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Charging a cell phone

Charging a cell phone (CurvaBezier, iStockphoto)

STEM in Context

What If You Could Charge Your Phone Using Radio Waves?

Ellen Fritz

Summary

Could we use radio waves to charge electrical technologies in the future?

Your cell phone is dead. You forgot your portable charger at home. Anyway, you have no time to sit and wait for it to charge. 
You’re not alone. We’ve all been there! Luckily, scientists are finding new ways to charge devices without using a cord. For example, you may soon be charging your gadgets using the power of electromagnetic waves.

Electromagnetic Spectrum
The electromagnetic spectrum. Notice that gamma rays are on the far left side (Modified from an image by Inductiveload [CC BY-SA 3.0] on Wikimedia Commons).

It’s not a completely new idea. Inductive charging has been used in electric toothbrushes for more than 20 years. More recently, charging pads have entered the market. Users can charge their devices by just placing them on the pad. No need for a cable!

Of course, charging pads and electric toothbrush stands still need to be plugged into the wall. And they need to touch the device they’re charging. They don’t produce electrical energy on their own or send it through the air.

Discovery News explains the physics of wireless charging (3:49 min.).

 

Your devices run on electrical energy. Other forms of energy can be converted into an electrical current. For example, the turbines at hydroelectric generating stations harness the kinetic energy of flowing water.

This is similar to how potential energy is converted into kinetic energy. When you lift an object, you give it potential energy. When you drop the object, the potential energy is converted into kinetic energy as it falls.

Electricity is great for transferring energy from one place to another. After all, you don’t have to plug your gadgets directly into a waterfall! But you still need to find an outlet. The electricity grid connects outlets to an electricity generating station.

Electrical energy flows through the power cord into your device. There, it’s converted into potential energy that’s stored in the battery. The potential energy gets converted back to electrical energy to power your device. Eventually, you’ll need to transfer more potential energy into the battery. And the hunt for an outlet begins again!

Did you know? 

Most portable electronic devices like cell phones use lithium-ion batteries. This type of battery can hold a lot of energy or “charge.”

But scientists are studying sources of electrical energy that don’t depend on cords. For example, they are looking at ways of charging devices using electromagnetic waves. This is a type of energy constantly flowing through the air. Sonic Energy, Energous and Ossia are three companies researching wireless charging technology. 

Did you know? 

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

uBeam’s system uses ultrasound waves. You will still need to plug a transmitter into the wall. But your device’s power cord would be replaced with an internal receiver. The receiver would capture ultrasound frequencies produced by the transmitter. That would make it possible to charge your device without a power cable, dock or charging pad. 

Smartphone sitting on a charging pad
Smartphone sitting on a charging pad (NejauPhoto via iStockphoto).

Energeous is developing a wireless charging technology called WattUp. It uses radio waves instead of ultrasound waves. So far, it has been used to charge smaller devices, like hearing aids. Now, the company is testing WattUp with larger portable devices.


Ossia developed a wireless charging technology called Cota in 2018. The system uses high-frequency radio waves. Ossia hopes to start testing it in Walmart’s warehouses as early as 2020. If all goes well, it could soon be available to consumers. 


Technologies like these could provide a convenient source of energy. Imagine if your school was full of electromagnetic wave transmitters. They would wirelessly charge everyone’s devices. You would never have to worry about low battery power again! 


Research on producing electricity from electromagnetic waves has only just begun. But things are moving quickly. Wireless charging could soon be built into every home, school and workplace. Say goodbye to plugs!
 

Starting Points

Connecting and Relating
  • How do you feel when your phone is about to die or when it dies in the middle of a call? 
  • What is your routine with respect to charging your phone? How many cords and plug-in zones do you have around your house? 
  • What electronic devices would you like to be able to power wirelessly?
     
Connecting and Relating
  • How do you feel when your phone is about to die or when it dies in the middle of a call? 
  • What is your routine with respect to charging your phone? How many cords and plug-in zones do you have around your house? 
  • What electronic devices would you like to be able to power wirelessly?
     
Relating Science and Technology to Society and the Environment
  • How would a widespread transition to wireless charging impact on society and the environment? 
  • What benefits do large corporations, like Walmart, see in investing in wireless charging technology? 
     
Relating Science and Technology to Society and the Environment
  • How would a widespread transition to wireless charging impact on society and the environment? 
  • What benefits do large corporations, like Walmart, see in investing in wireless charging technology? 
     
