INEEL High-Temperature Electrolysis Demo Produces Hydrogen for Record 1,000 Hours
06 March 2006
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| View of the edge of one high-temperature electrolysis cell while operating at 830º C (1,525º F). The arch-like openings carry air and the oxygen produced for the electrolysis. Source: INEEL |
Researchers at DOE’s Idaho National Engineering and Environmental Laboratory (INEEL) ran a high-temperature electrolysis stack to produce hydrogen for 1,000 hours in the longest and largest experiment to date on processes that could lead to the production of hydrogen using nuclear energy.
The stack, operating at 830º C (1,525º F), produced 177 normal liters of hydrogen each hour, or 4.248 normal cubic meters in a 24-hour period—an amount (0.36 kg) equivalent to about half of a driver’s average daily gasoline usage.
INEEL has previously estimated that a single next-generation nuclear plant will be able to produce in hydrogen the energy equivalent of 200,000 gallons of gasoline each day. The US consumes about 9 million barrels of gasoline per day, or 378 million gallons.
Conventional electrolysis splits water into its components—hydrogen and oxygen—by charging water with an electrical current. The charge breaks the chemical bond between the hydrogen and oxygen and splits apart the atomic components.
The resulting ions form at two poles: the anode, which is positively charged, and the cathode, which is negatively charged. Hydrogen ions gather at the cathode and react with it to form hydrogen gas, which is then collected. Oxygen goes through a similar process at the anode.
The main drawbacks of conventional electrolysis for large-scale hydrogen production are the amount of electricity required for the process and the high cost of membrane production. It takes about 142 MJ to produce 1 kilogram of hydrogen—about 40-50 kWh of electricity per kilogram of hydrogen.
High-temperature electrolysis (HTE) adds in some of the energy needed to split the water as heat—from a source such as high-temperature steam from an advanced nuclear reactor system or an adapted solar energy system—instead of electricity. Because the conversion efficiency of heat to electricity is low compared to using the heat directly, HTE reduces the overall energy required.
HTE uses a device very similar to an Solid Oxide Fuel Cell (SOFC). Essentially, the electrolytic cell consists of a solid oxide electrolyte with conducting electrodes deposited on either side of the electrolyte. A high-temperature mixture of steam and hydrogen is supplied to the anode side of the electrolyte.
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| Click to enlarge. |
Oxygen ions are drawn through the electrolyte by the electrical potential and combine to O2 on the cathode side. The steam-hydrogen mixture exits and the water and hydrogen gas mixture is passed through a separator to separate hydrogen.
Such a high-temperature system has the potential to achieve overall conversion efficiencies in the 45% to 50% range, compared to approximately 30% for conventional electrolysis. Added benefits include the avoidance of both greenhouse gas emissions and fossil fuel consumption.
We’ve shown that hydrogen can be produced at temperatures and pressures suitable for a Generation IV reactor. The simple and modular approach we’ve taken with our research partners produces either hydrogen or electricity, and most notable of all—achieves the highest-known production rate of hydrogen by high-temperature electrolysis.
—Steve Herring, lead INEEL researcher
This demonstration is seen as a necessary first step toward large-scale production of hydrogen from water rather than fossil fuels.
INEEL has been working with Ceramatec, a private-sector company, on the project for several years.
We’re pleased that the technology created over the nearly two decades dedicated to high-temperature fuel cell research at Ceramatec is directly applicable to hydrogen production by steam electrolysis.
In fact, both fuel cell and hydrogen generation functionality can be embodied in a single device capable of seamless transition between the two modes. These years of investment, both public and private, in high temperature fuel cell research have enabled the Ceramatec-INEEL team to move quickly and achieve this important milestone toward establishing hydrogen as a part of our national energy strategy.
