The NY Times has an article about how the Toyota Prius has been modified into a plug-in hybrid. Prius cars sold in Europe have the ability to run solely in battery mode, but this feature isn’t available in the Prius cars sold in North America. In additon, not all hybrids are battery/ICE, German engineers have made a hybrid fuel-cell/flywheel bus and there was also a report of a hybrid battery/compressed air car. Also, out of the standard battery/ICE hybrid cars, there are different classes of hybrids which reflect the amount of battery power that is being supplied to the engine.
Even with the increased fuel efficiency and high gasoline prices, hybrid cars are still more expensive over their lifetime than a regular car of the same size. A more recent development is hybrid trains such as those made by RailPower. These trains are diesel/battery hybrids. There is actually political will to limit emissions of trains, and so hybrid trains are thought to be the next major transportation revolution.
(Note, having recently purchased a Prius, which I’m very happy with, I may be a little biased :))
One thing that’s intrigued me is that back when steam ships were first being developed, the steam wasn’t terribly reliable – I guess boilers often had problems, wouldn’t last an entire journey, etc. Or wind was free, diesel fuel expensive, so why not save money by using sails too? So many early steamships were actually “hybrids” – they had sails too! See for example this history.
This history suggests that the complication of current hybrids will soon be replaced by the simplicity of the battery/electric system; the only thing holding that back is perhaps a factor of 3 or so in battery mass/energy storage performance; a bit of R&D may be all we need.
The NY Times article was saying that those who modified their Prius cars into plug-in cars got between 60-100 mpg fuel efficiency. The Prius now gets I think about 60 mpg max, so plug-ins obviously have potential. One thing the article was also saying though is that over 60% of the electricity generated is from coal power, and coal power pollutes more (for the same amount of energy output) than combusting gasoline does, so, plug-ins may actually increase emissions.
Coal is pretty much by all measures the worst of our current major energy sources, so increasing it’s use isn’t good. Plug-in hybrids do provide a proof in principle that replacing oil itself isn’t the issue; anything that makes electricity can in principle substitute for oil. It’s an argument against those who strongly advocate for hydrogen or bio-fuels (or the “we’re all doomed” crowd) because we’re running out of oil; electricity itself can probably work as a transportation fuel just fine.