More than a pipe dream: How one city generates power when people run their taps
Hydroelectricity is a greener way to generate power than burning fossil fuels, but big hydro dams come with their own environmental problems. Those can include greenhouse gas emissions from flooded and rotting vegetation and the potential to kill fish.
But there are smaller-scale sources of hydro generation that can have a lower impact. In fact, one of them is right under our feet — namely, the pipes that make water flow when we turn on the tap.
Halifax is the first city in Canada to exploit in-pipe power. In a 2014 pilot project, it installed a turbine — basically a water pump that runs in reverse — in a single pipe in a Halifax suburb. Since then, the 31-kilowatt turbine has been generating roughly enough electricity annually to power 25 homes and selling that back to the grid for about $30,000 a year.
“The technology has, I would say, a lot of great potential,” said James Campbell, a spokesperson for Halifax Water. “On larger scales, that could really be quite significant.”
Campbell noted that there’s a lot of energy already in a municipal water distribution system: “It’s a constantly renewable resource that’s flowing anyway.”
The energy comes from the fact that water is under high pressure when it flows downhill from a water treatment plant. That pressure has to be reduced as it moves through the system, “or else it would just be blowing the taps into people’s homes,” Campbell said.
Typically, the system relies on pressure-reducing valves that use friction to release the extra energy as heat. Capturing the energy is a matter of running the water through a turbine instead. The turbine, which is made by U.S.-based Rentricity, has an estimated 40-year lifespan and has required little maintenance so far.
Frank Zammataro, CEO and co-founder of Rentricity, said the technology was originally designed following the 9/11 attacks as a way to generate emergency power using water towers in New York City. Rentricity has 15 installations so far, mostly in U.S. municipal drinking water systems, although it’s expanding into industries like agriculture.
Zammataro estimates about 75 per cent of municipal systems in North America have the right conditions for installation — sufficient flow and pressure generated by gravity when a water source is at a higher elevation (such as on a mountain or in a tower).
The challenge, Zammataro said, is that municipalities and especially industry want the system to pay for itself in a short period of time.
The in-pipe turbine in Halifax was funded by grants and a provincial program that allowed small electricity producers to sell power to the grid at guaranteed rates. At those rates, not taking into account the grants, Halifax Water’s $500,000 turbine would be paid off after 17 years in operation. However, the provincial “feed-in tariff” was cancelled in 2015, and no other in-pipe turbines have been installed.
Zammataro said the cost and efficiency can be optimized if water system upgrades and expansions are planned and designed with in-pipe turbines in mind. SOURCE