Revolutionary, Unique Solar Energy Nano-Antenna: 10 Trillion Hz AC! No Silicon!

Infrared radiation from the sun has a frequency of roughly 0.3 to 400 THz. Researchers from three labs: Idaho National Laboratory, Microcontinuum Inc. of Cambridge Mass, and University of Missouri, have developed a novel approach to harvesting infrared solar energy: stamped or printed gold nano-antennas that absorb EM radiation in the THz range! That means the energy is at a frequency much too high to be utilised, but crafty nano-circuits should be able to reduce the frequency of the harvested power to a manageable range.

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. The sun radiates a lot of infrared energy, some of which is soaked up by the earth and later released as radiation for hours after sunset. Nanoantennas can take in energy from both sunlight and the earth's heat, with higher efficiency than conventional solar cells.

"I think these antennas really have the potential to replace traditional solar panels," says physicist Steven Novack, who spoke about the technology in November at the National Nano Engineering Conference in Boston.

The miniscule circuits absorb energy just like the antenna on your television or in your 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.

But finding an efficient way to stamp out arrays of atom-scale spirals took a number of years. "It's not that this concept is new," Novack says, "but the boom in nanotechnology is what has really made this possible." The INL team envisions the antennas might one day be produced like foil or plastic wrap on roll-to-roll machinery.

The team estimates individual nanoantennas can absorb close to 80 percent of the available energy. The circuits themselves can be made of a number of different conducting metals, and the nanoantennas can be printed on thin, flexible materials like polyethylene, a plastic that's commonly used in bags and plastic wrap. In fact, the team first printed antennas on plastic bags used to deliver the Wall Street Journal, because they had just the right thickness.

By focusing on readily available materials and rapid manufacturing from inception, Novack says, the aim is to make nanoantenna arrays as cheap as inexpensive carpet.

...Although infrared rays create an alternating current in the nanoantenna, the frequency of the current switches back and forth ten thousand billion times a second. That's much too fast for electrical appliances, which operate on currents that oscillate only 60 times a second. So the team is exploring ways to slow that cycling down, possibly by embedding energy conversion devices like tiny capacitors directly into the antenna structure as part of the nanoantenna imprinting process.

"At this point, these antennas are good at capturing energy, but they're not very good at converting it," says INL engineer Dale Kotter, "but we have very promising exploratory research under way." Kotter and Novack are also exploring ways to transform the high-frequency alternating current (AC) to direct current (DC) 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.

Idaho National Lab

80% efficient capture of solar energy, able to generate power both day and night! It sounds like an energy revolution to me. Particularly since these nano-antennas can be produced so much cheaper than even the cheapest photovoltaic DC panels. This approach may take 5-10 years to fully develop, but when it is ready for commercial production, you may as well sell your stock in silicon PV.I have long predicted that the most likely "peak oil" scenario to play out, is the collapse of oil production resulting from cleaner and more economical energy alternatives. People will naturally move away from fossil fuels for the same reason they moved away from gas streetlights and whale oil lamps. Because a better alternative came along.

The idea of designing resonating nano-antennas to harvest solar energy was a good idea waiting for the technology to be developed. We are almost there.

Via Brian Wang