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Does it make sense to replace America’s aging dams with solar panels?

Dams are typically seen as the enemy by environmentalists, ever since Hetch Hetchy Valley in Yosemite was flooded against the protests of John Muir. Ed Abbey painted dams as the enemy of his band of misfit ecoterrorists in The Monkey Wrench Gang

The reasons why dams are unpopular among environmentalists are numerous. Some are horrified by the loss of beautiful places like Hetch Hetchy or Glen Canyon. Flooding behind a dam not only destroys wildlife habitat but sometimes covers important paleontological, geological or archaeological sites. Others worry about the impact of dams on fish populations

Silt builds up behind dams, and the water is warmer in a reservoir created by a dam than in the original river. All of this leads to a release of methane created in the new aquatic environment and a loss of biodiversity. In fact, as the original life drowned by flooding die and decay, as much as 0.5 pounds of carbon dioxide equivalent is released per kilowatt hour, barely better than the 0.6 – 2 pounds produced from natural gas generated electricity. 

Migratory fish are stopped or delayed in their movement by dams. Sometimes dams favor invasive non-native fish populations adapted to different environments. Populations of fish in Europe have declined after the building of dams. In China, fish species declined from 107 to 83 after the Xinanjiang dam was built. The same trend of a decline in biodiversity, not only in the flooded region of a river but also downstream, has been shown in Australia and Latin America as well. Dams also impact native fishes negatively in the US.

Political battles have been fought over dams throughout the western US and mostly environmentalists have lost and dams sprouted everywhere people lived out west. For the most part, we’ve passed the time in US history for major dam building. According to FEMA numbers, only 92 dams of any stature were built before 1800 in the United States. The number of dams built increased until 27,715 dams were built in the US between 1951 and 1970. Dam building has slowed down considerably since that time, with 19,506 dams built between 1971 and 1990. Only 5,105 dams were constructed between 1991 and 2007. Now, many of these dams are growing old and there’s a discussion of what should be done. 

Headwaters Economics reports that the US has 87,000 dams more than six feet high and 2 million all together. Of the dams, there are 2,603 in the lower 48 states that generate electricity. It’s estimated that by 2020, 70% of dams will be over fifty years old and will require more and more costly maintenance. It’s estimated that repairing the United States non federally owned dams could cost $51.5 billion. 

Some of those dams still serve a useful purpose while others are potentially reaching the end of their service. With realities such as these, dams across the US have been removed as well as constructed. Since 1912, more than 1,300 dams in the US have been removed, and 62 were removed in 2015 alone.. With the removal of dams and the decommissioning of the connected hydropower plants that many of them keep alive, electrical power becomes an issue. 

Hydroelectricity currently provides about 6% of the United States electricity needs and give constant steady electricity to the grid. New research in Nature suggests that solar electricity could potentially replace the lost electricity from hydroelectric. The research indicates that theoretically, the same amount of electricity as currently generated by dams could be generated by solar panels using only 13% of the land currently occupied by reservoirs. 

Of course, some of the land used by reservoirs wouldn’t necessarily be appropriate for solar panels, so other land might have to be used to make the same amount of electricity. If all hydroelectric dams were removed and only half of the land area they occupied was replaced with solar, it could generate 3.44 times the amount of electricity currently created by hydroelectric. 

Replacing hydroelectric dams with solar panels is an interesting idea, but it’s more complicated than a straight trade of one thing for another. Without a way to store electricity like batteries, solar power is unlikely to be a good replacement for hydroelectricity, which is generated 24 hours a day. Solar also varies per season and not every location that currently uses hydroelectric has equal opportunity for solar. Washington State, for example, has 107 hydroelectric dams, Arizona has 9. On average, Phoenix, Arizona has 299 sunny days per year while Seattle, WA has only 152. Just from this one comparison it’s obvious that some places have a huge advantage than others for solar or hydroelectric. 

All of this leads to a lot of uncertainty about the potential cost of replacing hydroelectric plants with solar panels as well as the local feasibility. Replacing the energy Arizona gets from hydroelectricity seems a lot more doable than doing the same for Washington. There is also the question of environmental impact and what the impact of solar panels is in the long run.

Both solar and hydroelectric systems are forms of renewable energy, with solar having less of a direct impact, mainly coming from the manufacturing of the solar panel itself. Due to the carbon footprint of producing a solar panel, solar actually produces more carbon on average over its lifetime than hydro. There are also some serious problems related to disposing of solar panels. 

Over time, solar panels become less and less efficient, with most functioning at a rate of 85% after 25 years or less. The International Renewable Energy Agency (IRENA) estimates that by 2050 there will be 60 to 78 million tons of solar panel waste. Solar panels are hard to recycle because they’re made from so many different materials and very few facilities exist that are capable of recycling them at all. So, that leaves us with the question: is it better to replace hydroelectricity with solar?

The best way to reduce carbon emissions is to decrease consumption and increase efficiency. Whether solar makes sense as an alternative to hydroelectricity might change depending on the region, and it might also become less problematic as technology develops. For the moment, it’s something that deserves further consideration.                                   

By Zach Fitzner, Contributing Writer

Image Credit: Shutterstock/Gary Saxe

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