Hydropower Takes Center Stage for AMP

For American Municipal Power Inc., a nonprofit wholesale power supplier to municipal electric systems based in Columbus, Ohio, hydropower is the No. 1 renewable. To this end, AMP is moving forward with four developments along the Ohio River that will provide more than 300 MW of generating capacity for a majority of its 129 members in seven states.

AMP Chief Executive Officer Marc Gerken says hydropower has been “largely ignored” in recent discussions about alternative energy. “Hydro is not a new, shiny, sexy technology,” he said. It’s true, hydropower is not new. Hydroelectric generation comprised about 40% of total generation in the early 1900s. But by 2011, hydroelectricity accounted for just 7%, according to the National Hydropower Association.

Regardless, hydropower in the U.S. is anything but tapped out. About 130,000 sites are available with a capacity of 30,000 MW, according to the U.S. Department of Energy. Another study, by the Electric Power Research Institute, found at least 23,000 MW of additional capacity, including hydrokinetic and wave energy, that could be brought on line by 2025. Under a best-case scenario, the study estimated possible maximum development of 95,000 MW.

Gerken says AMP and its partners turned to hydroelectricity partially because of the reliability of the resource. “I know what I’m going to get out of these units tomorrow. I can’t do that with wind or solar,” he says.

Currently, 67% of domestic renewable generation comes from hydropower, according to NHA. In recent years, environmental groups have criticized hydro projects that require the construction of new dams. But all of AMP’s hydro projects avoid this criticism because they are being sited on existing U.S. Army Corps of Engineers locks and dams. In fact, the Corps’ original intention as part of building the dams where AMP is installing hydro facilities was for run-of-river projects to be constructed at the dams, Gerken says.

AMP’s run-of-river approach achieves ca-pacity factors of 55% to 60%, which is high in comparison with other renewable forms of energy. For example, wind in the Midwest has a capacity factor of 20% to 30%. And the capacity factor of solar is 15% to 18%, Gerken says.

Choosing the dams

In 2006, AMP commissioned MWH to study 10 dams along the Ohio River at which hydro projects had not been developed. Based on the results of this study, AMP sought and gained licenses from the Federal Energy Regulatory Commission for three projects: Cannelton Locks and Dam, Smithland Locks and Dam, and Willow Island Locks and Dam. AMP has a co-license with its partner, the AMP member community of Hamilton, Ohio, for a fourth project at Captain Anthony Meldahl Locks and Dam.

All four projects currently under construction, discussed in more detail below, are expected to be completed in 2014 or 2015.

Cannelton

The 84-MW Cannelton project near Hawesville, Ky., was the first of the four projects to commence, with a groundbreaking on August 5, 2009. Cannelton is scheduled to be the first project finished, with completion aimed at spring of 2014.

Work at the site involves constructing an intake approach channel, a reinforced concrete powerhouse and a tailrace channel. The powerhouse will contain three horizontal 29.3-MW bulb-type turbines and generating units at a gross head of 25 feet. Voith Hydro is supplying the turbines and generators for Cannelton, as well as the three other run-of-river facilities, under a $420 million contract. The project is expected to provide an average gross annual output of about 458 GWh. A 1,000-foot-long 138-kV transmission line interconnection is planned to connect to the Midwest Independent Transmission System Operator (MISO).

Smithland

The 72-MW Smithland project near Smithland, Ky., will divert water from Smithland Locks and Dam through three horizontal 25.3-MW bulb turbines to generate an average gross annual output of about 379 GWh. The gross head of the project is 22 feet. The site will include an intake approach channel, a reinforced concrete powerhouse and a tailrace channel. A 2-mile-long 161-kV transmission line interconnection is planned to connect to MISO.

The $450 million Smithland project experienced some construction delays in May 2011 when continuous rains and backwater effect from the Mississippi River caused water to rise nearly to the crest of the cofferdam being installed to construct the powerhouse. Elevation at that part of the river had not reached such levels since 1937. The floodway structure in the cofferdam is used to channel the flow of the river to the dam and allow flooding to occur in a controlled manner. This helps prevent serious damage to the structure of the cofferdam during significant events.

Because of high water on the Ohio River, the Corps directed AMP to flood the cofferdam on May 2, 2011. Fortunately, little damage was caused to either the structure or the side walls, or slopes, Gerken says. However, the flooding caused construction work to fall behind by 40 to 50 days.

Despite the flooding, contractor CJ Mahan Construction finished excavation and construction of the cofferdam in October 2011. The Smithland project is expected to be completed in early 2015.