Above: Image © CurvaBezier, iStockphoto.com

Your cell phone is dead and you have no place (or time) to sit and wait for it to charge. To top it all off, you forgot your portable charger at home. Now how will you plan your Friday night? We’ve all been there! Thankfully, scientists are developing new ways to charge electronic devices without any need for a cord. Instead, you may soon be able to charge your gadgets using the power of sound waves.

This idea is not completely new. Inductive charging has been used in devices like electric toothbrushes for over 20 years. More recently, some handheld devices have come with charging pads that you just place your gadget on top of, without having to plug a cable into the device. However, you need to place your electric toothbrush in its stand and charging pads still need to be touching your device. And they need to be plugged in, since they don’t produce the electrical energy your gadgets need on their own.

Did you know? Sound waves can be used to produce electricity.

The electrical energy your devices need to work is created by converting another form of energy into an electrical current. For example, at hydroelectric plants, the kinetic energy of flowing water is harnessed by turbines and converted into electrical energy. This is similar to how potential energy is converted into kinetic energy. When you lift an object and then drop it, you give it potential energy which is then converted into kinetic energy as it falls.

Electricity is particularly useful for transferring energy from one place to another. After all, you don’t have to plug your gadgets directly into a waterfall to charge them. But you still have to find an electrical outlet that is connected to a power plant through the electricity grid. This lets electrical energy flow through the power cord into your device. There, electrical energy from the outlet is converted to potential energy stored in the battery. It gets converted back to electrical energy to power your device and, over time, the energy available in the battery slowly fades. Eventually, you will need to put more energy into the battery, and the hunt for an outlet begins again.

But scientists are studying other sources of electrical energy that wouldn’t depend on cords. For example, the sounds you hear are actually produced by waves of energy flowing through the air. A team of researchers at the University of Utah used heat energy to create sound in long tubes that contained piezoelectric crystals. These are a type of crystal that naturally create electrical energy when they absorb the vibrations created by sound waves. In theory, you could use this method to charge your cell phone simply by yelling at it!

Did you know? Energy cannot be created or destroyed. But it can be converted to other forms and be reused over and over again.

Meanwhile, an inventor named Meredith Perry is developing a product called uBeam. It doesn’t entirely remove the need for a wall outlet, since it includes a transmitter that you need to plug in. But it does does replace the power cord with a receiver in the device. This receiver acts like a turbine, but instead of taking energy from falling water, it uses the vibrations from the sound waves produced by the transmitter. The electrical energy produced by the receiver can charge a device without a power cable, dock, or charging pad.

Beyond charging electronic devices, this technology could also provide a major source of renewable energy. Imagine if your school was full of sound wave generators that could be used to wirelessly charge your gadgets. You would never need to worry about low battery power! Or if excess heat could be used to create sound waves capable of powering an electric car.

Unfortunately, research on producing electricity from sound waves is still in its early stages. Large electrical generators powered by sounds are still a long way off. For now, Perry is aiming to have her first batch of wireless chargers ready by the end of 2015. When she does, I know I’ll want to be first in line!

Learn More!

News articles about research into using sound waves to produce electricity and power devices:

Mobile phones could be charged using sound(2014)
Ben Coxworth, Gizmag

Wireless Gadget Recharging with Sound Waves (2014)
Rachel Nuwer, Scientific American

Charging smartphones by soundwaves (2014)
Charles Pulliam-Moore, PBS Newshour

Ellen Fritz

For just over six years I was a senior Physics and Mathematics teacher in Saskatchewan. Through my division, I had many opportunities to explore Physics Education and Technology in Education as a teacher, as a technology coach, as a Physics 30 curriculum writer, and by completing an action-research based Master of Education program. I am currently working on a Ph.D. in Secondary Education at the University of Alberta with a planned focus on Physics Teaching and Physics Education research. 

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