By Matthew Palmer

Tesla determined the best way to distribute electricity was to beam it around the world. Nikola Tesla – one of the top researchers on the issue at the time - had difficulty imagining wires extending into every city, building, and room. With the discovery of electricity in the late 19 th century, inventors were in a race to determine the best possible way to distribute it around the world.

Tesla began drawing up plans for a tower that he claimed could distribute power to points kilometers away. Construction of the 57 meter tall tower began on Long Island, although it was eventually halted when funding for the project ran out. Unfortunately, the tower was never completed and the world began to wire up…

The idea of wireless power was put to rest after the world became accustomed to having wires around their daily lives. Then, a few years ago – a man by the name of Marin Soljačić was awoken by his cell phone, which emitted a loud beeping noise indicating that it had low battery life and needed to be charged. Soljačić wished the cell phone would begin automatically charging as soon as it was brought into the house. He resurrected Tesla’s idea of wireless power and began to research ways to transmit power wirelessly. He thought of three possible ideas…

Although Soljačić brought back Tesla’s idea of wireless power, he looked into midrange ways that could charge or power devices when they were brought into the vicinity of a power source. Soljačić first thought of radio waves – which could effectively transmit information through the air. Unfortunately, he found most of the energy was lost in space and wouldn’t be a viable solution to the wireless power problem.

Since radio waves didn’t work, Soljačić turned to the possibility of lasers to transmit power wirelessly. Soljačić determined that lasers too would not work because they require a clear line of sight and therefore would eliminate the “wireless” part of wireless power. Lasers could also possibly have harmful effects on anything in their path.

Soljačić eventually decided that resonant coupling was the only logical answer to his problem. Resonant coupling is when two objects that are tuned to the same frequency can exchange energy. Not only this, but it can travel through walls and has little to no effect on the environment and human beings. Working with two MIT physics professors, Soljačić designed a system that powered a 60 watt light bulb.

Soljačić’s resonant coupling set up consisted of two copper coils hung from the ceiling at a distance of about two meters. If one coil was plugged into the wall it would create a magnetic field that resonated with another copper coil that was plugged into a light bulb. (or possibly other objects as seen in picture.) Soljačić and his team were able to successfully power the bulb even with a thin wall between the two coils.

1. Resonant copper coil plugged into an outlet. 2. Standard wall outlet. 3. Obstacle. (Thin wall between the coils) 4. Resonant copper coil that is attached to a light bulb.

The most effective set up consists of two copper coils that transmit energy at around 50% efficiency. Soljačić and his team are looking into silver coils, which would decrease coil size while boosting efficiency. According to Soljačić, "While ideally it would be nice to have efficiencies at 100 percent, realistically, 70 to 80 percent could be possible for a typical application"

Already, there a wireless power devices that make use of resonant coupling to charge themselves. The electric toothbrush uses resonant coupling to charge itself. However, the toothbrush must be in range of the device in order for the current to tunnel from one coil to the other.

The Splashpower mat is a device that can charge multiple low power devices at once as long as they are in contact with the mat. Unfortunately, the idea never really took off due to the fact that the devices either had to be compatible with the mat or modified so they can be recharged.

As more and more research on wireless power is conducted, the possibilities of a future without wires is looking brighter every day. Devices would no longer require wires and could be powered just by being in range of a wireless power device. Imagine never having to worry about charging your cell phone, mp3 player, or laptop. Intel is currently working on their own version of wireless power similar to Soljačić’s that would finally make devices like laptops truly “wireless”.