Architecture and engineering firm Skidmore, Owings & Merrill (SOM) and energy-storage technology firm Energy Vault have announced a partnership to further develop gravity-based energy storage.

As a a leading designer of numerous supertall towers around the world, SOM sees a natural fit with Energy Vault's vertical-oriented energy-storage solutions, which use the inverters and turbine-turning principles of pumped hydroelectric power and recovered power from rapidly lowering weights. Excess potential energy comes from the basic equation of potential energy equals gravity times mass times height. 

Energy Vault's current demonstration projects in Italy and China can hoist and hold at height 30-ton masses which, when rapidly lowered, turn that potential energy into kinetic energy. Energy Vault current's G-VAULT gravity-based energy storage systems leverage renewable energy generation, including wind and solar, to power the lifting of heavy composite blocks to store energy. Lowering the blocks turns turbines to generate electricity, which can be produced when needed. 

The systems being developed with SOM will use the same approach, but also involve the rapid transfer of water to turn the turbines for finer control.

SOM will be the exclusive architect and structural engineer for the next generation of fixed frames and deployable structures for all new Energy Vault gravity energy storage systems (GESS). SOM will work on a new family of GESS for Energy Vault that include:

• EVu: A technology for superstructure tower design that integrates a GESS into hollow spaces within tall buildings over 300 m, and up to 1,000 m. These GESS structures will have the capacity to reach multi-GWh of gravity-based energy storage to power not only the building itself but also adjacent buildings. The companies say the carbon payback of this type of structure could be achieved within a time frame of three to four years.
  
  
• EVc: Large-scale pumped hydro energy storage systems that will be integrated within tall buildings using a modular, water-based system. Primarily a standalone GESS, EVc designs could also be integrated into tall buildings that form the basis of the EVu design. SOM says a cylindrical shape would be an optimized design for the structure, to better withstand wind and seismic events.
  
  
• EVy: Uses Energy Vault’s existing gravity-based energy storage technology on pre-existing natural slopes and topography to store energy with minimal environmental impact and capital expenditure by reducing or eliminating the need for more complex manmade structures.
   
• EV0: A pumped hydro energy storage system without the issues related to concrete production or added disruption to existing ecosystems. These modular systems will leverage a fabric vessel (a “water tree”) to store water in manufactured modules that can be deployed while leveraging proven pump-turbines and penstock designs for existing pumped hydro systems such as the sites of existing hydroelectric dams or similar locations.

"The partnership we have agreed to is one wherein we would be their architect and engineer for these new structures," says Adam Semel, SOM managing partner in Chicago. He adds that SOM is also willing to partner with other firms it identifies in parts of the world where it doesn't have an office on energy storage projects as it does on its building and infrastructure projects. 

For the composite block gravity-based systems, Energy Vault says it plans to use only wind and solar to raise the blocks and claims it will have over 80% roundtrip efficiency. Energy Vault’s software will control, manage and optimize assets such as the blocks and the motors and pulleys that hoist them. 

William Baker, consulting partner at SOM and a structural engineering innovator says that the availability of renewable energy, particularly solar, but also wind make such systems viable as storage for the grid.

"You have a storage facility up high in the sky and you have another storage facility down at the base, and you're moving the weights when the sun's shining and you have more solar energy than you need."

Baker says delivering the energy when it's not available from solar or wind generation will help fill off-peak gaps to run generators and feed microgrids.

Many of the EVu structures would have to be dedicated superstructures, solely designed to provide energy to microgrids and other nearby buildings as needed, Baker notes. But the technology could also be integrated in a building such as an office or residential tower.

Semel says SOM sees promise in Energy Vault's development of the technology.

"I think they are going to continue to evolve the technology to become more and more efficient. The commitment ... it's to unlock the potential of gravity, to store energy, renewable energy, at scale." he said.

He adds that SOM is considering using the systems in their own tall building projects.

"We're having some of those conversations now, it just has to be the right context, the right place and the right client. We are talking to some of them now about these ideas," he said.