IEEE Electrification - December 2021 - 4

TECHNOLOGY LEADERS
The Future of Electricity Storage:
From Hours to Days
By Paul Albertus
E
LECTRICITY SYSTEMS
have long relied on extensive
amounts of fuel storage
to avoid supply disruptions and
ensure that electricity can be delivered
as needed. On-site storage of
nuclear fuel and coal, as well as
pipeline and underground storage of
natural gas, are typically able to provide
conventional generators with
weeks to years of secure fuel supply,
and lack of access to fuel by large
scale-generators is rare. However, as
electricity supply systems shift to
increased use of the variable renewable
energy sources (RESs) wind and
solar, due to favorable cost and emissions
attributes, there are fundamentally
new challenges for grid
planners and operators as the
annual share of electricity from
these sources reaches 50% and
higher. These trials include faster
ramp rates for conventional assets,
a reduction in the inertia of rotating
generators, and spatial changes in
generation assets (and hence alterations
in transmission and distribution
networks) as well as market
challenges around adding a large
fraction of generation assets with
no fuel costs and a limited ability
for scheduling.
To address these, there are several
technical options to expand the
Digital Object Identifier 10.1109/MELE.2021.3115539
Date of current version: 1 December 2021
4
use of intermittent wind and
solar while ensuring a stable supply,
including
1) expanding the transmission network
to enable greater spatial
averaging of variable generators
2) expanding load flexibility through
demand response and other programs
for industrial and residential
customers
3) ramping conventional generators,
such as natural gas peakers,
potentially including carbon capture
and sequestration to limit
greenhouse gas emissions
4) curtailing intermittent resources
beyond those needed at the time
of production
5) storing electrical energy generated
by wind and solar.
While the first four options are
being pursued, they have significant
limitations. For example,
1) expanding the transmission network
is slow because of permitting
challenges associated with
public resistance
2) expanding load flexibility has difficulties
achieving significant
load reductions because of customer
hesitancy about the
programs
3) ramping conventional generators
still results in emissions and if
combined with carbon capture is
quite expensive
4) curtailment increases costs and
will eventually require the building
IEEE Electrification Magazine / DECEMBER 2021
of less favorable projects as the
best sites are taken.
Hence, there are significant
opportunities in the fifth option, electrical
energy storage, due to its
potential to provide truly large-scale
(i.e., hundreds of gigawatts) electricity
time shifts without emissions or
significant permitting problems.
The role of energy storage has
long been recognized, as evidenced
by the presence of pumped-storage
hydro (PSH) facilities, which in the
United States have a power capacity
of around 23 GW, with an average
duration of roughly 10 h, for a total of
approximately 230 GWh. PSH is by
far the largest form of electrically
charged storage in the world today.
However, there are only a few new
large-scale facilities being constructed
because of environmental and
other constraints. While a number of
thermal storage facilities integrated
with concentrating solar power
plants have been and will be built,
they are charged with heat rather
than electricity and therefore cannot
be used to store the power from the
large amount of solar photovoltaic
and wind coming online.
Of the new electrically charged
storage facilities being placed in service,
batteries constitute the largest
fraction by far, specifically lithiumion
(Li-ion) technology. Li-ion was
developed for portable electronics
and adopted for vehicles, and in the
2325-5897/21©2021IEEE
IEEE Electrification - December 2021

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