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Capturing the Sun: The Science Behind Solar Panels

Author: Eric Lin

Editors: Ian Cho, Winnie Mok

Artist: Felicia Chen


Every day, the sun sends 14.9 Zettawatts of energy to Earth. To put that into perspective, the energy within sunlight that hits the Earth’s surface in one second is equal to the yearly energy usage of everyone on the globe. Currently, most residential solar panels can convert 15% to 20% of sunlight into electricity, which is around 350 to 450 watts of power. 

Compared to other sources of energy, solar has many perks, such as ease of maintenance, affordable initial cost, and renewable energy generation. Even against other sources of renewable energy, solar power has massive benefits. For example, hydroelectricity requires the construction of large dams, which not only have an enormous initial cost but also disrupt ecosystems by diverting rivers and lakes. On the other hand, solar panels can be installed on rooftops or open land with minimal environmental impact. 

This is not to say that solar panels don’t have their limitations. Panels perform poorly in areas with excessive heat and require regular cleaning of debris to continue at maximum efficiency. The most glaring limitation is the fact that energy cannot be produced at night. That said, modern grid connections and batteries can resolve the issue of storing power when energy is not being produced at night. Now that we know that solar energy has the perks of solar energy, what is the actual science behind it? 

At the core of solar panels are solar cells, which are semiconductors made from silicon. When sunlight hits these cells, photons from the sunlight transfer energy to electrons inside the silicon, exciting them and creating an electrical current. This process is known as the photovoltaic effect. Each cell consists of a p-n junction which is a combination of two semiconductor materials. The P-type silicon or positive side has freely moving electron holes while the N-type or negative side has free moving electrons. When sunlight hits the electrons on the negative side they move across the junction and towards the positive side, creating direct current (DC)—a steady flow of electricity in one direction. 

However, there lies a problem: most appliances and homes use alternating currents (AC), which is the opposite of direct current where electricity changes direction periodically as it moves through a system. As such, a device called a power inverter is used to change the DC and AC by rapidly switching the direction the DC flows creating AC waveforms that appliances and homes can use.  As of 2024, 4.2 million U.S. households have installed rooftop solar panels. Beyond just conversion, power inverters also optimize energy production, store excess electricity, and even allow surplus energy to be fed back into the grid. This makes solar energy more reliable and efficient as a primary power source. As research continues and innovations are made, solar efficiency will continue to rise as innovations in materials, storage, and grid integration will make solar energy an increasingly dominant force in global energy production. 

Currently, research is being done on tandem solar cells that stack perovskite—a special class of materials with a specific crystal structure that makes them highly efficient at absorbing sunlight and converting it into electricity layers— on top of silicon, achieving efficiencies over 40% in lab tests. This is a large improvement over traditional silicon solar cells which have a theoretical efficiency limit of about 29%.

 

Citations:

Aggarwal, V. (2024, July 19). How much energy does a solar panel produce? EnergySage.

CleanMax. (n.d.). Comparing solar energy to other renewable sources | CleanMax. CleanMax | #1

Rooftop Solar Developer. https://www.cleanmax.com/solar-update/how-solar-energy-

Roy, B. B. (2024, July 10). Amount of solar energy hitting Earth every second, day, week & year. Go

Solar Quotes. https://gosolarquotes.com.au/amount-of-solar-energy-hitting-earth/#:~:

Storr, W. (2022, August 6). PN Junction Theory for Semiconductor diodes. Basic Electronics

Sunrun. (2021, November 17). The best ways to maximize solar panel efficiency. Sunrun.

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