i had this thought about making my house more energy efficient, and better for the environment etc...

solar panels on the roof. ok, not that original i hear you say. even though i want to hook it up to the grid, apparently you can sell energy to the electricity firms as well.

then i was thinking about storing it too. only batteries aren't too pleasant on the environment either. so i had a little think. what do batteries do? they store energy. so how about instead of charging up batteries, i use the electricity i generate to lift a big weight off the ground. during the night when i need electricity i let the weight come down and run a generator. only the weight needs to be filled with something heavy, so i thought i'd fill it up with batteries....