Clean Energy Canada | Power in the Pipe: Inside a British Columbia Run-of-River Hydro Plant
June 18, 2014
Earlier this month, Innergex Renewable Energy invited the Clean Energy Canada team to tour its Ashlu Creek Hydro Project—a run-of-river renewable-energy plant about 35 kilometres northeast of Squamish, British Columbia.
Unlike large hydroelectric dams, run-of-river plants do not require a vast reservoir. Instead, they “borrow” a carefully controlled portion of a river’s flow and direct it through a pipe called the penstock to a powerhouse downstream. There, the water spins turbines to generate electricity before it is returned to the river. Plants such as the Ashlu are designed to ensure that the watercourse always retains a minimum flow, to support any resident fish and other wildlife. (In reality, as discussed below, they do not always do so.)
The Ashlu plant is one of 13 such plants that Innergex operates in British Columbia. In total, approximately 50 run-of-river facilities are up and running in the province. When operating at peak capacity—as it was the day we visited—the Ashlu plant’s three Austrian-made Andritz turbines spin just shy of 50 MW of clean electrons out onto the provincial power grid.
Here’s a quick clip of one them in action:
Upstream at the head pond, an automated valve ensures that the Ashlu plant always directs a minimum of cubic meters per second of water in the river:
The Ashlu Creek plant includes an innovative Energy Dissipation System—a series of six valves in the powerhouse (see image above) designed to eliminate the potential impacts on downstream fish habitat that can occur when the power utility suddenly decides it cannot accept the plant’s power. Such an event would require the turbines to shut down, which would ordinarily hold back water in the penstock above and prevent it from re-entering the river. This practice, known as “ramping,” can kill fish by stranding them in shallows when the water level suddenly drops.
The Energy Dissipation System prevents that from happening.
“It’s a system of valves that allow you to continue to put water through the powerhouse, but remove the turbine from the equation,” says Matt Kennedy, VP of Environment for the company’s western region.
However, in an often-cited 2010 incident that occurred during the plant’s commissioning, just over 87 fish fry perished downstream from the Ashlu Creek plant when the utility suddenly stopped accepting power, and the plant’s Energy Dissipation System did not kick in as expected.
“It was an isolated accident, and it has never happened again since,” says Kennedy. Operators later traced the incident to a programming oversight in the software that controls the plant.
A part of the Ashlu Creek project, Innergex constructed 58,582 square meters of fish spawning habitat just downstream of the powerhouse. Each fall, thousands of salmon spawn in the pools and ponds.
The company also took steps as required to ensure trout could continue moving upstream, past the weir that manages the headpond. This fish ladder is covered with mesh to prevent fish from jumping out, and to prevent birds from picking them off on their way up.
Ecological standards for run-of-river power plants have proven a contentious issue in recent years in British Columbia. Earlier this year, the Pacific Salmon Foundation released an independent review of potential impacts of British Columbia run-of-river power hydroprojects on salmonids. The review identified pathways that would lead to fish impacts, and said that most of the province’s run-of-river hydro plants operate on fish-bearing rivers, but that ultimately the evidence of impacts was “inconclusive.”
This is because many of the early facilities were not monitored and because the more recent, but well-monitored sites are in the midst of their environmental assessments, the report authors said.
In its commentary on the report, the foundation said that a lack of independent review and analysis of the province’s run-of-river power plants amounts to a “serious deficiency in environmental oversight.”
Clearly, run-of-river plants need to be carefully sited and responsibly operated. The industry needs oversight, and needs to continue to identify the best opportunities for developing projects while minimizing ecosystem impacts.
However, with those boxes checked, run-of-river power can be a very low-impact solution—especially when compared to the fish and wildlife impacts of many fossil-based energy sources. As just one example, last year 7,500 migrating songbirds died when they flew into a flare at a liquefied natural gas plant in New Brunswick.
For its part, the Ashlu Creek Hydro Project delivers enough power each year to light up approximately 25,000 British Columbia homes—without releasing so much as a puff of greenhouse-gas emissions along the way. It is a case study in how to “do it right,” from a company that is clearly aiming for the highest possible standard of stewardship over both ecosystems and the climate.