Calling a lake a battery sounds like something a utility’s marketing team dreamed up. But on a bluff above Lake Michigan near Ludington, Michigan, that’s pretty much what two utilities have been running for more than 50 years.<\/p>\n
The Ludington Pumped Storage Plant is basically a giant water elevator. When there’s spare power on the grid, six reversible pump-turbines push lake water up into an 840-acre reservoir, and when Michigan needs electricity in a hurry, that water runs back down through the same machines, which spin the other way and generate power.<\/p>\n
Consumers Energy<\/a> says the water drops 363 feet on its way back into the lake. Consumers owns 51% of the plant and DTE Electric owns the other 49%.<\/p>\n Michigan doesn’t have a monopoly on pumped storage, either. We recently looked at a Welsh mountain plant that’s swapping out its pump-turbines<\/a> while the rest of its units keep running.<\/p>\n But I’m not here to talk about turbines today. I’m here to talk about a fishing net.<\/p>\n Every spring, a barrier net goes into Lake Michigan in front of the plant, and every fall it comes back out. Pacific Netting Products, the company that supplies the netting, says it’s about 2.5 miles long with an average depth of 55 feet. The utilities’ relicensing paperwork gets a little more precise: roughly 12,850 feet, split into 62 separate panels.<\/p>\n Because a pump that big doesn’t really care what’s in the water. When Ludington is pumping, it’s pulling Lake Michigan into its intake, and for years that included a lot of fish. Earlier studies put the losses in the millions every year, according to the Mason County Press<\/em>.<\/p>\n According to the Great Lakes Fishery Trust<\/a>, the plant had been running for about 13 years before it became clear that operating it meant losing fish.<\/p>\n Close to a decade of legal fighting and negotiation followed, with the State of Michigan, federal agencies and tribal governments, including the Grand Traverse Band of Ottawa and Chippewa Indians, all involved. The settlement that came out of it requires the utilities to put a fish barrier net in every year, from April 15 through October 15 at a minimum, according to federal regulators’ environmental assessment<\/a>. It also set up the Trust to collect compensation for the fish the net can’t save.<\/p>\n The net itself is a bit older than that deal. The utilities’ filings say they’ve installed a seasonal net every year for more than 35 years.<\/p>\n I’ll admit a giant net is a pretty low-tech answer to a very high-tech problem. But it’s also one you can pull out, fix and put back, which frankly seems like a sensible trait for anything that spends half the year in one of the Great Lakes.<\/p>\n The panels are made of Dyneema, a super-strong polyethylene fiber you’ll also find in some climbing gear. The openings are half an inch near shore and three-quarters of an inch in deeper water.<\/p>\n Each panel is held in place by permanent anchor piles driven into the lakebed. According to the utilities, those piles usually sit about 100 feet from each other.<\/p>\n Then there’s the current. Water rushes toward the plant when it’s pumping and away from it when it’s generating, so the net gets shoved in both directions all season. Pacific Netting says it’s built to handle water moving at up to 3 feet per second, and that’s before you add Lake Michigan’s wind and waves on top. So the net takes a beating from spring to fall.<\/p>\n Which is why roughly a fifth of it gets replaced every year, according to the supplier. That sounds like a lot until you picture what the thing goes through all summer.<\/p>\n Pacific Netting also says Consumers keeps a backup net on site. I’d call that a pretty sensible precaution for something anchored in open water.<\/p>\n The other problem is gunk. A net sitting in the Great Lakes for months turns into a pretty attractive home for algae and zebra mussels, and you’d expect a clogged mesh to catch a lot more of that current.<\/p>\nSo why does a power plant need a fishing net?<\/h2>\n
The net has a pretty rough summer<\/h2>\n
Divers spend the summer pressure-washing it<\/h2>\n