Photovoltaic Power: Pollution Paradox?

Solar energy is a rapidly growing market, which is generally good news for the environment. However, there are potential environmental impacts associated with solar power, including land use, habitat loss, water use, and the use of hazardous materials in manufacturing. While solar photovoltaic (PV) cells do not use water for generating electricity, some solar power plants may require water for cleaning solar collectors and concentrators or for cooling turbine generators. Additionally, the production of PV cells can generate toxic substances that may contaminate water resources. The hazardous chemicals used in manufacturing PV cells must be carefully handled to avoid releasing them into the environment, and some types of cells may require special handling at the end of their useful life. Although PV cells do not produce air pollution or greenhouse gases when operating, there are emissions associated with other stages of the solar life cycle, such as manufacturing, materials transportation, installation, maintenance, and decommissioning.

Manufacturing and transportation of PV cells

The manufacturing of PV cells does involve the use of hazardous materials, which can generate toxic substances that may contaminate water resources if they are not carefully handled and disposed of. Some PV cell technologies use heavy metals, which may require special handling at the end of their useful life. The production of high-purity polysilicon for solar cells, for example, is a rapidly growing industry in China, but it has been associated with serious pollution problems and high energy requirements at some facilities.

PV cell manufacturing also requires water, though the amount varies depending on the plant design, location, and type of cooling system.

The transportation of PV cells does produce emissions, but it is a relatively small proportion of total PV emissions, accounting for only 3%.

The carbon footprint of PV manufacturing is expected to shrink as power systems across the world transition away from fossil fuels. However, the rapid growth of the PV industry, particularly in China, has led to concerns about the world's ability to develop resilient supply chains. As countries work towards reducing emissions, they must ensure that their transition to a sustainable energy system is built on secure foundations.

Land use and habitat loss

Solar energy is a rapidly growing market, which is generally good news for the environment. However, the potential environmental impacts associated with solar power can vary greatly depending on the technology used. These impacts include land use and habitat loss, water use, and the use of hazardous materials in manufacturing.

Large-scale solar power plants can affect the environment at or near their locations. Clearing land for a power plant may have long-term effects on the habitats of native plants and animals. The land impacts from utility-scale solar systems can be minimized by situating them at lower-quality locations such as brownfields, abandoned mining land, or existing transportation and transmission corridors. Smaller-scale solar PV arrays, which can be built on homes or commercial buildings, also have a minimal land use impact.

The production of some photovoltaic (PV) cells generates toxic substances that may contaminate water resources. Renewable energy installations can also disrupt land use and wildlife habitat, and some technologies consume significant quantities of water. For instance, some solar power plants may require water for cleaning solar collectors and concentrators or for cooling turbine generators. Using large volumes of groundwater or surface water for cleaning collectors in some arid locations may affect the ecosystems that depend on these water resources.

PV panels have been linked to substantial impacts on species and ecosystems, the first and most obvious one being the degradation of natural habitats. They may also lead to the mortality of individuals and the displacement of populations. However, evidence on the effects of PV panels on biodiversity has been building up only fairly recently. Many other potential adverse effects of PV installations have been hypothesized in various technical reports, but little empirical evidence is usually provided by authors.

Water use

Solar energy is a rapidly growing market, which is generally good news for the environment. Unlike fossil fuels, solar energy does not produce air pollution or greenhouse gases when operating. However, the generation of electricity using solar photovoltaic (PV) cells does have some environmental impacts, including water use.

PV cells are electrically connected in a packaged, weather-tight PV panel (sometimes called a module). PV panels vary in size and in the amount of electricity they can produce. Solar PV cells are grouped in panels, and panels can be grouped into arrays of different sizes to power water pumps, power individual homes, or provide utility-scale electricity generation. When the sun is shining, PV systems can generate electricity to directly power devices such as water pumps or supply electric power grids.

PV cells do not use water for electricity generation. However, some solar power plants may require water for cleaning solar collectors and concentrators or for cooling turbine generators. Using large volumes of groundwater or surface water for cleaning collectors in some arid locations may affect the ecosystems that depend on these water resources. In addition, the water returns from power plants can be significant sources of thermal pollution and may include discharges of chemical pollutants, such as chlorine or other biocides used in cooling towers.

