How can US states with aggressive decarbonization goals coupled with
federal decarbonization goals have energy when they need it?
Long-duration energy storage (LDES) is a likely candidate. LDES
systems are large energy storage installations that can store
renewable energy until needed and can provide a much-needed solution
for a reliable and decarbonized grid. But planning needs to start now,
according to new research from Pacific Northwest National Laboratory (PNNL).
“Defining Long Duration Energy Storage,” a report by Senior
Energy Analyst Jeremy Twitchell and Waterpower Advisor Kyle DeSomber
from PNNL, explores how the growth of renewable energy generation will
require LDES to fill the gap between variable energy generation and
customer demands. The report also describes the barriers in current
energy planning and procurement processes that prevent planners from
recognizing those needs.
“This isn’t something we are going to be able to flex out of
like we have in the past,” said Twitchell.
“Things like energy efficiency, demand response, and
overbuilding generation capacity will all be part of the solution. But
when you look at the sheer size of these mismatches between when
energy is produced in a decarbonized grid and when it is consumed, we
simply can’t deploy those things at the required scale,” Twitchell
added.
The report, published in the Journal of Energy Storage, looks
at how the amount of variable energy—such as wind and solar—available
for the grid is changing, outlines new definitions for long-term
energy storage, and uses an illustrative example of California’s power
needs to demonstrate future shortfalls.
Why does this matter now?
In addition to the nonbinding federal goal that all electric
generation will be provided from clean energy sources by 2035, many
more states have adopted binding or nonbinding decarbonization
policies—which means a fundamental change in how energy is produced.
For example, 16 states and territories have binding requirements for
100 percent clean or net-zero energy (12 states at 100 percent clean
energy, four states at net zero), and six states have non-binding
goals for 100 percent clean or net-zero energy (three states at 100
percent clean energy, and three states at net zero).
Why do variable energy sources and planners need
long-duration energy storage?
Variable energy resources are increasingly included as a
central component of how grid planners meet customer demand. But
variable energy is exactly that—variable. For it to produce energy,
the wind needs to blow, or the sun needs to shine. This poses a huge
challenge for grid operators that must meet customer demands in real
time.
LDES gives electricity a shelf life so grid operators can use
it more effectively and for longer terms when taking into
consideration changing customer demands, climate, extreme weather
events, and seasonal dependencies.
Think of energy storage systems like the battery in your cell
phone, which only stays charged for so long despite there being small
things that can extend the battery’s life. If your phone is not
recharged, it will die. The same is true with long-duration energy
storage.
Currently, LDES is loosely defined anywhere between 10 to 100
hours. Twitchell and DeSomber propose that industry adopt two classes
of LDES: one class, diurnal, lasts up to 20 hours to reconcile daily
cycles of surplus and deficits in generation. The second class,
seasonal, reconciles seasonal periods of surplus power generation with
seasonal periods of insufficient generation. By thinking of
long-duration energy in two different ways, utility and grid planners
can look at historical load data and better pinpoint the length of
“stop gap” energy that will be needed.
California … we have a mismatch
Using load and generation data from the California
Independent System Operator, Twitchell and DeSomber created a model to
show energy shortfalls. “Looking at our data in our illustrative
example of California, the deficit is 30 gigawatts of capacity in one
day—approximately half of California’s total generation in one day,”
said Twitchell. To make up that deficit, the state would need 15
Hoover Dams producing energy over that same period.
![](images/images_05_31_2023/EED_2376_ANIM_TwitchellGifs_v4-1.gif)
Even with times of surplus energy generation,
California will face even deeper deficits despite additional power
generated from other sources. (Animation by Stephanie King | Pacific
Northwest National Laboratory)
As expected, energy consumption is highest during the morning between
5 – 8 a.m. and in the evening after 5 p.m. Throughout the day, solar
resources begin producing energy, which helps offset what customers
need. Demand is at its highest at 6 p.m., but solar-produced energy
begins to dramatically fall from 5 – 8 p.m., which creates a
shortfall.
![](images/images_05_31_2023/EED_2376_ANIM_TwitchellGifs_v3.gif)
California uses energy from other sources, such as natural gas
generators (their largest source of energy right now), lithium-ion
batteries, and other states’ energy surplus, to augment what is lost.
However, as more energy storage assets are dedicated to this service,
the duration requirements increase as the remaining peak becomes
flatter and longer. (Animation by Stephanie King | Pacific Northwest
National Laboratory)
Long-duration energy storage for the future
Binding clean energy targets set in 28 states and Washington,
D.C. will require about 34 percent of electricity consumed in the
United States to be from non-emitting resources by 2050, based on
those states’ share of electricity consumption in 2020. This means
that by the year 2050, the amount of non-emitting generation on the
grid will need to increase by almost 50 percent.
Incorporating all that variable generation while keeping the
lights on will be a significant undertaking.
“Much of the research that has been done in this space
concludes that long-duration energy storage can reduce the costs of
operating a fully decarbonized power grid,” said Twitchell. “These
findings are important, but our paper takes the additional step to
explain that long-duration energy storage is not a luxury, but a
necessity. This is not an economic paradigm, it’s a reliability
paradigm.”
Others in industry and research are collectively tackling this
challenge as well. One of them is Julia Souder, the CEO for the Long
Duration Energy Storage Council, a global non-profit that works to
accelerate the decarbonization of the world through the acceleration
of long-duration energy storage.
“LDES is a necessity to effectively de-risk our clean energy
future and PNNL reiterates the critical fact that the clean energy
transition is not possible without it,” Souder said. “As the market
matures, grid planners and operators will benefit from the research
here that displays how LDES provides a flexible, resilient, secure,
and affordable solution to meet tomorrow’s energy grid needs. And, as
we look to multi-hour, multi-day, and seasonal energy storage
solutions to achieve 24/7 clean energy, the planning and procurement
process needs to be much more inclusive to allow LDES to fully
participate in the market.”
Now is the time to act
Twitchell, DeSomber, and Souder all agree: the time to act is
now.
“The motivation for this paper and research was to make the
case that LDES will be an absolute necessity in a decarbonized grid,”
Twitchell said. “If we want it to be available when we need it, then
we need to start sending clear market signals that will support
research and development of LDES technologies now. These technologies
take years to develop, but our energy planning and procurement
processes work on short (less than three-year) cycles. By the time our
processes identify LDES needs, there won’t be time to develop and
deploy them.”
Funding for this report came from the Department of Energy
Office of Electricity and supports its efforts for the Long Duration
Storage Shot, the Office of Electricity Storage Program (research and
materials development), as well as the Department of Energy’s Net Zero
Labs Pilot Initiative, in which PNNL plays a collaborative effort to
apply the national laboratory’s scientific and technological knowledge
to create tangible solutions for achieving net-zero emissions.
PNNL hosts a monthly webinar series, Energy Storage@PNNL, on
behalf of the Office of Electricity for the Grid Storage Launchpad.
These monthly webinars are conversations with experts on the future of
energy storage. The March webinar, Long-duration Storage Policy and
Economics, was hosted by Twitchell and featured insights from three
industry leaders.
![](images/images_05_31_2023/pic5.jpg)
Click to view past energy storage webinars and register for upcoming
ones.
By Courtney Stenson, courtesy of PNNL.
Green Play Ammonia™, Yielder® NFuel Energy.
Spokane, Washington. 99212
www.exactrix.com
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