8/11/2019 mech3023_0405-01_intro

1/35

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

8/11/2019 mech3023_0405-01_intro

2/35

Contents

Study Guide

Overview

Control Fundamentals

System Concepts

8/11/2019 mech3023_0405-01_intro

3/35

8/11/2019 mech3023_0405-01_intro

4/35

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

8/11/2019 mech3023_0405-01_intro

5/35

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

6/35

Study Guide

Resources for learning

Lecture notes

Reference books

Web links

Journal papers

Attendance to lectures is IMPORTANT

8/11/2019 mech3023_0405-01_intro

7/35

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)

8/11/2019 mech3023_0405-01_intro

8/35

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

8/11/2019 mech3023_0405-01_intro

9/35

Lower energy cost Lower operations cost

Increase flexibility Ensure quality building

environment

Building Energy Management System

8/11/2019 mech3023_0405-01_intro

10/35

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

8/11/2019 mech3023_0405-01_intro

11/35

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

8/11/2019 mech3023_0405-01_intro

12/35

8/11/2019 mech3023_0405-01_intro

13/35

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

8/11/2019 mech3023_0405-01_intro

14/35

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)

8/11/2019 mech3023_0405-01_intro

15/35

BEMS

Fire alarm system

Security system Telecom system

Lift control system

Office/Home

automation

system

Potential overlap of microprocessor-based systems

8/11/2019 mech3023_0405-01_intro

16/35

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

8/11/2019 mech3023_0405-01_intro

17/35

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)

8/11/2019 mech3023_0405-01_intro

18/35

Discharge air control system

8/11/2019 mech3023_0405-01_intro

19/35

8/11/2019 mech3023_0405-01_intro

20/35

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

8/11/2019 mech3023_0405-01_intro

21/35

Thermostat model of proportional control with deadband

and dual throttling range

8/11/2019 mech3023_0405-01_intro

22/35

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

8/11/2019 mech3023_0405-01_intro

23/35

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

8/11/2019 mech3023_0405-01_intro

24/35

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

8/11/2019 mech3023_0405-01_intro

25/35

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

8/11/2019 mech3023_0405-01_intro

26/35

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

8/11/2019 mech3023_0405-01_intro

27/35

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.

8/11/2019 mech3023_0405-01_intro

28/35

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

8/11/2019 mech3023_0405-01_intro

29/35

Components

of a energy

management

system (EMS)

with direct

digital control

(DDC)

8/11/2019 mech3023_0405-01_intro

30/35

Modern building automation systems

LonMark

BACnet

Protocols

8/11/2019 mech3023_0405-01_intro

31/35

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

8/11/2019 mech3023_0405-01_intro

32/35

Integration controls network from different buildings

8/11/2019 mech3023_0405-01_intro

33/35

Wireless revolution

8/11/2019 mech3023_0405-01_intro

34/35

8/11/2019 mech3023_0405-01_intro

35/35

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.html