Solar Energy

Stratton Harrison

Chemistry 111

5/5/16

Solar Energy

One of the ways we absorb the sunlight and turn it into usable energy is through devices called photovoltaic cells. The main component of these sells is elemental silicon. However, this is not pure silicon. The silicon is “doped” with other elements in two different ways. The first way is adding a small amount of arsenic to the silicon. Silicon has four valance electrons which will bond with four electrons from the Arsenic to create a full outer shell. However, Arsenic has five valance electrons which leaves one at liberty to freely move making it negatively charged. They call this an n-type semiconductor. The other method creates a positive charge making it a p-type semiconductor. Boron, which only has three valance electrons added to the silicon creating a shortage of one electron leaving a positive charge.

These two types of semiconductors join together to form the photovoltaic cell. Electrons flow between the positively and negatively charged regions. When sunlight hits the surface, the electrical flow starts. But because of a barrier created between the p-type and n-type silicon due to holes being filled with electrons at the junction, the electrical flow goes through a circuit connecting the two semiconductors. 

Though other types of energy have been used for longer periods of time such as coal and natural gas. An oxidation-reduction reaction occurs when the coal is burned. The Carbon in the coal forms into Carbon dioxide and soot which is essentially unburned carbon. Natural gas is a lot cleaner to deal with than coal. Mostly comprised of methane, it also creates and oxidation-reduction reaction when burned. The end results from the reaction are Carbon dioxide, water and heat. 

The Energy Return on Energy Invested (EROEI) for solar energy is significantly higher than both natural gas and coal. I see that solar energy is not only more efficient but is also gaining in popularity and usage. A lot of labor goes into obtaining the fuels: natural gas and coal. Also once the substance is burned and the energy is obtained, the fuels are worthless and cannot produce any more energy. The photovoltaic cells on the other hand can continually be used to create more energy. Sunlight is natural and can be obtained effortlessly; all that needs to happen is that the solar cells be put in place. This greatly helps to explain why the difference in EROEI between the two types of energy.