A government program to help develop hydrogen-fuel-cell-powered vehicles--a hallmark of the Bush administration--has been almost completely wiped out in the Obama administration's proposed budget.

In 2008, hydrogen technology research and development at the Department of Energy got over $200 million. That's been scaled down to about $70 million in the current budget, and that's for fuel cells of all sorts--including generating electricity for the grid, and not just hydrogen fuel cells for vehicles.

Major automakers have also recently scaled back their hydrogen-fuel-cell vehicle development, emphasizing hybrids, plug-in hybrids, and electric vehicles instead.

Hydrogen fuel cells don't emit pollutants--just water. And the amount of hydrogen that can be stored, by weight, is tremendous. But fuel cells are expensive, hydrogen is hard to come by (there aren't many hydrogen filling stations), and it's difficult to store in a small volume. What's more, the cleanest way to make hydrogen--electrolysis using electricity from renewable sources--is expensive and inefficient.

What do you think? Is it about time we abandon hydrogen-fuel-cell vehicles? Or do they still have a place in future transportation?

A solar roof will simply ventilate the 2010 Prius.

The solar roof that Toyota is offering as an option on its next-generation Prius hybrid sedan may be even less useful than expected, according to a report in the specialty publication EVWorld. The solar panels, reports EVWorld, will add not a microwatt of charge to drive the Prius.

Last summer, Technology Review looked at the potential impact of adding a solar roof to the Prius when rumors of Toyota's plans first emerged. The clear conclusion of the experts was this: keep solar panels on rooftops, where they can be tilted toward the sun for maximum efficiency. A solar rooftop would be just a "marketing gimmick," said Andrew Frank, a plug-in hybrid pioneer at the University of California, Davis, and chief technology officer for UC-Davis hybrid-vehicle spinoff Efficient Drivetrains.

Toyota, it turns out, won't even bother plugging its solar rooftop panel into the 2010 Prius's nickel-metal-hydride battery. EVWorld editor Bill Moore, citing a conversation with Akihiko Otsuka, chief engineer for the Prius redesign, writes that

Toyota tried it and apparently discovered that for not-entirely-well-understood reasons, connecting the PV panels to the battery turns them into an "antenna" of sorts, which at the very least seems to disrupt the car's radio.

So Toyota left it at that. The solar roof will simply help keep the car cool when it's parked by running a fan to ventilate the car. For the average driver, that could be somewhat useful for, say, half the year.

I spoke with Otsuka while reporting from the Geneva Motor Show earlier this month, and learned that Toyota engineers are targeting a range of 20 kilometers in the EV mode for the plug-in version of the Prius. The lithium-battery-equipped vehicle is to be offered to Toyota's fleet customers by the end of this year.

That would mark a boost over the 10-to-15-kilometer range offered by the nickel-metal-hydride-powered plug-in Prius that Toyota has been testing. But it remains just a third of the 60-kilometer range that GM is promising for its Chevy Volt plug-in hybrid, which is due out next year. GM's design has already set off a debate over the cost effectiveness and efficiency of carrying the battery capacity that such range requires.

Prototype i-MiEV on show at this week's Geneva car confab. Sketch: Mitsubishi

French automaker PSA Peugeot Citroën kicked off the Geneva Motor Show this morning by announcing that it is pursuing a deal with Mitsubishi Motor to develop a compact electric car for sale in Europe next year. It will be based on Mitsubishi's i-MiEV, an approximately 160-kilometer-range commuter car that the company plans to roll out in Japan this summer.

Plenty more compact four-wheelers are in the automotive pipeline. Daimler will sell a battery version of its popular Smart Fortwo next year, and Volkswagen is engineering a commuter EV called the Audi Up! with a top speed of 130 kilometers per hour and roughly 100 kilometers of range. Renault is engineering a pair of battery-powered cars, to be produced starting in 2011.

These automakers are betting that there will be a market for smaller electric vehicles (EVs) that will be cheaper to build and far cheaper and cleaner to operate than regular hybrids. With battery technology developing rapidly and the automotive market in turmoil, that logic even has gas-electric hybrid champion Toyota hedging its bets. At the Detroit auto show in January, Toyota put the spotlight on new versions of its Prius, but also announced plans to offer a commuter EV in 2012.

To be fair, most of the companies talking up tiny EVs are similarly hedging their bets, simultaneously developing a range of hybrid options. PSA Peugeot Citroën plans to launch two diesel-hybrid vehicles in 2011--the Citroën DS5 HYbrid4 and the Peugeot 3008 HYbrid4--and it's also developing a "multipurpose" plug-in hybrid EV analogous to the Chevy Volt.

Like the Volt, PSA's plug-in will be a series hybrid, in which a small fuel-efficient engine serves only to recharge the batteries en route. Unlike the Volt, however, the engine can be swapped out and additional batteries swapped in for longer-range city driving.