Throughout history, towering structures have symbolized the power of empires, rulers, religions, and corporations. Today, the trend of erecting tall buildings continues to rise, but skyscrapers may soon serve a new function: storing renewable energy.
One of the significant challenges in transitioning to a power grid dominated by clean energy is dealing with the intermittency of renewable sources. Solar panels and wind turbines can be unreliable—clouds can obscure the sun when solar energy is needed, and calm winds can halt turbine operations. Conversely, there are times when these sources generate excess energy beyond what is required.
To balance energy production and consumption, effective storage solutions are crucial. A mix of technologies, including various types of batteries and other storage methods, will likely be necessary to enhance energy storage capacity.
Enter the concept of battery skyscrapers. At the end of May, Skidmore, Owings & Merrill (SOM), renowned for designing some of the world’s tallest buildings, partnered with Energy Vault to explore new gravity-based energy storage solutions.
The proposed design involves a skyscraper equipped with a motor powered by electricity from the grid to lift massive blocks when energy demand is low. These blocks would store energy as “potential” energy. When energy demand increases, the blocks would be lowered, releasing stored energy that would be converted back into electricity.
SOM has a history of designing iconic tall buildings, including New York’s One World Trade Center, Chicago’s Willis Tower (formerly Sears Tower), and the Burj Khalifa in Dubai, which stands over 828 meters (2,700 feet) tall. Bill Baker, a consulting partner at SOM and structural engineer for the Burj Khalifa, remarked, “Here’s an opportunity to take this expertise … and use it for energy storage, enabling us to wean ourselves [off] fossil fuels.”
Achieving net zero emissions by 2050 necessitates scaling up grid-scale storage technologies that can store and deploy energy when needed, according to the International Energy Agency. Lithium-ion batteries, popular in electric vehicles, are insufficient on their own for this task, as they cannot store energy for extended periods.
While lithium-ion batteries are effective for short-term energy shifts, such as moving energy from sunny afternoons to evening peak times, longer-term storage solutions are required. Pumped storage hydropower, already widely utilized, involves pumping water from a lower to a higher reservoir during off-peak hours and releasing it through a turbine during peak demand. However, this method needs hilly terrain and significant space.
SOM and Energy Vault’s proposed superstructure tower, ranging from 300 to 1,000 meters (985 to 3,300 feet) in height, would feature hollowed-out elevator-like shafts for moving the blocks. These designs would leave space for residential and commercial tenants. Additionally, the companies are considering integrating pumped storage hydropower into skyscrapers, using water instead of blocks.
Ultimately, such skyscrapers could store multi-gigawatt-hours of energy, sufficient to power multiple buildings, as noted by Energy Vault CEO Robert Piconi. However, experts have questioned the economic viability of skyscraper batteries due to the space required for energy storage and the structural modifications needed to support the additional weight.
Despite these concerns, Energy Vault and SOM are confident in the commercial feasibility of their solutions. Energy Vault has completed a project in China, which it claims is the world’s first commercial-scale, non-pumped hydro gravitational energy storage system. This 150-meter-tall (492 feet) building has a storage capacity of 100 megawatt-hours and is designed solely for energy storage without space for tenants.
The use of renewable energy in skyscrapers could help mitigate the carbon footprint of tall buildings. Currently, the buildings and construction sector account for nearly 40% of global greenhouse gas emissions. Efforts are underway to address this issue through better insulation and alternative, less carbon-intensive materials, such as timber.
Some buildings are also incorporating greenery. Italian architect Stefano Boeri has designed towers adorned with trees and shrubs in Milan, and a similar concept is planned for Dubai.
As buildings continue to grow taller to accommodate rapid urbanization and limited space, the potential for gravity-energy storage structures increases. According to Daniel Safarik of the Council on Tall Buildings and Urban Habitat, 235 buildings taller than 200 meters (656 feet) were built globally between 1900 and 1999. Last year alone saw the construction of 179 such buildings.
For gravity-energy storage structures, height is advantageous. A very tall gravity storage structure could offset its embodied carbon, from construction and materials, within two to four years. “If you’re going high in a superstructure anyway, we’re just piggybacking on that,” said Piconi.
SOM and Energy Vault are now seeking development partners to bring their designs to life. Piconi believes SOM’s reputation in the tall buildings sector will be instrumental in overcoming the challenge of constructing the first such skyscraper.
