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.

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1.5 Hour Event 2 Second Resolution

S t a t e o f C h a r g e



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.

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July 23

P o w e r ( k W )

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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.



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®

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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

[email protected]

www.altairnano.com

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