—Ashok Joshi, Ph.D., Ceramatec CEO
Secretary of Energy Spencer Abraham recently announced a grant of nearly $2 million to a Ceramatec-led effort teaming with the INEEL, the University of Washington and Hoeganaes Corp. to continue work in the broad area of high-temperature electrolysis and fuel cell development.
Resources:
“Milestone for H2 Production by High-Temperature Electrolysis” (earlier post)
Mmm, OK. So that means that it would take about 2000 reactors to supply the U.S. with the energy equivalent of the gasoline that we use today. Ignoring all of the other problems with this, doesn't the sheer number of these things required make this a deal-killer?
Posted by: Eric | 06 March 2006 at 10:15 AM
When we think of global warming, we generally think of greenhouse gas emissions. But what would all this generated heat do to our waterways and the planet as a whole? Or would the heat generated be counterbalanced by the heat not generated by the replaced gasoline.
Posted by: t | 06 March 2006 at 10:28 AM
The heat issue is not in any way a problem. Seriously, especially if you put the nuclear plants on the sea coast.
Anyways, I don't see this as any kind of credible solution. You could do it incredibly more cheaply with ordinary nuclear reactors (or whatever) and electric cars.
Converting all oil-propelled vehicles (cars, trucks, trains, ships etc) in the US to electric drive would require about 250 new 1000 MW reactors.
Building the power plants will cost $500 billion dollars and take 10-20 years from the day the plant licenses are granted, but building the plants is not the big issue, it could be done without too much trouble (but state intervention would obviously be needed if you want to speed up the construction).
The big issue is building those 200+ million cars, trucks etc, considering there are presently 0 mass produced EV's for sale...
Posted by: Starvid | 06 March 2006 at 10:39 AM
The back-of-the-envelope calcuation that 2000 nuclear reactors would be needed to replace our entire gasoline useage scared me at first too, like is scared Eric.
However, I don't think that it would be accurate to say that we would need actually to build that many reactors to hypothetically replace all of our gasoline with hydrogen. The reason is that hydrogen fuel-cell cars would make far more efficient use of the energy contained in the hydrogen than current cars make of the energy stored in gasoline. We would not need to replace every BTU of gasoline with an equivalent amount of hydrogen energy, because to drive the same number of miles (perhaps even in equally large cars) we would consume less hydrogen energy, but do so more efficiently.
According to some numbers I cribbed off howstuffworks.com, a fuel cell powering an electric motor in a car should see an overall conversion efficiency of around 64%. Typical gasoline engines are said to clock in at around 20%. Therefore, on a per-unit energy basis, we would need to replace our daily consumption of gasoline with a daily consumption of an amount of hydrogen which contains 3.125x less energy, because our powertrains would be working 3.125x more efficiently. We would therefore only need around 625 new reactors. That is still a somewhat large number; according to the Nuclear Energy Institute, the United States has 103 civilian reactors currently on line. Long term, many people speak of generating hydrogen from renewable sources (wind, solar, etc.). This solution eliminates a good deal of the scariness.
The heat pollution question also struck me as interesting. By currently burning so much gasoline we are dumping a lot of waste heat into the environment. Though hydrogen is more efficient within the car engine itself, and therefore would lead to less waste heat being dumped off each individual radiator, I don't think we (ordinary civilians) know enough about the hydrogen generation process to evaluate the heat balance on that end. I don't know, off hand, how much total heat the nuclear pile in question would throw off, or how efficiently that heat would be turned into chemical energy stored in the hydrogen, versus what would be discharged as waste heat. One problem with locating nuclear reactors far away from urban areas (for obvious safety reasons) is that it makes it impractical to use the waste heat for heating buildings and other ancillary purposes.
