Solar panel

A solar panel is a device that converts sunlight into electricity by using multiple solar modules that consist of photovoltaic (PV) cells. These PV cells are made of special materials that create excited electrons when light shines on them. The electrons move through a circuit and make direct current electricity, which can power devices or be stored in batteries.

Greencap Energy solar array mounted on brewery in Worthing, England

Solar panels are often placed in groups called arrays or systems. A full photovoltaic system includes one or more solar panels, an inverter that changes the electricity from direct current to alternating current when needed, and sometimes other parts like charge controllers or solar trackers to get the most sunlight. Many panels are found in large areas called solar farms or on the roofs of houses as rooftop solar panels, helping to supply power to the electricity grid.

Solar panels are important because they use a clean and renewable energy source from the sun. They help reduce greenhouse gas emissions compared to energy made from fuels like coal or oil. Even though they need sunlight to work and can be costly at first, solar panels are used in homes, businesses, factories, and even in space with batteries for storage.

History

In 1839, a scientist named Edmond Becquerel discovered that certain materials could create an electric charge when exposed to light. This was the first step toward creating solar panels. Later, in 1881, an inventor named Charles Fritts made the first solar cell, but it was not very efficient.

In 1954, scientists at Bell Labs created the first practical solar cell using silicon. Since then, solar energy has grown very quickly. The cost of solar panels has dropped a lot, making it more affordable for many people around the world. Today, solar energy is used in many places, helping to power homes and businesses without needing to burn fossil fuels.

Theory and construction

Efficiency

Performance and degradation

Solar panels are tested under specific conditions to measure their performance, such as sunlight strength, temperature, and angle. Their output changes throughout the day and year depending on where they are placed, the weather, and other factors. To work best, solar panels should face the sun directly and be connected in groups that have similar electrical qualities.

Temperature affects how well solar panels work. Cooler temperatures can sometimes help them produce more power, but cold weather also brings challenges like snow and less sunlight. Over time, solar panels may lose a small amount of their ability to generate electricity, but they are built to last through various weather conditions. Different types of solar panels may lose power at different rates, but most still work well for many years.

Mounting and tracking

Main articles: Photovoltaic mounting system and Solar tracker

Large solar power plants often use solar panels placed on the ground, held up by special supports. These supports can be poles driven into the earth, concrete foundations, or weighted bases that don’t need to be dug into the ground. This is useful in places where digging isn’t possible.

Solar panels can also be placed on rooftops, held by frames that attach to the roof. Some rooftops even have special covers called solar canopies that provide shade and make energy too. Portable solar panels are flexible and can be used to charge devices when traveling or camping.

Solar trackers are special tools that move solar panels to follow the sun, which helps them make more energy. But some solar panels stay in one place, which is simpler and cheaper.

Maintenance

Solar panels can lose some of their ability to make electricity when dust, dirt, or pollen gets on them. This is called soiling. In places with a lot of dust, a dirty solar panel might work up to 30% less well. Cleaning solar panels can be a good idea in many areas, but in some places it may not be worth the cost.

There are different ways to clean solar panels, including using hand tools or special machines. Scientists are also working on new ways to keep solar panels clean, such as using special coatings or electric charges to move dust away without water.

Main article: soiling
Main articles: occupational hazards with solar panel installation

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nanowires
MIT
electrostatic repulsion

Waste and recycling

When solar panels are no longer used, they can create waste. In 2021, there were 30 thousand tonnes of solar panel waste, and this number is expected to grow a lot in the future. Many parts of solar panels can be reused or recycled. This includes glass, metals, and some special materials.

Different types of solar panels need different ways to be recycled. For example, silicon-based panels can often be processed by companies that recycle glass. Other types need special methods to safely separate their materials. Many places are working on better ways to recycle solar panels and reuse them.

Production

The making of solar power systems grows better and cheaper every year. In 2019, companies making solar parts grew very fast, turning into big players able to make billions of watts of solar power. Most solar panels use silicon cells to turn sunlight into electricity. These cells are usually about 10–20% good at this, but newer ones are even better, working over 22% of the time. In 2018, the top five companies making solar parts were Jinko Solar, JA Solar, Trina Solar, Longi solar, and Canadian Solar.

Making solar panels can use some chemicals that are not good for the environment, but scientists are working to make this process safer.

Top producers of PV systems, by shipped capacity in gigawatts
Module producer	Shipments in 2019 (GW)
Jinko Solar	14.2
JA Solar	10.3
Trina Solar	9.7
LONGi Solar	9.0
Canadian Solar	8.5
Hanwha Q Cells	7.3
Risen Energy	7.0
First Solar	5.5
GCL System	4.8
Shunfeng Photovoltaic	4.0

Price

Standards

Solar panels follow specific rules to make sure they work well and are safe. Some important rules come from groups like the International Electrotechnical Commission, which has standards such as IEC 61215 for crystalline silicon panels, and IEC 61646 for thin film panels. There are also safety rules like IEC 61730. Other groups, like Underwriters Laboratories, have their own standards, such as UL 1703, UL 1741, and UL 2703. Panels may also need a CE mark to show they meet European safety rules. There are also special testers to check electrical safety.

Applications

Main article: Applications of photovoltaics

Solar panels can be used in many useful ways. For example, they can help farms by powering water systems for crops. In hospitals, solar panels can keep medicines cool by running refrigerators. Solar panels are also used to power many different machines and tools we use every day, helping to make things work without needing electricity from the grid.

Limitations

As more homes install solar panels, the way electricity flows changes. Sometimes, a home makes more electricity than it uses and sends extra back to the power lines. But regular power systems weren’t built to handle electricity flowing both ways, which can cause problems like too much voltage on the lines. There are ways to fix these issues, but they can be tricky and sometimes cost money.

To keep the power on during an outage, a home with solar panels often needs a battery to store extra energy.

Quality assurance

Solar panels need to be tested to make sure they work well and last a long time—usually between 20 and 40 years. Tests can happen in labs, through physical checks, or with computer studies. Companies like TÜV Rheinland help make sure solar panels are good quality.

These panels are checked at different points during their life to ensure they can keep providing power as expected. There are special rules and standards they must follow to be considered safe and reliable.