All vehicles are incredibly power consuming (compared to iPods) and there are basic limits to improving this. If you want a vehicle that is large enough to hold a human and can push air out of the way at 60 mph, it's going to take a lot of energy. Driving habits, aerodynamics, and size can change this usage by a factor of order unity, but they can't do it by orders of magnitude. Thus, alternative energy sources must approach the energy density of petroleum if they are to be competitive.

No, people need to realize that cars weighing in at 3+ tons with capacity for 5+ passengers to transport a single person to work are not viable. Because the "give us something we can hotswap for oil" attitude is obviously going nowhere.

My current car weighs 0.8 tons and has a 50 miles per gallon consumption (Renault Twingo), and the one I had before weighed 0.7 tons and could archieve up to 115 miles per gallon (according to an article) though something like 60 or 70 mpg was more normal.

http://www.aftermarketleads.com/2011/12/maruti-alto-delivers...

I suspect the problem is partly American attitude towards small cars. Japanese, Europeans and South Americans have much more efficient cars for daily commute.

You really need to specify whether that 50 miles per gallon is in US or UK gallons ...

US gallon is 3.78 Liters, UK gallon is 4.54 Liters.

US gallons: 50 MPG = 21.26 km/liter UK gallons: 50 MPG = 17.70 km/liter

50 MPG (UK) is 41.6 MPG (US).

In my Hyundai Accent (Korean) I get 34 - 36 MPG (US) depending on how I drive it. It is not nearly as efficient as a Renault Twingo or my grandma's Toyota Aigo (awesome little car).

Sorry, it's even worse, I picked the gallon figures off the Internet because I was lazy. Thanks for the correction and calling me out.

It seems the Twingo figure was in UK mpg, so US mpg would be closer to 40 mpg (US).

Same for the Maruti figure, it would actually be 50 to 60 mpg (US).

From what I read, both are still way more efficient than your average American car.

I'd like to get an Accent, but they're close to 30.000 dollars after (humungous) taxes here in Uruguay.

Thinking like this is what prevents real innovation. All of these statements seem to be common sense, but they're all individually false when you dig below the surface.

There are huge variations in how much vehicles consume on a per-passenger basis. And there's no reason that alternative energy / electric must approach the energy density of petroleum - that assumption only holds if you're assuming that a vehicle must carry all of its power with it (and many existing ones don't.) Looks at catenary-powered buses commonly in use in many metro areas - low energy consumption per passenger, off-vehicle power source. I'm not saying they're a solution, but just that you can't get to a good new solution by assuming it has to look like the current dominant option.

> Thinking like this is what prevents real innovation.

On the contrary, thinking like this is what spurs real innovation.

Look how many comments in this thread are about trivial changes like cutting the size of cars by half, or doubling fuel mileage, or cutting speeds in half. Likewise, think how many people assume you can make an appreciable change in global warming by recycling a bit more, driving a bit less, or buying the right brand of milk. What these all have in common is that they seem much easier to implement and, crucially, they make you feel like you're doing something.

In fact, we need major innovations. The point of my back-of-the-envelope argument isn't to assume that new solutions look like old ones. (I mean, I take it as obvious that, e.g., if we have ways to wireless beam energy to moving cars then this is an awesome solution and brilliantly defeats my argument.) The point of the argument is that you can't make minor changes; they have to be ambitious.

What I mainly took issue with was the conclusion: "Thus, alternative energy sources must approach the energy density of petroleum if they are to be competitive."

That seems utterly faulty to me, as I pointed out - there are multiple ways to solve the problem, none of which would necessarily require increasing the energy density of alternative power sources. All you have to do is reduce the amount of energy that needs to be stored in the vehicle, either by reducing use or required range between charges.

For what it's worth, there are already ways to beam energy to moving cars. http://www.extremetech.com/extreme/101581-inductive-car-char...

> If you want a vehicle that is large enough to hold a human and can push air out of the way at 60 mph

But do we really need to go 60 mph? Vehicles seem to be optimized for less-common use cases (e.g. 5 people in the car traveling 60 mph) instead of their more common uses (e.g. one person commuting at 30-40 mph). I, for one, would like to see smaller vehicles - NOT SmartCars and the like but an actual rethinking of the car that would be optimized for the single person commute.

They're called bicycles, motorcycles, buses, and trains. The first two give up protection from the elements, the second two give up independence. Keeping both the constraints nets you a single-person car-like device with say a 30hp motor - somewhat more efficient, but not enough to drive adoption. Gasoline (and energy in general) just isn't expensive enough for any of the alternatives to be taken seriously (infrastructure-wise) anywhere but dense urban areas.

My commute is mostly highway, at 65 Mph. The most common use case for my vehicle is thus very different from yours. Your vehicle would add extra time to my commute, and would not be useful for me in any situations where I am travelling long distance (120 km/h is the norm in Europe, that is about 75 Mph) I want to go faster, I don't want my trip to take even longer.

I suppose this depends on where you live, but going above 60mph is normal usage for me. In fact, a minimum speed limit of 45mph on freeways is fairly common (unless you can't due to traffic, of course).

On the other hand, I've never been able to drive above 45 mph on my normal commute, I'm only able to do so when I go on holidays.

Some cities are just not planned for cars (European cities like Vienna for example, where you cannot enter the downtown, or some South American cities like Montevideo).

I used to have a Maruti car and it was plenty for 99% of the time, and I'd buy a low-range electric/hydrogen/whatever car if it was cheap and offered me a better mileage equivalent.

Fuel economy can only improve by a factor of order unity (typically, less than 2) by changing speeds. And as I said, vehicle size is also incapable of reaching the orders of magnitude needed.

When visiting family in SC and FL I usually gag when I see people driving around (even running errands) in golf carts. Maybe I should give them a high-five instead.

My bad, poor choice of words. Of course it is not the fact that it is fueled by petroleum that contributes most to the five+ orders of magnitude in difference in power consumption.

I realize you're being slightly snarky...

If the chart on the website is to be believed, gasoline is second only to diesel in terms of energy density of viable fuel sources.

The power consumption of a vehicle has little to do with gasoline, though there is an important consideration for efficiency in terms of converting the fuel to linear motion (internal combustion engine and drivetrain).

Vehicles powered by any method are incredibly power consuming. Your average vehicle weighs more than 10x the weight of a single passenger, or in many cases 10x the weight of 2 pax.

Public transportation (impractical in the suburbs), or self-navigating vehicles (more practical) would seem to be a key in reducing the vehicle:occupant weight ratio and increasing overall efficiency.

Upvoted because of the reasons above. Bad choice of words on my part. Should have been "Vehicles (period) are incredibly power consuming".

But now you've got a period in the middle of your sentence.