ESA TR 8 09 Capture Grid Power Roberts

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2 IEEEpower & energy magazine july/august 2009

CapturingGrid Power

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july/august 2009 IEEEpower & energy magazine 33

Performance, Purpose,and Promise of DifferentStorage Technologies

By Bradford Roberts

MMAKING ELECTRICITY GRIDS SMARTER AND MODERNIZING THEM SO

that they can accept large amounts of renewable energy resources are fairly universallyaccepted as steps necessary to achieve a clean and secure electric power industry. The

best way to achieve this goal is a topic of debate among power system designers. Although

energy storage in utility grids has existed for many decades, the impact of storage in

future grids is receiving more attention than ever from system designers, grid operations

and regulators. The amount of storage in a grid and its value is also a subject of debate.

Understanding the leading storage technologies and how they can affect grid operations is

an important first step in this assessment.

Why Storage in the Grid?In April 2003, the U.S. Department of Energy convened a meeting of 65 senior executives

representing the electric utility industry, equipment manufacturers, information technol-

ogy providers, federal and state government agencies, interest groups, universities, and

national laboratories. They gathered to discuss the future of the North American electrical

system. The goal of the meeting was to establish Grid 2030, a national vision for elec-

tricitys second 100 years. From that meeting, energy storage emerged as one of the top

five concerns for the future grid. And since that meeting, more attention has been given

to storage in the grid at all levels, from large-scale bulk-storage systems to small units at

or near the point of load. Other nations are ahead of the United States with regard to bulk

storages; they recognized the value to grid operations sooner. The future of electric grids

will be impacted by a growing penetration of plug-in hybrid electric vehicles (PHEVs) and

electric vehicles (EVs), which will represent a new dimension for grid management; vast

amounts of energy storage will be present in the grid in the form of millions of electric

cars. Gigawatts to kilowatts, electricity storage devices will change the grid dramatically.

Spectrum of Electricity StorageIn industrialized countries, nearly every person depends on some form of energy storage

everyday. Every electronic device depends on battery power to function properly; think

of your cell phone or laptop computer. These storage energy devices continue to evolve

as newer applications are introduced. One application that is having a great impact on

potential utility grid applications is electric cars. The technologies that have worked in

electronic devices are being scaled up for higher power use in cars and the electric grid.

Figure 1 shows a storage technology chart published by the Electr icity Storage Associa-

tion (ESA) that shows various technologies in terms of total power (kW) and energy

capacity (time).

Digital Object Identifier 10.1109/MPE .2009.932876


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Power applications, such as uninterruptible power

supply (UPS) backup for dat a centers and automotive

starting batteries, represent the largest market for lead-

acid batteries, whereas laptop batteries and power tools

have fueled incredible growth for lithium-ion. For

bulk energy storage in utility grids, pumped hydro

power plants dominate, with

approximately 100 GW in service

around the globe.

In general terms, power appli-

cations would be storage systems

rated for one hour or less, and

energy applications would be forlonger periods. The chart in Fig-

ure 2 shows the positioning of en-

ergy storage options by application

(power level) and storage time.

Potential applications of each

of these technologies are being

found in the electric gridin

the transmission system for bulk

storage, in the residential feeder

circuit for smaller systems.

The location in the grid will

vary based on the economics ofthe technology.

Wise Investmentsin the PastUtility system designers have seen

the benefits of massive amounts

of energy storage in the form of

pumped hydro power plants.

A typical pumped hydro plant consists of two interconnected

reservoirs (lakes), tunnels that convey water from one reservoir

to another, valves, hydro machinery (a water pump-turbine),

a motor-generator, transformers, a transmission switchyard,

and a transmission connection (Figure 3). The product of the

total volume of water and the differential height between

reservoirs is proportional to the

amount of stored electricity. Thus,

storing 1,000 MWh (deliverable in

a system with an elevation change

of 300 m) requires a water volume

of about 1.4 million m3.

The earliest known use of

pumped hydro technology was in

Zurich, Switzerland, in 1882. For

nearly a decade, a pump and tur-

bine operated with a small reservoir

as a hydromechanical storage sys-

tem. Beginning in the early 1900s,

several small hydroelectric pumped

storage plants were constructed in

Europe, mostly in Germany. The

first unit in North America was

the Rocky River pumped storage

plant, constructed in 1929 on the

Housatonic River in Connecticut.

