hydrogen from solar

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smarsman's picture
smarsman
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hydrogen from solar

Chris,
Why can't hydrogen be generated from solar and/or wind? With such high net energy gains, it would seem that it is quite feasible.
Thanks

cmartenson's picture
cmartenson
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  Phredd nailed

 

Phredd nailed it.

 

  1. First you must hydrolyze water.  This is 70% efficient.
  2. Hydrogen gas is the most voluminous gas of them all.  Unless we each want a dirigible in our yard it must be compressed.  10,000 psi would give us a decently small tank.  This costs us another 15% in compression efficiency losses.
  3. Unless we use it very rapidly, hydrogen boils off and escapes costing us ~3%-4% per day.
  4. Then we burn hydrogen in a fuel cell at roughly 50% efficiency.

Final take = 0.70  * 0.85 * 0.96 (per day) * 0.50  = 28.5% of the original energy is available for work.

In short, at present hydrogen is a very inefficient battery.  Perhaps this can be improved, but that's how the technology stacks up at present as I understand it.

Chris Martenson, PhD.

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Reuben Bailey
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efficiencies
I agree that the electrical efficiency of hydrogen is only about 25% from the numbers that I have heard. The way that I could see hydrogen being useful is if you have a use for the waste heat generated by both splitting the water and burning the hydrogen. It also has some "economy" of scale - it becomes more cost effective to store a 10 day electricity supply in hydrogen than in batteries. Another potential benefit of it is pure oxygen (medical grade) given off during the splitting of water. I realize that these may not be practical in many situations, and that is part of what we need to be thinking about - there will be many different solutions that make sense in different situations, rather than one single solution that fits everywhere.

I think that not counting transmission costs is fooling ourselves - I have heard everything from 15% loss to as much as 65-70% loss if you count all energy used to build and maintain the transmission infrastructure - potentially not much better than hydrogen.

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phredd
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Well, yes and no

I agree with you that there is no "one size fits all" solution, and hydrolysis may someday play a role. I'm certainly glad to see research in that area, and if efficiencies improve, there may well be uses. But it is very unlikely to ever become as efficient as the direct use of the generated electricty. A couple of issues:

"[I]t becomes more cost effective to store a 10 day electricity supply in hydrogen than in batteries." As a blanket statement this isn't true. The answer depends on duration and scale. If you plan to keep this 10-day supply around for more than a short period, batteries are generally better. The escape rate of hydrogen from tanks generally exceeds the self-discharge rate of most large-scale batteries. On the other hand, batteries don't scale well past a certain point. If you are planning to store electricity on a truly massive scale (think city size here), then batteries become cumbersome.

"I think that not counting transmission costs is fooling ourselves - I have heard everything from 15% loss to as much as 65-70% loss if you count all energy used to build and maintain the transmission infrastructure - potentially not much better than hydrogen." Remember, I discounted BOTH the transmission costs of electricity AND the transportation costs for hydrogen. I do that for simplicity, and it is fair to ask about them. But be sure you compare apples to apples. The 65%-70% figure you hear counts the costs for manufacturing tension poles, transformers, wires, junction boxes, and other hardware, in addition to actual transmission losses (which really are about 15% on average). If you are going to use that 65%-70% figure, then be sure you compare it to the manufacturing costs of hydrogen storage tanks, the costs of manufacturing the tank trucks (including a portion of the infrastructure costs for the road network) (or pipelines, if you can justify the risks of an extremely high-pressure line) and the fuels to run them, the costs of the water purification systems, and so on, in addition to the hydrogen collection and compression systems. The problem rapidly gets very complex, but most analysts still conclude that the total conversion costs for electricity still compare extrememly favorably to those for hydrogen. And that may be understating it a bit.

Reuben Bailey's picture
Reuben Bailey
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yes and no again
phredd,

I agree that hydrogen is not a good medium for transporting power any significant distance. I was comparing centralized generation and long distance transmission with point of use generation and on-site storage. My reason for doing so is that I see our current paradigm of large scale, centralized power generation as being one that needs to change because of the inefficiency of sending electricity long distances, including building and maintaining the power lines.

At this point I do not have any hard sources for the numbers that I am using, so I can't back these up. The ten day supply figure came from someone who was talking about setting up a backup system for an off-grid house or farm. His comment was that the small scale setup using compressed hydrogen (not liquefied) was more easily/economically scalable than batteries in this situation (change the size of the tank to change the length of time). The length of storage time is basically from when the last excess power is generated by solar or wind units until the last of the hydrogen is used. He may be completely off base, I don't know.

