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How could we collect energy from gamma/x-rays instead of visible light which can be millions of times less efficient (compared to gamma/x-radiation)?

Since E = h * f, having left a solar panel at a sunny day for a little while would have consumed about 2.06775701e+12eV.

However, leaving the solar panel exposed to gamma ray for the exact same time, we would've consumed 4.13551402e+18eV, which is x2 million times more energy than the visible light frequency...

So, I created a simple diagram to explain how this could be done, and I want you to correct me if anything doesn't seem to work very well... enter image description here

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  • $\begingroup$ Why is collecting visible light less efficient? Less energy per photon perhaps, but usually more efficient to actually collect and use. $\endgroup$
    – Jon Custer
    Apr 3, 2017 at 22:24
  • $\begingroup$ Are you saying the cost of the transportation to set and build everything up etc. will be so big, that it would be more beneficial to harvest energy from visible light (the traditional way)? $\endgroup$ Apr 3, 2017 at 22:27
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    $\begingroup$ The sun emits far more energy in the visible then it does in the x-ray/gamma region of the spectrum (it is a pretty good black body). Next, the collection efficiency for a photon like a gamma that can travel a long way through matter is not good, since you don't know quite where it will be absorbed and create a huge avalanche of electron-hole pairs. So, you absorber has to be very thick, and that leads to other engineering issues that make it less efficient in getting the energy out. $\endgroup$
    – Jon Custer
    Apr 3, 2017 at 22:34
  • $\begingroup$ Maybe the sun emits more visible-light photons than gamma/x-rays, however how many times more? I bet not enough to exceed the energy that gamma ray providers compared to visible light, gamma ray photons contain a huge amount of energy compared to visible-light photons.. Also, can't the energy be sent to earth using microwave rectennas? I head something similar is being planned by NASA (see Suntower concept). $\endgroup$ Apr 3, 2017 at 22:38
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    $\begingroup$ You are on a physics website, so might be expected to look in to the physics of the problem a bit. (And, actually, there aren't many gammas produced by the sun at all - any that get made in the core nuclear reactions don't get out of the sun worth beans. Now, gammas arising from cosmic rays or interactions with the solar wind, mainly protons, are a slightly different story). $\endgroup$
    – Jon Custer
    Apr 3, 2017 at 22:59

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Yes there is a lot of energy being emitted by the Sun - solar wind, gamma rays, ... but I don't think it's a good idea to go into orbit to collect it.

The problem with solar energy is not one of "getting enough energy per unit area". The problem is "efficiently collecting energy so it can be used". Here "efficient" includes things like longevity. The radiation environment in space is BRUTAL: we are protected by the magnetic field of the Earth (for charged particles) and the atmosphere (for gamma) - without these, all life on Earth would fry. The same is true for most electronics - it would not take long for your gamma-energy collector to degrade. See for example this article.

The second problem is "getting the energy to Earth". It's expensive to collect energy in outer space and then sending it down.

The final problem is "putting your collector up there, and keeping it there". Launching any electronics into space is very expensive. Keeping it in orbit is expensive too - and forget about doing any maintenance.

Incidentally - your figure "2 million times more" is energy per gamma ray: but if you consider the Sun a black body radiator, the number of gamma rays is very much smaller than the number of visible light photons. That makes your idea not nearly as attractive as you think it is...

The energy distribution is given by Planck's law. Plotting it for a black body at 5777 K (roughly the surface of the Sun) you can see the relative intensity from the far UV on is much smaller than the intensity in the visible range:

enter image description here

I didn't even go all the way to the gamma end of the scale...

Of course the heart of the Sun is at higher temperatures and will contribute more gamma rays - but the relative flux is just not that big.

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  • $\begingroup$ As I responded to Jon, Maybe the sun emits more visible-light photons than gamma/x-rays, however how many times more? I bet not enough to exceed the energy that gamma ray providers compared to visible light, gamma ray photons contain a huge amount of energy compared to visible-light photons.. Also, can't the energy be sent to earth using microwave rectennas? I head something similar is being planned by NASA (see Suntower concept). $\endgroup$ Apr 3, 2017 at 22:41
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    $\begingroup$ The Planck Law plot is already in radiance - that is, energy per steradian per unit wavelength per unit area. So no - there is much more energy in the visible photons than in the gamma photons. $\endgroup$
    – Floris
    Apr 3, 2017 at 22:47
  • $\begingroup$ I see. What about X-Ray photons? The same principle applies? $\endgroup$ Apr 3, 2017 at 22:53
  • $\begingroup$ Yes - the curve "drops down steeply". The peak of the curve (note - I used log axes) tells you the wavelength at which you have the greatest energy density. The peak position is a function of temperature, given by Wien's Law $\endgroup$
    – Floris
    Apr 3, 2017 at 22:58

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