How to Run a Car on Water

Oh, it can be done. There are no scientific laws that say you can’t run a car on water. In fact, I have personally made fire from water on a number of occasions. A Japanese company is the latest to claim they are running a car on water. See the video here:

Water-fuel car unveiled in Japan

However, what you can’t do is run a car on water without overall energy inputs greater than you get from splitting the water. In simple terms, let’s say you split water to create 10 BTUs of hydrogen. You can then use that to burn in the car, or to operate a fuel cell. When you burn the hydrogen, it reacts with oxygen to again form water. But if you want to take the water and turn it back into hydrogen, it will always take more than the 10 BTUs that you released in the first place.

So let’s say it takes 12 BTUs of input to produce 10 BTUs of hydrogen from water. What’s wrong with that? Well, why wouldn’t you just use those 12 BTUs directly, instead of going through the step of cracking the water? This would be sort of like using gasoline in your car to produce steam to drive a steam engine that actually runs the car. But it’s a lot more efficient to cut out the middleman and use the gasoline directly.

There are two possible scenarios in which this sort of scheme might make sense. One is if the conversion allowed you to operate a more efficient motor; say an electric motor instead of an internal combustion engine. The second is when it is more convenient to keep the fuel in a solid form, as was the case for my carbide lamp example. Since the fuel is only produced when water drips on the solid, there isn’t a large inventory of flammable gas or liquid that can catch fire or explode.

However, it is important to keep in mind that there is a catch. There is a way to mask the energy input, and that is what the Japanese company is doing. I had to do a bit of research, but I finally found this:

Genepax unveils water energy fuel cell system

Within the story is the key to what’s going on:

Though the company did not reveal any more detail the company president said that they had “succeeded in adopting a well-known process to produce hydrogen from water to the MEA”, similar to the mechanism that produces hydrogen by a reaction of metal hydride and water.

That clued me in as to how they were pulling this off. Metal hydrides will react with water to produce hydrogen. For instance, sodium hydride (NaH) reacts spontaneously with water as follows:

NaH + H2O → H2 (gas) + NaOH ΔH = −83.6 kJ/mol, ΔG = −109.0 kJ/mol

So, if you had NaH in your car, and you dripped water on it, you would produce hydrogen from the water. What’s the catch? Metal hydrides that react with water don’t occur naturally, because they would have already reacted. This is the same reason hydrogen doesn’t occur naturally on earth. So, it takes energy inputs to make the metal hydrides. And there is the hidden energy source in the water car. The car isn’t really running on water. It is running on a combination of water and a very reactive compound that must be replenished.

Here’s what the laws of thermodynamics tell you. Back to the 10 BTUs of energy we liberated for the water car; it would have taken well more than 10 BTUs to produce the metal hydride required for that reaction. (Note that they may not be using metal hydrides; there are other compounds that react with water to liberate hydrogen. Again, none occur naturally on earth in the reactive form, and all require significant energy inputs to produce).

So, the moral is: Sometimes it appears that the lunch is free, but the bill eventually comes anyway – when you have to replenish the catalyst. (Note: As others have correctly pointed out, the proper term here would be reagent instead of catalyst since it is almost certainly undergoing a transformation from one compound to another. I merely used the term Genepax used to describe the system.)

40 thoughts on “How to Run a Car on Water”

  1. Although it may not be a free lunch, maybe that wasn’t the point to begin with. How would you like to fill up your car with tap water and go buy some metal hydride tablets (or whatever form it comes in) at your local grocery store. That seems to take the whole hydrogen infrastructure problem right out of the automotive fuel cell equation, while also making our way of life more productive by eliminating the need for gas stations and their supporting industries. Not only that, but the large, low density, high pressure hydrogen tank can be dropped for a small tank of water; again removing a key barrier to fuel cells.


  2. Bravo! Since I am in Japan, I get these emails saying how wonderful it is that the Japanese have invented free energy (there’s that Holy Grail again). I respond by saying we have to wait and see what’s really going on. Remember the Orbo?

    So, the energy input just comes from somewhere else. There truly is no free lunch. Now my replies to these congratulatory emails can just link to this blog entry. Many thanks, RR.

  3. How would you like to fill up your car with tap water and go buy some metal hydride tablets (or whatever form it comes in) at your local grocery store.

    I can’t find a cost for sodium hydride, but the metal hydrides are generally very expensive; something like $100/lb. The reason is that it is very energy intensive, and difficult to produce and handle them. Thus, the dream of throwing some cheap substance into the tank that can turn water into hydrogen remains elusive.


