SolarPowerNerd
The basic process behind solar power is straightforward, even though the technology has gotten more advanced over the years. Every step builds on simple physics.
This guide traces a photon’s journey from the center of the sun all the way to your wall outlet, covering the science and hardware at each stage.
Chapter One: Journey from the Sun
Believe it or not, it takes tens of thousands of years for one small particle of light from the sun to hit your solar panel. And it takes far more than one particle to produce enough energy to create an electrical current.
The epic story of the photon (from Greek phos, phot, meaning light) begins at the very center of our sun. The process of nuclear fusion, caused by intense pressure, releases staggering amounts of energy as two atoms merge.
Our little photon pings its way from atom to atom, being absorbed and emitted time and again over an estimated forty thousand years to finally reach the sun’s surface.
After such a long journey, the photon is flung into space at such speed it only takes 500 seconds (8 minutes and 20 seconds) to travel 1 AU (Astronomical Unit) from the sun to Earth, an impressive 92,955,807.3 miles.
When the photon has traveled all that way, it’s absorbed by an atom or molecule and passes its energy to an electron, which becomes very excited. Enough excitement can cause the electron to escape its atomic bonds, but this depends on the frequency of the light.
For the most part, it’s a one-for-one exchange: one high-frequency photon for one electron. This is one of the problems physicists and chemists are working to overcome by experimenting with different materials such as Perovskite and light-absorbing dyes.
A photon with low energy frequency is less able to excite an electron enough to dislodge it. Multiple low-frequency photons with a combined sum of energy still can’t perform the task of a single high-frequency photon.
That said, innumerable photons are being cast in Earth’s direction. Similarly unfathomable numbers of electrons are being stimulated in conductive material, and we get the movement of energized negative particles we know as electricity.
It was French physicist Alexandre Edmond Becquerel who at age 19 (in 1839) discovered that shining light on an electrode submerged in a conductive solution would create an electrical current.
This effect was initially called the Becquerel Effect. It’s what we now know as the Photoelectric or Photovoltaic Effect.
This field was further advanced in a 1905 paper by Albert Einstein (“On a Heuristic Viewpoint Concerning the Production and Transformation of Light”), describing the linear relationship between light frequency and the energy of dislodged electrons.
Einstein’s paper was first received with skepticism because it undermined established understandings of light. He introduced the concept of a particle of light called a “Quanta,” defying the widely accepted theory that light was only a wave.
Light is made of these particles, the quantum (today’s photons), and it moves in an oscillating wave formation.
In 1914, Robert Andrews Millikan proved Einstein’s theory correct, paving the way for quantum physics. Einstein received the Nobel Prize for Physics in 1921.
His fresh look at light’s behavior advanced the concept of the photoelectric effect, showing how photons transfer energy to electrons and explaining how light creates and sustains electrical current.
The first solar cell was created by Russian physicist Aleksandr Stoletov in 1888. American Russel Ohl later patented the true forebear of today’s solar cell.
At Bell Laboratories, inventors Fuller, Chapin, and Pearson demonstrated the first practical Photovoltaic (PV) Cell, which is still largely used today.
Chapter Two: Inside the Panel
The Photovoltaic cell has been developed and improved a lot since Stoletov’s time, but the core technology hasn’t changed much in about 130 years.
The same principles power everything from Arnold Schwarzenegger’s million solar roofs pledge to the White House solar panel installations to millions of home and business owners across the globe. Understanding how solar panels are made helps explain why these principles still work so well.
Using the knowledge that an energized electron can create a current isn’t enough on its own. We need an impetus, something to create voltage (described as electric potential difference), which is like hydraulic pressure but with subatomic particles.
This drives the electric current from point A to point B.
Enter the extrinsic semiconductor.
The solar panel consists of cells covered in a layer of glass or other translucent material. This acts both as a window for light to pass through and as protection for the semiconductor wafers beneath.
Over 90% of solar cells contain layers of crystalline silicon as the semiconductor. There are two opposing layers of silicon that have been “doped” (the doping process changes an intrinsic semiconductor to extrinsic) with different chemical elements.
The n-type layer (donor, repelling) is usually made with phosphorus. The p-type layer (acceptor, attracting) is made with boron.
This is called the P-N junction: P-type positive and N-type negative.
Several different materials are used in solar cell production. Silicon remains popular due to its durability and efficiency, but research has delivered interesting products for unique applications.
