Electrolysis of water for biosphere 1

[JamesSmith]

Hello.
I am evaluating the potential for using Electrolysis of water as part of a biosphere support system.
I am not chasing 'perpetual energy' or anything like that.
As I understand water electrolysis, it may be possible to keep a process active as long as new water is supplied.
However, I have also heard that such a thing simply will not work, as the resources used would not be enough to keep the process going.

I feel this is important. If I can get such a process going, verious usable resources could be produced, such as power, heat, distilled water, oxygen, etc. etc.

Please help me with this if you can -anyone?

 

[kenvlach]

"As I understand water electrolysis, it may be possible to keep a process active as long as new water is supplied.'
---It can keep going forever given water, electricity and inert electrodes. And, it is possible to recycle the water.

"However, I have also heard that such a thing simply will not work, as the resources used would not be enough to keep the process going."
--- Of course, by the Second Law of Thermodynamics, it cannot keep running by itself in a closed-loop process. Every time you transform energy from one form to another, you will lose a portion. You do need some external energy input.

Suppose you want to utilize the H2 and O2 created by hydrolysis in a fuel cell to create the electricity for further electrolysis, and condense the H2O vapor created by the fuel cell to provide water for the electrolysis. You will need energy input to separate the gases, perhaps from pumping through a diaphragm, and then storing and releasing each gas into the fuel cell, the fuel cell will be less than 100% efficient, and you will have to pump cooling water or run a fan for your condenser. To get 100 % condensation is not possible, you will have to add some make-up water. There are probably some uses for heat from the fuel cell and condenser in wintertime. E.g., one method to separate H2 from O2 is to pass the H2 through a heated palladium membrane.

If you burn the H2-O2 mixture in an engine that powers a generator, your efficiency will be even less, due to greater heat loss in creating mechanical energy and then the loss in converting mechanical energy to electricity. In this case, efficiency may only be about 40%. Again, there are opportunities for waste heat recovery, e.g., via distillation, but this can only raise efficiency part way, never to 100%.

Summary. If you create electricity by some means, say solar cell, you are best off using that electricity directly. The electrolysis could be used as part of an energy storge scheme by separating and compressing the gases into cylinders, but the energy output will always be less than the input. This might be OK given solar cells and lots of free sunlight, though.
Good luck, I hope I shed some light w/o being too discouraging.

 

[kenvlach]

James,
Another factor about the electrolysis of water:
you require water of good conductivity, condensate (i.e., distilled water) won't work.

A 25% solution of NaOH (or sulfuric acid) was used for commercial electrolysis. I can't find anybody doing this on a large scale, H2 is produced more cheaply by the petroleum industry, and O2 is produced more cheaply by air liquidation.

 

[JamesSmith]

Regarding electrolysis of water and your message...

What I am specifically interested in doing, is to use the electrolysis to produce the gases, use the gases to heat a steam generator of some sort, then use the electricity from that generator to then power the electrolysis.
1. Nothing perpetual, not an enclosed system, water would have to be continually added.
2. Using the water as a type of 'fuel', I want the process to otherwise be self-sufficient, and to tap off just a little of the gas, heat, water, etc.
3. Efficiency is not a concern.

I just want to keep the process going on its own, without adding anything but more water.
-Will this work???
I have read that it requires a great deal of power for electrolysis and that any potential power generated by such a process would be far short of what would be required to simply keep the electrolysis going.

What can you tell me along these lines?
Thank you in advance for any help you can give, I eagerly await your reply.
James

 

[RichLeimbach]

James,
The problem with this idea is that the liquid water is at it's lowest energy state as it enters the system. By adding liquid water into your system, you have not really added any extra energy to your system.
The liquid water is by itself incapable of producing the energy necessary to split itself into hydrogen and oxygen gases. If it did, water would spontaneously separate all the time and swimming would become a real problem.
It needs to have energy added into it (separating the gases) before it can do any useful work. Since the efficiency is necessarily less than 100%, you would have to add an outside energy source (solar, steam, electrical, water wheel, etc.) for this to work.

 

[JamesSmith]

Thank you for your help.
You mentioned that I would have to use an outside power source, and mentioned solar and wind power, etc, which seem to be fairly low-output power generators.

