technology

cross-posted from: https://lemmygrad.ml/post/9551599

A western video that doesn't demonize China? Hell yes.

If you didn't know about gravity batteries, they are a very efficient form of energy storage that work so simply on paper, you have to wonder why we didn't think of it sooner.

Basically you build a huge weight (24 tons for starters), which can be made of sand, cement, or anything sufficiently heavy you can find.

But how do you get electricity out of a huge slab of concrete, you ask? You simply raise it up into the air. When the grid is producing more electricity than it needs, cranes raise this block of weight up in the air using the excess energy. Then, when the grid is consuming too much energy, the block is released and allowed to drop back down, turning a turbine in the process and producing electricity.

It's basically undoing what you did, or reversing the process. A lot of energy storage works on that principle. You let the block fall down naturally with gravity at the same speed you raised it up. It's like the dynamo on your childhood bike.

And the energy output is huge. First the stored (potential) energy inside the concrete block is 100% efficient: it will use as much energy to drop this block than you used to get it up in the air. However, because of inefficiencies in the electricity conversion process, the actual conversion rate is around 80% (if I understood the video correctly). But potentially, you could make this system output just as much electricity as you put into it.

There is also no leakage like in dams, which operate on the same principle (pump water into a reservoir when consumption low, let it fall into a lower reservoir when consumption high, it hits a turbine when falling down and moves it). Dam water evaporates, and li-ion electricity dissipates naturally. But a block of concrete will stay in place when you raise it up because gravity is a constant. It will not move an inch.

Building such a battery is not super cheap yet: China invested over 1 billion USD for their grid. However, once it's built the battery can last well over 35 years and most of all, you can build those everywhere in the world because all they need is a weight and vertical space. Conversely getting lithium for li-ion battery farms is not available to everyone, and hydroelectric power (which uses the same gravity principle and can also store energy using a pump to pump the water back upstream) is even more geographically dependent. But everyone has rocks, sand and soil to make 24 ton blocks.

The cost of producing electricity with this type of battery is estimated to be 5 cents per watt, compared to over 12-17 cents per watt for a hydro dam. It has large upfront costs, but the return is some of the best you can get.

Moreover, I think it's also important to note that we see China is relying on all types of energy storage, building a resilient grid. While they are the only country actually building gravity storage at scale (in the west this is still just prototypes here and there), they are also making li-ion farms, hydro dams, and what have you. They don't rely on a single method which would lead to a single point of failure.