Arkansas Electric Cooperative Corp. (AECC) applied Jan 3 to FERC for a preliminary permit allowing it up to three years to explore the feasibility of the 600-MW (nominal) River Mountain Pumped Storage Hydropower Project in Arkansas.
The project will utilize the existing U.S. Army Corps of Engineers’ Lake Dardanelle on the Arkansas River as the lower reservoir. The project intake structure will be located on the Arkansas River at approximately navigation mile 217.4, which is upstream of the existing Dardanelle Lock and Dam structure located at navigation mile 205.5.
AECC said it filed this preliminary permit application to update the initial evaluations of the project that were performed in the 1990-1993 period by other entities. AECC was approached to participate in the project in 1994 by the then license holder but was unable to do so at that time.
AECC noted that it has considerable experience with hydropower on the Arkansas River. In 1983, AECC received seven FERC licenses for projects on the Arkansas River. Three of those projects, at Dam No. 2, Lock and Dam No. 9, and Lock and Dam No. 13, were constructed by AECC from 1988 to 2000. These three construction projects represented an investment by AECC of approximately $349 million. The licenses for the remaining four projects, at Lock and Dam Nos. 3-6, were surrendered by AECC in the 1980s because further analysis showed them to be economically marginal or uneconomic to develop at the time.
The application added: "After a period of adding significant natural gas combined cycle capacity, which ended in 2012, AECC is now studying its options for future generation resources, including a program of renewable energy development for the next 20 to 25 years. That includes a new examination of potential hydroelectric projects at Dams 3, 5 and 6 for which AECC currently holds preliminary permits (P-14663, P-14665, and P-14664, respectively). AECC is currently updating previous energy estimates on those projects as part of the preliminary permit process.
"Regarding the River Mountain Project, which is the subject of this application, AECC is now in a position to seriously study the proposed Project and the possible benefits this pumped storage facility could add to AECC’s generating resources. Prior to this date, however, a preliminary permit application to undertake those studies has not been filed with FERC by AECC for the Project. Specifically, another entity currently holds a preliminary permit (FERC P- 14472 issued January 17, 2014) for the site and until that preliminary permit expires on December 31, 2016, AECC cannot apply for a permit which would secure priority of the site for evaluation. Now that such permit has expired, AECC hereby submits this application for consideration of being granted a 36-month preliminary permit.
"If AECC’s application is approved, AECC will use the Burns & McDonnell Engineering Company, Inc. … to assist AECC in studying the Project. This firm has over 50 years of experience developing very large civil as well as major power generation Projects, both domestically and internationally. Their experience includes major projects in several countries outside the US. They have been retained previously by AECC on several of AECC’s power generating facilities for design, contracting, and construction management support, including AECC’s first power plant, the Thomas B. Fitzhugh Generating Station commissioned in 1962 which is located on the Dardanelle pool of the Arkansas River approximately 30 miles upstream of River Mountain."
Project would include three pump-turbine/motor-generator units
The proposed River Mountain Pumped Storage Project is a 600-MW (nominal) facility to be located in Logan County, Arkansas, approximately thirteen miles from Russellville, Arkansas. A new reservoir, to be constructed on River Mountain overlooking Lake Dardanelle, will serve as the upper storage reservoir, with a surface area of approximately 208 acres when full. Underground power facilities will contain three pump-turbine/motor-generator units, each with an installed generating capacity of 200 MW. The upper and lower reservoir will be connected by a power tunnel, power shaft, penstocks, and draft tubes. The units will require approximately 220 MW of capacity to operate in pumping mode.
The primary mode of operation of the project is expected to be as an energy storage and peaking facility storing off-peak energy during nights and weekends by pumping water from the lower to the upper reservoir, and generating energy to meet peak system demands by returning the water to the lower reservoir through the turbine-generators located in the power plant.
The generating capacity of the project will vary with the head difference between the upper and lower storage reservoirs. The elevation difference between Lake Dardanelle (at normal pool) and the upper reservoir atop River Mountain (at maximum, full capacity) is approximately 670 feet. On average, the project will be able to generate approximately 6,500 MWh in the time it takes to lower the upper reservoir to its minimum, which will take about 9.5 hours. It will take approximately 13 hours to refill (recharge) the upper reservoir which will require an average of 660 MW of pumping capacity. The maximum anticipated generating capacity factor, assuming operating at full daily generation five days per week and two days (weekends) on standby, would be approximately 28%. However, based on plant utilization factors of other pumped storage facilities, a generating capacity factor of 10% to 20% is more likely. The units would be available to serve as spinning reserve for most of the generating period.
Power generated will be transformed to 500 kV and interconnected with the existing grid via a new 500-kV overhead transmission line at a point where existing 500-kV power lines owned by Entergy Arkansas pass within two miles from the project. A switchyard will be constructed near the portal of the access tunnel to connect cables from the power plant to the 500-kV overhead transmission line. A second switchyard will be constructed at the point of interconnection between the new 500-kV transmission line and the existing Entergy power lines.
Notable is that in January 2014, FERC issued a preliminary permit, good for three years, to Control Technology Inc. for a 600-MW pumped storage hydro project at this site. That is the now-expired permit that AECC referred to in its application.