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Pumped Hydro: Is it TOO Green?

By Pete Singer
January 6, 2011 | 5 Comments

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In the latest Electric Power Research Institute Journal, an article titled "Hydropower Reservoirs: A Question of Emissions" notes that reservoirs used for hydropower and for pumped-hydro energy storage are not necessarily as green as you might imagine. Or rather, they might be too green: carbon-rich organic material that accumulates on the reservoir floor can be the source of carbon emissions. A recent study of the 90-year-old Lake Wohlen, in Switzerland, for example, found high emissions of methane, as recently reported in the journal of Environmental Science and Technology, in an article titled: "Extreme Methane Emissions from a Swiss Hydropower Reservoir: Contribution from Bubbling Sediments."

The EPRI article notes that hydropower reservoirs have come under criticism for net greenhouse gas emissions. The EPRI report The Role of Hydropower Reservoirs in Greenhouse Gas Emissions (1017971) reviews available information on the subject and examines the potential for U.S. reservoirs to be net emitters. The key finding: actual or potential reservoir greenhouse gas emissions are undetermined at present.

The U.S. Department of Energy (DOE) is funding a three year study through the Oak Ridge National Laboratory to investigate these emissions from seven to eight reservoirs primarily in the southeastern United States and three reservoirs in the Pacific Northwest. EPRI will participate in the study, and funding from the hydropower industry could expand it to reservoirs in other climatic regions and reservoirs of varying sizes and depths.

Addressing hydropower’s emissions was ranked fourth on a list of industry needs established at the 2008 EPRI/DOE Waterpower Industry R&D Prioritization Workshop. The National Hydro Association’s staff recognizes the study’s value and is urging its members to consider supporting this research. The International Hydropower Association (IHA) is collaborating with the United Nations Educational, Scientific and Cultural Organization (UNESCO) to address the “possible role and contribution of hydropower to climate change mitigation and adaptation.” Researchers from multiple continents will examine a representative set of reservoirs. Combined with the U.S. study, these results will provide robust answers, according to the EPRI report.

For more information on Energy Storage, see www.energystoragetrends.com.

Hydropower

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5 Reader Comments

Comment
1 of 5

nigel-morris-167490

January 7, 2011

Presumably the methane comes from vegetation that was previously above the waterline and was inundated when the dam was built and water level rose.

Logging and then burning prior to inundation would ensure that the Carbon in the vegetation from the area to be inundated would enter the atmosphere at least as CO2 rather than Methane and there might be some benefits from any salvaged timber i.e. a type of pre-flaring.

Other causes might be excess run-off of agricultural fertilisers into waterways, which will affect any standing body of water (and some flowing bodies) in which case the issue is not so much hydro facilities as the agricultural practices of local farms, which need to be remedied no matter where their run-off goes.

Comment
2 of 5

Cliff_Goudey

January 7, 2011

If we are to believe this, then shouldn't all lakes and reservoirs be drained.

The EPRI report can be downloaded at: http://my.epri.com/portal/server.pt?space=CommunityPage&cached=true&parentname=ObjMgr&parentid=2&control=SetCommunity&CommunityID=221&PageIDqueryComId=0

That report is unconclusive.

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3 of 5

PeteSinger

January 7, 2011

I imagine the carbon emissions are negligible, but they're not zero. Another downside when it comes to pumped-hydro energy storage is that water evaporates and the stored energy along with it. But again negligible.

Comment
4 of 5

thomas-mayrand-14505

January 7, 2011

Cliff, don't forget natural ponds and lakes have life within that help balance their ecology. Stagnant reservoirs do not.

Comment
5 of 5

jajagabor

January 9, 2011

I don't know whether this has anything to do with sedimentation that occurs to one degree or another above dams, but it might . . . Dams usually cause sedimentation in the areas above where they are placed, and in some cases this can seriously affect their hydropower output negatively.

thomas-mayrand-14505 states that stagnant reservoirs do not have the presence of life that natural (or even artificial for that matter!) lakes and ponds have. I don't know if this is true (or how consistently true), but it is something that needs to be addressed.

There is no question that dams have negative impacts on fish and other aquatic life forms, but the perrenial question is: how much? (especially in regard to other forms of power production, like coal burning, nuclear plants, etc. etc.) I don't pretend to have an authoritive answer, though I am sure there are many that might claim to . . .

Although it is a tough decision, and despite my intense dislike of dams, I would still prefer a dam over a nuclear plant. But you can only build so many dams on a river, and I'm sure we already have too many. Much better would be if we commit ourselves more to solar, wind, "organic rankine cycle" generators (already in production by companies like Infinity Turbine and Electra-Therm, and apparently very cost-efficient), and other renewable technologies such as methane fueled generators (think cow & pig & even human waste etc.!). We're only scratching the surface of the hundreds (or maybe thousands) of things we could do to conserve/reduce consumption and produce it from renewable, safe, and mostly local resources! :)

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