As the popularity of solar continues to rise, the sight of solar panels topping a home or business is becoming commonplace. You may even have some on your own home, helping provide the power enabling you to read this article online. But did you ever stop to think how they got there?
The creation of a solar panel from raw materials to installation on your roof is a complex process. For most people, it’s a process that is shrouded in mystery. It needn’t be, though. In fact, if you have solar panels or are considering getting them, you should know how they are made. Let’s take a look!
Types of solar panels
First, we should clarify that there are several different types of solar panels. In this article, we’ll be discussing the most common type of solar panel in the U.S.—photovoltaic (electricity-producing) panels made with crystalline silicon.
There are two types of crystalline silicon PV panel. The difference has to do with the type of solar cells—the flat, square(ish)-shaped parts of the panel that actually generate electricity—used to create them. Monocrystalline, or single-crystal, cells are made from silicon ingots. These tend to be slightly more efficient and perform better in high temperatures. We will take a closer look at the manufacture of monocrystalline solar cells below. Polycrystalline, or multi-crystalline, cells are made by melting raw silicon and pouring it into a mold. They are cheaper to produce, but not as pure as monocrystalline cells and typically not quite as efficient.
The raw materials for solar
The process of making solar panels begins with raw materials. These include silicon; aluminum for the frame; copper, silver, aluminum and lead for the electronic components; and a host of abrasives, cleaners, catalysts and other chemicals.
It’s important to note that like all manufacturing, the production of solar panels is not without environmental impact. Some of the chemicals used in mining and manufacturing silicon and silicon products must be handled carefully to prevent or minimize harm to the environment and workers’ health, which is why it’s very important to select panels made by responsible manufacturers. A number of solar panel manufacturers, especially those based in China, operate under lax standards and have even been observed dumping toxic material onto farm fields. When selecting panels, look for those made by manufacturers who can document their environmental standards and those of their supply chain.
The making of a solar cell
To make a monocrystalline cell, silicon rock is first heated to red-hot in a crucible, along with a tiny amount of boron. Once conditions in the crucible are right, a silicon seed crystal is lowered into the molten silicon, which begins to freeze around it, matching the crystal pattern. The result is a long, cylindrical silicon crystal, or ingot.
Once the ingot is cool, the next step is to cut it into wafers. First, the irregular ends of the cylinder are cut off with a wire saw. Then, the rounded sides of the cylinders are cut off, leaving them with a square cross-section with rounded corners. (Some very early solar panels used round cells, but the industry quickly moved to squared cells for greater efficiency of space.) Finally, the squared-off ingots are pressed through a wire web, which slices them into wafer-thin cross sections.
Thanks to the addition of boron to the melting crucible, these thin silicon wafers have a positive electrical orientation, but they are not yet capable of creating a current. For that to happen, they must undergo a series of manufacturing steps. The first of these involves etching the cells to give them a rough texture (on a microscopic scale) for greater light absorption. After that, they’re ready to become photovoltaic cells.
In order for the cells to be capable of generating an electric current, they must be treated so that one side becomes negative. This is done by diffusing phosphorus in a thin layer on the cell’s surface to form a positive/negative junction.
Next, the surface is treated with an anti-reflective coating such as titanium dioxide, or with silicon nitride, which gives them their dark color and helps reduce reflection for optimal absorption of solar energy. Finally, metal circuitry is printed on both sides of the cell. This allows it to collect and transmit the power for practical use.
Assembling solar cells into panels
Once the individual solar cells are finished, they’re ready to be assembled into functioning solar panels. This is primarily done by robots for maximum efficiency and precision.
First, each cell is encapsulated in silicon rubber or ethylene vinyl acetate. This protects the delicate circuitry from shock, dust, moisture and other environmental hazards.
Next, a series of cells is soldered together into a “string”—a single line of 10 or so connected cells. A group of strings is then laid out in a rectangular matrix and laminated onto glass. Then, the panel is fit into a sturdy aluminum frame and equipped with a junction box that enables the panel to be joined with other panels in a solar array, which is then connected to batteries or the grid.
Quality control is important when manufacturing solar panels in order to ensure optimal efficiency. The best solar panel manufacturers engage in continuous inspection and testing, from raw materials to individual cells and components, to finished panels. When choosing panels, be sure to ask about the quality control measures taken by the manufacturer.
Solar panel installation
Solar panels are a marvel of manufacturing, but even the best panels won’t perform optimally unless they’re properly installed. It’s very important for any solar system to be properly sited and sized for the desired application.
If you’re planning to install solar on your home, you’ll get the most out of your panels by working with a competent installer. Look for a company that’s properly licensed and insured, and has experience installing solar in your area and on your roof type. That way, you’ll be sure to justify the energy and resources used in manufacturing and delivering your panels.
Thinking about putting solar panels on your roof? Read our Solar PV Buyer’s Guide>>
[box]Ryan McNeill is the president renewableenergysolar.net, one of the Mid-Atlantic’s largest residential solar energy companies.[/box]