Exploring Concepts
  • What energy transformation is taking place in inductive charging? 
  • What is the role of the battery in your mobile devices? 
  • Which forms of potential energy are being considered for “completely” wireless charging applications? 
  • What is the difference between ultrasound waves and radio waves? How would charging systems using these different waves differ? 
     
Exploring Concepts
  • What energy transformation is taking place in inductive charging? 
  • What is the role of the battery in your mobile devices? 
  • Which forms of potential energy are being considered for “completely” wireless charging applications? 
  • What is the difference between ultrasound waves and radio waves? How would charging systems using these different waves differ? 
     
Nature of Science/Nature of Technology
  • Aside from developing the science and technology behind a product, what other factors can influence the progress of a product, such as a phone that can be wirelessly charged, from a prototype to becoming a commercially available product? 
Nature of Science/Nature of Technology
  • Aside from developing the science and technology behind a product, what other factors can influence the progress of a product, such as a phone that can be wirelessly charged, from a prototype to becoming a commercially available product? 
Media Literacy
  • Have you seen advertisements for charging one phone from another phone? In electrical terms what type of charging are these ads promoting? How are there products being labelled or trademarked by corporations? 
  • How would you market a wireless charger? 
     
Media Literacy
  • Have you seen advertisements for charging one phone from another phone? In electrical terms what type of charging are these ads promoting? How are there products being labelled or trademarked by corporations? 
  • How would you market a wireless charger? 
     
Teaching Suggestions
  • This article can be used to support teaching and learning of Physics, Technology & Engineering, Electricity, Waves, Sound and Light related to sound waves, electrical technologies, electricity generation, electricity transmission, energy sources and energy transformations. Concepts introduced include inductive charging, electrical current, kinetic energy, potential energy, electricity, battery, heat energy, transmitter, receiver, radio waves, high-frequency electromagnetic waves and renewable energy. 
  • After reading the video and watching the embedded video, teachers could have students complete a Concept Definition Web learning strategy for the concept of wireless charging. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • After reading the article and watching the embedded video, teachers could have students consider the advantages and disadvantages of wireless charging, using a Pros & Cons Organizer learning strategy. Ready-to-use Pros & Cons Organizer reproducibles are available in [Google doc] and [PDF] formats. 
  • To go further, teachers could have students look at the potential consequences of having everyone use radio waves for charging electronic devices, using a Consequence Mapping learning strategy. Ready-to-use Consequence Mapping reproducibles are available in [Google doc] and [PDF] formats. 
     
Teaching Suggestions
  • This article can be used to support teaching and learning of Physics, Technology & Engineering, Electricity, Waves, Sound and Light related to sound waves, electrical technologies, electricity generation, electricity transmission, energy sources and energy transformations. Concepts introduced include inductive charging, electrical current, kinetic energy, potential energy, electricity, battery, heat energy, transmitter, receiver, radio waves, high-frequency electromagnetic waves and renewable energy. 
  • After reading the video and watching the embedded video, teachers could have students complete a Concept Definition Web learning strategy for the concept of wireless charging. Ready-to-use Concept Definition Web reproducibles are available in [Google doc] and [PDF] formats. 
  • After reading the article and watching the embedded video, teachers could have students consider the advantages and disadvantages of wireless charging, using a Pros & Cons Organizer learning strategy. Ready-to-use Pros & Cons Organizer reproducibles are available in [Google doc] and [PDF] formats. 
  • To go further, teachers could have students look at the potential consequences of having everyone use radio waves for charging electronic devices, using a Consequence Mapping learning strategy. Ready-to-use Consequence Mapping reproducibles are available in [Google doc] and [PDF] formats. 
     

Learn more

Device harvests energy from low-frequency vibrations (2018)

Article by Walt Mills introducing another form of wireless charging that uses piezoelectric crystals in wearable fitness devices, which can cause an electric current when they change shape.

Energous Wireless Charging 2.0 (2018)

Promotional video (2:53) by the Energous Corporation explaining how their wireless charging technology works.

Cota™ by Ossia - Real Wireless Power (2016)

Promotional video (2:08) by Ossia Inc. explaining how their wireless charging technology works.

References

Mattson, B., & Newman, P. (2013, March). The electromagnetic spectrum. NASA.