Reducing harm to wildlife or applying a wildlife
impact criterion to assess harm and inform policy, is a worthwhile goal. Impact
on biological species is a subset of environmental impact. Many human engineering
and energy endeavors impact wildlife. Wind turbines kill migrating birds and raptors.
Boats, underground blasts, and seismic air guns impact ocean life. Dams impact
wildlife. Mining and oil & gas development can fragment forests, impacting species
and habitats. Light pollution in urban areas impacts wildlife.
I read about
painting wind turbines black or with black stripes as a deterrent to birds that
will prevent many deaths. I am not sure if this is being adopted (perhaps
another post). The subject for this post is the development of fish-safe
hydropower turbines. Harmful impacts of hydroelectric turbines on fish have long
been known and there have long been strategies to lower impact.
Hydropower is
still by far the leading source of renewable electricity, producing more power
than all other renewables combined in 2022, according to a July 2024 MIT Technology
Review article. Hydropower is expected to have small growth or remain flat in many
countries where it is nearly fully developed but in less-developed countries, there will be more hydropower plants built.
Most dams were
built many decades ago. According to the IEA, the average age of a hydropower
plant in the U.S. is 65 years. Some are much older. When these were built, much
less was known about environmental impacts and effects on fish. The fact is that many fish and other aquatic creatures are killed by hydropower turbines through
direct hits or water pressure changes near dams with larger drops. As early as
1890, there were regulations on dams requiring infrastructure to allow fish to
pass through. As well as harming fish through turbine strikes the dams prevent
migrating fish from migrating and fragment their habitats. Fish can migrate
upstream and downstream, and both are affected. Many of these hydro plants are
coming up on their 50-year relicensing requirements which may include improving
fish/wildlife safety. Hydropower relicensing, it has been argued in the past, has
become cumbersome, expensive, and slow. While I agree it should be streamlined,
there should be more focus on modernizing the old plants, and that could
include making them safer for fish. The issue is not unlike requiring pollution
abatement at coal-fired power plants. Perhaps a fish death abatement credit
trading system could be developed similar to pollution credits. Of course, I don’t
know the feasibility or plausibility of that. Around 17GW of hydropower
facilities will be up for relicensing by 2035.
Fig. 7. Histogram showing the year in which a license will expire from a sample of 1038 FERC licensed hydropower projects across the United States.
Development of Guidance Systems to Allow Fish to Safely
Bypass the Turbine Zone
The EU project “FIThydro”, involved
the research and industry partners studying the ecological impact of hydroelectric
plants. Based on that research ETH Zurich’s Laboratory of Hydraulics, Hydrology
and Glaciology (VAW) developed a protection and guidance system to migratory
fish to safely bypass hydropower turbines. A model of that system is shown
below.
Fish migrate both downstream and upstream. Strategies
like lift gates, basically elevators, are used to convey fish upstream. As the
picture shows the fish are moving upstream. Those fish can’t pass through the
turbine chamber so they must be accommodated with some type of conveyance
system. Regarding downstream conveyance, the researchers noted:
“When descending over weirs, they can also be injured
by the strong currents in the stilling basin or lose their orientation, making
them easy prey for predators.”
Predators include birds, which predate lots of
juvenile fish at dams. Predation of disoriented juveniles may represent the largest
number of fish kills at dams. Down the road from me here in Ohio there is a long-abandoned
water mill in a very small river where the water level drops about 3 feet maybe,
and I often see a grey heron there fishing the low side. The FITHydro
researchers studied how different species of fish and eels pass along the
guidance system. Based on that research they developed their curved-bar rack
bypass system (CBR-BS), which is shown above.
“The core of the CBR-BS is a vertical bar rack with
specially shaped bars; these create strong local eddies that steer fish away
from the bar rack and towards a bypass. In this way, the CBR-BS is able to
guide a variety of fish species of different sizes safely past the turbine. The
bypass system is also designed so that the plant's operations are only slightly
affected.”
The researchers
created a barotrauma detection system to detect and monitor dangerous changes
in water pressure. It utilized sensors that are sent through or over the dams and
retrieved. They also developed a bedload monitoring system (BMS) which enables qualitative
and quantitative assessment of bedload transport in watercourses. This is a
passive acoustic system that utilizes geophones and accelerometers.
Solutions for
protecting fish include fish ladders/spillways, installing screens, or lowering
turbine blade speed. Fish ladders and other spillways have to divert some of
the water so less can be used to power the turbine. They are like fish weirs
that gather the fish. Screens can be very expensive to install and maintain, and
lowering turbine speed can make power generation uneconomical. Thus, finding a
means to allow fish to pass through the turbine chamber unharmed is a desirable
problem to solve.
Another
strategy is to lower turbine speeds and runtime during fish migration seasons. Some
dams shut down at night to allow eels to pass through. Changing operating
parameters like this is always an option but also is weighed against economics.
Trap and Haul is another strategy used more in the past. That is to use weirs
to collect and trap the fish and transfer them to specialized tankers or barges
that release the fish on the other side.
