Building Energy Saving through Optimization and Life-cycle … on ICC... · 2010-03-22 · Building Energy Saving through Optimization and Life-cycle Commissioning –The Approach

Building Energy Saving through Optimization

and Life-cycle Commissioning

– The Approach and Experiences in ICC

CPD Technical Seminar, CIBSE (Hong Kong Branch), ASHRAE

(Hong Kong Chapter) and HKIE (BS division)

17, March 2010, Hong Kong

Shengwei Wang (王盛衛王盛衛王盛衛王盛衛)

Chair Professor of Building Services Engineering

Department of Building Services Engineering

The Hong Kong Polytechnic University

A Simple View of Energy Saving Potentials for Building A Simple View of Energy Saving Potentials for Building A Simple View of Energy Saving Potentials for Building A Simple View of Energy Saving Potentials for Building

HVAC&R Systems in OperationHVAC&R Systems in OperationHVAC&R Systems in OperationHVAC&R Systems in Operation

Building Energy SavingBuilding Energy SavingBuilding Energy SavingBuilding Energy Saving

HVAC&R SystemsEnergy Saving Potential

System, component and BAS

commissioning and diagnosis

20~30%Saving Potential

10~20%Saving Potential

System operation and

Control Optimization

- HVAC, lighting, lift, …

Design: Configuration,

Components selection, etc.

Outline of Presentation

• Introduction to ICC building systems;

• Our roles in ICC project;

• The concept of “commissioning”

• Examples of commissioning efforts at design,

installation, T&C and operation stages;

• Saving Energy through Control Optimization

control strategies implemented

examples of control strategies

• Summary of energy benefits

• Summary of experiences in ICC

International Finance Centre (ICC)International Finance Centre (ICC)

490 m

118 F

Six-star Hotel

High-rank

commercial

office

Commercial center and

basement

Floor Area:

Hotel 70,000 (m2)

Office 286,000 (m2)

Commercial center

67,000 (m2)

Gross 440,000 (m2)

EVAPORATOR EVAPORATOR EVAPORATOR EVAPORATOREVAPORATOR

COOLING

TOWER 2

COOLING

TOWER 4

COOLING

TOWER 3

COOLING

TOWER 6COOLING

TOWER 5

COOLING

TOWER 8COOLING

TOWER 7

COOLING

TOWER 1

COOLING

TOWER 11COOLING

TOWER 9

COOLING

TOWER 10

EVAPORAROR

WCC-06a-01

(2040 Ton)

PCHWP-06-01

FROM OFFICCE FLOORS(7-41)

TO OFFICE FLOORS(7-41)

HX HX HX HX HX HX HX

PCHWP-06-02 PCHWP-06-03 PCHWP-06-04 PCHWP-06-05 PCHWP-06-06

WCC-06a-02

(2040 Ton)

WCC-06a-04

(2040 Ton)WCC-06a-03

(2040 Ton)

WCC-06a-05

(2040 Ton)WCC-06a-06

(2040 Ton)

CDWP-06-01 CDWP-06-02 CDWP-06-04CDWP-06-03 CDWP-06-05 CDWP-06-06

CT-06a-01 CT-06a-02 CT-06a-03 CT-06a-04 CT-06a-05 CT-06a-06 CTA-06a-01 CTA-06a-02 CTA-06a-03 CTA-06a-04 CTA-06a-05G

Cooling tower circuit

A

F

D

CA

B

E

B

D

C

E

F

G

Secondary water circuit for Zone 1


Secondary water circuit for Zone

3 and Zone 4

Primary water circuit

Chiller circuit

Cooling water circuit

(S-B)

FROM PODIUM & BASEMENT

TO PODIUM & BASEMENT

HX HX

(S-B)

(S-B)

(S-B)

FROM OFFICE FLOORS (43-77)

TO OFFICE FLOORS (43-77)

(S-B)

CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER

HXHXHX

TO OFFICE FLOORSS (79-98)


(S-B)

(S-B)

SCHWP-42-01 to 03SCHWP-42-04 to 06

SCHWP-78-01 to 03

PCHWP-78-03PCHWP-78-01 PCHWP-78-02

PCHWP-42-01 PCHWP-42-02 PCHWP-42-03 PCHWP-42-04 PCHWP-42-05 PCHWP-42-06 PCHWP-42-07

SCHWP-06-06 to 09

SCHWP-06-03 to 05

SCHWP-06-01 to 02

SCHWP-06-10 to 12

CTA Towers (without heating coil) CTB Towers (with heating coil)

