Transcript Power Delivery

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An Electric Utility Perspective on Applications of
Electricity Storage for Distributed Generation
Workshop on Advances in Electricity Storage in Support of
Distributed Renewable Energy Based Systems
Monday, May 10, 2004
Hyatt Regency Waikiki
Bradley R. Williams, PE
Director, Power Delivery Business Technology
PacifiCorp, Portland, OR
[email protected]
DISTRIBUTION
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PacifiCorp Quick Facts
• 1.5 million electric customers in six
Western states
• Doing business as Pacific Power and
Utah Power
• Low-cost, reliable energy producer
• 8300 megawatts of generation
capacity from coal, hydro, gas-fired
combustion turbines, geothermal,
co-generation and renewable wind
power
• 6,400 employees in the United
States, headquartered in Portland,
Oregon
• President and CEO: Judi Johansen
• Part of the ScottishPower Group,
which additionally provides energy
and other utility services to 5.5
million customers in the United
Kingdom.
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May 10, 2004
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Utility Distribution Applications best Suited to
Distributed Electricity Storage
• High loading - existing infrastructure at full capacity
• High Costs to increase capacity and/or build transmission
• Slow to moderate load growth to leverage best asset
deferral benefit
• Feeder voltage/reactive power (var) support needed
• Difficult access to stable fuel source
• Difficult permitting process for DG combustion engines
Load Concentration
Substation
CB
Feeder capacity
limit
DG
emissions
Energy Storage (300kW) Support of Feeder Load
4000
Normal Load
Feeder Load (kW)
3500
Feeder Capacity Limit
Feeder Load with
Energy Storage Discharging
3000
Feeder Load with Energy
Storage Charging
2500
2000
1500
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9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour of Day
POWER DELIVERY
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Rattlesnake#22
25kV Feeder
• Environmentally Pristine Southeast Utah
–
–
–
Castle
Valley
East of Moab
East of Arches National Park
Along Colorado River valley
• 209-mile long 25kV feeder, with 3-line regulators & 7-reclosers
• Possible denial of new connects because feeder cannot supply any
significant amount of new load without causing low voltage to existing
customers.
• Because feeder is so long, reliability and power quality is low leading to
Public Service Commission Complaints. PacifiCorp agreed to fix.
• Traditional alternatives to add capacity and improve service are very
costly and environmentally difficult.
• Demonstrated distribution benefits of VRB energy storage as part of
PacifiCorp's DG Strategy – 2 MWh, 250kW VRB-ESS (expandable to
1MW) in Castle Valley, Utah
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Castle Valley, Utah - VRB Site
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Utility Electricity Storage Applications
Power quality and reliability
Energy management applications
applications
Spinning and standby reserve
Power rating
100 MW
Frequency
control
10 MW
1 MW
100 kW
Power quality
10 kW
Black start
Load levelling/following
Un-interruptible
power supplies
Voltage
support
VAR support
Transmission
stability
Peak shaving
Load factor increase
Capacity deferral
Integration of renewables
Tariff trading
0
0
1s
10s
1 min
30 min
1h
2h
Storage inventory
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May 10, 2004
4h
8h
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Electricity Storage Technology Alternatives
UPS
Market
Flywheels
Batteries
• Li Ion
• NiMH
Capacitors
1-MW
10-MW
Large-scale batteries
Lead-acid
NAS
VRB
ZBB
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May 10, 2004
100-MW and above
Pumped storage
Compressed Air
Energy Storage
(CAES)
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PacifiCorp’s View of Electricity Storage
• Excellent progress in electricity storage technology &
power electronics
–
Redox Flow Cell stores charged electrolytes separate from cell for
greater kWh storage capability. Best distributed resource applications.
• Efficiency: 60-85%
• Best Applications:
– Deferred Power Delivery assets: Peak Shaving, load following,
dynamic frequency control, volt-var support
– Large renewable wind and solar projects. Leveling applications.
– Premium Power: Industrial/Commercial High 9’s Availability (99.999%
available)
• Opportunity for early adopters
– Looked at a number of storage technologies: Regenesys, ZBB, VRB, others
– Selected VRB Power Systems due to efficiency, availability, and scalability
(smaller size initially to prove the technology).
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May 10, 2004
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What is a Vanadium Redox Battery?
Vanadium Redox Batteries are a type of energy
storage system (“VRB-ESS”) - flow batteries
capable of storing electrical energy and deploying
it back to the grid when required.
The VRB-ESS is charged like any other battery,
but the energy is stored by chemical changes to
the electrolyte. The electrolyte is a solution of
ionic forms of vanadium in a dilute sulfuric acid
that are electrochemically oxidized or reduced to
store the energy. The acidity level of the
electrolyte is no greater than a conventional car
battery.
The VRB-ESS is a “green” technology.
It has no emissions, and does not
contain heavy metals. Most other
energy storage systems rely on toxic
substances such as lead, zinc or
cadmium. The electrolyte used in the
VRB-ESS has an indefinite life and is
completely reusable.