One question for you: For your average of 15% transmission loss, what are the starting and ending points for that? Is it from end to end of the high tension line or is it from generator to point of use?

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phredd
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Electric Transmission

Reubenmp3-

I am using a "hybrid" figure for transmission losses, based on the reading I have done, and would be a pessimistic guess of the average losses from generator to user. The figure-of-merit most often cited on the web for total distibution losses is from a 2003 study (here in PDF format) which lists transmission and distribution losses at 7.2% for the average line loss in the U.S. I have seen utility company papers which estimate regional losses in the 5% range. However, I have also heard people complain that those figures are understated for various perceived reasons. (Transmission losses vary by the distance from the source, and some argue that average distance from generator to user has increased over time.) I have seen figures from non-U.S. companies which cite a 12% loss figure as accurate but unacceptably high. This is just from generator to home.

There will be additional losses in an average home due to the relatively low voltages and relatively thin wires used on that scale; however, the distances are also quite short. Those losses account for the the increase from the 10% range to the 15% range, although actual losses are likely to be a bit less on average (losses in the 2% range are typical, but these losses are multiplicative with the transmission losses cited earlier). I think 15% loss for total transmission and distribution losses from generator to user is actually quite pessimistic.

I think your friend is generally incorrect about the convenience of hydrogen storage on the scale of a home or farm. It is not hard to find a 60kWh storage system (which runs about $15,000 at today's prices, and would have a typical use of 10 years or more). And frankly, a 10-day capacity will exceed most users' actual needs. The self-discharge rate on these batteries will be about 5%/month. (Research is still ongoing for hydrogen storage. The loss rates are improving.)

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phredd
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"High net energy gains?" I
"High net energy gains?" I don't think you understand the problem. Hydrogen can be split using electricity generated by solar panels or wind turbines. The question is: Why would you do that? Coverting electricity to hydrogen via electrolysis of water and then combusting the hydrogen is perhaps 30% efficient (optimistically) end-to-end, and that isn't counting any cost for transporting the hydrogen to where you need it. If you simply collect the electrical energy in a battery or transmit it through the existing grid system and then use it to run an electric motor, your resulting efficiency is 70%-80%, not counting transmission costs (which will be much less than hydrogen transportation costs). By using hydrogen as an intermediary you are essentially just throwing away more than half of your production. I don't think that sounds like such a good idea in a world that will shortly find itself starved for cheap energy.
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gyrogearloose
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Close
If the hydrogen is compressed there is no day to day losses unless you have bad fittings ;-) If you liquefy it, then you face the boil off losses for the time you are not consuming it as fast as the boil off rate. So for your final total efficiency you use either 2 or 3, not both. Either way, hydrogen is still a BAD idea Hamish
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srbarbour
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Hydrogen
[quote]First you must hydrolyze water. This is 70% efficient.[/quote] Closer to 75% actually. Though I'd point out that most good electrolyzes use platinum. There has been innovation on platinum issue though. [quote]Hydrogen gas is the most voluminous gas of them all. Unless we each want a dirigible in our yard it must be compressed. 10,000 psi would give us a decently small tank. This costs us another 15% in compression efficiency losses.[/quote] You can use the compression energy of the hydrogen as a power source, so calling it a 15% loss is probably a bit unreasonable. Also, other storage mechanisms have widly varying storage losses, so using this as an example distorts a very complex problem. [quote] Unless we use it very rapidly, hydrogen boils off and escapes costing us ~3%-4% per day. [/quote] What crappy storage tank/storage mechanism was used to conjure these numbers? Sounds exceedingly bogus or old. There are plenty of ways to store hydrogen where losses are much, much less. Near zero actually. [quote]Then we burn hydrogen in a fuel cell at roughly 50% efficiency.[/quote] If used now, we'd certainly be burning it in a Internal Combustion Engine: 12-25%.

Fuel cells range wildly in their conversion efficiency anywhere from 30-90% efficiency ratings. However, almost all fuel cells use platinum and only a few can reasonably be used in vehicles. Again, there has been innovation in all the related areas. [quote]Final take = 0.70 * 0.85 * 0.96 (per day) * 0.50 = 28.5% of the original energy is available for work. In short, at present hydrogen is a very inefficient battery. Perhaps this can be improved, but that's how the technology stacks up at present as I understand it. [/quote] If deployed right now, probably closer to 75% * 20% * 50-90% (Total transport loss is probably ~10-60%+) = ~6% - 13%. Losses could be much lower if used in a power generator -- say to store solar energy and release it at night -- 75% * 50% (engines which burn for efficiency == much better) * 90% (Short term storage cost) which could be as high as 33% give or take as much as 10%.

