British Columbia is a great place to drive an electric vehicle. Why? Most of our electricity comes from hydroelectric dams (but not most of our energy, see “Don’t get too smug about B.C.’s hydroelectric”
But dams, once the go-to source of low carbon electricity, are problematic from an environmental perspective.
We know that dams cause extensive ecological damage to the flora and fauna overrun by the reservoir. Dams also produce more methane and CO2 than was previously suspected. Rotting materials, deep underwater without access to oxygen, break down. This produces large amounts of methane and CO2. The methane is 30 times more powerful a greenhouse gas than CO2.
Reservoirs created by dams trap rotting material deep underwater, producing methane, a greenhouse gas 30 times as powerful as CO2
This “carbon cost” is much higher than emission from natural lakes or marshes; the emission from dams is much closer to human-created water bodies such as rice paddies. The Site C dam is expected to emit between 4-6 million tonnes of CO2 equivalent over a 100-year operating life, with most emissions occurring within 10 years after the flooding.
READ MORE: U.S. is ripping us off on water
Given a critical need to switch to low carbon power, what are the alternatives to the environmental impact of hydro power? Ask John Waldman. In research published in the scientific journal “Nature Sustainability”, Waldman (along with Shailesh Sharma, Shahab Afshari and Balázs Fekete) conducted a thought experiment: What if you removed the dam, and used some of the area now underwater for photovoltaic panels?
The first question: Is it possible to generate enough energy by replacing reservoirs with solar farms? The answer is a resounding “yes”. In fact, given the efficiency of solar panels today, you need less room for photovoltaics than you would cover with water for a dam.
The idea of restoring habitats flooded by reservoirs, and replacing the clean energy by putting up some solar panels is striking. What is even more impressive is that after we do the math, it turns out that we only need 13% of the land area flooded by dams to create the same amount of electricity.
Research by Waldman shows that we could replace all the electricity coming from dams by using 13% of the reservoir land area for solar energy
It would be premature to start dismantling all of our dams. Many dams have other uses, such as controlling flooding and providing drinking water. Dams also play two critical roles in maintaining our electricity grid: serving as “dispatchable energy” and as a key “black-start” resource. First let’s talk about “peaker plants”. The amount of electricity we need changes during the day and is not completely predictable. In order to meet a sudden spike, you need a source that can respond quickly – this is called “dispatchable” energy. In the table we list sources of electricity that can and cannot react quickly to demand. Hydro and natural gas, marked with an asterisk, are considered the best source of dispatchable energy.
Hydro and natural gas are considered the most “dispatchable” resources.
In the event of a widespread power outage, some plants can restart themselves, while others require electricity to start producing electricity. The ability to do this makes them a “black-start” resource. Hydro is often designated, coming online and then providing electricity to fossil-fuel or nuclear stations. (Here technology is changing things. In California they have tested a battery storage system, to provide a black-start to a natural gas plant. Clearly solar+storage could play an important role.)
The Waldman and collaborators thought experiment is useful in two ways. First it demonstrates that photovoltaics are not only capable of replacing hydro energy, but if you consider the environmental “footprint” they would be a significant improvement. Secondly it suggests that as our ability to store solar power matures, we could consider replacing hydro power with photovoltaics.
Finally, we live in a world where people use electricity but don’t want it generated anywhere near them. People protest strongly because they oppose any generation in their backyard (nuclear, wind, coal, solar). If we frame the question, not “can we put a powerplant here” but “which power plant would be least disruptive” then solar clearly winds over hydropower.
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Kristy Dyer has a background in art and physics and consulted for Silicon Valley clean energy firms before moving (happily!) to sunny Penticton. Comments to Kristy.Dyer+BP@gmail.com
Kristy’s articles are archived at teaspoonenergy.blogspot.com