Ever wonder what’s in a solar panel? Solar cells are made of the same material that forms the basis for another technological marvel: The computer chip. Like computer chips, solar panels are made of silicon, which is most commonly derived from sand.
So how do you get from a handful of sand to a solar panel capable of converting sunlight into electricity?
Solar Panels: From Sand to Silicon
In simple terms, here’s how solar, or photovoltaic, panels are made:
- The first step is to refine sand into pure silicon by removing the oxygen. This is done by heating it with carbon to over 3,600° F.
- The refined silicon is placed in a cylindrical furnace with a tiny amount of boron and heated again, this time to 2,500° F.
- Once melted, a seed crystal is introduced and drawn up through the top of the furnace. As the silicon cools, it forms a cylindrical crystal. The added boron ensures that the crystal has a positive potential electrical charge.
- The resulting crystal is cut into 2-foot ingots and squared. The ingots are then sliced into thin silicon crystal wafers. These will become the panel’s solar cells. The square shape with rounded corners ensures maximum surface coverage with minimum waste from the cylindrical crystals.
- Before the wafers can produce electricity, they must undergo several additional steps. These include:
- Texturing, to improve light absorption;
- Diffusing a thin layer of phosphorus onto the surface. This establishes a layer of negative potential electrical orientation. (Remember the addition of boron earlier to give the wafer a potential positive orientation? The opposing electrical potentials will enable formation of an electrical current in the finished cell.)
- Adding a silicon nitride coating to reduce reflection and further maximize light absorption;
- Printing of circuitry on both sides of the cell, to enable the collection and flow of electricity.
- Finally, the wafers are assembled into panels. They must be strung together to function as a unit, laminated onto a special type of solar glass, and set into lightweight aluminum framing to protect the assembly from weather and impacts.
Of course, the making of a solar panel is a highly technical and exacting process. Many of the steps require specialized equipment and robotics. Care must be taken at every step to ensure that the product is kept clean. Solar panel manufacturers must also continuously test the wafers and cells for quality assurance.
The Life Expectancy of Solar Panels
While it’s a long way from that handful of sand to the panels on your roof, there’s one thing solar panels do share with their precursor: longevity. Despite their intricate construction, you can expect your photovoltaic panels to last at least 25 years (although it’s not uncommon for solar panels to last much longer than that.) With the average payback for an investment in solar panels in Maryland now only 7 years, you don’t need to know exactly how they work to know that your solar panels will save you money for years to come!