Does this mean that it really does not require much energy to produce a usable amount of gases from electrolysis?

Is there some simple way to express the efficiency/lack thereof, or the outside energy required to produce a certain amount of gases?
Like, say, so many watts could produce so many cubic feet of gases over such amount of time?
(I am not well versed in algebra or other mathematics, my talents are diverse, but mathmatics has always been my handicap)

If only a relatively small amount of energy is required to produce enough constant gas output to keep a 'burner' of some kind going, then my problem might be solved.

Thank you again for your help.
James

 

[IRstuff]

To some degree, this is a losing proposition. The energy you are looking for from the gases is the energy released when they enter an exothermic reaction and bond together, To get this energy, you need to put that same amount into the electrolysis. However, since the previous postings indicate that you need a conductive water, you'll be dumping electrical energy into simply heating the water.

Therefore, you will use much more energy getting the gases than you would from the gases themselves.

If there are other considerations other that energy gain, it might be worth doing, otherwise, you're btter off using the electricity directly. TTFN

 

[JamesSmith]

There are two basic goals involved in this:
1.
To make as much use, and as much inter-realated or cross-connected uses of already present resources.
2.
To expand on any potential resources and the diversity thereof. (Related to 1. above)

If I have a worthwhile continuing water-electrolysis process, then I will have the benefit of oxigen for an aquatic part of the overall project, and hydrogen for various uses including heat, etc.
-For instance... If it were legal foe me to use a "still", I would be able to use material for that still to and from compost resources as "stillage"; The still would also produce water vapor and C02 which could benefit plantlife, as well as the heat used for the still being beneficial to a greenhouse - thus, the still would be worth whatever extra resources it required, for the diverse benefits it produced primarily ( Distilled water and alchohol for fuel) and secondarily (Water vapor, C02, Heat, etc.)

What I am trying to determine in this subject is whether the electrolysis process is generally worth it's own existence and the resources required to keep it going.
Specifically: The hardware accomodations are no problem, aquiring the water is no problem, and there would be some primary and secondary benefits as well.
However, Just how much electricity would I have to devote to the electolysis to produce those benefits?
-That is what in the end would determine it's worth, I guess.

Two peticular considerations:
1.
I would likely use epsom salts to make the water more conductive, or in any case, something other than Sulfuric acid, something generally non-toxic.
2.
The real key to the whole project is that there will be diverse inter-related and cross-related primary and secondary resources feeding diverse processes; there will be different sources of recycled water, biomass, biogas, heat, C02, oxigen, etc. -The system as a whole begins to benefit itself; one resource feeds more than one process, one process yields more than one resource.
I have a hunch that certain things - like the electrolysis process may become easier due to the inter-related diverse resources and processes of the system as a whole...
That one thing will supply 'some' thing needed by another thing.
Solar, wind, and other power sources may well be employed, but may not be dependable, according to weather, regional climate, location and conditions in general, etc.

I am just having trouble getting my head around this electolysis part of the whole picture as far as just how much (power) I have to put into it to make it funtion as part of the system as a whole.
I am sure that you can understand that the project as a whole is both complicated and yet simple at the same time, which I have no problem grasping, so my real problem is a lack of familiarity with this one peice of the puzzle.

I need to get an idea of how much practical electricity is required to produce a certain amount of gases, to make it as short as possible - (despite the length of this reply)

Thanks again, and I still hope to figure this one out.

 

[GregLocock]

Fundamentally this idea is flawed because on balance in the real world you will lose energy by electrolyising water and then burning the results, instead of just using the electricity directly.

As to "I need to get an idea of how much practical electricity is required to produce a certain amount of gases"

The answer is that for each hydrogen atom you need to supply one electron. In one amp for one second there are 6.6*10^18 electrons.

2 kg of hydrogen contains 6*10^26 pairs of hydrogen atoms.

The voltage required to do this will depend on details of catalysts, electrode materials and impurities, to say the least.

If you were to optimise your process then the energy required would equal the calorific value of the hydrogen produced, 142000 kJ/kg. 2 kg of hydrogen has a volume of 22.6 cubic metres roughly at atmospheric temperature and pressure.





