How Solar Panels Generate Electricity: In-Depth Explanation

The basics of solar energy

Most people are already familiar with the basic principles of how solar energy is harnessed: it is captured from the sun’s rays. Along with other clean energy sources like wind power and hydropower, solar is a vital component of a growing base of renewable energy sources. These sources have the potential to significantly reduce our reliance on fossil fuels and decrease greenhouse gas emissions.

As with any other energy source, there are some pros and cons of solar energy to consider. However, its potential is undeniable. In just one hour, the Earth receives enough sunlight to power the entire planet – encompassing everything from residential properties and individual electronic devices to large-scale industrial and commercial operations.

Ready to get more technical about how solar energy is converted into electricity? Then read on! Alternatively, if you want to develop a solid baseline understanding before moving on to the nitty gritty of how solar works, you can read more in our intro to solar energy blog.

How solar panels generate power

To fully understand how solar works, you’ll need to learn more about how energy from the sun can be converted into usable electricity. Let’s begin with an overview of the sun as a power source before examining the two main mechanisms used to convert sunlight into electrical current.

How the Sun creates light

Solar power on Earth begins about 93 million miles away. Way out in space there’s a gargantuan ball made up of gas, mostly helium and hydrogen. We all call it “the Sun.”

Inside the core of the Sun, there’s a process constantly occurring called nuclear fusion. This means that atoms are slamming into each other so hard that they fuse together. In the Sun’s core, hydrogen atoms are fusing together to form helium atoms. Now imagine this process occurring hundreds of millions of times per second. Humans can’t technically visualize anything at this scale, but you just need to know that it’s an incredible amount of energy being produced at all times.

After nuclear fusion happens in the core of the Sun, the energy produced (heat, light, and radiation) travels outwards towards the surface. When the energy finally reaches the surface, or the photosphere, it’s released into space as sunlight. Sunlight is manifested in several ways including visible light, infrared radiation, and ultraviolet light.

Visible light – This is the portion of the solar spectrum that we can see. It is an essential component in photovoltaic systems, which convert solar energy to electrical energy.
Ultraviolet (UV) radiation – UV has higher energy than visible light. While it contributes to the total amount of energy that can be harnessed, it is less efficient in generating electricity.
Infrared radiation – While not visible to the human eye, infrared radiation plays a significant role in thermal solar energy production, such as heating water or air.

Sunlight races away from the Sun in all directions at over 186,000 miles per second. The sunlight headed in the direction of Earth reaches us in about 8 minutes and 20 seconds.

The architecture of a solar panel

Solar panels are made up of rows of solar cells or photovoltaic cells. The cells are flat, square structures constructed of glass and silicon layers with dimensions of between 0.5 and 6 square inches.

There are other types of solar cells that have different architectures, but for the sake of this article we will focus on PV cells as they are the most common.

The surface of a solar cell

On the surface of the cell there is a grid pattern of thin metal lines called the front contact. These lines are there to capture and collect electrons that are freed when sunlight hits the cell.
Solar panels are mostly black because of the solar cell’s anti-reflective coating designed to absorb as much light as possible. This increases the efficiency of the solar panel and it’s cells.
Just above the anti-reflective coating are layers of a transparent, protective material that protects the cells from environmental damage like moisture and dirt.
Above this protective layer is highly-tempered glass which is impact resistant. This protects the solar panel from harsh weather conditions such as hail or falling objects like tree branches.

Inside the solar cell

Underneath the upper layers lies the silicon core of the cell. Silicon is a semiconductor material that is essential for what’s called the “photovoltaic effect” — we’ll get into that a bit further into the article.
The top layer of the core of the cell is called the N-type layer. It also contains the element phosphorus and has an excess of electrons, which gives this layer a negative charge.
The bottom layer of the cell is called the P-type layer. This layer contains the element boron and has fewer electrons, which gives this layer a positive charge.
In between the layers is the PN Junction, an interface which allows for the creation of an electric field between the N-type and P-type layers.

The bottom of the solar cell and solar panel

Underneath these silicon core sits a solid metal layer called the back contact, which allows electrons to flow out of the cell and into the electrical circuit which feeds into the grid.
The underside of the solar panel is lined and closed with a metal frame to provide structural support, protect the glass edges of the panel, and facilitate the mounting and installation of the panel.
Outside the metal frame you can find the junction box and wiring which allow you to connect the panel to external wiring. This is where electricity generated by the panel flows into an electrical system of a home or a power grid.

How solar panels convert sunlight into electricity

Now that you understand how solar panels are constructed, let’s dive into how they generate electricity.

There are two primary ways in which solar panels generate electricity: thermal conversion and photovoltaic effect. Photovoltaic solar panels are much more common than those that utilize thermal conversion, so we’ll be focusing on PV solar panels.

Understanding the photovoltaic effect

Sunlight strikes the solar cells of the solar panel. Some of the rays of light or photons pass through the outer layers of the cell and into the silicon core.
When the photons enter the core, they excite and free the electrons. Thanks to the imbalance or electric field generated by the PN Junction, electrons freed in the top N-layer are caught by the front contact.
At the same time, the freed electrons are leaving behind “holes” where they used to reside within the atoms. These “holes” are driven by PN junction field towards the P-layer.
As the free electrons are caught by the front contact and the holes are caught by the back contact, this completes the circuit and generates an electric current.
The current flows out of the cell as electrical energy (electricity!) and through the junction box and wiring on the back of the panel.

Thermal conversion

Thermal conversion utilizes solar energy for heating. Thermal systems concentrate solar radiation using mirrors or glass casing and lenses to absorb sunlight and heat water or glycol (an organic compound belonging to the same family as alcohol). The liquid, now heated to high temperatures, produces steam to drive a turbine and generate electricity.

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If you’ve found this explanation of solar energy and how it works helpful, then you’re probably already interested in exploring renewable electricity plans.

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Written by Graham Lumley

Graham Lumley, Growth Product Manager at BKV Energy, leads digital and traditional marketing strategies, focusing on educating Texans about the state's deregulated energy market. With over 10 years of marketing experience, he creates content to help consumers understand and save on their energy bills, bringing a fresh and dynamic approach to the industry.