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8/12/2019 Applications for Advanced Batteries Wp
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Applications for Advanced
Batteries in Microgrid Environments
WHITE PAPER
Dec. 12, 2
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Demands for high performance battery solutions are
expected to accelerate the adoption of renewable energy
resources. This is especially true for microgrids. Microgrids
are attractive settings for wind turbines and photovoltaic
panels. But, susceptibility to wind spikes, lulls, and rolling
clouds can lead to significant frequency variations and
voltage drops. Beyond concerns over equipment damage of
traditional generation assets, the intermittency associated
with renewable generation increases maintenance and
fuel costs. As a result, microgrids are well-positioned to
benefit from battery-based storage systems for maintaining
reliability and power quality.
Efficient Storage is Critical
Traditional lead-acid battery systems have been tried,
but performance limitations, short life cycles, and high
maintenance demands have limited their adoption. However,
breakthroughs in a new generation of lithium-based battery
storage devices are entering the market, and one company,
Altairnano, has advanced the technology a step further by
replacing traditional graphite materials used in conventional
lithium-ion batteries with a proprietary, nanostructured
lithium-titanate.
Efficient storage is critical because microgrids or onsitegeneration systems with “islanding” capabilities can operate
without being connected to a utility grid, says Mariesa Crow,
Ph.D., P.E., director, Energy Research and Development
Center, Missouri University of Science and Technology.
“Any time you have a reliance on renewable energy or
intermittent energy without a grid tie you have to have some
sort of storage,” Crow explains. “Lead acid batteries are
extremely well-known but do have issues. They are toxic and
very heavy, and they require maintenance. Another issue is
environmental impact and sustainability.”
Lithium-based batteries offer many advantages to answer
Crow’s performance issues. They are safer because they
don’t suffer from hydrogen gas leakage or degrade fromexposure to sulfuric acid. Lower weight and volume ratios
compared to power output are additional benefits. The latest
breakthrough in lithium-titanate technology offers a rugged
battery with high power, fast charge and discharge rates, and
long life, plus a superior power to weight ratio over lithium-
ion based predecessors.
What About Efficiency?
“One of the biggest issues with microgrids is the loss of
efficiency when changing the form of energy,” says Crow.
“So you need a good roundtrip efficiency factor.” Lithium-
titanate batteries offer an impressive average efficiency
that surpasses 90% total roundtrip efficiency (including
power conversion system) for a 1 MW dispatch. At a 250
kW dispatch, roundtrip efficiency rises to 93%. Moreover,
their performance is ideal for mitigating the impact of high
diesel fuel consumption in microgrid situations.
In an era of record-high oil prices, diesel fuel costs have
placed significant burdens on electricity providers, but the
implications can be staggering for remote villages, such
as Kotzebue, Alaska. Located north of the Arctic Circle,Kotzebue’s 3,000 residents depend on diesel generators
plus an array of wind turbines to supply a load that
averages 2.5 MW.
“We buy an annual supply of 2.15 million gallons of
fuel,” says Brad Reeve, general manager of the Kotzebue
Electric Association. “That isn’t our total consumption
but it’s what we need in order to carry the prior year’s fuel
and also to get a year’s supply plus four months backup.”
In 1997, Kotzebue installed its first wind turbine in an
effort to reduce diesel consumption. At this point, it hasinstalled 17 wind turbines that can produce a maximum
of 1.1 MW. Power quality fluctuations occur, but aren’t
disruptive because the diesels handle the majority of the
load. Future plans call for a change to the role of the wind
turbines, and Reeve is anticipating power quality issues
that require a solution.
“Efficient storage is critical
because microgrids or onsitegeneration systems with
‘islanding’ capabilities can
operate without being connected
to a utility grid.”
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“When we add another 1.8 MW of wind equipment we’ll be
in high penetration so we’re looking at some battery storage
as part of the equation,” says Reeve. “Storage is key for a lot
of these island grid installations like ours in maintaining our
power quality. If you have batteries they can buffer against
low and high wind problems, and when you get a low load
you can run the diesels at their sweet spot in efficiency and
use the storage to avoid having to turn on a peaking unit.”
