Other companies are taking the green-is-convenient approach to the next level. Plug-in electric cars and petrol-electric hybrid cars have both been around for years. Both typically charge using a special unit that must be installed in the home, and use a few dollars worth of electricity for each charge.

But a new trend of "plug-in hybrid" cars combines both. Several car companies, including Toyota, DaimlerChrysler and GM, are working on plug-in hybrids, which have additional batteries that can be charged by plugging the car in. These cars can run on batteries alone for as much as 100 miles between charges. Then they operate as conventional hybrid cars, alternating between the petrol engine and electric motor.

Ford unveiled last month its most advanced concept car, the Flexible Series Hybrid Edge, a zero-emissions, plug-in hybrid hydrogen fuel cell vehicle that runs for the first 25 miles on electricity only.

A secretive Texas start-up called EEStor claims to have invented a battery technology -- actually, a fast-charging ceramic "ultracapacitor" -- which provides 10 times the power of conventional batteries at half the cost and without toxic chemicals. The new batteries may show up as early as this year in a new car from Toronto-based Zenn Motor. Because of the EEStor battery technology, the Zenn cars should charge in minutes, rather than hours, and would have many times the range of today's electric cars. Cars running on EEStor batteries may be as powerful as cars running on petrol, and cheaper and easier to own than petrol/electric hybrids. The new battery technology is reportedly applicable to laptops and other consumer devices, too.

All these cars will be desirable to consumers because they're easier to own.

The research revolution

Green technology innovators have faced an uphill battle getting funding for start-ups that might develop alternative energy products. But all that is changing, thanks to deep-pocket investors like Google and even the Pentagon.

One start-up, called Nanosolar, in California, has received more than $100 million in funding and was started using seed money from the founders of Google. Nanosolar has invented a solar panel technology that can be cheaply mass produced. The company claims that its solar panels will be able to generate power almost as cheaply as conventional sources of electricity. The massive funding behind this company, which comes from venture capital firms and government grants, is part of a clear trend toward growing investment in green technologies.

Innovation in green technologies is coming from another surprising source -- the Pentagon. The agency that brought us the Internet and GPS is now working on radical advancements in solar, wind, hybrid and other green technologies.

When the US military rolled into Baghdad, it was followed by a dangerous, slow and expensive convoy of fuel tankers and trucks full of batteries. All those military gadgets and petrol-guzzling Humvees turned out to be a major limitation in large-scale battle. As a result, the Pentagon is working on green technologies, such as hybrid vehicles.

There are military advantages to green technologies as well. Hybrid Humvee replacements can switch to "stealth mode", which is not only electric, but silent. Solar and wind generators don't have the "heat signatures" enemies can use to target the heat produced by diesel generators that typically power Army outposts. As with other military technology developments, these green innovations are likely to end up in consumer products as well.

Development and funding of projects like this are growing in part because of changes on the political front, where another "revolution" is about to take place.