Electrolyzing water for energy storage.
Electrolyzing water for energy storage.
(OP)
No, this is not for over-unity crazies. 
In the wind power thread this came up thanks to marks1080. I didn't want to hijack that thread further so here we are.
Always seemed to me that electrolyzing water could be very efficient if you avoid heating the water. I would think the efficiency would be much better than any battery chemistry out there. Of course you have to herd it somewhere and compress it which brings ineffiecency to the party.
Then, if, you have to burn it in an IC engine, you toss %50 away immediately.
Can anyone describe an actual running system?

In the wind power thread this came up thanks to marks1080. I didn't want to hijack that thread further so here we are.
Always seemed to me that electrolyzing water could be very efficient if you avoid heating the water. I would think the efficiency would be much better than any battery chemistry out there. Of course you have to herd it somewhere and compress it which brings ineffiecency to the party.
Then, if, you have to burn it in an IC engine, you toss %50 away immediately.
Can anyone describe an actual running system?
Keith Cress
kcress - http://www.flaminsystems.com






RE: Electrolyzing water for energy storage.
RE: Electrolyzing water for energy storage.
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I suspect finding schematics for the system would be hard, but I do have some old friends that work with NL Hydro, and some contacts at the University. I will see if I can't get in touch with them to see if they know more.
RE: Electrolyzing water for energy storage.
Or is just because you have it a real good reason?
Do you really save money when you buy something you can't use, even if it's on sale?
RE: Electrolyzing water for energy storage.
RE: Electrolyzing water for energy storage.
The problem is someone wants to be paid for that free energy.
If the factor is a green thing, then why can't nucular be used to provide energy to produce hydrogen?
It's not that I don't like wind power, it is simply not a good mix with most other existing generation and load profiles. Part of the reason is simply we sleep at night, and the other is the cost.
RE: Electrolyzing water for energy storage.
This is not really my area of expertise, but I have done quite of bit of reading in this over the years, and did cover this area in a college course in the 1970s.
My understanding is that electrolysis of water itself is generally only about 50% efficient at temperatures near ambient. That is, you need about 2 units of electrical energy to produce hydrogen containing 1 unit of enrgy.
I have read that the efficiency goes up substantially at higher temperatures, so if you have a "free" source of heat, you could do significantly better. It would seem that producing this next to a nuclear power plant at night, with "free" waste heat, and almost free electricity (if the alternative would be reducing the power outputs of the plant) would provide the cheapest production. Of course, then you would need a new storage and transmission infrastructure.
Then, in burning the hydrogen in an internal combustion engine, you will probably not get better than a 25% efficiency, for a total efficiency of 12.5%. Burning the hydrogen in a combined-cycle turbine could achieve 50% efficiency, for overall 25%, with similar numbers for fuel cells.
By contrast, lithium-ion batteries have charge/discharge efficiencies above 90%, so on this count, batteries appear to me to be far ahead. And, they work off an existing infrastructure.
Curt Wilson
Delta Tau Data Systems
RE: Electrolyzing water for energy storage.
If you have excess power you must generate, you need a storage solution. Charging batteries can be that. Pumped storage can be that. Hydrogen can be that.
As for nukes why do you think they built Helms Reservoir?? It's because nukes need to run full out 24/7. They need storage to be economically better utilized.
We are not debating the need for storage I'm just trying to learn about an alternative method.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Electrolyzing water for energy storage.
cswilson; Sorry for the delay - we cross posted. Thanks for that summary. I didn't realize Li-Ion were that much better than lead acid batteries (~60%) or that the quantum efficiency of electrolysing water was that poor. That's pretty bad. :(
I also didn't realize that heating the water would help the bond breaking that much. Thanks.
I don't recall the efficiency for H-O fueled fuel cells maybe that would be better than an IC.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Electrolyzing water for energy storage.
The best PEM fuel cells are about 60% efficient.
Alan
----
"It's always fun to do the impossible." - Walt Disney
RE: Electrolyzing water for energy storage.
This is the real question. And let me say this energy isen't free. The wind tower owners do expect to be paid for that energy.
So if we use the 50% number each mega Joul of hydrogen energy will cost at least 3 cents, then there is a profit margin, storage cost, insurance, taxes, water fees, water treatment, sales cost.
Granted you could possibility make additional cash selling the oxygen.
Probally an electric car would be a better alternitive.
RE: Electrolyzing water for energy storage.
alehman; Thanks.
I'm seeing 50~80% in some literature. There are also many different methods, electrolytes, and electrodes. It appears more complex than I initially thought, energy-conversion wise.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Electrolyzing water for energy storage.
the point of this thread is to let people know there are other storage mediums out there for wind power. We can all agree most wind potential is during periods of low demand. SO... instead of turning off the wind turbines when the wind is blowing and the demand is NOT there we are simply discussing a method of storing the power so it can be used when the demand comes back.
i admit i have not done any calculations on this, but even a 50% efficiency rate on the hydrogen production and a 50% efficiency rate on the burning of that hydrogen seems like it could be well worth the extra infrastructure over the moderate to long term. When you consider the fact that the energy used to create it would never of been utilized in the first place your 'profit' margins are very wide.
Does anyone know the going rate for Hydrogen? I expect the demand for hydrogen to increase quite a lot over the next few years... would anyone here know if you could make more money selling the hydrogen gas than burning it? would the money made from selling the hydrogen offset the cost of purchasing power from a neighboring utility? There are dozens of scenarios one could get into on this. Lets not forget the initial pilot project i mentioned earlier was specific to an isoloated community which would normally burn diesel for power.
RE: Electrolyzing water for energy storage.
It becomes worse when you start with a higher cost energy to start with.
Maybe there are times when the differential is worth it, but would it not be better to give real time pricing to the consumers and let them do the energy storage?
I hear Ice storage works somewhat well for reducing summer cooling loads. And if the night time electric costs were that much lower than more costumers might consiter it.
The best part is we can do this today, not some time in the future.
RE: Electrolyzing water for energy storage.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Electrolyzing water for energy storage.
RE: Electrolyzing water for energy storage.
In the USA northwest, wind is backed up by hydro. If the wind blows when demand is low, more water is held back in the reservoirs. Energy storage with no energy utilization (free?). I know, fish protection, reservoir capacity, and irrigation complicate things from my simplified description.
RE: Electrolyzing water for energy storage.
But what we are seeing is a requirment that we accept more and more wind into places that have a difficulty in accepting it. And the customers are being told they will pay to fix this unbalance.
10% name plate is probally a good number that most utilites can handle. Above that there can be dificulty with the changes in the wind speed.
RE: Electrolyzing water for energy storage.
The 'best' storage schemes, from the grid's point of view, would be implemented at the wind farms. That way their smoothing effect would present the grid with a stable power source over time periods that operations can deal with.