Another waste heat problem is that waste heat is currently generated and discharged in a fairly dispersed fashion -- each car discharges a little bit of waste heat directly into the atmosphere wherever it happens to be. Nuclear reactors, by contrast are point sources of fairly large and intense discharges of waste heat. This can have unfortunate local consequences, such as when a stream or a local body of water is overheated by reactor waste heat, significantly affecting the local ecology. Locating reactors by the sea coast would allow us to take advantage of a very large pool of very cold water that exists at the ocean depths, but aside from the unknown environmental consequences that might accrue from warming up the bathypelagic depths, finding thinly-populated oceanfront property on which to build these reactors would be quite a challenge, as our coastlines have become hugely popular residential zones over the years.
Posted by: NBK-Boston | 06 March 2006 at 11:18 AM
Also keep in mind that the solar concentrating dish technology that Stirling Energy is developing to produce up to 1.75GW of solar electricity in the next few years, could also work quite well as a hybrid thermal electrolytic hydrogen generator.
Mass production of the dishes will bring down the cost of the tracking dishes, enabling lots of different things to be put at the focal point beyond just Stirling Engines.
Posted by: DishBoy | 06 March 2006 at 11:43 AM
You can see a presentation offering similar results using concentrating solar power done by NREL here:
http://www.eere.energy.gov/solar/pdfs/mcconnell.pdf
Point being all you need is heat and electricity, nuclear need not be part of the equation.
Posted by: NREL_LaidOff_Employee | 06 March 2006 at 11:51 AM
Some nice efficiently generated solar thermal electroytic hydrogen sure would go nice with this:
http://world.honda.com/news/2006/4060108FCX/
Honda says they will have a production version out before 2010.
Posted by: FCX4Me | 06 March 2006 at 12:05 PM
First, a disclosure: I'm from Austria, the only country ever to have built a complete nuclear power plant (at Zwentendorf) that was never switched on because of public protests.
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The arguments being advanced in favor of hydrogen fuel cells for cars are: zero tailpipe emissions, zero teilpipe greenhouse gases, reduced dependence on oil from unfriendly countries and, storing energy from renewable sources.
If emissions are the problem we're trying to solve, carmakers can install a fan + burner or battery + electric heating element for the three-way catalyst already required for every new gasoline-powered vehicle. Pre-heat the cat for 10 (summer) to 20 (winter) seconds and then engage the starter motor. This will go a long way toward earning PZEV ratings in California, which count toward the ZEV quota of currently 10%. However, by law, carmakers selling more than 60,000 vehicles per year in that state still have to achieve a minimum sales target of 2% true EV or FC vehicles, if need be well below cost.
If greenhouse gases and/or dependence on oil from unfriendly countries are the problem, tighten up CAFE and sharply increase the net cost of driving a gas guzzler. Invest in cellulose ethanol and biogas technology. Import biodiesel feedstocks from friendly tropical countries. Improve the energy efficiency of new real estate developments with small-scale heat-cold-power co-generation based on clean engines and absorption chillers.
If storing energy from renewable sources (solar, wind, waves or tides) is the problem, use any transient electricity surplus to pump water back upstream into the reservoirs of already existing hydroelectric dams.
Perhaps the biggest problem of all is the DOE playing hide the salami. Half a century into the nuclear age, it still has no operational long-term storage facility for highly radioactive nuclear waste, neither at Yucca Mountain nor anywhere else. Nor does anyone else (France, China, India, ...) Waste stored on-site at existing nuclear power plants is subject to a determined terrorist attack. And if the US insists on expanding its reliance on nuclear power, containing rogue states with hidden agendas (Iran?) will prove nigh-on impossible.
Ergo: nuclear power is a bad idea. The hydrogen economy is a bad idea. Combining the two is a really bad idea. I much prefer the DOEs advocacy of diesel as a motor fuel.
Posted by: Rafael Seidl | 06 March 2006 at 12:28 PM
The article above highlights powerfully the one largest drawback of the hydrogen economy: it takes an absolutely huge amount of energy to produce the hydogen gas in the first place, before it can power anything. Sure hydrogen burns clean, etc, etc. No one would argue that. That shouldn't be the point.
