First Analysis of the Water Requirements of a Hydrogen Economy

First Analysis of the Water Requirements of a Hydrogen Economy
This graph shows the annual water consumption as a feedstock and coolant for generating 60 billion kg of hydrogen, which is influenced by both the fraction of hydrogen that is produced by thermoelectrically powered electrolysis and electrolyzer efficiencies. Image credit: Michael E. Webber.

One of the touted benefits of the futuristic US hydrogen economy is that the hydrogen supply—in the form of water—is virtually limitless. This assumption is taken for granted so much that no major study has fully considered just how much water a sustainable hydrogen economy would need.

Michael Webber, Associate Director at the Center for International Energy and Environmental Policy at the University of Texas at Austin, has recently filled that gap by providing the first analysis of the total water requirements with recent data for a “transitional” hydrogen economy. While the hydrogen economy is expected to be in full swing around 2050 (according to a 2004 report by the National Research Council [NRC]), a transitional hydrogen economy would occur in about 30 years, in 2037.

At that time, the NRC predicts an annual production of 60 billion kg of hydrogen. Webber’s analysis estimates that this amount of hydrogen would use about 19-69 trillion gallons of water annually as a feedstock for electrolytic production and as a coolant for thermoelectric power. That’s 52-189 billion gallons per day, a 27-97% increase from the 195 billion gallons per day (72 trillion gallons annually) used today by the thermoelectric power sector to generate about 90% of the electricity in the US. During the past several decades, water withdrawal has remained stable, suggesting that this increase in water intensity could have unprecedented consequences on the natural resource and public policy.

“The greatest significance of this work is that, by shifting our fuels production onto the grid, we can have a very dramatic impact on water resources unless policy changes are implemented that require system-wide shifts to power plant cooling methods that are less water-intensive or to power sources that don’t require cooling,” Webber told “This analysis is not meant to say that hydrogen should not be pursued, just that if hydrogen production is pursued through thermoelectrically-powered electrolysis, the impacts on water are potentially quite severe.”

Webber’s estimate accounts for both the direct and indirect uses of water in a hydrogen economy. The direct use is water as a feedstock for hydrogen, where water undergoes a splitting process that separates hydrogen from oxygen. Production can be accomplished in several ways, such as steam methane reforming, nuclear thermochemical splitting, gasification of coal or biomass, and others. But one of the dominant production methods in the transitional stage, as predicted in a 2004 planning report from the Department of Energy (DOE), will likely be electrolysis.

Based on the atomic properties of water, 1 kg of hydrogen gas requires about 2.4 gallons of water as feedstock. In one year, 60 billion kilograms of hydrogen would require 143 billion gallons of fresh, distilled water. This number is similar to the amount of water required for refining an equivalent amount of petroleum (about 1-2.5 gallons of water per gallon of gasoline).

The biggest increase in water usage would come from indirect water requirements, specifically as a cooling fluid for the electricity needed to supply the energy that electrolysis requires. Since electrolysis is likely to use existing infrastructure, it would pull from the grid and therefore depend on thermoelectric processes.

At 100% efficiency, electrolysis would require close to 40 kWh per kilogram of hydrogen—a number derived from the higher heating value of hydrogen, a physical property. However, today’s systems have an efficiency of about 60-70%, with the DOE’s future target at 75%.

Depending on the fraction of hydrogen produced by electrolysis (Webber presents estimates for values from 35 to 85%), the amount of electricity required based on electrolysis efficiency of 75% would be between 1134 and 2754 billion kWh—and up to 3351 billion kWh for a lower electrolysis efficiency of 60%. For comparison, the current annual electricity generation in the US in 2005 was 4063 billion kWh.

In 2000, thermoelectric power generation required an average of 20.6 gallons of water per kWh, leading Webber to estimate that hydrogen production through electrolysis, at 75% efficiency, would require about 1100 gallons of cooling water per kilogram of hydrogen. That’s 66 trillion gallons per year just for cooling.

