Twenty years ago, the state shut down eastern Oregon farmer Kent Madison’s water well to protect overdrawn groundwater below.
He was left with a 700-foot well and a pump that he owned but couldn’t use.
It was 10 years before he found a way to legally refill the underground aquifer with water he could use on his farm. New laws and permitting processes allowed Madison to inject winter flood water from nearby Butter Creek into the aquifer below so he could use it later for summertime irrigation.
This aquifer storage and recovery process is now used in numerous locations across the Northwest to store water while it’s abundant and save it for drier days. According to the Oregon Water Resources Department, the concept offers many benefits including a hedge against climate change and population growth.
But Madison discovered another benefit: You can use it to generate power.
He noticed that when he recharged the aquifer under his well, he was sending the water down a 620-foot drop.
“If I were sitting at the base of a dam that was 620 feet high, I’d try to capture some energy off of it,” he said. “So, I started thinking, ‘How do I capture energy off that water 600 feet below the ground’s surface?’”
He devised a way to do it by applying wind-energy technology to the water pumping system.
Here’s how it works: The water pump itself has a mechanism that keeps the pumping bowl from spinning backwards when it’s not moving water upwards. When water flows down through the pump, the bowl spins backwards, but not fast enough to generate energy on its own. By attaching a regenerative drive to the system, Madison created an electronic brake that generates heat as the pump bowl spins.
“That’s energy,” Madison said. “You take a slow-spinning turbine, apply a brake to it, and it creates more energy than it takes to apply the brake.”
With a grant from Oregon Energy Trust, Madison developed a successful prototype that now recovers 47 percent of the energy it takes for him deliver the water to the pump site. By applying ready-made technology, Madison said, “it was incredibly easy to do.”
Is it easy enough for an entire city to do, too? City of Pendleton Public Works Director Bob Patterson loved Madison’s idea.
Pendleton has been recharging its aquifer with water from the Umatilla River since 2004, and is now trying to put Madison’s method to work on a larger scale.
Though the end result – even with similar generators in five wells – is still pretty small-scale in the world of power production.
“We’re calling ourselves pico-hydro,” Patterson said. “Micro-hydro projects are usually about 5 megawatts. We’re looking at projects between 25 and 125 kilowatts.”
Nonetheless, if everything goes as planned, the city’s $500,000 investment in the technology – $80,000 will be offset by clean energy subsidies – should be repaid within six or seven years.
According to the city’s calculations, the five wells together will generate 1 million to 1.2 million kilowatt hours of electricity over the duration of the recharging season. That should add up to $62,000-$72,000 in annual savings.
“We’re really thinking of it as an offset for our overall power bill,” said Patterson. “We pay $400,000 a year for a water supply system to lift water out of the wells and run our water treatment plant.”
Meanwhile, the recharging effort is slowly reversing annual declines in the city’s aquifer. The aquifer level was dropping 3.5 feet a year as groundwater was removed for city residents and rural farmers. The level should increase by 1 foot a year over time as the city injects more water into the aquifer than it removes and relies more on surface water from the Umatilla River.
Pendleton is ahead of the pack when it comes to developing municipal hydropower projects, said Jed Jorgensen, senior project manager for Energy Trust. The city of Portland signed a deal in October to add in-pipe hydropower to its municipal water mains. But that’s another rare case.
“In general, these municipal hydro projects are still very few and far between,” he said. “For the most part it’s because they require a tremendous amount of permitting for a small amount of energy.”
Pendleton is still working through the Federal Energy Regulatory Commission’s requirements for adding hydropower to its water wells. Next month, the city will submit its final application, which will go out for public comment before FERC makes a decision.
Patterson said he’s hoping all the permits will be in-hand by March so the city can test the system and start generating power when it recharges the aquifer next winter.
*This story was informed by OPB’s Public Insight Network.