POWER March 2021 - 25

SUSTAINABILITY
A Fish-Friendly Hydro Turbine
Expanding the use of hydropower
comes with the unique challenge of
minimizing disruption to watershed
ecosystems and mitigating impacts
to fish and other aquatic wildlife. Alameda,
California-based Natel Energy
claims to have the answer. The
company says its Restoration Hydro
Turbine (RHT) design enables sustainable,
climate-resilient, low-cost hydro
by combining approaches used to restore
watersheds, remove dams, and
build new recreational features (such
as river surfing waves and white water)
with fish-friendly, compact, modular
power generation.
" When my brother and I were coming
up with the idea for Natel Energy,
the conundrum we faced was how
to
build hydro
differently
than it's
been done for the last 100 years, " Gia
Schneider, Natel Energy's CEO and cofounder,
told POWER. " We knew the
approach going forward would likely
be distributed, and not necessarily
building huge dams. Our main focus
was, first and foremost, building an efficient
and fish-safe turbine, because
in hydropower, your choice of turbine
defines the rest of your powerhouse
and civil work. "
Restoration Hydro projects provide
several benefits, including habitat
creation, improved water quality, and
sustained increases in groundwater.
When deployed strategically at multiple
sites across a basin, the development
enhances river, wetland, and
watershed connectivity, which can
help mitigate the impacts of droughts
and floods. Restoration Hydro projects
can also link irrigation networks to improve
agricultural productivity, and can
provide water supply systems for sanitation
and household consumption in
developing countries.
RHTs (Figure 2) can be installed in
a range of settings, including retrofits
of existing small hydro plants (for lowcost
compliance with environmental
requirements or to improve output
of old units), at existing non-power
dams, in irrigation canals, on dam removal
projects combined with new
hydro, and in run-of-river new stream
reach developments. Special fishfriendly
blades are optimized for low
head-between 2 meters (m) and 10
m (about 6.5 ft to 33 ft)-eliminating
the need for fine fish screens, thus
increasing total plant efficiency while
reducing both upfront, and operations
and maintenance costs. The thick,
slanted blades deflect fish around the
March 2021 | POWER
projects for their ESG performance,
helping to set minimum performance
expectations for the sector, and publicly
rewarding projects for meeting
those expectations.
Costa said that over the past 10
years the hydropower sustainability
tools have been officially applied to at
least 35 hydropower projects around
the world, and unofficially to many
more. He noted that the three tools-
HGIIP, HSAP, and HESG-are aligned
and complementary.
2. The Restoration Hydro Turbine (RHT)
combines high performance, safe fish passage,
and a short draft tube for simple civil
works. The RHT is also offered as a runner
retrofit, allowing existing hydropower
installations to upgrade without major
changes to plant infrastructure. Courtesy:
Natel Energy
blade, reducing direct strike impacts.
" The blades in our turbine have a
unique shape that makes them somewhat
like an airbag, " Schneider said.
" If fish hit them, the fish are deflected
around the blade, as opposed to being
struck sharply in a manner that results
in cuts, abrasions, breaks, or other injuries.
In addition, our turbines have
fewer blades compared to conventional
turbines, which reduces the chance
that a fish hits a blade when passing
through the turbine. "
Results have been very positive.
For example, testing done in partnership
with Alden Laboratory demonstrated
that when rainbow trout were
subjected to strikes with a 100-millimeter-thick
blade at velocities of 10
m/sec at a location along the blade
with a 30-degree slant relative to
the tangential direction, the survival
rate was 98% compared to 26.8%
survival at a location with a 90-degree
slant. Additionally, in September
2020, Pacific Northwest National
Laboratory (PNNL) executed tests
that revealed a 100% survival rate
for fish up to 15 inches long passing
through Natel Energy's 1.9-meterdiameter
D190 RHT at the Monroe
Drop Site in Madras, Oregon. PNNL's
test, which utilized sensor fish and
balloon tag technologies to analyze
the physical turbine stressors and
recover trout to assess passage condition,
revealed minimal injury or impact
to fish passage, even when the
RHT was operated at full power.
" These results provide important
evidence that, if designed correctly,
small hydropower facilities do not have
to compromise between generation
efficiency and biological performance, "
Schneider said.
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" It is really a unified set of tools that
provide this common language around
sustainable hydropower, both for financiers,
hydropower developers, civil society,
and this is a big aim of these tools,
and this is what they do, " Costa said.
" The assessment process is an evidence-based
process. It's very practical.
It implies having an independent
accredited assessor going to the site,
doing the site inspection, interviewing
the affected stakeholders from the
communities to developers to all actors
involved, and also reviewing the documentation.
So, it's really a very wellstructured
and very precise activity that
provides enough evidence to take solid
conclusions, " he said.
The tools are designed to be applicable
from the early stage of development,
when ideas are still being
formed and options evaluated, through
the preparation, implementation, construction,
and operation of hydropower
projects.
" It's applicable to
all
projects-same
methodology for any type
of project, for any size of project, for
any location-provides really that common
language, that unifying tool, and
ultimately, it will allow projects to
prove their performance across a range
of topics, " said Costa.
Among the items produced during
an HSAP assessment is a sustainability
profile, which is an easy-to-comprehend
diagram that allows stakeholders to
quickly gauge a project's performance
across more than 20 sustainability topics.
The visual can help decision-makers
better understand various aspects of a
project, identify areas for improvement,
align with financial mechanisms, make
better choices, manage the process,
and meet ESG objectives. Costa said
the goal of the new standard is not to
provide a threshold for sustainability,
but rather, to improve transparency and
encourage continuous improvement. ■
-Aaron Larson is POWER's
executive editor.
25
http://www.powermag.com
POWER March 2021

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