How do solar panels work? Solar power explained

Solar panels harness the sun's energy to generate usable electricity. At a high level, solar cells absorb incoming sunlight to generate an electrical current through what's known as the "photovoltaic effect." This electrical current is captured by plates and wires and turned into a usable energy current that is sent to your home and appliances. In this article, we'll break down exactly how solar panels produce renewable energy for your home.

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 temperatures 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's core (the hottest part) is about 27 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.

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: How it works

The science of electricity generation 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 effect works through the following simplified steps:

1. Sunlight hits the solar cells, energizing electrons in the cells and setting them in motion

2. The electrons flow out of the junction between cell layers, creating an electrical current

3. Metal plates and wires capture the flow of electrons and generate electricity

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 percent 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 of 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.

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 used around the solar industry.

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 uses 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.

Other essential solar panel parts

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 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.

Generating an electric current is the first step of a solar panel working, but the process doesn't end there. Here's how solar arrays create a usable electricity system 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 power is converted to AC power when it passes through your solar inverter (or inverters if you're using a microinverter system). 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 electrical panel. 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 energy 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. Learn more about the net metering policy.

We've been talking about photovoltaic solar, or PV, in this article because it's the most common type of solar energy generation, especially for homes and businesses. But there's more out there - the sun is an energy source for multiple types of solar technology that work in different ways than traditional solar photovoltaic panels. Two of the most common alternative solar options that work differently than PV panels are solar hot water and concentrated solar power.

Solar hot water

Solar hot water systems capture thermal energy from the sun and use it to heat water for your home. These systems are made of a few major components: collectors, a storage tank, a heat exchanger, a controller system, and a backup heater.

In a solar hot water system, there's no movement of electrons. Instead, the panels transform sunlight into heat. The panels in a solar thermal system are known as "collectors" and are typically installed on a rooftop. They collect energy very differently than traditional photovoltaic panels – instead of generating electricity, they generate heat. Sunlight passes through a collector's glass covering and strikes a component called an absorber plate, which has a coating designed to capture solar energy and convert it to heat. This generated heat is transferred to a "transfer fluid" (either antifreeze or potable water) contained in small pipes in the plate.

Concentrated solar power

Concentrated solar power works in a similar way to solar hot water in that it transforms sunlight into heat. CSP technology produces electricity by concentrating solar thermal energy using mirrors. At a CSP installation, mirrors reflect the sun to a focal point. At this focal point is an absorber or receiver that collects and stores heat energy.

CSP is most often used in utility-scale installations to help provide power to an electricity grid and is an alternative to fossil fuel-based power plants.

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:

Can you run your whole house on solar power? 

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. 

Do you still have an electric bill with solar panels?

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 company. If you want to rely completely on solar energy, you will need to add solar battery backup to pair with your solar panels. 

Do solar panels work at night?

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 on cloudy days when solar panels aren't able to get the full benefit of a sunny day. 

How do solar panels work on a house?

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. 

If you want to reduce your carbon footprint and start saving money on electricity, you'll want to start off by comparing solar panel system quotes. This is where EnergySage can help: When you sign up for a free account on the EnergySage Marketplace, we provide you with custom quotes from installers in your area. So what are you waiting for? Get started with your own clean energy journey through EnergySage today!