  4. Anonymous,

    Honda’s FCX Clarity holds 5 kg of H2. You’d need 60 kg (132 lb) of NaH tablets to provide 5 kg of H2 via Robert’s reaction:

    NaH + H20 -> NaOH + H2

    Pulling 132 lb of NaH (which can spontaneously ignite in air) off the grocery store shelf, lugging it to your car and somehow dumping it into a fuel tank sounds like a hassle. How is this an improvement over a gas pump? And what do you do with your tank full of leftover NaOH (lye)?

  5. The aluminum one looks cheaper but heavier.
    A midsize car with a full tank of aluminum-gallium pellets, which amounts to about 350 pounds of aluminum, could take a 350-mile trip and it would cost $60, assuming the alumina is converted back to aluminum on-site at a nuclear power plant.

  6. That sounds like a good way to make use of Iceland’s geothermal and hydroelectric resources Clee. Their electricity costs are about half that of fossil fuels,and Iceland only uses about 15% of its geothermal and hydro potential.

    Maybe they could use some of that clean,renewable energy to make gas from CO2 while they are at it.

  7. I have somewhere heard that the French used a calcium hydride system to generate hydrogen for barrage balloons and observation balloons. I don’t know for sure, but I’d guess it is easier to store in dry air than calcium carbide, and it was certainly practical to store and use that for acetylene generators fuelling vehicle lamps. They just needed to spray water onto the carbide rather than allow liquid to rise onto the solid like a laboratory hydrogen generator with metal and acid, because the reaction was too fierce for that.

    On another matter, there is at least one way in which water can improve a fuel system. If you are using a gas producer, the gas is a mixture of hydrogen, carbon monoxide and diluting atmospheric nitrogen, plus trace gases. The carbon monoxide comes from exothermic partial combustion of carbon containing material in atmospheric oxygen and from endothermic reduction of water by the carbon, which also yields the hydrogen. Up to the point where it chokes combustion off, the latter reaction improves the efficiency by capturing some of the energy from the former reaction and by cutting down the proportion of diluting nitrogen output. The water comes partly from the air, partly from moisture or compounds in the fuel, and partly as deliberately introduced water.

  8. The real problem is that the state of the general public’s knowledge of science is so poor that a seemingly endless series of these ideas keep people from focusing on real solutions. Anyone with an engineering or scientific background knew without even looking that there had to be another energy input. About the only reason I can see to look at this idea is to see if it has the potential to provide chemical storage of hydrogen to drive a fuel cell electric vehicle.

  9. If you get behind a water car and push, you get a lot more mpg.

  10. The ability to understand and explain the “Second Law of Thermodynamics” should be mandatory for all journalists — print, television, and Internet.

  11. hmmm lets do a primitive energy flow diagram.

    Water car?
    metal in mine, to mining equipment, to plant to make and process hydrides, to transportation to market, to the market, to car


    aluminum mine, to aluminum manufacturing facility, to market, to, to car


    Sun, to plant, to harvest/planting,
    to ethanol mill, transported to market, to car

    Electric Cars.

    From Electricity source, to car

    Electric cars are the best bet for personal transportation right now, as you can see the more steps you take in the flow, the more compounding inefficiency’s you have, It takes a ton of electricity to make aluminum, so why not just take that electricity and put it in your car.. Anyway, that’s all my opinion but you’ve got to admit electric cars are the only viable alternative.

  12. The real question is:

    You may have to replace the whole catalyst membrane.

    How long will it last? How much will it cost? How much will the car cost?

    And, with new materials research, it is quite likely they will find a cheaper way to manufacture it.

    Again, we’re not going to violate the laws of thermodynamics, but it is possible to come up with a series of reactions that allow us to cheaply make the particular metal hydride (which wasn’t specified) that they use.

    There’s no such thing as a free lunch in terms of physics, but there are cheap lunches when it comes to economics.

    So, don’t write this one off as a fraud. It is an important step in a new direction. For christ sakes, they created materials with negative refractive indexes that make them invisible to infrared and low range red spectrum.

    With enough money at stake, and enough minds working on it, I’m sure they can find a cheaper way to manufacture the hydrides. And once they do, battery technology will improve as well.

    Don’t count this as done.

  13. Speculation in the absense of data is not very informative. Yes, in the past, expensive metals may have been needed. However, nothing so far from GenePax indicates that there are metals to be replenished.

    Certainly after reading about it, I wanted to be disabused of the notion that we could “run cars on water” — but I don’t have enough info to make that evaluation…and you don’t either.

