New Technology To Harvest Sun’s Energy With Antennas

Researchers at Idaho National Laboratory, along with partners at Microcontinuum Inc. and Patrick Pinhero of the University of Missouri, announced that they have developed a novel way to collect energy from the sun with a technology that they state could potentially cost pennies a yard, be imprinted on flexible materials and still draw energy after the sun has set.

The new technology uses a special manufacturing process to stamp tiny square spirals of conducting metal onto a sheet of plastic. Each interlocking spiral "nanoantenna" is as wide as 1/25 the diameter of a human hair. Because of their size, the nanoantennas absorb energy in the infrared part of the spectrum, just outside the range of what is visible to the eye. It is claimed that nanoantennas can take in energy from both sunlight and the earth’s heat, with higher efficiency than conventional solar cells.

The miniscule circuits absorb energy just like the antenna on a television or cell phone. All antennas work by resonance, the same self-reinforcing physical phenomenon that allows a high note to shatter glass. Radio and television antennas must be large because of the wavelength of energy they need to pick up. In theory, making antennas that can absorb electromagnetic radiation closer to what we can see is simple: just engineer a smaller antenna.

The real trick to making the solar nanoantenna panels is to be able to predict their properties and perfect their design before printing them in the factory. While it is relatively easy to work out the physics of one resonating antenna, complex interactions start to happen when multiple antennas are combined. When hit with the right frequency of infrared light, the antennas also produce high-energy electromagnetic fields that can have unexpected effects on the materials. So the researchers are developing a computer model of resonance in the tiny structures, looking for ways to fine-tune the efficiency of an entire array by changing factors like materials and antenna shape.

"At this point, these antennas are good at capturing energy, but they’re not very good at converting it," stated INL engineer Dale Kotter, "but we have very promising exploratory research under way." The researchers are also exploring ways to transform the high-frequency alternating current to direct current that can be stored in batteries. One potential candidate is high-speed rectifiers, special diodes that would sit at the center of each spiral antenna and convert the electricity from ac to dc. The team has a patent pending on a variety of potential energy conversion methods. They anticipate they are only a few years away from creating the next generation of solar energy collectors.