It’s a concept that seems obvious: provide power to underwater vehicles using the ocean itself. Logical the tactic may be, but the technology required for the concept’s execution has eluded scientists until recently — just this week, in fact. On April 5, U.S. Navy and university researchers reported a successful demonstration of the first underwater vehicle powered solely by ocean thermal technology.
The Sounding Oceanographic Lagrangrian Observer Thermal RECharging (SOLO-TREC) vehicle splashed its way to a triumphant endurance test off the coast of Hawaii. According to NASA’s Jet Propulsion Laboratory, the “autonomous underwater vehicle uses a novel thermal recharging engine powered by the natural temperature differences found at different ocean depths.” The revolutionary technology is scalable, which will allow it to be used on most robot oceanographic vehicles, and is predicted to bring about a new generation of autonomous underwater vehicles able to indefinitely monitor their sub-aquatic environs.
SOLO-TREC operates by drawing the ocean’s natural thermal energy as it gradually sinks from the warm surface to the cold depths. Ten external tubes contain waxy substances known as phase-change materials. As SOLO-TREC (or any future vehicle equipped with the technology) rises to the warmer surface, the material melts and spreads; conversely, it solidifies and contracts in cooler waters. The expansion of the wax pressures oil stored within the float, which in turn drives a hydraulic motor that supplies electricity and recharges vehicle batteries. After the batteries provide juice to a hydraulic system, the hydraulic system alters the vehicle’s volume, which grants it vertical movement.