How do solar panels work?
Solar panels use the sun’s energy to generate usable electricity. At a high level, solar cells interact with incoming light to generate an electrical current through the “photovoltaic effect”. In this article, we’ll break down exactly how solar panels produce renewable energy for your home.
Key takeaways: how do solar panels work?
Solar cells are typically made from silicon, which is a semiconductor and can generate electricity through the photovoltaic effect.
Solar inverters convert direct current (DC) electricity produced by solar cells to usable alternating current (AC) electricity.
Other types of solar technology include solar hot water and concentrated solar power – they both use the sun’s energy, but through a slightly different mechanism than photovoltaics.
The science of how solar panels work: solar cells and the photovoltaic effect
In a nutshell, a solar panel works by generating 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, turning it into a usable electric current. This process is called the photovoltaic effect, and is the foundational chemical and physical process behind the vast majority of solar technology.
The photovoltaic effect explained
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 process of generating solar electricity starts with solar cells, the individual pieces that make a larger solar panel. Solar cells are usually made from the element silicon (atomic #14 on the periodic table). Silicon is a nonmetal semiconductor that can absorb and convert sunlight into electricity – we also use silicon in almost every computer on the planet. There are a few different types of semiconductors typically used in solar cells, and silicon is by far the most common, used in 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.
There are two layers of silicon used in photovoltaic cells, and each one is specially treated, or “doped”, to create an electric field at the junction between the layers. This electric field forces loose electrons to flow through the solar cell and out of the silicon junction, generating an electrical current. Phosphorus and boron are commonly used as positive and negative doping agents, respectively, to create the positive and negative sides to a photovoltaic cell.
Metal plates on the sides of each solar cell collect the electrons pushed out by the electric field, and transfer them to connecting wires. At this point, electrons flow as electricity through the wiring to a solar inverter and then throughout your home.
Where does solar energy come from?
The photons that reach your solar cells and generate an electric current come from somewhere – the sun. Solar energy is created by the constant nuclear fusion reactions occurring deep within the sun. Nuclear fusion in the sun happens when protons (which are essentially the same as hydrogen atoms) collide and fuse under extreme temperature and pressure to create helium. This process emits a massive amount of energy (plus more protons), and in the core of the sun, this reaction is constantly happening, producing over 500 million tons of hydrogen atoms every second.
The result? Our sun exists at a temperature around seven million degrees Fahrenheit, and is constantly emitting massive amounts of energy in the form of electromagnetic radiation (EMR). EMR exists in many forms, and the sun produces all types of EMR, carried to earth in the form of photons.
Alternatives to silicon solar cells
While silicon is the most common semiconductor used worldwide in solar panels, there are alternative options used in some new and emerging solar products.
Thin-film solar cells are a general category of solar cells made from lightweight and/or flexible materials. There are four main chemical types of thin-film solar cells: Cadmium Telluride (CdTe), Amorphous Silicon (a-Si), Copper Indium Gallium Selenide (CIGS), and Gallium Arsenide (GaAs). The light-absorbing layers in these types of cells are 350 times smaller than silicon cells, hence the name “thin-film”.
Organic solar cells are a separate type of thin-film solar cell that use carbon-based materials as a semiconductor. These types of organic photovoltaics (OPV) are also sometimes referred to as “plastic solar cells” or “polymer solar cells”, and are produced by dissolving organic compounds in ink and printing them onto thin plastics.
Perovskite solar cells are a third class of thin-film solar cells built out of perovskites, a class of man-made materials with a unique crystallographic structure that makes them highly efficient at converting photons of light into usable electricity. Perovskite cells are built using “solution processing”, which is the same technique used to print newspapers.
Alternatives to silicon solar cells
Aside from their solar cells, a typical solar module includes a few essential parts:
Panels have a glass casing that offers durability and protection for the silicon PV cells. Under the glass exterior, solar panels have an insulation layer and a back sheet, which protects against heat dissipation and humidity inside the panel. This insulation is important because increases in temperature lead to a decrease in efficiency, resulting in lower solar panel performance. Solar panels have an anti-reflective coating that increases sunlight absorption and gives the cells maximum sunlight exposure.