Most of these early units wererelatively expensive since they had

VR

Zn-Br

Na-SCAES

PSH

L/A

Ni-Cd

FW

Na-S

EDLC

Ni-MH

Li-lon

System RatingsInstalled Systems as of November 2008

100

10

1

0.1

0.01

0.001

DischargeTime(h)

0.00010.001 0.01 0.1 1

Rated Power (MW)10 100 1,000 10,000

CAES Compressed AirEDLC Dbl-Layer Capacitors

FW Flywheels

L/A Lead-Acid

Li-lon Lithium-Ion

Na-S Sodium-Sulfur

Ni-Cd Nickel-CadmiumNi-MH Nickel-Metal Hydride

PSH Pumped Hydro

VR Vanadium Redox

Zn-Br Zinc-Bromine

figure 1. Electricity storage by technology.

figure 2. Storage technology application comparison.

Positioning of Energy Storage Options

UPS

Power Quality

Grid Support

Bridging Power

Energy Management

Bulk Power Management

Metal-Air Batteries Flow Batteries

ZrBr VRB PSB Novel SystemsPumped

Hydro

CAESNaS Battery

ZEBRA BatteryHigh-EnergySuper Caps

Li-Lon Battery

Lead-Acid Battery

NiCd

NiMH

High-Power Fly Wheels

High-Power Super Caps

1 kW 10 kW 100 kW

System Power Ratings

Seconds

Minutes

Hours

DischargeTimeatRatedPower

1 MW 10 MW 100 MW 1 GW

SMES

Advanced LeadAcid Battery

Load Shifting

2008 Electric Power Research Institute, Inc. All rights reserved.c


4/10


a motor and pump on one shaft and a separate shaft with a

generator and turbine. Subsequent developments through the

middle of the 20th century typically used a tandem system

with a single vertical shaft that had a motor-generator at the

top, above a pump, and a turbine at the bottom. Whereas

some of the earliest units used propellers, both the pump

and the turbine in these later developments were usually of

the Francis type, which uses flow inlet converted to axial

flow outlet. Wicket gates, eventually under hydraulic

control, regulated the power level. An advantage of the Fran-cis turbine shape is high efficiency, but in this configuration,

it operates best with a very limited head range.

It was realized early on that a Francis turbine could also

operate as a pump, but it was not used for both purposes until

the Tennessee Valley Authority (TVA) and Allis-Chalmers

constructed the Hiwassee Dam Unite 2 in 1956. This unit

was a true reversible pump-turbine and, at 59.5 MW, it was

larger than earlier installations. Developments in technology

and materials over the next three decades improved overall

efficiency, reduced start-up issues, and allowed larger and

larger units to be constructed.

The next major breakthrough, the variable speed

design, was developed mainly in Japan. In most of the early

designs, the only knob available to the operator was water

flow, which was controlled by moving the wicker gates, but

in th is design, an adjustable-speed motor-generator allows

the shaft rotation rate to change as well. By optimizing

the two variables, the unit can be dispatched at optimum

efficiency over a large power range. The first adjustable-

speed system unit was constructed for use in Japan and

became operational in 1990. Recently, an adjustable-speed

system was constructed at Goldisthal in Thuringia, Ger-

many. Two of the four 265-MW units at this plant are ad-

justable speed.

Today, the global capacity of pumped hydro storage

plants totals more than 95 GW, with approximately 20

GW operating in the United States. The original intent

of these plants was to provide off-peak base loading for

large coal and nuclear plants to optimize their overall

performance and provide peaking energy each day. Their

duty has since been expanded to include providing an-

cillary service functions, such as frequency regulation in

the generation mode. The newer adjustable-speed system

design allows pumped hydro plants to provide ancillary

service (frequency) capability in the pumping mode aswell, which increases overall plant efficiency. Filings with

the Federal Energy Regulatory Commission (FERC) have

been made for additional pumped hydro facilities. These

new plants represent 20 GW of new storage capacity that

could be added to the U.S. grid.

Compressed Air Energy StorageCompressed air energy storage (CAES) is a peaking gas

turbine power plant that consumes less than 40% of the

gas used in a combined-cycle gas turbine (and 60% less gas

than is used by a single-cycle gas turbine) to produce thesame amount of electric output power. This is accomplished

by blending compressed air to the input fuel to the turbine.

