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Solar panel

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A solar panel is a device that converts sunlight into electricity. It uses multiple solar modules made of photovoltaic (PV) cells. These cells use the photovoltaic effect to generate power. This process occurs when light hits materials that produce excited electrons. These electrons flow through a circuit to create direct current (DC) electricity. This electricity can power devices or be stored in batteries.

From a solar cell to a PV system
From a solar cell to a PV system

Solar panels are often grouped into larger arrays or systems. These systems are used for residential, commercial, and industrial needs. They are also essential for powering spacecraft in outer space.

To understand how they work, we must look at the cell construction. Most modules use wafer-based crystalline silicon cells or thin-film cells. The cells are connected electrically in series to increase voltage. They are then connected in parallel to increase current. This combination creates the total power of the solar panel. The power is measured in watts, which is voltage multiplied by current.

Actual output in volts, amps, and wattage from a 100 Watt Solar module in August
Actual output in volts, amps, and wattage from a 100 Watt Solar module in August

A PV junction box on the back acts as an output interface. Most systems also include an inverter. This device converts direct current into alternating current (AC) for standard use.

Smart Module
Smart Module

Manufacturers use different techniques to connect cells and improve efficiency. Early technology, called Aluminum back surface field (Al-BSF), used a full aluminum rear contact. Later, Passivated emitter rear contact (PERC) used a reduced aluminum face and a polymer film. This film helps capture more light. Newer Tunnel oxide passivated contact (TOPCon) uses smaller silver bus bars and an oxidation layer. Interdigitated back contact (IBC) moves all contacts to the back. This allows the entire front surface to capture sunlight.

Global photovoltaics market share by technology 1980-2021
Global photovoltaics market share by technology 1980-2021

Some advanced versions use tandem solar cells. These combine different cell chemistries to boost performance.

Solar technology has a long history of discovery. In 1839, Edmond Becquerel observed materials creating a charge from light. In 1873, Willoughby Smith discovered light could charge selenium. By 1881, Charles Fritts created the first commercial solar cell. It worked even in dim, diffused daylight. In 1939, Russell Ohl created a design used in modern panels. He patented this design in 1941. Finally, Bell Labs used his design in 1954. They created the first commercially viable silicon solar cell.

NREL PV Module Record Efficiency Chart
NREL PV Module Record Efficiency Chart

Solar energy has seen massive growth recently. Since 2010, the cost of solar photovoltaic electricity has fallen by 85%. Between 1992 and 2023, worldwide usage grew exponentially. From 2016 to 2022, production grew by about 26% annually. This means capacity doubles approximately every three years. By the end of 2022, global installed capacity reached 1,185 gigawatts (GW). This supplied over 6% of global electricity demand.

1975 – Price of solar panels as a function of cumulative installed capacity
1975 – Price of solar panels as a function of cumulative installed capacity

Lower costs help people in the Global South save money on fuel.

Different types of panels serve different purposes. Most modules use crystalline silicon, which made up 95% of production in 2021. Other markets use thin-film technologies like cadmium telluride. Bifacial cells are a special type that produce energy on both sides. They work best in high-albedo surroundings like snow. As of 2024, bifacial panels are leaders in utility-scale installations. For spacecraft, engineers use multi-junction solar cells. These are made of gallium arsenide and other semiconductors. They provide the highest power per kilogram for space travel.

Using solar power involves managing light and environment. The amount of light absorbed depends on the angle of incidence. Panels are often tilted to face the sun directly. Solar tracking mechanisms can adjust the tilt from dawn to dusk. This keeps the angle of incidence small to maximize energy.

EarthRangersCentre-ImageEnhancement
EarthRangersCentre-ImageEnhancement

Some modules use concentrators with lenses or mirrors. These focus light onto smaller, highly efficient cells. This can raise efficiency to around 45%. While solar is clean and renewable, it does require maintenance. Panels must be kept clean and depend on sunlight availability.

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File:Dji fly 20230602 13826 PM 27 1719032149374 photo optimized.jpg
Dji fly 20230602 13826 PM 27...
File:Photovoltaik Dachanlage Hannover - Schwarze Heide - 1 MW.jpg
Photovoltaik Dachanlage Hannover -...
File:From a solar cell to a PV system.svg
From a solar cell to a PV system.svg
File:Smart Module.png
Smart Module.png
File:Global photovoltaics market share by technology 1980-2021.svg
Global photovoltaics market share by...
File:Solar-Cell-IV-curve-with-MPP.png
Solar-Cell-IV-curve-with-MPP.png
File:UP-curve of partially shaded solar generator.png
UP-curve of partially shaded solar generator.png
File:Photovoltaic Diode Connections.png
Photovoltaic Diode Connections.png
File:NREL PV Module Record Efficiency Chart.png
NREL PV Module Record Efficiency Chart.png
File:Actual output in volts, amps, and wattage from a 100 Watt Solar module in August.jpg
Actual output in volts, amps, and wattage...
File:Variability of Solar Energy.jpg
Variability of Solar Energy.jpg
File:EarthRangersCentre-ImageEnhancement.jpg
EarthRangersCentre-ImageEnhancement.jpg

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