Cheers

Greg Locock

 

[mattnz]

James,
I wonder at the design concept behind your biosphere project. Now, I know nothing about biosphere technology and what is achievable so take what I say with a grain of salt.

It has been mentioned in previous posts that there are fundamental flaws in the proposed use of an electrolyising system. I agree. I have limited knowledge with adapting biological systems to mechanical solutions and I think a biosphere has to be approached from the same angle.

To my knowledge, the fundamental concept of a biosphere is to create an enclosed environment for human habitation.
Obviously thermodynamics limits the design of a totally self-contained biosphere to little more than a long term liferaft as eventually whatever high energy source you start from will become lower and lower energy sources until it is irretrievable. To create a long-term sustainable biosphere is, in effect, to create a living organism.

To get to the point, a living organism uses high energy sources (on Earth this is primarily solar) to extract necessary materials from the surroundings; whatever cannot be readily used is excreted. The organism uses single purpose devices to gain a high efficiency. For example, the lungs are devoted to breathing, they do not also try to extract energy from the surroundings (not entirely true, they do serve as limited heat exchangers).

I think that a design that utilises high inter-related or cross-connected devices will not be sustainable in the long run, simply because it is not done in the natural world. I know that this raises the example of the food chain, but the food chain is not an energy chain. At the beginning there is always an organism that gets its primary energy from the sun.

Cheers

Matt

P.S. Wasn't the biosphere idea tried before, without success?

 

[GregLocock]

I disagree Matt. Solar energy can be used to run a boisphere, but it takes a large surface area to do so, and it would be wise to use the energy efficiently. If push comes to shove you can halve the transmission efficiency and double the area, if you can afford to.

Biosphere2 did fail, but on the other hand if we are ever going to get off this planet for good we are going to have to figure out why it failed and get it right. People are working on this. Cheers

Greg Locock

 

[mattnz]

Greg,
I definitely agree with the importance of such work. Maybe my point was lost. I don't discount the possibility of a biosphere working and think that solar energy is the only viable energy source (or perhaps geothermal, but is a biosphere over a geothermal vent still a biosphere?). I was thinking that natural systems seem to have specialised organisms rather than multi-purpose and that the energy chain is rather direct (sun - grass - cow - human). There is obviously complexity in natural systems but this complexity seems to be in the control of the system rather than in the energy process. My main wonder was whether other biosphere projects have failed due to an over-emphasis on complicated energy transfer processes.

Matt

 

[JamesSmith]

Well...
Thank you everyone, as this is a lively subject at this point.
Since we have both specified and diversified on the subject of Bioshperes at the same time, I would like to address specific points of interest.

-By the way, being that I am not even a failing novice in physics or mathmatics, although I do very much appreciate the information and formula provided by 'GregLocock '- (Thanks, 'GregLocock '), as I mentioned before, I have trouble bending my mind around such things. So tell me, If I use 20 amps, 12 volts (from a car battery), improve the water conductivity with epsom salts, and use fairly efficient electrodes, how much gas(es) would be produced per minute or hour?

-Now on to Biospheres...
I m not actually trying to create a completely closed and self-sufficient system, but what amounts to being cclose to that by making the best use of all available resources in what I guess I would have to call "Cross-recycling" - as I mentioned, each process producing more than one resource, and each resource feeding more than one process, leaving nothing to waste, being essentially a "super-greenhouse"

There have been very simple and easy, completely closed and self-contained biospheres of an aquatic nature where just the right balance and choice of plant and animal life create a near-perfect cycle in something as small as what amounts to a large goldfish bowl, some of which have remained functioning and healthy for up to 5 years and more, by this date, probably much longer.
THe funny thing is that Aquatic environments seem to be much more efficient and cooperative than others.

