Confidential

Northern Power EnergyBridgeTM UPS Status UpdateSeptember 29, 2008DOE Peer Review – Washington, DC

This project is part of the Energy Storage Collaboration between the California Energy Commission (CEC) and the Energy Storage Systems Program of the U.S. Department of Energy (DOE/ESS) and managed by Sandia National Laboratories (SNL). Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration, under contract DE-AC04-94AL85000

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Project Objectives

• Maintain high power quality on protected loads at all times

• Provide power to protected load in event of a utility sag or outage

• Meet the ITI (CBEMA) curve during power quality events

• Resynchronize with backup power or grid as necessary

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Palmdale Water District Clearwell Site

ClearwellProtected

Loads~400 kW

Diesel Back-up800 kW

SCE UtilityGrid

Static switch

PQM

ClearwellOther Loads

~350 kW

Hydro250 kW

ATS

PQMM

EnergyBridge™ EB 450

Ultracapacitors

Power conversion

450 kW

NG Genset200 kW

PQM

ATS

Utility meter

Power quality meter

Automatic transfer switch

Circuit breaker

Legend

M

4

One Line Diagram

SeriesInductance

Ls

FastSwitch

S1

BypassBreaker

CB3 (Optional)

IsolationBreaker

CB2

IIsolationBreaker

CB1

Bi-directionalInverter

Bi-directionalDC to DCConverter

UltracapacitorBank

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ToUtilityGrid

ToCriticalLoads

InductorL3

ElectrolyticCapacitor Bank

Sub-system 2: Shunt Power Conversion

Sub-system 1: Series Components

DSP Controller

Sub-system 3: Energy Storage

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EnergyBridgeTM UPS System at PWD

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Project Status Milestones

• Factory Witness Test September 2007• System Installed in December 2007• System Commissioned March 2008• On Site Acceptance Test May 2008

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EnergyBridgeTM UPS Project

• Aggressive Goals:

Develop a production-ready prototype 450kW Ultracapacitor based uninterruptible power supply

o New hardware design for power convertero New control architecture design using distributed control

Demonstrate prototype with motor + process control loads

• Significant underestimation of problem size and inherent challenges for UPS grade operation

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On Site Acceptance Test

• Test performed with high standards• Test procedures designed to test system

performance based on original UPS grade design goals

• Each test performed only once, no “do-overs”• Demonstrable outliers still scored as failures

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Project Successes

• Demonstrated successful system operation for limited loads

• Demonstrated power quality improvement for all loads• Ultracapacitor interface and control demonstrated• Demonstrated system operation for generator and grid

source• Demonstrated proper operation and capability of

hardware

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Load Support From / To Grid

• Mostly satisfactory for large and medium loads

Requires load dependent controller settings

Marginal control stability results in “random” faults

• Possible, but unsatisfactory for no / low load• Hardware capable of performing goal• Control algorithms require significant

additional development work to meet UPS grade operation

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200hp PWD Load Grid Power Quality

• Input displacement power factor corrected• Compensating harmonic current injection to grid

Grid Voltage

Grid Current

Load Current

Load Voltage

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Voltage Waveforms, 200hp PWD Load

Note: These actual waveforms were acquired with a low sampling frequency.Therefore the non-sinusoidal appearance is a measurement artifact.

Grid and Load Voltages

-500

-400

-300

-200

-100

0

100

200

300

400

500

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61

Vgrid A

Vgrid B

Vgrid C

Vload A

Vload B

Vload C

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200hp PWD Load Support V & I

• Series switch open (zero grid current)• Load supported by power converters & ultracapacitors

Grid Voltage

Grid Current

Load Current

Load Voltage

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Ultra-Capacitor Control

• Control algorithms fully functional• Charging and discharging of ultra-capacitors

well behaved• Modular and autonomous operation of

capacitor strings demonstrated• Future work is refinement and cost reduction

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Bus Voltages & Ultracapacitor Currents 200 + 150 hp PWD Load Support

GridConnected

IsolatedLoadSupport

Recharge Ultracapacitors

Grid Connected

dc Bus Voltage and Capacitor Voltage & Current

650

700

750

800

850

900

11:41

:0511

:41:10

11:41

:1511

:41:20

11:41

:2511

:41:30

11:41

:3511

:41:40

11:41

:4511

:41:50

11:41

:5511

:42:00

11:42

:0511

:42:10

11:42

:1511

:42:20

11:42

:2511

:42:30

11:42

:3511

:42:40

11:42

:4511

:42:50

11:42

:5511

:43:00

11:43

:0511

:43:10

11:43

:15

Time

Volta

ge (V

)

0

100

200

300

400

500

600

Cur

rent

(A)

3A_A_VoltCap_V

3B_A_VoltCap_V

3C_A_VoltCap_V

3D_A_VoltCap_V

DC_bus_avg_v_bus

3A_A_CurNeg_A

3B_A_CurNeg_A

3C_A_CurNeg_A

3D_A_CurNeg_A

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Northern Power Corporate Status

• Northern Power now a private company owned by new investors as of August 2008

Publicly traded Distributed Energy (old owner) filed Ch. 11 on 04 June 2008 and sold the Northern Power asset

• Northern Power focused on wind turbine technology

Northwind® 100 wind turbine is present commercial product

Developing 2.2 MW wind turbine

Power electronics (PE) in support of wind secondary focuso MW Wind power convertero Other PE systems to further enable wind sales

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EnergyBridgeTM UPS Project Future Status

• Limited testing on demonstration system going forward

• Northern pursuing energy storage solutions for wind-diesel applications

Northern is seeking an energy storage partner for commercializing an energy storage product that operates with our Northwind 100 wind turbine

• Evaluating wind-energy storage for utility grids

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Future Opportunities for EnergyBridgeTM Technology

• Increase wind penetration in isolated wind-diesel grids

Real, identified customer driven market in Alaska (AVEC)

Potential market for rural agricultural pumping

Present solution not satisfactoryo Secondary load to handle load sheds / wind gustso Doesn’t handle load increases / wind lullso Limited ability to utilize dump load

• Load Leveling in Grid Connected Wind Farms

Same concept as above, only much larger scale

Large potential market including locations in Palm Springs, Altamont and Tehachapi

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Wind-Diesel System Architecture

Northwind® 100 Wind Turbine