Hydropower was the world's first large-scale renewable
energy source. It's still by far the largest renewable
worldwide, producing over twice as much energy as wind
and over four times as much as solar.
And pumping water up a hill, aka pumped storage
hydropower, comprises well over 90% of the world's
total energy storage capacity.
But in spite of hydropower's outsize impact,
we don't hear much about it.
Hydropower has to date been seen as an old technology,
one that's existed forever and doesn't really need
incentives in order to be developed.
While the past few decades have seen wind and solar
plummet in price and skyrocket in availability,
hydropower generation in the U.S.
has remained relatively steady.
But some are advocating for its expansion.
The era of big dam construction in the United
States is over. However, there's still huge potential
for growth in the industry using the existing
infrastructure. We have 90,000 dams in this country,
most of which were built for flood control, for
irrigation, for water storage, for recreation.
Only 3% of those dams are actually used for generating
power.
Adding electricity generating turbines to
existing dams is the way forward for domestic hydro.
But internationally, it's a different story.
China has driven global expansion for decades by
building thousands of new, oftentimes massive
hydroelectric dams.
And India, Africa and other Asia-Pacific countries are
set to do the same. But expansion without strict
environmental oversight could lead to trouble, as
dams and reservoirs disrupt river ecosystems and
surrounding habitats.
And recent studies show that reservoirs can emit
more CO2 and methane than previously understood.
As the climate changes, drought is also making hydro
a less reliable source of energy.
The Hoover Dam, for example, has lost over 30%
of its generating capacity.
What you're seeing here behind me is about 160 feet
of white walls. That represents the drop of Lake
Mead's elevation since it was last full at the
beginning of the century.
But despite the challenges, experts say that hydro has a
big role to play in a 100% renewable future.
We can't have a grid dependent just on wind,
solar and batteries.
We're not going to have 24/7 reliable power without
the flexibility and the long duration energy storage
that hydropower and pumped storage can provide.
The world's first hydropower plant began operation in
1882, far before wind or solar farms blanketed the
land.
And we really helped power America's Industrial
Revolution. And it's been a clean source of renewable
power ever since.
In 2021, hydropower accounted for about 6% of
utility-scale electricity generation in the U.S.
and 32% of renewable electricity generation.
Domestically, it was the largest renewable until
2019, when it was surpassed by wind.
The way it works is pretty simple.
In traditional hydro projects, a river is dammed,
creating an elevation difference. As the water
flows from the upper reservoir to the river
below, it turns turbines that power
electricity-producing generators. Noe Santos from
the Bureau of Reclamation takes us inside the world
famous Hoover Dam.
So the water behind me is the Lake Mead.
And we're actually sitting on top of one of the intake
towers on the Arizona side.
And from there, the water enters the intake towers and
through the various penstocks and laterals that
are inside the dam. And those are used to then power
17 generators within the dam.
And that water is then released into the Colorado
River below, which then flows into Lake Mojave.
When Hoover was built during the Great Depression, it was
the most powerful hydroelectric dam in the
world. And while the dam's reservoir, Lake Mead, is
still the largest reservoir by volume in the U.S., it
hasn't been full in over 20 years and is currently at an
all-time low.
So in a typical year, Hoover Dam will generate about 4.5
billion kilowatt hours.
With the lake being the way it is now, it's more like
3.5 billion kilowatt hours.
So that's equivalent to about 450,000 homes in a
normal year and about 350,000 homes in these
drought years.
Reservoirs on the East Coast are faring better in terms
of water supply. But all across the country it's
still incredibly hard to get a new hydropower plant
built or to relicense a dam after its initial license
expires.
It costs tens of millions of dollars and years of effort
to go through the licensing process.
And for some of these facilities, particularly
some of the smaller facilities, they just don't
have that money or that time.
So we could be facing a raft of license surrenders
just as we're trying to ramp up the amount of
flexible, carbon-free generation we have in this
country.
The licensing process combined with the nation's
aging dams are major reasons why domestic hydro
isn't expected to grow much in the coming decade.
That doesn't mean the possibility isn't there,
though. The Department of Energy says that traditional
hydropower, excluding pumped storage, has the
potential to expand by nearly 13% by 2050, mainly
through upgrades to old plants and adding power to
existing dams.
Pumped storage hydropower has significantly greater
growth potential in the U.S. While pumped storage
has about 22 gigawatts of electricity-generating
capacity today, there's over 60 gigawatts of
proposed projects in the development pipeline.
