- Hydrogen gas has to be liberated from petrochemicals (oil) or electrolyzed from water using electrical energy. This process has much greater inefficiencies than with electrical battery storage.

Clarkson, and the "Top Plug" team, while continually pouncing on battery cars for refilling from power station electricity, appear to have swallowed the "hydrogen is the most abundant element in the universe" line and presume it's just lying about ready to fling in your car.

 - There is *no* hydrogen distribution system in place and is not going to be one anytime soon because it is so difficult and expensive.

 - There is (and has to be) a sizable lithium battery in the Honda Clarity for energy regeneration under breaking and buffering the power from the fuel cell (because it is too slow on it's own).

In fact, this car uses identical technology to the Tesla, except that a hydrogen cell recharges the drive battery, instead of having a bigger battery or a high efficiency petrol generator topping it up (like the PML flightlink QED Mini).

What I can't wait to see is the all British Lightning GT driving around the Top Gear track after their first cars are produced in 2009. They use PMLs 'Hi-Pa drive' system of 4 in-wheel motors, which give the Lightning the same 0-60 time as the Tesla, but a slightly higher top speed, no overheating problems and 4 wheel independent drive for perfect handling.

Above: Lightning GT

This technology has also been taken fully on-board by Volvo who have a serious plug-in hybrid scheduled for full roll out in under 4 years, and there is the Ford F150 pickup truck concept demonstrating that big vehicles can be made green just as easily.

[UPDATED 2014-03-26 - Refurbished with new pictures.]

The Lightning GT seem to have dropped hub motors some time ago, and this link (previously included) is officially dead - http://www.hipadrive.com/phev.html

But more recently, engineering CEO superstar, Elon Musk, called out fuel cell bullshit too.

0-60mph < 5 seconds
65-80 mpg with approx 600 mile range
zero emmissions for short to medium travel

Wheel hub motors (4 of): 750Nm, 15kg, 480A, 450V, 1800rpm.
Brushless permanent magnets, constant torque at all speeds.
Integrated inverter circuitry: 24 Phase sine wave (IGBT), water cooled.

Battery: 300V, 70Amp hour, Lithium Polymer (700A peak).
Therefore: 21kW hour, 75600000J=75.6MJ
(typical lightning bolt ~500MJ; thinking about accidents)
100 mile battery range @ 70mph

Ultra Capacitors: 350V, 11 Farad, 700A limited (3850 Coulombs)
Therefore: 0.67MJ

Generator: 250cc, 2 stroke gasoline, 15kW (at it's 7000rpm).
Power required to cruise at 70mph

Energy re-circulator: 1400A IGBT distributer.

Indipendent traction control via torque adjustment, yada, yada...
Thier inovation is in the compactness of the motor (their speciality) and the efficiency of the motor drive electronics (IGBT). The generator could be a fuel cell, or any other portable source, but battery/capacitor advancements look set to make everything else obsolete.

It's basically the prototype of the type of car comming off the line in the film Minority Report (i believe Tom Cruise gets trapped/built into a chasis during a fight, then escapes by driving it away!): Basically, new cars in the next couple of years (PML claim to be working with 3 large scale automotive manufacturers to bring out full products by the beginning of next year) will be the prototypes of car perfection: chasis with 4 integrated motor/wheels and a really big capacitor. They'll be charged up at home, in car parks, at *power* stations, probably by inductive coils (or wireless power transmission, when that technology properly comes of age) so u'll probly forget about this strange concept of fuel (!?) altogether...

All that's left is for the cars to drive themselves, then u have the perfect private/public transport system. Public transport with a driverless, pollution neutral fleet of vehicals of any size. Providing door to door, personalisal transport and dynamically reroutable busses for the busiest routes (to avoid rush hour/end of night, taxi rank style queues).

Can't wait to see if stanley pulls off safe town driving during the next grand challenge installment this November. But in a way i'd rather the problem wasn't solved too quickly, so that i personally have some time to work on solving it. Naturally there's always room for improvements.

I'd say this will all be realised in well under 20 years (for post industrial regions). Maybe that sounds too good to be true? Well, u'd better get used to lots of stuff sounding like that and then *actually* happening; it's the Singularity baby! Though i need not preach to a public that take for granted mobile phones and internet access, u now couldn't live without, when u hadn't even heard of such things 20 years ago!