Prudent Energy

Storage for a sustainable future

The Global Leader in Advanced Energy Storage

Large scale Energy storage – applications of the VRB-ESS®

in providing electrical grid power solutions

Intersolar 2012

Timothy Hennessy June 11 2012

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About Prudent Energy

• Provides proprietary VRB® Energy Storage Systems (VRB-ESS®) for grid and

renewable energy storage applications between 200kW to 10MW 100MWh

• 10 years operation with the VRB® technology: 200 employees

• Over 20MWh commercial sales and installations in last year across 11 countries

• VRB® and storage application Patents: control all substantial patents including

51 issued patents and 48 pending patent applications in 34 countries

• Major Investors: MITSUI Corporation, GS Caltex, State Power Group, DFJ and

DT Capital, CEL, Northern Light

Company Overview

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Prudent VRB® Technology

What is a Flow Battery?

Regenerative fuel cell or “Cell

Stack”

Independent electrolyte storage

tanks

Pumps to circulate electrolyte

Control system to manage

electrolyte circulation

Flow battery technologies are

distinguished by electrolyte

composition

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Prudent VRB® Technology

Flow Battery Cell Stack

Array or “stack” of individual

cells in series

Each cell consists of

bipolar plate

2 electrodes

Membrane separator

• Colors of Vanadium at different ionic states

• Non Toxic

• Readily available from waste streams such as flyash

V+5 -> V+2

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Prudent VRB Technology

Advantages

No daily “off periods” - always on

Power and energy capacity can be sized

independently of one another

Operates at any SOC without life impact

Any Depth of Discharge (DOD)

Lowest LCOE (unlimited cycles of

electrolyte)

Large surge capability possible

Efficient over 100% DOD range

< 1 cycle responses

Low pressure and low temperature=safe

Disadvantages

Low energy storage density = big footprint

Not mobile

Flow Battery Advantages and Disadvantages

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The modular assembly of a MW scale VRB-ESS® in California

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The modular assembly of a MW scale VRB-ESS® in California

• Peak Shaving

• Using bio gas from

onion plant

• Gills Onion’s

California

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500kW 750kW pulse (10 minutes) / 1MWh

Results – one of other technologies has

had performance issues within a year

Our performance has been solid

Ambient temperatures down to -30C

Provides continuous reactive energy

(MVAR)

2MW * 8MWH system being

commissioned in September 2012 – wind

PV - grid connected

MW scale VRB-ESS® in China - wind and PV smoothing

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Microgrids – island and hybrid systems

• 400kW x 500kWh diesel, PV

and micro-hydro, Hybrid in

Indonesia

• Slovakia – smart grid 600kWh

• Hawaii – islanded PV

• China – smart grid wind and PV

• Korea Smart grid Jeju island

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VRB® characteristics from field testing

1. Response time full charge

to discharge < 50ms

2. Stack Coulombic efficiency

3. Short circuit test – stack

shorted max 2000 Amps.

Discharged over 140

seconds. System recovered

after short removed

4. Longest field operation 6

years un-manned

Short circuit test

Response time ms

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Future enhancements to VRB® Technology

• Energy density of electrolyte being improved – reduces footprint and costs

• Footprint reduction of plant – higher efficiency of cell stacks

• Market driven cost reductions depends on application e.g. renewable power

smoothing, peak shaving etc.

• 40% footprint reduction

2011 to 2013

• Modular 250kW

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Implications of community based generation in Distribution System

• Power flows no longer in

one direction due to multiple

sources

• Complex protection

coordination due to multiple

generation sources

• Microgrid or community

grids contains both

generation and load

• Managed independently

of main distribution

system and can operate

even if main transmission

source is cut

Courtesy Brad Williams Oracle

storage

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Germany Current Situation

Reports on critical grid conditions [Reference: Paul-Fredrik Bach: Frequent wind

power curtailments 14 April 2012]

Recently “Welt Online” reported on “alarm level yellow” for German power grids on 28

and 29 March 20121..

