Load Management System with Intermittent Power on the Grid

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Load Management System with Intermittent Power on
the Grid
Econnect Ventures Ltd
Ruth Kemsley CEng MIMechE MIEE ruth.kemsley_at_econne
ct.com
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Project background

• Econnects long experience with demand-side
  management
• distributed load control devices
• providing system (frequency) control on small
  islanded networks with intermittent and limited
  generation sources
• Desire to develop these devices and associated
  system design techniques to assist grid
  integration of renewables using DSM
• Need to evaluate potential markets and target
  technology development accordingly

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Project objectives

• Identify contractual requirements and commercial
  benefits of different load management systems
• under the Renewables Obligation and electricity
  trading arrangements
• Model economic benefits of load management to
  customers with intermittent generation on site
• Develop low cost load management system
• incorporating communication technologies and
  switching devices
• to maximise renewable energy use on a
  demonstration site
• Identify associated social and psychological
  aspects

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Project tasks

• Identified and evaluated four potential control
  strategies for a load management system on the
  distribution network
• A solution to voltage rise problems caused by
  distributed generation
• Ensuring zero export from a site with renewable
  generation
• Avoiding load demand discrepancies
• Creating an additional market for renewable
  energy
• Selected one strategy suitable for application at
  the test site
• Demonstrated technical aspects of load management
  equipment
• Investigated the social aspects of the load
  management strategy

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Project partners

• Econnect
• analysed potential DSM strategies
• carried out computer modelling work
• designed, developed, installed and tested load
  management equipment
• Findhorn Foundation Community
• provided a test site and assisted with
  implementation
• De Montfort University
• carried out social impact studies

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Conclusions from preliminary evaluation

• Mitigating voltage rise from embedded generation
• technically achievable
• benefits of avoiding voltage-related constraints
  4 x implementation cost in case study
• Maximising on-site usage of renewables on a site
  with embedded generation and loads
• technically possible to ensure close to zero
  power export to the grid
• quick payback of implementation cost possible
• Avoiding demand discrepancies between actual and
  contractual volumes of load
• possible only to reduce, rather than avoid,
  demand discrepancies
• savings 5 x installation cost over 20 years in
  case study
• Creation of additional demand for renewable
  energy
• complex system with high capital cost of
  duplicated heating equipment
• possible to reduce energy bills and increase
  generation / supply companies revenues
• benefits less marked

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Minimising energy export from embedded generation

• Technique selected for demonstration at Findhorn
  Foundation Community
• 75kW wind turbine with plans for 600kW more wind
  capacity (at time of project inception)
• Extensive low voltage distribution network,
  administered by FFC
• Power export from site rare, but will increase
  significantly when new wind turbines added
• Installation aimed to demonstrate load management
  technology

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System tasks
DECIDE WHETHER TO INCREASE SITE LOAD
MEASURE POWER EXPORT
SEND SIGNAL TO LOAD CONTROLLERS
SWITCH LOAD ON OR OFF
SWITCH LOAD ON OR OFF
SWITCH LOAD ON OR OFF
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System components
IMMERSION HEATER
LOAD CONTROLLERS AND CONTROLLABLE LOADS (SMALL
PERCENTAGE OF TOTAL SITE LOAD)
FINDHORN DISTRIBUTION NETWORK
LC
GRID SUPPLY POWER IMPORT OR EXPORT
SPACE HEATER
LC
CURRENT AND VOLTAGE MEASUREMENT
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LC
POWER MEASUREMENT UNIT
LC
1
SPACE HEATER
SEND ON OR OFF SIGNAL
COMMUNICATIONS UNIT
POWER IMPORT OR EXPORT, kW
TRAFFIC LIGHT
3
CONTROL UNIT
2
ADD LOAD OR REMOVE LOAD
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Engineering challenges

• Measurement of imported / exported power
• Signal communications needs to be robust
• powerline carrier demonstrated here via overhead
  line and underground cable
• low power radio
• communications cables
• internet
• Control algorithm for deciding when to switch
  devices
• need to avoid increasing import from grid!
• need to avoid switching large blocks of load
  simultaneously

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Social challenges

• Selecting suitable loads for automatic management
• Identifying and communicating benefits to
  consumers of surrendering control over their
  loads
• traffic light idea popular with the community
  voluntary load switching
• test loads were mostly in central community
  buildings
• Ensuring no loss of quality or reliability of
  supply
• Integrating system with tariff structure to
  incentivise take-up

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System designPrototype equipment
POWER MEASUREMENT UNIT
LOAD CONTROLLER
GRID SUPPLY POWER IMPORT OR EXPORT
COMMUNICATIONS UNIT
LOAD CONTROLLER
SUBSTATION CENTRAL CONTROLLER
LOAD CONTROLLER / TRAFFIC LIGHT
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Simulation results

• Key to developing control algorithms and
  identifying benefits
• Example results
• assume 72kWh per day provided by 40kW of
  deferrable load
• without control timeswitch controls 40kW just
  before midnight
• with control 40kW switched on and off
  throughout the day depending on wind availability
• saving in this instance 19kWh depends on wind
  profile and switching speed

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Test results

• Demonstrated
• low-cost power measurement system
• simple PIC-based control algorithm
• powerline carrier communications over three phase
  low voltage network around test site (including
  cable and overhead lines)

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Conclusions

• Identified several beneficial applications of
  load management in context of renewable energy
• Extended application of Econnects load
  controllers from off-grid systems to
  grid-connected operation
• Developed a load management system for
  implementation
• Demonstrated successful technical operation of
  component parts
• Identified issues which will make a system
  practicable and successful