Learn which chemicals make solar power possible

Solar power currently makes up a small percentage of the power usage in the U.S., only about 0.2 percent according to the Institute for Energy Research. Although this number seems small, it's definitely an increase compared to past levels.

In 1997, the U.S. produced 334.2 megawatts of solar energy, which has grown to 6,220.3 megawatts in 2013. Many experts look to it as a key renewable source of energy going forward.

Solar, along with wind, tidal and geothermal energy sources are often referred to as clean energy. And while solar power doesn't create the greenhouse gases and carbon emissions of other forms of power when in use, it does require a number of chemicals to create the photovoltaic or PV cells and harness solar power.

Like fracking, solar power is reliant on a variety of chemicals to work successfully and efficiently. Check out some of the most common chemicals used for solar power and how each plays a role.

Hydrochloric acid, copper, trichlorosilane gas and silicon waste
Like many electronics on the market today, PV cells require the use of silicon for semiconductors. Silicon can be mined in the environment, with sand or quartz and then processed at high temperatures that burn off the oxygen and leave you with a 99.6 percent pure metallurgical grade silicon, Solar Industry magazine outlined. 

However, 99.6 percent isn't high enough for semiconductor use, so this metallurgical grade silicon must go through a second, chemical-rich process. The silicon is mixed with copper and hydrochloric acid to produce trichlorosilane gas, which is then reduced with hydrogen to make silane gas. The silane gas is heated into molten silicon which leads to silicon crystals that can be reformed and used for PV cells and micro chips, Solar Industry explains. 

The magazine notes that the entire process is necessary to get the pure silicon material, but very energy intensive and materially wasteful, with about half of the initial pure metallurgical silicon lost in the process. Additionally, silicon dust presents safety dangers and silane gas is incredibly explosive. 

While silicon production uses an array of chemicals and is a key aspect of PV cell creation, it's not the only chemical used. As Stanford University's Stanford Magazine explained, cadmium is an important part of creating the cadmium telluride thin film

Cadmium is a naturally occurring earth metal, produced from smelting zinc, copper or lead ore. The U.S. Environmental Protection Agency explained that inhaling or being exposed to cadmium can lead to cancerous and noncancerous damage to lungs and organ systems. 

Stanford Magazine pointed out that in addition to being dangerous to human health, cadmium is also expensive, so its use in cadmium telluride thin film is closely monitored. Only about half the cadmium used in the process makes it into the film, so the rest is waste. The waste cadmium can be used in other parts of the cadmium telluride thin film production process, but the risk of cadmium polluting the water or air from a fire or improper disposal exists, the magazine explained. 

Nitrogen trifluoride and sulfur hexafluoride 
Although solar power doesn't produce  greenhouse gases while in use, the one's it does release during production are important, according to the Voice of San Diego. 

Ray Weiss, a professor of geochemistry at the Scripps Institution of Oceanography, told the Voice of San Diego, that some solar panel production releases nitrogen trifluoride, which is 17,000 times stronger than carbon dioxide. Efforts are made to contain the gasses produced, but they often leak out Weiss explained. 

Sulfur hexafluoride is another greenhouse gas that some solar panels release when they're being made. It's 22,800 times more potent than CO2, according to Deutsche Welle.

Copper indium selenide and copper indium gallium (di)selenide 
Stanford Magazine also pointed out that copper indium selenide and copper indium gallium (di)selenide have been used in PV cells previously. These chemicals can be dangerous to people working on PV cell production, as they're toxic at low levels. The magazine explained that many are moving away from using these chemicals in current processes to avoid risks to workers and the environment. 

The importance of chemicals 
Many chemicals are critical for manufacturing better and cleaner solar panels, but they can also present a a very real risk to people and the environment during production and afterward. Panels made with toxic and environmentally dangerous chemicals may release these chemicals to the environment when damaged or disposed of, which underscores the importance of responsible and safe use of potentially dangerous chemicals.