Kid Friendly Science
Solar energy explained
Solar energy is energy captured from the sun. Photovoltaics are devices that harvest the energy of the sun and turn it into electricity. They are made from semiconductors such as silicon. When sunlight hits a photovoltaic it causes the electrons in the semiconductor to jump to a higher energy level and become excited electrons. The electrons are therefore absorbing the energy of the sun.
If we connect wires to the the negative and positive poles of solar panels it creates a circuit or track for electrons to flow. Once the electrons are excited by absorbing the sun's energy they can move. The movement of electrons around a circuit creates electricity.
Therefore, in solar cells we have the conversion of light energy into electrical energy. The electrical energy can now be converted into other forms of energy like motion or kinetic energy.
In the following video we see a kid scientist building a solar powered boat illustrating how light energy can be converted to electrical energy and then kinetic energy or motion.
Building a solar powered boat
Negative and Positive Layers
Solar panels typically have an n-doped and p-doped layers. Doping of the semiconductors involves introducing small amounts of impurities that cause them to become negative and positive.
Semi-conductors like silicon have two important energy levels called a valence band and a conduction band. The valence band is at the lower energy while the conduction band is higher in energy. The energy difference between the conduction band and the valence band is called the band-gap. Electrons typically stay in the valence band until they get excited by some external energy source.
Solar panels absorb sunlight because the silicon crystals have a band gap energy that matches the energy found in a photon of sunlight. When the sun is shining on a solar panel, the electrons sees amount of energy it needs to jump from the valence band to the conduction band, it absorbs that energy and gets excited and ready to do work.