Power System Reliability: Spinning Reserve From Responsive Load

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Power System ReliabilitySpinning Reserve From
Responsive Load

• Brendan Kirby
• Oak Ridge National Laboratory
• 865-576-1768 kirbybj_at_ornl.gov

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Conceptually, Responsive Load and Distributed
Generation Could Greatly Enhance Bulk Power
System Reliability

• Good match between some loads inherent response
  capability and power systems physical
  reliability requirements
• Preconceptions about what response is easiest are
  often wrong
• Advances in communications and control technology
  make it possible to exploit load response
• Market and reliability rules need to be
  reexamined
• Our goal should be to enhance reliability, not to
  blindly embrace existing rules
• Responsive load is the largest underutilized
  reliability asset in North America

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This Presentation Will Focus On The Match Between
Loads Response Capability and The Power Systems
Physical Reliability Needs

• If there is a good match then we should work to
  exploit the reliability benefits
• This may require reexamining market and
  reliability rules
• The Independent System Operator must not favor
  specific commercial participants
• The Independent System Operator should actively
  seek to expand the range, scope, and number of
  reliability resources

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Four Types of Demand Response

• Energy Efficiency programs reduce electricity
  consumption and usually reduce peak demand
• Price Response programs move consumption from day
  to night (real time pricing or time of use)
• Peak Shaving programs require more response
  during peak hours and focus on reducing peaks
  every high-load day
• Reliability Response (contingency response)
  requires the fastest, shortest duration response.
  Response is only required during power system
  events

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A Series of Reserves Respond To Contingency Events
Spinning reserve is typically deployed for 10
minutes or less
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Responsive Loads Better Matched To Spinning
Reserves Than Peak Reduction
Power System Reliability Events Are Fast,
Infrequent and Relatively Short

• Better for the load shorter, less frequent
  disruption (less storage is required)
• Better for the power system faster response,
  more reliable, redundancy, distributed, better
  use of generation
• Better for other loads reduced energy and
  ancillary service prices not all loads need
  respond
• Better for society reduced need for generation
  and transmission

Highest value when load is most available Not
necessarily available in square blocks
Complements energy management, peak shaving, and
price response
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Market Rules Do Not Align Perfectly With
Reliability Needs
Market and reliability rules naturally tend to be
aligned with the capabilities of the dominant
supply technology
Minimum load Minimum run time 10 minute
ramp Minimum off time Start time Inaccurate
response
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Spinning Reserve As Capacity
Spinning reserve is part of the real-time
capacity requirement Supplying spinning reserve
frees other generation to serve load If long-term
spinning reserve payments do not cover the
capital cost of a CT they are probably flawed or
incomplete
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Responsive Load Examples

• Demonstrates a good match between some loads
  response capability and the power systems
  physical reliability needs
• Counterintuitive Responsive load may be better
  suited to the provide the fastest, most
  expensive, and most critical reliability
  services. It may not be best to start with the
  slow, easy demand reduction
• Both large and small responsive loads abound
• Counterintuitive Small loads may be easier to
  exploit and make a larger reliability impact
• Load providing regulation is included because it
  even surprises me

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Spinning Reserves From Large Pumping Loads

• This demonstration with the CA Department of
  Water Resources consist of controlling water
  utility pumps so that they respond to frequency
  deviations and system operator commands for
  contingency events
• Variable speed drives may help increase
  operational flexibility and motor lifetimes

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4 of Total US Load Is Domestic Water Pumping and
Irrigation.Most Have Some Storage.CDWR
Interested In Expanding Opportunities.

• Modeling hourly pump power consumption and power
  system spinning reserve price data to determine
  the potential benefit consider inter-pump
  operating constraints and storage
• Evaluating soft-start capabilities
• Demonstrating response

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CDWR Manages Pumping Loads To Reduce Energy Costs
Spinning Reserve Opportunities and Revenues Are
Still Substantial
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CDWR Pumps Could Supply Significant Spinning
Reserve

• 62 of total California spinning reserve
  requirements
• 100 of California spinning reserve requirements
  for 3292 hours in 2002

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Xcel Energy DemonstrationCabin Creek 2x124MW
Pumps

• At night, when XCEL is pumping up the pond, and
  they already have their efficient combined cycle
  plants running at full load, they must run low
  efficiency peakers as spin. Turning off the
  pumps would be more reliable, and would save
  natural gas.
• Jim Williamson
• Xcel Energy
• 303-808-1849
• An immediate opportunity

• Pumps currently supply operating reserves
• Xcel wants to supply spin from pump load
• Load removed in lt1 minute
• Could be frequency responsive
• Must they have a droop curve?