By 2050, the NRC report predicts that hydrogen demand could exceed 100 billion kg—nearly twice the 60 billion kg that Webber’s estimates are based on. By then, researchers may find better ways of producing hydrogen, with assistance from the DOE’s large-scale investments, which will exceed $900 million in 2008.

“That most of the water use is for cooling leaves hope that we can change the way power plants operate, which would significantly ease up the potential burden on water resources, or that we can find other means of power production at a large scale to satisfy the demands of electrolysis,” said Webber.

If electrolysis becomes a widespread method of hydrogen production, Webber suggests that researchers may want to look for an electricity-generating method other than thermoelectric processes to power electrolysis. With this perspective, he suggests hydrogen pathways such as wind or solar sources, as well as water-free cooling methods such as air cooling.

“Each of the energy choices we can make, in terms of fuels and technologies, has its own tradeoffs associated with it,” Webber said. “Hydrogen, just like ethanol, wind, solar, or other alternative choices, has many merits, but also has some important impacts to keep in mind, as this paper tries to suggest. I would encourage the continuation of research into hydrogen production as part of a comprehensive basket of approaches that are considered for managing the transition into the green energy era. But, because of some of the unexpected impacts—for example on water resources—it seems premature to determine that hydrogen is the answer we should pursue at the exclusion of other options.”

More information can be found at the Webber Energy Group, an organization which seeks to bridge the divide between policymakers and engineers & scientists for issues related to energy and the environment.

Citation: Webber, Michael E. “The water intensity of the transitional hydrogen economy.” Environmental Research Letters, 2 (2007) 034007 (7pp).

Copyright 2007
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Oct 18, 2007
I don't understand why the water used for cooling is not directly recyclable. That is 100% water in, 100% water out. This does not seem like additional consumption. Please explain!

Oct 18, 2007
In some cases it is 100% in 100% out, not only that but most of the heat disbursed can be reused to sustain low thermal co-gen processes.
Not to mention that in many cases the actual use of hydrogen has the direct by product of creating pure water!

There is more hype in this work that fact.

Oct 18, 2007
I guess they dont read the news.

Atlanta and others facing drought and great lakes dropping due to ethanol production.

I think there are some serious issues with hydrogen and ethanol.

Ever hear of wind, solar, and wave generators ?

I guess not, or it must not be backed by the big rubber and big oil.

Oct 18, 2007
Hello anyone? Does anyone else realize that if you only have 75% efficiency in the power system that enables electrolosys, then you are automaticly wasting 1/4 of the energy you produce before it is ever used? Just to use the allegedly "clean" hydrogen...Then of course, when you use a fuel cell or burn it in a combustion engine you end up with an additional huge amount of waste heat and other forms of waste just like regular automobiles anyway.

I personally believe, based on elementary chemistry and physics, that the "carbon economy" will be a disaster which produces more air and water pollution than oil ever has.

Oct 18, 2007
No matter what form of energy we use. There will always be waste. No machine we will ever develop will be 100% efficient.

Using aluminum and gallium to take hydrogen directly from water would be great.

http://www.physor....html />

Oct 19, 2007
Using Aluminium or Gallium to produce electricity in a cell would be even more efficient, than making hydrogen and then oxidising that. You could fill up at a bowser with liquid gallium, and discharge your Gallium oxide waste powder for recycling. Aluminium would be much cheaper. No water is consumed in the process.

Oct 19, 2007
We should also think about the effect the extra water vapor has on the global warming situation as 36% of all green-house gasses are water vapor...

Oct 19, 2007
From what I remember from chemistry I always thought you needed salt water for electrolysis otherwise there can't be a current through water. So my question is, why not use seawater? This is in huge supply and after electrolysis and use you would be left with fresh water. Also why not use seawater for cooling? Why does it have to be fresh water?

Oct 19, 2007
As a chemical engineer who understands thermodynamics, it is clear that the amount of energy that can be obtained by burning hydrogen is equal to the energy required to electrolyze water. Due to inefficiencies in the electrolysis system (due to the Second Law of Thermodynamics), using hydrogen is a net energy-loser unless the electricity used for the electrolysis is obtained from a non-fossil-fuel source, of which nuclear power is the most plentiful.

