Jan
8
A Nano Technology Payoff That Should Be Huge
January 8, 2008 |
Nano solar radiation collectors were awarded two Nano50 Awards to the research team at Idaho National Laboratory and partners Microcontinuum, Inc. and the University of Missouri. The approach uses a novel manufacturing process to stamp square spirals of conducting metal onto plastic sheets. The spirals are 1/25th the diameter of human hair.
The spectacular aspect is the range of sunlight these tiny collectors can absorb. With sunlight ranging from frequencies of 0.3 to 400 THz these collectors are more properly described as solar antennas. Al Fin’s post sets out the potential more fully than the original news story that came from the Idaho National Laboratory. The team led by Steven Novak and Patrick Pinhero estimate that collecting solar energy based on the radiation energy by antenna can absorb up to 80% of the available energy and while the working area cools after sunset the antenna will continue to work as the surrounding materials release the absorbed infrared energy.
At the earth’s surface infrared radiation is a large part of the net solar spectrum. The atmosphere clears off a substantial part of the high frequency energy making the gathering of the near visible infrared a key to high efficiencies. This property of the nano solar antennae makes the working period much broader, including more collection during overcast days, and into the night as the infrared is re radiated back.
Antennas operate by resonance, a phenomenon one can see when the frequency of a high pitched note shatters a “glass antenna.” The antennas we see, like the cell phone, television, and WiFi are larger to match the length of those frequencies. Infrared, so much smaller, needs engineering to devise antenna sizes to work cheaply and in size that can grasp the energy available in shorter lengths. Novak says “It’s not that this concept is new, but the boom in nano technology is what has really made this possible.”
The team’s innovation has been developed to lay 10 million antennas on 15 cm (6 inch) circles of plastic sheeting. The goal is to produce the antenna-laden film like a foil or plastic wrap. Impressive, indeed.
An array of nanoantennas, printed in gold and imaged with a scanning electron microscope. The deposited wire is roughly a thousand atoms thick. A flexible panel of interconnected nanoantennas may one day replace heavy, expensive solar panels.
The next step is to tune the nano antennas and perfect the properties before mass printing. The team offers that it is easy to work out the physics of one antenna yet when antennas are combined in close proximity complex interactions occur such as high-energy electromagnetic fields from certain infrared frequencies that can also affect the materials. The research is now focused on computer modeling to find the ways tuning can take out the problematic electromagnetic fields and gain further efficiency. Novak offers that small tweaks in things like antenna shape and materials can make big differences.
Another issue is that the electrical potential comes from the antenna arrays in very high frequency alternating current, some ten thousand billion times a second. Compared to the 50 or 60 alternations per second we’re familiar with in commercial grid current that seems to be quite a problem. The team is exploring ways to slow that alternating rate down using such ideas as embedding conversion devices such as capacitors directly into the nano antenna array. Another candidate is a high-speed rectifier, a form of diode that could be placed at the center of each antenna and make a conversion to direct current. Dale Kotter, an INL engineer says, “we have very promising exploratory research underway.” The news report states that patent applications are pending on a variety of energy conversion methods.
While there are these early issues to be worked out, the prospect of collecting solar energy by grasping the energy of the radiation rather than the photons offers a very different and more complete solar efficiency. It will take some time to engineer the solutions to the issues, find and solve what other matters might arise and formulate low cost manufacturing. Quoting Al Fin “People will naturally move away from fossil fuels for the same reason they moved away from gas street lights and whale oil lamps. Because a better alternative came along.”
This is one of the best examples of innovation I’ve seen in some time. The connection of nano printing and material sciences, combined with the realization that gathering the energy in the frequency of solar radiation is a revolution in solar energy. We are much closer than one might think to choosing a product that will make a huge difference.
Comments
10 Comments so far
You wrote the article that I was trying to write. Nice job!
I am especially intrigued with approaches to harvesting “waste heat.” Conventional thermoelectric devices and advanced cycle heat engines can grab “conducted” heat. These nanoantennas can convert radiated heat.
My slogan is “fight back against entropy!”
[...] For a couple days I have been just haunted, yes, haunted by an insight by Al Fin and his commenters on the nano antenna array we both covered early this week. [...]
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Offhand, their proposed device seems to defy the second law of thermodynamics. More information is needed. Where is the increase in entropy? Do these things radiate even longer wavelength photons? It is implied that you could stick one in a beaker of water and the water would freeze while electric power is extracted. The universe does not work that way.
More thoughts: Why bother with the antennas? If you can get diodes with such low forward voltage the thermal motion of the electrons would be sufficient to drive them through these magic one way valves. Maxwell’s demons cannot function and never will.
Perhaps if infrared black body radiation was low entropy coherent radiation like radio or microwave transmissions some form of this system might work. Otherwise, one cannot defy the 2nd law of thermodynamics.
I think the idea is that the antennas are still room temperature compared to the radiating heat, but instead of the heat transferring to the antennas entirely as heat energy to create equilibrium, it converts 80% of the energy to electrical? It technically would not be trying to transfer heat energy from a cooler object to a warmer one, i don’t think. Still seems far-fetched, but amazing if true.
But it does not yet convert energy to electricity. IR is a very high entropy source of energy and useful energy can only be extracted from it as it flows into someplace cooler and you have a net increase in entropy. For example, one could use it to heat a boiler to generate steam to drive a turbine on its way to a cool condenser.
Thought experiment: If their device could work one could transfer heat form one body to another even if both started out at the same temperature and both were in an insulated box. Just run the electric power extracted from the first through a heating element on the second. This can not happen in our universe.