Or, can any conceivable technology for propelling land vehicles ever be as cheap (allowing for inflation) as gasoline used to be? Many people say (and some gleefully) that the era of cheap transportation is over forever. that if anything could be cheaper than four dollar a gallon gasoline, we’d already be using it. But on the other hand we haven’t invented everything yet, and a lot of possible replacements for petroleum would require decades of establishing infrastructure (hydrogen, etc.), after which the marginal cost would be lower. What say you?
It’s possible. I don’t think anyone is saying it can’t happen, just that we’d be fools to count on it happening.
Mr. Fusion! Runs on household waste.
It’s conceivable that roof-top solar panels could become cheap enough and efficient enough to make it possible to charge your own pluggable electric car for less than the equivalent gas vehicle.
Well, it’s still (relatively) cheap NOW. The average person (in the US anyway, but in Europe as well and in several other places I can think of off the top of my head) can afford to drive around after all…they can go on vacation, drive to work, drive to the store, go on a long drive for a weekend. Think about that in historical terms. Before the advent of the car, how many people could afford a good horse and had one available for casual travel? A horse and buggy? Could afford to travel via train or by ship, casually, just for the fun of it?
Yeah, I think several new technologies have the potential to ‘make driving cheap again’…or at least keep driving cheap enough that the average person will have access to transport undreamed of by even the elite in the past. Hydrogen (or methane) fuel cells have vast potential…assuming someone works out all the little ( 
) infrastructure and distribution problems. So does all electric, again assuming someone figures out how to make batteries cheaper, lighter, faster recharging and longer range. Solar also has a lot of promise and potential.
The people who gleefully note that we are at the end of ‘cheap transportation’ are either of the back door neo-Luddite variety (lots of the more fanatical eco types fall into this category IMHO) or sort of like the folks who were wringing their hands over the fact that we were running out of whale oil (or trees, or whatever) in bygone ages. Hell, we could just stay with the CURRENT technology for a couple more decades of (relatively) cheap transport if we wanted to (and weren’t worried about CO2 and such)…I seriously doubt that the price of gas in the US will rise to the CURRENT price of gas in Europe or elsewhere in the world in that time frame…and you know, THEY are still able to travel about fairly well.
Personally I think we are on the cusp of a bunch of alternatives, and the current rise in price (in the US, because we really are whiners sometimes) is flogging the industry even harder to come up with those alternatives. I’ve seen some pretty exciting things in solar (printable, cheaper, thinner cells), battery (faster recharge, holds more charge, lighter, cheaper), hydrogen (several car manufacturers have already announced they will be starting production in the near future), etc. I know it’s unfashionable in some parts to rely on technological fixes for all our problems…but seriously, it’s not like it’s a great leap of faith that ONE of those will pan out and give us a viable alternative. Not considering A) the amount of money being poured into research and development, and B) the amount of money at stake for whoever wins the alternative wars…we aren’t just talking about millions or even billions…but potentially hundreds of billions or even trillions. For that kind of money…yeah, I think someone will figure it out. YMMV of course.
-XT
Does enough energy in the form of sunlight land on the roof of a typical car over, say, eight hours, to recharge the batteries enough for the commute home, say, a 30 minute drive?
Personally, I think it’ll be a combination of more nuclear plants providing cheap electricity combined with greater in-car computing power allowing it to drive itself at optimal efficiency. Plus a reactor in northern Alberta allowing mass processing of tar-sands oil. Longer term, cars made of nanomaterials that are stronger than steel, but the whole car weighs as much as a moped. 
“Ever” is a long time, and categorical pronouncements are always iffy.
But I think the CEO of Exxon put it best: “There are all kinds of potential alternative fuels, but realistically, I’m betting that the hearse that carries me away after my funeral will be running on gasoline.”
I think he’s right. Even decades from now, gasoline will probably remain the primary source of motor power. Petroleum isn’t getting more abundant and demand isn’t falling. So, it probably can’t (and probably SHOULDN’T) get significantly cheaper.
I’m guessing Fear Itself was talking about solar panels for the roof of your house, not the roof of your car. At the Earth’s surface the maximum solar energy available is around 320 BTU/hr/ft^2. A three foot by five foot solar panel could not collect more than 38,400 BTU over an eight hour period, enough to replace about a third of a gallon of gasoline.
Well, the next-gen Prius will have solar panels on it. To run the AC off of, apparently.
Not only is cheap/stable fuel available it just went online. Bio-diesel from algae is 30 times more productive than soy and that figure is expected to increase to 120 times the productivity of soy based diesel. The process uses Co2 captured from coal plants. We have all the land necessary to sustain the transportation needs of the United States. We also have the coal reserves to do the same thing for the foreseeable future (coal to liquid fuel conversion).