Steam reforming of methane (to make CO2 and hydrogen) doesn't make sense energetically, since energy is used to boil the water to make steam, and more energy could be obtained by simply burning the methane. A "hydrogen economy" is only feasible if electricity for electrolysis is obtained from nuclear power plants, or eventually from hydroelectric power from dams.

If a water-electrolysis plant was built next to a nuclear power plant, some of the waste heat from the electrolysis could be recovered by using cooling water from the electrolysis plant as preheated boiler-feedwater for the steam boiler at the nuclear power plant, thereby increasing the amount of steam (and electricity) produced for the amount of nuclear fuel consumed.

Regarding "cybrbeast's" comment about using salt water for electrolysis, electrolysis of salt water produces chlorine gas, the process commonly used to manufacture bleach and caustic soda. However, if hydrogen is produced on a massive scale by electrolysis of salt water, the process will produce 35 times more mass of chlorine than hydrogen, and some means of capturing and neutralizing the toxic chlorine would need to be used. If the hydrogen was produced as a transport fuel on a large scale, the industrial market for chlorine could never absorb such a huge amount of free chlorine.

Salt water could eventually be used for cooling, but most engineers tend to avoid it, due to problems of fouling and corrosion of heat exchangers and cooling towers.

Oct 19, 2007
Personally, I consider the proposed hydrogen economy as yet another 'flying car' technology. It sounds really cool, and you just feel the need to say that you want it. But there are technical considerations that bring this off of it's pedestal.

I might be wrong, but I keep thinking that the amount of electrical power needed to generate enough hydrogen to move a fuel-cell car one mile, is greater than the amount of electrical power needed to move a plug-in battery-electric car the same distance. So to my mind, hydrogen is just an alternative solution to the problem of storing electric power. I don't feel right about shaping the public infrastructure around what might be just a band-aid fix for the short-comings of battery storage. I have more faith in future developments in battery technologies, which only require the purchase of 220 volt battery chargers to complete the delivery of energy to individuals.

And now I get to add in consideration, the amount of cooling water. Thanks!

ps - big fuel distributors are trying to break it slowly to the public that the ea-85 fuel is going to need more trips to the pump to drive the same miles every day. of course, the price per gallon is fixed...

Oct 20, 2007
The power for electrolysis will come from solar power and it will be almost naturally like producing energy from plant except that it will not require the growing of live plants.

Oct 20, 2007
Chem_eng, the amount of energy returned from burning hydrogen, isn't equal, it's less than the amount used to free the hydrogen. There is always energy loss in electrolysing the water or other hydrogen source.

Hydroelectric dams also produce a lot of co2 and methane. Not from the generators themselves, but because they cause the water level around the dam to raise and lower. Letting plants grow, then drowning and decomposing them. Leeching nutrients from the soil around the damn and turning it into gases. Tidal, wave and continuous flow systems don't cause this problem.

You are right about the Chlorine though. The other half of that problem is the sodium getting turned into Sodium Hydroxide (Lye). So on top of the chlorine gas, the lye would also need to be neutralized and removed. Although we can somewhat cheat with that (adding aluminum neutrlizes the lye and releases more h2) the problem then becomes, where do we get enuogh aluminum, since that takes even more power to create.

In the end, h2 is just too much of a PITA to deal with as an energy transport. A carbon neutral power plant batteries and maybe super capacitors is going to end up being the way to go. Batteries are where we really need to be putting some research. Mainly in getting the mass per kilowatt down.

Oct 20, 2007
Couldn't the sodium and chlorine that are released when electrolyzing salt water be recombined into into NaCl, salt?
I see a big future for nuclear and solar power, but I'm not a big fan of the hydrogen idea in general. There are already some electric cars that are practical for medium distance daily commuting. Like Shadetree said batteries are a much better option. They are also less dangerous than hydrogen tanks. I think the nanotech industry will be able to greatly increase the capacity of batteries, and decrease the charging time in the near future.

Oct 20, 2007
The Tesla Roadster battery electric vehicle will go four miles on the electrical energy it costs to make, move and transfer enough H2 to propel a fuel cell vehicle one mile.

