The remotely operated vehicle (ROV) developed by a team at the Virginia Institute of Marine Science, is able to use acoustic signals to gauge the volume of a spill, and locate the thickest part of the slick, a task that is currently performed by visual surveillance from aircraft ands boats. The difficulty of assessing spill size and volume is likely to increase as oil exploration and recovery moves into Arctic waters, where ice and bad weather can hinder access and visibility.
Developed with funding from the US government’s Oil Spill Response Research program, and tested in the program’s 2.6 million-gallon Ohmsett wave tank in Leonardo, New Jersey, the ROV gauges the thickness of a slick by emitting sound waves from below. These waves reflect off the density boundaries between water and oil, oil and air, or oil and ice. Measuring the slight delay between the reception of these reflected echoes allows the vehicle’s software to gauge the thickness of surface and below-ice oil slicks at very fine resolution—from slicks less than 0.5 millimetres thick to more substantial accumulations of up to several centimetres.
The ROV’s main electronics reside in a plastic case that stays topside. The ROV is tethered to the electronics by about 130 feet of cables. The controlling computer—a laptop with a joystick—connects to the electronics via Wi-Fi so that the operator can operate the electronics-ROV package from a pool-deck, or in the case of experiments at the Ohmsett tank, an observation tower.
“Our ROV will provide a test platform for developing other sensors and for field applications,’ said project leader Prof Paul Panetta. ‘It’s one step along the path to developing platforms for use in the ocean to measure slick thickness and other oil properties using acoustics.”
The ultimate goal, he added, is to continue refining the technology so that it can one day be used to help respond to an actual spill in the open ocean. “We’ve already thought of several improvements,” he said, “including integrating the video stream into the ROV software for more seamless operation. We’d also like to create a database of the acoustic properties of different types of oil as a function of temperature.”
Panetta said that future iterations of the technology might mount the sensors on an autonomous underwater vehicle or other free-swimming platform for greater flexibility and wider coverage.
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