  14. So, don’t write this one off as a fraud. It is an important step in a new direction.

    First, I am not suggesting that it’s a fraud. I am suggesting that the car isn’t actually being run on water. It’s being run on water and a very reactive metal catalyst. And the point of discussing the physics is that the energy inputs into producing the catalyst could have directly been used to operate the car. No water required.


  15. Certainly after reading about it, I wanted to be disabused of the notion that we could “run cars on water” — but I don’t have enough info to make that evaluation…and you don’t either.

    First, I wasn’t trying to disabuse anyone of anything. I am explaining “how” a car can run on water. But you miss the point that the car is not actually running on water. The car requires a very reactive metal catalyst that is necessarily energy intensive to produce.

    I could also run a car on water just using sodium metal. But again, it takes a lot of energy to produce sodium metal; energy that could have just been used directly to power the car.


  16. If it’s possible to recycle the NaOH and eventually reduce the inputs into just energy, then it sounds like the type of energy storage device that would make green power possible. Does anyone know any of the efficiencies around making and using the NaH?

  17. Ahh, RR at his ever lovin’ best. ‘Tis a pleasure to behold. Now I have a place to link in response to all the chatter on this topic.

    I eagerly await your critiques of automotive battery storage technologies when you are able. Not because I know what conclusions you will reach, but because I don’t.

  18. Does anyone know any of the efficiencies around making and using the NaH?

    Just to clarify, I only used NaH as an example. They are most likely using something else that has the same characteristics of reactivity with water. Generally speaking, these sorts of catalysts are going to be energy intensive to produce, and they will be consumed as they react with water. I can envision that there might be an economic solution here, but not one that is overall very energy efficient.

    For instance, in a place where electricity is very cheap (like Iceland) you could produce the react metals cheaply. You could then possibly transport them for use elsewhere. This could be a way of “transporting” electricity across the ocean.


  19. Oh, there you go again Robert. First it was the ethanol problem and now it’s the poor little water car. Quick, some one head off the metal hydrate lobbyists before they get to the US congress!wzskw

  20. Greencar Congress is reporting on this very topic, that is newly released research results from Uppsala University, on use of metal hydrates, mainly magnesium based, in fuel cell technology.

    The article is somewhat over my head but it does take recycling of the the metal hydrates into account, and Uppsala’s reference point research was conducted by three Japanese scientists.

    Now, I live in Japan, and have worked with the R & D department of a major Japanese high-tech automotive parts company. I find it very difficult to believe that a Japanese start-up company would take the trouble to produce a WORKING prototype of a car, claim to have working relationships with a major auto company here in Japan, and get resulting media attention IF the product in question is so obviously ineffecient in its energy usuage. Certainly, ANY of the engineers at Mitsubishi, etc., would simply ask a few questions, go on to do some testing and then either toss the project away or take further interest in it.

    Robert has pointed out some very valid points but I simply find it very suspect that a car such as this would have such obvious detriments, given the market and the current attention to R & D here.

  21. Doggydogworld, That is my big question too. Sure NaOH is a valuable chemical/product, but I’m not convinced a bunch of consumer grocery getters can safely or reliably make proper use of the lye in their car’s tank. Funny how cleaning the air means dumping liquid hazardous materials like lye around. Go Al Gore! Save us all! (sarcastic)

  22. I actually like the hydrogen powered electric car model, but it will realistically require a lot of energy/time to set up, wasting energy in the process, and I am not wealthy or car dependent enough to purchase such new tech.

    For right now, I’m wondering about the feasibility of burning hydrogen in conventional Internal combustion engines.
    I’ve been reading about folks wiring electrolysis devices to their car alternators and burning the Hydrogen-Oxygen mixture in their internal combustion engines. They claim at idle, no hydrocarbon fuel is required, and overall 30-60% fuel savings. It seems like another perpetual motion machine, but part of me wants to experiment. doesn’t seem dangerous, because fuel is not made or stored when the engine isn’t spinning, and any leaks will be small and disperse rapidly. If this can work, it would definately clean up the air and may help a transition to a hydrogen economy.

  23. “It’s being run on water and a very reactive metal catalyst”

    I think you mean “reagent”, not “catalyst”. A catalyst wouldn’t destroyed in the reaction, as the metal hydride is.

  24. I think you mean “reagent”, not “catalyst”. A catalyst wouldn’t destroyed in the reaction, as the metal hydride is.

    Yes, that is technically correct. While they call it a catalyst, in reality it is consumed in the reaction. As such, it is a reagent.


