Savannah River National Lab sucessfully completes test of new electrolyzer
Researchers at the Savannah River National Laboratory have completed their first long duration of a new hybrid sulfur process electrolyzer. The process works in two main stages with the first taking sulfuric acid and decomposing it into oxygen and sulfur dioxide in the presence of heat from a nuclear reactor.The other stage puts the sulfur dioxide and water into the electrolyzer to produce hydrogen and sulfuric acid. The presence of the sulfur dioxide reduces the voltage required across the electrodes to 0.8V per cell although the researchers are confident they can further reduce that to 0.6V. That brings the overall efficiency of the process to over fifty percent. SRNL is currently working on a larger multi-cell due to be completed next year. Longer term, SRNL is working on an integrated system that incorporates both stages of the hybrid sulfur process at the DOE's next generation nuclear plant in Idaho.
[Source: Department of Energy]
Reader Comments (Page 1 of 1)
BJD 5:12PM (7/15/2007)
I still don't understand it. Electrolysis is only 50% efficient, and it takes another chemical process at another certain efficiency to convert the resulting hydrogen back into water to produce electricity (presumably for use in a transportation vehicle). The use of electricity directly from the source to power an electric vehicle is somewhere in the high 90's in terms of efficiency. Why are we still looking into hydrogen fuel cells based on electrolosis?
there are more efficiency losses.
. That's to take water to hydrogen. Then the hydrogen is used in a fuel cell at another efficiency rate
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David Schmetterer 7:20AM (7/16/2007)
BJD - I for one hear you loud and clear, but the thinking *must* be that they are hoping to make it more and more efficient, but the process happens in tiny steps.
And at the same time, lots of batteries and charging systems are being worked on as well by other people in other places, but those have their drawbacks as well.
It is a long race, I just hope *someone* finishes in time.
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Sam Abuelsamid 7:38PM (7/15/2007)
The problem is not the efficiency of the electricity to torque process. Battery powered cars do not take electricity from the source unless you drive around with an extension cord connected to your car. The problem is the limited ability of chemical batteries to store energy and release it when needed. The rate at which energy can be put into a battery is slow (aside from the Altairnano batteries) and the total capacity for a given weight is also low. There are also transmission losses from the power plant to your home.
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Mike Z 7:42PM (7/15/2007)
People just think that hydrogen is going to cars. But Hydrogen might make a big difference in boosting the yields of biofuels and increasing the yield on oil refining. Also LH2 for possible in air travel.
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James 9:26PM (7/15/2007)
One could note, too, that this technology would enable a nuclear plant to supplement renewable generation by operating the hydrogen production at variable current. Peaks and valleys in grid supply and demand can be smoothed out as renewables come on and offline, with the resulting energy stored as hydrogen for transportation or industrial use. Compare the efficiency of this to the exactly zero efficiency of overproduction waste on the grid, which is what we have today.
One could argue that several millions of PHEV batteries attached to smart chargers distributed throughout the grid would accomplish the same thing, but that might be a lot more difficult to achieve in practice, but definitely worth study.
The heat source for this process could be solar thermal as well. Other DOE researchers as well as some private companies are working on this.
There was a good write-up and some lively discussion on this subject a couple weeks ago on greencarcongress.com.
http://www.greencarcongress.com/2007/07/srnl-hits-miles.html
James
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A.Brien 9:29PM (7/15/2007)
As hydrogen is difficult to transport it should be fabricated as needed on place by electrolysis from water onboard the car or near the house if needed as household gas. I found a compagny that has this product. WWW.itm-power.com
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Chris M 10:31PM (7/15/2007)
Is it just me, or is the idea of using corrosive sulfuric acid in a nuclear reactor to produce explosive H2 gas as foolhardhy as it sounds?
Another puzzler is why bother with this more expensive and hazardous process, when conventional electrolysis can achieve a slightly higher efficiencies? Maybe it has to do with using more heat energy directly from the reactor and less electrical energy. Maybe it has to do with promoting nuclear power.
Of course, even with nuclear furnaces going full blast, H2 will still be a bulky expensive fuel, not really suitable for automotive use.
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Mike Z 10:52PM (7/15/2007)
This method is far more efficient, because it will not require a second steam line and does not waste the energy to generate electricity. The process appears to be more efficient at generating hydrogen from nuclear than nuclear is at generating electricity.