By compressing air during off-peak periods when energy

prices are very low, the plants output can produce electricity

during peak periods at lower costs than conventional stand-

alone gas turbines can achieve.

Making the CAES concept work depends on locat-

ing plants near appropriate underground geological

formations, such as mines, salt caverns, or depleted gas

wells. The first commercial CAES plant was a 290-MW

unit built in Handorf, Germany, in 1978, and the second

commercial site was a 110-MW unit built in McIntosh,

Alabama, in 1991. These units are fast-acting plants and

typically can be in service in 15 min when called upon for

power. The plants used a fairly complex turbomachinery

design integrated with a combined motor-generator and

custom components.

Today, the Electric Power Research Institute (EPRI) has

an advanced CAES program designed around a simpler

figure 3. Typical pumped hydroelectric storage plant.

Pumped Storage

Reservoir

Elevator

Access Tunnel

Generator

Surge Chamber

U.S. Capacity 22,000 MWWorlds Capacity 110,000 MW

7085% Efficient

All of the energy storage technologies discussed are targeting waysto help the utility grid cope with balancing generation and loadin the most optimal ways possible.


5/10


system using advanced turbine technology. Figure 4 shows a

basic diagram of an advanced CAES design.

This proposed concept is targeted at plants in the 150

400 MW range with underground storage reservoirs of up

to 10 hours of compressed air at 1,500 lbf/in2. Depend-

ing on the reservoir size, multiple units could be deployed.

The largest plant under consideration in the United States

would have an initial rating of

800 MW. In addition to these

larger plants, EPRI has been

studying an aboveground CAES

alternative with high-pressure air

stored in a series of large pipes.

These smaller systems are target-ed at ratings of up to 15 MW for

two hours.

Battery Energy StorageAdvancements in battery tech-

nology over the last 20 years

have been driven primarily by

the use of batteries in consumer

electronics and power tools.

Only in the last ten yearswith

efforts to design better batteries

for transportationhave pos-sible uses of battery technology

for the power grid emerged. One

driver that has helped make potential utility applications

possible is more efficient cost-effective power electron-

ics. For battery technologies to be practically applied

in the ac utility grid, reliable power conversion systems

(PCSs) that convert battery dc power to ac were needed.

These devices now exist and have many years of service

experience, which makes a wide range of battery tech-

nologies practical for grid sup-

port applications.

Figure 5 shows the steady in-

crease in the energy density of

batteries since the first lead-acid

batteries were introduced in the

mid-19th century.

A large variety of battery

types are being used for grid sup-

port applications.

Sodium Sulfur BatteriesThe sodium sulfur (NaS) battery

is a high-temperature battery sys-

tem that consists of a liquid (mol-

ten) sulfur positive electrode and a

molten sodium negative electrode

separated by a solid beta alumina

ceramic electrolyte (Figure 6). The

electrolyte allows only positive

sodium ions to pass through it and

combine with the sulfur to form

sodium polysulfides.

During discharge, positive

sodium ions flow through the

electrolyte and electrons flowin the external circuit of the

CT Module

CompressorAir

Air

Fuel

Combustion Turbine

Expander

Recuperator

Constant Output Pressure Regulation Valve

Storage

Source: EPRI

Motor

Intercoolers

Heat RateEnergy Ratio

38100.70

2008 Electric Power Research Institute, Inc. All rights reserved.

Exhaust

c

figure 4. Advanced CAES one-line diagram.

Lead-Acid2545 Wh/kg

Nickel-Iron3040 Wh/kg

Nickel-Cadmium3560 Wh/kg

Nickel-Metal Hydride5075 Wh/kg

Lithium Ion110140 Wh/kg

1860 1910 1960 2010

Time of First Introduction

Exponential Improvement in Performance

SpecificEnergy

c 2008 Electric Power Research Institute, Inc. All rights reserved.

figure 5. Exponential improvement in battery performance.


6/10


battery, producing about 2 V.

This process is reversible since

charging causes sodium poly-

sulfides to release the positive

sodium ions back through the

electrolyte to recombine as

elemental sodium. The batteryoperates at about 300 C. NaS

battery cells are efficient (about

89%). This battery system is

capable of six hours of dis-

charge time on a daily basis.

