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
Timothy Hennessy
June 15 2012
About Prudent Energy
Company Overview
• 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
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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
Flow Battery Advantages and Disadvantages
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
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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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MW scale VRB-ESS® in China - wind and PV smoothing
 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
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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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KW class VRB-ESS® for Telecoms and commercial sites








5 to 10kW
No refuelling costs
Long Life (10+ years)- electrolyte
never wears out
No degradation on deep cycling
Low maintenance
Always on – no bridging power
needed - SOC always known
Long duration storage independent
of power – scalable up to 10 hours
Closed loop no emissions – no
disposal issues
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VRB® characteristics from field testing
Response time ms
Short circuit test
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
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Cell stack evolution - 2002: 2012
SEI 42kW stack
VRB P3 5kW- 10kW
VRB P3 2010
VRB P1 5kW 2004
S5 stack 2012
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Schematic of a conventional battery and PCS are separate
VRB-ESS
is a
system
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PCS – Power Conversion system
•
Sized in modular form ABB PCS-100 provides 4 quadrant operation, P&Q and
F&S modes of operation ABB PCS 100
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HMI Power Screen for the VRB-ESS
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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.
• Modular 250kW
•
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40% footprint reduction
2011 to 2013
4MW 16MWh Plant
33m x 35m for delivery 2013
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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
storage
• 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
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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
Net Power with 9MW Wind and No PV
Net Power with 9MW PV and No Wind
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10
4 Hours Storage Duration
6 Hours Storage Duration
4 Hours Storage Duration
6 Hours Storage Duration
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8
8
Power, MW
Power, MW
6
4
2
6
4
2
0
0
-2
-2
0
100
200
300
400
500
Time, Days
600
700
800
0
100
200
300
400
500
Time, Days
600
700
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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800
Firmness provided by storage in islanded micro grids
Net Power with 5MW Wind and 4MW PV
Net Power with 5MW Wind and 4MW PV
12
12
10
10
8
8
6
6
Power, MW
Power, MW
4 Hours Storage Duration
6 Hours Storage Duration
1 Hour Storage Duration
6 Hours Storage Duration
4
4
2
2
0
0
-2
-2
0
100
200
300
400
500
Time, Days
Grid purchases when
storage sized at 1hour
600
700
800
0
100
200
300
400
500
Time, Days
Wind (MW)
Grid purchase (times/year)
Grid purchase (times/year)
Energy purchases (MWh)
6 hours storage duration
Grid purchase (times/year)
Energy purchases (MWh)
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800
4
Energy purchases (MWh)
4 hours storage duration
700
5
PV (MW)
1 hour storage duration
600
230
604.7
152
35.8
8
2.7
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
• Medium CAPEX
• High impact on
environment
• Low average
efficiency
• Risky gas
supply
• Fast delivery
• Low operating
cost
• Environmentally
friendly
• Higher initial
CAPEX
Solutions
Comments
Fit for
Commercial
Grid Storage
Applications
• Mature
• Long lead time
• Geographical
limitation
• Large scale
• Lowest cost
Exists – part of
mix not distributed
• Limited by
geology
• Central type
plant
• Long lead time
• Large scale
• Long duration
• Expensive with
low efficiency
• Risky
• Highest energy
density
• Central type
plant
Possible part of
mix
Possible part
solution
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Yes part of mix
Distributed
essential part of
solution
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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