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Spinning Reserve From Residential and Small
Commercial Thermostats

• Existing Carrier ComfortChoice technology for
  peak reduction
• Faster than generation for spinning reserve
• Spinning reserve capability 3x peak reduction
• Significant monitoring in place

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Can Provide Spinning Reserve While Providing Peak
Reduction
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Substantial Installed Capacity That Could Be
Tested Today
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Communicationsand Control

• Designed for multi-hour peak reduction
• Deployment signal lt90 seconds
• Verification delayed to protect paging system
• Grouping by location, type, or any other criteria
• Customer override allowed for peak shaving, not
  for spinning reserve
• Control can be duty cycle, set point, or turn off
• Monitors temperature, run time, communications
• Customer remote monitoring and control web
  interface

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Spinning Reserves From Commercial Loads

• Supervisory controllers in hospitality industry
  can
• Save energy and can reduce electric demand
• Reduce space heating/cooling in rooms that are
  unoccupied
• Shift electric loads during peak periods for
  short time intervals
• Provide the capability for utilities to satisfy
  spinning reserve(?)

• Easy retrofit Fast deployment
• Developed by Digi-Log Technologies tested
  for energy savings by ORNL
• Spinning reserve is an easy add-on
• Modified to operate by pager signal from utility
• Demo with LIPA and possibly others
• Will work with many technologies

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DigiLog Motel Energy Management System Provides
Spinning Reserve
Spinning Reserve Response

• 80 room Howard Johnson motel
• 1 minute revenue metering
• Pager deployed spinning reserve
• 34kW, 36 load drop in 1 minute

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Interesting Complexities Concerns

• Observability metering and communications
• Statistical response
• Communications
• Forecasting
• Override

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Metering and Communications Requirements

• Givens
• Payment must be tied to actual response
• Deployment signals have to be fast
• One SCADA monitoring system currently performs
  three functions
• Continuous readiness monitoring
• Real-time event monitoring
• Performance monitoring
• How much monitoring is required?
• Statistical resources may not need the individual
  real-time monitoring that deterministic resources
  need
• Redundancy may be better than observability.
• A 5 error in total load forecast can be a
  problem. A 5 error in reserve response may not
  be. Especially if the error is usually in the
  direction of needed response.
• Performance monitoring can be slower
• What information does the system operator really
  require in real-time?

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Communications Requirements Are Asymmetric(This
is a Big Benefit)

• System-to-load communications are typically
  broadcast
• Resource need MW of response desired
• Price
• Deployment respond Now!
• Load-to-system communications are typically
  individual
• Capabilities and price offer
• Performance monitoring conceptually can be
  slower
• Aggregator may help

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Statistical Response May Be Better Than Monitored
Response
Aggregation of many (smaller) individually lower
reliability resources still provides higher
guaranteed response than fewer (larger)
individually higher reliability resources
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Common Concerns Overrides A Benefit and a
Problem, But Less of a Problem for Spinning
Reserve
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Common Concern Stability Will Suffer With
Reduced Inertia

• WECC Analysis Loss of Palo Verde 1
• Case A is the normal base case simulation.
• Case F, normal governors but 300 MW of spin has
  been removed and one Helms pump trips at 59.95
  A better freq. response than the normal base case.

Analysis done by Donald Davies, WECC
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Service Definitions Are Critical

• Most generators do not care if they run for 30
  minutes or 8 hours
• May have minimum run times
• May have emissions limits
• A load may be able to respond for 10-30 minutes
  but not 2 hours
• Can re-arm immediately if not used frequently
• Response capability matches spinning contingency
  reserve much better than demand relief

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Co-Optimization

• Co-Optimization optimizes specific supply
  technologies (generation)
• Co-Optimization does not optimize the reliability
  functions being procured
• Spinning reserve
• Non-spinning reserve
• Supplemental reserve

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Loads May Have The Capability To Provide
Regulation

• Air liquefaction 1,000MW
• Induction ladle metallurgy furnaces 1,000MW
• Gas water pumping with variable speed motor
  drives
• Electrolysis gt14,000MW
• Aluminum 6,500MW
• Chlor-alkali 4,500MW
• Potassium hydroxide 3,000MW
• Magnesium, sodium chlorate, copper
• Always address regulation on an aggregate system
  basis

CPS 12 are the metrics for minute-to-minute
control area balancing Regulation is the most
expensive ancillary service
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Initial Testing of Load Supplying Regulation
Should Begin in December

• The same net energy is consumed the same
  production is met
• Two response options are shown blue may be
  better for both the load and the power system
  than red

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Conclusions

• Communications and control technology now makes
  spinning reserve from load possible
• There are advantages to the responding loads, the
  power system, other customers, and society
• Spinning reserve is a better match for some loads
  than peak reduction
• Rules are important

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Conclusions (continued)

• If a technology does not serve the physical
  reliability needs of the power system we do not
  want it
• If a technology does provide reliability benefits
  but does not meet current market or reliability
  rules we may want to reexamine the rules