Assuming there's eventually an economical supply of hydrogen from acceptable sources other than petroleum, the next challenge lies in creating the infrastructure to store, transport, and distribute it. When you consider that those of us in electronics already deal with an infrastructure that routinely handles large volumes of liquid oxygen and nasty gases like silane and arsine and (I still hate this) metal organics, not to mention the fact that most people pump their own gasoline, developing a safe hydrogen infrastructure is certainly achievable.
For distribution, it just isn't practical to ship and store hydrogen at high pressure for most of the journey from source to consumer. For one thing, compressing the gas to something like 30,000 psi requires lots of energy. Liquification is out of the question because it would take even more energy.
One alternative is to store the hydrogen as a component of ammonia, from which it can be recovered at the point of transfer by using a catalytic reformer. Another alternative is to store the hydrogen as metal hydrides, either sodium borohydride, lithium aluminum hydride, or ammonia borane. Sodium borohydride is a hot prospect because it can be used directly in fuel cells without the need for platinum catalysts. On the other hand, recycling sodium borohydride is another sizable energy consumer.
Electric Power Stored In Batteries
People like my solar-cell contractor and his all-electric RAV4 tend to react passionately when somebody mentions hydrogen-fueled cars. They worship their battery-driven vehicles and will point out that by simply using off-the-shelf components, they get 2 to 3.3 mi/kWh, while a car that gets 30 mpg is achieving about 0.9 mi/kWh (that's assuming that a gallon of gas can produce 33.6 kWh).
But is it really that simple? I live in Silicon Valley, and many of the EV fans here do their own conversions. Acterra, a Bay Area environmental group, spent around $7000 to convert an MG Midget to an EV. (No, not the original TD Midget, rather the 1960s version.) Like the original Midget, the EV version is something you learn to love in spite of its limitations. Top speed is 65 mph and range is about 30 miles. The coolness factor, though, is very high.
For the Acterra conversion, out went the engine, gas tank, exhaust system, and so on. In went a 20-hp (60 hp max) Prestolite series dc motor connected to the standard transmission by an adapter plate, an Auburn C600 motor controller, and 12 12-V, 30XHS Trojan deep-cycle, lead-acid batteries. A dc-dc converter charges a couple of gel cells that run the 12-V headlights and similar features.
Commercially, what's keeping the EV flame alive are vehicles like Mitsubishi's Lancer Evolution MIEV. (The "I" stands for in-wheel.) It uses outer-rotor in-wheel motors on all four of its 20-in. wheels (Fig. 6). Each wheel-hub motor produces 50 kW of power and 518 Newton-meters of torque. Acceleration from zero to 60 mph takes less than eight seconds. Top speed is around 110 mph. The juice to run it comes from a lithium-ion (Li-ion) storage battery.
The drawbacks of pure electric vehicles are range and charging time. Factory specifications for my solar-panel contractor's RAV4 claim a range of 80 to 120 miles on a full charge. That charge comes from 24 12-V, 95-Ah, NiMH batteries with a total potential output of 27.4 kWh. (Actual range depends on speed-induced aerodynamic drag. Top speed is 80 mph, and the RAV4 is a boxy beast.)
Reducing charging time offers some interesting opportunities for EEs. Activity is rather intense within the worlds of battery-charge metering and charge-current shaping for handheld devices and laptops. It's interesting to speculate on how that experience could be extended to charging electric-car batteries.
At the "pump," charging can be accomplished either by a direct connection or inductively. In the latter, a "paddle" is inserted into a slot on the car. The paddle contains one winding of a transformer. The other winding is the car. The paddle has obvious safety advantages.
Limited battery life appears to be a bogus objection to all-electric vehicles. According to the Electric Power Research institute, "Toyota RAV4-EVs are successfully operating for more than 100,000 miles on the original NiMH battery, and are projected to last for 130,000 to 150,000 miles." That's not many fewer miles than Electronic Design contributor Bob Pease has on his famous 1970 VW bug.