Hydroelectric projects can be terrific for meeting peak electricity load demands; if they store water in reservoirs, they can release it more-or-less instantly to generate electricity just in time to meet the demand. This is what pumped storage hydroelectric facilities are designed to do from the start, usually pumping water uphill from one reservoir to another to store energy, then letting it flow back down when energy is needed. The only potential significant environmental impact from this operational phase would result from reservoir water-level changes during the cycle. In a non-pumped-storage situation where the reservoir is behind a dam on a river and the peaking strategy with the best economics is to release practically no water until needed for peaking, then to release a lot, there are plenty of potential downstream environmental impacts. Such a strategy is utilized in the mid-Atlantic US by some utilities. In a paper just accepted by the journal Environmental Science & Technology, researchers at the University of North Carolina and Duke University looked at releases at Roanoke Rapids Dam on the Roanoke River and tried to figure out if adding wind to the mix of renewable power would increase or decrease these potential impacts (Kern et al. 2014). Despite earlier suggestions that it would, they decided not, based on the model results that predicted very little increase in the downstream “flashiness” over current operational conditions, even with 25% new wind market penetration….
Kern et al. used an electricity market (EM) model for the Dominion Zone of PJM Interconnection, a 23 GW electric system, to which the Roanoke Rapids Dam can contribute, at most, 100 MW. The system gets its energy from a mix of coal, natural gas combustion and combined cycle turbines, nuclear, pumped storage hydropower, conventional hydropower, biomass, and oil. Pumped storage hydropower provides 6.9% of the power, but hydropower of the sort they are interested in provides only 2.1% of it, and the dam in question could provide less than half a percent of the overall mix when operating at full capacity. Adding wind power of up to 25% average annual market penetration [a lot] could conceivably substantially increase the need for peaking hydropower to make up for unexpected intermittencies in the wind, leading to very high real-time electricity prices, which might then encourage a much flashier operation of the Roanoke River Dam to maximize revenues there. It turns out that if the wind market penetration were as high as 25%, there would be a modest increase in downstream flashiness, but the authors figure that the environmental impacts of building the dam in the first place, and those of its current operation, far outweigh those due to any additional effects of even 25% windpower penetration.
Kern, J., Patino-Echeverri, D., Characklis, G.W., 2014. The Impacts of Wind Power Integration on Sub-Daily Variation in River Flows Downstream of Hydroelectric Dams. Environmental Science & Technology. (DOI: 10.1021/es405437h, Accepted for publication) http://bit.ly/1knbCuD