  25. Robert has pointed out some very valid points but I simply find it very suspect that a car such as this would have such obvious detriments, given the market and the current attention to R & D here.

    I think there is a general misunderstanding here. I did not set out to debunk the water car. What I did set out to do was explain how you can run a car on water. It is not a fraud, but it does contain energy inputs outside of those which are obvious. That was my point.

    Of course my other point – and it is a fundamental law of thermodynamics – is that those energy inputs have to be greater than what you get out of the water. In some cases, that may make sense. I will give some examples in an upcoming post.


  26. Nice article, but explain to me how a nuclear reation works. Its seems it unlocks mor eenergy than it takes to release it. So maybe we just haven’t found the right way to unlock/release it…? We should all be focusing on how to do that not simply saying it can’t be done.

  27. There is no mystery about a nuclear reaction. Mass is converted to energy according to E=MC^2.

    And I didn’t say it couldn’t be done. I explained how it is done, and that it takes quite a bit more than “just water.”


  28. Metal hydrides are very hard to create. To create metallic hydrides, you need to compress hydrogen at million+ psi.
    Genepax just wasted their time and money on a car that will spend more money.

  29. I think what you are saying is that there is no such thing as a perpetual motion machine. This is correct. What you have to look at though is how much energy is “wasted” on a gasoline engine. We have to use much more energy to power a gasoline engine than it produces. Everything is like that.

  30. I live in Missouri, the cave state and have used calcium carbide for years in my spelunking. It’s made of a mixture of limestone and coke (as in steel making) in a water slurry that is heated to over 5,000 degrees F, a temperature a moderate sized (think backyard) solar dish furnace could generate on a sunny day. That’s the energy input side of what I’m suggesting… solar heat to produce the reactant from two common, relatively cheap materials. Heck, the whole state of Missouri is made of limestone and our neighboring state, Illinois, has a lot of coke available.

    Some years ago, around the time of the first energy crisis, a local private inventor made the St. Louis evening news with his carbide run car. He placed a moving round metal plate (to make a carousel) in an ordinary pressure cooker and placed a pound of carbide on the constantly turning platform. He welded a pipe, control valve and sprayer head to the lid of the cooker to let a controlled amount of water in from a small tank fall on the carbide and had another pipe to carry off the acetylene gas it generated to an old inner tube he was using as a gas reservoir and pressure regulator.

    From the inner tube he ran a line to the carburetor of his car. The only modification he made to the carburetor was to change the size of the jet orifice slightly to make it work better with a gas instead of a liquid. It’s the same modification that you would need if you decided to run your car on propane instead of gasoline.

    He claimed he could drive about 320 miles on one pound of carbide ($ .87/lb at that time) and about a gallon of water. They showed video of his cobbled together apparatus, (including auto tire inner-tube) in the back seat of his car and had footage of him driving it around with no problems or loss of performance. After that story appeared, there was no follow-up and I’ve never heard another thing about it.

    If you replaced the primitive inner-tube with an more sophisticated pressure cell and gas regulator and did a little engineering on the pressure cooker gas generator (basically a giant carbide lamp) to make it smaller and safer, this on-board fuel maker would probably be easy to fit under the hood or in a corner of the trunk of just about any car or truck. All you’d have to buy would be the cheap limestone and coke for your backyard solar carbide maker and it’s good-by gas stations!

  31. rzpogi has an interesting story I believe. After have reading all other comments I think the most useful conclusion would be that energy stored in highly reactive “stone” would make a storage with low volume/energy. If the sun can be used to “load” the “stone” we both get a solution to storing solar energy over season or to transport it to other parts of the world and a suistable fuel to vehicles. The energy minister of Marocko has some years ago anounced that he has a lot of desert with sun. Theoreticly it only needs solarpanels 700x700km to provide all energy need for the entire world!

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  33. Good Evening Mr. Rapier,

    I really enjoyed your article on “How to Run a Car on Water” You are so right that a car can run on water, but not just water. Your article is so informative and with great timing, because how high gas cost today. I remember a time when regular gasoline use to cost $99c a gallon, a long time ago! Now, it is so expensive, but because of people with your insight we can read articles like this one and see that cars can run with tap water as your primary fuel source and because you don’t need to fill-up your gas tank as often, you’ll have 40-80% more cash in your pocket at the end of each and every month.

    Once again, Thank you for a great article and I look forward to reading more from you.

    Vidal Aponte
    If you would like more information on how to actually run your car with water you can go to

  34. This thread is now attracting nothing but people linking to “Run Your Car on Water” sites. Since that sort of advertisement is not allowed, I am locking this thread.


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