The hope for a “solar revolution” has been floating around for decades — the idea that one day we’ll all use free electricity from the sun. This is a seductive promise, because on a bright, sunny day, the sun’s rays give off approximately 1,000 watts of energy per square meter of the planet’s surface. If we could collect even a small fraction of that energy, we could easily power our homes and offices for free.
This future is happening, rapidly.
For most of us though, how solar actually produces electricity is a mystery. I hope to unravel at least of part of that mystery with you today.
Energy from the sun, in the form of discrete particles called photons, shine on the photoelectric panel. Photovoltaic, or PV for short, are cells that convert sunlight into electricity.
They are important because they make up the solar panel and are the key module in the system responsible for the electricity generation.
They are essentially made of a semiconductor like silicon and a few other materials. When sunlight hits the cell, a portion of the energy is absorbed into the semiconductor material.
When looking at the element silicon at an atomic level, one will see that each atom of silicon has 14 electrons. A silicon atom will bond with other atoms to form a crystalline structure.
However, just silicon in a solar cell is not sufficient to conduct electricity because none of its electrons are free to flow resulting in no electricity.
To solve this, engineers add a Phosphorus doped layer (called the n-type semiconductor) and a Boron doped layer (called the p-type semiconductor). This is important because it changes the top layer to a negative charge and the bottom layer to a positive charge.
The imbalance between layers is crucial for the generation of electrical currents. When photons (discrete particles of sunlight) are introduced from the sun to the panel they knock electrons loose to move throughout the silicon’s crystallized structure.
The middle layer is all silicon with a neutral charge. This allows electrons to move from the positive layer to the negative layer but not back. Situating a circuit from the negative layer to the positive layer creates a flow of electricity and with it, the ability for electrons to do work and power a house.
Not only can the sun power a house, but with this electricity and storage, we could power our entire civilization (at least a good portion of it). We can become free from the polluting emissions that are threatening to change our climate and the future generations of humans to come.
Bill Womeldorf is a building efficiency designer in Boston, MA. He’s typically the one with the reusable water bottle in business meetings. When we all work together, he believes, it’s possible to solve the climate crisis. You can follow Bill on twitter @BillWomeldorf