NaS battery technology was

origina lly developed in the 1960s

for use in early electric cars, but

was later abandoned for that ap-

plication. NaS battery technol-

ogy for large-scale applications

was perfected in Japan. Current-ly, there are 190 battery systems

in service in Japan, totaling more

than 270 MW of capacity with

stored energy suitable for six hours of daily peak shaving.

The largest single NaS battery installation is a 34-MW,

245-MWh system for wind power stabilization in northern

Japan (Figure 7). The battery will allow the output of the

51-MW wind farm to be 100% dispatchable during on-

peak periods.

In the United States, utilities have deployed 9 MW of

NaS batteries for peak shaving, backup power, firming wind

capacity, and other applications.

Another high-temperature battery, which is based

on sodium nickel chloride chemistry, is used for elec-

tric transportation applications in Europe. Known as the

Zebra battery, it is being considered for utility applica-

tions as well.

Flow Battery TechnologyFlow batteries perform similarly to a hydrogen fuel cell.

They employ electrolyte liquids flowing through a cell

stack with ion exchange through a microporous mem-

brane to generate an electrical charge. Several different

chemistries have been developed for use in util ity power

applications. An advantage of flow battery designs is the

ability to scale systems independently in terms of power

and energy. More cell stacks allows for an increase in

power rating; a greater volume of electrolytes translates

to more runtime. Plus, flow batteries operate at ambient

(rather than h igh) temperature levels.

Zinc-bromine flow batteries are being used for utility

applications. The battery functions with a solution of zinc

bromide salt dissolved in water and stored in two tanks.

The battery is charged or discharged by pumping the elec-

trolytes through a reactor cell. During the charging cycle,metallic zinc from the electrolyte solution is plated onto

the negative electrode surface of the reactor cell, as shown

in Figure 8.

The bromide is converted to bromine at the positive

surface of the electrode in the reactor cell and then is stored

in the other electrolyte tank as a safe chemically complex

oily liquid. To discharge the battery, the process is reversed,

50 kW, 6 h Module ThermalEnclosure

Thermal Enclosure

Cell

Sketch of a 2 V NAS Battery Cell

Sulfur

S

Na2S4

Na+

MoltenNa

2 VBeta

AluminaTube

Discharge

+

Sodium Sulfur Battery - NAS

+

2 V Cell

NA+ Exchange89% Efficient

2,500 Cycle Life

Terminals

figure 6. NaS battery cell construction.

figure 7. A 34-MW, 245-MWh NaS battery installation.

PorousSeparatorBromineElectrode

Pump

Valve

Complex Phase

Pump

ZincDeposit

Anolyte

Reservoir

Catholyte

Reservoir

+

figure 8. Zinc-bromine flow battery diagram.


7/10


and the metallic zinc plated on the negative electrode is dis-

solved in the electrolyte solution and available for the next

charge cycle.

One of the advantages of flow batteries is that their

construction is based on plastic components in the reactor

stacks, piping, and tanks for holding the electrolytes. The

result is that the batteries are relatively light in weight

and have a longer life. The typical flow battery can be

used in any duty cycle and does not have self-discharge

characteristics that can cause damage like other battery

technologies can.

Flow battery manufacturers are using modular

construction to create different system ratings and dura-

tion times. Figure 9 shows a zinc-bromine flow battery pack-

age with a rating of 500 kW for two hours. Other packages

are being applied at utilities with system ratings of up to 2.8

MWh packaged in a 53-ft trailer.

Another type of flow battery is the vanadium redox

battery (VRB). During the charge and discharge cycles,positive hydrogen ions are exchanged between the two

electrolyte tanks through a hydrogen-ion permeable polymer

membrane. Like the zinc-bromine battery, the VRB systems

power and energy ratings are independent of each other.

Numerous other chemistries are being developed around the

flow battery concept. New startup companies are expected to

announce flow battery technologies in the next few years.

Lithium-Ion BatteriesThe battery technology with the broadest base of

applications today is the lithium-ion battery. This technol-

ogy can be applied in a wide variety of shapes and sizes,

allowing the battery to efficiently fill the available space,

such as a cell phone or laptop computer. In addition to their

packaging flexibility, these batteries are light in weight

relative to aqueous battery technologies, such as lead-acid

batteries. As previously shown in Figure 5, lithium-ion bat-

teries have the highest power density of all batteries on the

commercial market on a per-unit-of-volume basis. Safety

issues with lithium-ion batteries in laptop computers have

been a recent concern, but continued development of the

technology for PHEV application has resulted in newer

types of lithium-ion cells with more sophisticated cell

management systems to improve performance and safety.

