New technology can harvest \'lost\' energy, create electricity

An array of cells using inexpensive materials can capture microwave signals from sources like satellites or WiFi to create electrical power, U.S. engineers say. The power-harvesting technology, with efficiency similar to that of modern solar panels, can capture and utilized otherwise "lost" energy by converting the microwave signal to direct current voltage capable of recharging a cellphone battery or other small electronic device, scientist at Duke University reported Thursday. The key to the power harvester lies in its application of metamaterials, engineered structures that can capture various forms of wave energy and tune them for useful applications, the Duke team said. The engineers created a series of five fiberglass and copper energy conductors wired together on a circuit board to convert microwaves into 7.3V of electrical energy. By comparison, they noted, Universal Serial Bus (USB) chargers for small electronic devices provide about 5V of power. "It's possible to use this design for a lot of different frequencies and types of energy, including vibration and sound energy harvesting," graduate student Alexander Katko said. "Until now, a lot of work with metamaterials has been theoretical. We are showing that with a little work, these materials can be useful for consumer applications." For example, he said, a metamaterial coating could be applied to the ceiling of a room to redirect and recover energy from a WiFi signal that would otherwise be lost.