As the cost of solar energy has plummeted in recent years alongside major improvements in technical efficiencies and manufacturing quality, many homeowners across North America are starting to look at solar as a viable renewable energy solution. And as solar enters mainstream energy markets, the big question is, “how do solar panels work?”.
In a nutshell, a solar panel generates electricity when particles of sunlight, or photons, knock electrons free from atoms, setting them in motion. This flow of electrons is electricity, and solar panels are designed to capture this flow, making it a usable electric current. This electric current is created by photovoltaic cells, and the components of those cells turn the electricity into usable power.
In this article, we’ll break down exactly how solar panels produce renewable energy for your home and how pragmatic going solar really is.
How do solar panels work? Step by step overview of the solar generation process
Solar power generation starts when solar panels absorb photons, or particles of light, with photovoltaic cells, generating this direct current (DC) energy and then converting it to usable alternating current (AC) energy with the help of inverter technology. AC energy then flows through the home’s electrical panel and is distributed accordingly. The main steps for how solar panels work for your home are:
1. Photovoltaic cells absorb the sun’s energy and convert it to DC electricity
Photovoltaic cells are treated with phosphorus and boron, giving them positive and negative charges conducive to carrying an electric current.
2. The solar inverter converts DC electricity from your solar modules to AC electricity, which is used by most home appliances
DC electricity becomes AC output when an inverter switches the direction of the current rapidly enough that it becomes AC power. Inverters can also be equipped with transformers that regulate the voltage of DC and AC currents.
3. Electricity flows through your home, powering electronic devices
Solar inverters transfer converted AC energy to your home’s electric box. From there, electricity is dispersed through your house by wires in the wall so that when your devices need to be plugged in, there is an electric current available.
4. Excess electricity produced by solar panels is fed to the electric grid
If you have a grid-tied solar system, energy runs both ways to and from the grid, and excess energy produced by your panels can actually make you money with a policy called net metering. Through net metering, you receive credits from the grid you are feeding your excess energy to, which makes your overall cost of electricity even cheaper.
How do solar panels generate electricity?
A standard solar panel (also known as a solar module) consists of a layer of silicon cells, a metal frame, a glass casing, and various wiring to allow current to flow from the silicon cells. Silicon (atomic #14 on the periodic table) is a nonmetal with conductive properties that allow it to absorb and convert sunlight into electricity. When photons interact with a silicon cell, it causes electrons to be set into motion, which initiates a flow of electric current. This is known as the “photovoltaic effect,” and it describes the general functionality of solar panel technology.
The science of generating electricity with solar panels all comes down to the photovoltaic effect. First discovered in 1839 by Edmond Becquerel, the photovoltaic effect can be generally thought of as a characteristic of certain materials (known as semiconductors) that allows them to generate an electric current when exposed to sunlight.
The photovoltaic process works through the following simplified steps:
1. The silicon photovoltaic solar cell absorbs solar radiation
More specifically, the semiconductor, which is not as effective in conducting electricity than metal, hence “semi”, absorbs light energy. There are a few different types of semiconductors typically used in solar cells. Silicon is by far the most commonly used semiconductor, making up 95% of solar cells manufactured today. Cadmium-telluride and copper indium gallium diselenide are the two main semiconductor materials used in thin-film solar panel production.
2. When the sun’s rays interact with the silicon cell, electrons begin to move, creating a flow of electric current
The wavelength of the light that shines on the PV cell plays a role in the overall efficiency it possesses.
3. Wires capture and feed this direct current (DC) electricity to a solar inverter to be converted to alternating current (AC) electricity
These wires are the grid-like lines you typically see on solar cells. The efficiency of a solar cell refers to how much electricity is picked up by these wires compared to the amount of sunlight that shines on the cells.
The science of solar panels, in depth
Silicon solar cells, through the photovoltaic effect, absorb sunlight and generate flowing electricity. This process varies depending on the type of solar technology, but there are a few steps common across all solar photovoltaic cells.
First, light strikes a photovoltaic cell and is absorbed by the semiconducting material it is made from (usually silicon). These incoming photons cause electrons in the silicon to be knocked loose, which will eventually become the solar electricity you can use in your home.
There are two layers of silicon used in photovoltaic cells, and each one is specially treated, or “doped”, to create an electric field, meaning one side has a net positive charge and one has a net negative charge. This electric field causes loose electrons to flow in one direction through the solar cell, generating an electrical current. The elements phosphorus and boron are commonly used to create these positive and negative sides to a photovoltaic cell.
Once an electrical current is generated by loose electrons, metal plates on the sides of each solar cell collect those electrons and transfer them to wires. At this point, electrons can flow as electricity through the wiring to a solar inverter and then throughout your home.
How does grid connection work with solar panels?
Though electricity generation with solar panels may make sense to most people, there’s still a lot of general confusion about how the grid factors into the home solar process. Any home that is connected to the electrical grid will have something called a utility meter that your utility company uses to measure and supply power to your home. When you install solar panels on your roof or on a ground mount on your property, they are eventually connected to your home’s utility meter. The production of your solar system’s renewable energy can actually be accessed and measured by this meter.
Most homeowners in North America have access to net metering, a major solar incentive that significantly improves the economics of solar. If you have net metering, you can send power to the grid when your solar system is overproducing (like during the day in sunny summer months) in exchange for credits on your electric bill. Then, during hours of low electricity production (such as nighttime or overcast days), you can use your credits to draw extra energy from the grid and meet your household electricity demand. In a sense, net metering offers a free storage solution to property owners who go solar, almost like a battery, making solar an all-in-one energy solution.
Additional important parts to solar panels
Aside from their silicon solar cells, a typical solar module includes a glass casing that offers durability and protection for the silicon PV cells. Under the glass exterior, the panel has a layer for insulation and a protective back sheet, which protects against heat dissipation and humidity inside the panel. This insulation is important because increases in temperature will lead to a decrease in efficiency, resulting in lower solar panel performance.
Solar panels have an anti-reflective coating that increases sunlight absorption and allows the silicon cells to receive maximum sunlight exposure. Silicon solar cells are generally manufactured in two cell formations: monocrystalline or polycrystalline. Monocrystalline cells are made up of a single silicon crystal, whereas polycrystalline cells are made up of fragments or shards of silicon. Mono formats provide more room for electrons to move around and thus offer a higher efficiency solar technology than polycrystalline, though they are typically more expensive.
