22 August

Storing electricity in gravity

Kottke brings news of a novel way to store electricity for later use using cranes and concrete blocks. During times of excess solar/hydro/wind generation the electric powered crane lifts these huge weights as high as it can. Then, when there's a lull in energy the crane drops the weights, spinning turbines which generate electricity for the grid. What's striking is they claim to be recovering 85% of the electricity used to lift the blocks, compared with 90% when it's stored in lithium batteries. I always assumed these systems lost much more through noise, friction, etc, so that's good to know.

Of course this has been around for ages. The UK national grid uses reservoirs in Wales to store energy for peak times, traditionally when soap operas finish and everyone puts the kettle on at once.

There's also the train-full-of-rocks approach, where a train full of rocks is slowly driven up a hill and then, when the energy is needed, rolls back down.

But reservoirs and hills take up a lot of space. The crane system really caught my eye because it doesn't have a large footprint. You simply need to lift something up. And we have plenty of structures that can house a up-lifty thing. Imagine if every building over 3 stories had a shaft containing a dense block of metal. On top of the building is a solar array and/or wind turbine which, if its energy isn't being used, lifts the block. And then, at night or when the wind drops, the block starts its descent.

This sort of micro-conservation of energy has a lot of potential. Cities absorbed insane amounts of heat this summer which just sat there in the concrete making everyone uncomfortable. Couldn't that energy be captured and stored in a kinetic system?

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