Going with the flow

Halifax Water is making clean, efficient energy from moving water… and that’s not all.

Cogswell ATDES Map. Image courtesy of Halifax Water.

Could the water flowing from your tap also power the creation of electricity? In a word, yes.

For the past ten years, Halifax Water has been doing just that by creating clean, renewable energy via an in-line turbine added to its water system infrastructure.

Halifax’s gravity-fed water distribution system, flowing from the heights of Pockwock Lake down to the Halifax peninsula, serves a geographical area filled with hills and valleys. To regulate water pressure, engineers have designed pressure reducing valves (PRVs) so that people living at the bottom of a hill aren’t drinking from a fire hose, while those at the top of a hill only get a trickle out of their taps. These PRVs release the excess pressure from downstream flows in the form of sound and heat within the valve and pipe work (think whistling tea kettle).

This excess pressure doesn’t have to be wasted, though. By replacing a traditional PRV with an in-line turbine, pressure can be converted into electricity, says Jeff Knapp, Senior Manager of Energy and Business Development at Halifax Water.

“The flow of water over the turbines’ runner blades results in energy being absorbed and transferred to the output shaft of the turbine, and typically to a generator which can convert this mechanical energy into electricity.”

Other parts of Canada and the U.S. have already installed in-line turbines in their water systems similar to the one at Halifax Water’s Orchard Street site in Bedford.

“It was installed in 2014 and has been operating flawlessly since that time,” says Knapp.

The cost of the Orchard Turbine was approximately $500,000, with funding provided by Halifax Water, the Water Research Foundation, and the Nova Scotia Department of Environment and Climate Change. Knapp says it’s expected to save well over 4,000,000 kWh of energy over the life of the 20-year power purchase agreement Halifax Water has with Nova Scotia Power.

Knapp is proud of other work Halifax Water has done to maximize energy efficiency at its administrative offices and its water and wastewater treatment facilities (WWTFs).

“We installed air source heat recovery at our largest WWTFs between 2014 and 2016 — those projects were very successful, resulting in almost a 50 per cent reduction in fossil fuel use and heating costs during the heating season,” he says.

There’s also untapped potential in wastewater. That water coming from our dishwashers, washing machines, showers, and bathtubs is still warm when it reaches the plant and as such can be used for localized heating. 

“We are exploring wastewater heat recovery at some of our treatment facilities, and the possibility of utilizing the waste heat to help heat the facilities in the winter months,” Knapp says.

Wastewater heat recovery makes sense in new developments, too, like some already underway in downtown Halifax.  

“The Cogswell District Energy System is currently under construction. The Distribution Piping System has been fully installed and the energy centre, which will be located at the Halifax treatment facility, is currently being designed. The system is expected to be operational by late 2028,” Knapp says.

Once completed, the six buildings forecast to be built as part of the Cogswell project will be the recipients of energy from wastewater (in the form of heat recovery) coming into the treatment facility during the colder months. There’s also potential to expand the wastewater heating zone into the Gottingen-Cogswell-Brunswick Street nexus ­— an area slated for redevelopment and where Halifax Water already has installed pipe.

As plans for wastewater heat recovery move ahead, what’s happening with the solid residue being pulled from that wastewater? Halifax’s biosolids facility, located at Aerotech Business Park, is due for an upgrade soon, which could include anaerobic digestion to generate renewable natural gas, a process that’s been used in Sweden for decades. If funding is secured and the project goes ahead, Knapp says Halifax Water could both be buying its own gas for use in its plants and selling biogas to the local market. It’s a win-win-win for the utility, the province, and the environment.

With debate swirling about Nova Scotia’s energy future and the need for increased resource extraction to supply power, it’s clear that we need to get better at wasting less of the energy we already produce.

Investing in well-established technologies like in-line turbines and wastewater heat recovery is an important step towards our energy sovereignty.

Climate Stories Atlantic is an initiative of Climate Focus, a non-profit organization dedicated to covering stories about community-driven climate solutions.