POWER October 2015 - 62

HYDROPOWER
to beneficial aquatic life and adds nothing
to the aquatic environment. The technology
is inexpensive and has low maintenance requirements.
Pumped
Storage Ramps Up
Many observers expect PSH to play an increasingly
important role as intermittent
renewables like wind and solar grow in installed
capacity. China is planning to add
around 130 GW of PSH capacity by 2050
to its current total of 23 GW. (For one example
of PSH's role in grid management, see
" Ludington Pumped Storage Plant Increases
Efficiency to Provide Greater Grid Support "
in this issue.)
Adjustable-speed (AS) pump-turbines are
the most significant recent advance in PSH
because they give a PSH plant the ability to
offer frequency regulation services, as well as
varying the power consumed in pump mode
over a range of outputs and generally increasing
overall efficiency. Greater deployment of
AS pump-turbines will be key to greater renewable
integration. While AS PSH is common
in Japan, it is still a small component
of the PSH fleet globally, especially in the
U.S. A 2014 study by the Argonne National
Laboratory estimated that the addition of
three proposed AS PSH projects in Califor4.
Leak stopper. Polyurea coatings can be added to existing pumped storage reservoirs to
greatly reduce leaks and maintenance. This facility in Australia was losing 150 gallons a minute
through its asphalt substrate prior to adding the liner. Courtesy: Versaflex
nia would cut potential wind curtailments in
2022 by 20% as well as offering significant
financial benefits to the grid.
With many PSH facilities having been in
operation for decades, upgrades are necessary
to keep them operating efficiently on
the modern grid. With smaller plants that use
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POWER | October 2015
lined reservoirs for storage, one key concern
as they age is water exfiltration/infiltration
as a result of leaks in the liner. Asphalt-lined
reservoirs are a particular concern because of
asphalt's vulnerability to freeze-thaw cycles.
Advances in coating materials now offer
easier repair options for leaks and much better
long-term durability. Polyurea coatings and
liners are increasingly being used because of
the material's flexibility, durability, and low
maintenance requirements. Polyurea can be
applied directly to the existing substrate and
cures in as little as an hour (Figure 4). For
areas that experience freezing temperatures
during the winter, polyurea is much more
" ice friendly " than asphalt or concrete as it is
able to release frozen ice without damage.
For internal components at a hydropower
plant, hydrophobic coatings can be applied
to improve efficiency and reduce corrosion,
erosion, and bio-fouling, but existing technologies
are not as durable as they need to be.
One possibility for the future, according to
a presentation by researchers from the Massachusetts
Institute of Technology, is rare
earth oxides (REOs). Tests have shown that,
properly applied, REO coatings can create a
highly hydrophobic, highly durable layer on
piping and turbine elements.
Hydro's Benefits Keep Flowing
Hydropower does not always get the attention
that wind and solar do, but its advantages
are certain to keep it an important element
of the power mix in the future, especially as
a resource to back up intermittent generation
elsewhere. Large and small, hydro appears to
have a bright future. ■
-Thomas W. Overton, JD is a POWER
associate editor.

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POWER October 2015

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