Power plants don’t normally make my vacation sightseeing list, but this was no ordinary power plant.
It has neither the smokestacks and plumes of a coal-burner nor the telltale cooling towers of a nuclear facility. Its 1,000-acre footprint almost disappears into the tall dunes of Lake Michigan’s eastern shoreline.
Slightly more visible are the 50-plus white wind turbines arrayed across the rolling orchard country that lies to plant’s inland side. But you can walk around the place on a breezy day in June and hear little but the wind itself.
Underground and out of sight, billions of gallons of lake water are moving uphill or down through a set of six huge, reversible hydroelectric turbines. As they turn, enough electricity is being stored or released, depending on the time of day, to power 1.4 million households in a cycle that optimizes the balance between power generation and consumption.
A brand-new solution to the world’s electric power problems?
Not at all. Construction of the Ludington Pumped Storage Plant began in Richard Nixon’s first term and was completed early in his second, in 1973.
Old idea, new purpose
At that time its purpose was to serve as a giant storage battery for volts created in distant coal and nuclear plants during nighttime hours, when demand was low, returning them to the grid during daytime periods of peak demand.
That purpose continues, but is expanding in the new age of renewables.
Now it can be used to store and dispatch electricity generated from wind, which blows intermittently all day long but often reaches its peak potential overnight.
Sometimes known as the Pentwater plant, for the western Michigan village south of Ludington where it is situated, the project was the world’s largest of its kind when built by Michigan’s two largest utilities, Consumers Energy and Detroit Edison.
It remains No. 5 in the world according to a page on pumped hydroelectric storage maintained at Wikipedia, and still boasts some impressive stats:
- Its kidney-shaped storage reservoir measures about 2.5 miles long, a mile across and 110 feet deep, with a surface area of 840 acres and a surface elevation some 360 feet above the great lake’s normal high-water line.
- Its six huge tubes, or “penstocks,” that carry water from the lake into the reservoir and back down, are a quarter-mile long and 28 feet in diameter at the upper end, tapering to 24 at the bottom — you could drive a gasoline tanker through them.
- A turbine at the bottom end of each penstock is rated at 433,000 horsepower and is capable of moving more than 5,000 gallons per minute; working together, they can drop the reservoir level by six feet a minute when returning power to the grid at maximum output.
- The plant’s overall output is rated at 1,875 megawatts, which is slightly more than the combined capacity of Xcel Energy’s nuclear plants at Prairie Island and Monticello.
And yet the plant remains somehow unobtrusive, surprisingly harmonious with its surroundings.
Mystery presence on map
I first noticed it on a map or satellite image — not through the car window — as Sallie and I were navigating around the Ludington area some summers ago: a long, thin line in the lake that looked sort of like a breakwater but had no apparent opening to the lake, nor any visible development on the shoreline. Huh?
A year later, coming into Ludington at dawn on the cross-lake ferry S.S. Badger, I noted a spot in the horizon some miles to the south where the dunes seemed unusually high, geometric and manicured.
But we had miles to go, so I made a mental note to investigate next time I found myself in the territory with an extra hour or two at hand. Time passed, and our allegiance shifted to the competing ferry Lake Express out of frustration with the Badger‘s truculent approach to environmental regulation.
Some spare time arrived on Monday, when stiff winds and cool temperatures made the Ludington beaches a better bet for wet-suited surfers than our swimsuited selves. So we found our way to a little parking lot provided for visitors by Consumers Energy, which operates the plant for the two-utility partnership.
This took a little doing; for all of its size, and the five years of earth-moving required to raise its massive retaining dike, the project often disappears from roadside view, screened out by lush forest.
We made the short, steep hike to an observation platform and learned that the long line in the water isn’t part of the plant proper, but rather a 2.5-mile exclosure net to keep fish out of the turbines during warm-weather months.
Thereby hangs a tale told in somewhat less detail than others in Consumer Energy’s discussion of the project and its engineering feats — the turbines also proved highly effective at killing fish, which prompted lawsuits from conservation groups and Indian tribes.
The nets went up in 1989 and the litigation was settled in 1996, with the utilities paying into a Great Lakes Fishery Trust Fund that finances a range of projects to offset the plant’s negative impacts on fish.
On the plus side, environmentally speaking, Consumers Energy has also undertaken some habitat-improvement work for bird populations; this work has earned high marks from the national Wildlife Habitat Council.
Bringing renewables online
Until recently, the Pentwater project added no new power of its own to the Michigan grid. Its virtue lay in allowing large coal and nuclear plants to run at a continuous high output, maximizing their efficiency.
Not incidentally, it has also enabled the utilities to meet maximum demand without building new “peaking” plants — typically fueled with natural gas — whose output can be raised and lowered more readily than the baseload plants.
According to the trade publication Water Power & Dam Construction, the Pentwater plant currently achieves just 70 percent efficiency over its cycle of storing and releasing electricity.
But that was good enough for the utilities — and their state regulators — to justify a $315 million capital investment back in 1969, an outlay that would be a bit over two billion bucks in today’s dollars.
In the last year, Consumers Energy has brought an additional 100 megawatts of wind power into the plant from an array of 56 turbines in the vicinity and potentially could add more, if required to do so under the state’s renewables standard.
And this simple, elegant approach to balancing generation against load has stood the test of time at Pentwater, as it has all around the globe.
Large pumped-storage facilities like Pentwater have been in use since the 1930s and, according to The Economist, remain today as the most widely used form of bulk electricity storage worldwide — even as companies experiment with banking voltage in such forms as compressed air and superheated salt.
That’s why Consumers Energy and Detroit Edison are now in the midst of a six-year project to replace the Pentwater plant’s turbines with new, higher-efficiency equipment from Toshiba, an $800 million upgrade that will raise the plant’s capacity by 15 percent, to 2,172 megawatts or 1.65 million households, and its efficiency by 5 percent, all within its existing footprint.
And you might still pass by the plant without even knowing it’s there.
