Courtesy of Clare Reimers/Oregon State University
Instruments that monitor poorly understood deep-sea phenomena burn through their batteries in less than a year, and sending a ship to change them runs about $10,000 a day. So Clare Reimers, an oceanographer at Oregon State University, devised a novel fuel cell that generates electricity using little more than salt water and muck.

Reimers, working with colleagues at Rutgers University and the Naval Research Laboratory, found a way to tap into the natural voltage difference between decomposing ocean-bottom organic sediment and the water just above it. Electrodes made of carbon fiber, platinum, or graphite span the two layers, conveying electrons from one side to the other and generating a current. A prototype cell (above) produces enough electricity to run a salinity sensor or underwater microphones, and the technology is easily scaled up. Soon scientists may be able to build affordable seafloor sensor networks— no batteries required.