Energy Vault’s breakthrough technology was inspired by pumped hydro plants that rely on gravity and the vertical movement of water to store and discharge electricity. Energy Vault’s innovation created the only gravity-based storage system that does not rely on land topography or geology, and thus can be built almost anywhere either co-located with solar or wind plants, or simply connected to the grid to support dispatchability and grid stability.
Based on the same fundamentals of physics, specifically potential energy, Energy Vault applied innovative material science to replace the water with proprietary cement/polymer-based composite bricks that can be made of ultra-low-cost materials: soil, mine tailings, coal ash, incinerated city waste, and other remediation materials. The bricks, each weighing 35-metric tons, are manufactured with these materials, designed to have a specific gravity at least twice that of water and engineered to achieve significant compressive strength with virtually unlimited life. Energy Vault’s “greener than green” approach stores dispatchable renewable energy and utilizes material that would otherwise be destined for landfills at a very high financial and environmental cost.
The specially designed Energy Vault system lifts the bricks with conventional hoist machinery that is much more efficient than current hydro plant pumps or turbines. This results in a round trip efficiency of more than 80% with minimal auxiliary consumption -- compared to chemical batteries which require significant thermal management to extend their otherwise short cycle life. This efficiency combined with lack of degradation in storage capacity over time is the key to reduce the levelized cost of storage by ~70% versus current competing technologies.
Key to the design is leveraging existing trillion-dollar industries to accelerate scalability and time to market while innovating to create 15 patents in material science, structural design and AI/software. The system’s custom designed 6-armed crane is operated with proprietary algorithms and machine vision to fully automate the process of sequencing and orchestrating the movement and positioning of the bricks. The control software manages induced sway in milli-second time while synchronizing the motion of the arms to deliver or absorb a constant power to the grid. With the innovative application of variable frequency drives and permanent synchronous motors, the actual power can be controlled continuously from 10-100% load without compromising efficiency.