Research teams are looking for turbines that make tidal power work without harming sea life, like this one. (Photo courtesy of Charles Cooper with Oceana Energy)
For decades, people in the Pacific Northwest have relied on hydropower
for most of their electricity. But dams hurt salmon runs and river
ecosystems. That’s sent Washington utilities on a quest for new, cleaner
sources of power. As Ann Dornfeld reports, some are looking for new ways
to harness the power of flowing water:
Transcript
For decades, people in the Pacific Northwest have relied on hydropower
for most of their electricity. But dams hurt salmon runs and river
ecosystems. That’s sent Washington utilities on a quest for new, cleaner
sources of power. As Ann Dornfeld reports, some are looking for new ways
to harness the power of flowing water:
It’s a brilliant day outside. Craig Collar is perched on a rocky outcropping
overlooking rushing green water swirling and eddying below. Collar says
the water is moving so quickly because this is one of only two spots where
the Pacific Ocean flows into Puget Sound:
“As the tide comes in, it comes into this constrained passageway at
Deception Pass. Y’know, all that energy gets channeled, focused
through this very narrow area. So that’s what results in these rapid
tidal currents that we’re seeing right here.”
Collar researches new power sources for Snohomish County Public Utility
District. His goal is to use a sort of underwater windmill to convert some of
this water’s energy to electricity and funnel it onto the power grid. It’s called
“tidal power.”
Collar says there are dozens of underwater turbine designs to choose
from. Some look like a standard wind turbine with three big blades; others
look like a metal donut or a fish tail.
The Utility District is considering putting underwater turbine farms at half a
dozen locations around Puget Sound. It estimates tidal energy could power
at least 60,000 homes. Collar says the technology has a lot going for
it. It doesn’t emit carbon dioxide or other pollutants. He says underwater
turbines can be much smaller than wind turbines because they’re so
efficient:
“And that’s just as a result of the higher density of water. Water’s
roughly 800 times denser than air, so it contains a lot more energy.”
Unlike the wind, tides aren’t really affected by the season. You know the
saying: “predictable as the tides.” Collar says lunar phases let you forecast
the tides for decades into the future:
“Where with wind, you’re doing good if you can forecast hours or
even a little bit ahead. That really helps utilities like us integrate that
power into the power grid.”
Collar acknowledges there are a lot of questions about the impact of tidal
turbines on marine ecology.
These questions worry nearby Native American tribes. The Tulalip
reservation is close to Deception Pass, and they fish throughout Puget
Sound. Darryl Williams is the tribes’ environmental liaison:
“Five species of salmon, orca, grey whales, eagles, hawks, falcons…
y’know, we have numerous species of fish and marine mammals and
migratory birds that use the areas that are being proposed for these
turbines, and the studies really haven’t been done yet to show what
the impacts may or may not be.”
Along with the marine environment, Williams says the tribes are worried
that tidal turbines could scare away fish or get tangled in fishing nets.
“For the tribes, the fisheries aren’t only an economic source but
they’re also part of the tribes’ culture. Most of our cultural activities
are centered around salmon, and if we can’t catch the salmon, then
that part of our culture really goes away.”
A research team at the University of Washington is looking for ways to
make tidal power work without harming sea life. Brian Polagye is a
mechanical engineering graduate student whose focus is renewable
energy. His team is working with the oceanography department to look at
the ecological risks of tidal power. But Polagye says there are a lot of
misconceptions about what those risks are.
“The most obvious one is the question of ‘Oh! So you’re going to put
these rotors in the water and you’re gonna make sushi in addition to
electrical power.’ People view these turbines kind of as almost a
propeller that’s moving through the water so rapidly that if anything
gets near it it’s gonna get chopped to pieces. In practice, you can’t
actually run the rotors that fast. The maximum speed that the tip of
the rotor can turn at is about 25 miles an hour. Which is actually
relatively slow.”
Polagye says one of the biggest risks is that removing some of the energy
from the tidal currents will change the ecology downstream. He’s studying
how much power can be extracted from an estuary before it has a
noticeable effect on the ecosystem.
Back at Deception Pass, Craig Collar with the utility district says even if
there is a small ecological impact, it’s key to look at the overall picture:
“At the end of the day the thing that’s compelling about tidal energy
for us is there just aren’t very many opportunities for clean,
renewable, emission-free energy that’s both predictable and close to
the loads. And all those things are true for tidal energy in the Puget
Sound region, and there simply is no other renewable for which all
those things are true.”
The utility is working with the University of Washington to figure out
whether tidal power is viable in Puget Sound. If so, it could help reinvent
hydropower on the Pacific Coast for the next generation.
For the Environment Report, I’m Ann Dornfeld.