First, let’s look at a simple introduction to how solar-powered electricity really works. If you’d like to dive into the more technical details of how solar works,skip down to Part 2.
1. How does a solar panel work to create electricity?
PV cells, or “photovoltaic cells,” are solar panels that are mounted on homes or on land that are busily absorbing sunlight and magically converting it into electricity.
A solar panel is basically a “silicon sandwich”. It has two layers of silicon sheets inside that work together to generate electricity. Similar to chemical-based batteries that have a positive and a negative side, solar cells inside a solar panel also have positive and negative sides. The bottom layer of a solar panel is positive, while the top layer is negative. When sunlight hits the solar panels, it activates a flow of electrons between the negative and positive layers, and it’s this flow of electrons that creates an electric current, streaming into the circuits of a home to supply everyone “free” electricity straight from the sun.
When solar panels are installed on a home, there is an inverter connected to the system that transforms the “DC” power, or direct current, from the solar panels into “AC” power, alternating current (the same form of electricity traditionally used in most houses in America).
Whereas one little D-size disposable battery would produce about one watt of electricity, one solar panel itself can produce 180 – 310 watts of electricity. Covering the average roof of a mid-sized house with solar panels could easily produce 4,000 watts or more of electricity.
2. Technical Overview: How solar works in electricity generation.
“How does a solar panel work?” Let’s take a closer look at what is inside the cells of a solar panel.
To top the solar panel is a layer of glass with an anti-reflective coating. This sheet of treated glass is important to help support the structure of the panels, protect the circuits from bad weather, and also allow plenty of light to pass through to the semiconductors below. Beneath the glass is the front contact, which is a sheet of metal that provides the necessary circuitry to direct the flow of electricity. There is also a metal contact layer of circuits directly on the bottom side of the solar panel. Between the two contacts, the thin silicon layers function as the semiconductors that power the whole system. Manufacturers treat the silicon so that the positive layer of silicon on the bottom has too few electrons, and the negative layer of silicon on the top has too many electrons.
As soon as we expose the panel to sunlight, the photons from the sun’s rays excite the electrons in the bottom, positive sheet and cause them to flow up into the negative silicon sheet and out around the panel’s circuit. Just like that, the ordinarily inactive silicon sheets become conductors and manufacturers of electricity. Let’s not forget that the top of the solar panel needs to have a transparent conducting film that’s helping to collect the current produced by the solar panel. While there are many different kinds of films depending on the solar panels used, some of the most common ones contain indium tin oxide, nanowire networks or other conducting polymers.
At this point, the solar cells have generated power in the form of a DC current. In order to make the electricity usable for homeowners, an inverter box needs to be installed to transform the DC power into AC power. Traditionally, the home has one inverter that converts power from all the cells at the same time.
A homeowner with a solar-panel system connected to the electrical grid doesn’t have to worry about power regulation or availability. The inverter will automatically relay excess power not consumed back into the grid for public use, and a credit is generated for all the power unused.
However, for self-reliant, or off-grid systems, careful calculations are required to determine the amount of power needed to set up batteries for storing power for future use, especially on days when there might not be much sunlight. That means, in order to convert to solar panels, a homeowner must calculate exactly how many watts per hour the home consumes on average. Then it’s possible to select the proper size and type of solar panels that will provide the home with the right amount of power. A charge controller will connect to the solar panels and regulate the power flow to a battery bank. The charge controller makes sure that batteries don’t become overcharged or damaged with any sudden surges of electricity. The charge controller is also the medium connecting the battery bank to the inverter, so the power is always flowing to the inverter as needed. Then from the inverter, power flows to the distribution panel and into the home for use.
If you’re interested in taking advantage of the sun’s free energy, contact the Go Solar Group for an energy audit & assistance.