Photovoltaics

Photovoltaics, often called PV, is a way to change light into electricity using special materials that show the photovoltaic effect. This effect is something scientists study in physics, photochemistry, and electrochemistry. We use this amazing trick to make power and even to make tools that can sense light.

A photovoltaic system uses solar modules made of many solar cells. These can be placed on the ground, on rooftops, on walls, or even floating on water. Some systems can move to follow the sun, which helps them catch even more light.

Photovoltaic technology is very important because it helps fight climate change. Unlike fossil fuels, using the sun to make electricity does not pollute the air or make harmful gases. Even though there are some challenges, like needing special systems to store the energy or share it over long distances, solar power keeps getting better and cheaper. Since the year 2000, the cost of solar panels has dropped a lot, making it an affordable way to get clean energy. Today, solar power is one of the biggest sources of renewable energy in the world and is becoming the cheapest way to make electricity in many sunny places.

Etymology

The word "photovoltaic" combines two parts: "photo," which comes from the Greek word φῶς (phōs) meaning "light," and "volt," named after the Italian scientist Alessandro Volta, who invented the battery. People have been using this term in English since 1849.

Greek volt Italian Alessandro Volta electrochemical cell

History

In 1989, Germany started the first program to help people put solar panels on their roofs. This program, led by Walter Sandtner in Bonn, helped install 2,200 roofs with solar power.

A few years later, in 1994, Japan began a similar program, installing solar systems in 539 homes. Since then, many countries have been working hard to grow the use of solar power quickly.

Solar cells

Main article: Solar cell

Solar cells are a way to make electricity from sunlight. They change the energy from the sun into a flow of tiny particles called electrons. This is called the photovoltaic effect.

These cells make a kind of electricity called direct current, which can power things or charge batteries. At first, they were mainly used in space for satellites and spacecraft. Today, most solar panels are used to help make electricity for homes and cities. To do this, a special device called an inverter changes the electricity so it can be used in most places. Solar cells can also be used in smaller ways, like for boats, cars, or places far from regular power lines.

Solar panels are made from many solar cells put together. They are connected with special wires and need to be protected from weather and other outside conditions. The amount of electricity they make can change depending on where they are, the time of day, and the weather.

Performance and degradation

Module performance is checked under special test conditions: a certain amount of sunlight, a specific type of light, and a set temperature. But in real life, the electricity a solar panel makes changes with where it is, the time of day, the weather, and the angle of the sun. To work best, solar panels should face the sun directly.

Solar panels can lose some of their ability to make electricity over time. This can happen because of things like temperature changes, rain, or snow. Different panels lose power at different rates, but most lose only a small amount each year. Some types of panels may lose more power in the first few years but then settle down.

Manufacturing of PV systems

See also: List of photovoltaics companies

Making solar panels is a straightforward process because it doesn’t need many moving parts. Solar panels last a long time, from 10 to 30 years. To get more power from a solar panel system, manufacturers can just add more solar parts. This makes it important to make lots of panels at once to save money.

Most solar panels around the world use a type called crystalline silicon. Making these panels has several steps. First, miners get quartz, which is turned into very pure silicon. This silicon is melted with a small amount of boron to create a special material. This material is then shaped into blocks and cut into thin pieces called wafers. These wafers are treated with phosphorus to change their properties. Finally, coatings and electrical parts are added to finish the solar cell. The cells are then connected together to make a solar panel ready for use.

Economics

See also: Photovoltaic system § Costs and economy

The cost of making solar power has changed a lot over the years. It has become cheaper because of better technology and more factories making solar parts. This makes solar power a good choice for many places, especially where electricity prices are high.

Renewable energy, like solar power, has become cheaper than fossil fuels in many parts of the world. This is because making solar panels and wind turbines has improved a lot.

In 1977, solar cells cost $76.67 for each watt of power. By 2024, the price dropped to as low as $0.11 for each watt, a big decrease. This happened because factories made more solar panels and found better ways to produce them.

The cost of solar power depends on where you are and how you calculate it. In some places, solar power can cost less than traditional power from coal or gas. However, solar power does not work at night and can be less reliable when the sun is not shining strongly.

Governments sometimes help solar power by giving money or special rules to make it more affordable. This was important in the early days of solar power. Countries like Germany and Spain helped a lot by giving money to people who used solar panels.

Some people think that more help from governments could make solar power even cheaper faster. This would let solar power compete better with fossil fuels.

Growth

Main article: Growth of photovoltaics

Solar power is growing quickly because it costs less and works well with batteries. Many countries are using solar power to help make clean energy.

Solar power is becoming very popular around the world. In April 2022, the world had enough solar power to make one terawatt of electricity. This makes more than 500 TWh of electricity each year, which is about 2% of all the electricity used worldwide. Big countries like China, the United States, and Japan are leading in using solar power. Some smaller countries, like Honduras, get a lot of their energy from solar too.

Applications

Main article: Applications of photovoltaics

Solar panels, also called photovoltaics, have many useful jobs. They can give power to farms for watering crops, help hospitals keep medicines cool, and make electricity for homes and big buildings. These panels work by turning sunlight into power that we can use.

Photovoltaic systems

Main article: Photovoltaic system

A photovoltaic system, or solar PV system, is a way to make electricity from sunlight. It uses solar panels to catch the sun’s energy and turn it into power. There are small systems for houses and big ones that make lots of electricity for whole towns. Most of these systems connect to power lines, but some can work all by themselves.

Photo sensors

Main article: Photodetectors

Photosensors are tools that can feel light or other kinds of energy from the sun. They change light into tiny bits of power. Solar cells are a special kind of photosensor that turns sunlight into electricity we can use.

Experimental technology

Crystalline silicon photovoltaics are one type of solar power technology, but there are many other exciting technologies being developed. These new technologies could help meet our future energy needs.

One newer technology is thin-film PV. It is made by putting special layers of materials, such as perovskite, onto a surface in a vacuum. These layers can be made from different materials and are then separated and connected to create electricity. Perovskite solar cells are very efficient but are still being researched to make them larger for everyday use. Thin-film solar cells might become popular in the future because they use fewer materials and cost less to make than traditional silicon solar cells.

Advantages

Solar power is clean and does not create pollution while it is being used. This helps reduce pollution compared to other types of energy. For example, using solar power instead of coal can help keep people healthier.

Solar panels usually last for about 25 years and need very little care after they are set up. This means that after the cost of building a solar power system, keeping it running costs very little. Solar panels can also be used right on rooftops, which helps save energy that would normally be lost when moving electricity over long distances.

There is still much to learn about making solar cells even better. Scientists and inventors are working to improve how well solar cells turn sunlight into electricity, and they are also finding ways to make them cheaper to produce.

In some places, special rules help people who want to put solar panels on their homes. For example, a program called PACE lets home owners pay for solar panels over time through small extra charges on their property taxes. This helps make sure that the value of the solar panels stays with the home even when the owner moves.

Disadvantages

When people use solar panels on their roofs to make electricity, sometimes there is more power than they need. This extra power goes back to the electricity grid. But the grid was not made to handle power going back to it, which can cause problems.

One problem is that too much power going back can make the voltage too high. There are ways to fix this, but they can cost money. Also, when the sun is shining brightly, people use less electricity from the grid, but when the sun goes down, they need more power quickly. This change can make it hard for power plants to keep the electricity supply steady.