systems for freq regulation

Advanced Energy Storage Systems for Frequency Regulation

WHITE PAPER

Dec. 12, 2012

2 Advanced Energy Storage Systems for Frequency Regulation

THE AES CASE STUDY

Advanced Batteries Supply Ancillary Services

For the power engineer, delivering an instantaneous and

consistent power supply can be an elusive goal. Yet without

it, grid frequency regulation is impossible. Today, frequency

regulation is an ancillary service bought by the hour, the

day prior to utilization. It is then dispensed on an as-

needed basis by dispatch communiqus and provided by

the ancillary service provider on a 15-minute basis.

Sounds complicated, and it is. Wear and tear on generation

equipment, conflicting dispatch signals with varying loads

and wasted fuel are all part of the current implementation

of this ancillary service.

Altair Nanotechnologies (Altairnano), based in Anderson,

Ind., has developed a lithium-titanate energy storage

system to mitigate some of these ancillary services

difficulties. The Altairnano Energy Storage System (ALTI-

ESS) provides frequency regulation on a 1-second dispatch

basis, as needed.

AES Energy Storage LLC is a subsidiary of the AES

Corporation. As one of the worlds largest power companies,

AES Corporation supports operations in 29 countries,

including more than 120 power facilities and 12 million

distribution customers. Together, AES Corporation and

Altairnano have a joint development agreement to create

grid-scale energy storage applications.

With AES Energy Storage LLC, Altairnano developed a 2

MW, 500 kWh system with the capability of producing

1,000 amps at 1,000 volts. The system comprises two

individual 1 MW, 250 kWh battery configurations housed

in 53-foot trailers. The Altairnano battery system was

pilot-tested at Indianapolis Power & Light by AES Energy

Storage LLC. KEMA (a global strategic and technical

energy consultancy) served as the test contractor, providing

independent third-party analysis.

LITHIUM-ION BATTERY CONSTRUCTION NANO-TITANATE BATTERY CONSTRUCTION

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Figure 1 Battery technology comparison: A comparison configuration of a typical lithium-ion battery with a lithium-titanate battery. Source: Altairnano

These batteries work very efficiently in extreme temperatures and operate with a wider temperature range than other technologies.

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New Technology for Power and Energy Management

The lithium-titanate battery system exhibits three times the

power capabilities of existing batteries and can be described

as the combination of a battery and a supercapacitor.

This means power can be extracted from, as well as

inserted into, the battery at symmetrical rates, making the

technology ideal for Smart Grid applications. Altairnanos

lithium-titanate technology is also unique because it lacks a

solid electrolyte interface (SEI), as shown in Figure 1.

The SEI is a film on the anode that is an internal resistor

that limits power output and generates heat build-up in

a standard lithium-ion battery. Therefore, the lack of an

SEI allows the lithium-titanate battery to work efficiently

in extreme temperatures and significantly reduces thermal

runaway risk. This batterys operating temperature range

also is wider than that of other technologies: from -40C to

55C (-40F to 131F). This capability virtually eliminates

the need for supplemental heating when the battery is used

in low temperature environments and reduces or eliminates

cooling requirements for high temperature operation.

Inside the 53-foot trailer (Figure 2) reside numerous

lithium-titanate Line Replaceable Unit (LRU) battery

units installed in racks (Figure 3). The batteries are air-

cooled (the black circles in Figure 3 are the fans) in order

to compensate for I2R heating in the modules. An air-

conditioning system for the trailer keeps the temperature

below 55C (131F).

Various computer systems monitor and control the LRUs

and associated systems. A battery management system

monitors battery cell temperature, balances the cell voltages

as needed and keeps track of the battery charge state. A

programmable logic controller interfaces with three parallel

three-phase Parker Hannifin SSD inverters. The A/C side

of the power inverters operate at 480 V. Then after passing

through isolation transformers, the voltage is stepped up to

the substations 13.8 kV distribution bus. The energy storage

system is monitored by a supervisory control system that

interfaces with the utility regulation signal and controls the

sending and receiving of power to and from the grid.

Independent Test Results Technical Validation for Frequency Regulation

KEMA put the Altairnano system through three sets of tests

for the validation study:

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The AES Energy Storage LLC pilot test at Indianapolis Power

& Light is considered a significant success in the application

of advanced energy storage devices for frequency regulation.

According to KEMA, the prototype units in their current state

are suitable for use in future market pilot activities designed

to help better define the application requirements and

demonstrate the potential of this technology.

Figure 2 Batteries on wheels. The Altairnano/AES 1 MW system can produce 250 kWh and is contained within a single 53-foot trailer.

Figure 3 Modular arrangement. The batteries are arranged in racks within the trailer along with air-cooled fans, air conditioning and various

computer monitoring systems and controls.

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4 Advanced Energy Storage Systems for Frequency Regulation

The KEMA report observed that a key performance finding

was the maximum unit storage capacity for each of the two

1 megawatt systems was approximately 300 amp-hours with

a capacity of delivery of 250 kWh at a rated output of 1,000

kW for 15 minutes. Each unit was able to dispatch at any

power level between 1 MW discharge to 1 MW charge within

one second. Due to the battery and inverter technology used,

response actually occurs within cycles.

The round-trip efficiencies are on the high end of various

options, with total efficiencies ranging from 95 percent

to 88 percent depending upon the dispatch signal. Other

systems that have a 60 percent to 70 percent round-trip

efficiency cannot provide the required economics when the

losses are included in the value calculations.

Commercial Operation

Following technical validation, one of Altairnanos

megawatt systems used in Indianapolis Power & Lights

demonstration met requirements to participate in the PJM

Regional Transmission Organization (RTO) control area. PJM

Interconnection is an RTO that coordinates the movement

of wholesale electricity in 13 states and the District of

Columbia, serving approximately 51 million people.

In November 2008, the milestone marked the first

commercial acceptance of an advanced lithium-titanate

battery to provide grid regulation services in one of the

largest electricity markets in the United States. Today, the

unit is available for commercial operation as a qualified

market participant for regulation service and is operating

continuously, 24 hours a day, generating revenue for AES

Energy Storage LLC.

Altairnanos advanced lithium-titanate battery technology is

helping AES Energy Storage LLC address the power markets

need for energy-efficient solutions that provide grid stability

and help increase the adoption of renewable generating

resources, such as solar and wind.

Open power markets, like the PJM Interconnection, value

grid stability services and encourage the deployment of new

technologies to efficiently serve these needs. By completing

the requirements to compete in the PJM RTO, Altairnano is

enabling energy storage technologies that can help to make

the electric grid smarter and more responsive.

Lithium-titanate battery systems exhibit three times the power capabilities of existing batteries.

systems for freq regulation

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