One that has excited many eco-nerds is the evolution of Organic Photovoltaics (OPV). Organic PV cells have huge potential because they could provide electricity at a much cheaper rate than silicon. They’re less expensive to manufacture on a large scale.
The cells are made from carbon-rich polymers and can be modified to amplify specific attributes, such as sensitivity to different frequency bands in the spectrum of light.
There are several drawbacks to OPV technology. Cell lifetime is generally shorter than silicon, and efficiency is less than half.
OPV cells can be applied to a much larger range of structures though, making them viable for creative architectural designs.
Other semiconductor materials include Cadmium Telluride (CdTe), Copper Indium Gallium Selenide, Gallium Arsenide, and Perovskite. Each has pros and cons, and each is still in development.
Back to what happens inside the panel. When the photon agitates an electron and the electron disentangles from its atomic orbital, the relationship between n-type and p-type squeezes the electrons along to create the electric current.
This continues until the current reaches an electrode.
Chapter Three: From Panel to Plugging In
The circuit isn’t complete yet. Many cells are needed to make a panel, and many panels are needed to make an array that can run a home, heat a pool, or power a satellite.
Cells are linked in parallel and/or series circuits to combine DC (direct current) energy toward a junction box. This small but vital piece attaches to the panel and handles heat regulation and protection from water, dirt, and insects.
The junction box’s main job is to pull all that electron juice into one cable and direct it toward your home. It typically contains four diodes, which are terminal electrical components with a dual purpose.
The diodes should have as high as possible resistance in one direction and as low as possible resistance in the other. Here again we see the silicon semiconductor with a p-n junction that maintains the flow of electricity in the desired direction and protects the panels from energy feedback.
The DC energy then flows to a solar inverter or power box where it’s converted into safe AC (alternating current) to run domestic appliances, warm water, and heat homes.
There are three types of inverters. First, off-grid or stand-alone inverters are disconnected from the utility grid but connected to batteries storing surplus energy for later use.
The batteries have special backup inverters that manage power flow.
The second type is grid-tie inverters. These work with the grid and usually aren’t available during power outages due to anti-islanding protection, a failsafe that halts energy flow during electrical maintenance.
The third type is a hybrid, combining the best attributes of both stand-alone and grid-tie inverters. It manages backup storage, PV panels, and the grid.
It’s more intelligent and versatile, but not cheap.
The alternating current from your inverter travels through copper wires to your distribution board. There it’s divided into separate circuits for distinct areas of your home: lighting, heating, air conditioning, power outlets, upstairs and downstairs.
Circuit breakers or fuses in your distribution board protect your home from energy overload. Energy from the distribution board carries on through more copper wiring to your socket, to your plug, to your computer.
You’ve just spent the last few minutes reading an article powered by particles of light older than civilization.
Frequently Asked Questions
How long does it take sunlight to reach a solar panel?
Photons begin their journey at the sun’s core, where nuclear fusion releases enormous energy. They bounce between atoms for roughly 40,000 years before reaching the sun’s surface.
After that, they travel 93 million miles to Earth in just 8 minutes and 20 seconds, arriving ready to generate electricity.
What’s the difference between DC and AC electricity in solar systems?
Solar panels produce direct current (DC), where electrons flow in one direction. Your home appliances need alternating current (AC), where electrons switch direction rapidly.
A solar inverter handles the conversion from DC to AC, making the panel’s electricity compatible with your outlets and everything plugged into them.
Can solar panels work on cloudy days?
Yes, solar panels still produce electricity on cloudy days, though at reduced output. Panels rely on photons, not direct heat, and photons still reach the surface through cloud cover.
Expect about 10 to 25 percent of normal output on overcast days. Battery storage systems help cover gaps during low-production periods.
What is the photovoltaic effect?
The photovoltaic effect occurs when photons strike a semiconductor material and knock electrons loose from their atoms. The freed electrons flow through an external circuit, creating an electrical current.
This phenomenon was discovered in 1839 and remains the foundation of all modern solar panel technology used in residential and commercial systems.
Final Thoughts
Solar power follows a remarkable path from nuclear fusion in the sun’s core to the outlet on your wall. Every stage builds on straightforward physics that scientists have understood for over a century.
The technology keeps improving, but the fundamentals haven’t changed. Photons dislodge electrons, semiconductors direct the flow, inverters convert it to usable power, and your home runs on sunlight.
