When I hear the words “solar panel” my heart skips a beat. My entire life I’ve heard of the limitless benefits of these amazingly simple devices that have the potential to save us from the ravages of a man-made runaway greenhouse effect. Like most, I trusted experts when they said that solar panels were a source of clean renewable energy with absolutely no downsides and, like most, I was wrong. As with almost anything human beings manufacture, solar panels are far from being environmentally harmless, but they fair much better than other forms energy production.

There are two main types of solar energy production; photovoltaic (PV) and concentrating solar thermal plants (CSP). PV solar cells use complex overlays of heavy metals and other elements to generate electricity directly from sunlight, and are usually what people mean when they refer to “solar panels.” CSPs basically consist of a large tower surrounded by thousands of mirrors that redirect the sun’s thermal energy towards the tower where steam rises to spin a turbine.

Photo: Imaginechina/Corbis

Over 90 percent of PV cells are made by the process of purifying silicon into what’s called polysilicon and stripping it into small wafers that get laced with semiconductor metals and assembled together (Mulvaney 2014). The combination of elements provides the basic mechanism for the photovoltaic effect which produces usable electricity. Production of polysilicon requires combining silicon with dangerous hydrochloric acid resulting in a highly toxic chemical called silicon tetrachloride. The polysilicon wafers are cleaned with hydrofluoric acid which is deadly if ingested by plants or animals. The production stage of these PV cells creates highly toxic waste which, if disposed of improperly, can have disastrous environmental and health effects. Alternatively, PV cells can be made by a new method which involves assembling thin films of either plastic, glass, or metal and lacing them with layers of semiconductor metals. This process avoids the toxic byproducts created by the polysilicon wafer method, but it requires layers of cadmium telluride and cadmium sulfide, which are known carcinogens. Strict procedures and safety regulations must be adhered to in order to prevent workers from being exposed to any of these toxic compounds during the manufacturing process.

Photo: Piotr Zajda/Shutterstock

Although the energy production process that happens within the PV cells themselves doesn’t produce any greenhouse gases, the energy production processes that fuel the manufacturing of PV cells often do. The majority of the solar industry’s PV cell components are created and assembled in China, and the primary source for the energy fueling those factories comes from coal power (Mulvaney 2014). Fossil fuels are also used in the collection, transportation, and export of PV cells and their components. Fossil fuel dependence in the industry can be partly circumnavigated by substituting other solar plants as energy sources for PV cell manufacturing. While it’s important to remember that solar panels don’t have the spotless carbon footprint many think it does, its carbon impact is still significantly less than more widely used energy sources. PV cells have an estimated lifecycle emission of  0.07 to 0.18 pounds of CO2 for every kilowatt-hour of energy produced, which is still better than the 0.6 – 2.0 pounds of CO2 per kWh produced by natural gas or the 1.4 – 3.6 pounds of CO2 per kWh produced by coal (Union of Concerned Scientists 2013).

Solar panel production and use can have land and water impacts as well. PV systems require an estimated 3.5 to 10 acres of land for every megawatt of usable electricity produced while CSP systems can require anywhere from 4 to 16.5 acres (Union of Concerned Scientists 2013). This impact can be mitigated by putting solar plants in deserts or barren farmland where more complex ecosystems aren’t already present. Small-scale PV cells, like those used to power family homes, often sit on rooftops and don’t require any additional land usage. Additionally, CSP systems can require 600 – 650 gallons of water for each megawatt-hour produced (Union of Concerned Scientists 2013). This doesn’t include water used to clean solar panels regularly.

PV cell components and solar panels themselves can be recycled for their precious metals and other raw materials, but it isn’t very cost efficient so most solar industries aren’t motivated to reuse PV cells. The panels can be sold to other industries to be disassembled since they are often made out of useful materials like glass, silicon, and metal. PV cells have a 25 to 40 year “lifespan,” or period where they are considered as efficiently producing power. In reality, common PV cells degrade in efficiency at about 1% per year, so they could theoretically continue producing electricity for decades (Stahley 2017).

Solar plants actually require more labor per kilowatt of electricity produced than more pervasive coal or natural gas plants, and thus provides more jobs (Union of Concerned Scientists 2015). Of course, I am assuming solar panels are made and used at a uniform efficiency, whereas the environmental and social impacts vary greatly depending on the manufacturer and the regulations in the state/province and country that the solar panel is made. Overall, solar panels represent the cleanest and most sustainable source of energy that we’ve found so far, but the negative environmental and health impacts involved with solar power production are far from what our goals should be for a sustainable energy source. The good news is that the solar power industry is quite new and quite aware of ways to minimize their environmental impacts. New methods of solar technology that use less harmful compounds are gaining more traction in the industry, and solar panels themselves are becoming increasingly more efficient and popular.

References

Stahley, Brook. “Commercial solar panel degradation: What you should know and keep in mind.” Commercial Solar Panel Degradation: What to Know and Keep in Mind, Sunpower, businessfeed.sunpower.com/articles/what-to-know-about-commercial-solar-panel-degradation

UCS. “Concentrating Solar Power Plants.” Union of Concerned Scientists, www.ucsusa.org/clean-energy/renewable-energy/concentrating-solar-power-plants#.WnjLD8lG1o4.

UCS. “Environmental Impacts of Solar Power.” Union of Concerned Scientists, www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/environmental-impacts-solar-power.html#.Wni_oslG1o4.

Mulvaney, Dustin. “Solar Energy Isn’t Always as Green as You Think.” IEEE Spectrum: Technology, Engineering, and Science News, 13 Nov. 2014, spectrum.ieee.org/green-tech/solar/solar-energy-isnt-always-as-green-as-you-think.

Nunez, Christina. “How Green Are Those Solar Panels, Really?” National Geographic, National Geographic Society, 19 Sept. 2017, news.nationalgeographic.com/news/energy/2014/11/141111-solar-panel-manufacturing-sustainability-ranking/.

“Solar.” IER, Institute for Energy Research, instituteforenergyresearch.org/topics/encyclopedia/solar/.

UCS. “Solar Power Plants: Large-Scale PV.” Union of Concerned Scientists, www.ucsusa.org/clean-energy/renewable-energy/solar-power-plants-large-scale-pv#.WnjDNslG1o4.