Due to the explosive growth of wind turbines, essentially a periodic source of power, people are trying to find new ways of storing energy at lower costs. I have two ideas. 1. A collection of massive springs, which stores as strain energy. 2. A fluid stored atop a hill, which stores as gravitational potential energy. For #2, this is already a fairly well-known storage mechanism (at least discussed). The fact is, you have to find a large reservoir, if water is the fluid of choice, and a lot of space to put it in at both elevations. So, I was thinking it should be possible to use mercury as the fluid, which will either decrease the required amount of fluid by 13 times, or decrease the height req'd by 13 times, or a product of the two. That means for any leak-proof design for water energy storage, you can store 169 times more energy if mercury was used instead. Of course there are environmental concerns with using so much mercury so I'd recommend it over a deep mine shaft such that in case a spill/flood ever occurs all the mercury will sit deep inside the crust where it should belong. But this might be impractical too, due to the cost of mercury. But who knows - with so much pollution going on people might be able to extract mercury from pollutants. I'm debating myself whether #1 is practical. After all, if the springs are to be aligned vertically, why not just substitute them for masses in a potential energy system? This is something which I recently reversed my mind on, thinking that yes, you can store megawatt-hours of electricity in springs. Before that, for the previous three years or so, I thought it was infeasible. And even before that, when I first thought of the idea, I thought it was feasible. So now I've switched my mind twice. In posts which I hope to post soon, I will at least attempt to demonstrate why a spring system might work.