Oct 20, 2007
The chlorine that comes from electrolyzing sea water would not stay around for very long. It would combine with the hydrogen that is still in the water, or the moisture in your lungs if you are unlucky enough, to make hydrochloric acid. It would be an immediate death to anyone who inhaled it.

Oct 21, 2007
I have always wondered what would happen to the tailpipe exhaust of hygrogen burning cars. Two problems come to mind.
1. Does the exhaust gas assume complete and perfect combustion producing only pure H2O vapor? If not, then what possible pollutants can come from an incomplete combustion? Bleach comes to mind.
2. What will happen to cities full of cars emitting water vapor into an atmosphere at 14F.
I fear it may be possible to ice skate from Montreal to Providence.
As said many times, "Hydrogen is the fuel of the future...and always will be".

Oct 22, 2007
How about first achieving a mass scale program for desalinating sea water (via solar or safe fusion power), and then figuring out how to electically hydrolicize or plasmatically dissassociate that fresh water secondly?

Oct 23, 2007
Has anyone looked at to assess their technology and feasibility for generating electricity from tidal power? Would this provide any relevant electricity for consideration?

Oct 25, 2007
1. I think a simple requirement to catch most or all water exhausted by use of the fuel cell and electrolyze it onboard would greatly reduce the amount of water consumed to make hydrogen. Some water would of course be lost during use in the vehicle, but it would be a relatively small amount. The electrolysis of recycled water could be made from regenerative energy produced when going downhill or coming to a stop, just as it is now in hybrids.
2. Electrolysing sea water is probably a last resort. Ideally, water should be purified or distilled to reduce any contamination of the fuel cell and environment and avoid productions of HCL.
3. Most hydrogen can be made from wind, sun and tidal action in areas of the world that possess these qualities in abundance. Nuclear can alos be used to both produce hydrogen and distill sea water. Shipping/transport of the hydrogen produced to areas not able to produce it can then be made in a similar way to how oil is now done (ie. ship/truck/pipeline). Cost of generating hydrogen in those areas will be free for operators once equipment is capitalized. Forget about the cost of producing hydrogen. It will be much less than producing oil once infrastructure is in place. Cost of transportation will be on the consumer, as it is now for petroleum.
Shadetree Engineer is quite right about ethanol. It's much less efficient as a fuel than gasoline, and it's causing tremendous increases in worldwide food prices.

Oct 26, 2007
All the assumptions about the "limitless" water resource implicitly means ocean water. It would be plain stupid to electrolyze drinkable water. For one thing, you have to add things such as plain old table salt to make it conduct electricity more efficiently.
Chlorine gas produced from electrolyzing sea water can be collected by well proven methods on industrial scales, as it has been for decades, as an valuable chemical. No industrialist will waste it, and by safety laws and regulations, you are not allow it goes free to choke/kill/poison the trees and people in the neighborhood anyway!
To be effective, the energy sources for electrolyzing obviously can't be oil. That leaves solar, nuclear, wind, geothermal and tidal power production. Solar-electric power is currently not favorable competitively due to high costs of semiconductor materials and production costs. Solar-thermal-electric approaches are limited by the scale and technology of mirrors/collectors, associated heat transfer loops and thermodynamics limits. Direct dissociation of water by extremely high temperatures produced by concentrating sunlight is constrained by the inefficiency of the process and thermal limits on materials. Nuclear power, while easily the most powerful and up scalable,is both politically and environmentally explosive. Natural wind, tidal and geothermal power are subjected to the vagaries of geography, not to mention the aesthetic impact on surrounding inhabitants, who are usually influential enough to derail any plans to have eyesore in their views, whether it is good for the planet or not.
So, all of them are compromises. We just have to accept and choose each for the available resources,location and (political) wind.
I envision a massive tank-like installation rigidly anchored off shore off the sea bed. The rise and fall of water would provide the water potential to drive electric generators, the strains on the anchors even be used for piezoelectric generation or a source of high oltage source for other uses. The massive surface area of the tank top will be used for solar power generation. By electrolyzing sea water, NaOH is produced. Its solution in sea water is denser than than water, so you can use that fact too. NaOH-rich water will sink, a reservoir of it with outlets will draw in sea water, generating extra power. Heck, if the tank is BIG enough and goes deep enough, the tank can be of two concentric layers, with the outer wall an osmotic membrane type, and fresh water is produced between the membrane by osmotic pressure for free!

