Have you ever wondered how solar works? On this blog, we’re going to discuss what it takes to make the sun’s energy produce AC voltage for your home.
Since the early 1900’s the United States has spent a crazy amount of money on the current infrastructure. This infrastructure supports mining, drilling, transporting, refining and distributing fossil fuels for our use. At the same time, the demand for energy has gone up steadily with the population. In the US, we get the majority of our power from coal, oil, and natural gas. Solar, Wind, Hydroelectric, and other renewables are starting to make a dent in the infrastructure, however. I think there is definitely hope for renewables in the future as a primary source of energy.
It’s hard to believe that the Earth absorbs over 173,000,000,000,000,000 watts of energy. That’s 173 thousand terawatts in a day, 10,000 times more sun than we need on any given day. Did you know 20 days of sunshine is all Earth needs to produce more energy than all the fossil fuels ever did on this planet combined?
Transforming light from the sun directly into electricity without any moving parts is science! It’s free, and when it’s not we won’t care, right? So how do we harness that potential energy and power our homes with it? It’s a process as predictable as the sun rising and setting every day. And there are no moving mechanical parts during the whole process. This makes solar technology so desirable because the technology will last for decades at a time.
So how do we take photons from the sun and get them to push the electrons on the solar panel in a manner that will create enough electricity to power our homes? It all starts with the PV cell. A single PV cell is the smallest component capable of this process.
The Perfect Element
Silicon solar cells are the most common type. Silicon, being the second most abundant element on earth, is perfect for this. The silicon is then sandwiched between two layers of conductive material. An atom within the silicon connects to other atoms with four strong bonds. This keeps the electrons stationary, so no current can flow.
A silicon PV cell is a semiconductor with two main layers, a positive and a negative. The positive side is doped with boron to give it a positive charge or extra electrons, and the negative side is doped with phosphorous to give it a negative charge. The junction where the positive and negative layer come together is called the P-N junction, and an electric field is created there. It generates a half (0.5) volt dc potential to travel through the cell from the P layer to the N layer, but not in the other direction. The connection between the P layer of one cell and the N layer of an adjacent cell increases the overall voltage, which is added in series.
Sunlight has particles of light shooting out from it, called photons. When a photon hits the solar panel hard enough, it knocks an electron from its bond, leaving a hole. The negative electron and location of the positively charged hole can then move around freely.
Since there is an electric field at the P/N junction, the electrons will only go one way. The electron gets pulled over to the N-side, while the hole gets pulled to the P-side. From there, this process repeats itself and does work like powering the house until the electrons return to a conductive aluminum sheet on the back of the panel.
Because the voltage of an individual crystalline PV Cell is only 0.5 v dc, a PV module consists of numerous cells, wired together in series. So, when 36 cells are wired in series, you should expect to get 18 volts DC. Unlike voltage, the current of the cell is dependent on the surface area, so the larger the panel the more voltage it can produce. In general, though, the current of each cell will be the same as the current of each module. The panels of yesterday were 18 and 36 cell panels. In 2019, our panels are 60-cell at the very least and go to 72 and 96 cell panels for the residential market. More cells mean more power per panel.
Monocrystalline vs Polycrystalline
Monocrystalline and Polycrystalline panels are your choices for your solar panels. Because of their efficiency and aesthetics, Monocrystalline panels are currently the most desirable. Typically a black panel and frame, these are made with a single type of crystal.
The single crystalline material used on Mono panels makes them more efficient than polycrystalline panels. They’re more efficient because they allow the electrons to move more freely. The reason they’re a tad bit more efficient than polycrystalline panels is due to the casting process of the cells.
Polycrystalline panels are made with a variety of crystals. So when the molten silicon of multiple types of crystals gets poured into the mold and solidifies, it dries flat into what looks like a bed of flakes or crystals. Polycrystalline panels have a bluish tinge to them too.
The different crystals within the cell create grainy speedbumps that can make it more difficult for the electrons to navigate out of the cell. Monocrystalline panels are smoother at that level. That’s the reason Monocrystalline panels are all the rage right now.
I hope this has helped you gain a little understanding of the process of solar energy production. If you’re in the Greater Sacramento area and interested in having Fox Family come out and give you a quote on your solar project just give us a call, or you can text us, too, at 916-877-1577.