Over the last few posts, we’ve covered the basics of wind turbines and geothermal energy. We’re going to be continuing this trend of renewable ELI5 basics with solar panels today. Mechanically what we see is, light hits the panel, ???, electricity. So what we’re really going to be focusing on is that middle step, the ???.
A solar panel is made up of a series of solar cells called photovoltaic cells, or PV cells for short. Solar cells function essentially as a p-n junction diode, but for our purposes we will just say that as sunlight hits the cell, photons, or light particles, knock electrons free from atoms. An electric current is created as electrons are traded between positively and negatively charged atoms. Very simply, imagine you and a friend each have a deck of playing cards and someone (the photon) bumps into you spilling both decks. The two of you will pick up the cards and then trade back and forth with each other (generate electricity) to have your two full decks again.
The actual construction of the cells is particularly important because specific components and elements are needed so that solar panels will work. You cannot just hook up jumper cables to an iron plate in the sun and expect it to charge your phone. Solar panels are constructed out of two silicon panels which are infused with additional elements that help generate either a negative or positive charge to each, thus incentivizing the transfer of electrons. The goal is to have a deck of 52 unique playing cards again. Two most common elements used for this are boron for the bottom layer which creates a positive charge, and phosphorous into the top layer, creating a negative electric charge.
As electrons get knocked out of place, they are collected by metal conductive plates at the edge of the solar panels and funnel them through wires that connect the two silicon layers. It is this transfer from one layer to the other that generates electricity. After that the work of the solar panel is done and the electricity is carried off to an inverter which transforms the direct current to alternating current which is what we use in our homes.
This process sounds and is complicated, but we should also look at why it is valuable to understand. In 2019, the capacity of the entire solar grid in the United States surpassed 71.3 gigawatts, that is over 1.5% of electricity used in the country. That may not sound like a lot right now, but that number is only growing and the U.S. Energy Information Administration projects that solar will be the fastest growing renewable energy source until 2050.
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