EAT your heart out, Duracell bunny: NASA has unveiled an ocean-going robot that really can go on forever. It is the first of its kind to be fuelled entirely by renewable energy.
This month the agency revealed that , a wax-filled buoy powered only by the temperature differences in the water around it, has been tirelessly diving to depths of 500 metres off the Hawaiian coast three times a day since November 2009. The float gathers data on temperature and salinity to improve studies of ocean currents.
SOLO-TREC extracts thermal energy from the ocean each time it travels from the cold depths to the warmer surface. Tubes of oil on its shell are surrounded by a compartment filled with two different waxes. They flip from solid to liquid when the sea temperature exceeds 10聽掳C, and expand by 13 per cent (see diagram).
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The expanding wax squeezes oil from the tubes into the float鈥檚 interior, where it is stored at high pressure. The oil can then be released to drive a generator and charge batteries. They power the pumps that take on and expel water so the buoy can dive and surface, and also the float鈥檚 GPS receiver, sensors and the transmitter that beams data to satellites when at the surface.
鈥淓ach full dive generates about 200 watts for 30 seconds,鈥� says Jack Jones, one of the project鈥檚 leaders at the in Pasadena, California.
鈥淭he buoy can recharge as it travels to the warm surface. Each dive generates about 200 watts for 30 seconds鈥�
He and colleagues hope to create large numbers of the floats to boost existing monitoring of oceanic conditions, which helps in weather and climate prediction.
More mobile robots that use the technology are planned. in Falmouth, Massachusetts, makes winged robots that 鈥済lide鈥� underwater using thermal wax to control buoyancy. But they need batteries for their electronics.
The US Office of Naval Research has asked the two teams for ideas for gliders that will never need a battery change.