Reeve estimates that batteries could provide ride through
during fluctuations and avoid about 300 engine starts
per year, resulting in savings of 150,000 gallons of fuel.
Ultimately, Reeve says the goal is to reverse the role of the
wind turbines and the diesels, so the wind turbines and
storage working together supply the base load requirements.
With wind power supporting a large portion of the load,
it’s not unusual for diesel engines to struggle to controlfrequency, voltage and reactive power, according to E. Ian
Baring-Gould, senior mechanical engineer at the National
Renewable Energy Laboratory’s (NREL) Wind Technology
Center. Baring-Gould has been involved closely with the
development of wind power at a number of Alaskan villages,
and he notes that problems often occur when wind surges
and voltage spikes cause diesel engines to power down and
operate below their minimum load ratings.
Running diesels (especially older models) at levels under
40% to 50% of minimum load can raise emissions, and
reduced load levels can force engines to run at cooler
temperatures. Ensuing problems are increased engine
carbon build up, wet stacking, and higher maintenance
requirements. Obviously it’s beneficial to shut down as many
“Any time you have a relianceon renewable energy or
intermittent energy without a
grid tie, you have to have some
sort of storage.”
ACTUAL WIND FARM OUTPUT-SMOOTHING POTENTIAL BY ALTAIRNANO LITHIUM-TITANATE BATTERY STORAGE
Figure 1 Actual wind data for the Apollo Wind Farm provided by the Hawaiian Electric Light Company reflects variability of wind output
using two-second resolution over a two-hour period. The blue line reflects wind output. The magenta line reflects the smoothing capabilities
of a 1MW Altairnano Energy Storage System (ALTI-ESS), using a control algorithm developed by HOMER, LLC. It is anticipated the
smoothing of output would reduce wear and tear on generation equipment and result in an overall reduction in the ramping requirements.
16,500
15,500
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9,500
200%
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20%
0%1 6
7 1 3 3
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M W s
1.5 Hour Event 2 Second Resolution
S t a t e o f C h a r g e
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fuel consuming engines as possible as renewable resources
supply more of the load, but fast response storage is needed
to give the diesels time to restart when the output of those
renewable resources falls.
“Diesels with storage batteries allow you to supply some
buffering until you can start another diesel in a controlled
fashion,” says Baring-Gould. “In most cases, the optimal
runtime and ridethrough is five minutes, but of course it
depends on load characteristics. You want to have leeway
and avoid using the engine when you don’t really need it for
a short fluctuation.” The charge/discharge capability and
high cycle life of a lithium-titanate battery can provide an
ideal solution to these ride-through needs.
For example, within milliseconds, the Altairnano Energy
Storage System provides up to 1 MW of instantaneous
dispatch for 15 minutes per module, and importantly,
recharging the battery takes just 15 minutes. Such
performance would result in a reduced life cycle for
traditional battery technologies, but with a conservative
12,000-plus cycle life (full depth of discharge), this product
has an estimated life of 20 years. For many microgrid
applications, the duty cycle isn’t going to require a full
depth of discharge. The shallower the charge and discharge,
the greater the cycle life.
Photovoltaics and Microgrids
Photovoltaic solar panels aren’t seeing much uptake in
northern climates such as Alaska, but their popularity
is growing elsewhere, and they share much of the same
intermittency characteristics of wind. The Department of
Energy has taken notice and issued warnings about problems
such as, “… voltage rise, cloud-induced voltage regulation
issues, and transient problems caused by mass tripping of
PV during low voltage or frequency events.”
“In part, photovoltaics have problems because they are
subject to the IEEE 1547 interface guidelines,” says Robert
Lasseter, Emeritus Professor at the University of Wisconsin’s
Department of Electrical and Computer Engineering, and
site director of the Power Systems Engineering Research
“The latest breakthrough in
lithium-titanate technology offers
a rugged battery with high power,
fast charge, and discharge rates
and long life.”
