Monday, December 28, 2009

Piezoelectric Tree Harvests Breeze Power

Imagine all the energy moving through the leaves of a large oak or pine. Have you ever tried to devise a way to tap into the power of a breeze using the leaves of a tree? Cornell researchers have devised a "piezo tree", an artificial tree-like structure with piezoelectric "leaves." But don't expect to power your house from just one tree.
Researchers at Cornell University have created an energy harvesting "piezo-tree" based on the fluttering of leaves where synthetic leaves are connected to a piezoelectric stem. The device is able to convert the energy in wind into electric power whilst remaining light, low-cost, and easily scaled.

In the prototype, the flexible plate and film are driven to oscillate just as a flag or leaf might flap in the wind. The flapping motion is attributed to instability of the aero-elastic system. When creating the piezo-tree, researches used the flexible piezoelectric material Polyvinylidene Fluoride (PVDF) as the basic component, as it could withstand unpredictable wind strength. The basic design is to clamp one edge of PVDF element to a cylinder bluff body and leave the other edge free. When the wind crosses this bluff body, it will lead to a vortex shedding and the periodic pressure difference will drive the piezo-leaf to bend in the downstream of the air wake, synchronously. AC signal is collected from the flapping piezo-leaf, which is working on a periodic bending model, and the electrical energy is stored in a capacitor after rectifying it with a full-wave bridge. _EnergyHarvestingJournal_via_Ecofriend
The project is at the level of 100 pico watt, but has come up with multiple ideas to increase the output by orders of magnitude.

Of course, if you want an artificial tree that is truly functional, why not design it to concentrate CO2 (and turn it into fuel), condense and accumulate pure water for use (and tap into aquifers as well), harvest energy from wind AND sun, and provide multi-functional communications infrastructure (omni-antenna transceiver) -- plus a built-in docking station for robotic groundskeepers and maintenance robots.



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