From pv magazine USA
The gravity-based energy storage tower developed by Energy Vault has reached commercialization, with the company signing an agreement with DG Fuels to supply 1.6 GWh of energy storage.
The tower will be charged with solar photovoltaic energy. The dispatched storage will support the creation of renewable hydrogen, biogenic based, synthetic aviation fuel, and diesel fuel.
The agreement is estimated to provide Energy Vault with $520 million in revenues across three projects. The first, a 500 MWh storage tower in Louisiana, is expected to commence in mid-2022. Additional projects are planned in British Columbia and Ohio.
Energy Vault’s design includes a six-armed crane tower that lifts composite blocks using an electric (solar-powered) motor. The lifted blocks are stacked, which creates potential energy. As the blocks are lowered, the energy is harvested and dispatched for use.
The tower is controlled by computer systems and machine vision software that orchestrate the charging and discharging cycles. A range of storage durations from two to 12 hours or longer is achievable, said the company.
Energy Vault said the tower’s design is based on the physics of pumped hydroelectric energy storage. However, as a solid “mobile mass,” the composite blocks do not lose storage capacity over time. The company said the tower has an 85% round-trip efficiency and a 35-year-plus technical life.
The composite blocks can be made cheaply, said the company, using excavated soil from the construction site, waste materials like mine tailings and coal ash, and even fiberglass from decommissioned wind turbines.
DG Fuels will deploy the storage systems to power its carbon conversion fuel process. The company said it is targeting a 93% carbon efficiency rate for its aviation fuel. It will also use the tower’s energy to power water electrolysis for both hydrogen and oxygen feedstock production.