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BJD 12:53AM (7/16/2007)
Sam,
Thanks for your comments. They are very insightful. I already know about Altair's batteries and their superior capability of storing more energy and rapid charges. On the issue of transmission losses...the losses wouldn't be so great if more people were generating their own power via solar panels. In the case though of the nuclear power plant, I see your point. It would be nice to see someone actually conduct a study of the cradle to grave efficiencies (and maybe costs) of the following scenarios:
1. nuclear/electrolysis/distribution/hydrogen fuel cell/electric motor
2. Nuclear/transmission lines/Li-Ion battery/electric motor.
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James 1:40AM (7/16/2007)
The beauty of this system is that you still generate electricity with better efficiency than modern nuclear plants, but you get hydrogen on top of it. The net system efficiency is much higher than if it did simply one or the other.
The peak heat drives the thermochemical hydrogen generation and the waste heat drives the electrical generation (it might be the other way around depending on what the feasible temp of the reactor turns out to be, but the end result is still much better...). Same amount of nuclear input fuel, much more useful product.
This way you can provide energy for Chris M's EV and my FCV at the same time.
Thanks,
James
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Tim 10:18AM (7/16/2007)
There is no way the H2 can be a distributed power carrier with efficiency anywhere near electricity. Are there uses for it, YES... in space and for certain industrial processes like producing biofuels. Will there ever be a "Hydrogen Economy", NO... because the "Electron Economy" can use existing infrastructure and can also be easily distributed and even produced on our roofs at 4X the efficiency of hydrogen. Simple physics show us that the “Hydrogen Economy” is fools gold.
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OhmExcited 10:25AM (7/16/2007)
Hydrogen makes perfect sense for more practical e-flex type of electrically driven vehicles. Buses, trucks and semis can't run on batteries alone. Hydrogen can be produced in areas where there is no grid to take it to large population centers. For example, most wind resources are offshore or in the upper Dakota plains. Most cheap real estate with lots of sun is not surrounded by large population. These are currently untapped resources. Finally, hydrogen is a better alternative for local air quality compared to diesel and gasoline hybrids.
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Chris M 11:52PM (7/16/2007)
BJD: Here is a rough comparative calculation of efficiency.
1) Nuclear H2 generation 50%, Transport 90%, Compression 80%, Fuel cell 50%, Controller and motor 90%, overall efficiency 16.2%
2) Nuclear electricity generation 35%, Transmission 90%, Charger and Battery 85%, Controller and motor 90%, overall efficiency 24.1%
I generously assumed an efficient H2 transport via a relatively short pipeline, if transported by truck the efficiency plummets.
I don't have all the information to do a cost calculation, but an automotive fuel cell cost much more than a EV battery pack. Then add in the cost of the high pressure H2 tank, and it is abundantly clear which costs more. Much more.
Operating costs would tend to reflect overall efficiency, and again, H2 fuel will cost more.
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James 1:06AM (7/17/2007)
Chris M,
You left a couple things out in your efficiency chains:
1) You also have to DISCHARGE the EV battery. 90%. Grid transport is probably a bit higher than 90% for electricity, but splitting hairs.
2) Fuel cell efficiency closer to 65%. Ancilliary systems 90%. (Honda is claiming 60% tank to wheels, although that seems high. Who knows, they've surprised us before. Others in US DOE Hydrogen Program show FC system between 52% and 58%.) Transport loss 90% seems high, but I'll give it to you.
Tally here:
EV: 22%
FCV: 19%
Not as dramatic as your previous calculation, or Tim's 4x efficiency difference.
Plus with FCV you get the grid storage, renewable enabling peak load adaptability for the grid, don't have to carry around 450kg battery, >250mile range, 5 minute recharge whenever you want...
In reality these technologies go hand-in-hand. The H2 fuel cell is the most efficient range extender for EV, if you want to think about it like that.
Thanks,
James
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Chris M 3:21AM (7/17/2007)
James: The 85% figure for charger and battery includes charging AND discharging. Grid is typically 94% to 98% efficient, but I didn't want to appear biased against H2. (90% efficiency = 10% loss) I used the standard PEM fuel cell efficiency of 50%, as that is the most common figure quoted, even by H2 proponents. There are other types of fuel cells with higher efficiency but for various reasons are not considered suitable for automotive use. For example, alkaline fuel cells can hit 80% efficiency, but reqire pure H2 and pure O2.
H2 fuel cells could be used as an EV range extender, and that is the direction both Ford and GM are taking for their H2FC program. "Electric fuel" is simply cheaper than H2, and always will be, so why not use it when you can?
Aside from H2 and petrol and diesel, other possible EV range extenders include refillable zinc-air or aluminum-air fuel cells, or even powered guideways for power "on the go".
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