If we can trap the sun in solar panels and the wind in turbines, why not freeze time - quite literally - with ice? In the sweltering summers of New York City, a new kind of battery does just that.
A quiet revolution is underway in the basements and rooftops of New York City’s commercial towers. As the summer heat begins to strain the city’s aging power grid, a new kind of battery—one that stores cold instead of electricity—is making its mark.
These so-called “ice batteries” are changing the way buildings stay cool and are rapidly becoming a go-to technology for developers seeking to cut energy bills, lower emissions, and reduce blackout risks. At the forefront of this transformation stands a small company from Kibbutz Shdema in Israel: Nostromo Energy.
At Eleven Madison, one of Manhattan’s landmark office towers, hundreds of thousands of pounds of ice are produced every night four floors underground. The ice is not meant for drinks—it is used to cool the building the following day.
By freezing water at night when electricity is cheap and abundant, and then circulating its chill during the day when demand and prices spike, the building avoids tapping into the grid when it’s under the most pressure. According to Trane Technologies, which installed the system, the savings can reach up to 40% on cooling costs.
This strategy—shifting energy use from peak to off-peak hours—is not new. But until recently, it was largely confined to industrial-scale operations or research labs. Now, a growing number of commercial buildings, hospitals, hotels, and even municipal facilities are adopting thermal storage systems. At the center of this surge is Nostromo Energy, which has become one of the leading names in ice-based thermal storage.
Nostromo was founded by Yaron Ben Nun, an Israeli designer, filmmaker, and former fighter pilot with a passion for clean energy. The son of former Israeli Air Force commander Avihu Ben Nun, he came to energy storage after a decade of environmental advocacy and industrial design. Frustrated by the lack of clean and scalable cooling storage technologies, Ben Nun and his engineering team developed a new system: the ״IceBrick״.
Each IceBrick unit contains hundreds of capsules filled with water, which freezes during hours of low electricity demand. Later, the stored ice cools the building’s central HVAC system without consuming electricity during peak hours.
Unique design, eco-friendly power
The system’s modular design—described by the company as “Lego-like”—allows it to be installed on rooftops, inside mechanical rooms, or along exterior walls in both horizontal and vertical arrangements, adapting to even the tightest urban spaces.
Unlike lithium-ion batteries, the IceBrick system is entirely water-based, non-toxic, and non-flammable. Water also doesn’t degrade over time. “In theory, you can freeze and thaw water forever,” noted Allison Mahvi, a mechanical engineering professor at the University of Wisconsin.
The only components subject to wear are the pumps and valves, which can last decades. Technically speaking, it takes 80 times more energy to freeze a gram of water than to heat it by one degree Celsius—a fact that gives ice batteries tremendous energy density for cooling applications.
Since launching its operations in the U.S., Nostromo has secured high-profile partnerships. Its technology is already operating at two of California’s most iconic hotels—the Beverly Hilton and Waldorf Astoria—as part of a shared 1.4 MWh system that has been credited with reducing carbon emissions by over 200 metric tons annually.
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A broader deployment is underway in California, where the company is in advanced negotiations for a \$189 million loan from the U.S. Department of Energy to install IceBrick systems in over 120 buildings. In 2023, the system became the first thermal storage technology to qualify as a demand-response resource by the California Public Utilities Commission.
Now, Nostromo is bringing its technology to New York. The state’s dense urban infrastructure and volatile energy pricing make it an ideal proving ground. New York’s grid often struggles during late-afternoon summer hours, when air conditioning demand surges just as solar generation dips.
Buildings like the 43-story Goldman Sachs headquarters, which installed an ice storage system in 2014, have reported up to 30% energy savings — over $50,000 per month in peak season.
“The potential here is enormous,” said Nostromo CEO Yoram Ashery. “Air conditioning is the single largest source of electricity demand during peak hours, and our solution directly addresses that.” According to the International Energy Agency, cooling accounts for about 20% of global building energy consumption—but can exceed 70% during peak times in hot climates.
By enabling buildings to consume less energy during those critical hours, ice batteries not only reduce costs but help utilities avoid triggering polluting backup generators known as peaker plants.
The environmental benefits are clear: unlike lithium extraction, which has serious ecological and ethical concerns, ice batteries use water—abundant, safe, and fully recyclable. “You’re never going to power a lightbulb with ice,” said one engineer. “But you might eliminate the need for fossil-fuel peaker plants just by cooling smarter.”
Another key to the system’s market success lies in Nostromo’s business model. Rather than selling its systems outright, the company offers them as a service. Building owners pay no upfront capital costs. Instead, Nostromo installs and maintains the units and collects monthly service fees over a 20-year period, based on a percentage of the building’s energy savings and revenues from grid participation.
In states like California, where time-of-use electricity rates are favorable, this approach can save building owners between $235,000 and $345,000 annually, with projected lifetime savings of \$9.4 million per installation.
Despite growing enthusiasm, thermal energy storage still faces real-world barriers. Large systems like IceBrick require space, access to a central chiller and utility rate structures that reward off-peak usage. In cities where electricity prices stay flat, or in colder regions with limited cooling demand, such systems may not yet be cost-effective.
Even in California, where the state has been a pioneer in renewable energy incentives, Nostromo’s expansion depends on completing a complex federal loan process and securing long-term contracts with commercial property owners. As a result, the technology's current reach remains mostly limited to large-scale commercial buildings.
Back in Israel, Nostromo has signed a cooperation agreement with the national electric utility to develop a virtual power plant, and its system is already operating on the roof of the Medinol medical device company in Jerusalem. According to Ashery, these kinds of projects demonstrate how thermal energy storage can play a vital role in stabilizing solar-heavy grids, particularly in the evening hours after sunset.
As global demand for cooling continues to rise—potentially tripling by 2050, according to IEA projections—the need for clean, scalable and cost-efficient storage solutions becomes increasingly urgent. Nostromo’s IceBrick may not store electrons, but it stores exactly what the grid needs when it’s most vulnerable: cold.
“The more renewable energy we add to the grid,” Ashery said, “the more we’ll need ways to store it. And in buildings, that often means storing cold."