Climate Tech

Seatrec’s self-replenishing batteries could make ocean research cheaper

Its batteries generate energy from temperature differences in the ocean.
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Yaorusheng/Getty Images

· 4 min read

The vast majority of the ocean’s seabed floor has never been reliably mapped by humans.

Several initiatives exist to change this, including the Nippon Foundation-GEBCO Seabed 2030 Project, a global partnership that aims to map the entirety of the sea floor by 2030. To achieve this feat, the initiative has signed up companies making cutting-edge tech that ranges from autonomous underwater vehicles to satellite-based ocean mappers. And last week, the initiative signed a new partner: Seatrec. The company will send Seabed 2030 the ocean floor data it collects via echo sounder-equipped floats that run on its battery technology—a system that generates renewable energy from differences in the ocean’s temperature.

Like drones that fly in the sky, ocean-exploring robots need battery power to do their jobs—and there aren’t many power outlets in the open seas. Seatrec has devised a way to fill that gap with batteries that self-replenish by harvesting thermal energy from the ocean.

The company primarily sells to other ocean equipment-makers, though it builds its own robots as well. Seatrec claims it can lower the cost of ocean research, because devices equipped with its batteries don’t need to be manually recharged or replaced. Seatrec’s SL1 battery platform costs $25,000 to operate and deploy, and depending on the scale of data collection a client needs, a second module can be attached.

Image of two SL-L seatrec battery platforms


According to Seatrec’s founder and CEO, Yi Chao, its clients include companies like New Hampshire-based Airmar Technology, which manufactures ultrasonic sensor technologies. It also works with firms specializing in other marine sensing tech, like temperature and salinity sensors (measuring the saltiness of the ocean) or hydrophone sensors (underwater devices that detect and record ocean sounds).

The federal government is also a customer: Seatrec has received over $2 million in federal contracts since the company spun off from NASA’s Jet Propulsion Laboratory at Caltech in 2016, Chao told us. It has also received $3.5 million in venture funding, with a $2 million round as recent as 2020.

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Right now, the operational range for Seatrec’s batteries is limited to the two-thirds of the ocean that experience a temperature difference of 5-10 degrees Celsius between its surface and its depths. That excludes most of the Arctic and Antarctic, as the water is always cold from top to bottom.

How it works: Seatrec’s batteries function on what Chao calls “energy harvesting,” which takes elementary science—how liquids change into solids, gases, and back again—and applies it to battery technology. As the elements Seatrec uses in its batteries shift between states, these "phase change materials” melt, harden, and fluctuate in volume as a result. Those fluctuations, in turn, drive a motor that converts hydraulic energy into electricity that can power things like sensors and robots.

“We basically pack our materials into a backpack. They are solid when they are cold, because, like a candle, they are a solid material” Chao told us. “When it comes to the surface, those materials [melt] into a liquid. So the backpack kind of expands in volume, and that expansion will create this kinetic energy and then turn it into electricity.”

Looking ahead…Chao hopes to apply Seatrec’s tech to additional ocean-tech projects, like providing portable power for machines doing seaweed farming, which has the potential to help with carbon sequestration or to serve as biofuel. Seatrec also plans to add hydrophones to its equipment in the next year, which could help detect sounds like animal migrations, marine mammal singing, and underwater volcanoes.

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