Our Roles in ICC ProjectOur Roles in ICC ProjectOur Roles in ICC ProjectOur Roles in ICC ProjectOur Roles in ICC ProjectOur Roles in ICC ProjectOur Roles in ICC ProjectOur Roles in ICC Project

� Independent Energy Consultant (Independent Commissioning Agent)

� Developer of HVAC Energy Optimization System (EOS) and Energy Performance Diagnosis System (EPDS)

� Annual electricity consumption of the central

air-conditioning system is about 50,000,000 kWh

Chiller Pump Cooling Tower Fan PAU Fan AHU Fan Total

Number 6 36 11 29 152 234

Rated Power (kW ) 1346 152

Total load (kW ) 8076 4374 1672 513 4600 19235

Percentage 41.99% 22.74% 8.69% 2.67% 23.91%

� Summary of design power load of main HVAC

equipments

Principle of Commissioning Principle of Commissioning

((校核校核校核校核校核校核校核校核//校校校校校校校校校校校校校校校校及及及及及及及及改進改進改進改進改進改進改進改進))

� Commissioning is the process throughout the

whole building lifecycle rather that one-off task.

� Commissioning is a valid means for

improving energy performance of

buildings and HVAC systems

throughout the building life cycle.

Categories of CommissioningCategories of Commissioning

� Initial commissioning: Applied to a production of a new

building and/or an installation of new systems.

� Retro-commissioning: The first time commissioning

implemented in an existing building in which a documented

commissioning was not implemented before.

� Re-commissioning: Implemented after the initial

commissioning or the retro-commissioning when the owner hopes to

verify, improve and document the performance of building systems.

� On-going/continuous commissioning: Conducted

continually for the purposes of maintaining, improving and

optimizing the performance of building systems after the initial

commissioning or the retro-commissioning.

� Commissioning is the process throughout the whole building lifecycle rather that one-off task as conventional “Test and Commissioning”.It is performed regularly throughout the whole building lifecycle from early planning, design, construction and installation to operationfor ensuring that systems are designed, installed, functionally tested and capable of being operated and maintained properly.

LifeLife--CCycle ycle CCommissioningommissioning� The building profession in Northern American and European countries has been promoting the new concept of life-cycle “Commissioning” and role of “Independent Commissioning Agent” over the last few years.

� Commissioning is an effective means for improving energy performance of buildings and HVAC systems throughout the building life cycle.• An average payback period for commissioning of new buildings is 4.8 years in United States.

• Average energy cost saving for periodical commissioning of existing building is 15%.

� Commissioning is the process throughout the whole building lifecycle rather that one-off task as conventional “Test and Commissioning”.It is performed regularly throughout the whole building lifecycle from early planning, design, construction and installation to operationfor ensuring that systems are designed, installed, functionally tested and capable of being operated and maintained properly.

LifeLife--CCycle ycle CCommissioningommissioning� The building profession in Northern American and European countries has been promoting the new concept of life-cycle “Commissioning” and role of “Independent Commissioning Agent” over the last few years.

� Commissioning is an effective means for improving energy performance of buildings and HVAC systems throughout the building life cycle.• An average payback period for commissioning of new buildings is 4.8 years in United States.

• Average energy cost saving for periodical commissioning of existing building is 15%.

ICC project is one of the very first full scale

trial of the new concept of “Commissioning”

and “Independent Commissioning Agent” in

very large and complex building system in

Asia. It is a very attractive contribution to the

IEA Research programme Annex 47.

Commissioning and examples of Commissioning and examples of Commissioning and examples of Commissioning and examples of

efforts at design, installation, T&C efforts at design, installation, T&C efforts at design, installation, T&C efforts at design, installation, T&C

