Solar energy obtained from solar panels is actually one of the cleanest energy sources even when you factor in the manufacturing process and end of life disposal. Most of the environmental impact actually occurs during production due to the electricity coming from coal and other unclean energies. Replacing these power sources with clean energies would greatly reduce the impact of solar panels on the environment.
Personal Solar Power vs Solar Farms
Many of the environmental impacts of solar energy come from things like land or water use and are only relevant to industrial power generation from solar farms. Solar energy on a personal scale is easily among the top environmentally friendly energy sources since panels are often mounted to roofs where land is already being used for buildings and concentrators, which take water, aren’t often used.
Another important consideration is that some solar systems might use of things like batteries for power storage. This will increase the impact of the overall system by quite a bit because batteries are difficult to dispose of when they do reach the end of their life. Luckily in many applications the power can be fed directly into the existing electrical grid so storage is unnecessary. Both residential and business type systems can be fed directly into the grid and batteries are primarily used in applications where the power is intentionally disconnected from the energy grid. One drawback of this low impact “free storage” achieved by hooking solar panels directly to the energy grid is that no power could be drawn from the system once the sun goes down.
Solar Panel Manufacturing & Waste
Silicon is the second most common element found on Earth behind Oxygen making it extremely environmentally friendly to mine when compared to things like coal and uranium. It is also relatively inert and only poses a danger if silicon dust is inhaled making it safe to work with as long as you take precautions. Even though silicon is a benign material and clearly quite abundant, other chemicals used and created during the solar cell manufacturing process pose more serious environment and health risks.
Cadmium, tellurium, gallium, arsenide, germanium, and indium are just a few of the chemicals used in the manufacturing of some solar cells. Although the currently popular crystalline silicon photovoltaic cells don’t use these chemicals they do use lead and produce various waste products such as sulfur hexafluoride and nitrogen trifluoride which is 17,000 times more powerful as a greenhouse gas than carbon dioxide. The environmental impact of these high efficiency solar cells depends on extended producer responsibility and the proper disposal of toxic components. The solar industry at large is not currently subject to extended producer responsibility but many believe it should be. Emerging technologies like organic solar cells or polymer photovoltaics make use of organic semiconductors greatly reducing any concerns about disposal.
Another major concern is photovoltaic panels being produced in other countries with lax environmental protection laws. Western countries don’t typically pose a problem as environmental protection regulations already exist but a large number of photovoltaics come from countries like China who are known for their poor track record with electronic waste. Recently reports came out that Luoyang Zhonggui High-Technology Co. was dumping toxic byproducts like silicon tetrachloride on nearby farms created from polysilicon production intended for solar cell manufacturing around the world. It was surprising because this was a “green energy” company who might be expected to hold themselves to higher environmental standards.
Solar Energy & Greenhouse Gas Emissions
Compared to the current national energy landscape in the US replacing 1,000 kWh with solar power would reduce the emissions of sulfur dioxide by 8 pounds, nitrogen oxides by 5 pounds, and carbon dioxide by more than 1,400 pounds. Considering the average American home used 11,040kWh in 2008 that is a reduction of 7.7 tons of carbon dioxide being released into the atmosphere per American home by switching to solar energy. There are some concerns over extremely potent greenhouse gases produced during the manufacturing of solar cells as mentioned above. For example nitrogen trifluoride is 17,000 times more powerful as a greenhouse gas than carbon dioxide.
Solar Energy Land Use
Solar energy land use is actually a major environmental concern for solar power. Solar power plants use large tracts of open and sunny land. In some cases this has put solar power companies at odds with conservationists. The Quechan, a Native American tribe, sued the U.S. government over damage to “cultural and biological resources of significance.” The suit referenced the land being an essential habitat for the flat-trailed horned lizard which is important to the tribal creation story. Tessera, the developer of the solar site, agreed to purchase an equal amount of land that is also habitat for this lizard in order to offset the project’s impact.
Solar power company BrightSource Energy ran into similar problems at a proposed 4,000 acre solar energy generation station that would impact the desert tortoise and an area of rare desert plants. They came back with a new proposal that reduced the acreage by 12% and tried to avoid the area of rare plants but the U.S. Fish and Wildlife Service said that the compromise did not fully resolve their concerns.
In spite of these land use concerns, the solar energy footprint necessary to provide all electricity from photovoltaic sources is less than 2% of the crop and grazing land in the United States in addition to being less land than is currently used to produce corn for ethanol. It is also less land than is used for coal power when land for the coal mining operations is included.
Solar Energy Water Use
A more pressing concern may be the water use of some solar energy generation plants. When Solar Millennium announced they planned to build two large solar farms in Nevada, US the public came out against it because it was revealed the power plants would require 1.3 billion gallons of water per year consuming 20% of the available water in the region. Unfortunately the fact that solar energy operates more efficiently in high insolation areas means that plants are often built in deserts where water is obviously extremely limited.
Coal fired plants use 110-300 gallons of water per megawatt hour, nuclear plants use 500-1,100 gallons/MWh, and a solar parabolic trough plant uses 760-920 gallons/MWh. The water in solar power generation is used to either cool systems or boiled to produce steam for driving turbines in the case of concentrators like our example of the parabolic trough plant. It is important to note however that photovoltaic panels do not consume water so this is primarily a concern of concentrated solar power projects where water is used as the thermal mass.
Solar Panel Disposal
Recently an association known as PV CYCLE was created to handle end of life issues relating to solar energy. This organization is composed of members of the photovoltaic energy industry who take on a voluntary commitment to “assume the producer’s responsibility for the complete life cycle of our products.” Since photovoltaics have only recently been industrially produced there has yet to be any real demand for solar cell recycling. Though at this point it is promising that the industry appears to be self regulating, for the time being, and is preparing several years in advance of the first wave of end of life PVs.
Many people would like to see extended producer responsibility (ERP) implemented in the solar industry and some companies like FirstSolar have voluntarily taken this on. ERP would force solar panel manufacturers to take back their products at end of life and be responsible for proper recycling and disposal. Some of the chemicals involved in certain photovoltaics like CdTe (Cadmium-Telluride) or CIGS (Copper Indium Gallium Selenide) solar cells are actually quite valuable and should provide an incentive for manufacturers to recycle their products. For example Tellurium is a somewhat rare element because it isn’t primarily being mined for and as a result only a small amount (industrially speaking) is produced every year. Indium is quite rare as well and thus extremely expensive so solar panel manufacturers would essentially be wasting money by not recycling it.
Also as mentioned previously some new technological advances in organic and polymer solar cells could allow for very disposal friendly panels to be created. Currently efficiency for these cells is at around 8% making them unattractive but they are a very promising future technology.
1. NREL; Energy Payback: Clean Energy from PV
2. U.S. Energy Information Administration
3. LA Times; Native Americans sue U.S. over solar power plant
4. ScienceDirect; Land-use requirements and the per-capita solar footprint for photovoltaic generation in the United States
5. PV CYCLE; Our voluntary commitment
6. NY Times; BrightSource Alters Solar Plant Plan
7. NY Times; Western Water War Slows Some Solar Projects
8. U.S. DOE; Energy Demands on Water Resources
9. Scripps Institution of Oceanography; Potent Greenhouse Gas More Prevalent in Atmosphere than Previously Assumed
10. Washington Post; Solar Energy Firms Leave Waste Behind in China