How to cool down in a warming world

Posted: June 02, 2025

As the world warms, air conditioning is becoming a bigger problem—not just for the many people who lack cooling, but also as a crucial contributing factor to both climate change and energy security.

The International Energy Agency already warned of a looming “cold crunch” in 2018, calling the rising demand for space cooling “one of the most critical yet often overlooked energy issues of our time.”^[1]

Even if governments meet their climate targets, energy consumption for cooling buildings could triple by mid century as more and more households install air conditioners. It already makes up around 10% of global electricity consumption. Last year, rising air conditioning use during heatwaves was the main reason behind accelerating demand growth for power. 

This means not only higher emissions—fossil fuels met much of that extra demand—but also unpredictable strain for the grid.

“It is a blind spot for many decision-makers,” Fatih Birol, the IEA’s executive director, said last year.

In other words, much still has to happen to address the growing impact of those cooling needs. The good news: there are multiple efforts now to at least address one part of this puzzle—how to make air conditioners themselves more efficient.

Improving air conditioner efficiency with 3D-printed heat exchangers

One group of researchers recently figured out a potentially promising way to manufacture heat exchangers, which are the central component of air conditioners but are also used in everything from data centers to factories to ships.

The researchers developed machine-learning models and ran thousands of computational fluid dynamics simulations to design a better two-phase heat exchanger using a common refrigerant.  

In a heat exchanger, cold water cools the refrigerant through a thin wall, changing it from gas to liquid. The researchers’ models figured out how best to maximize that heat transfer by increasing the surface area of the membrane between the two fluids. It turns out that means wavy walls, as well as lots of precisely placed bumps, fins, and other protrusions—which also help mix the refrigerant.

The team made their model with a 3D printer, using lasers to fuse together layers of aluminum alloy. It achieved a power density similar to that of brazed plate heat exchangers, a common design, and outperformed others by up to 50%.

Traditional manufacturing techniques would struggle with the design, however, and the laser sintering the researchers used is still too expensive to be viable beyond niches such as aerospace or next-generation ships.

Still, “it’s worth exploring, and I don’t think that we know yet where we can push it,” Dennis Nasuta, director of research and development at consulting firm Optimized Thermal Systems, told MIT Technology Review. 

Giant ice cube trays turn air conditioning into energy storage

At least one company has made it its mission to not only develop new cooling technologies—but at the same time address the issues air conditioning causes for the power grid.

In 2023, Nostromo Energy installed a system called the IceBrick at a Beverly Hilton and neighboring Waldorf Astoria hotel in Los Angeles. It’s pretty much what it sounds like: a huge tray of 40,000 half-gallon capsules that hold some 150,000 pounds of ice.  

It works by cooling down a solution of water and glycol, which then freezes the water in the heavily insulated capsules. When needed, the process is reversed: the ice cools down the coolant solution as it melts, which in turn cools the water circulating through the building’s chilling system.

The key is that it can function like a battery: using cheap electricity early in the day to start “charging up” by freezing the ice tray, which takes around 10 hours, and then releasing it in the late afternoon, when demand is high. That means the air conditioning doesn’t add to grid strain at the most critical time of day, and also costs less for building owners. (The tradeoff is that, due to inefficiencies, the IceBrick actually uses more total energy for cooling.)

The company's software enables the systems to operate as a virtual power plant, allowing it to coordinate multiple IceBricks or run each individually. In December, it secured a conditional commitment for a $305 million loan from the Department of Energy to install almost 200 IceBricks in California over the next five years.

How desiccants could make air conditioning more efficient

Companies are also exploring solutions to lower the actual energy used in air conditioning. One of them: desiccants. Yes, like those little silica packets you find at the bottom of a pill bottle or in a new purse.

When it comes to cooling technology, the desiccant is more likely to take the form of a liquid salt solution. That’s what Blue Frontier, a Florida-based startup, is using—along with evaporative cooling.

Standard air-conditioning systems, it turns out, operate extremely inefficiently by simultaneously cooling air with a refrigerant and dehumidifying it during chilling—which is necessary to avoid damage to the machine itself. A highly absorbent desiccant cuts down on the dehumidification the AC needs to perform.

Meanwhile, evaporative cooling eliminates the energy-intensive process of vapor compression by which regular AC units condense and expand a refrigerant to absorb and release heat. Instead, it simply takes advantage of the cooling effects of evaporating water, which absorbs heat as it turns from liquid to gas.

As Blue Frontier CEO Daniel Betts explained to Scientific American, the company’s system uses its liquid salt desiccant to dry the air and then splits it into two adjacent streams. One of them passes over a thin layer of water to induce evaporation, lowering the temperature of the surrounding metal—which then cools the other airstream before it flows back into the room. The whole system reduces energy use by between 50% and 90% based on the company’s field trials, according to Betts.

Transaera, another desiccant-focused startup, instead uses crystalline structures called metal-organic frameworks—molecular cages that can catch particles and release them when heated. In this case, an MOF-coated wheel captures water from the air and then empties it using the AC’s waste heat (one researcher has likened the contraption to “sponges on steroids”).  

The company wants to develop an in-home air conditioning unit eventually but needs to make the economics work first. For now, it’s trialing the dehumidification technology in a commercial warehouse and hopes to convince big air conditioning manufacturers to adopt it in their own products, CEO Sorin Grama told TechCrunch. 

The commercial HVAC market “really wants—demands—more efficient systems,” he said.