When it comes to silicon solar cells, there are generally two cell formations produced: monocrystalline and polycrystalline. Monocrystalline cells are made up of a single silicon crystal, whereas polycrystalline cells are made up of fragments of silicon. Monocrystalline 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.
How do solar panels generate electricity for your home?
Generating an electric current is the first step of a solar panel working, but the process doesn’t end there. Here’s how solar panels systems generate usable electricity for your home:
1. Photovoltaic cells absorb the sun’s energy and convert it to DC electricity
As explained above, the solar cells that make up each solar panel do the heavy lifting when it comes to actually generating electricity. Through the photovoltaic effect, your solar panels produce an electrical current.
2. Solar inverters convert DC electricity from your solar modules to AC electricity, which is used by most home appliances
DC electricity is converted to AC electricity when it passes through your solar inverter. 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 the converted AC energy to your home’s electric box. From there, electricity is dispersed through your house to all of your outlets, so that when your devices need to be plugged in, there is a usable electric current available.
4. Excess electricity produced by solar panels is fed to the electric grid
If you have a grid-tied solar system, electricity can run both to and from the power grid, and excess energy produced by your panels can actually make you money. Through a policy known as net metering, you receive credits from the power grid when you send electricity back to it, which makes your overall cost of electricity even cheaper.
What is a grid-tied solar panel system?
If you’ve installed a solar system, the majority of your electricity is probably coming directly from your system, assuming it’s sized appropriately. But what happens on a cloudy day or at night when the sun isn’t shining? Most homeowners still remain connected to their local electrical utility grid so they have access to an alternative electricity source – meaning their solar system is grid-tied. In fact, in most cases, unless you have a solar-plus-storage system, you’ll have to remain tied to the grid in order for your solar panels to work because they aren’t designed to consistently generate enough electricity to be a home’s only power source.
Frequently asked questions related to how solar panels work
Learning more about how solar panels work can be confusing at times, which is why making it simple and digestible is key. Now that you know more about how solar panels generate electricity and the science behind it, check out a few other questions that homeowners commonly ask:
The two main disadvantages of solar energy are its high upfront costs and intermittency. While investing in renewable energy pays off in the long run, this technology is typically more expensive than traditional energy generators when it comes to installation. Luckily, there are financial incentives, such as tax credits and rebates, available to help alleviate the initial burden. Additionally, intermittency can be an issue — renewable energy resources aren’t available 24/7, year-round. For instance, solar panels produce less electricity at night and on overcast days. There may be unpredictable weather patterns that impact the efficiency of solar panels, but you can consider battery options as a backup.
Yes, you can generate enough electricity for your entire house using solar power. The key is making sure your solar panels are operating at maximum efficiency by choosing the right type of panel, installer, and the best angle for your home and your needs. However, although a solar panel system can offset all of your energy usage, it’s not realistic to expect that level of production every day due to intermittency. Installing storage will help if you don’t want to rely on the grid when the sun isn’t shining.
Yes, if you’re connected to the grid, you’ll still receive an electric bill with solar panels – but it’s possible that you won’t owe anything. However, if your solar panels are not producing enough energy to meet your needs, or if you’ve increased your energy consumption since installation, you’ll likely still owe some money to your utility. If you want to rely completely on solar energy, you will need to add solar battery backup to pair with your solar panels.
While some electricity can be generated from other light sources at night, the output is very low because the cells in solar panels require sunlight. When solar panels are paired with solar battery storage, energy is stored throughout the day for use during evenings and even cloudy days when solar panels aren’t able to get the full benefit of a sunny day.
After determining the number of panels needed to power a home, panels are mounted to a south-facing rooftop and angled to get the full benefit of the sun. These panels then absorb sunlight and convert it into electricity and, for homeowners who opt to have a solar battery, store energy for cloudy days or night usage.
