Okay, a little more serious. The Clarity's fuel cell stack produces electricity that is sent to a battery, and from there powers the car's electric motor. How fuel cells work is explained here. The cells use hydrogen and oxygen to produce electricity. Where does the hydrogen come from? Honda doesn't say, except to note that it is "stored in a fuel tank onboard the vehicle." The oxygen is from the atmosphere.

Which is all fine, but where does the driver get the hydrogen to begin with? Hydrogen gas, H2, is not found free in nature. There are two ways to separate hydrogen from its compounds: hydrolysis and reforming. The former, most commonly and easily done with water, uses electricity and a catalyst to break H2O into H2 and O2. Reforming uses heat instead of electricity.

More than 90 percent of the hydrogen produced in the world is obtained by steam reforming of natural gas. It's not energy efficient since the energy gained from the hydrogen gas is less than the energy required to produce it. H2 produced in this manner is not used for fuel, though, but for industrial and chemical purposes.

There is nothing on the Clarity's web pages to indicate that H2 is produced aboard the vehicle. It can be done using either method. See, for example, the Youtube vid at the end of my post on the coming 500 mpg car to see how reforming works aboard a car using the exhaust for heat. Substitute alternator-supplied electricity for exhaust reforming and you can eletrolyze H2 from water. Both such systems supply gasoline engines, though, while the Clarity uses no petroleum product for fuel. (I remember reading that GM is working on an on-board system to produce H2 from the auto's gasoline itself by reforming. Sorry, didn't record the link. Here it is.)

So the source of the Clarity's hydrogen is perhaps another issue to consider. Nothing on the site indicates that H2 is made aboard the car. If the H2 is produced using electrcity somewhere, then odds are that coal produces that electricity. So the CO2 production has been merely moved off the auto to another emitter. Also, does it take more energy to produce the H2, whatever the source, than the H2 supplies? If so, exactly what is the benefit of the Clarity?

I also note that H2 gas is itself pretty much the perfect fuel for internal-combustion engines. Engineers have known for decades that hydrogen injection into the air intake, just before injecting into the combustion chamber, improves fuel efficiency enormously. By weight, hydrogen has three times the energy of gasoline. The first patent for this scheme was granted in 1934.

The rub has always been how to get the hydrogen gas. H2 is very difficult to store. Hydrogen atoms are so small that making a leakproof container is no simple thing. H2 gas takes up a lot of space, making it imperative either to compress it (adding a safety concern and increasing the leaking challenge) or liquefying it (adding the refrigeration problem of mobile storage). And both compression and liquefaction of H2 add weight and complexity to an auto.

Presumably, the Clarity has an on-board tank of compressed H2. I don't know enough about fuel-cell engineering to know how much H2 it takes to propel the car 300 miles, the driving range car companies aim for no matter the fuel.

On the whole, I would have to say that on-board generation of H2 gas, to be added to the existing fuel-air mixture of a gasoline-powered vehicle, would essentially solve the problem Honda's engineers were trying to solve. The advantage is that the H2 would be electrolyzed aboard the car from either water-plus-catalyst (baking soda works) or heat-reformed from either water or the gasoline itself. Drivers then need not drive around with a compressed-gas tank and can refuel with water or gasoline just as simply as they refuel now.

Update: The car's web site does say on one page that "Hydrogen fuel stations are critical to the deployment of a fuel cell car," clearly meaning that the car does not generate its H2 aboard. This is made more explicit elsewhere on the site, too.

I am not suggesting that the negative balance of energy derived from H2 vs. the energy required to make it can be overcome. I have not yet found a way to repeal the second law of thermodynamics! It's the ratio that counts - witness the debate about whether making corn ethanol is really worth the energy costs to grow and transport the corn in the first place.

I am suggesting that on-board "cracking" of bound hydrogen from water or hydrocarbon fuel would seem to offer a better ratio. Here's why. The heat the Israeli engineer uses (of the Youtube vid referenced in the post) to reform H2 aboard his van comes from the van's exhaust. That means he is using a waste product of combustion to reform the H2. Whether he uses the H2 system or not, the van will still waste that exhaust's heat. So he's essentially using free energy. The exhaust's heat is a sunk cost no matter what. Now it's true that once the reforming system in put into place, a closed loop forms in which H2 is made, burned and heat therefrom is exhausted, then the heat is used to reform H2, and so on. But the effective energy loss is still minimal because the van will exhaust heat whether using H2 or not. It's the same principle of the Toyota Prius' regenerative braking.

BTW, I checked this assessment with a bona fide, practicing chemical engineer and he agreed. General Motors's engineers must agree, since "GM is working with oil companies on a new gasoline formula that would be more suitable for extracting hydrogen."

I am less certain that the same assessment applies to using electricity from the car's alternator to electrolyze H2 from water. It raises the load requirement on the car's electrical generation system, and this requires the motor to burn more fuel. But some of the increased load will be met using the H2 as fuel and some by burning the gasoline. If relatively speaking, less H2 is used to meet the load than gasoline (which is going to be burned anyway), then the same net calculation may still be true. But this seems less obvious than using exhaust to reform H2.

General Motors has a web page on the Prospects, Promises and Challenges of fuel cell technology, including an extended page about hydrogen storage.

Fuel cell technology uses pure hydrogen in the liquid or gaseous form. Currently, this liquid hydrogen is derived from gasoline or methanol via a processor. General Motors believes gasoline as a hydrogen source provides the best bridge to a completely hydrogen economy, because world markets already operate in a gasoline infrastructure. However, GM also believes that a hydrogen infrastructure, similar to the gasoline model of today, is the ultimate answer.

This begs the question, though: can you drive a fuel-cell car farther on H2 derived from a gallon of gasoline than you could on the gas itself? Perhaps we will with the stll-theoretical special formulations of gasoline. If not, then the economics don't make sense and the idea won't catch on no matter the presumed ecological benefits. (I have to assume that GM's folks know this, wouldn't you?) But modern gas engines combust extremely efficiently - according to Popular Mechanics's automotive writer, "Your vehicle already burns over 99 percent of the fuel you pay for."