How is solar energy tapped for electricity?

Question

How is solar energy tapped for electricity?

Answer 1

They use photovoltaic panels.  They come in a wide range of sizes too.  I've seen them as small as 5 watts and as large as 208 watts.  The nice thing about pv panels is that you can use them to power your house and charge batteries at the same time, so by the time dusk rolls around your batteries are ready for the night.

Answer 2

You'd need to understand how a doped semiconductor works because the solar cell works on that principle.  You'd also need to know a little about quantum mechanics too, but I'll try and make it simple and to the point.

Based on the materials to make the basic semiconductor matrix (often silicon), you can put in half the matrix an impurity that is an element with one less electron (one Z down) and on the other half, one with an extra electron (one Z up).  So for example, you can have a matrix of silicon with aluminum as the p-type (for positive) impurity and arsenic as the n-type (negative).  The p-type impurity has one less electron for its atom, thus when the impurity arranges itself within the silicon lattice arrangement, there is a vacancy for an additional electron.  And likewise for the n-type, there is an extra electron w/ that atom.

Now, the fun begins.  In order for that extra electron to pass from atom to atom, it needs to be excited from the valence band of the n-type atom into a conduction band that is shared between all of the atoms.  There is a gap (which is considered forbidden by quantum mechanical rules) that the electron needs to jump, and it can do so if it is excited.  Photons (rays of light) can do that if they are of the minimum amount of quantum energy.  There is a direct proportional relationship between photon energy and light's wavelength, and the difference is Plank's constant.  (I will dispense w/ all the math here).

So anyway, through all sorts of previous research on semiconductors, many combinations of matricies and impurities have been created and the band gaps found to move those electrons from the n-type to the p-type impurities.  The two sides are touching, so an electric current can run from one side to the other.  Now, based on the frequencies of sunlight, we know what wavelengths there are, and we know what materials would respond to them.  So today's photovoltaic cells are a sandwich of several layers of semiconductors because we havn't found a combination that responds to all the energies of sunlight.  But we've made them pretty good and they get better with constant research.

So as the photons hit the electrons in the n-type impurities, the electrons jump into the conduction band and other electrons by the p-type impurity fall into the vacancies, and the resultant vacancies works their way back to the n-type impurities since those atoms can normally hold an extra electron. Thus a voltage is created and a current can be derived from that.