The production of PV cells and panels also has environmental impacts. The hazardous chemicals used for manufacturing PV cells and panels must be carefully handled to avoid releasing them into the environment. Some types of PV cell technologies use heavy metals, and these types of cells and panels may require special handling when they reach the end of their useful life. The production of some PV cells generates toxic substances that may contaminate water resources. Most PV panels produced today are made of single or multicrystalline silicon, and the production of high-purity polysilicon for solar cells has high energy requirements and serious pollution problems at some facilities.

U.S. environmental laws regulate the use and disposal of hazardous materials, and the U.S. Department of Energy is supporting various efforts to address end-of-life issues related to solar energy technologies, including recovering and recycling materials used to manufacture PV cells and panels. However, given the current very high recycling costs, there is a risk that used panels will end up in landfills.

Use of hazardous materials

Solar energy is a renewable, sustainable, reliable, and clean source of energy. However, like any industrial product, there are health and environmental impacts associated with the manufacture of solar cells and panels. The production of some photovoltaic (PV) cells generates toxic substances that may contaminate water resources.

The PV industry uses hazardous materials, including heavy metals, and flammable and toxic substances, which can pose environmental and occupational risks. These hazardous chemicals must be carefully handled to avoid releasing them into the environment. Some PV cell technologies use heavy metals, and these cells and panels may require special handling at the end of their useful life. The US Department of Energy is supporting various efforts to address end-of-life issues related to solar energy technologies, including recovering and recycling materials used to manufacture PV cells and panels. The solar recycling industry is growing and is supported by policies and regulations, with producers of solar panels in the EU financing the recycling of solar panels.

The most common semiconductor material used in solar cells is silicon, which accounts for approximately 95% of the modules sold today. Silicon is the second most abundant material on Earth (after oxygen) and is also the most common semiconductor used in computer chips. Other semiconductor materials used in PV cells include cadmium telluride and amorphous silicon. Organic PV (OPV) cells are composed of carbon-rich (organic) compounds and can be tailored to enhance specific functions of the PV cell, such as bandgap, transparency, or color. OPV cells are currently only about half as efficient as crystalline silicon cells and have shorter operating lifetimes, but they could be less expensive to manufacture in high volumes.

While solar energy technologies and power plants do not produce air pollution or greenhouse gas emissions when operating, there are emissions associated with other stages of the solar life cycle, including manufacturing, materials transportation, installation, maintenance, and decommissioning and dismantlement. Most estimates of life-cycle emissions for photovoltaic systems are between 0.07 and 0.18 pounds of carbon dioxide equivalent per kilowatt-hour.

End-of-life issues

Solar energy technologies and power plants do not produce air pollution or greenhouse gases when operating. Using solar energy can have a positive, indirect effect on the environment when solar energy replaces or reduces the use of other energy sources that have larger effects on the environment. However, the production of photovoltaic (PV) cells and panels generates hazardous materials and toxic substances that may contaminate water resources. These include gallium arsenide, copper-indium-gallium-diselenide, and cadmium-telluride, which are found in thin-film PV cells. Some PV cell technologies also use heavy metals. These hazardous materials must be carefully handled to avoid releasing them into the environment and may require special handling when the PV cells and panels reach the end of their useful life.

U.S. environmental laws regulate the use and disposal of hazardous materials. The U.S. Department of Energy is supporting various efforts to address end-of-life issues related to solar energy technologies, including recovering and recycling materials used to manufacture PV cells and panels. However, the replacement rate of solar panels is faster than expected, and the high recycling costs pose a real danger that all used panels will go to landfills. As the solar PV market grows, so will the volume of end-of-life panels, and these will need to be properly recycled or disposed of.

While in use, solar panels provide clean, renewable energy from the sun, and their prevalence as an energy source has been growing. In 2020, solar panels provided about 40% of new U.S. electric generation capacity, compared to just 4% in 2010. Crystalline silicon solar PV represents over 95% of solar panels sold today. These panels typically contain small amounts of valuable metals, including silver and copper, which can be recovered through recycling.

Overall, while the use of solar panels for electricity generation has a much lower environmental impact than traditional power generation systems, there are still end-of-life issues that need to be addressed to ensure proper disposal and recycling of PV cells and panels.

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