Figure 2 Using actual solar data forthe island of Lanai available from
National Renewable Energy Lab
(NREL), Altairnano and HOMER
Energy accurately modeled PVoutput in one-minute intervals,
which would be anticipated for
the island of Lanai on July 23,2009 and a 1.2 MW PV solar array.
The yellow line represents the
output from the PV array for eachminute of the day. The blue line
represents the target output for the
Altairnano Energy Storage Systemover each 30-minute time step.
Modeling reflects the smoothing
characteristics of an Altairnano
Energy Storage System.
1,200
900
600
300
0
July 23
P o w e r ( k W )
0 6 12 18 24
AC Primary Load
PV Power
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Center, a multiuniversity center focused on the restructuring
of the electric power industry. The IEEE 1547 set of
standards governs connecting small sources of energy to
the distribution system, and it causes PV systems to shut
down during voltage drops or frequency fluctuations. A
microgrid can disconnect or “island” from the utility grid
when photovoltaics react to these problems, but because
the disconnection removes the stabilizing reserve offered by
the utility grid, storage is needed to smooth out and absorb
excess load, or supply power to compensate for drops in
voltage. “If you have bigger generators that don’t respond
as fast, you want storage to take things up and balance the
load,” says Lasseter.
Additionally, Lasseter notes that microgrids with fuel cells
are experiencing problems similar to those of photovoltaics.
He was recently involved in a distributed energy project at a
correctional institution in California, where the distributed
generation employed 2 MW of photovoltaic panels and a1 MW fuel cell. “The fuel cell trips off any time there are
fluctuations in the grid,” Lasseter explains. “We are going
to install large storage [batteries], and the ability to “island”
in half a cycle. In that case we’re relying on the storage to
make up all the energy differences instantaneously.”
Mitigating Intermittency on the
Hawaiian Island of Lanai
Batteries have also been chosen to solve energy fluctuation
problems at a new solar farm on the Hawaiian island of
Lanai. The project’s location and weather-related solar
intermittency offer an ideal environment to compare the
performance of Valve Regulated Lead Acid (VRLA) batteries
against lithium-titanate.
The project is a $19 million, 1.5 MW photovoltaic solar
farm, occupying about 10 acres in the Palawai Basin,
just two miles from the island’s diesel generation facility
operated by the Maui Electric Company. The facility supplies
10.4 MW from 8 diesel units, and will continue to operate
with expectations of the 1.5 MW plant supplying up to 30%
of peak demand on Lanai. An integrated battery systemcould smooth out voltage spikes and drops, and provide
short-term storage.
Such spikes and related problems have become a critical
issue for Maui Electric. The company has had problems with
power outages on the islands of Oahu and Maui, and is still
searching for adequate methods of buffering fluctuations
in power coming from their Kaheawa wind energy project.
The short-term solution has been less than cost-effective—
access to the power has been limited to an average of one
third of the 30 MW the wind is capable of producing.
Those same wind fluctuations will contribute to cloud
conditions that make Lanai an ideal laboratory for studying
solar energy fluctuations, and also an ideal site for
determining the most cost-effective technology for a battery
buffering system. Peter Lilienthal, former NREL microgrid
optimization expert and now the CEO of HOMER Energy,
utilized a life cycle analysis approach to study the costs
and performance factors between traditional VRLA batteries
versus lithium-titanate batteries.
The study used solar data for Lanai from July 20 through
August 23, gathered from NREL, to get an accurate picture
of typical cloud patterns over a month’s time. The data
revealed significant fluctuations in solar radiation. There
were 2,000 ramp events per year where the PV output
changed by more than 500 kW from one minute to the next,
and 53 ramp events where the PV output changed by more
than 800 kW. Each of these represents one or more power
quality events where voltage and/or frequency move out of
spec, leading to generator stress, higher maintenance and
fuel costs, and stress on the battery that will reduce its life.