When it takes many many times more energy to make a thousand units of hydrogen energy than the equivalent units of energy from any other fuel source, whatever it may be, the advantage is all gone. We're talking huge conversion losses here. Hydrogen can never be cleaner in the end. You have to burn tons and tons of conventional fuels to get your hydrogen for your hydrogen car, so where are the environmental benefit in the end? You're worse off than better, you're just never told this. The only way that the hydrogen economy can ever be feasible/cleaner in the end is if it is all somehow produced from green energy sources, but it still won't be efficient. This huge political push for hydrogen makes no sense. Electricity makes waaaay more sense.
Posted by: John W. | 06 March 2006 at 02:20 PM
John W.
I have yet to see a complete life cycle analysis comparing hydrogen vs. electricity. My guess is that electricity makes more sense, but this is more intuitive than based upon a rigorous analysis. I can see certain possible applications for hydrogen. For example, it is might be a good way to fully utilize wind energy when it can't be fed into the grid. On the other hand, advanced batteries or pumped storage might be as good or better.
In any event, it is clear that reformation of fossil fuels like natural gas is a dead end if one's goal is efficient energy use and reduced greenhouse emissions. Otherwise, it is just a way perpetuate the use of fossil fuels while doing nothing to combat global warming or wean us from fossil fuels.
The problem is that we don't seem to have a clear set of goals that holistically compare the different technologies. It just seems like DOE is throwing everything in the mix to satisfy different political interests. With this scattershot approach, we will never get anywhere, and people will still be debating this 20 years from now. By that time, we will be way beyond screwed.
Posted by: t | 06 March 2006 at 03:59 PM
Newer turbine designs can use more of the heat and turn it into energy with secondary heat to energy recovery. Its not been done before because energy was so cheap when most of the nuke plants here were built. If people were not so crazy about the nuke issue the waste heat could be used to heat houses or factories in the winter. Stirling engines could recover much of the waste heat unused or dumped now.
You would be surprised how much heat is thrown off by cars, if you measured it I am sure it would be a few hundred times would reactors put out now.
Posted by: Hampden Wireless | 06 March 2006 at 05:21 PM
19 months ago I calculated that all US motor fuel could be replaced with about 180 GW of electricity. Average US electric consumption is about 450 GW, of which ~20% is produced by ~100 nuclear plants. Looks like a mere 200 more plants would suffice to replace motor fuel if we drove transport directly via wires or using high-efficiency batteries like Li-ion.
Posted by: Engineer-Poet | 06 March 2006 at 09:10 PM
I have been doing a little more research on the conversion efficiency question that I raised before, a question which also seems to bug John W. in his post, where he decides that hydrogen is totally infeasable because "it takes an absolutely huge amount of energy to produce the hydrogen gas in the first place... When it takes many many times more energy to make a thousand units of hydrogen energy than the equivalent units of energy from any other fuel source, whatever it may be, the advantage is all gone." I think John's concerns are largely misplaced, and state my reasoning below.
According to the DoE, conventional nuclear reactors have a thermal efficiency of about 33%; that is for every 10,623 BTU of heat thrown off the nulcear pile, 1 kWh of electricity (3,412 BTU) comes out the back end of the plant. The rest gets discharged as waste heat, or could be used in a co-generation scheme of the sort noted above. See reference #1.
Furthermore, the conversion efficiency of a conventional hydrogen-gas production plant using existing electrolysis technologies is about 85%+. That is, for every 142 megajoules of electricity pushed into the electrolysis unit, one kilogram of hydrogen gas comes out, which contains about 120+ MJ of chemical energy. See references 2 and 3.