and operation stagesand operation stagesand operation stagesand operation stages

Development of Virtual Building System - Dynamic

simulation platform of the complex HVACR system

Chiller One

TYPE 23

Chiller Four

TYPE 23

Chiller Six

TYPE 23

Chiller Two

TYPE 23

Chiller Three

TYPE 23

Chiller Five

TYPE 23

CTA Three

TYPE 1

CTB One

TYPE 2

CTA Five

TYPE 1

CTA Two

TYPE 1

CTA Four

TYPE 1

CTB Two

TYPE 2

CTA One

TYPE 1

CTB Five

TYPE 2

CTB Four

TYPE 2

CTB Three

TYPE 2

CTA Six

TYPE 1

Cooling tower controller

TYPE 3&54&55

Mixing after chiller condensers

TYPE 4

Mixing after cooling towers

TYPE 5

Data Reader

TYPE 9

Chiller sequence controller

TYPE 50

Mixing & Bypass

TYPE 67

Return pipe

TYPE 31 Supply pipe

TYPE 31

Pump & network

TYPE 12

AHUs

TYPE 63

PID control

TYPE 42

Pump sequence

TYPE 39

HX modeling&mixingTYPE 41

HX sequence

TYPE 39

PID control

TYPE 43

Tao,i

Load & status of AHUs

TYPE 49

Pump & network

TYPE 13

AHUs

TYPE 21

PD optimizerTYPE 7

PID control

TYPE 20

Pump sequence

TYPE 39

PID control

TYPE 43

Tao,i

VPi

PDset

Pump & network

TYPE 14

PID control

TYPE 43

PID control

TYPE 43

Mixing

TYPE 48

Tw,out

HX modeling&mixing TYPE 36

HX sequence

TYPE 39

Pump & network

TYPE 17

AHUs

TYPE 63

PID control

TYPE 42

Pump sequence

TYPE 39

PID control

TYPE 43

Tao,i

Pump & network

TYPE 15

PID control

TYPE 43

PID control

TYPE 43

Mixing & bypassTYPE 19

Tw,o

ut


TYPE 35

Pump & network

TYPE 18

AHUs

TYPE 63

PID control

TYPE 42

PID control

TYPE 43

Tao,i


HX sequence

TYPE 39

Pump & network

TYPE 16

PID control

TYPE 43

PID control

TYPE 43


PD optimizerTYPE 6

VPi

PDset

PD optimizerTYPE 8

Pump sequence

TYPE 39

PDset

PD optimizerTYPE 62

PDset

Mixing

TYPE 47

Mixing

TYPE 47

Tw,sup

Mw,i

On/Off

of AHUs

Mw &

PD

mea

s

Npu

Freq

On/Off

of AHUs

Mw,i

Mw &

PD

mea

s

Freq

Npu

Nhx

Tw,sup

Tw,in &Mw

Tw,sup

Mw,set

Mw,measFreq

Mw,i

VPi

Npu

Freq

VPi

Mw,i

Freq

Npu

Mw &

PD

mea

s

Nhx

Mw

Tw,sup&MwMw,set

Mw,measFreqNhx

Load

Nhx

Nhx

Tw,sup

Tw,out

Ma,i&

Ta,in

Ma,i&Ta,inMa,i&Ta,in

On/Off of AHUs

On/Off of AHUsOn/Off of AHUs

Mw & Tw,rtn Mw & Tw,rtn

On/Off of AHUs Ma,i&Ta,in

On/Off

of AHUs

On/Off of AHUs

Load

Tw,sup

Tw,rtn

& M

w

Tw,rtn & Mw

Tw,in

Mw &

Tw,in

Tw,sup & MwMw & Tw,rtn

Nhx

Mw

Mw,&

w,in

Tw,rtn

& M

w

Mw,measFreq

Mw,set

Mw

Nch On/Off On/Off On/Off On/Off On/Off On/Off

Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out

Tsup

Tsu

p

Mw,tot&

Trtn

Nch Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out

Tw,cd,in

Mw,tot&Tw,ct,inTw,cd,outOn/Off,i&Freq,i

Zone 2

Zone 1Zone 3&4

NumberN:

Valve positionVP:

Pressure differentialPD:

FrequencyFreq:

Cooling loadLoad:

Water or air flow rateM:

TemperatureT:

Component type numberTYPE XX:

NumberN:

Valve positionVP:


FrequencyFreq:

Cooling loadLoad:


TemperatureT:


Supplysup:Heat exchangerhx:

wb:

ct:

cd:

rtn:

in:

ao:

meas:

w:

Subscript

Wet-bulb

Cooling tower

Condenser

Return

Inlet

Air outlet

Measurement

Water

Set-pointset:

Chillerch:

Dry-bulbdb:

Outletout:

Pumppu:

Totaltot:

Individuali:

