Photovoltaic EM spectrum question?

[Der Anfang]

So, I might be wrong about this, but solar cells pnvert visible light into energy, right? It just dawned on me... if we can convert that ki.d of light into energy, what about the other wavelengths such as Radio or even Gamma? Would it be possible to build a photovoltaic device which could convert those into energy as well?

[_stilgar_]

Of course, you just need a substance that absorbs the waves of the frequency you want. It's hard with gamma, they pass through most stuff, but with radio waves it's super-easy. That's basically what your radio antenna is doing

[RainDreamer]

Not sure about the efficiency though...

[Shpaget]

Photovoltaics are not particularly efficient, either, yet are widely used.

[K^2]

It just dawned on me... if we can convert that ki.d of light into energy, what about the other wavelengths such as Radio or even Gamma? Would it be possible to build a photovoltaic device which could convert those into energy as well?

Not with photovoltaics. These have a limited range of usable frequencies. On the low end, PVs are limited by thermodynamics. You can't convert into electricity EM radiation corresponding to energies bellow temperature of the cell. At typical 300K we have here on Earth, that means nothing with wavelengths over 5 microns or so. That's well into IR, so radio is a no go under normal conditions, You might be able to get to microwaves with sufficient cooling, though.

On the high end, there is no strict limit, but you will start damaging the cell once you get to high enough energy. I don't know if converting gamma rays to electricity with PV is a way to go.

In principle, though, of course you can convert other EM ranges into electricity. Radio antenna converts radio waves into electricity. It's not a lot of electricity, so it still has to go through amplifier in the receiver, but nonetheless, that is precisely what it does.

[MinimumSky5]

The other thing to consider is that the sun emits most of its energy in the visible range, with some near IR, so getting energy from other ranges of the EM spectrum isn't very helpful even if it was possible with today's technology.

[PB666]

The other thing to consider is that the sun emits most of its energy in the visible range, with some near IR, so getting energy from other ranges of the EM spectrum isn't very helpful even if it was possible with today's technology.

THe IR isnt useful because E = hv. The gamma range has a background radiation the isnt derived from the sun, things like radon, potassium, iodine, etc give off a few hundred CPM, although these hv are relatively powerful you would have to many many times more to amount to anything, which lucky for us they dont. the actual dpm per cubi meter is much higher, you would have to go to considerable more effort to capture it. unlike the sun gamma comes from local matter so that the collector has to placed in the ground close to the highest source. What we do is take the most active earth, separate the most radioactive elements, purify them and place them in pellets and let the fission process create heat, causing steam to boil.

A photomultiplier tube is a device used to detect by amplifying an initial electric signal created by gamma rays. These are used in gieger counters and gamma counters.

[AngelLestat]

I am agree with all responces, in theory you can harvester energy from any wavelenght, but trying to absorb a bigger range of wavelenght will make your device more complex and costly, for what? if you know that the sun emit mostly of its energy in the visible range.

But well a good way to try to get a bigger range is looking for a true black body, nanotech may allow this without sacrifice much of simplicity.

[Der Anfang]

Not with photovoltaics. These have a limited range of usable frequencies. On the low end, PVs are limited by thermodynamics. You can't convert into electricity EM radiation corresponding to energies bellow temperature of the cell. At typical 300K we have here on Earth, that means nothing with wavelengths over 5 microns or so. That's well into IR, so radio is a no go under normal conditions, You might be able to get to microwaves with sufficient cooling, though.

On the high end, there is no strict limit, but you will start damaging the cell once you get to high enough energy. I don't know if converting gamma rays to electricity with PV is a way to go.

In principle, though, of course you can convert other EM ranges into electricity. Radio antenna converts radio waves into electricity. It's not a lot of electricity, so it still has to go through amplifier in the receiver, but nonetheless, that is precisely what it does.

That's interesting that you mention the use of Mircrowaves as being a source of energy. Supposedly, that's what scientists and engineers would use to transfer energy from solar satellites in orbit. The solarsats would collect the suns energy, then send a microwave beam to an earth based station to harvest the energy like that. Do I have my facts straight about that?

[Nuke]

alpha and beta voltaic devices exist, but these are very low power devices.

as i understand photovoltaics, they only convert a very narrow band of the visible spectrum. id be more interested in technologies that can either widen the spectrum absorbed or divert the appropriate spectra to an array of narrow band cells tuned to different wavelengths.

Edited August 16, 2015 by Nuke