Solar Antennae that Generate Power
Gathering Solar Energy via Nanoscale Antennae Developed in Idaho
A team at the Idaho National Laboratories has developed an innovative method to manufacture nanoscale antennae at the right size to capture energy from the sun.
It seems that everything is being miniaturized these days, and solar power is no exception. In the Input Output column in the March 2008 Mechanical Engineering magazine, Jeffrey Winters reports on work being performed at the Idaho National Laboratories to develop nanoscale antennae that are small enough to absorb energy from the tiny wavelengths of sunlight.
Solar Antenna Design
Unlike traditional methods to harvest energy from sunlight, such as photovoltaic cells or solar thermal systems, solar antennae react to the electric field caused by light waves, just as a car antenna reacts to the megahertz waves of FM radio. However, antennae must be sized based on the wavelengths of the particular waves being targeted. Until recently, it was simply not possible to create an antenna small enough to capture the small waves of sunlight.
Steven Novack and Dale Kotter at the Idaho National Laboratories have applied nano-manufacturing techniques to create antennae with a diameter of about one micrometer. The team has used a stamp and repeat technique to create a sheet of plastic containing over 260 million of these miniature solar antennae. The resulting sheets of antennae are thin and flexible, allowing them to be used in traditional applications such as roofing, but also in unconventional applications such as tents and clothing, anywhere where polyester fabrics can be used.
The antennae developed by the Idaho National Laboratories team are optimized for capturing light waves in the infrared range. This allows the antennae to capture direct waves from the sun during the day and radiated heat from the Earth long after the sun has set. Alternatively, these antennae could be used to capture heat from many other sources, such as computer servers.
Technical Challenges
Some challenges still remain. Automated production techniques must be developed, but the team anticipated that the cost of power from these antennae could be less than any other available source, including fossil fuels, once manufacturing has been optimized. Also, innovative modeling techniques have to be developed to accurately predict the behavior of not just one antenna, but arrays of millions of antennae. "The ability to model these antennas is what's going to make us successful, because we can't see these things," Novack says. "They're hard to manipulate, and small tweaks are going to make big differences."
The main technical challenge at this point is converting the light energy from its natural form of trillion-plus cycles per second to a useable 60 Hz frequency to match the existing grid. Potential conversion techniques could come from the growing field of optical computing.
Despite these challenges, the concept of an solar antenna shows immense promise. These antennae do not require the rare or expensive materials required for photovoltaics, and could truly provide an alternative energy source at costs that are on par with conventional energy sources.
Sources:
Winters, J., “PV Antennas”, Mechanical Engineering, March 2008
Idaho National Laboratory website