Obviously, Hydrogen without good energy converter and without eliminating platinum as much as possible isn't going to be practical. It would require a massive investment in increasing electrical energy. How much, it is hard to say. Most lists of 'energy' used by our fuels directly list the energy of the root oil, or ignore the large transport and conversion losses of gasoline. Which is rather like back tracing the energy consumption of your refrigerator to the energy content of raw coal before it is burnt.

If we can get a good fuel cell with little or no platinum use, and which is suitable for running a vehicle (most fuel cells arent). Then the viability of Hydrogen increases significantly.

Long story short. Cellulosic Ethanol is probably our best interim solution. Until then, we have to wait for the electric industry to switch to more expansionary technologies (fast breeder reactors/solar power) and for a 'better battery'. Be it improvements in hydrogen, capacitors, etc... I will say though that current batteries will never be good enough and have no real potential for improvement. The jump to Lithium was the last revolutionary step for battery technology, and there isn't enough lithium in the world to power all our cars.

Don't get my wrong. We can go hydrogen if we really wanted to. Its just that at this point it is still better to wait as long as possible until the necessary technologies mature and improve ...

... short of an onset of peak oil, that is.

--

Steve
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LeaderofMen
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NH3
I'm not a math expert and thus haven't run the numbers for this but why not use ammonia to store H2? I'm not sure of the energy tax to split it but once that's done, you get N2 + H2, which is potential energy + fertilizer. Seems to me that since ammonia is such a huge industrial chemical currently in use that this would be a reasonable way to transport it to energy storage facilities. I'm guessing this is off the table because of the energy tax burden.
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Nichoman
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Expansion of Role Alternative Energies

Chris...

 

Read your bio and seems we have somewhat similar backgrounds...mine is atmospheric physics...thermodynamics...E-M in multiple leading edge projects in late 1980's into mid 1990's.  You've spent a tremendous amount of time on developing a thorough...outstanding presentation.  Alternative Energies...I find...is your one area still incomplete.

Solar...Wind...also Geothermal...Ocean...Batteries among others need more addressing.  Suggest researching how long and how quickly they can supplant portions of transportation and other applications.   Offer my view is were still 5+ years away before they can make significant inroads...my research suggests by 2020...options for electrification of most transportation can also be quite powerful.  They can aid in upgrading electrical grid...plus potentially other areas.   If so...this tends to alter options and consequences to world economy starting within 10 years.  May be aware of numerous studies showing electric propulsion is roughly 2 times more efficient than ICE (Internal Combustion Engine) which is also important.

Suggest this is a critical point to the basis of your excellent presentation that thus needs further expansion.  Your efforts are greatly appreciated by myself and family.  I have researched energy heavily for well over 5 years...and share many of your concerns and points.   I may be a bit more optimistic regarding alternative energy options helping us and other areas of science and technology to at least a modest degree beyond 5 years.   Again, this is where suggest considering doing possibly a complete section.   Your probably aware there is tremendous amount of information out there...it's like your other subjects you've done quite well with...parsing it.

Key point I tend to agree with you on is the next 5 years...alternative energies without major advances will have negligible impacts to the energy problem. 

 

Warm Regards,

--Bill Nichols

 

 

 

 

 

 

 

 

gregroberts's picture
gregroberts
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Re: hydrogen from solar

Hydrogen Solar home, does not look cheap though...

http://www.youtube.com/watch?v=xEdQRVQtffw

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angelsmile
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Re: hydrogen from solar

Since we are experiencing economy crisis right now, we ought to find ways on how to lessen our daily expenses. We all prioritize expenses at home and it's really amazing to have this solar energy for our homes. It is great to save money from our electricity bills.

The sun is a gift from God, that we really need. It is indeed amazing that we can make use of it's heat. To have energy for our homes and appliances and of course, to save! Solar energy panels really helped many people. It is very useful and reasonable in saving money. It is all natural and a green nature friendly.

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SPAM_angelina
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Re: hydrogen from solar
  1. First you must hydrolyze water.  This is 70% efficient.
  2. Hydrogen gas is the most voluminous gas of them all.  Unless we each want a dirigible in our yard it must be compressed.  10,000 psi would give us a decently small tank.  This costs us another 15% in compression efficiency losses.
  3. Unless we use it very rapidly, hydrogen boils off and escapes costing us ~3%-4% per day.
  4. Then we burn hydrogen in a fuel cell at roughly 50% efficiency.

[utl=http://www.sterling-energy.com]Technical Consulting Services[/url]

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