Subject: Viridian Note 00216: Piezoelectric Eel

Bruce Sterling []

Key concepts: piezolectricity, biomimicry, sewerspace,
Ocean Power Technologies, polyvinylidene fluoride

Attention Conservation Notice: Kind of a Viridian gizmo Christmas toy knickknack military blobject thing.

(((bruces remarks: I'm way too busy cleaning my office to manage a Note more ambitious that this. If you're coming here for New Years, we'll see you soon.)))

Source: New Scientist magazine

"Reinventing the eel

"AN ARTIFICIAL eel that can harvest energy from the currents of the ocean, a river or even a sewer is being developed by engineers in the US. (((Electronic sewer apps are a big trend lately.))) The eel's tail thrashes around in turbulent underwater flows, flexing to produce a current that charges a battery.

"The idea is to provide long-term power for remote- sensing and surveillance devices that the US Navy drops into the sea. Currently, these use small dynamos to generate power, but their turbines clog quickly, rendering them useless.

"'We have built a prototype that works well and we're now developing a larger-scale version,' says Sean Kammenn, chief engineer on the project at Ocean Power Technologies in Pennington, New Jersey.

"The prototype eel is essentially an underwater flag the size of a football scarf. It's made of a piezoelectric polymer called polyvinylidene fluoride (PVDF), which produces a small current when flexed. The flag is only a couple of millimetres thick and so flutters easily when it is anchored in a turbulent flow. (((Cut to the chase and make that scarf into a wearable couture item. PVDF might also make great aquatic galoshes to go with your piezoelectric Gershenfeld jogging shoes.)))

"The energy this produces trickle-charges a battery. 'The prototype produces about 10 milliwatts, but the eel we are developing for the US Navy will produce about 1 watt of usable power,' says Kammenn.

"The navy plans to use the eel to power sensors dropped in remote ocean locations. These will measure factors such as sea temperature and salinity for weather forecasts and broadcast the data via a satellite to the mainland. (((Wow! A fabulous Greenhouse app!))) The eel may also power underwater microphones for listening to underwater traffic. 'The Navy drops lots of sensors that are only able to broadcast data for about an hour because of battery limitations. However, the eel should produce power for at least a year,' says Kammenn. ((("Kids! Buy your own Navy-Surplus Slimy Spy Eel!")))

(...) "The team has already carried out trials in the lab and is hoping to begin ocean testing in a tidal estuary sometime during 2001. 'We're looking for a suitable site right now,' says Smits.

"The eventual objective, however, is to make an artificial eel that can swim. By reversing the flow of current to the piezoelectric material, the researchers believe it should be possible to make it flex in a way that drives it through the water like a real eel. The idea is that an eel carrying surveillance equipment and a fully charged battery would be dropped into an enemy sewer or storm drain, stopping to recharge whenever necessary." (((Those of you who read the Viridian issue of TIME DIGITAL (Jan-Feb 2001/2026) probably thought we were making it all up about those sewer-based "jellybot" surveillance devices. Another "Viridian Imaginary Product" swims gamely toward real-world existence!)))

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