potential across the cell but sulfur based compounds have stronger bonds and sulfur sticks to just about everything so removing it can be more difficult.

Often, bi-metal catalysts are used on the anode side of a fuel cell to help reduce the effects of poisoning. Pt-Ru is a very common catalyst but the added Ru makes it more expensive.

Heat resistant metals or ceramics are used

Do they actually use ceramics commercially in heat turbines these days? I thought the failure rate of ceramics was still to unpredictable.
 
  • #34
mheslep
Gold Member
317
728
Do they actually use ceramics commercially in heat turbines these days? I thought the failure rate of ceramics was still to unpredictable.
I can't reference a model number, only this at the moment:
http://www.energymanagertraining.com/power_plants/Gas_Turbines.htm [Broken]
 
Last edited by a moderator:

Related Threads on Extracting energy out of hydrogen and oxygen

  • Last Post
Replies
7
Views
6K
  • Last Post
Replies
4
Views
3K
Replies
11
Views
2K
Replies
1
Views
3K
Replies
12
Views
6K
Replies
2
Views
3K
  • Last Post
Replies
1
Views
1K
Top