All we need are pipelines...:-)

Dec 17, 2007
It seems that most criticisms of the Kanzius experiment point to the violation of the second law of thermodynamics. However, those with a background in chemistry can point to the role of catalysts in chemical reactions. Wikipedia has a good commentary on this, for those who would like to get a better understanding.

It appears that maybe the Kanzius RF experiment is taking advantage of the dynamics within a catalyzed reaction. The RF energy, at the 13.56 MHz frequency, is freeing the hydrogen from its bonds to oxygen. This is facilitated by the salt within the water. So the salt and the RF energy work in conjunction to allow less energy to create free hydrogen. One of the things about catalyzed reactions is that they are not well understood. That is because they operate within the dynamics of molecular physics. So, what the thermodynamic criticism fails to address is the fact that in catalyzed reactions the energy to put the atoms back together as a water molecule are also much less. This is impossible to prove for this particular reaction, but can be done so for other reactions, thus proving the hypothesis that the second law of thermodynamics is not violated in this instance either.

However, we don't care about putting the atoms back together in the presence of the catalyst(s) anyway. We care that we've reduced substantially the amount of energy required to break apart the bonds of the molecule.

Jan 05, 2008
I am not a scientist but I do have great interest in gaining further knowledge where possible. My way of contributing to a more prosperous and responsible ECO-nomy, is by passing on what I have found... here are two links.

One is for the world's first ever Hydrogen-Production-Storage-Transport Ships the Hydrogen Challenger

(a very clever idea for creating hydrogen via a renewable resource; especially interesting since the production and storage and transport of the hydrogen happens in the same place)

The second is an excellent interview/documentary with Hydrogen Energy Expert David Sanborn Scott on the wonderful CBC radio show Ideas.

part 1: http://podcast.cb...4089.mp3
part 2:

it's nice to see when an internet forum doesn't devolve into ridiculousness and name-calling...

i'll be checking in this site from time to time, thanks.

Jan 09, 2008
I thought the largest issue was extracting energy. Hydrogen is just another energy carrier. Batteries can be more efficient and the infrastructure is already here!

Mar 19, 2008
WRT the idea that 'you can't get as much out of the hydrogen as you need to make it'
1) we don't have to convert everything to hydrogen today. More efficient engine design (check out the Revetek engine) more efficient solar and wind (there's a lot just around the corner) more efficient electolysis (resonant frequencies, etc.);
2) use solar, the sun is free, panel's are getting more efficient every year anyway;
3) five years ago the GAO was estimating the actual cost of a gallon of gas between 5 and 7 dollars considering the efforts to secure oil in all the hotspots around the globe.

Recover the exhaust and "re-burn" it so the vapor doesn't contribute to global warming.

What's easier and less costly? To build an electric car using batteries or to convert a gasoline engine that already exists to use hydrogen to supplement the gasoline it's already using or switch all the way to hydrogen as needed? Gasoline engines can already burn hydrogen.

Yes there are tons of details, just like with oil. The economic growth opportunites are phenomenal. I suggest that not moving to hydrogen as at least a substantial part of the equation is folly.

What are the costs of not trying? Perhaps our favorite buddy Hugo Chavez has some ideas where we can spend our money!

May 10, 2008
We need alternative greener fuel especially for transportation. Fossil fuels will run out someday anyway and become extremely expensive well before that. Bio-fuel is not the answer, look at recent rises in food prices amd we need land to feed ever expanding populations. That leaves basically electrcity and Hydrogen which together could reduce our dependancy on fossil fuels. Electricity at the moment looks like it will have to be nuclear to produce the quantities needed and as for the production of Hydrogen we have virtually unlimited supplies of seawater and offshore windturbines to supply power all that is needed is the best way to use them. Alternatives to electrolysis please.

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