To model the VRLA battery performance, characteristics
were based upon the units cycling 1,200 times to an
80% depth of discharge. The lithium-titanate batteryspecifications were based upon cycling 15,000 times to a
100% depth of discharge.
Neither battery could make the combined PV-battery output
perfectly smooth on every day of the year, but the Altairnano
battery came much closer than the lead acid battery while
A microgrid can disconnect or
“island” from the utility grid when
photovoltaics react to problems.
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delivering more energy to the utility. During energy spikes,
the lead acid battery was stressed to its limits and such
events typically result in a reduced lifetime. The cycle life of
the Altairnano battery far exceeds the amount of cycling that
it would experience during 20 years in this application.
The analysis showed that on average, the lead acid batterywould deliver 4,350 kWh per day, while the Altairnano
battery would deliver 4,600 kWh per day. The difference
amounts to 91,250 kWh per year plus an additional 7,306
kWh per year of unserved energy from the lead acid battery.
Ultimately, the lithium-titanate battery is more effective in
smoothing output because its design is better suited to the
high rates of charge and discharge in this application. It
delivers significantly higher kWh to the utility because its
higher efficiency incurs fewer losses. Finally, the 20-year
shelf life is not reduced due to cycle wear, yet the lead acid
battery is only estimated to last 7.9 years in this particular
application. This was considered a best case life expectancy,
as the repeated battery life shortening stress events were not
factored into the life expectancy.
With its high performance, modular scalability, and extended
lifetime, Altairnano’s application of lithium-titanate
technology offers an ideal solution to power stability in
microgrid applications that use renewable energy. But is it
price competitive in today’s market? In an environment such
as the Lanai solar farm or other isolated grid environments,
the Altairnano battery demonstrates the lowest life cycle
cost by a significant margin. And though each situationwill be different, the evaluation methods employed using
data associated with Lanai are applicable for helping to
determine the true economic value of Altairnano’s storage
capabilities for power management.
The lithium-titanate battery
specifications were based upon
cycling 15,000 times to a 100%
depth of discharge.
FREQUENCY OF CHARGES IN PV POWER OVER 1 MINUTE
Figure 3 Using PV output modeledfor the island of Lanai, the graphic
reflects the frequency of rampingevents as a function of the changefrom one minute to the next. Thecenter gap includes smaller, butmore common, ramp events, notsupported by the “smoothing”capabilities of an Altairnano EnergyStorage System. Since there are525,600 minutes in a year, 0.1%represents 526 events per year.Although it sounds small on apercentage basis, there were stillover 2,000 ramp events per yearwhere the PV output changed bymore than 500 kW from one minuteto the next and 53 ramp events
where the PV output changed bymore than 800 kW.- Graph produced by HOMER®
0.8
0.6
0.4
0.2
0
Change in PV Power (kW)
F r e q u e n c y ( % )
-1,200 -600 0 600 1,200
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About Altairnano
Current as of 12.12.2012
Note that all specifications, product descriptions, standards and other technical documentation are subject to change at any time and cannot be guaranteed accurateas of this printing. 2012 by Altairnano. Altair Nanotechnologies Inc.® and Altairnano® are registered trademarks of Altair Nanotechnologies, Inc.
Altairnano is a leading provider of energy storage
systems for clean, efficient power and energy
management. Designed for power-dependent
applications, Altairnano’s family of advanced
lithium-ion energy storage systems and batteries
is responding to changing demands in energy
generation, utilization and policy. Whether
it’s reducing our dependencies on coal-fired
generation facilities, reducing carbon emissions or
accelerating the adoption of renewable integrationand alternative-fuel vehicles, Altairnano is helping
to achieve sustainable and economically sensible
power and energy management practices.
Altairnano is headquartered in Anderson, Ind., where it
operates a 70,000-square-foot manufacturing facility.
Altairnano’s technical team comprises scientists,
engineers and real-world business professionals.
With proprietary technologies, proven market
acceptance and production scalability, Altairnano is
uniquely positioned to help solve the challenges and
opportunities of an energy-focused economy.
For more information:
+1.888.218.4005
www.altairnano.com