Fish Ladders and Spillways
Fish ladders
are a type of spillway that allows fish to pass around dams, avoiding the turbine.
There are several kinds of them. Some use siphoning to guide the fish. Others
use compressed air to guide them. Many use step downs to account for drop. There
are quite a few designs. They have been around for centuries. They are often
used for fish that swim upstream to spawn like salmon and trout. They can allow
many species through at high rates, but other species can have much lower rates
of passage. Dams commonly install screens to keep larger fish away from the
danger zone near the turbines. “Leaves and debris can block these screens
and reduce flow without constant maintenance. They also add about $1,000/kW in
capital costs.”
An informative
video from Practical Engineering, How Fish Survive Hydro Turbines, shows how
fish passage is managed at McNary Dam on the Columbia River which hosts a 1GW
hydro plant. Splashing water is used to attract fish
toward safe passage. Baffles, weirs, lift gates, screens, brushes to clean the
screens, and step-down sections in the guidance systems help safe passage. An
upstream guidance system also assists upstream migration. McNary Dam has ways
to speed and slow the water currents and guide the fish in such a way as they
get less disoriented and are less amenable to predatory birds. At McNary the small
percentage of fish that pass through the turbine chamber are more endangered by
changing water pressure than turbine strikes. This affects the swim bladders of
fish that they use for buoyancy. The video also shows some interesting ways
fish passage is studied in the lab and onsite at dams.
New Turbine Designs That Allow Safe Pass-Through of
Fish
These new fish-safe
turbine designs are used for fish migrating downstream. Pass-around designs are
still needed for upstream migration. Many older dams do not have fish bypass
facilities. Adding a fish-safe turbine to these would still be beneficial. Natel
Energy’s turbines, which are described below, have blunt leading edges and the turbine
blades are curved to complement the curve of fish spines. The result, according
to Natel, is safe passage for 98-100% of fish smaller than 20cm in length.
Natel Energy’s New Fish-Safe Turbine Designs
Natel Energy
was founded by two siblings, a brother and sister who are both MIT alumni. The MIT
Technology Review article explains Natel’s new turbine designs through one of
its cofounders:
“The company started with two big goals: high
performance and fish survival, says Gia Schneider, Natel’s cofounder and chief
commercial officer.”
“The company is making new designs for the turbines
that generate electricity in hydropower plants as water rushes through
equipment and moves their blades. Conventional turbine blades can move as fast
as 30 meters per second, or about 60 to 70 miles per hour, Schneider says. When
straight, thin edges are moving that quickly and striking fish, “it’s fairly
obvious why that’s not a good outcome,” she says.”
“Natel’s turbine design focuses on preventing
fast-moving equipment from making fatal contact with fish. The blades have a
thicker leading edge that pushes water out in front of it, creating a
stagnation zone, or “basically an airbag for fish,” Schneider says. The blades
are also curved, so even if fish are struck, they don’t take a direct hit.”
Natel started
out designing Pelton Wheel Turbines, a kind of impulse turbine that extracts
energy from the impulse of moving water instead of the weight of the water.
These have been around since the 1870’s. When designing turbines for small river
hydro projects they discovered that thicker turbine blades that were curved to
match fish spine curves resulted in few to no deaths. The ratio of turbine
blade thickness to the length of the fish is considered in the design. The blades
are also slanted forward which results in glancing blows rather than direct
blows. The design does require the turbine speed to be slowed to 7 to 10 m/sec
but that is up to double the speed of 5 m/sec required for fish safety of conventional
turbines. Turbines that run at lower speeds have less issues with cavitation,
which is when high-speed bubbles make pits in the metal turbine blades. Natel
used Alden Labs to study their turbine’s effects on passing fish. According to
an article quoting the founders:
“You can expect 100 percent mortality for fish 20
centimeters long if struck by the leading edge of a rotating blade 10
millimeters thick,” Schneider said. That is the size of the blades for the
conventional compact 1-MW turbines found on dams with 5 to 7 meters of head.”
“The expense of keeping out fish is high as it stalls
or stops many small hydro projects since the solutions are so expensive. It is
enough of a problem that the Electric Power Research Institute commissioned
Alden Labs, a fluid engineering firm, {to} study the problem.”
“They found that fish do not notice spinning turbines.
Once in them, the turbine accelerates the fish. When the thin turbine blades
strike them, they break the fish’s spines.”
“Initial data showed that at 5 m head, 100 percent of
20 cm fish passed safely through the turbine. At 10 m head, 98 percent went
safely through. That is close to Natel’s design goals and roughly as good as a
fish spillway.”
Natel also
designs bypasses that attempt to optimize the natural features of rivers. This
also allows for the passage of river sediment, something that dams can prevent
that could even lead to coastal erosion downstream. As shown below, these
designs mimic natural features like log jams, beaver dams, and rock arches.