Aira:


wb:

ct:

cd:

rtn:

in:

ao:

meas:

w:

Subscript

Wet-bulb

Cooling tower

Condenser

Return

Inlet

Air outlet

Measurement

Water

Set-pointset:

Chillerch:

Dry-bulbdb:

Outletout:

Pumppu:

Totaltot:

Individuali:

Aira:

Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & MwTw,out & MwTw,out & MwTw,out & Mw Tw,out & MwTw,out & Mw Tw,out & Mw

Mw,tot&Tw,ct,out

Pump sequence

TYPE 39

NpuMw

Pump sequence

TYPE 39

Npu

Mw

Mixing

TYPE 60

Tw,rtn & Mw,tot

Twb&

Tdb

Tw,out,i

Mixing

TYPE 61

Mw,tot & Tw,rtn

Zone airflow rates

Zone 1Zone 1Zone 1Zone 1

Zone 2Zone 2Zone 2Zone 2Zones 3&4Zones 3&4Zones 3&4Zones 3&4

Development of Virtual Building System - Dynamic

simulation platform of the complex HVACR system

Chiller One

TYPE 23

Chiller Four

TYPE 23

Chiller Six

TYPE 23

Chiller Two

TYPE 23

Chiller Three

TYPE 23

Chiller Five

TYPE 23

CTA Three

TYPE 1

CTB One

TYPE 2

CTA Five

TYPE 1

CTA Two

TYPE 1

CTA Four

TYPE 1

CTB Two

TYPE 2

CTA One

TYPE 1

CTB Five

TYPE 2

CTB Four

TYPE 2

CTB Three

TYPE 2

CTA Six

TYPE 1

Cooling tower controller

TYPE 3&54&55

Mixing after chiller condensers

TYPE 4

Mixing after cooling towers

TYPE 5

Data Reader

TYPE 9

Chiller sequence controller

TYPE 50

Mixing & Bypass

TYPE 67

Return pipe

TYPE 31 Supply pipe

TYPE 31

Pump & network

TYPE 12

AHUs

TYPE 63

PID control

TYPE 42

Pump sequence

TYPE 39

HX modeling&mixingTYPE 41

HX sequence

TYPE 39

PID control

TYPE 43

Tao,i


TYPE 49

Pump & network

TYPE 13

AHUs

TYPE 21

PD optimizerTYPE 7

PID control

TYPE 20

Pump sequence

TYPE 39

PID control

TYPE 43

Tao,i

VPi

PDset

Pump & network

TYPE 14

PID control

TYPE 43

PID control

TYPE 43

Mixing

TYPE 48

Tw,out


HX sequence

TYPE 39

Pump & network

TYPE 17

AHUs

TYPE 63

PID control

TYPE 42

Pump sequence

TYPE 39

PID control

TYPE 43

Tao,i

Pump & network

TYPE 15

PID control

TYPE 43

PID control

TYPE 43


Tw,o

ut


TYPE 35

Pump & network

TYPE 18

AHUs

TYPE 63

PID control

TYPE 42

PID control

TYPE 43

Tao,i


HX sequence

TYPE 39

Pump & network

TYPE 16

PID control

TYPE 43

PID control

TYPE 43


PD optimizerTYPE 6

VPi

PDset

PD optimizerTYPE 8

Pump sequence

TYPE 39

PDset

PD optimizerTYPE 62

PDset

Mixing

TYPE 47

Mixing

TYPE 47

Tw,sup

Mw,i

On/Off

of AHUs

Mw &

PD

mea

s

Npu

Freq

On/Off

of AHUs

Mw,i

Mw &

PD

mea

s

Freq

Npu

Nhx

Tw,sup

Tw,in &Mw

Tw,sup

Mw,set

Mw,measFreq

Mw,i

VPi

Npu

Freq

VPi

Mw,i

Freq

Npu

Mw &

PD

mea

s

Nhx

Mw

Tw,sup&MwMw,set

Mw,measFreqNhx

Load

Nhx

Nhx

Tw,sup

Tw,out

Ma,i&

Ta,in

Ma,i&Ta,inMa,i&Ta,in

On/Off of AHUs

On/Off of AHUsOn/Off of AHUs

Mw & Tw,rtn Mw & Tw,rtn

On/Off of AHUs Ma,i&Ta,in

On/Off

of AHUs

On/Off of AHUs

Load

Tw,sup

Tw,rtn

& M

w

Tw,rtn & Mw

Tw,in

Mw &

Tw,in

Tw,sup & MwMw & Tw,rtn

Nhx

Mw

Mw,&

w,in

Tw,rtn

& M

w

Mw,measFreq

Mw,set

Mw

Nch On/Off On/Off On/Off On/Off On/Off On/Off

Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out

Tsup

Tsu

p

Mw,tot&

Trtn

Nch Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out

Tw,cd,in

Mw,tot&Tw,ct,inTw,cd,outOn/Off,i&Freq,i

Zone 2

Zone 1Zone 3&4

NumberN:

