Metamaterials as a class get a lot of press for their ability to exhibit a negative refraction index, the characteristic that lets them bend light around a space or object (the much ballyhooed "invisibility cloak"). But designer metamaterials have potential reaching far beyond just visible light. They can be customized to have all sorts of tailored responses to radiation, and thanks to a Duke University research team, one of those responses could have a huge impact on thermophotovoltaics and other energy conversion schemes.
The team has demonstrated the ability to use metamaterials to engineer emitted "blackbody" radiation with an efficiency that surpasses the natural limits that should be imposed on the material by its temperature. In English, that means better energy conversion efficiency in things like photovoltaics and possibly waste heat harvesting.
A "black body" is an idealized material that absorbs all radiation that strikes it regardless of wavelength. It also emits that energy based on the material's temperature. Black bodies don't exist in nature, which is too bad because they are really efficient, in that they achieve a kind of equilibrium. What goes in as electromagnetic radiation comes out as thermal radiation (or "blackbody radiation"). Ideally speaking.
What the duke team has shown using metamaterials--man-made materials not found in nature--is that they can tailor that blackbody radiation in various ways, including in ways that defy the efficiency that a material would have naturally. Put another way, there is a natural limit on the radiation a given material can emit, and that limit depends on the material's temperature. But the Duke team has shown its metamaterials can emit radiation at efficiencies beyond what nature says they should be able to (more detail on the science behind this hereand here).
The takeaway: a new class of metamaterials could lead to technologies that can harvest waste heat from industrial processes or other heat emitters at unprecedented efficiencies (read: efficiencies that actually make such energy harvesting schemes worthwhile). Or they could lead to thermophotovoltaic cells that can tailor the emitted photons to match the band gap of the semiconductor on the cell, making energy conversion far more efficient.
If they can be designed to absorb ANY EM radiation, then they could construct effective shielding against Gamma and X-Ray radiation. The application of such materials could increase the efficiency of nuclear reactors, radiation protection for people and space vehicles, and energy cells that utilize gamma emitting isotopes like Pu and Co-60.
Nuts! Falconer beat me to the punch...
not to mention more efficient solar panels.
why learn from your own mistakes, when you could learn from the mistakes of others?
though that's a good idea, I think you would hit problems with heat. As the EM radiation is absorbed, it must be converted to heat.
solar panels would fall under thermophotovoltaic cells if i'm not mistaken...
@Breoghan, maybe this links will clarify things for you.
As soon as I started reading this article I wondered if they could make a material that absorbs all EM radiation. I got my answer :D
But I think I was confusing this with a material that bends EM radiation around it. If there was a material that could bend all EM radiation, we could be invisible from everything!
Don't mind me, just thinking out loud.
Falconer13 mentioned that this could be used for radiation shielding and energy production separately, but I wonder if there's a way to have the material do both at the same time. The negative effects of solar radiation on the human body in space are already well-documented, so if we ever want to go colonizing other planets, we're going to need proper radiation shielding no matter what. But what if instead of just shielding the riders of a spaceship against radiation, the shields also served to power the ship itself by absorbing the radiation and converting it to electricity? Plus, the only way we're ever going to get to other stars in one piece is with a reliable power source that will last the entire trip. That means either using fusion power or harnessing interstellar radiation. Maybe this is the first step toward achieving that goal. Awesome.
@marcopolo1613 We could not only convert some of the energy into electricity but the excess heat could be used to heat the space craft, last I heard it can get pretty chilly in space lol.
How about specialized shielding for space travel, and for both lunar and martian based settlements? I'm sure you've all read somewhere or another about the dangers of solar radiation, gamma and otherwise that is posed in both Lunar and Martian enviroments. Having a shield tailored to absorb these radiations, then convert that to heat and/or electricity... I mean, that's EXACTLY what we need to accomplish colonization of extraterrestrial locations...
Playing Devil's Advocate since 1978
"The only constant in the universe is change"
-Heraclitus of Ephesus 535 BC - 475 BC
Black body by definition is able to absorb and transmit all energy wavelengths. So by default it should be able to take huge bursts as a shielding, and retransmit the energy in a safer and efficient manor to power the system as well. 1 of many problems with the trip to Mars solved. That makes a couple, now we have radiation protection so our drunk astronauts can survive those harsh radiations while drinking down their wine to protect their bones. Can anyone say manned mission to Mars in the next few years.
Okay, "Wairimu", we will not pay any attention to you thinking out loud, but it would be nice to travel through space in a self-charging - self-contained spaceship that is invisible...run low on power, just coast in close to a star and let your solar powered electric particle engine recharge. I wonder if NASA is paying attention to this article?
@bubbagump - also from wikipedia... "A conventional solar cell is effectively a TPV device in which the Sun functions as the emitter." - as was my understanding. thanks for the links tho!
If it was space fight you would want the heat to keep the cabin warm. Same with a regular jet.
I like the idea of using it for reactor shielding. A reactor is already hot so some extra heat want be hurting it. And if its getting to hot for a LWR use a Liquid Fluoride Thorium Reactor or a MSR (the far superior technology).
ok, the idea of using it as radiation shielding is good. But, this kind of shielding would only work for electromagnetic radiation (i.e. ultraviolet, x-ray, gamma). The radiation that poses the most threat to a nuclear station and spacecraft is particle radiation (i.e. neutrons, protons, electrons, and exotics). Ablative meta materials might be able to help by redirecting charged radiation, but the structure would eventually become compromised rendering the shielding useless. When you're radioactive samples have half lives of 10,000 years you need something permanent.