05-10-2012, 12:08 PM
Power from Plastic
Power from Plastic.ppt (Size: 7.47 MB / Downloads: 178)
Advantages of Dielectric Elastomer EAP Power
Lighter – low density, high performance, multifunctional polymers
Cheaper – inexpensive materials, fewer parts, no precision machining
Quieter – high energy density and compliance of polymers allows quiet primarily sub-acoustic operation with few moving parts
Softer – rubbery materials are impedance matched to large motions (e.g. human motion, engines)
Versatile – polymers are scale-invariant; systems can be made in variety of form factors (conformal, elongated, etc.)
Dielectric Elastomers: Principle of Operation
Dielectric elastomers are a type of EAP that uses an electric field across a rubbery dielectric with compliant electrodes
Variable capacitor generator– energy generated as nearly incompressible polymer layers increase in area and decrease in thickness when stretched
Polymer Dielectric Elastomer Materials
Several elastomers work well
Acrylic and silicone are most promising and have shown exceptional energy density
Acrylic has greater energy density but also greater damping and electrical leakage
Silicone has exceptional temperature range (–60 to 260 C)
Power Conversion and Management
Power available from dielectric elastomer EAPs is at a high voltage (e.g., 2 kV)
For most applications we would like to charge batteries at a low voltage (3–48 volts)
Some applications can use high voltage directly (e.g. night vision optics, in-boot actuators)
High-voltage is not all bad: low current can allow for thinner, lighter wires and simpler connectors
Battery or capacitor energy storage is needed to smooth output
Enabling a Heel-strike Generator
Energy from the heel strike is “free” - it would otherwise be dissipated as heat
Energy converted per step with reasonable heel compression can be up to 5 J
Power generated (both feet) during walking is 1W to 10 W
The amount of electrostrictive polymers needed to convert 5 J is less than 50 g or 50 cc.
Electromagnetic or piezoelectric devices would weigh more than 10 times this weight
Applications of a Heel-strike Generator
Boot generator can assist the dismounted soldier in several distinct ways
Power source or battery recharger to reduce battery weight for a mission
Smart Shoes, Multifunctional Footwear - simplify logistics by reducing the number of separate batteries or devices required
power an instrument that should logically be located in a boot for best operation:
personal navigation system, medical status monitor, foot warmer
power a device that could be located in a boot for weight or space savings
Friendly ID beacon, comm link, magnetometer, chem/bio detector, special battery or capacitor for high-voltage device such as night vision scope
Dynamic Footwear - Actuation or Adaptability for enhanced performance
reduced injury
improved comfort
more efficient load carrying