An experimental computer chip called Ice River can reuse the energy put into it, researchers say.

A regular computer chip cannot reuse energy. All the electrical energy it draws to perform computations immediately becomes useless heat. Your phone or laptop will “use energy once and then throw it away,” says Michael Frank, a scientist at Vaire Computing, the London company where the new test chip was made. When your device is working hard, you can feel the warmth of all that wasted energy.

In data centers, large amounts of water and hardworking fans keep computers from overheating. AI demands powerful computer chips that draw more electricity than those in the past. As the technology proliferates, the environmental and energy costs of computing keep on rising.

The new chip, tested in August, drew around 30 percent less energy than a regular chip performing the same computation. The system was reusing a portion of its electrical energy instead of wasting it as heat. “This is quite exciting,” says Aatmesh Shrivastava, a computer engineer at Northeastern University in Boston. “We all want a computing system where we can recover energy.”

To develop Ice River, Frank and the team at Vaire reimagined two inefficient features of modern computer chips.

First, chips sold now waste energy by erasing information. A typical chip’s logic — the circuitry and rules that determine the way the chip processes information — only works in one direction. When you do a computation, the original 1s and 0s are erased, generating heat. IceRiver instead uses reversible logic, which allows it to un-compute and get the original information back. This avoids losing heat to erasures.

Second, modern chips waste energy when their voltage rapidly changes. Like a hammer coming down, the power supply slams 1s into 0s or vice versa. This allows for very fast computation, but those rapid changes give off heat.

In contrast, IceRiver uses an approach called adiabatic computing, in which voltages gradually go up and down. “You can think of [the energy] as sloshing back and forth,” Frank says. It’s more like a pendulum than a hammer. The system can partly keep itself going and reuse energy in the next operations. Importantly, the power supply doing all this is housed on the chip itself.

Computer scientists have known since the 1960s that this sort of system was theoretically possible. In the 1990s at MIT, Frank worked on test systems that showed reversible logic working. But Ice River is the first physical chip to combine reversible logic with a pendulum-like power supply on board, he says. With just one or the other, Frank says, you can’t reuse a meaningful amount of energy.

The August test was an important proof of concept. Before that moment, says Vaire cofounder Hannah Earley, “I’ve been sketching [the chip] on paper and [running it] in simulation.” She was thrilled to finally see Ice River work in real life.

Erik DeBenedictis, who runs the computing company Zettaflops in Albuquerque, N. M., says Vaire is “much closer” to a reversible chip that would be useful in the real world than anybody has come before.

However, there’s still a long way to go. “This type of technology will take a long time to become more mainstream,” Shrivastava says. For one thing, adiabatic computing “is a slow process,” he says. Because these chips don’t heat up like usual ones, you can pack them more closely together to make up for the slower speed, but that ups the cost. Vaire will need to find ways to scale up effectively and to reuse even more energy. “They have a challenge ahead of them,” DeBenedictis says.