ELECTRICITY STORAGE FOR CAPITAL DEFERRALEnd-User: Utah Power, a subsidiary of Scottish Power affiliate PacifiCorp (installed by VRB Power Systems Inc.)

Application: Defer capital expenditure by shifting peak load on a 25 kV distribution feeder

Benefits: Improved distribution throughput, lower line losses, better power quality

Basic Specifications of the VRB Energy Storage System (VRB-ESS TM ):

Continuous Power Rating: 250 kW, 250 kVAR, 353 kVA using intelligent,

programmable four-quadrant power converter

Energy Storage: 2,000 kWh – 8 hours discharge at full rated power output

Footprint: 3,800 square feet (350 square meters) – allows for expansion to 500 kW within existing building.

Operation Start: March 2004

Project Background and Objectives:Utah Power operates a 209 mile, 25 kV distribution feeder in environmentally pristine Southeast

Utah, near Moab. Bordering the eastern side of Arches National Park and following the Colorado

River valley, the line traverses great distances to serve small, isolated

rural communities. Reliability and power quality problems had

resulted in Public Service Commission complaints, and new service

connects were being denied because the feeder could not supply

including line reinforcement, substation upgrades and increased

reactive compensation. Ultimately, it decided on an energy storage

solution from Prudent Energy as an economically attractive way to avoid both the high cost of adding a large

increment of new capacity using conventional means, and the lengthy permitting process that would have

been required in this sensitive geography.

A site was selected in Castle Valley,

Utah, where a simple metal building was

erected to house the initial 250 kW, 8-

hour (2MWh) system, with space allowed

for future expansion. Construction of

the storage system was straightforward,

consisting of two off-the-shelf double wall

(two in series, three pairs in parallel),

pumps, heat rejection equipment, a

packaged power conversion system, and

Allen Bradley controls and monitoring. 0

2,000

2,500

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3,500

4,000

Feed

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oad

(kW

)

Feeder Capacity Limit

24201612841,500

Nomal Load

Hour of Day

Feeder Load withEnergy Storage Discharging Feeder Load with Energy

Storage Charging

continued (over)

Unit 04-09A, SOHU.COM Internet Plaza,Tsinghua Science Park, Haidian District, Beijing, ChinaTel: (8610) 82158025　 Fax: (8610) 82151477Website: www.pdenergy.comCA

SE S

TUDY

VRB , VRB-ESS and VRB Energy Storage System are trademarks of Prudent Energy Inc.TM TM TM

The system was initially started in November, 2003 and formally commissioned in March, 2004.

Designed for unmanned operation, the system was initially set up for time-of-day cycling, charging

overnight and discharging during the peak afternoon period. Voltage response is less than 5 milliseconds,

and the operating temperature range is 41° to 104° (5° to 40°C). The charge/recharge cycle (adjustable

algorithm, with control override based on battery state-of-charge. The VRB-ESS controller program

allows easy changes to all parameters, including dates and times. The scheduled kW output changes

voltage changes.

The system also provides a temporary voltage support mode.

If the measured voltage at 480 V drops between 2 and 10% of the

previously measured voltage for three consecutive controller scan cycles,

the VRB-ESS increases discharge to full 250 kW within 5ms even

if it was in charging state, and maintains this output for 30 minutes

(provided the fault current settings allow this). After 30 minutes, the

VRB-ESS returns to the normal schedule following the kW rate of

change ramp. Ongoing testing will make use of the system’s ability

to provide automated VAR support.

Results:

The system operated charging and discharging over its full power capacity and duration, some 1,600 cycles since installation. Feeder power factor improvement has allowed the relocation of shunt capacitor banks, loadgrowth and has reduced line loses by over 40kW more than offsetting the parasitic losses of the storage system. Several studies and reports by EPRI have been completed.

The company has made further enhancement to system efficiency and reliablity through the upgrade of the power conversion system and cell stack in late 2004.

The application has demonstrated the viability of using a VRB-ESS as a planning solution for utilities, and the results of this project will enable a number of other utility applications for electricity storage in the future.

CASE

STU

DY

Unit 04-09A, SOHU.COM Internet Plaza,Tsinghua Science Park, Haidian District, Beijing, ChinaTel: (8610) 82158025　 Fax: (8610) 82151477Website: www.pdenergy.com

VRB , VRB-ESS and VRB Energy Storage System are trademarks of Prudent Energy Inc.TM TM TM