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Introduction and Basic Cocepts
MECH3023: Building Energy Management & Control Systemshttp://www.hku.hk/bse/mech3023/
Dr. Sam C M HuiDepartment of Mechanical Engineering
The University of Hong Kong
E-mail: cmhui@hku.hk
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Contents
Study Guide
Overview
Control Fundamentals
System Concepts
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Study Guide
Main topics taught by Dr. Sam C. M. Hui
Basic Concepts
Hardware Components System Architecture
Networking
Communication Protocols
Control Strategies and Applications
Intelligent Buildings
See also Course Schedule
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Study Guide
Course content
Lectures and Assigned Readings
Examination
Course Website (http://www.hku.hk/bse/mech3023/)
Related courses
BBSE3004 Air Conditioning and Refrigeration MECH3005 Building Services
Assessment
Practical work (15%); Examination (85%)
http://www.hku.hk/bse/mech3023/http://www.hku.hk/bse/mech3023/8/11/2019 mech3023_0405-01_intro
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Study Guide
Resources for learning
Lecture notes
Reference books
Web links
Journal papers
Attendance to lectures is IMPORTANT
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Overview
Terminology
Building automation system (BAS)
Building management system (BMS)
Building energy management system (BEMS)
Energy management system (EMS)
Central control monitoring system (CCMS) Direct digital control (DDC)
Intelligent building (IB)
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Overview
Building services systems being controlled
HVAC (heating, ventilation & air-conditioning)
Fire services Plumbing & drainage
Electrical installations
Lighting Lifts & escalators
Security & communication
Special systems e.g. medical gas
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Lower energy cost Lower operations cost
Increase flexibility Ensure quality building
environment
Building Energy Management System
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Overview
Why use BEMS?
Growing complexity of building systems
Demand for more efficient building operation Need to save energy & operating costs
Need to increase flexibility & reliability
Improve indoor environment & productivity
Connect BEMS to major building equipment to Control air conditioning & lighting to save energy
Monitor all equipment to improve efficiency of operations
personnel & minimise equipment down time
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Overview
Factors affecting energy use in buildings
Thermal efficiency of building envelope
Thermal insulation, air tightness, solar gains
Requirements of indoor environment
Temperature schedule, ventilation needs, humidity
control, indoor air quality, lighting, lifts, etc.
Processes within the building
IT or office equipment, industrial processes
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Overview
Early development history
1st generation (1950s)
Remote monitoring panels with sensors & switches (hard wire)
2nd generation (1960s)
Electronic low voltage circuits
3rd generation (1960s-1973)
Multiplexed systems with minicomputer stations
4rd generation (1983)
Microcomputer-based systems
5th generation (1987)
Direct digital control (DDC) with microprocessor & software
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Overview
Recent trends
Conventional system (front end based)
Central computer + dumb field panels
Distributed intelligence BEMS
Central computer + field panels (limited standalone)
Fully distributed BEMS
Multifunction microprocessor close to the equipment
(complete standalone)
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BEMS
Fire alarm system
Security system Telecom system
Lift control system
Office/Home
automation
system
Potential overlap of microprocessor-based systems
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Control Fundamentals
Pneumatic controls
Traditional form of control used in buildings
Pneumatic controllers, sensors & actuators Electronic devices may be integrated
Direct digital control (DDC)
Entered the HVAC industry in late 1980s
Use a programmable microprocessor as controller
Direct = microprocessor is directly in the control loop
Digital = control is accomplished by the digitalelectronics
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Control Fundamentals
Basic elements
Sensor
Measure some variables, e.g. temperature
Controller
Process & compute an output signal
Controlled device
Act to change the output of the load
Typical situation for BEMS
Close loop systems (w/ feedback loop)
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Discharge air control system
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Control Fundamentals
Control modes
Two position (on/off) control
Proportional control Integral control
Proportional + integral (PI) control
Proportional + integral + derivative (PID) control Technical terms
Set points, dead band, throttling range, offset,
proportional band, integral time
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Thermostat model of proportional control with deadband
and dual throttling range
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Control Fundamentals
Choice of control mode
Degree of accuracy required; amount of offset
Type of load changes expected Including amplitude, frequency & duration
System characteristics
Such as no. & duration of time lags, speed of response
Expected start-up situation
In general, use the SIMPLEST mode
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Application Control mode
Space temperature P
Mixed air temperature PI
Coil discharge temperature PI
Chiller discharge temperature PI
Air flow PI (use wide proportional band &
short integral time), PID
Fan static pressure PI (some may require PID)
Humidity P, possibly PI for tight control
Dewpoint P, possibly PI for tight control
Recommended control modes for HVAC system
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Control Fundamentals
Other advanced control techniques
Adaptive control
Controllers learn the plant/system operatingconditions by observing the response to disturbances
Fuzzy logic
Based on a set of rules of the IF-THEN type, expressed
in near natural language
Neural network
Reproduce the way the human brain leans by
experience; non-linear processing
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System Concepts
Typical procedure for a BEMS project
Initial concept
Information retrieval
Candidate buildings & system selection
Field survey
Design
Prepare contract documents
Contract
Installation & training
Acceptance
Operation & maintenance
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System Concepts
Common BEMS software functions
Programmed start/stop: occupancy schedules
Optimised start/stop: based on indoor/outdoortemperatures
Thermostat temperature setback/setup
Economizer control: use free cooling Reset of air, chilled water or hot water temps.
Chiller or boiler optimisation
Demand control: reduce peak electrical loads
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System Concepts
Common BEMS software functions (contd)
Duty cycling: turn off equipment for some time to
reduce energy use Monitoring/alarm: logging conditions, on-
off/high-low alarms, run time, energy use, etc.
Fire notification: parallel with fire alarm system
Security: alarm, door switches, etc.
Card access: card readers, exit doors, door
contacts, etc.
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Management
level
Control level
Operational level
Field level
Outstation, discrete controller
Sensor, switch, etc.
Central station
Central station communication
via gateways
Levels of control in building energy management system
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Components
of a energy
management
system (EMS)
with direct
digital control
(DDC)
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Modern building automation systems
LonMark
BACnet
Protocols
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System Concepts
Future development potentials
World Wide Web (Web-based controls)
Communication standards (BACnet & LonMark) Wireless revolution
Integration of communication & automation
Emerging issues
Green building environment
Evolution of DDC to facility wide control
Occupant connectivity & control
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Integration controls network from different buildings
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Wireless revolution
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Further Reading
Building automation: an overview of centralcontrol and monitoring systems
http://www.nrc.ca/irc/cbd/cbd214e.html
AutomatedBuildings
http://www.automatedbuildings.com/
11 Revolutionary Automation Trends
http://www.automatedbuildings.com/news/may01/articles/trends/trends.htm
http://www.nrc.ca/irc/cbd/cbd214e.htmlhttp://www.automatedbuildings.com/http://www.automatedbuildings.com/news/may01/articles/trends/trends.htmhttp://www.automatedbuildings.com/news/may01/articles/trends/trends.htmhttp://www.automatedbuildings.com/news/may01/articles/trends/trends.htmhttp://www.automatedbuildings.com/news/may01/articles/trends/trends.htmhttp://www.automatedbuildings.com/http://www.nrc.ca/irc/cbd/cbd214e.htmlRecommended