Use‐Cases and Business Cases: Utilities Prerequisite for Acceptanceof Electricity Storage
byPramod Kulkarni
California Energy Commission
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What Can Electricity Storage Do?
• Reliably store electrical energy in mechanical, chemical, magnetic or electrical form to be retrieved at a different time from its generation for operational needs.
• Availability from seconds to days, and from a kWh to hundreds of MWh makes electricity portable across time and distance and allows for multiple forms of ownerships and business models.
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Types of Energy Storage
Electrochemical
• Lead Acid Battery
• Sodium‐Sulfur Battery (NaS)
• Flow Batteries
Vanadium Redox Zinc Bromine Battery
• Nickel Cadmium (NiCd) Battery
• Nickel Metal Hydride (NiMh)
• Lithium Ion (Li‐ion) Battery
Non‐Electrochemical
• Pumped Hydroelectric
• Compressed Air Energy Storage (CAES)
• Flywheel
• Ultra‐Capacitor
• Superconducting Magnetic Energy Storage (SMES)
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Storage Technologies’ Capabilities Vary By Power Rating & Duration
PumpedStorage
1 MW1 kW 100 kW 10 MW 100 MW
Max
imum
Dis
char
ge
Tim
e
High Energy Fly Wheels
Power Rating
Compressed-AirFlow Batteries
NAS Battery
Metal-Air Batteries
Advanced Batteries
Lead-Acid Batteries
Super Capacitors
Seco
nds
10 kW
Low Energy Fly Wheels SMES
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ELECTRIC ENERGY STORAGE FOR VARIOUS UTILITY FUNCTIONS(All Boundaries Of Regions Displayed Are Approximate)
1.0
0.1
10
100
0.1 Cycle 10 Cycle 5 Hour
Power Quality
TemporaryPower Interruptions
15 Minutes
1000
Voltage Support byAbsorption or Injection ofVAR
Peak ShavingT&D Deferral
Load LevelingRamping
1 Hour15 Second
Spinning Reserve
Renewables- Wind- Solar
Community EnergyStorage &
Roof-top Solar Mgmt
Peak LoadManagement
Congestion Management
BlackStartFrequency
Regulation
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Examples of Energy Storage Technologies
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Drivers for Utility Interest in Energy Storage
• Efficient integration of renewable resources
• Peak load management
• Distribution reliability & asset management
• Improve & maintain power quality
• Defer distribution or transmission system upgrades
• Transmission & distribution congestion
• Need for capacity, energy & ancillary services7
Peak Shaving Benefit of Battery StorageSource: American Electric Power Presentation to Southwest Distribution
Exchange, May 2009
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Load Leveling Using A Sodium Sulfur Battery Source: American Electric Power Presentation to Southwest Distribution Exchange, May 2009
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Different Value Streams Affect Business CaseSource: American Electric Power Presentation to Southwest Distribution Exchange, May
2009
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Utility Approach to Energy Storage • Use Case: Possible technology use in the context of operational needs & demonstration that a storage system performs in utility’s operational setting.
• Business Case: If a use‐case is established, a storage system must make an economic sense in the business context unique to utility’s circumstances.
– Benefit/Cost ratio compared to other options.
– Benefits analysis is difficult due to multiple benefit streams, some not easily quantifiable. Uncertain costs. Methodologies are evolving.
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Southern California Edison (SCE) Business Case Approach
• An application specific benefits/cost analysis
• Identify operational Issues
• Develop practical application
• Match application to storage technology
• Evaluate application/technology pair for B/C Ratio
• Sensitivity analysis for different scenarios
Source: www.edison.com/files/WhitePaper_SCEsApproachtoEvaluatingEnergyStorage.pdfAuthor: Johannes Ritterhausen, et al. May 2011
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Operational Uses of Storage TechnologiesSource: SCE Approach to Evaluating Energy Storage. Author: Johannes Ritterhausen, et al. May 2011
Grid Location Minimum Duration of Output Energy (Continuous)
Short (< 2 minutes) Medium (2min‐1 hr) Long (1 hour +)
Generation (1) Provide spinning or non spinning power
(4) Provide capacity
(2) Provide ramping (5) Firm renewable output
(3) Provide frequency regulation services 6) Shift Energy
(10)Smooth intermittent resource output(11) Improve short‐duration
performance(12) Provide System Inertia
(7) Avoid dump energy, minimum load issues
(13) Avoid Congestion feeTransmission
Distribution (16) Improve Power Quality ( 15) Improve system reliability
(17) Defer System Upgrade
(18) Mitigate Outages
(19) Integrate Intermittent distributed generation
End User (21) Maintain power quality
(20) Optimize retail rates 13
Rationale for Application Specific Business Case Analysis
• It defines role of storage, its location in the system & mode of operation
• Informs value of benefits accrued and location
• Helps asses cost and performance target for technologies
• Impact of storage ownership and business models in context of Benefit/cost ratio
• Points to needed regulatory action, rules & forum for discussion
Source: SCE Approach to Evaluating Energy Storage. Author: Johannes Ritterhausen, et al. May 2011
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Implementation of Application Specific Business Case Analysis
Applications selected, matched with technology & calculated NPV of the benefits streams.
