Econnect Ventures Ltd
Load Management System with Intermittent Power on
the Grid
Ruth Kemsley
CEng MIMechE MIEE
ruth.kemsley@econnect.com
Project background
• Econnect’s 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
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
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
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
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
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
System tasks
MEASURE
POWER
EXPORT
DECIDE
WHETHER
TO INCREASE
SITE LOAD
SEND SIGNAL TO
LOAD CONTROLLERS
SWITCH LOAD
ON OR OFF
SWITCH LOAD
ON OR OFF
SWITCH LOAD
ON OR OFF
System components
GRID SUPPLY
POWER IMPORT OR EXPORT
IMMERSION
LOAD CONTROLLERS AND
HEATER
FINDHORN DISTRIBUTION
CONTROLLABLE LOADS
NETWORK
(SMALL PERCENTAGE OF
LC
TOTAL SITE LOAD)
LC
CURRENT AND VOLTAGE
MEASUREMENT
4
LC
1
POWER IMPORT
OR EXPORT, kW
2
LC
POWER
MEASUREMENT
UNIT
SEND
“ON” OR “OFF” SIGNAL
COMMUNICATIONS
UNIT
CONTROL UNIT
ADD LOAD OR
REMOVE LOAD
3
“TRAFFIC
LIGHT”
SPACE
HEATER
SPACE
HEATER
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
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
System design
Prototype equipment
POWER
MEASUREMENT
GRID
UNITSUPPLY
LOAD
CONTROLLER
POWER IMPORT OR EXPORT
COMMUNICATIONS
UNIT
LOAD
CONTROLLER
SUBSTATION – CENTRAL CONTROLLER
LOAD CONTROLLER / TRAFFIC LIGHT
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
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)
Conclusions
• Identified several beneficial applications of load
management in context of renewable energy
• Extended application of Econnect’s 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