Piezoelectric Energy Harvester
Sponsor: Steven Alexander, Professor of Physics
I have created a floor-pad that will act as a passive energy harvester, collecting the energy of people’s footsteps and converting it into electrical energy. This project makes use of piezoelectric elements which can convert physical stress into electricity. Every day, billions of people walk through high traffic areas such as doorways and sidewalks. The goal of this project is to create a device that could be used to power electronics simply by using the work these people are already doing by going about their day to day lives.
In order to do this, an artificial, piezoelectric polymer was used. This polymer has been stretched into a film and placed between two incredibly thin pieces of aluminum foil. Two leads are attached to each sheet of aluminum, allowing the mechanical stress to be turned into an electric signal. Each of these thin sheets can only be stressed so much however. To increase the amount of electricity that can be pulled form a single footstep, four of them were stacked on top of each other and wired in series. In this manner, they signal is multiplied and more energy is gathered for the same amount of applied physical stress.
The next task was to create a circuit that could harness the raw energy being produced. In order for the signal to be transferred into something that could be used to charge a battery, a circuit designed for ultralow voltage energy harvesting was finally decided on. The two main portions of this circuit revolve around two integrated circuits. Their model numbers are S-882Z and S-8353D30MC. The integrated circuit S-882Z acts as a pool of charge. As voltages are pumped into the circuit, it stores them up and when the voltage reaches a certain level, it dumps the stored energy into the next phase of the circuit.
The next step of the circuit revolves around the integrated circuit S-8353D30MC. This integrated circuit is an IC pump converter. The main job of it is that it takes the energy that is dumped into it by the first section of the circuit and steps up the voltage to 3.0 volts. This allows the circuit to be used to charge a small battery, such as the ones that a cell phone uses as well as other batteries for small electronics. This circuit has the ability to take inputs as small as 0.3 volts and step up the voltage by a factor of ten, which makes it ideal to be used in low output energy harvesters.