(1) Off‐to‐on peak intermittent energy shifting, firming
(2) On‐peak intermittent energy smoothing & shaping
(3) Ancillary service provision
(4) Transportable distribution‐level outage mitigation
(5)Peak load shifting downstream of distribution system
(6) End‐user retail rate optimizationSource: SCE Approach to Evaluating Energy Storage. Author: Johannes Ritterhausen, et al. May 2011
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Results of Application Based AnalysisSCE matched application to specific storage technology. Quantified the net present value (NPV) of total lifetime benefits (application value streams) and costs (technology installed and operating)
Application Storage Characteristics & Value Streams
Current Benefit cost Ratio
ChangedAssumptions B/C in 2020
Off‐to‐on peak intermittent energy shifting firming
300 MW pumped hydro, transmission avoided cost, arbitrage
0.5 1.1
On‐peak intermittent energy smoothing & shaping
10 MW, 30 min flywheel, Market rents from smoothing
0.1 1.1
Ancillary service provision 20 MW, 30 minute flywheel, ramping regulation up/down, spinning reserves
0.3 1.1
Transportable distribution‐level outage mitigation
Transportable 2 MW, 4 hour Li‐ion battery, Defer T&D upgrade , arbitrage
0.2 1.1
Peak shaving downstream of the “secondary” distribution
25 kW, 4 hour Li‐ion battery; Defer T&D system upgrade, arbitrage
0.4 1.5
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Observations from SCE Methodology
• 2020 B/C ratio encouraging depending on storage costs reductions & different revenue streams based on favorable regulations & market rents.
• Business case analysis & outcome depend on assumptions and utilities’ unique conditions.
• Applied to a different utility some other applications could be more cost‐effective than for SCE. Several have strong business cases.
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CASE Study of a Utility in Western US*• Applications included in benefits analysis:
– Distribution Deferral
– PV Load Shifting
– Customer‐side Energy Management
• Application analyzed under different ownerships, net benefits varied depending on how benefits were aggregated and allocated (to utility, customer or entire system)
*Case study conducted by the Electric Power Research Institute for members only. Data and
other details are proprietary the Electric Power Research Institute
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CASE Study of a Utility in Western US*
Battery storage by location for benefit analysis:– Community energy storage based on customer‐side of meter (battery)
– Storage in neighborhood but on utility side of meter (several small batteries)
– Storage at a substation using transportable battery system (battery)
*Case study conducted by the Electric Power Research Institute for members only. Data and other details are proprietary
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Value Associated with Storage Locations on the Grid
Source: American Electric Power Presentation to Southwest Distribution Exchange, May 2009
120/240 V69 kV 4 to 34 kV 480 V138 kV345 kV765 kV
Storage Value
Devaluators:• Limited Value to Customer• High Security Risk• Does not remove Grid Constraints
Devaluators:• Aesthetics• O&M?
CES(Community Energy Storage
(Substation Battery)
CentralGeneration
Load
Distribution circuits appear to offer most value for hosting storage
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Methodology for Assessing Business CaseBenefits Streams Calculated:
– Distribution Deferral– System Capacity – Regulation (up & down)– Reliability– Lowering Customer’s electricity bill
• Based on time‐of‐use rates & demand charges.
– Avoided cost of mitigating photovoltaic on grid.
Net Present Value of aggregated benefits (when applicable) compared to $/kWh storage cost
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Findings of the Case Study
• Substation based mobile battery storage had the highest NPV due to value of capacity and regulation realized by the utility
• Distribution deferral had little value due to preponderance of networked circuits
• Aggregation of customer‐side storage had system wide benefits but not under utility ownership.
*Case study conducted by the Electric Power Research Institute for members only. Data and other details are proprietary
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General Observations on Business Cases for Energy Storage
• Utilities have similar use‐cases, yet a business case for same application varies with utility specific situation; and is often location specific within the same utility
• Current storage costs from $1500/kWh to $3,500/kWh; cost‐effectiveness is function of cost of alternative(s) for the same application
• Storage costs are coming down. Externalities such as greenhouse gas mitigation, cost of fossil fuel and ISO/RTO & regulators giving proper credit for storage would make for a stronger business case.
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