Solar Flares

Silicon atoms have room for eight electrons in their outer bands, but only carry four in their natural state. This means there is room for four more electrons. If one silicon atom contacts another silicon atom, each receives the other atom's four electrons. This creates a strong bond, but there is no positive or negative charge because the eight electrons satisfy the atoms' needs. Silicon atoms can combine for years to result in a large piece of pure silicon. This material is used to form the plates of solar panels.

Here's where science enters the picture. Two plates of pure silicon would not generate electricity in solar panels, because they have no positive or negative charge. Solar panels are created by combining silicon with other elements that do have positive or negative charges.

Phosphorus, for example, has five electrons to offer to other atoms. If silicon and phosphorus are combined chemically, the result is a stable eight electrons with an additional free electron along for the ride. It can't leave, because it is bonded to the other phosphorus atoms, but it isn't needed by the silicon. Therefore, this new silicon/phosphorus plate is considered to be negatively charged.

In order for electricity to flow, a positive charge must also be created. This is achieved in solar panels by combining silicon with an element such as boron, which only has three electrons to offer. A silicon/boron plate still has one spot left for another electron. This means the plate has a positive charge. The two plates are sandwiched together in solar panels, with conductive wires running between them.

With the two plates in place, it's now time to bring in the 'solar' aspect of solar panels. Natural sunlight sends out many different particles of energy, but the one we're most interested in is called a photon. A photon essentially acts like a moving hammer. When the negative plates of solar cells are pointed at a proper angle to the sun, photons bombard the silicon/phosphorus atoms.

Eventually, the 9th electron, which wants to be free anyway, is knocked off the outer ring. This electron doesn't remain free for long, since the positive silicon/boron plate draws it into the open spot on its own outer band. As the sun's photons break off more electrons, electricity is generated. The electricity generated by one solar cell is not very impressive, but when all of the conductive wires draw the free electrons away from the plates, there is enough electricity to power low amperage motors or other electronics. Whatever electrons are not used or lost to the air are returned to the negative plate and the entire process begins again.

One of the main problems with using solar panels is the small amount of electricity they generate compared to their size. A calculator might only require a single solar cell, but a solar-powered car would require several thousand. If the angle of the solar panels is changed even slightly, the efficiency can drop 50 percent.

Some power from solar panels can be stored in chemical batteries, but there usually isn't much excess power in the first place. The same sunlight that provides photons also provides more destructive ultraviolet and infrared waves, which eventually cause the panels to degrade physically.

A solar, or photovoltaic, cell is used to convert energy in the form of electromagnetic radiation that is incident on it (ie that transfers light energy to it) into electrical energy.

The cell itself consists of 2 different types of doped semi-conductor material.

Doping is the process whereby impurity ions are introduced to the crystal lattice, with either one or fewer, or one extra free electron. Once doped, the materials are notelectrically charged.

In the P-type material, there are excess holes, and in the N-type material, there are excess electrons. When layered on top of each other, at the junction, the electrons fill the holes.

This means that on the P-side, there is a shortage of holes (as opposed to the number it would normally contain) so the material has a negative charge. On the N-side, there is a shortage of electrons, giving it a positive charge. This establishes a potential difference of 0.5V, but there is no current, as there are no free charge carriers at the junction.

When light shines on the cell, electrons are released by photons from the electron-hole pairs (photoelectric effect*), on the P-side of the junction. This alters the equilibrium at the junction. The electrons then flow to the positively charged n-type side, and the holes flow to the p-type side. This creates a current.

If there is an external, unbroken circuit attached to the cell, charge carriers are pushed through. As they go, they dissipate energy.

- If there is a greater light intensity, more photons are released per second, so there are more charge-carriers liberated per second, a greater current, and more power available.

* Particular frequencies of photons, or quanta of light energy, are absorbed by electrons so they have enough energy to move to a higher energy level/leave the surface of the metal.