That's second only to China. This technology
functions like a giant battery.
While traditional hydropower has just one
upper reservoir, pumped storage has an upper and a
lower. When a pumped storage facility is
generating power, water flows from the upper
reservoir to the lower, passing through a turbine to
generate electricity. The difference is that a pumped
storage facility can recharge, using power from
the grid to pump water from the lower reservoir up to
the higher one, storing potential energy that can be
released when needed.
The Bath County Pumped Storage Station in Virginia
is the largest facility of its kind in the world.
Station director Sean Fridley showed us around.
These reservoirs are approximately 550 acres in
size, that's surface area.
And we've got the capacity to move about 28,000 acre
feet of water between the two stations.
The station can power about 750,000 homes and can supply
continuous power for about 10 hours.
Utility-scale lithium-ion batteries generally max out
at around 4 hours of energy storage.
While lithium batteries and other technologies are
getting a lot of headlines, the proven value of pumped
storage, I think, has been overlooked.
And that's beginning to change.
Woolf says there's over 90 proposed domestic projects.
And as more intermittent energy sources like wind and
solar come onto the grid, pumped storage is gaining
traction as a way to firm renewables by storing excess
energy for use when the sun isn't shining and the wind
isn't blowing.
So there are times now in California when we're
producing too much solar power.
And rather than curtail that solar power, that's
when pumped storage can actually take a load off the
grid, pump water back up and make it available for
sunset when we're going to need that power again.
Just like traditional hydro, pumped storage poses
environmental challenges.
But there are ways of building these facilities
that could greatly lessen their impacts.
All of the U.S.'s 43 pumped storage facilities are
open-loop, which means the lower reservoir is connected
to a water source like a river. But closed-loop
facilities, in which neither reservoir is
connected to an outside water source, are generally
more environmentally friendly since they don't
disrupt river ecosystems.
And since they don't need to be near a river, they can
be sited more flexibly to minimize impact.
In recent years, permits and licensing applications
for closed-loop systems have increased considerably.
Smaller pumped storage facilities, which could use
tanks instead of reservoirs, are also being
considered.
There's a variety of new technologies that are being
deployed around the world, although not yet in the
United States, where they're finding thousands
and thousands of untapped areas and resources where
you can put these facilities in an
ecologically responsible way.
However, there's always going to be some level of
environmental harm that comes from damming rivers or
creating new reservoirs.
This development can obstruct fish migration and
ruin surrounding ecosystems and habitats.
Dams and reservoirs have even displaced tens of
millions of people throughout history, usually
indigenous or rural communities. These harms are
widely acknowledged, but it turns out there's even more
to worry about.
What people don't realize is that these reservoirs
actually emit a lot of carbon dioxide and methane
into the atmosphere.
The emissions come from decomposing vegetation and
other organic matter, which break down and release
methane when an area is flooded to create a
reservoir.
Usually that methane then turns into carbon dioxide,
but you need oxygen in order to do that.
And if the water is really, really warm, then the bottom
layers are depleted of oxygen.
So that decomposition process ends at methane, and
then the methane kind of just bubbles out and goes
into the atmosphere.
Methane is over 80 times more potent than CO2 for the
first 20 years after its release.
But the amount of emissions released from any given
reservoir varies widely.
Some reservoirs absorb more CO2 than they emit, while
certain climates and conditions can cause others
to emit concerning levels of methane.
So far, research shows that hotter parts of the world,
like India and Africa, tend to have more polluting
plants, which is worrisome since both areas are
expected to drive hydropower growth this
decade. Thankfully though, Ocko says that China's
reservoirs are not high emitters.
While growth is slowing in the country, it still plans
to build more hydro capacity by 2030 than any
other nation. Ocko also says that reservoirs in the
United States are not of particular concern, but
what's really needed is a more robust emissions
measuring program.
And then you could have all sorts of incentives to
reduce it or regulations to make sure that you're not
emitting too much.
Another major problem for hydropower is climate-driven
drought. Shallow reservoirs produce less power, because
the less water, the less force with which that water
can spin a turbine.
The last 23 years, we've experienced the driest 22
year period on record.
As reservoirs like Lake Powell, which feeds the Glen
Canyon Dam, and Lake Mead, which feeds the Hoover Dam,
produce less electricity, fossil fuels are picking up
the slack. One study found that from 2001 to 2015, an
additional 100 million tons of carbon dioxide were
released across 11 states in the West due to a
drought-induced shift away from hydropower.