A biosphere is, in fact, a little like an 'organism', but is very different in a way that helps my project.
No organism is a closed, self-sufficient being. They all require input of resource of some sort, and output of waste of some sort.
My project is "superior?" in the one respect that there is no waste, but it still needs input of resource of some sort.
Sunlight is free, "life" is essentially free once started, and the flora and fauna in turn produce various resources that are then reused.
In this "partially closed" system, all I really need is water - at least in warmer climates, but in the colder parts of the country, warmth is also needed when the sunlight is dim or temperatures become critically low.
Efficiency is a small concern, as it must be assumed that resources of some sort are necessary; but the trick is in keeeping the needed resources to a minimum through the efforts of "cross recycling" (mentioned above)

Solar energy is definitely an option, as well as other potential 'cheap' resources, but what I have to determine is if a 'small' solar set-up or other'cheap' option will supply enough energy to make the water electrolysis function just efficiently enough to justify its existence in the process - if so, I gain diverse resources, and at least one resource that was not present before, which adds opportunities and potential to the whole process.

As I mentioned earlier, 'GregLocock' gave me a clue as to how to figure out the energy needed to produce a certain amount of gases... I will re-insert that information and a sample specification here in the hope that someone can help me to understand it better or cheat for me and do the calculation that escapes me...

"...for each hydrogen atom you need to supply one electron. In one amp for one second there are 6.6*10^18 electrons.
2 kg of hydrogen contains 6*10^26 pairs of hydrogen atoms.
The voltage required to do this will depend on details of catalysts, electrode materials and impurities, to say the least.
If you were to optimise your process then the energy required would equal the calorific value of the hydrogen produced, 142000 kJ/kg. 2 kg of hydrogen has a volume of 22.6 cubic metres roughly at atmospheric temperature and pressure."
"If I use 20 amps, 12 volts (from a car battery), improve the water conductivity with epsom salts, and use fairly efficient electrodes, how much gas(es) would be produced per minute or hour?"

-Help?

 

[kenvlach]

James,
I hoped to give you some firm numbers re electrolysis, but can’t locate my energy handbook book after several moves. However, I can tell you that by burning the H₂ in an engine driving a generator, your electricity produced will only be 1/3 of that used in hydrolysis. You can double that efficiency using a fuel cell, but that requires quite a bit of technological know-how. You could also improve the overall efficiency using the waste heat from the engine, e.g., if you put a turbocharger type device on the exhaust to drive another generator. But, as greggnz warned, the failure rate goes up as the complexity increases.

You really need a handbook on alternative energy. A lot of research was spurred by the energy crises in the 1970’s. I suggest you seach for ‘alternative energy,’ ‘energy handbook,’ etc. at

http://www.addall.com/Used/

e.g., some search results:
Alternative Energy Handbook. (1979).
by Rodale Editors.

ALTERNATIVE ENERGY HANDBOOK (1993)
ROSENBERG PAUL

Energy Handbook (1978)
Author: Robert L. Loftness

A Design and Construction Handbook for Energy-Saving Houses (1980)
Wade, Alex

 

[kenvlach]

James,
I found a plating chart that shows Hydrogen is generated at the rate of 0.0373 gram/ampere-hour, and Oxygen is generated at the rate 0.2984 gram/ampere-hour, assuming 100% electrode efficiency. The 1:8 ratio corresponds to the H₂:O weights of water. I.e., H₂O will be electrolytically decomposed at the rate of (0.0373 + 0.2984) = 0.3357 grams/ampere-hour.

http://www.finishing.com/GIFS/crib.GIF

Now, for voltage needed. A table of 'The Standard emf Series' shows
O₂ + 4H⁺ + 4 e^- = 2 H₂O at +1.229 Volts, and
2H⁺ + 2 e^- = H₂ at 0.000 Volts. Subtracting 2x the 2nd rzn. from the first gives
O₂ + 2H₂ = 2 H₂O at +1.229 Volts
However, due to polarization at the electrodes, to get the reaction to go at a reasonable rate requires an overvoltage. In this case, figure an extra 0.5 V at each electrode, for a total driving voltage of -2.229 Volts.

Now for an overall rate of 1000g H₂O decomposed per hour, the current required is 1000/0.3359 = 2977 amp-hours. At 2.229 Volts, the power consumed is 6636 volt-amp-hr = 6.636 Kwatt-hr, or $0.796 worth of electricity at $0.12/Kwatt-hr.

Hope this is useful.