The leading lithium-ion cell design being applied in

new PHEV designs is a combination of lithiated nickel,

cobalt, and aluminum oxides, referred to as an NCA cell.

The designs life characteristics on float and cycling duty

have made NCA cells the primary choice for the next

generation of PHEVs. Two lithium-ion designs that are

starting to be used in higher-power utility grid applica-

tions are lithium titanate and lithium iron phosphate.

Lithium Titanate

The lithium titanate approach uses manganese in thecathode and titanate anodes. This chemistry results in a

figure 9. Zinc-bromine flow battery system (500 kW).(Photo courtesy of Altairnano.)

Lithium-Ion Battery Storage System

figure 10. A 1,000 kWh lithium-ion battery system ap-

plied in a utility frequency regulation application (photocourtesy of ZBB Energy Corporation).

The future of electric grids will be impacted by a growingpenetration of plug-in hybrid electric vehicles and electric vehicles,which will represent a new dimension for grid management.


8/10


very stable design with fast-charge capability and good

performance at lower temperatures. The batteries can be

discharged to 0% and appear to have a relatively long life.

Figure 10 shows a lithium-titanate battery in a utility power

ancillary service application (frequency regulation).

Lithium Iron PhosphateThe lithium-ion battery using iron phosphate cathodes is

a newer and safer technology. In this chemistry, it is much

more difficult to release oxygen from the electrode, which

reduces the risk of fire in the battery cells. This design ismore resistant to overcharge when operated in a range of up

to 100% state of charge.

As mentioned previously, lithium-ion batteries are used in

a wide variety of applications and will benefit from economy

of scale in production over the next decade. As shown in

Figure 10, the ancillary services market appears to be the

most available opportunity in utility power applications.

As volume production increases, the future cost of

lithium-ion battery systems will play a key role in how fast

they penetrate utility power applications.

Lead-Acid BatteriesThe lead-acid battery is the oldest and most mature of

all battery technologies. Because of the wide use of

lead-acid batteries in a wide variety of applications,

including automotive starting and

UPS use, lead-acid batteries have the

lowest cost of all battery technolo-

gies. For utility power application,

a 40-MWh lead-acid battery was

installed in the Southern California

grid in 1988 to demonstrate the

peak shaving capabilities of batter-

ies in a grid application. The battery

demonstrated the value of stored

energy in the grid, but the lim-

ited cycling capability of lead acid

made the overall economics of the

system unacceptable.

For backup power sources in

large power plants, lead-acid battery

plants are still used as black start

sources in case of emergencies.

Their long life and lower costs make

them ideal for applications with lowduty cycles.

Advanced Lead-Acid BatteriesThe high volume of production of lead-acid batteries

offers a tremendous opportunity for expanded use of these

batteries if their life could be significantly extended in

cycling applications. Adding carbon to the negative elec-

trode seems to be the answer. Lead-acid batteries fail due

to sulfation in the negative plate that increases as they are

cycled more.

Adding as much as 40% of activated carbon to the

negative electrode composition increases the batterys life.

Estimates of a cycling life improvement of up to 2,000cycles represent a three to four times improvement over

current lead-acid designs. This extended life coupled with

the lower costs will lead storage developers to revisit lead-

acid technology for grid applications.

Nickel-Cadmium BatteriesAs shown in Figure 5, which depicts the exponential

growth in the power density of batteries, nickel-cadmium

(Ni-Cad) batteries represented a substantial increase in

battery power in the middle of the last century. The Ni-Cad

battery quickly gained a reputation as a rugged, durable

stored energy source with good cycling capability and a

broad discharge range. Ni-Cad batteries have been applied

in a variety of backup power applications and were cho-

sen to provide spinning reserve for a transmission proj-

ect in Alaska. This project involves a

26-MW Ni-Cad battery rated for 15

min, which represents the largest bat-

tery in a utility application in North

America. The project was featured in

the March/April 2005 issue ofIEEE

Power & Energy Magazine. Ni-Cad

batteries are still being used for util-

ity applications, such as power ramp

rate control for smoothing wind

farm power variability in areas with

weak power grids (such as island

power systems).

