According to Spectrum, several companies are poised to make a splash storing energy with gravity. That sounds fancy and high tech at first, but is it, really? Sure, we usually think of energy storage as some sort of battery, but there are many energy storage systems that use water falling, for example, which is almost what this new technology is all about. Almost, since instead of water these new systems move around multi-ton blocks.
The idea itself is nothing new. You probably learned in high school that you have kinetic energy when a rock rolls down a hill, but a rock sitting on a mountain immobile has potential energy. These systems use the same idea. Moving the “rock” up stores energy and letting it fall releases the same energy. The big difference between the systems is what “up” means.
For Swiss company Energy Vault, the 35 metric ton bricks rise into the air manipulated by towers that look like alien construction cranes. To store energy, the crane builds a tower of bricks around itself. When the bricks return to the ground, they form a lower ring around the tower.
Another company, Scotland-based Gravitricity, uses weights up to 5,000 metric tons and moves them up and down very deep mine shafts, an approach shared by several other companies in this field. Some of the systems use the mechanical motion of the weight falling while others use the weight as a piston to drive water through a pretty ordinary generator.
Why not use batteries? According to the post, Energy Vault claims that blocks made of dirt, waste, and polymer are environmentally friendly compared to batteries. The blocks don’t wear out much, either, so operating costs are low since there’s not much to replace frequently as is the case of batteries.
The scale of the weights is hard to imagine. Another company, Gravity Power, claims they could deliver 400 megawatts for 16 hours using an 8 million metric ton piston. There’s no word on how long it takes to bring that piston back to the charged position after the 16 hours, though. A Boeing 757-200, for example, weighs about 100 tons when loaded with fuel and passengers. So imagine 80,000 giant airplanes melted down. It makes Energy Vault’s 35-ton weights seem much more reasonable.
Keep in mind, these systems don’t generate electricity. They store it, so there will be some loss. However, the principle of these is straightforward, the only complication is the scale. We wondered if anyone has used some sort of system like this on a small scale on a project that would have normally used rechargeable batteries? Sounds like a weekend project and if you do it, be sure to let us know.