Valve positionVP:


FrequencyFreq:

Cooling loadLoad:


TemperatureT:


NumberN:

Valve positionVP:


FrequencyFreq:

Cooling loadLoad:


TemperatureT:



wb:

ct:

cd:

rtn:

in:

ao:

meas:

w:

Subscript

Wet-bulb

Cooling tower

Condenser

Return

Inlet

Air outlet

Measurement

Water

Set-pointset:

Chillerch:

Dry-bulbdb:

Outletout:

Pumppu:

Totaltot:

Individuali:

Aira:


wb:

ct:

cd:

rtn:

in:

ao:

meas:

w:

Subscript

Wet-bulb

Cooling tower

Condenser

Return

Inlet

Air outlet

Measurement

Water

Set-pointset:

Chillerch:

Dry-bulbdb:

Outletout:

Pumppu:

Totaltot:

Individuali:

Aira:

Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & MwTw,out & MwTw,out & MwTw,out & Mw Tw,out & MwTw,out & Mw Tw,out & Mw

Mw,tot&Tw,ct,out

Pump sequence

TYPE 39

NpuMw

Pump sequence

TYPE 39

Npu

Mw

Mixing

TYPE 60

Tw,rtn & Mw,tot

Twb&

Tdb

Tw,out,i

Mixing

TYPE 61

Mw,tot & Tw,rtn

Zone airflow rates

Zone 1Zone 1Zone 1Zone 1

Zone 2Zone 2Zone 2Zone 2Zones 3&4Zones 3&4Zones 3&4Zones 3&4

Virtual

Building

System

Simulated

(updated throughout

the entire process)

• Verification the system configuration and component selection including the chiller system, water system (primary/secondary system), heat rejection system (cooling towers), fresh air system etc.

• Verification of the metering system for proper local control, and the original proposed control logics at the design stage.

• Proposal of additional metering system for implementing supervisory control strategies and diagnosis strategies and related facilities for implementing these strategies ( This is a typical energy-saving implementation from the earlier design and installation phase)

Design CommissioningDesign CommissioningThe design commissioning mainly concerns the

future operation and control performance of HVAC

systems, and includes:

HX-42 HX-42 HX-42 HX-42 HX-42 HX-42 HX-42

(S-B)



(S-B)

HX-78HX-78HX-78



(S-B)

(S-B)


SCHWP-78-01 to 03

SCHWP-06-06 to 09

To Z

on

e 3&

4

Fro

m Z

one 3

&4

Flow meter

Bypass valve

EVAPORATOR EVAPORATOR EVAPORATOR EVAPORATOREVAPORATOREVAPORAROR

WCC-06a-01

(2040 Ton)

PCHWP-06-01

FROM OFFICCE FLOORS(7-41)

TO OFFICE FLOORS(7-41)

HX-42

PCHWP-06-02 PCHWP-06-03 PCHWP-06-04 PCHWP-06-05 PCHWP-06-06

WCC-06a-02

(2040 Ton)

WCC-06a-04

(2040 Ton)WCC-06a-03

(2040 Ton)

WCC-06a-05

(2040 Ton)WCC-06a-06

(2040 Ton)

CDWP-06-01 CDWP-06-02 CDWP-06-04CDWP-06-03 CDWP-06-05 CDWP-06-06

A

F

D

CA

B

E

B

D

C

E

F



Secondary water circuit for Zone

3 and Zone 4

Primary water circuit

Chiller circuit

Cooling water circuit

(S-B)

FROM PODIUM & BASEMENT

TO PODIUM & BASEMENT

HX-06

(S-B)

(S-B)

(S-B)



(S-B)

CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER

HX-78HX-78HX-78



(S-B)

(S-B)


