ETA 2021 Strategic Plan - Flipbook - Page 18
In searching for a new technology, it helps to
take stock of the leading storage technology
for grid deployments: Li-ion batteries. With
growing demand for grid storage and barriers
to deployment of pumped hydro storage and
compressed air energy storage, what prevents
Li-ion batteries from being the technology of
choice? Answering this question helps to define
advantageous characteristics of Li-ion batteries
that, if emulated, would allow a new technology
to substitute for Li-ion batteries. It also helps
to define gaps in Li-ion technologies that, if
addressed, would allow a new technology to find
a foothold through features unavailable to a Liion battery.
Research Summary
ETA’s vision is to develop new, commercially
ready technologies that can economically
address the need for energy storage to
electrify the transportation sector and provide
sustainable, resilient electricity to the grid. This
initiative will examine market use cases for these
technologies, establishing a techno-economic
pathway to commercialization and deployment
within the grid infrastructure. It combines the
area’s long-standing expertise in developing
novel chemical, electrochemical, and thermal
technologies with policy analysis that can
demonstrate the economic use case for these
new technologies to relevant stakeholders.
Underlying the initiative is the realization that no
economically viable, widely deployable solution
for long-duration storage currently exists. The
largest source of stationary energy storage in
the power system is, by far, from pumped hydro
storage, largely due to investments made in the
1970s and 1980s.9 Almost no new pumped hydro
capacity has been developed in the United States
in the past two decades due to the difficulty of
siting, permitting, and financing this technology.
Other economical methods of storage, such
as compressed air energy storage, suffer from
similar limitations in siting and geographic
availability. What is needed is a long-duration
storage technology that can be deployed
anywhere, yet maintains or improves upon the
low cost of these historical technologies that
take advantage of geographic features.
9 U.S. Energy Information Administration. 2019. Most pumped storage electricity generators in the U.S. were built in the
1970s. Today in Energy. https://www.eia.gov/todayinenergy/detail.php?id=41833.
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Li-ion has undergone tremendous growth as it
revolutionized a portable electronics technology
and was adopted into plug-in hybrid electric
vehicles (PHEV) and grid applications. By 2030
production is expected to be several terawatthours (TWh), which will put significant strain
on the availability of lithium and the transition
metals used in cathode materials. One TWh of
Li-ion using nickel manganese cobalt (NMC) class
cathodes requires between 0.9 and 1.1 million
tons of nickel and/or cobalt metal, which far
exceeds cobalt production and is a significant
fraction of today’s world production of nickel.
The United States currently does not produce
lithium from its natural reserves, which creates a
supply chain risk. Meeting the need for massive
transportation and grid electrification appears
impossible with today’s NMC and nickel cobalt
aluminum (NCA) cathode technology.
As noted, Li-ion batteries have been known to
overheat, which under certain conditions can
lead to devastating fires and explosions. To
ensure their safety in all applications — including
transportation and large-scale grid storage —
better heat exchange and transfer technologies
need to be integrated into the battery systems
across all length scales. Alternatively, solidstate Li metal based batteries, which involve
nonflammable ceramic-like densified layers and
composites, can further increase energy density
and reduce the risk of catastrophic failure.
Li-ion batteries are the current technology
of choice for commercial grid connected
applications for many reasons. First is their
cost, in particular for systems providing shorter
durations of capacity. The capital cost of Liion batteries has fallen dramatically over the
past few years. Second is their high round-trip
efficiency. A Li-ion battery yields more than 80%
of the energy used to charge the resource. Third
is their modularity. Li-ion batteries at the 100
megawatt scale have been deployed at large,
centralized installations, but they have also been
deployed at the kilowatt (kW) scale distributed
in households across the country. Since a Liion battery has essentially no geographical
constraints on where it can be sited and is
modular in size, a utility can strategically site Liion battery storage at a constrained substation
or transmission line, or it can be placed in an
open field near a utility-scale renewable energy
plant.
There are disadvantages to Li-ion batteries,
however. Self-discharge can reduce stored
capacity if the cells are unused for long periods
of time, and batteries also degrade with cycling.
As a result, the useful lifetime of Li-ion batteries
is comparatively shorter than most other grid
infrastructure (i.e., shorter than the 20–30
year life of wind and solar plants). The cells
are composed of thin sheets of conductive
material overlaid with active storage material.
These electrode sheets are typically rolled into
canisters to make a single cell. Large-scale
installations simply arrange these individual
cells into larger racks and containers of cells.
At end-of-life it can be difficult and therefore
expensive to unpack the cells and extract the
active material for recycling. Safety can also be
of concern due to the risk of thermal runaway
sparking a high-energy fire, although Li-ion
chemistries designed for stationary applications
are less volatile than chemistries aimed at
transportation markets.
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