August 15, 2006

Kannagawa Hydropower Plant, Japan

Dr. Robert Peltier, PE

Tokyo Electric Power Co. (TEPCO)—the world's largest private power company—traces its roots to the illumination of a lecture hall by an electric arc lamp at Tokyo's Institute of Technology on March 25, 1878. That was more than four years before Thomas Alva Edison's Pearl Street Station began operation in New York City. Tokyo Electric Light Co., Japan's first electric power company, began commercial operation in 1887. TEPCO was born in 1951, when it became one of nine utilities created by the government's restructuring and consolidation of the country's electricity sector.

TEPCO also is an old hand at designing and building large pumped-storage projects; hydropower accounts for over 14% of the utility's installed capacity of 63,000 MW. In Japan, which has virtually no indigenous fossil-fuel resources, pumped-storage plants play an important role in stabilizing grids and in improving the efficiency and economics of hydropower generation.

By comparison, hydropower accounted for 8.7% of U.S. generation in 2004. America has about 19,000 MW of installed pumped-storage capacity, but the "real" total actually is a negative number: –5,500 MW. That's because it takes anywhere from 10% to 30% more power to fill a pumped-storage plant's reservoir than is recovered when its contents are emptied into hydro turbines. Although, on a net basis, pumped-storage plants consume more energy than they deliver, they serve a very useful purpose: the ability to respond very quickly to a load increase on a grid. Having a source of power that can be dispatched in minutes (seconds, if the turbines are already spinning) to trim peak demand well justifies its capital and operating costs. A pure-pumped storage plant also can be a source of "black start" power and provide the full range of ancillary services needed in today's competitive wholesale electricity markets.

Pure pumped storage

TEPCO's Kannagawa Hydropower Plant (KHP), which is now about half-finished, is a "pure" pumped-storage plant; that is, water is pumped from a lower reservoir to a higher one during off-peak hours and released when there is an immediate need for power. What Figure 1 doesn't quantify is that the water tunnel (the red dotted line) connecting the lower and upper reservoirs—created by the Minamiaiki Dam and Ueno Dam, respectively—is 3.8 miles long and spans two different prefectures. What it does illustrate are the number and size of the turbines envisioned—six, rated at 470 MW apiece (Figure 2). The power house in which the turbines "live" was built in a large cavern 708 ft long, 108 ft wide, and 169 ft high, at a depth of about 1,600 ft.

1. Major water works. At 2,820 MW, the Kannagawa Hydropower Plant will be the world's largest pure pumped-storage plant when all six of its units are completed—in 2016 at the earliest. Unit 1 entered commercial service in December 2005. Courtesy: Tokyo Electric Power Company Inc. All rights reserved.

2. Cave dwellers. The turbine floor is 1,600 feet below the surface, in a cavern hewn from rock. Courtesy: Tokyo Electric Power Company Inc. All rights reserved.

TEPCO has relied on decades of experience to execute a project whose technical challenges would have daunted a neophyte. Back in the 1960s, TEPCO cut its teeth on a series of smaller pumped-storage projects, topping out at 600 MW. The 1970s saw the development of larger facilities, including the 1,280-MW Shintakasegawa mixed-type hydro plant. The 1980s began with the commissioning of TEPCO's first pure pumped-storage plant—the 1,200-MW Tamahara project—in 1982 and ended with the successful completion of three other plants of the same type.

Kannagawa, which is TEPCO's ninth pumped-storage plant, bumps up against what may be the technological limits of building such facilities (details to be presented later). However, with an expected rated capacity of 2,820 MW, KHP's design represents the largest plant of its type in the world. The project recently bore its first fruit after more than a decade of cultivation. Unit 1 began test runs in December 2004, and it was declared commercial in December 2005. The next crop of kilowatt-hours is still years off, however; Unit 2 is scheduled to enter commercial service in 2010, and Units 3 through 6 won't be commissioned until 2016 or later.

Construction of KHP began in July 1993 with TEPCO's establishment of a field survey office for the project, two years ahead of its approval by Japan's Electric Power Development Coordination Council. Construction of the two dams powering KHP officially began in May 1997. By September 2004, both dams had been completed and the upper one had been filled to capacity, allowing testing to begin.