SCHWP-78-01 to 03

PCHWP-78-03PCHWP-78-01 PCHWP-78-02

PCHWP-42-01 PCHWP-42-02 PCHWP-42-03 PCHWP-42-04 PCHWP-42-05 PCHWP-42-06 PCHWP-42-07

SCHWP-06-06 to 09

SCHWP-06-03 to 05

SCHWP-06-01 to 02

SCHWP-06-10 to 12

To cooling towersFrom cooling towers

HX-42 HX-42 HX-42 HX-42 HX-42 HX-42

HX-06

Original SystemOriginal SystemOriginal SystemOriginal System Revised Revised Revised Revised SystemSystemSystemSystem(operation mode)(operation mode)(operation mode)(operation mode)

System Design VerificationSystem Design Verification --Secondary water loop systems Secondary water loop systems of 3rd and 4of 3rd and 4thth zoneszones

Primary pumps are omitted

Comparison between Two systemsComparison between Two systems

0

200

400

600

800

1000

1200

1400

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time (h )

Pump power (

kW)

Original design

Alternative design

Annual Pump Energy Saving is

1M kWh

Typical sunny-

summer day

• A very special cooling tower with large heat rejection capacity and a very large dimension (4*10*9)

• High pressure drop through fill packing and silencer

• Energy consumption is about 3.6 million a year with intended two-stage control

• Energy consumption is about 2.6 million a year with intended VFD control from PolyU

• However, energy consumption will increase greatly to about 5.0 million when single-stage is used

From chiller

To chiller

Pressure drop

300 Pa 50 Pa100 Pa

Silencer

Fill packing

System Design VerificationSystem Design Verification--Cooling tower systemCooling tower system

Annual saving potential of using variable speed

cooling towers is 2.4M compared with that

using constant speed towers. It is 1.4M

compared with that using two speed towers.

Example of CO2 Sensor

Installation

CO2CO2 CO2CO2

CO2CO2CO2CO2

CO2CO2

CO2CO2CO2CO2

CO2CO2

CO2CO2

CO2CO2

CO2CO2

CO2CO2CO2CO2

CO2CO2

CO2CO2CO2CO2

CO2CO2

CO2CO2

AHU

AHU

KaishingIC

BB

Morgan

Stanley

Empty

Empty

EmptyCO2CO2

CO2CO2

Flow stations

200

250

300

350

400

450

500

550

600

650

700

9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00

Sample time (h)

CO2 concentration (ppm)

Fresh air (Measured) Return air (Measured)

Supply air (Measured) Supply air (Calculated)

After calibration

200

250

300

350

400

450

500

550

600

650

700

9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00

Simple time (h)

CO2 concentration (ppm)

Fresh air (Measured) Return air (Measured)

Supply air (Measured) Supply air (Calculated)

Measurement accuracy of CO2 sensors directly affects

indoor air quality and energy performance of air side

system, which is therefore essential for implementing

optimal ventilation control strategy.

Before calibration

� CO2 sensor calibration and commissioning

Example of air flow

station Installation

∆P

PAvAQ ∆⋅=⋅= 2

Cooling tower site operation issueCooling tower site operation issue• We suggest all the cooling tower fans are equipped with

VFD for significant energy savings, and the variable frequency range is from 50 Hz to 25 Hz at least.

• At the test stage, the manufacture stated the minimum frequency is 37 Hz for cooling requirement of the inside motor.

• The manufacture finally confirmed the minimum frequency is 20 Hz ensuring the normal operation of the fan.

This low frequency increases the This low frequency increases the This low frequency increases the This low frequency increases the

energy saving potential greatly energy saving potential greatly energy saving potential greatly energy saving potential greatly

at partial load conditions !at partial load conditions !at partial load conditions !at partial load conditions !

Cooling tower site operation issueCooling tower site operation issue• We suggest all the cooling tower fans are equipped with

VFD for significant energy savings, and the variable frequency range is from 50 Hz to 25 Hz at least.

• At the test stage, the manufacture stated the minimum frequency is 37 Hz for cooling requirement of the inside motor.

• The manufacture finally confirmed the minimum frequency is 20 Hz ensuring the normal operation of the fan.

This low frequency increases the This low frequency increases the This low frequency increases the This low frequency increases the

energy saving potential greatly energy saving potential greatly energy saving potential greatly energy saving potential greatly

at partial load conditions !at partial load conditions !at partial load conditions !at partial load conditions !