Flywheel Energy StorageSpinning a weighted mass on the end

of the shaft of an electrical motor or

generator to provide ride-through

energy during short input power sags

or outages is a concept that has beenaround for decades. Slow-speed (up to

figure 11. A 100-kWh high-speed

flywheel assembly (photo courtesy ofBeacon Power Corporation).

As countries around the world continue to increasetheir renewable energy portfolio, the participation of storagein the success formula needs attention.


9/10


8,000 r/min) steel flywheels have been used as battery

substitutes in the UPS market for many years. These

devices are practical for ride-through times of up to 30 s.

Achieving longer storage times at high power levels

requires significant changes to the flywheel design and

choice of materials. In the simplest terms, the amount of

energy that can be stored kinetically in a flywheel is a

function of the cube of rotational speed. Higher speeds

translate to h igher energy storage densities.

Modern flywheel energy storage systems consideredfor utility power applications consist of a massive rotating

cylinder, as shown in Figure 11.

The cylinder is weighted with most of the mass located

on the outer edge to increase the moment of inertia and maxi-

mize the amount of energy stored. Flywheels of this design

can be operated in a vacuum and supported on magnetically

levitated bearings. This assembly is considered the stator

of a motor-generator, with the outer shell acting as the gener-

ator portion of the device. Typical operating speeds are up to

60,000 r/min. Actual delivered energy depends on the speed

range of the flywheel. For example, above a 3:1 speed range,

a flywheel will deliver up to 90% of its stored energy to an

external load.

Currently, high-speed flywheel systems rated 1,000

kW (15 min) or larger are being deployed in the U.S. grid

for frequency regulation use. At least three independent

system operators (ISOs) have opened their markets for

fast-response systems, such as flywheels and battery-

powered systems.

Electrochemical CapacitorsCommonly called supercapacitors, electrochemical

capacitors look and perform similar to lithium-ion

batteries. They store energy in the two series capacitors of

the electric double layer (EDL), which is formed between

each of the electrodes and the electrolyte ions. The dis-

tance over which the charge separation occurs is just a

few angstroms. The extremely large surface area makes

the capacitance and energy density of these devices thou-

sands of times larger than those of conventional electro-

lytic capacitors.

The electrodes are often made with porous carbon

material. The electrolyte is either aqueous or organic. The

aqueous capacitors have a lower energy density due to

a lower cell voltage, but are less expensive and work in awider temperature range. The asymmetrical capacitors that

use metal for one of the electrodes have a significantly larger

energy density than the symmetric ones do and also have a

lower leakage current.

Compared with lead-acid batteries, electrochemical

capacitors have lower energy density, but they can be cycled

hundreds of thousands of times and are much more powerful

than batteries (fast charge and discharge capability).

Supercapacitors have been applied for blade-pitch control

devices for individual wind turbine generators to control the

rate at which power increases and decreases with changesin wind velocity. This functionality is desirable if wind

turbines are connected to weak utility power grids.

New Battery TechnologyWith the growing interest in energy storage for greater

use in transportation and renewable energy, research

activities are increasing in private industry, universities,

and national laboratories. In North America, the U.S.

Congress mandated increased funding for research and

development (R&D) in energy storage. Major universities,

including the Massachusetts Institute of Technology

(MIT), are working to design new storage technologies.

MIT is investigating ways to create very large-scale

batteries capable of storing enormous amounts of power

in the utility grid.

Thermal StorageAll of the energy storage technologies discussed are

targeting ways to help the utility grid cope with balanc-

ing generation and load in the most opt imal ways possible.

Traditionally, utility grids have been designed to deal with

the highest load peaks that typically occur less than a few

hours per day for only a few days per year. Just like batter-

ies and peaking generators, any storage device that helps

meet this objective should be considered in utility system

planning. Thermal storage devices that can be deployed at

the residential and commercial level should be given more

attention. Modular ice storage systems can generate ice

during off-peak power periods to power air-conditioning

systems for several hours each day during the peak after-

noon load times. Similarly, in cold climates, modular heat

storage systems can capture electric power during off-

peak periods and use that energy to store heat in a ceramic

heatsink to be dispatched during higher peak periods in

the winter. As more utilities consider real-time pricing ofenergy based on actual cost, all forms of energy storage

Utility system designers have seen the benefitsof massive amounts of energy storage in the form of pumpedhydro power plants.


