The SL1 is intended to be attached to submersible research robots loaded with sensors known as profiler floats. These devices collect data on short trips up to a mile below the surface. When they emerge from the depths, they transmit this information to a satellite. Today, thousands of profiler floats drift through the Earth’s oceans as part of an international program called Argo. They remain the best tool available to scientists for studying the high seas remotely, but their lifespan and data collection are severely limited by their energy sources.
All floats in the Argo fleet are powered by lithium-ion batteries, which are usually only good for around five years or a few hundred dives. Their dependence on the battery limits how often they can dive; a typical float does this only once every 10 days. And after the death of its battery, a float is usually abandoned, because the cost of its collection is higher than the cost of the device itself. Still, a float can cost as much as a new car, making them expensive jetsam parts.
“Everything we put in the ocean is limited by its battery,” says Steve Jayne, senior scientist at the Woods Hole Oceanographic Institution, who is not involved with Seatrec. “If you had unlimited energy, you might be able to create a profile every day instead of every 10 days.”
Seatrec’s ocean generator doesn’t produce a lot of power – each charge cycle completes it with about half the power of a single AA alkaline battery – but that’s more than enough to meet the needs of low-power sensors. power typically found on profiling floats. For applications that require more power, says Chao, it is possible to increase the size of the generator or simply to connect the smaller ones in series. The floats are also designed to work in any ocean environment, whether trapped among arctic ice or dived among sharks in the tropics. All it takes to adapt them to different regions is tweaking the chemistry of their waxy guts so that they solidify and melt at the right temperatures.
Chao hopes the Seatrec ocean generator will deliver on a promise first conceptualized in the 1980s by renowned oceanographers Douglas Webb and Henry Stommel. They contemplated a global fleet of missile-shaped underwater research robots called Slocum gliders it would explore the oceans with the same dexterity, autonomy and longevity that we expect from the robots that NASA sends to explore other planets. Like Seatrec’s SL1, these gliders would be propelled by temperature differences underwater.
Although Webb, Stommel and their associates have made progress towards creating a global Slocum fleet, their vision is still in development, says Matt Palanza, program engineer at the Woods Hole Oceanographic Institution. Ocean Observatory Initiative who previously worked with Webb. Palanza’s team at the Ocean Observatory oversees the world’s largest civilian fleet of Slocum gliders – 50 in total – and he says the reason there aren’t thousands of patrols in the world’s oceans is simply a lack of funding. “The technology is out there and constantly changing,” he says.
Chao and the Seatrec team believe that extending vehicle lifespan with unlimited clean energy could dramatically increase the size of ocean research fleets. But the company is not the first to work on the technology. In 2003, Webb built a prototype thermal glider that used temperature differences to control its ascent and descent in the ocean, but still relied on batteries for its electronics. In 2008, a team led by researchers from Woods Hole successfully deployed a different prototype glider in the Caribbean that used differences in ocean temperature to power an electric propulsion system. The following year, Chao and a team of researchers from NASA and the Scripps Institution of Oceanography deployed Solo-Trec, the world’s first profiling float powered entirely by electricity generated by temperature differences.