How Do Solar Panels Work? (Understanding Photovoltaic Systems)
Date Published: November 6, 2017
At Scott Home Inspection, we cover a broad amount of information during a home inspection. This means we can’t always go into specific detail about each system a home has installed. In the last few years, we have seen a large increase in the amount of homes that have a Photovoltaic (PV) or solar system installed. This is great for the environment and your energy bill, but it begs the question: How do solar panels work?
To answer this, our guest writer, Kyle P from the solar company PowerScout, is going to break down the technical aspects for you:
The PV Effect:
Solar panels cover the roofs of houses and businesses across the country. They convert sunlight into electricity through a process called the photovoltaic effect
(PVs). The PV effect is the process of generating voltage or electric current in a PV cell when it is exposed to sunlight. It is how the cells in the solar panel convert sunlight to electricity.
The PV effect occurs first in solar cells that are made up of two types of semiconductors, a p-type and an n-type, which are linked together to form an electric field. Electrons are knocked loose in both semiconductors when sunlight enters the cells. An external circuit, usually a thin wire that runs on the top of the n-type layer, allows the electrons to have a path to travel from the n-type layer to the p-type layer. The electrons that flow through the circuit are what provide the supply of electricity.
What is a Photovoltaic Cell?
PV cells are made to capture and convert sunlight into electricity that can power homes. One PV device is called a cell, which is typically small and produces about one or two watts of power. PV cells are connected in chains to form larger units that are called solar modules or solar panels in order to boost the power output. Modules can be connected to form solar arrays, which is connected to the electrical grid.
PV cells are manufactured from semiconductive materials like silicon. Semiconductors convert light into energy. Photons of light transfer energy to electrons when light is absorbed by a semiconductor, which allows electronics to flow as an electrical current through the material. When light hits a cell, part of it is then absorbed into the semiconductor material, and the energy of the light gets transferred to the semiconductor. That energy frees electrons, and the freed electrons flow into a current. The current and the electric field of the cell produces a voltage, and together that produces the electricity that powers a home.
Solar inverters take the direct current (DC) electricity from solar panels and use them to create alternating current (AC) electricity. They are a central part of any PV solar system. Inverters can do more than converting DC power into usable AC electricity. They can allow owners to see how well their system is working. There are several types of inverters.
String inverters get their name from the name for the rows of solar panels installed on a roof. Multiple strings of panels are connected to one string inverter. The DC power the panels produce is carried to the string inverter and converted into AC power. Microinverters are installed on each panel. Since they convert DC power to AC at the panel, a string inverter is not needed. The advantage to microinverters is that if a panel is shaded or not performing as well as the others, the performance of the other panels will not be affected. They also monitor the performance of each panel and can report this performance to the owner on solar production tracking software (e.g. an app).
What are solar panels made of?
Silicon is just one type of semiconductor material used in solar cells. It is the most commonly used semiconductor for solar cells, representing about 90 percent of the modules sold today, according to the Department of Energy. There are several reasons why silicon is used so commonly in solar cells. It is the second most abundant material on the planet. Solar cells with silicon as the semiconductor provide high efficiency, low cost and a long lifetime.
Cadmium telluride (CdTe) is the second most common material used in solar cells. Their use allows for low-cost manufacturing, but they are not as efficient. Copper indium gallium diselenide (CIGS) is also used in solar cells and has better electronic and optical properties. However, combining four elements is complex and makes it difficult to transition from the lab to manufacturing. Both CdTe and CIGS can be directly deposited into the front or the back of the solar module. They are considered to be thin-film photovoltaics, and account for about 10 percent of the global PV market.
Solar panels work for you and the future:
As you can see, the technology is complicated but the bottom line is that this is the technology of the future. The emerging advancements in PV systems are going to reshape the way that we power our homes. It is important for home owners and inspectors to understand these technologies. If you have any questions on this topic feel free to leave a comment below.
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Chris Scott is an ASHI certified home inspector with multiple years of experience in home inspections, blower door testing, duct leakage testing, and Boulder Rental License Inspections. Chris is also the Website Coordinator for Scott Home Inspection.