The electrolyte is pumped from separate plastic
storage tanks across proton exchange membranes
in the cell stacks, creating a current. The reaction
is reversible, allowing the battery to be charged,
discharged, and recharged with high efficiency.
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Castle Valley VRB System
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VRB Energy Storage System Components
•
•
•
V2+ and V3+
V4+ and V5+
•
•
DC Power
AC Power
Electrolyte storage tanks
Cell stacks (with proton exchange
membranes & carbon felt
electrodes)
Pumps to move the electrolyte
fluid through the cell stack
ac/dc Inverter and power
conditioning
VRB ESS Control system
The battery provides DC power.
Therefore, an inverter is used to
convert it to alternating current
when it is returned to the electric
delivery system.
Also involved: control, monitoring, and
temperature regulation systems
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VRB Chemistry
-
dc Power
V4+/V5+
V2+/V3+
Vanadium sulfates in H2SO4
V2+
V5+ + e-
+
 V3+ + e-
[1]
 V4+
[2]
• Based on reduction and oxidation of different ionic forms of Vanadium.
• Chemical energy can be stored indefinitely (very low discharge rate).
• Very fast conversion response: less than 1 millisecond to change from charging to discharging.
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Potential VRB-ESS Utility Applications
•
Load Leveling (Peak Shaving)
–
•
Ancillary Services to Utilities
–
•
Uninterruptible Power Supply (UPS) – emergency power backup for loss of AC, voltage sags, dips, etc.
Voltage support & flicker compensation
Power factor management
Quality of Supply (QOS) – supply side management
–
–
–
•
The VRB Energy Storage System is a means of buffering both the flow and supply of power and thereby
increase the associated delivered capacity in MW on a network path that is otherwise constrained.
Power Quality & Reliability– demand side management
–
–
–
•
Reserves - Spinning, Standby, Replacement - In the event of the loss of output from a supply source or an
unexpected change in system demand, the VRB-ESS can immediately provide the required power to
make up the shortfall.
Constraint Relief & Capital Deferment
–
•
The VRB Energy Storage System can reduce the peak of a customer’s energy load as seen by the
distribution system. This enhances utilization of assets on the electrical grid and manages customer
energy demand.
Reactive power provision
Capacity extension – improves voltage regulation
Power factor management
Renewable Energy Capacity Support
–
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The VRB-ESS can serve as a buffer between a variable supply sources and the firm competitive
requirements of a power contract – which could add value to non-firm resources such as wind and
photo-voltaic (PV). It could also provide stabilization of wind turbine output and is a source of reactive
energy.
POWER DELIVERY
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Example Peak Shaving
High Cost
Low Cost
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Renewable Energy Applications
•
•
•
•
The VRB can be used to store
solar and wind energy
Using a VRB can smooth the
power supplied, making it
more constant
The VRB can provide reactive
energy through the AC/DC
converter
The VRB is an environmentally
friendly alternative to diesel
generators and larger lead
acid batteries
King Island – Hydro Tasmania
800kWh VRB Integration with
Remote Wind & Diesel Systems
• Reduced emissions – 47%
• Saved fuel costs – Load factor is
28% or 10,000litres/day average.
Reduced by 1.5million/litres/year
• Reduced Operating and
Maintenance costs
• Improved power system stability
and enhance power quality
Wind output is variable so capacity is discounted by > 75%
VRB can firm supply and increase capacity and efficiency
VRB
renewable energy source
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May 10, 2004
AC/DC
Converter
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Castle Valley VRB Enclosure Footprint (m2) per
capacity
Hours
kW
50
100
200
500
1,000
2,500
10,000
2.0MWh – 250kW
4
6
8
10
11
21
46
60
120
272
622
16
32
46
90
179
408
933
21
42
46
120
239
414
995
26
53
57
149
272
518
1291
• Castle Valley enclosure 7300 sq. ft. designed for expansion, room to work,
and visitors (being 1st VRB in North America).
• Minimum VRB foot print design for 1MW-4hrs = 3200 sq ft.
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Modular Design
• Sumitomo (Japan) – 50kW VRB Cell Stacks have 5X short duration
overload rating for PQ support and major disturbance mitigation.
• Each stack size = 4.2-ft X 3.2-ft X 3.6-ft (1.3m X 1.0m X 1.1m)
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VRB Cell Stacks
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Electrolyte Storage Tanks
• 58-ft long, 9.5-ft diameter. 70,000 liters capacity
• Fiberglass (double wall) construction with leak detection sensors.