 

[GregLocock]

Great stuff. 1 kg of water will electrolyse to give 111 g of H2. This has a calorific value of 142 MJ/kg, so in an 80% efficient fuel cell it will generate 0.111*.8*142*10^6/3600/1000 kWh

3.5 kWh

So you are putting in 6.6 kWh of electricity to generate 3.5 kWh of electricity (ie 53% efficient). Not, in most circumstances, a great idea. Cheers

Greg Locock

 

[JamesSmith]

Only 53% efficient at best?
-That means the process may only lose 47% energy/resource!
Compared with the efficiency rates of various fuels, this might not be too bad.
The 53% efficiency /47% loss is what would have to be justified by the overall benefits of it being part of a system. (or the cost of building and running it.)
This would probably be better than the efficiency of a still, or other processes involved.

This has been very helpful, and I thank everyone for thier help and all the information which I am condensing and adding to a general document on this subject.
I will have to do some conversions, as most of the information has been submitted in metric standards, so I am crossing my fingers that I will do so accurately.

One thing I forgot to mention on the subject of biospheres:
The (Failed) Biosphere project was named "Bioshpere II", The Earth being the assumed Biosphere #1.
Since the Earth itself has been functioning for at least several years now, and can be assumed to be somewhat successful, I think the difference betwen it and Biosphere II is size, diversity/complexity, and cooperation of it's various processes.
A "direct chain" will often lead to a dead end eventually;
Therefore diversity of inter-related and cross-connected entities or processes is absolutely neccessary, and otherwise "natural".

The issue of the Second Law of Thermodynamics has been refered to...
According to this principle, the Earth itelf is not actually working, but using itself up and will eventually die.
Thus, resource is needed to keep anything running, and the reason for the Earth apparently working is that it has a lot of material, and an indirect outside source of power in our Sun.

One arguement popular with those who do not belive in "perpetual energy" or possibly perpetual motion also, is that "there is no such thing as a free lunch".
Both sides are wrong.
On one hand, as long as the sun shines, the evaporative and precipitaion processes work, the water flows, or the wind blows, there IS such thing as a free lunch - (in fact, in this example a potential of between two and four types of free lunches, and possibly other potential examples as well).
On the other hand, If someone were to succeed in manufacturing a perpetual energy device, eventually it would need some sort of maintenance or servicing; and eventually replaement as well, thus, a truely perpetual energy device cannot exist.
Even the Sun will someday burn out.

The point?:
"Is something worth it's own existence?"
My goal is not to have a big hernmetically-sealed terrarium
that produces forever without maintenance or added resource.
The goal egan as a large greenhouse, which inevitably lead to composting, recycling, and efficient use of materials;
which in turn leads to more and more of the same.
In the end, the final hoped-for result is a 'pseudo-biosphere that still needs input and maintenance, but the only real input/resource/fuel being sunshine and water.
Most life functions by using these two resources.
In fact, a direct chain can be traced like so:
Rock/dust/mineral - moss/lichen - plant/animal.
All that is needed for the chain to work is an environment that includes water and sunshine.
(-and atmosphereic pressure, procetion form harmful cosmic rays, etc.)

I know for a fact that this general project can and will work - I just have to find a few of the right peices from Earth's puzzle that will cooperate together...
-and then cheat!
Because in order to make a true biosphere, it would require such diversity, and so many organisms and processes, that you would have to essentially create another Earth, so shortcuts and 'cheating' are necessarily required.

I would still like to get input on this subject, as another good resource is diversity -of information..........

 

[JamesSmith]

I would like to formally apologise for my sloppy and mis-spelled writing in this forum, as I can do better, but like most people, am in too much of a hurry to do it right.
-I am not as hasty and sloppy in my projects.
Thank you, I will now punish myself somehow, after procrastinating....

 

[GregLocock]

If you want to read some interesting thoughts on why B2 'failed', and more generally the difficulties in establishing complex ecologies, then read "Out of Control" by Kevin Kelly.

I agree, the Earth is not a closed system, we get energy from the sun and that's what ultimately powers the whole thing (and a bit of a contribution from geothermal, and a bit from us).
Cheers

Greg Locock

 

[kenvlach]

Please see developments in
'Photoelectrolysis of water is the answer.'
thread804-60148