Combining the two cycles gives an overall thermal efficiency of about 28%, starting with uranium pellets and ending with H2 gas. Combining this number with the drivetrain efficiency of a fuel-cell attached to an electric motor (see my earlier post) gives a near-total lifecycle efficiency of about 17.8%. This is the total thermal efficiency, from uranium pellets all the way to drive shaft, but excludes the costs of mining the uranium and the proportionate share of construction costs (in dollars or BTU's... take your pick) of the reactor and associated capital equipment. Considering a gasoline engine only gets 20% thermal efficiency from tank to drive shaft, we're already pretty close. And I'm going out on a limb here, but I'm willing to guess that pumping, transporting and refining petroleum -- all of which are not figured into the 20% efficiency figure -- add a lot more energy expenditure than the neglected elements of the nuclear fuel cycle examined above. From a purely thermodynamic point of view, hydrogen already makes at least as much sense as gasoline, if not more. And it clearly makes more greenhouse-gas sense.
If I understand the original article correctly, though, the researchers quoted there are really claiming that a 50% conversion efficiency, from reactor heat to hydrogen gas energy content, is possible. (I did not understand the exact meaning of their claim the first time around.) That would yield a near-total lifecycle efficiency of 32%, which would be a huge thermodynamic gain on gasoline or other similar liquid fuels. Serious co-generation of building heat could make the theromodynamic efficiency across the whole economy even higher.
Hydrogen is also carbon-neutral, highly portable, quicker and easier to refuel than most batteries, potentially much lighter to carry than batteries for a given amount of stored energy, and potentially less dirty to produce than a huge number of batteries, each possibly containing rare-earth or heavy metals, and hydrogen is usable in combusion and turbine applications as well as in fuel cells. These are several reasons why hydrogen might be preferred on a long-term basis. On the flip side, the nuclear waste produced by 625 new reactors burning full at steam would certainly be a sight to see, and quite potentially a total deal-killer, at least until hydrogen made from green electricity or yet another source become a real possibility.
After looking all this up, I've come to realize that hydrogen really does have great theoretical promise, and that John W.'s concerns over hydrogen's fundamental efficiency seem largely misplaced. The problem is that the technical barriers to implementation seem to be very high. Generating hydrogen, storing it, and burning it in fuel cells still requires unreasonably expensive equipment, and still faces many practical hurdles; storing hydrogen safely in and efficiently in car-sized portions is a big one. Replacing our entire vehicle fleet would also be an enormous hurdle, and could only take place gradually.
For that reason, I think that hybrid drivetrains, renewable fuels (ethanol/biodiesel), battery technology, and strong fuel-efficiency-promoting regulatory measures (taxes on gas and gas guzzlers, CAFE with teeth, etc.) are fundamentally necessary for the critical 20-30 year horizon ahead of us. Beyond that horizon, I think hydrogen could easily take over as a long-term energy medium. As a young man, I hope to live through that horizon and beyond, in a clean, safe and sustainable world. Our government's neglect of these near-term options is well known and impossible to excuse.
References:
1. http://eia.doe.gov/cneaf/nuclear/page/uran_enrich_fuel/convert.html (efficiency of conventional nuclear reactors)
2. http://www.ne.doe.gov/hydrogen/HTE.pdf (efficiency of electrolysis)
3. http://www.hyweb.de/Knowledge/w-i-energiew-eng2.html (energy density of hydrogen)
Posted by: NBK-Boston | 06 March 2006 at 10:35 PM
P.S. ...
Regarding Engineer-Poet's calculation: Even if we ignored transmission losses over the grid, which have been calculated at anything from 1.5% to 7.5% of total transmitted energy (see Refs. 1 and 2), there still is the question of conversion from electricity to mechanical energy.
The figure of 180 GW actually represents the total engine shaft output of all vehicles together. At a conversion efficiency of 80% (Ref. 3), you would actually need 225 GW of current electricity, after transmission losses, to generate 180 GW of shaft output. That's at least 250 present-day nuclear reactors.
I don't know why the article states that yearly output from a single reactor would be the hydrogen equivalent of 200,000 gallons of gasoline. Perhaps they are just using unusually small reactors.
