Energy Vault to build grid-level, gravity-fed battery from a tower of concrete blocks
Meeting our growing energy demands without continuing to destroy the planet might be one of the biggest challenges of our time, and it calls for some pretty creative solutions. Swiss company Energy Vault has just launched an innovative new system that stores potential energy in a huge tower of concrete blocks, which can be "dropped" by a crane to harvest the kinetic energy.
With a focus on storing energy from intermittent renewable sources such as wind and solar, the Energy Vault takes advantage of some fundamental physics. If you coil a spring, for example, you're packing it with potential energy – as soon as you let it go, that energy is unleashed as the spring extends itself back out. This new system scales that up to the grid level.
In this case, that potential energy is stored inside huge concrete blocks. To charge up this skyscraper-sized "battery," a six-armed crane lifts the blocks off the ground and stacks them up around its base, creating a tower. To discharge, the crane simply lower the blocks back to the ground, converting the kinetic energy from the descent into electricity. Proprietary algorithms calibrate and control the charge and discharge cycles to make it as efficient as possible.
According to the company, the general concept was inspired by pumped hydro plants, which also tap into gravity. In those systems, power is generated by water rushing downhill through turbines, and during times of low energy demand, that water is pumped back up to the higher reservoir to reset the energy potential.
The company says each tower can be built to have a capacity of up to 35 MWh and 4 MW peak power based on their size, with the modularity of the system allowing capacity to be increased by building more towers. While it might seem big and cumbersome, the crane can be generating power in as little as 2.9 seconds, and has a roundtrip energy efficiency of about 90 percent. And unlike chemical storage systems, once those bricks are stacked up, that energy won't "leak" out or degrade.
That said, Energy Vault claims that the concrete blocks don't degrade over time, but to us it seems like years of exposure to the elements could slowly wear away at them. Still, the company says the system should have a lifetime of 30 to 40 years.
Another possible argument against the system is that concrete is one of the most environmentally damaging materials to produce, so building the components in the first place could leave a big footprint. But Energy Vault says the blocks are made out of concrete debris that would normally be headed for landfill, reducing both cost and waste materials. It also says it will look at using various concrete-based composite materials to suit different regions around the world.
The ultimate goal of the system is to store energy produced by renewable sources like wind and solar, keeping the lights on even when the wind isn't blowing or the Sun isn't shining. It should be able to do so at a lower cost-per-kilowatt hour than other storage systems like Tesla's huge Li-ion battery in Australia, or the brine4power redox flow battery in Germany.
The first 35-MWh Energy Vault system is due to be deployed in India for The Tata Power Company in 2019.
Source: Energy Vault