Plug-in electric vehicles (PEVs) have the potential to dramatically
drive down consumption of carbon-based fuels and reduce greenhouse gas
emissions, but the relatively high price of these vehicles — due in
large part to the cost of batteries — has presented a major impediment
to widespread market penetration.
Researchers at the Energy Department's
National Renewable Energy Laboratory (NREL) are playing a crucial role
in identifying battery second use (B2U) strategies capable of offsetting vehicle expenses while improving utility grid stability.
NREL's Jeremy Neubauer measures battery voltage in an
environmental chamber at the Thermal Test Facility. NREL is identifying
battery second use (B2U) strategies capable of offsetting vehicle
expenses while improving utility grid stability. Credit: Dennis
Schroeder.
Lithium-ion (Li-ion) batteries, the energy storage technology of
choice for PEVs, are typically the most expensive components in those
vehicles, and their disposal presents environmental challenges.
Second-use options support a broad spectrum of sustainable energy
strategies, as they increase the potential for widespread PEV adoption
by eliminating end-of-life automotive service costs, in addition to
helping utilities support peak electricity demands while building a
cleaner, more flexible electricity grid. NREL research confirms that
after being used to power a car, a Li-ion battery retains approximately
70 percent of its initial capacity — making its reuse a valuable energy
storage option for electric utilities, before battery materials are
recycled.
"Per the Energy Department's request, we set out to identify the
benefits and viability of B2U strategies, as well as potential
roadblocks," NREL Energy Storage Group Manager Ahmad Pesaran said. "We
not only confirmed that reusing batteries this way is feasible, we found
that it has potential to deliver great benefits to automakers and
utilities, as well as car owners."
NREL researchers Ahmad Pesaran, left, and John Ireland work on a
cell calorimeter at the Battery Testing Laboratory. Credit: Dennis
Schroeder.
Battery Second Use Could Extend Battery Service Life to 25 Years
NREL paired intensive techno-economic analyses with laboratory and
field testing to better understand battery degradation issues, the
ever-evolving world of energy storage, and the true potential costs and
benefits of reuse. This research revealed utility energy storage as the
most promising of possible applications, with a relatively low expense
and abundant battery supply.
"Our analysis showed that B2U is unlikely to significantly reduce the
upfront cost of PEVs, but it will eliminate car owners' end-of-service
costs, like battery disposal or recycling, and could even provide a
credit of as much as $1,000," Pesaran said. "The potential of
integrating B2U energy storage with the electricity grid could be large
with adoption from industry."
Most batteries will become available for second use at the end of the
expected PEV service life of approximately 15 years. NREL studies show
that these batteries can retain as much as 70 percent of their initial
capacity and potentially continue to operate for another 10 years in
second use as energy storage for utilities — translating into a total
service life of up to 25 years. The 25-year estimate is based on a
simulation of 15 years of automotive service, then another 10 years in
second use with a daily 50 percent depth of discharge duty cycle using
NREL's battery degradation life model.
NREL analysis showed regional repurposing facilities specializing
in a single plug-in electric vehicle model could harvest and retrofit
Lithium-ion batteries for second use at relatively low costs.
Credit: Dennis Schroeder.
Collaborating with Partners to Verify Potential of B2U
NREL analysis showed regional repurposing facilities specializing in a
single model of PEV could harvest and retrofit Li-ion batteries for
second use at relatively low costs (less than $500 for today's typical
PEV battery), while avoiding transportation expenses associated with
nationwide battery collection.
Although the supply of second-use batteries has the potential to
overwhelm many high-value markets for energy storage by an order of
magnitude or more, battery reuse by utilities would call for a
large-scale supply capable of absorbing a significant portion of these
components and diverting them from premature recycling or the waste
stream.
Just as PEV batteries are expensive, the utility infrastructure has
finite capacity to meet ever-growing electricity needs, and the majority
of this system is powered by coal and natural gas generators. Energy
storage systems based on reused automotive batteries can increase the
availability of peak-period electricity and store energy during periods
of low demand. These capabilities are expected to become even more
valuable in future facilitation of higher penetrations of solar- and
wind-based generation.
To field test its analysis findings, NREL and the Energy Department
supported establishing the world's first fully integrated energy storage
system consisting of multiple heterogeneous reused vehicle batteries on
the campus of project partner University of California – San Diego
(UCSD). The system is operated by the Center for Sustainable Energy
under both demand charge management and frequency regulation control
algorithms, responding in real time to solar power production and
facility load to reduce peak loads, or to the microgrid frequency to
improve stability. The tests have confirmed that B2U systems can
successfully accomplish both goals. Additional tests of the nature of
battery wear under similar conditions in NREL laboratories suggest that
B2U system degradation will be slow, indicative of a long second-use
service life.
"We used batteries from two different manufacturers with distinct
designs, characteristics, management systems, voltages, and capacities,"
said Mike Ferry of the Center for Sustainable Energy. "Even with these
variables, the system has been operating successfully since late 2013."
Other NREL B2U research partners include utilities (San Diego Gas
& Electric and Southern California Edison), universities (UC Davis
and UC Berkeley), hardware developers (AeroVironment), energy agencies
(California Energy Commission), and automakers (BMW).
What Does This Mean for Automakers, Utility Operators, and Car Owners?
It is estimated that a critical mass of used PEV batteries will
become available beginning in 2030. That gives automakers and utility
operators 15 years to develop new strategies to ensure reliability,
compatibility, cost, and market acceptance.
The NREL team's findings indicate that the economic margins that make
B2U viable can be small, calling for further data collection through
onboard diagnostics and accurate assessments of battery degradation in
original and secondary applications. Installation of onboard diagnostic
technology by automotive and battery manufacturers would make it
possible to track a battery's overall health and degradation issues and
accurately identify value and viability for different second-use
services. Affordable, megawatt-scale systems based on repurposed
batteries and new utility policies and guidelines will be needed to
smooth the transition to replacement of peak-power plants with
second-use technologies.
"If these recommendations are implemented, it is likely that B2U
could become an important part of both the auto and electricity
industries—as well as deliver meaningful reductions in greenhouse gas
emissions and fossil fuel consumption," Pesaran said. This project was funded by the Vehicle Technologies Office of the
Energy Department's Office of Energy Efficiency and Renewable Energy.
http://www.renewableenergyworld.com/articles/2015/06/battery-second-use-offsets-electric-vehicle-expenses-improves-grid-stability.html