I realize this could be crazy talk, but is there a better way to store energy than batteries? Could you have a series of really heavy weights that rise when there's an excess of power and fall slowly to generate power when there's a need? You could even look at the weights as a gauge and if you need more energy, you hop on a bike or something. Of course gearing and mechanics would have to be perfect. Could it be as efficient as batteries? It would definitely save some toxic waste.

The problem with your hanging weight energy storage device is the weight required. To store a mere 12 hours' worth of 400 watt output (feel free to check my math here), assuming you have 5 meters of vertical space available, would require a weight of over 350,000 kilograms.

How about making the weight a cylinder and spinning it instead of raising it. These are known as flywheel energy storage devices are used in places like hospitals as power backups.

There's any number of ways to store energy, but most of them aren't as convenient as batteries. A flywheel is probably the refined version of what you're thinking of, William, since they allow you to get energy out relatively quickly compared to other mechanical sources.

I wouldn't know how to check the math, but 350,000 kgs sounds like a TON! Seriously, thanks for the input.

A better solution would be to have a braking mechanism that uses friction to turn a generator. (Like some hybrid vehicles do.) Instead of storing the excess energy, use the excess to generate electricity for direct consumption. Convergence is long overdue in the clean energy arena.

Superbad your math is good. The trick is, of course, to have a whole lot more than 5 meters of lift, and to have millions of tons of stuff available to lift, as is done in Pumped Storage Hydroelectric projects.

Good point. I remember reading in Georgetown, CO a couple years ago that they use off peak electricity to pump water from one lake to another higher altitude lake, then use that potential energy to generate electicity later during the day. Which is kind of silly, except that the power station has to run all night anyway, and the power would go to waste otherwise.

william: that's been done before: http://tinyurl.com/z2kws didn't make it to the new cenury very well, though... ;-)

The problem with flywheel storage is ... what happens when the flywheel loses structural integrity? They're very efficient because the air gets pumped out and magnetic bearings form a very low friction energy storage. However, you've still got a big heavy wheel rotating at thousands to hundred of thousands of RPM... (which is why most flywheel installations are underground and buried, so if it does lose integrity, the ground absorbs a lot of the energy and very little escapes out).