References:
1. http://www.dti.gov.uk/energy/consultations/elec_market.pdf
2. http://en.wikipedia.org/wiki/Electric_power_transmission
3. http://science.howstuffworks.com/fuel-cell4.htm
Posted by: NBK-Boston | 06 March 2006 at 11:11 PM
About the waste heat from a 1000 MWe nuclear plant: at 2000 MWt, it's equivalent to the 24-hour average of sunlight falling on an area of eight square km--a bit less than three square miles. If the plant were built underground and serviced an urban area for a radius of four miles (area of ~40 square miles), it would raise average ground temperature in its service area by just a couple of degrees C--assuming a reasonable density of trees and greenery to help dissipate the heat through transpiration. Basically, trees would serve as the nuclear plant's cooling towers. A network of underground tunnels would be needed to distribute the waste heat over the area, but they would double for distribution of power and utilities.
In any case, the heat load from a nuclear power plant is drastically less than that from a gas or coal-fired power plant. The big heat contribution is not in the waste heat from the plant itself; it's in the retained solar energy that the released CO2 from a fuel-burning plant is responsible for over the CO2's lifetime in the atmosphere.
High temperature electrolysis is not just significant for making hydrogen from nuclear electricity, however. It can be used to make hydrogen more efficiently from wind and solar electricity as well. Just put a bunch of electrolysis cells in a very well-insulated box; any waste heat from the cells just raises the temperature inside the box until the contribution of thermal energy to hydrogen production exactly balances the electrical losses. The result is 100% net conversion efficiency from electrical energy to hydrogen.
That's not a *huge* boost from the 80% typical for conventional electrolysis, but it's enough to be helpful. Especially if high temperature ceramic cells become cheaper and/or more durable than the PEM cells currently favored.
Posted by: Roger Arnold | 07 March 2006 at 01:13 AM
Look at the big picture not just the numbers (smart life planning).
You can produce energy in many ways that have no nuclear waste,
wich will take a billion years to dissolve (smart waste).
You shouldnt have to commute far to work (smart development),
you should waste energy like empty SUVs or
I have even flown in an almost empty plane (smart transportatin).
Free natural energy such as wind combined with solar, Dams and on the coast ocean currants, also Bio Fuels (Smart energy).
We already have Nuclear waste that we cant deal with, we dont need any more.
It is just laziness that we use nuclear since its cheap and dangeruos for our future, 3 Mile Island, Chernoble, 911, Iran nuclear power- Bells Ringing in your head yet?
(Smart Safty)
Go Natural - Then the Earth will last longer. And I am not a Old Hippy (Just Smart).
Posted by: Nuclear Waste. Heard of it? | 08 March 2006 at 07:33 PM
Correct me if I am wrong. The new plants would make the equivalent of 200,000 gallons of gas per day. The article says US uses 9 million (barrels) a day of gas. 9 x 55 = 495 million gallons of gas per day. Now 495,000,000 gal. divided by 200,000 gal. = 2475 plants to sustain the gas usage. Are the numbers bad here or am I missing something?
Next question. Is that number inclusive of the diesel fuel we use? 495 million sounds like a lot but if you consider US population to be at the 300 million mark that comes to 1.65 gallons of gas per person. That sounds possible. So 2475 nuclear plants? No thanks!!
Correct me if I am wrong. The new plants would make the equivalent of 200,000 gallons of gas per day. The article says US uses 9 million (barrels) a day of gas. 9 x 55 = 495 million gallons of gas per day. Now 495,000,000 gal. divided by 200,000 gal. = 2475 plants to sustain the gas usage. Are the numbers bad here or am I missing something?
Next question. Is that number inclusive of the diesel fuel we use? 495 million sounds like a lot but if you consider US population to be at the 300 million mark that comes to 1.65 gallons of gas per person. That sounds possible. So 2475 nuclear plants? No thanks!!
Posted by: chuck | 27 July 2008 at 07:49 PM