So, how does it work? Again, we'll allow the certified geniuses at NASA's Jet Propulsion Laboratory to explain:People have long dreamed of a machine that produces more energy than it consumes and runs indefinitely... While not a true perpetual motion machine, since we actually consume some environmental energy, the prototype system demonstrated by JPL and its partners can continuously monitor the ocean without a limit on its lifetime imposed by energy supply.
Got it? And the best part of all is that it actually works. So far, SOLO-TREC has completed 300 dives, each of which produced about 1.7 watt-hours, or 6,100 joules, of energy – enough to power the vehicle's science instruments, GPS receiver, communications device and buoyancy-control pump.SOLO-TREC draws upon the ocean's thermal energy as it alternately encounters warm surface water and colder conditions at depth. Key to its operation are the carefully selected waxy substances known as phase-change materials that are contained in 10 external tubes, which house enough material to allow net power generation. As the float surfaces and encounters warm temperatures, the material melts and expands; when it dives and enters cooler waters, the material solidifies and contracts. The expansion of the wax pressurizes oil stored inside the float. This oil periodically drives a hydraulic motor that generates electricity and recharges the vehicle's batteries. Energy from the rechargeable batteries powers the float's hydraulic system, which changes the float's volume (and hence buoyancy), allowing it to move vertically.
[Source: NASA Jet Propulsion Laboratory via Engadget]