Load Management System with Intermittent Power on the Grid Ruth Kemsley CEng MIMechE MIEE [email protected] Econnect Ventures Ltd.

Load Management System with Intermittent Power on the Grid

Ruth KemsleyCEng MIMechE MIEE

[email protected]

Econnect Ventures Ltd

• 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 background

• 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 objectives

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

• 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

Conclusions from preliminary evaluation

• 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

Minimising energy export from embedded generation

System tasks

DECIDE WHETHER

TO INCREASE SITE LOAD

MEASURE POWER EXPORT

SEND SIGNAL TO LOAD CONTROLLERS

SWITCH LOADON OR OFF

SWITCH LOADON OR OFF

SWITCH LOADON OR OFF

System components

POWER MEASUREMENT

UNIT

COMMUNICATIONSUNIT

LC

LC

ADD LOAD OR REMOVE LOAD

1

2

3

SEND“ON” OR “OFF” SIGNAL

GRID SUPPLYPOWER IMPORT OR EXPORT

FINDHORN DISTRIBUTION NETWORK

CURRENT AND VOLTAGE MEASUREMENT

IMMERSIONHEATER

SPACEHEATER

SPACEHEATER

“TRAFFICLIGHT”

LC

LC

CONTROL UNIT

LOAD CONTROLLERS ANDCONTROLLABLE LOADS

(SMALL PERCENTAGE OF TOTAL SITE LOAD)

POWER IMPORT OR EXPORT, kW

4

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 designPrototype equipment

GRID SUPPLYPOWER IMPORT OR EXPORT

POWER MEASUREMENT

UNIT

COMMUNICATIONSUNIT

LOAD CONTROLLER

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