During first quarter EON Netz has issued 257 interventions.. Thus there have been

interventions active for 23.1% of the hours in first quarter.

Part of the solution is storage backed

microgrids owned by communities

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Comparisons of Wind and PV systems with energy storage for municipal

owned microgrids

0 100 200 300 400 500 600 700 800

-2

0

2

4

6

8

10Net Power with 9MW PV and No Wind

Time, Days

Po

we

r, M

W

4 Hours Storage Duration

6 Hours Storage Duration

0 100 200 300 400 500 600 700 800

-2

0

2

4

6

8

10

12Net Power with 9MW Wind and No PV

Time, Days

Po

we

r, M

W

4 Hours Storage Duration

6 Hours Storage Duration

4 cases: Objective to minimize grid demand and reduce volatility of power sold to grid.

• PCC= 9MW: Below zero in graphs indicates grid purchases i.e. NON FIRM

renewable resource

• Smoothing effects and ramp rate (stability) management provided by energy storage

• Cases examine mixes of PV and wind generation along with 2.5MW of storage with

durations of 1, 2, 4 and 6 hours all at 2.5MW FIRM PPA with utility

• Finding is that between 4 to 6 hours of storage yields lowest volatility and minimum

grid purchases.

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Firmness provided by storage in islanded micro grids

0 100 200 300 400 500 600 700 800

-2

0

2

4

6

8

10

12Net Power with 5MW Wind and 4MW PV

Time, Days

Po

we

r, M

W

1 Hour Storage Duration

6 Hours Storage Duration

0 100 200 300 400 500 600 700 800

-2

0

2

4

6

8

10

12Net Power with 5MW Wind and 4MW PV

Time, Days

Po

we

r, M

W

4 Hours Storage Duration

6 Hours Storage Duration

Wind (MW) 5

PV (MW) 4

1 hour storage duration Grid purchase (times/year) 230 Energy purchases (MWh) 604.7

4 hours storage duration Grid purchase (times/year) 152 Energy purchases (MWh) 35.8

6 hours storage duration Grid purchase (times/year) 8 Energy purchases (MWh) 2.7

Grid purchases when

storage sized at 1hour

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Peaking generation enhancing the value of OCGT using Energy Storage

Also reduces CO2 emissions

Ref: PJM USA markets

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Energy trading using flow batteries in Germany

IRR over ten

years > 15%

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Summary of Alternative Grid Energy Storage Solutions

Electrochemical energy storage is the most preferred practical solution for distributed

grid energy storage applications but one size does NOT fit all

Pumped Storage

Compressed Air

Energy Storage

(CAES)

Hydrogen

Open Cycle Gas

Turbines, Diesels or

Coal Fire Station

Electrochemical

Energy Storage

Solutions

Comments

• Mature

• Long lead time

• Geographical

limitation

• Large scale

• Lowest cost

• Limited by

geology

• Central type

plant

• Long lead time

• Large scale

• Long duration

• Expensive with

low efficiency

• Risky

• Highest energy

density

• Central type

plant

• Medium CAPEX

• High impact on

environment

• Low average

efficiency

• Risky gas

supply

• Fast delivery

• Low operating

cost

• Environmentally

friendly

• Higher initial

CAPEX

Fit for

Commercial

Grid Storage

Applications

Exists – part of

mix not distributed

Possible part of

mix

Possible part

solution

Yes part of mix

Distributed

essential part of

solution

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Summary and observations

Energy Storage can be used to “FIRM” variable generation resources both centrally and distributed

Electrochemical Storage prices are coming down

GAS fired generation combined with storage for fast acting reserve is more economic than standalone gas fired generation alone.

Distributed Storage must form part of any SMART GRID in order to manage power flows

An approach to microgrids allowing communities to island their resources will occur and regulations applying to these should be developed

Long term storage is essential for stability and energy management in distributed generation grids

Government and regulatory bodies must lead the way in setting appropriate policy and tariffs such as locational marginal pricing to direct storage investments

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