If you’re reading this, then you’re probably someone who supports solar power. That’s great! Maybe you’ve already taken the plunge and gone solar at home. Or maybe you’re still thinking about it.
Either way, if you’re like our solar customers around central and southwestern Virginia, you’re probably also the kind of person who likes to know how things work.
If that’s true, then you’re in the right place. Here, I’m going to give you a quick and dirty introduction to the most important part of any solar energy system: the solar panels.
The Star of the Solar Show
It takes different kinds of equipment to make up a solar power system, including inverters, racking and wires. But when most people think of solar, they usually think first of shiny blue or black solar panels.
And the biggest news in the solar industry over the last few years has been falling prices. On average, in Virginia alone home solar is half the price it was ten years ago. That explains why so many families in the Old Dominion have started going solar recently.
For years, the cost of solar panels came down so much in the last decade that it made the cost of a whole solar system cheaper. The price for solar panels actually stabilized in 2012. Yet, since then, the installed cost for an average home solar system has continued to decline each year. That’s mostly because of lower costs for the other parts of a solar system besides solar panels, such as inverters.
While advances in manufacturing were behind most of the cost reductions for all the components of a solar power system, the basic technology of solar panels has changed surprisingly little in the six decades since the first modern solar panel came out in 1954. Check out this video from the Department of Energy for a quick take on solar’s technology.
[Learn more about PV & solar technology: download our free ebook answering the “Top 10 Questions on Solar”]
Solar Technology is Older than Cars and Telephones
The solar technology used today to convert the sun’s rays into electricity, known as photovoltaics or PV, actually goes back nearly 200 years.
“In 1839, French scientist Edmond Becquerel discovered that certain materials would give off sparks of electricity when struck with sunlight,” explains the Union of Concerned Scientists. “Researchers soon discovered that this property, called the photoelectric effect, could be harnessed; the first photovoltaic (PV) cells, made of selenium, were created in the late 1800s. In the 1950s, scientists at Bell Labs revisited the technology and, using silicon, produced PV cells that could convert four percent of the energy in sunlight directly to electricity.”
In the 1960s, the aerospace industry used solar PV to power NASA spacecraft. When the energy crisis of the 1970s hit consumers with high electricity bills, homes and businesses began to install solar PV as well.
While the basic technology of PV is tried and true, solar panels have gotten much more efficient over the years. Just 15 years ago, the average solar cell converted about 10% of the light that hit its face into energy. Today, most solar panels convert between 15% and 20% of light into power. And according to researchers, that’s about ten times more efficient than plants are at converting sunlight into power through photosynthesis!
A solar panel, or photovoltaic module, consists of a number of solar cells electrically connected to each other.
The diagram above shows how a basic photovoltaic cell works. As the NASA website explains,
Solar cells are made of the same kinds of semiconductor materials, such as silicon, used in the microelectronics industry. For solar cells, a thin semiconductor wafer is specially treated to form an electric field, positive on one side and negative on the other. When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material. If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current — that is, electricity. This electricity can then be used to power a load, such as a light or a tool.
Most PV cells are squares just a few inches wide. By itself, a single solar cell generates very little power, so solar cells are connected together as PV modules or PV panels. The panels can be used by themselves or put together to form a larger solar array.
[Learn more about PV & solar technology: download our free ebook answering the “Top 10 Questions on Solar”]
Three Types of Solar Cells
There are three basic types of solar cells:
- Single-crystal PV Cells. Also known as monocrystalline PV, these cells are made in long cylinders and sliced into thin wafers. Since this process is energy-intensive and uses more materials, it’s more expensive. But it produces the highest-efficiency PV cells, which can convert about 23% of light into power. About a third of all solar panels currently installed around the world use monocrystalline cells.
- Polycrystalline PV Cells. These less expensive solar cells are made of molten silicon cast into ingots then sliced into squares. While production costs are lower, the efficiency of the cells is lower too – converting 20% of light or less to electricity. About half of all solar panels installed worldwide use polycrystalline PV cells.
- Thin Film PV Cells. These more specialized cells only supply about 10% of the global market for solar cells today. To make them, factories have to spray or deposit amorphous silicon, cadmium-telluride, or other materials onto glass or metal surfaces in thin films, making the whole module at one time instead of assembling individual cells. Traditionally, thin film cells have less been efficient at converting light into power, but they’ve improved recently and may now be about as efficient as polycrystalline PV cells. Because they use fewer materials, thin film PV cells can also be cheaper to make. And people are excited about the new applications for solar PV that thin film technology can open up, like Tesla’s new solar roof tiles.
In past decades, most PV panels were used to provide power for remote locations not served by the electrical grid such as a vacation home located in a wilderness area. However, today more than 99% of solar panels power buildings that are already connected to the electricity grid.
This means that, in Virginia as in most parts of the U.S., owners of solar power systems can sell the extra power they produce but don’t use themselves to their local utility company through a process called net energy metering. Likewise, at night, when PV panels are not producing electricity, solar homeowners can draw on the grid for their electricity needs. In this way, the grid serves as a gigantic battery to back up solar PV arrays without the extra expense of having to install batteries on site.
Finally, like the rest of the average home solar system, PV panels have no moving parts, which means there’s little chance of anything breaking. Also, in Virginia, where regular heavy rains remove most dust or bird droppings that accumulate over time, solar panels don’t require cleaning. Every five years you might have your system inspected — and cleaned if necessary. Otherwise, solar panels generally require little or no maintenance.
Learn more about PV and other solar technology: download our free ebook on the “Top 10 Questions & Answers on Home Solar in Virginia.”
— Andrew Brenner, Main Street Solar