Thus far,
Natel has installed two versions of its latest turbine, the Restoration Hydro
Turbine, at existing plants in Maine and Oregon. By the end of this year, two
more will be deployed, including one in Europe, a key market due to stronger hydropower
regulation. The two installed turbines have been found to convert more than 90%
of available water energy to power the turbine, which is comparable to
conventional hydro turbines. The company estimates that 30GW of hydro capacity in
Europe and the U.S. could be retrofitted with their turbines and that their
turbines can avoid shutdowns and retirements at relicensing time. They also hope
to build new plants on existing non-powered dams, noting that only 3% of the
80, 000 U.S. dams are powered. They estimate that this could result in up to
48GW of new hydropower in the U.S. and Europe. I include links to some of the testing
and validation results in published papers in the references.
Andritz’s Pass Through Fish-Safe Turbine Designs
Another hydropower
supply company that designs fish-safe turbines is Andritz. Some of their turbine
designs, simulations, and mortality analysis are shown below.
Regarding the
study at the Xayaburi hydropower plant in Asia, shown above as the example of a
fish ladder, the company noted:
“By implementing these technologies and developments,
a 90% survival rate of the fish passing through a turbine can be ensured. It
should also be noted that only about 20% of all migrating fish are affected by
the turbine, since the majority of the fish population are protected by other
measures, such as fish ladders and bypass passages.”
That is pretty good but Natel’s 98-100% is better. However,
I am not aware of the details like turbine speeds and dam heights that would
make comparisons equal.
Other Fish-Safe Turbine Designs
The DOE’s
Office of Energy Efficiency and Renewable Energy notes two other turbine
designs that achieved a 98% survival rate for fish passing through the turbine
chamber. One the Army Corps of Engineers’ Ice Harbor Dam on the Snake River,
which was installed in 2016. Another is the Alden Fish-Friendly Turbine which
produced similar survival rates. Research is ongoing for fish pass-through and
pass-around systems. Sensors are used to tag and track fish movement and to
monitor the effects on different species.
References:
Company
makes revolutionary development in hydropower with 'fish-safe turbines':
'Basically an airbag for fish'. Susan Elizabeth Turek. The Cool Down. July 23,
2024. Company
makes revolutionary development in hydropower with 'fish-safe turbines':
'Basically an airbag for fish' (msn.com)
How
fish-safe hydropower technology could keep more renewables on the grid. Casey
Crownhart. MIT Technology Review. July 1, 2024. How
fish-safe hydropower technology could keep more renewables on the grid | MIT
Technology Review
How Do
Fish Survive Hydropower Dams? U.S. Department of Energy. Office of Energy
Efficiency & Renewable Energy. April 29, 2024. How
Do Fish Survive Hydropower Dams? | Department of Energy
A path
to fish-friendly hydropower. Yoana Cholteeva. Power Technology. January 25,
2021. A
path to fish-friendly hydropower - Power Technology (power-technology.com)
Hydropower
making sustainability gains with fish-safe turbines. Guest Contributor. Power
Engineering International. November 16, 2023. Hydropower
making sustainability gains with fish-safe turbines - Power Engineering
International
Natel
Energy: Making Hydropower Plants More Fish-Friendly and Sustainable. Zach Winn,
MIT. Sci Tech Daily. August 5, 2022. Natel
Energy: Making Hydropower Plants More Fish-Friendly and Sustainable
(scitechdaily.com)
Protecting
fish and livelihoods: Fish-friendly assessment in practice. Andritz. Protecting
fish and livelihoods - Fish-friendly assessment in practice (andritz.com)
Towards
more fish-friendly hydropower plants. ETH Zurich. February 2021. Towards
more fish-friendly hydropower plants | ETH Zurich
Estimated
capital costs of fish exclusion technologies for hydropower facilities. Paul G.
Matson, Kevin M. Stewart, Gbadebo A. Oladosu, Emrat Nur Marzan, and Scott T.
DeNeale. Journal of Environmental Management. Volume 351, February 2024, 119800.
Estimated
capital costs of fish exclusion technologies for hydropower facilities -
ScienceDirect
Design
and validation of fishsafe hydro turbines for retrofit andnew-build
applications. A.D. Schneider and S.M. Watson, Natel Energy, USA. International Journal
on Hydropower and Dams. Issue 5. presented at the HYDRO 2023 conference in Edinburgh
(October 2023). Layout
1 (website-files.com)
Improving
survival: injury and mortality of fish struck by blades with slanted, blunt
leading edges. Stephen V. Amaral, Sterling M. Watson, Abraham D. Schneider, Jenna
Rackovan, and Andrew Baumgartner. Journal of Ecohydraulics. Volume 5, 2020. Pages
175-183. June 16, 2020. Full
article: Improving survival: injury and mortality of fish struck by blades with
slanted, blunt leading edges (tandfonline.com)
Fish-Safe
Turbines Empower Small-Dam Hydro Projects. Alan Brown. The American Society of
Mechanical Engineers. August 20, 2019. Fish-Safe
Turbines Empower Small-Dam Hydro Projects - ASME
Pelton
wheel. Wikipedia. Pelton
wheel - Wikipedia
Innovative
technologies from FIThydro. FIThydrowiki. Innovative
technologies from FIThydro - FIThydrowiki
Bedload
monitoring system. FIThydrowiki. Bedload
monitoring system - FIThydrowiki
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