10/10


will provide more value and contribute to lowering the

overall peak demand.

This concept is not limited to small applications. In

Europe, a very large thermal storage system (up to 10,000

MWh) is being proposed.

What About Hydrogen?The development of hydrogen-based fuel cells as clean

energy sources continues around the world. In the

transportation arena, PHEVs appear to be developing acommanding lead over fuel cell-powered vehicles as the

clean energy choice. Proponents of a hydrogen economy

argue that large wind farms could be used to power

hydrogen-processing facilities and that pipelinesin lieu

of large electrical transmission linescould carry bulk

hydrogenas the energy sourceto major population

centers. Like todays large natural gas pipeline networks

that store gas conveniently in the system to match cus-

tomer demand, hydrogen would be stored as necessary to

match the demand for fuel cells for electricity and hydro-

gen-powered cars.

Critics question the overall efficiencies of creating

large quantities of hydrogen to power fuel cells to create

electricity. Large-scale adoption of hydrogen would require

a significant paradigm shift in the overall energy delivery

strategy in major world markets. Today, changes of this

magnitude do not appear possible in any of the worlds

major utility markets.

ConclusionsEducation about the value of energy storage in operating

electric power grids has been lacking for a long time. During

the 2003 conference aimed at establishing a vision for the

future smart electric grid, storage was identified as playing

a vital role in managing new and more complex networks.

Since that time, more attention has been given to the benefits

storage can provide. The infrastructure stimulus bill passed

by the U.S. Congress provided increased funding for storage

in the electric gr id and significant monies to advance storage

devices for PHEVs.

As countries around the world continue to increase

their renewable energy portfolionamely, wind power

the participation of storage in the success formula

needs attention. The November/December 2007 wind

integration issue ofIEEE Power & Energy Magazinecontained only very minor references to storages ability

to add value to wind resources by reducing the impact of

wind availability. Like wind power, storage can benefit from

financial stimulus to support its growth and demonstrate its

value in actual performance. The United States, Japan, and

Germany currently benefit from having fairly large amounts

of storage (pumped hydro) in their grids. Recognizing the

value of storage in dealing with the variability of renewable re-

sources is essential to harnessing the maximum potential of

wind and solar power. Fortunately, storage systems used

in grid applications will benefit from the huge investmentin electric-based transportation. In fact, the growth

of EVs to 50 million units (15-kW capacity average)

by 2030 would dwarf the installed capacity of major

renewable energy sources. The real technology challenge

will be making all of the new electric power resources func-

tion in a fully integrated smart grid.

For Further ReadingDOE Electricity Advisory Committee. (2008). Bottling

electricity: Storage as a strategic tool for managing vari-

ability and capacity concerns in the modern grid [Online].

Available: www.doe.energy.gov/eac

D. Rastler, New demand for energy storage,Elect. Per-

spect., vol. 33, no. 5, pp. 3047, Sept./Oct. 2008.

(2008, Nov.). Utility scale energy storage grinds into

gear. Climate Change Bus. J. [Online]. Available: www.

climatechangebusiness.com

B. Lee and D. Gushee. (2008, June). Massive electric-

ity storage. AICHe White Paper [Online]. Available: www.

aiche.org

C. Vartanian, The coming convergence, renew-

ables, smart gr id and storage,IEEE Energy 2030, Nov.

2008.

Parliamentary Office of Science and Technology.

(2008, Apr.). Electricity storage [Online]. no. 306. Avail-

able: www.parliament.uk/parliamentary-offices/post/

pubs2008.cfm

J. McDowall. (2008). Understanding lithium-ion tech-

nology, BATTCON 2008 [Online]. Available: http://www.

battcon,com/Archive Papers.htm#McDowall2008

BiographyBradford Roberts is the power quality systems director for

S&C Electric Company and chair of the Electricity StorageAssociation. p&e

One of the advantages of flow batteries is that their constructionis based on plastic components in the reactor stacks, piping, andtanks for holding the electrolytes.

ESA TR 8 09 Capture Grid Power Roberts

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