In a recently-published academic paper titled "Energy harvesting from a backpack instrumented with piezoelectric shoulder straps," mechanical engineers from Michigan Technological University and Arizona State demonstrate the potential of a backpack that makes its own energy via piezoelectric straps.
According to a story on www.physorg.com, the piezoelectric backpack straps are the latest innovation in the area of "energy harvesting," where otherwise-wasted, ambient energy is converted into electrical energy to prolong the life of electronics.
Apparently, the rubbing of backpack straps on shoulders creates enough movement, heat and energy to create electric power that can be transferred to charge GPS devices, headlamps, a cell phone, or an iPod Nano while on the go.
"The strap would operate no differently than the strap on a traditional backpack," said Henry Sodano from Arizona State.
The theoretical backpack uses straps made of polyvinylidene fluoride (PVDF), a strong, flexible material that feels similar to nylon. But unlike nylon, PVDF is piezoelectric, meaning that an applied stress generates an electrical charge.
When carrying a 100-pound load -- a typical amount for a soldier's pack, according to the researchers -- and walking at 2-3 mph, simulations showed that the straps could generate 45.6 mW of power.
The researchers said that this output could be used to power small electronics.
The researchers hope that additional energy harvesting systems can be integrated into a user's other gear -- shoes maybe? -- based on the results of the to-be-created piezoelectric backpack straps.
See http://www.physorg.com/news108897656.html for the full story.