Video: Gravity energy storage capacity to power sustainable aviation fuel projects
S. Himmelstein | November 03, 2021New projects planned to demonstrate sustainable aviation fuel production technology developed by DG Fuels LLC will be powered by gravity-based energy storage technology systems supplied by Energy Vault.
The gravity energy storage solution is based on the engineering fundamentals of pumped hydroelectric energy storage but uses composite blocks instead of water as the storage medium. These structures do not lose storage capacity over time and are lifted and lowered to capture potential energy in the elevation gain. 
Source: Energy VaultElectric power is then generated as the bricks are lowered.
Energy Vault will supply 1.6 GWh of energy storage for several DG Fuels projects, starting with a 500 MWh system for operations in Louisiana. These facilities will be used to advance a carbon conversion fuel production process that targets a 93% carbon conversion efficiency and reduces the amount of agricultural and timber waste feedstock and cost required to produce sustainable aviation fuel. The modified Fischer-Tropsch system also reduces carbon dioxide life cycle emissions and yields ASTM-certified direct replacement fuel with greater fuel density and lower particulate and nitrogen oxides emissions.
The gravity storage systems will provide green electricity in conjunction with photovoltaic solar capacity to match the demand load of water electrolysis systems for both green hydrogen and oxygen feedstock production.
I would hope the blocks on the bottom of the stack don't fracture from the stress. It would be a bad day if one or more stacks collapsed.
I assume that has been factored in.
The website claims low cost, eco-friendly materials (composite) whatever that is (concrete maybe?), but no where is there an estimate in cost per installed watt which is an industry standard measure of power generation facilities. There appears to be a demonstration unit being constructed in Switzerland. I wonder how the system compensates for high winds in positioning the blocks? Seismic issues with this Jenga system? What is the energy-in/energy-out
This quote from the website leaves me wondering: "Energy Vault delivers all of the sustainability and simplicity of pumped hydro storage with greater flexibility." Huh? This is WAY more complicated than pumped storage.