During a particularly rough patch for California between
2012 and 2016, another study estimated that lost
hydropower generation cost the state $2.45 billion.
For the first time in history, a water shortage
has been declared at Lake Mead, triggering water
allocation cuts in Arizona, Nevada and Mexico.
Hoover's operational staff said they don't expect
additional cuts to happen this year, though they could
in 2023. The water level, currently at 1,050 feet, is
only expected to drop further as the Bureau of
Reclamation has taken the unprecedented step of
holding back water at Lake Powell, which is situated
upriver of Lake Mead, so that the Glen Canyon Dam can
continue to produce hydropower. If Lake Mead
drops below 950 feet, it will no longer be able to
produce power.
But unfortunately, one thing that we can't control is the
changing climate for sure. It's really hard to predict
year to year how much water we can expect.
Current models that are online show that Lake Mead
could fall to around an elevation of 1020 or so.
As levels continue to plunge, dead bodies have
been found in the lake. And one of the original intake
valves has been exposed, so it can no longer draw in
water. With critical hydropower infrastructure
threatened by drought, it throws into question how
reliable this energy source really is in a world where
unprecedented weather trends are becoming
commonplace.
Modernizing existing hydropower infrastructure
could increase efficiency and recoup some
drought-related losses though, as well as ensure
that plants are able to operate for decades to come.
Between now and 2030, $127 billion will be spent on
modernizing old plants globally.
That accounts for nearly one fourth of total global
hydropower investment and nearly 90% of investment in
Europe and North America.
At the Hoover Dam, that's meant retrofitting some of
their turbines to operate more efficiently at lower
elevations.
They're good at these lower lake elevations, but when
the lake fills back up again someday, they're good
for those elevations as well. They're more efficient
and they're able to deal with the wider variability
that we see in those pressures.
Cook also says they've installed thinner wicket
gates, which control the flow of water into the
turbines. Thinner gates can increase flow rates, thereby
increasing efficiency.
The team is also injecting compressed air into turbines
to increase efficiency.
Fully modernizing all the world's aging plants would
cost a whopping $300 billion though, more than
twice current spending projections. But in other
parts of the world, the majority of investment is
going towards construction of new plants.
Large, state-owned projects in Asia and Africa are
expected to account for over 75% of new hydropower
capacity through 2030.
And while the rate of hydropower growth within
China is slowing, the country is investing heavily
in global development. Over half of new projects in
sub-Saharan Africa, Southeast Asia and Latin
America are expected to be built, financed or owned by
Chinese companies. While these types of large
international projects are set to drive global
expansion, Ames worries about the impact such
projects will have on the environment.
In my humble opinion, they're overbuilt.
They're built to massive capacity that isn't
necessary, and they're built around the assumption
of massive reservoirs.
They could be done as run-of-river.
They could just be designed differently.
Run-of-river facilities don't include a reservoir
and are thus less impactful on the environment, but they
cannot generate energy on demand since output depends
on seasonal flows.
Run-of-river hydropower is expected to account for
about 13% of total capacity additions this decade, while
traditional hydropower will make up 56% and pumped hydro
29%. But overall, hydropower growth is slowing
and is set to contract by about 23% through 2030.
Reversing this trend will largely depend on
streamlining the regulatory and permitting processes and
setting high sustainability standards and emissions
measuring programs to ensure community acceptance.
A shorter, simpler development timeline would
help developers to obtain power purchase agreements or
other long-term contracts, thereby incentivizing
investment since returns would be guaranteed.
This applies to the construction of new dams as
well as powering existing dams.
Part of the reason it doesn't look as attractive
as solar and wind is because the horizon for the
facilities is different.
A wind and solar plant typically gets looked at as
a 20 year project.
On the other hand, hydropower is licensed and
operates for 50 years and many of them have been
operating for 100 years.
But our capital markets don't necessarily appreciate
a longer return.
But finding the right incentives for hydropower
and pumped storage development, and ensuring
that it's done in a sustainable manner, is going
to be critical to weaning the world off of fossil
fuels.
The hydropower industry is really this forgotten giant.
So we do feel like an underdog.
We don't get the headlines that some of the other
technologies do. But I think folks are increasingly
realizing that you can't have a reliable grid without
hydropower.