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Inverter
•
•
•
•
TSI/Eskom QuPS 250kW, 300kVAR inverter
1200A, Vdc=200-300 volts with constant power output
Internal ac bus = 600volts (IEEE 514 harmonic filter capability)
Overload capability = 200% for 10-seconds, 150% for 5-minutes
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System Layout Design
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Cell Operating Range State of Charge
Cell potential vs. state of charge
T = 298 K
1.6
Open Circuit Voltage / V
1.5
1.4
1.3
1.2
1.1
1
0.9
0
0.1
0.2
0.3
0.4
0.5
0.6
State of Charge
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0.7
0.8
0.9
1
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Charge Discharge curves for VRB-ESS
900
400
800
200
100
700
0
600
-100
-200
500
Battery potential
Battery current
Elelctrolyte Temp: 38-41 C
400
-400
0.0
0.5
1.0
1.5
2.0
2.5
Discharge/Charge time (hr)
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-300
3.0
3.5
Battery current (A)
Battery potential (Vdc)
300
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Operating Parameters
• Temperature range - 5ºC to 40ºC
• Electrolyte concentration – 1.6 to 2.4 Mole/liter
• Sulphuric acid concentration 2 to 4 Mole/l
• Electrolyte Hazardous classification: EEC 8, 6.1
• Speed of response - <1ms
• SG – 1.36 to 1.47 kg/liter
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Castle Valley VRB Project Status
•Initial operations in startup and testing in November 2003
•Continuous full power daily cycling operations since March
2004
•On-going monitoring and performance testing
•Minor Capacity enhancements Underway
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PacifiCorp VRB Future Plans
•Advanced application development:
–
–
–
–
–
–
Advanced power quality applications
Advanced islanded operations
Adaptive charge/discharge energy arbitrage control algorithms
Advanced dynamic voltage control algorithms
Dynamic stability control algorithms
Wind farm application studies
•DOE Wyoming Wind Farm / Energy Storage Study.
•Increases to capacity through:
– Additional cell stacks
– Higher capacity inverter
– Increased molarity of the electrolyte
•Can relocate to new site once transmission line and sub is built
•Investigating future telecom site and substation battery
replacements
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Storage Business Case
Southeastern USA 2004
Generator (1,000kW 6 hours/day 320days/y) –1,920,000kWh/year
• Fuel ($9/MMbtu) and O&M costs ($0.0168/kWh) per year = $214,000
• CAPEX cost per year (20 years @ 7%) = $99,523
• Equivalent cost of energy = $0.1634/kWh
VRB-ESS 1,000 kW 1,000kVAR for 6 hours storage
• Fuel cost (off peak purchases $0.013/kWh @80% efficiency) and O&M
per year = $45,000
• CAPEX cost per year (20 years @ 7%) = $267,000
• Equivalent cost of energy = $0.1625/kWh
• Ancillary services are additional value streams that could be derived
by a storage system, and a hedge against gas price volatility
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Cost Benefit Analysis Arbitrage – East Coast
•
•
•
•
Out of City generation = 300MW
Unable to deliver during peak daytime loads due to line constraints
Option – Install several distributed Energy Storage systems locally to the
loads.
Cost of Storage installation $320/kWh – 10MW, 10MVAR, 10 hours
Size of connection - kW
energy charge plus O&M - $/kWh
10,000
0.024
Demand charge - $/kW.month
Repayment period -years
Energy price in $/kWh
Capacity price in $/kW.month
Period available in year (hours)
Discount rate (WACC)
Assumed depreciation period - years
0.55
15
0.12
2.00
3650
7.00%
12
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NPV = $5.6million
ROI AT = 23%
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Cost Benefit Analysis Industrial facility - NY
Industrial customer Daily load profile in NY with Storage
•Maximum Demand – 3,862kW
3,000
2,500
2,000
kW
•Minimum Demand – 680kW
•Simple payback < 6 years
Average Demand
22
20
18
16
14
12
VRB Charge (+ve) discharge (-ve)
Resultant Demand curve
kW
Monthly Max Demand Industrial - NY
4500
4000
3500
3000
2500
2000
1500
1000
500
0
1
2
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May 10, 2004
10
hour
•Storage shifts 6,230kWh usage
per day from peak pricing to
off peak pricing and MD
reduced 800kW.
•Annual saving based on
current tariffs - $292,000
8
0
(500)
(1,000)
6
•Storage – 800kW x 6 hours 75%
round trip efficiency
4
500
2
•Load factor 60%
1,500
1,000
3
4
5
6
7
Month
8
9
10
11 12
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Industrial Consumer Solution
60
50
Grid, Regenesys, Mill energy interaction
40
30
60.0
20
10
50.0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Power in period
40.0
Profile Without Storage
30.0
20.0
60
From Reg to Mill
50
From Grid to Reg
10.0
40
From Grid to Mill
30
0.0
20
1
Re g e n e s y s Ef fic ie n c y L o s s
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Profile With Storage
Courtesy Regenesys – Mr. Mark Kuntz
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11
12
13
14
Time period
A v e ra g e
15
16
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18
19
20
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Conclusion - Lessons Learned
from Utility Energy Storage Application
1.
Focus on best applications – this can make or break the project.
2.
Cost – CAPEX and O&M (life cycle) – Maximize efficiency, minimize
maintenance requirement
3.
Reliability and Availability – Must be there when we need it!
4.
Must be large enough to have an impact (MWh).
5.
Speed of response to an event - Can it be controlled and dispatched – risk
to system
6.
Grid stability impacts – voltage and protection dynamic interactions
7.
Permitting – ease and time to obtain permits
8.
Footprint – How Big? Can it be sited at customer’s premise or substation
9.
Must breakthrough utility Technology bias – just build more lines and
substations – new technology is too risky and subject to disallowance.
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