To begin, here are links to a couple of interesting articles. The first is the 2005 Energy Flow diagram from the Department of Energy; the second is a 2006 Powerpoint by Dr. Tim Fitzsimmons that contains not only the first diagram cited but several others of interest.
First off, the USA consumes about 100 quadrillion BTUs of energy each year. We produce about a fifth of the world's energy, but as net energy importers we consume about a quarter. This energy comes in three principle flavors: fossil fuels (coal, natural gas, and petroleum provide about 85% of our total energy), nuclear energy, and renewable sources (mostly hydroelectric). Energy imports into the USA - about a third of our total consumption - consist mostly of petroluem products. This energy feeds four sectors of the economy: residential, commercial, industrial, and transportation. However, it does not do so in equal proportions.
Nuclear, renewable energy sources, and coal are used almost entirely to produce electricity. About two-thirds of the nation's electricity is consumed by the residential sector; the other one-third by industry. Natural gas is consumed in more or less equal parts by electrical production, residential use, and industry. Petroleum products - forty percent of our energy - are consumed almost entirely by the transportation sector of the economy.
About 70% of the energy consumed for electrical consumption is lost, mostly in the form of waste heat. The percent lost in transportation is even greater at about 80%. Wth the steadily increasing (and occasionally volatile) price of crude oil, it's no wonder that there's so much excitement about hybrid electric vehicles and Bruce Crowler's six-stroke engine, both of which use existing fuel more efficiently.
But there's also excitement about wind farms and solar energy and ethanol and hydrogen. Southern Man will now explain why you should not be overly enamoured of these and will explain what you should actually be rooting for.
Wind farms and solar energy contribute a small but growing portion of our renewable energy. The upsides are little pollution (mostly from manufacturing) and noting that the wind will blow and the sun will shine whether we harness that energy or not. Southern Man is a proponent of small-scale solar power as an energy supplement to a home or small office building, but electrical solar panels will have to get a bit more efficient before such a system will actually break even. If you're handy, a homebrew solar hot water system (to supplement your existing electric or natural-gas water heater) will easily pay for itself in little time. But while useful, wind farms and solar electricity are not the big answers.
Ethanol is absolutely the wrong way to go. Ethanol blends like E85 are inefficient - your vehicle's mileage will drop from 25% to 40% when you burn it - but usually isn't any less expensive than regular unleaded (which is usually E15 - about 15% ethanol). The pollution problems are about the same. And while you can just about break even with ethanol produced from sugar cane (as does Brazil and other South American countries) we here in the USA have to do with corn, which does not yield the product easily. And world prices for both sugar cane (and sugar beets and other sugary plants) and corn are already rising due to the increasing consumption of these food crops by the energy sector. Which means that the prices of foods that depend on corn (like hamburger, which comes from corn-fed cattle) are also on on the increase. The choice isn't guns or butter; it's cars or butter. Do you want to drive, or do you want to eat?
The future of science fiction has always been a hydrogen-powered economy. Well, the science-fiction dream usually involves using that hydrogen to power nuclear fusion reactors, but we'll take it any way we can get it. The universe is, after all, three-quarters hydrogen, right? We're practically swimming in fuel! Why not use it?
Well, the problem is that the hydrogen available to us, being fairly reactive stuff, has already done reacted with something else and is bound up in a tight little molocule somewhere, and energy must be spent to extract it again. And as it turns out, the most efficient way to do this is to start with - hydrocarbons.
Yep. Fossil fuel.
What hydrogen proponents don't tell you is that if we could magically convert all of our economy to a hydrogen base tomorrow, our need for imported hydrocarbons would triple overnight. And the process to release that hydrogen produces just as much pollution (including CO2) as burning the hydrocarbons directly. And the net energy yield of the hydrogen produced is less than if you just burned the hydrocarbon directly as fuel. And hydrogen is fairly heavy, as fuels go. It's pretty hard to beat the energy density of gasoline.
Some day - some day - the technology will exist to extract hydrogen from sea water in a practical manner. This would be a good thing; for example, some of the waste heat in conventional power plants could be harnessed to produce hydrogen. But that technology ain't here yet, and it doesn't look like it will be anytime soon.
So, you ask, what are the other options?
Southern Man sez - better batteries and nuclear energy.
The Achilles Heel of transportation in general is that you have to carry your engine and your fuel and your pollution controls around with you, and that makes for a heavy vehicle. Your engine is heavy - it has to be large enough to provide needed torque for stop-and-go driving in town, but that's way larger than optimum for highway cruising. Your fuel is heavy - which is why we use gasoline, which packs a lot of energy into each kilogram of fuel. Your pollution controls are heavy - and it's remarkable that we are able to handle almost all of a car's pollution with only about a hundred pounds of equipment. The problem with electric transportation is that the energy density of batteries just plain sucks. You just can't store much energy per kilogram in your batteries. And they don't last long without a recharge. How often do you curse at your big, heavy battery when it won't run your laptop for more than a few hours? Now move that problem to your car. Practical all-electric vehicles are still decades away.
But there is hope. Gasoline-electric hybrids try to get the best of both worlds with a small (and thus efficient) gasoline engine for highway cruising, and a battery-powered electric motor for city driving. The increasing popularity of hybrids is pushing battery technology in the right direction. And as batteries improve, cars can rely more and more on electric drive rather than fossil-fuel engines. The day may come when you plug your car into the charger at night (and that charger may itself be based on a rooftop solar panel) and rarely run the gasoline motor at all.
And that leads to a second benefit. More than a third of our energy infrastructure is devoted to producing electricity - but the transportation sector can't use it 'cause most transportation is powered by petroleum-fueled motors. Improvement in hybrids and the inevitable production of all-electric cars means that the transportation sector can - finally - start to make use of energy infrastructure other than petroleum. For example, it's been said that we're the Saudi Arabia of coal. The USA has more coal than it knows what to do with. We already use it to make electricity - why not use it to make electricity that runs our cars?
And the third benefit is that it gives us a reason to increase our reliance on nuclear power. Southern Man is a big fan of nuke plants - in his opinion they are far safer and produce much less pollution than a coal-fired plant - but building more nuke plants today doesn't really decrease our reliance on energy imports. But as the transportation sector begins to tap into our existing electrical infrastructure, this will change. Southern Man sees a future where most of our transportation energy needs come from electricity and most of that electricity is produced by nuclear power (on the largest scales) and solar power (on smaller scales, like the rooftop car-battery recharger described above).
Nuclear power has languished in this country for a number of reasons, but the most important one by far is that the cost of fossil fuels remained unexpectedly low for much longer than anyone anticipated. You may be surprised to hear Southern Man say that in this painful era of $3-per-gallon gasoline, but the adjusted price of gasoline today is not much different than it was forty years ago (and part of our pain today is that throughout the 1990s oil was really cheap - Southern Man remembers one summer when the pump price of gas fell (briefly) to 59 cents a gallon after years of sitting at $1.09 or so). Believe me, Southern Man feels your pain - his old SUV gets 18 MPH and consumes the cost of dinner and drinks for two at Outback with every fillup. But he also believes that the future is bright.
In summary: think about supplementing your own home with solar water heating, support research into improved battery technology for hybrids (and laptops and cell phones!) and the upcoming generation of all-electric vehicles, and vote in favor of building as many new nuclear power plants as possible.