Physics Extra Credit

Anonymous High School Student

April/May 2025

Solar energy is one of the best types of renewable energy we have. It comes from the sun and can be turned into electricity or heat. The most common way to get energy from the sun is with solar panels, which use something called photovoltaic (PV) cells. These cells take sunlight and change it into electricity we can use. Solar energy is clean because it doesn’t make pollution while creating power. This makes it a great way to fight climate change and replace fossil fuels like coal and gas. Science, especially physics, helps us understand how solar panels work. Some important parts of physics involved are light, electricity, and heat. Solar energy can be used in small homes or giant solar farms. But even though it’s useful, it has problems like low efficiency and how to store energy for nighttime or cloudy days.

The main way solar panels work is because of something called the photoelectric effect. This is when light hits a material and knocks out electrons, which are tiny particles that carry electricity. When the sun’s light hits the solar panel, it gives energy to these electrons, which then start to move and make electricity. Solar panels are usually made of silicon, a material that works really well for this. The energy in sunlight depends on its color or frequency, higher frequency light has more energy. If the light doesn’t have enough energy, it won’t knock the electrons loose. That’s why some colors of sunlight work better than others. Scientists use a special equation (E = hf) to measure this. The goal is to use materials that let as many electrons as possible move. That’s how we get more energy from sunlight.

Solar panels are made from special materials called semiconductors, and silicon is the most common one. Scientists add tiny amounts of other elements to the silicon to help it work better, this is called doping. This creates something known as a p-n junction, where two sides of the material act differently. When sunlight hits this area, it causes electrons to move and create an electric current. This is what gives us power. But sometimes, the electrons fall back into place before they can do their job, which wastes energy. That’s called recombination. Also, some energy is lost through the wires or gets turned into heat instead of electricity. Another important part is the band gap, which means how much energy a material needs to start making electricity. Scientists pick materials with the best band gap to get more power from the sun.

Efficiency means how much of the sun’s energy a solar panel can turn into electricity. Most solar panels today can turn about 15% to 22% of sunlight into power. That may not sound like a lot, but it's still helpful. Scientists say there’s a limit to how efficient a single-layer solar panel can be—about 33%. That’s because some sunlight has too much or too little energy to work well. Some of it turns into heat instead. To improve this, engineers are building panels with more than one layer to catch different parts of sunlight. They also try to reduce energy loss from things like resistance or bad angles. All of this is based on physics and how light and electricity work. The more we learn, the better we can make solar panels.

Thermodynamics is the study of heat and energy, and it matters a lot in solar power. Some solar systems don’t make electricity directly, they heat up water or air instead, which can power machines. The first law of thermodynamics says energy cannot be created or destroyed, only changed. So sunlight becomes heat, and heat can be used to do work. But the second law says you can’t turn all heat into useful energy because some of it is always lost. In regular solar panels, heat is actually a bad thing. When panels get too hot, they don’t work as well. Hot temperatures make it harder for electricity to move the right way. That’s why some panels have cooling systems or special coatings to stay cooler. Physics helps us figure out how to deal with this problem.

The amount of electricity a solar panel makes depends on how strong the sunlight is. This is called solar intensity and is measured in watts per square meter. A simple equation, P = IV (power equals current times voltage), helps figure out the power a panel produces. The angle of the sunlight also matters, a panel gets more light if it faces the sun directly. That’s why solar panels work best when they are tilted toward the sun and sometimes move during the day. Weather, seasons, and location on Earth all affect how much sunlight a panel gets. Dust or pollution in the air can block sunlight too. Engineers use math and physics to find the best angle and place to put solar panels. They even use tracking systems that follow the sun’s path for more energy.

The environment has a big impact on how well solar panels work. Clouds, fog, and air pollution can block or scatter sunlight. Snow or dirt can cover the panels and stop light from getting in. The Beer-Lambert law helps explain how light fades as it travels through things like clouds. Heat is also a big factor, hot days can make solar panels less efficient, as mentioned earlier. On the other hand, wind can help cool the panels down a little. Moisture from rain or humidity can damage some parts of the panel if they’re not protected. Also, the sunlight angle changes during different times of the year because of the Earth’s tilt. Some places only get good solar energy during certain seasons. That’s why scientists and engineers need to study the local environment before setting up solar power systems.

The type of material used in a solar panel can change how well it works. Most panels use silicon, but new materials like perovskites are being tested because they might work even better. Some materials can absorb more sunlight even if they are very thin. This makes panels lighter and cheaper to make. Scientists use anti-reflective coatings so that light doesn’t bounce off the panel and go to waste. These coatings use wave interference, which is a physics idea about how waves can add or cancel each other out. Some panels even use tiny patterns or nanomaterials to trap more light. This means more energy gets absorbed and turned into electricity. All of this is based on our understanding of how light and materials interact. Better materials mean better solar panels.

One big problem with solar energy is that it doesn’t work at night or when it’s cloudy. So we need ways to store the energy for later. One option is batteries, which store energy chemically and release it when needed. Lithium-ion batteries are common and use physics and chemistry to move electrons around. Another option is using heat storage, where hot materials keep the energy until it’s needed. Some places even pump water uphill and let it flow back down to make electricity later. All of these systems lose a little energy, so scientists try to make them better. Storage is important because it helps people use solar power all the time. Without storage, solar energy isn’t very reliable. Physics helps us find the best ways to store energy without wasting it.

A big challenge for solar panels is that they get too hot, especially in places like deserts. When this happens, their efficiency drops. This is because the heat messes with how electrons move through the material. The band gap, which is how much energy the material needs to work, changes a little when it’s hot. Also, high temperatures create more vibrations in the material, called phonons, which slow down the electrons. This makes the panel produce less electricity. Fans and water coolers can help, but they take energy and cost money. In hot areas, this problem is hard to fix. That’s why scientists are looking for new ways to cool solar panels using physics. One idea is radiative cooling.

Radiative cooling is a special way to cool down objects without using power. It works by letting heat escape as invisible infrared light into space. Special materials can reflect sunlight while still sending out heat. These materials don’t need fans or electricity, they work on their own. Scientists design them to give off radiation at wavelengths that go straight through Earth’s atmosphere. This is based on physics ideas like blackbody radiation and Planck’s law. By adding these coatings to solar panels, they can stay cooler and work better. Some tests show this can improve efficiency by 2% to 5%, which is a big deal in solar energy. Radiative cooling is a great example of using physics to solve a real-world problem. It could be used more in the future.

Solar energy is a powerful and clean way to make electricity, and physics helps us understand how it works. From the photoelectric effect to thermodynamics, physics explains how light turns into power and what gets in the way. Things like temperature, sunlight angle, and materials all affect how much energy we get. Even though solar panels are getting better, we still face problems like energy storage and overheating. But using science, we can find smart ways to fix them. Radiative cooling and better materials are just a few ideas that show what’s possible. Solar energy has a bright future because we keep learning how to improve it. As technology grows, physics will keep guiding us. The sun gives us free energy every day, we just need to know how to catch it. And with science on our side, we’re getting closer.