The architecture firm that designed the world's tallest building is considering ways to build skyscrapers that can store energy using gravity.
Skidmore, Owings & Merrill LLP has developed a series of prototype designs that use electric motors to elevate massive blocks, creating potential energy that can be converted into electricity when the blocks are lowered. The designs are based on technology developed by partner Energy Vault Holdings Inc. as an alternative to lithium-ion batteries and other types of chemical cells. They are seeking developer partners interested in offsetting greenhouse gas pollution from buildings, which the United Nations estimates are responsible for almost 40 per cent of global emissions.
The concept is similar to widely used pumped hydroelectric plants. Energy Vault completed its first major project this month near Shanghai, a stand-alone storage system that can supply as much as 25 megawatts of power for four hours. Other companies are testing new types of gravity storage systems, including ones using abandoned oil wells and mines.
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Building owners and designers have a growing number of tools to limit carbon emissions from day-to-day operations, from better insulation to heat pumps. However, there are no substitutes for steel and concrete that are critical components of modern buildings, both of which are major sources of carbon emissions. There are efforts to decarbonize those materials, but they remain far from reaching a meaningful scale. For building owners looking to zero out emissions, turning a skyscraper into a massive battery is one avenue, according to Bill Baker, a consulting partner at Chicago-based SOM.
SOM has created four storage system prototypes based on this concept. Three are standalone systems that use either heavy blocks or water, with two built into hillsides and a third that's a tall, cylindrical tower. The last is intended for urban areas, a towering skyscraper that could include residential, retail and office spaces. Energy Vault's Shanghai project is about 150 meters (490 feet) high, but SOM's skyscraper batteries may be much higher, starting at 300 meters.
Tall buildings are SOM's specialty. Baker was the lead designer for the Burj Khalifa, the 828-meter tower in Dubai that's the world's tallest building, and he sees significant potential for incorporating energy storage into skyscrapers. That's because the higher the weights are lifted when there's a surplus of cheap electricity, the more potential energy they will hold that can be released when electricity is needed.
"If I store it twice as high, twice the energy," said Baker. "High is better."
Energy Vault's current systems can provide energy for about five to 10 cents a kilowatt-hour, according to Robert Piconi, the Westlake Village, California-based company's chief executive officer. That's cheaper than lithium-ion batteries, which come in at about 13.5 cents, according to BloombergNEF. Going higher will shift the economics significantly, and he said the goal is to get that figure down to less than 5 cents, the levelized cost over a project's lifetime.
Once a building gets above about 200 meters, a gravity-storage system could supply more than enough power to cover its operations. That's when building operators can start to offset the carbon footprint of construction materials, with some of SOM's designs expected to see that payback in two to four years.
"Instead of buildings being carbon emitters, think about a carbon payback," Piconi said. The companies are talking to potential developer partners in the Middle East, and if things proceed smoothly, Piconi could see a project begin construction in early 2026.
That date may be optimistic, though. Energy Vault has faced hurdles, including fundamentally redesigning its gravity system and offering chemical battery storage systems to customers as a way to generate revenue now. While completing the Shanghai project was an important milestone, and partners in that venture are now planning additional storage systems in China, Energy Vault's shares have tumbled more than 85% since it went public in 2022 in a deal with a special purpose acquisition company.
The idea of adding storage to a major skyscraper is fundamentally sound, according to Thomas Boyes, an analyst with investment bank TD Cowen. Planning, permitting and financing for these kinds of developments take years, however, and there's only a limited number of so-called supertall projects that exceed 300 meters. Boyes said it's more likely that mixed-use towers with Energy Vault technology could appear sometime in the 2030s.
"It makes sense on paper," he said. "There are underlying reasons why buildings will want this technology, but it's a market that takes a long time."
Storage technology built into tall structures would significantly change the energy economics of the construction industry, said Adam Semel, a managing partner at SOM.
"Gravity energy storage has a huge role to play in the economy of the future," Semel said. "We want to get to work on some actual buildings."
