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How Do Solar Panels Work?

Rooftop solar panel

Solar panels are devices that collect energy from the sun and convert it into electricity. Semiconductors create interactions between photons from the sun and electrons to capture energy.

Learn how the process works and what happens to the electricity generated.

Solar Energy to Electricity: Step by Step

Solar energy is driven by the photovoltaic effect (PV), which captures energy from the sun. Each solar panel is organized into groups of PV cells, to create electricity by the following steps:

As the sunlight hits each PV cell, the photons, or solar energy particles, that make up the light knock electrons loose from the semiconductive material in the panels.

These electrons begin to flow toward the metal plates around the outside of the PV cell. Like the flow of water in a river, the electrons create an energy current in the form of direct current (DC) electricity.

Most electricity is used is in the form of alternating current (AC), so DC electricity has to travel to an inverter that changes DC to AC electricity.

Once the electrical current is changed into AC, it can be used to power electronics in a house or stored in batteries.

The Photovoltaic Effect In Depth

Electric currents in solar panels are made by knocking an electron loose from an atom of a PV material like silicon. This takes a lot of energy because silicon really wants to hold on to its electrons.

Unlike metals which are great conductors of electricity, silicon semiconductors allow controlled electricity to flow through them.

Silicon cannot generate much of an electric current on its own. Scientists solved this problem by adding a negatively charged element like phosphorus to silicon.

Each atom of phosphorus has an extra electron, so more electrons can easily be knocked loose by sunlight. 

CROSS SECTION OF A SOL AR CELL

This negatively charged, or N-type, silicon is then sandwiched together with a positively charged, or P-type layer of silicon. The P-type layer is made by adding positively charged boron atoms to the silicon.

Boron’s Role in the Photovoltaic Effect

Each boron atom is “missing” an electron, and would love to get one from wherever it can. Putting sheets of these two materials together causes electrons from the N-type material to jump over to the P-type material. This creates an electric field, which then acts like a barrier that keeps electrons from easily moving through it.

When photons hit the N-type layer, they knock an electron loose. That free electron wants to get to the P-type layer, but it doesn’t have enough energy to make it through the electric field. Instead, it takes the path of least resistance. It flows through metal wires that make a connection from the N-type layer, around the outside of the PV cell, and back into the P-type layer. This movement of electrons creates electricity.

Where Does the Electricity Go?

According to the Federal Trade Commission, most solar-powered homes in the United States get about 40% of their electricity from their panels.That amount depends on factors like how many hours of direct sunlight the panels get and how many panels are in the system.

There are multiple ways to store and access solar energy, and most involve interacting with the traditional power grid.

Net Metering: This occurs when excess electricity is sent back to the power grid as a credit on electricity bills.

Hybrid System: These systems include batteries, where the electricity that isn’t immediately used by the house is stored. Whatever is left over will be sent back to the grid.

Gross Metering: In this system, all electricity that is produced by residential solar panels is immediately sent to the power grid.2 Residents then pull the power back from the grid. Depending on usage costs, which can vary depending on the time of day the electricity is needed, this can be less efficient when homeowners are charged by the utility company for the energy consumed.  

Frequently Asked Questions

What are the three types of solar panels?

The three main types of solar panels are monocrystalline (the “purest,” made from a single crystal of silicon), polycrystalline (made from multiple fragments of silicon), and thin film (a flexible sheet composed of thin layers of photovoltaic material).

Do solar panels need direct sunlight?

Solar panels do not need direct sunlight, although they are most efficient in radiant sun. They can also produce energy on cloudy days or other times with the sun is not as strong.

Do solar panels work year-round?

Solar panels work during every season, though they’re most efficient in the summer, when the sun is most radiant and days are longest. Solar panels continue to work in the winter so long as the photovoltaic cells are not obstructed by snow and ice.

How long do solar panels last?

Solar panels last 25 to 30 years, but newer models claim to last even longer—up to 50 years.

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