• willowwoodweb2020

Some Science on Solar Cells

Updated: Mar 21

by WillowWood's Steve Taylor


So now that we’ve got solar panels…


How Do They Work?

In simplest terms, solar panels allow particles of light called photons to knock electrons free from atoms. These freed electrons then generate a flow of electricity.


Let's Talk About Electrons

Electrons are those nearly weightless, negatively charged particles that zip around the empty space surrounding the nucleus (the positive middle part made of protons and neutrons) of an atom. Electrons stay within a certain range of the nucleus because of their electromagnetic attraction (positives and negatives attract) to it. Removing an electron from its orbit requires energy to overcome that attraction. It's kinda like, if you wanted to kick the Earth out of its orbit of the Sun, you would need some energy...just a lot more.


Photovoltaic Cells

Solar panels are made of many smaller units known as photovoltaic cells. Each photovoltaic cell is made up of two layers of semi-conducting material (meaning electrons can move around in it) such as silicon. In order to produce electricity, a photovoltaic cell needs to create an electric field. Similar to a magnetic field, this is established by opposing poles, created when opposite charges are separated (+ goes one way, - goes the other way).


To create an electric field, manufacturers imbue the silicon wafer with other materials, giving each layer either a positive or a negative charge. Phosphorus is added to the top layer, imparting extra electrons with a negative charge to it (N-type silicon). The bottom layer is infused with boron (P-type silicon), which results in fewer electrons being added and therefore creates an opposing positive charge. This separation of charges creates an electric field in the space between the silicon layers. When a photon of light strikes the photovoltaic solar cell, it frees an electron. These freed electrons are then set into motion by the electric field within the silicon wafer.


“All that glitters may not be gold, but at least it contains free electrons.”

-- John Desmond Bernal


Electricity

To turn these electrons into usable power, metal conductive plates on the sides of the photovoltaic cells collect the electrons and transfer them to wires and establish an electric current. The strength of the current determines how much electricity each cell can produce.

Unfortunately, the electricity generated at this point is direct energy (DC) and needs to be converted to usable alternating current energy (AC). This is accomplished using a solar inverter (akin to a transformer). A wire then transports the AC electricity from the inverter to the breaker box, which distributes the electricity throughout the building as needed. Any electricity that is not used can be stored in an on-site battery or allowed to flow back into the utility electric grid. Voila!


“When there is a huge solar energy spill, it’s just called a nice day.”

--www.votesolar.org