Table of Contents
INTRODUCTION TO PIEZOELECTRICITY
EQUATIONS AND VARIABLES
EXAMPLES OF COMPLETED PROGRAM
Research and the creation of this project was to figure out how Piezoelectricity works and how to utilize it in everyday life. We decided that creating a piece of a highway would give us the most amount of energy. The equations, pictures, and other information was accumulated through different scholarly sources found on the internet and cited at the end. We used this information to help us understand and model what power output we could get from changing a section of a highway to include Piezoelectric material.
The Piezoelectric effect is when a Piezoelectric material is compressed or lengthened, resulting in a voltage. This is also conversely true, although we do not focus on this. The Colorado, Interstate 25 has about 174,000 vehicles on it per day. These cars have a force on the ground that is currently being unutilized. Through the use of Piezoelectricity, we can harness this force and turn it into power through the Piezoelectric effect. We can store this power in batteries for emergencies, or push it directly into the power grid, however we are storing it in capacitors.
Introduction to Piezoelectricity
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Piezoelectric generators (commonly known as Piezos) we first need to define a few things. The effect called The Piezoelectric Tile diagrams show what happens to a voltmeter when the material is squeezed(right) or pulled apart(left) - (Image Created by N. effect” is the electromechanical interaction between the states of mechanical and electrical in some materials. In more layman terms, it is the electric charge that accumulates inside of solid materials in response to mechanical stress. This is only true if there is no inversion symmetry in the material. Inversion symmetry is when, on a molecule, there is an atom that is in a directly opposite (along the x, y, or z axis) that is identical to it.
Some naturally occurring crystals that have the piezoelectric effect include: Quartz, Sucrose, Topaz, and other crystals, including synthetic ones, that share similar structure as Quartz. Some other materials that possess the Piezoelectric effect include: bone, silk, and wood. For more realistic purposes, people have commonly used ceramics like Barium titanate (the first Piezoelectric ceramic discovered) and Lead zirconate titanate (the most common piezoelectric ceramic used today).
Something else that is interesting about the Piezoelectric effect, is that it is completely reversible. This means that if a voltage is put onto a Piezo, then it will cause the material to be stretched. Note that pushing a Piezo together will cause a positive voltage, while pulling it apart will cause a negative voltage. The same is also true inversely.
The geometry, thickness and other things effect how efficient the Piezo is. In the Table 1 (from source number 9) it shows some of these paramiters.
Geometry The most efficient form to produce more energy is tapered shape Thickness More energy is produced with thinner material Loading More energy is produced with increase in mass or force Mode Fixation Fixation at one end will result in more deflection, thus more energy when subjected to external force, than when fixed at two ends Structure Bimorph structures produce double the energy output than unimorph structure Table 1: Piezoelectricity parameters.
As the Piezo has a force or pressure exerted on it, AC current, and therefore voltage, is created. This can then be turned into DC voltage and used in normal electronics. Figure 1 shows the steps of harvesting power from piezoelectrics.
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Piezoelectricity was discovered in 1880 by French physicists Jacques and Pierre Curie. They combined their knowledge of pyroelectricity (the property of certain crystals which are naturally electrically polarized and thus contain large electric fields) with their understanding of their underlying crystal structures to figure out the Piezoelectric effect (detailed above). The Curies, however, did not predict the converse Piezoelectric effect. This effect was mathematically deduced from Gabriel Lippmann in 1881. After this the Curies immediately confirmed the existence of the converse effect, and went on to obtain quantitative proof of the complete reversibility. For the next few decades, Piezoelectricity remained something of a laboratory curiosity. More work was done to explore and define the crystal structures that exhibited Piezoelectricity, while there was not much interest from consumer products to integrate them into their electronics.
The first practical application for Piezoelectric devices was sonar, first developed during World War I. The use of Piezoelectricity in sonar, and the success of it, created a lot of interest in Piezoelectric devices. Over the next few decades, new Piezoelectric materials, and new applications for those materials, were explored and developed. Ceramic phonograph cartridges simplified record player design and made them cheaper and easier to build. The development of the ultrasonic transducer allowed for easy measurement of viscosity and elasticity of fluids and solids. This led to huge advances in materials research. Ultrasonic time-domain reflectometers (which send an ultrasonic pulse through a material to measure reflections from discontinuities) could find flaws inside caste metal and stone objects, improving structural safety. Some more recent uses are electric lighters, Ultrasound imaging, and ultrasonic procedures. Piezoelectric transducers are often used in ultrasound equipment and with the advances in this and other equipment have helped improve monitoring of pregnancies and other invasive surgical procedures. Newer uses for Piezos are exactly
what we are researching. Several places, such as California, are arriving at the same conclusion as us, that we can harness energy from cars moving and are creating Piezoelectric roadways.
During the energy crisis that became popular knowledge in the early 2000’s, citizens and the government of the United State have been trying to create and use sustainable energy sources including solar panels, wind turbines, and hydroelectric dams. We do this because we are running out of non-renewable resources such as gas and coal. While these things are good for getting energy from natural causes, there hasn’t been many ways to harness the wasted energy from human usage. Humans waste energy from walking, driving, and even being alive. The way to do this is Piezoelectricity. Knowing now about Piezoelectricity we needed a way to create stress on the material. The easiest way to create this stress, we concluded, was with gravitational force. Many streets, and specifically interstates, have massive amounts of force being pressed on them every day. This can be upwards of 200,000 cars per day. We concluded that this is would be the most effective way to harness gravitational force with our Piezos. In Colorado, on Interstate 25, there is an average of 174,000 cars passing any section of the highway on any day. With an average personal vehicle weighing 1800 Kilogram this would cause upwards of 18,000 newtons of force. Most of this force could be harnessed and put into our power grid or into batteries for everyday use.
Different places are also currently trying to make Piezoelectric roads into a real-life feature. Piezoelectric asphalts used to provide electrical power to street lights was tested in Hefer intersection, Israel. The set up involved piezoelectric devices underneath asphalt roads, at a total distance of 10 meters. The setup generated an average electrical power of two Kilowatt-Hours.
Another test has been conducted by POWERleap, a licensed technology manufacturer, has provided data proving the reliability of piezoelectric asphalts. The experiment involves 1 Kilometer stretch Piezoelectric asphalt with vehicles passing at a rate of 200-400 in 16 hours. Based on this experiment, the total electrical energy generated range anywhere between 400 Kilowatt-Hours to 600 Kilowatt- Hours. Since an average house uses around 900 Kilowatt-Hours, this means we could power tens, if not hundreds of houses for a month, just from a single day’s traffic.
Some useful factors for making the roads more effective include vehicle speed, weight and the traffic flow capacity. Contrary to this, tests showed that at a faster speed and velocity the output of power was greater. Different types of vehicles such as bus, car, and motorcycle were tested at a speed of 45 mph and 65 mph. Power was always greater with higher speed and greater weight. The higher speeds had a higher impact on frequency resulting in a higher decay creating a better AC voltage. As assumed by us, if there is more traffic going on this plate, there will also be a higher voltage.
- Quote paper
- Sumaanyu Maheshwari (Author)Nicolas McMahon (Author), 2017, Piezoelectricity, Harnessing Your Wasted Energy, Munich, GRIN Verlag, https://www.grin.com/document/382490