Gravity Battery

The transition from fossil fuels to renewable energy is slow. Way too slow. Apart from spoiled suburbans complaining about how wind farms spoil their view, there's a major technological barrier slowing down this much needed transition: how do we store this renewable energy in a cost-efficient and environmentally friendly manner?

The problem with renewable energy, like solar or wind, is that their power generation isn't constant and is heavily depending on circumstances. This is most obvious with solar power, as no energy is generated at all during the night, while during the day en excess of power is produced. To guarantee a steady flow of power during all circumstances we need a way to store excess power that we can use during times when no power, or too little power, is generated. The chemical batteries we use now fall short in a couple of ways. If we want to use renewable energy to spare the environment, chemical batteries are antithetical to that goal, as they produce chemical waste and use resources that are harvested in an environmentally unfriendly manner. Also, these batteries discharge rapidly when stored in places where it's too hot or too cold.

This is where the gravity battery enters the picture. These have existed since 1907, when the first gravity based pumped-storage hydroelectricity (PSH) system was developed in Switzerland. The idea is as simple as it is brilliant: use excess energy to pump water into a reservoir located on top of a mountain to store gravitational energy there. When you need the stored energy, you just let the water flow back down to generate energy in the same way as with a dam, river or waterfall. This works a treat, en modern versions of this PSH system, of which there are a lot, operate at 75 percent efficiency. There's a problem though: this system can only work in areas where there are mountains and lots of water. It's no coincidence this originated in Switzerland... So, what do we do in the desert? There's loads of excess solar energy to be harvested there. Or in my country, The Netherlands, where there's a lot of wind and water, but no mountains at all?

Well, that's what the below linked video is all about. And again the idea is as simple as it is brilliant. The solution discussed consists of an Energy Management System, the software operating it all, a bunch of software-driven fully automated cranes, and a collection of heavy bricks. The system works by using excess energy to lift 30 ton bricks on a platform and on top of each other, and then, when the energy is needed, lowering them slowly back to the ground while generating gravitational energy:

Energy Vault gravity-based solutions employ a proprietary mechanical process and energy management system to store and discharge electricity. When renewable energy generation is high, EVRC uses that energy to raise 30 ton bricks to an elevated position. Potential energy is stored in the elevation gain of the brick. When energy is needed, EVRC releases kinetic energy back to the grid via controlled lowering of the bricks under gravitational force.
_{source: Energy Vault}

The stated goal of Energy Vault is to accelerate the global transition to renewable energy, which is something I can stand behind all the way. They even mention that they use eco-friendly materials with the ability to integrate waste materials for beneficial re-use. The bricks, for example, can be made from recycled heavy materials. The video also discusses another start-up that uses the same principles, but instead of cranes, they use deep abandoned mine-shafts. All in all a promising development, so please watch the video if you're interested to learn more.

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