NASA, U.S. Navy and university researchers have successfully demonstrated the first robotic underwater vehicle to be powered entirely by natural, renewable, ocean thermal energy. Though not quite a perpetual motion machine it is close to that. The Sounding Oceanographic Lagrangrian Observer Thermal RECharging (SOLO-TREC) autonomous underwater vehicle uses a novel thermal recharging engine powered by the natural temperature differences found at different ocean depths. Scalable for use on most robotic oceanographic vehicles, this technology breakthrough could usher in a new generation of autonomous underwater vehicles capable of virtually indefinite ocean monitoring for climate and marine animal studies, exploration and surveillance.
NASA, U.S. Navy and university researchers have successfully demonstrated the first robotic underwater vehicle to be powered entirely by natural, renewable, ocean thermal energy. Though not quite a perpetual motion machine it is close to that. The Sounding Oceanographic Lagrangrian Observer Thermal RECharging (SOLO-TREC) autonomous underwater vehicle uses a novel thermal recharging engine powered by the natural temperature differences found at different ocean depths. Scalable for use on most robotic oceanographic vehicles, this technology breakthrough could usher in a new generation of autonomous underwater vehicles capable of virtually indefinite ocean monitoring for climate and marine animal studies, exploration and surveillance.
!ADVERTISEMENT!Researchers at NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif.; and the Scripps Institution of Oceanography, University of California, San Diego, completed the first 3 months of an ocean endurance test of the prototype vehicle off the coast of Hawaii in March.
"People have long dreamed of a machine that produces more energy than it consumes and runs indefinitely," said Jack Jones, a JPL principal engineer and SOLO-TREC co-principal investigator. "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."
The term perpetual motion, taken literally, refers to movement that goes on forever. However, the term more commonly refers to any device or system that perpetually (indefinitely) produces more energy than it consumes, resulting in a net output of energy for an indefinite time. The law of conservation of energy, which states that energy cannot be created or destroyed, implies that such a perpetual motion machine cannot exist.
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. 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 pressure of the oil is periodically released to drive 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 up and down.
Sooner or later the submersible charging system will fail because perpetual motion machines cannot truly exist. However, it may take a good long period of time to fail.
So far, SOLO-TREC has completed more than 300 dives from the ocean surface to a depth of 500 meters (1,640 feet). Its thermal recharging engine produced about 1.7 watt-hours of energy per dive, which is enough electricity to operate the vehicle's devices.
The performance of underwater robotic vehicles has traditionally been limited by power considerations. "Energy harvesting from the natural environment opens the door for a tremendous expansion in the use of autonomous systems for naval and civilian applications," said Thomas Swean, the Office of Naval Research program manager for SOLO-TREC. "This is particularly true for systems that spend most of their time submerged below the sea surface, where mechanisms for converting energy are not as readily available. The JPL/Scripps concept is unique in that its stored energy gets renewed naturally as the platform traverses ocean thermal gradients, so, in theory, the system has unlimited range and endurance. This is a very significant advance."
Battery systems have been a round for awhile but they always have needed some way to recharge. The present system is recharged by a more natural way based on ocean temperature gradients.
In theory the same method of recharging can be used on other types of submersible vessels. This is an immense stride for certain types of "green" vessels vastly extending vessel range and abilities for minimal cost.
For further information: http://www.jpl.nasa.gov/news/news.cfm?release=2010-111&rn=news.xml&rst=2544
