SALT LAKE CITY — There is wasted energy under the streets of Salt Lake City. Lots of it. And for decades, it's been deliberately dissipated. But now, city planners are taking steps to harness the energy and put it to good use.
In what is city officials say is the first project of its kind in Utah, the Salt Lake City Public Utilities Department plans to install microturbines to generate electricity from rushing water inside municipal water pipes.
"Yes, we can do this project," Public Utilities Director Jeff Niermeyer said, explaining that the electricity will be sold to Rocky Mountain Power. "It will pencil out."
Because of its topography, Salt Lake City is especially well-suited to an idea that has been around for decades, planners said. Water running downhill packs a punch and carries potential energy as it descends from higher elevations.
When water is stored behind a dam, it's capable of generating large amounts of electricity by falling through big pipes called penstocks and spinning enormous hydroelectric turbines.
"Our water has been falling down the foothills in this pipe and has developed a lot of potential energy," Niermeyer said as he pointed to a concrete blockhouse at the intersection of 500 South and 1000 East
At that point, a buried pipeline drops sharply as it descends the steep terrain on the city's east side.
When the door to the blockhouse is opened, the sound of rushing water is almost deafening.
"Rushing water being squeezed through some plates," Niermeyer explained.
The plates are inside two large valves, pressure-reducing valves, that are more than a half-century old. They're actually designed to squeeze the energy out of the falling water and dissipate it to reduce pressure.
"We have to keep the pressure reasonable in our system so we don't end up blowing up pipelines and creating flooding and issues like that," Niermeyer said.
That means potential hydroelectricity is being wasted at 57 locations in the city where water runs downhill and where the city has pressure-reducing valves.
"Each of those, to some degree, offers an opportunity to produce power at those locations," Niermeyer said.
I think we can generate … 190-kilowatt hours, which is really equivalent to enough power to produce power for 92 homes.
–Public Utilities Director Jeff Niermeyer
Rocky Mountain Power spokesman David Eskelsen said the company is not aware of any utility in the state that has tried to generate hydroelectric power inside water pipes. Such projects are underway in two cities in Oregon.
Salt Lake City expects to build its first facility later this year at the 1000 East location. Water in a 36-inch pipe will flow through two microturbines that will spin at high speed to generate electricity.
"I think we can generate … 190-kilowatt hours," Niermeyer said, "which is really equivalent to enough power to produce power for 92 homes."
The project on 1000 East will cost nearly $1 million. But most of that money would have been spent anyway to update the aging pressure-reduction valves.
That facility is strategically positioned close to power lines, which means the city can efficiently sell the electricity to Rocky Mountain Power. The other 56 locations may not work out financially unless Rocky Mountain Power modifies its rate structure, which is not especially favorable to small, alternative energy projects.
In a pricing structure that is analogous to retail vs. wholesale prices, Rocky Mountain Power buys electricity from small producers at a lower rate than what its customers have to pay when they buy electricity from Rocky Mountain Power.
The company's rates, approved by the Utah Public Service Commission, are based on the theory that the cost of power lines and distribution facilities have to be factored into its retail sales price.
Niermeyer hopes there will eventually be more flexibility in the rate structure once the first microturbine project proves itself.
"What we're hoping is that this demonstrates our ability to do what's called 'virtual net metering,' where you produce it at one location and get credit for it at another location," he said. "And that will open up a whole bunch more other projects.
"I think there's a real consensus now in progressive communities like Salt Lake," Niermeyer said, "that we really need to look at how we can produce energy sustainably and reduce our overall impact on the environment."