Contemporary innovation in the field of energy seems to be all about finding power in sources that are all around us, such as the sun and wind. Researchers at Pennsylvania State University have taken that idea one step further having found a way to harness electricity from thin air.
More specifically, the scientists have developed a method to harness electricity from ambient magnetic fields generated by everyday household appliances.
Reporting in the journal “Energy and Environmental Science,” they note home devices, and especially the cords that supply electricity to them, generate small magnetic fields that otherwise dissipate into the air around them.
The scientists have developed a new mechanism capable of harvesting this wasted magnetic field energy and converting it into enough electricity to power next-generation sensor networks for smart buildings and factories.
One of the study’s co-authors, Shashank Priya, professor of materials science and engineering and associate vice president for research at Penn State, says the device he and his colleagues developed “allows for achieving high power density under low amplitude magnetic fields.”
He and his team designed paper-thin devices, about 11/2 inches long, that can be placed on or near appliances, lights or power cords. They used a composite structure by layering two different materials together. One of these materials is magnetostrictive, which converts a magnetic field into stress, and the other is piezoelectric, which converts stress, or vibrations, into an electric field. The combination allows the device to turn a magnetic field into an electric current.
The devices have a beam-like structure with one end clamped and the other free to vibrate in response to an applied magnetic field. A magnet mounted at the free end of the beam amplifies the movement and contributes toward a higher production of electricity.
In testing, when placed 4 inches from a space heater, the device produced enough electricity to power 180 LED arrays, and at 8 inches, enough to power a digital alarm clock.
According to the scientists, the technology has implications for the design of smart buildings, which will require self-powered wireless sensor networks to do things such as monitor energy and operational patterns and remotely control systems.