Connecticut River Dam debate shows hydropower is more complex than just blocking a lot of water

Editor’s Note: No, you’re not confused as to what day it is. The Granite Geek column that previously aired on Tuesday has been moved to Monday, while the COVID tracking column has been moved to Tuesday for data logistics reasons, starting tomorrow.

Dams appear to be pretty straightforward things – they’re big things that block water – but a license renewal effort for three dams on the Connecticut River shows it can get complicated when electricity is added to the mix.

“It would be unique for us,” said John Ragonese of Hydro du Grand Fleuve, a company that owns and operates 13 hydroelectric projects in the Northeast, including the three in question that it acquired in 2017 from TransCanada.

Ragonese’s title is FERC License Manager but before we dive into acronyms, a quick recap.

Most of us think that dams hold or hold so much water that rivers become lakes, and then release some of that water through valves as desired. The Hopkinton-Everett Flood Control dam is typical.

But many of New Hampshire’s 4,800 dams are called run-of-the-river. They let the river flow without holding anything back. If they are hydroelectric dams, they divert part of the water through canals as it passes to turn turbines and generate electricity.

By the way, this surprisingly high number of dams in New Hampshire is correct. Most are tiny, often built for long-gone sawmills, but we also have plenty of larger ones, including 22 on the Connecticut River.

Run-of-river dams are cheaper to build and operate and cause less damage to the environment than retaining dams, but also generate less electricity, since the power of the water is a function of the distance it falls, and offer less control over how much and when they can generate power.

The three dams in question here – Wilder, Bellows Falls, and Vernon – have always been reservoir hydroelectric dams. Great River Hydro wants to change that and instead operate them as run-of-river dams, in part because it reduces environmental concerns that could prevent license renewal by the Federal Energy Regulatory Commission, or FERC. (Now you understand Ragonese’s job title.)

They have applied this month and hope to have permission by the summer.

Because these dams have fairly small holdbacks, three to five feet high, running over the water will be relatively easy, Ragonese said. “There will be no change in the turbines, no modification of the dam for the most part.”

So how is it complicated? The electricity market.

ISO-New England, the people who run the six-state power grid, have established what is called a capacity market which they believe is necessary to ensure that we don’t have blackouts during a polar vortex. or a summer heat wave. Not everyone agrees that this market is necessary; some see it as a subsidy for inefficient power plants.

Power plants bid on the capacity market with the guarantee that they can produce a certain amount of electricity on demand, no matter what. If their price is low enough, ISO-NE takes care of it. They are paid for ensuring whether electricity is needed or not – this is where applications for subsidies arise – but they also face heavy fines if they cannot produce when their electricity is needed.

To my surprise, Ragonese said Great Hydro would offer these plants to the capacity market even after going run-of-the-river. This is the aspect that will be unique for the company.

It seems crazy to me. How can you be sure that you can produce enough electrons on demand during, say, a long heat wave that is part of a drought that cuts off the flow of the river? One way to tell the difference between a hydroelectric retaining dam and a run-of-river dam is for the former to plan its discharges and its electricity production while the latter does not.

Despite this, Ragonese said the Great River experience and some proprietary approaches, including the occasional use of a small amount of impoundment (a foot or less), would make it work. It remains to be seen whether FERC agrees and grants the new operating license.

Part of the company’s confidence comes from ever better forecasting and modeling of precipitation, soil conditions, runoff, and other factors that affect flow throughout the watershed, the area that flows into the river. Connecticut River upstream of each dam. Dams don’t just wait to see how water appears every day; they increasingly predict future supply.

In this way, dams are like wind farms, which use constantly improving weather forecasts to know in advance how much wind they will have and therefore how much electricity they are likely to produce on the road.

A complicating factor for dams is the fact that the rivers are long and lean, which means that the entire supply does not change at the same time. It can rain in one part of the watershed but not in another, and the water in the river channels does not move very quickly. It would take at least two days for a raindrop falling on the Quebec border to reach Long Island Sound, even if there were no dams.

“The longer they are, the more other developments there are going on – the water comes upstream but it really doesn’t hit the dam for hours and hours,” Ragonese said. “You see (the water) as a tilt… It’s not flat. “

I hadn’t really thought that the water in the rivers was sloping, but then again, I didn’t have to operate a dam either.

The change in operation of Great River is even more surprising as check dams become more and more valuable in the age of renewable energy. They can act like a big battery, holding water when wind and solar power is plentiful and releasing it for power generation when it isn’t. This ability to help stabilize the system is worth the money, and it seems to me Great River won’t be able to get as much out of it.

But whatever the bottom line, it shows that even large stationary objects can be more complicated than you think.

(David Brooks can be reached at 369-3313 or [email protected] or on Twitter @GraniteGeek.)


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