How Do Solar Panels Work?
Solar panels are devices that collect solar energy and use photovoltaic cells to convert it into electricity. Through the photovoltaic effect, semiconductors create interactions between photons from the sun and electrons to generate electricity. Find out how the process works and what happens to the electricity it generates.
From solar energy to electricity: step by step
Each solar panel contains individual photovoltaic cells made of materials that can conduct electricity. This material is mostly crystalline silicon due to its availability, cost and long life. The structure of silicon makes it very efficient at conducting electricity.
When sunlight hits each PV cell, the photovoltaic effect is set in motion. The photons, or particles of solar energy, that make up light begin to loosen electrons from the semiconductor material. These electrons begin to flow towards the metal plates around the outside of the PV cell. Like the flow of water in a river, the electrons create a flow of energy. The energy flow is in the form of direct current. Most of the electricity that is used is in the form of alternating current (AC). Therefore, direct current has to be conducted via a cable to an inverter, whose job it is to convert direct current into alternating current.
Once the electrical current has been converted to alternating current, it can be used to power the electronics in a house or for storage in batteries. In order for the electricity to be consumed, it must be routed through the home’s electrical system.
The photovoltaic effect
The process of converting sunlight into electricity is known as the photovoltaic (PV) effect. A layer of light-collecting PV cells covers the surface of a solar module. A PV cell consists of semiconducting materials such as silicon. Unlike metals, which are large electrical conductors, silicon semiconductors allow just enough current to flow through them.
Electric currents in solar panels are created by loosening an electron from a silicon atom, which uses a lot of energy because silicon really wants to hold onto its electrons. Therefore, silicon cannot generate a large amount of electric power by itself. Scientists solved this problem by adding a negatively charged element such as phosphorus to silicon. Each phosphorus atom has an extra electron that it can easily donate, so more electrons can be easily released by sunlight.
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This negatively charged N-type silicon is then placed together with a positively charged P-type silicon layer. The P-type layer is made by adding positively charged boron atoms to the silicon. Every boron atom is missing an electron and it would love to get one wherever it can. By putting sheets of these two materials together, electrons jump from the N-type material to the P-type material. This creates an electric field, which then acts like a barrier that prevents electrons from moving easily through the field.
When photons hit the N-type layer, they release an electron. This free electron wants to get to the P-type layer but doesn’t have enough energy to get through the electric field. Instead, it takes the path of least resistance. It flows through metal wires that connect from the N-layer around the outside of the PV cell and back into the P-layer. This movement of electrons creates electricity.
Where is the current going?
If you’ve ever driven past a house with solar panels or considered buying them for your own home, you might be surprised to find that most solar homes still need electricity from a utility company. According to the Federal Trade Commission, a majority of homes with solar panels in the US get about 40% of their electricity from their modules. This amount depends on how many hours of direct sunlight your panels receive and the size of the system.
When the sun is shining, solar panels convert sunlight into energy. Often, when they produce more electricity than needed, that electricity is sent back to the grid and there is a credit on the electricity bill. This is known as “net metering”. In a hybrid system, people install batteries with their solar panels, and most of the excess electricity generated by the modules can be stored there. What is left is sent back to the grid.
With the gross measurement, all the electricity that is generated by solar modules for private households is immediately fed into the power grid. The residents then withdraw electricity from the grid. However, solar panels don’t always produce electricity. If the sun isn’t shining, homeowners may still need to plug in to get electricity. Then they are calculated by the energy supplier for energy consumption.