To meet our future energy requirements, we need to rely on a huge range of alternative sources. Let's not forget the whimsical beginnings of our efforts to harness electricity (I'm referring to the kite of Benjamin Franklin). It's only fitting that electricity generation technologies come from left field.

Cars. Let's keep those cars on the road - because the weight of vehicles driving over metal plates could be used to generate electricity. (Perfect for lining public transport routes).

Tornados. Banish the image of tornado-chasers lugging HYminis - Louis Michaud is planning to create artificial vortices from hot air generated in power stations, and use them to drive turbines.

Cows. And in fact, farm animals in general. Although it lacks charm, manure is an energy powerhouse, releasing countless tons of natural methane. A study at the University of Texas has estimated that this manure could represent 100 billion kwH of electricity a year. And there's more: cows also generate methane in other ways that could yet be put to work. 

Food. It's no small potatoes in terms of energy. With a couple of electrodes and a little high school physics, you can generate a current. It's pitifully small, but it's there. Are food batteries round the corner? It's possible.

Rain. As National Geographic reports (video), the theory is simple - piezoelectric sensors convert impacts into electricity. Spread them over a wide enough surface, and the trickle of power could become a flood. Extraordinary potential.

Gray Water. Flush a toilet, run a faucet...turn a turbine and charge a battery. Hydroelectricity in the home.

Trees. In 2006, MagCap Engineering claimed to be generating a an electrical current directly from trees (Treehugger has the story). Could the same apply to plants in general? Street lighting powered by Nature - there's a bright idea.

Us. There must be hundreds of ways. Those piezoelectric sensors capturing rain energy? They could line our office floors and sidewalks, energizing our footsteps. Every mechanical task we personally undertake, from mowing the lawn to running on a treadmill, could generate electricity (maybe fed directly into our own Personal Batteries). And electricity from trees? That's because living things generate a bioelectric field. Same applies to every one of us - we're aglow with energy. It's sounding a bit Matrix-y, isn't it?

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