Solar panel

A solar panel is a device that changes sunlight into electricity. It uses many small parts called solar modules. These modules have special cells that make excited electrons when light shines on them. The electrons move and make direct current electricity. This electricity can power devices or be stored in batteries.

Solar panels are often put together in groups called arrays or systems. A full photovoltaic system has one or more solar panels. It also has an inverter that changes the electricity from direct current to alternating current. Sometimes it has other parts like charge controllers or solar trackers to catch the most sunlight. Many panels are placed in big areas called solar farms. They can also be placed on house roofs as rooftop solar panels. This helps give power to the electricity grid.

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

History

See also: Solar cell § History, Timeline of solar cells, and Growth of photovoltaics

In 1839, a scientist named Edmond Becquerel found that some materials could make electricity when light hit them. This was the first step to making solar panels. Later, in 1881, an inventor named Charles Fritts built the first solar cell, but it did not work very well.

In 1954, scientists at Bell Labs made the first useful solar cell using silicon. After that, solar energy grew fast. Solar panels became cheaper, so more people could use them. Today, solar energy helps power homes and businesses without burning fossil fuels.

Theory and construction

See also: Solar cell

Photovoltaic modules are made from many solar cells that change sunlight into electricity using the photovoltaic effect. Most modules use either wafer-based crystalline silicon cells or thin-film cells. The cells need protection from damage and moisture. The cells and modules are connected to raise the voltage and current they make. Most panels are stiff, but flexible ones from thin-film cells are also sold. The power of a solar panel, in watts, depends on sunlight and the electrical load linked to it.

Solar panels often have metal frames to hold their shape. Smart solar panels have built-in electronics to help them work well, like finding the best sunlight or checking how they are doing. Most solar panels today use crystalline silicon, with a few using thin-film technology. Some special panels can catch sunlight on both sides to make more energy.

Efficiency

See also: Solar-cell efficiency

Solar panels change sunlight into electricity. Their efficiency shows how well they do this. A panel’s power output can change depending on where and when it is used, usually between 100 to 365 Watts. Higher efficiency means a smaller panel can produce the same amount of power. As of 2025, the best solar panels can turn about 24.5% of sunlight into electricity.

The electricity a solar panel makes also depends on its location and weather. Places closer to the equator or with clearer skies get more sunlight, so their panels work better. For example, panels in the United Kingdom might only work well about 10% of the time on average, while in Spain they can work up to 18% of the time. Heat can also make solar panels less efficient.

Performance and degradation

Solar panels are tested to see how well they work under different conditions like sunlight, temperature, and angle. Their output changes during the day and year based 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 with similar electrical qualities.

Temperature affects how well solar panels work. Cooler temperatures can sometimes help them produce more power, but cold weather can bring 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 place solar panels on the ground, held up by special supports. These supports can be poles driven into the earth, concrete foundations, or weighted bases. This works well where digging isn’t possible.

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

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

Maintenance

Solar panels can work less well when dust, dirt, or pollen gets on them. This is called soiling. In very dusty places, a dirty solar panel might work up to 30% less well. Cleaning solar panels can be a good idea in many areas.

There are different ways to clean solar panels, like using hand tools or special machines. Scientists are also finding 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
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Waste and recycling

When solar panels are no longer used, they can create waste. 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. Many places are working on better ways to recycle solar panels and reuse them.

Production

See also: List of photovoltaics companies

Making solar power systems is getting better and cheaper every year. Companies that make solar parts are growing fast and can now make lots of solar power. Most solar panels use silicon cells to change sunlight into electricity. These cells are usually about 10–20% good at this, but newer ones work even better.

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 sometimes use chemicals that are not good for the environment, but scientists are finding ways to make this process safer.

Price

See also: Grid parity

The cost of solar power keeps getting lower. In many places, it is now cheaper than electricity from fossil fuel sources. This is called grid parity. Governments, like the IRS, help by giving money back to people who install solar panels.

Prices change depending on how much you buy. Small, medium, and large buyers all pay different amounts. Over many years, solar panels have become much cheaper. In 2012, they cost about US$0.60 per watt, which is less than the US$150 in 1970. Sunny places can make solar power more cheaply than cloudy places.

Standards

Solar panels follow special rules to make sure they work well and are safe. Groups like the International Electrotechnical Commission make rules 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 rules, such as UL 1703, UL 1741, and UL 2703. Panels may 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

See also: List of solar-powered products

Solar panels have many useful jobs. They can help farms by powering water for crops. In hospitals, solar panels can keep medicines cool by running refrigerators. Solar panels also power many machines and tools we use every day, helping them work without needing electricity from power lines.

Limitations

When more homes use solar panels, the way electricity works can change. Sometimes a home makes more electricity than it needs and sends the extra back to the power lines. But regular power systems were not made to handle electricity moving both ways. This can cause problems, like too much power on the lines. There are ways to fix these problems, but they can be difficult and sometimes cost money.

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

Quality assurance

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

These panels are checked at different times during their life to make sure they keep providing power as expected. They must follow special rules and standards to be safe and reliable.