The savings is about 607,000 kWh , 2.86% of

annual energy consumption of chillers and

cooling towers due to the lower frequency limit.

Low Delta-T Central Plant Syndrome

� The inability to sufficiently

load chillers;

� Excess water flow demand;

� An increase in pump energy;

� Either an increase in chiller

energy or a failure to meet

cooling load; etc.

� Nearly all large primary-secondary chilled water

systems suffer from low chilled water temperature

difference, known as low delta-T central plant

syndrome, resulting in inefficient operation.

� When the low delta-T syndrome exists, a series of

operation problems will be resulted

-500

-400

-300

-200

-100

0

100

200

300

400

500

0 12 24 36 48 60 72 84 96 108 120 132 144 156 168

Sample time (hour)

Water flow rate (L/s)

0

1

2

3

4

5

6

7

8

Chiller number and Temp. difference

Chiller operating number

Water flow

Temp. difference after decouple

Low Delta-T Central Plant Syndrome

� The inability to sufficiently

load chillers;

� Excess water flow demand;

� An increase in pump energy;

� Either an increase in chiller

energy or a failure to meet

cooling load; etc.

� Nearly all large primary-secondary chilled water

systems suffer from low chilled water temperature

difference, known as low delta-T central plant

syndrome, resulting in inefficient operation.

� When the low delta-T syndrome exists, a series of

operation problems will be resulted

-500

-400

-300

-200

-100

0

100

200

300

400

500

0 12 24 36 48 60 72 84 96 108 120 132 144 156 168

Sample time (hour)

Water flow rate (L/s)

0

1

2

3

4

5

6

7

8

Chiller number and Temp. difference

Chiller operating number

Water flow

Temp. difference after decouple

Some causes can be avoided, but some

of them cannot be avoided in some

applications.

Each phase in the life cycle of air-conditioning

systems, including design, equipment selection,

commissioning, operation and maintenance,

may result in low delta-T problems.

� Potential solutions

� The use of variable primary-only systems;

� The use of pressure-independent modulating

control valves;

� The use of bypass check valves;

� Advanced control and operation strategies.

System Improvement by using a Check ValveSystem Improvement by using a Check Valve

� Experimental validation prior to a check valve is really installed

� by using a ‘conceptual’ check valve in the chiller decouple ---- through fully closing down one of the isolation valves in the chiller decouple when the deficit flow was observed.

CHILLER 06CHILLER 06

FM

AHUAHU

Secondary water

circuit for Zone 1

Secondary water

circuit for Zone 2

Secondary water

circuit for Zone 3&4

Primary

pumps 01-06

Secondary

Pumps 01-02






AHUAHU

AHUAHU

AHUAHU

AHUAHU

AHUAHU

Secondary

pumps 03-05Secondary

pumps 06-08

AHUAHU

AHUAHU

AHUAHU

Check valve

� Summary of experimental results

-250

-200

-150

-100

-50

0

50

10:09:59

10:24:58

10:42:56

10:58:57

11:10:59

11:23:01

11:39:01

12:03:03

12:21:03

12:35:00

13:00:01

13:14:04

13:29:01

13:43:58

13:56:59

14:13:58

14:38:58

14:52:04

15:02:58

15:16:57

15:33:04

15:47:59

16:06:59

16:23:01

Time

Deficit flow (L/S)

Closing the valve in

the decouple

Reopen the valve

in the decouple

5.5 °C set-point 5.0 °C set-point

4000

4500

5000

5500

6000

6500

7000

10:17:58

10:36:58

10:51:59

11:06:59

11:19:04

11:32:56

11:54:58

12:14:56

12:29:58

12:48:56

13:07:58

13:24:59

13:37:59

13:50:59

14:08:59

14:34:00

14:44:56

14:58:58

15:10:56

15:29:01

15:39:00

15:57:59

16:15:58

Time

Cooling load of chiller(kW)

Closing the valve

in the decouple

Reopen the valve in

the decouple

Reset supply water

temp. set point from

5.5°C to 5 °C

12

12.5

13

13.5

14

14.5

15

15.5

16

10:00:58

10:17:58

10:36:58

10:51:59

11:06:59

11:19:04

11:32:56

11:54:58

12:14:56

12:29:58

12:48:56

13:07:58

13:24:59

13:37:59

13:50:59

14:08:59

14:34:00

14:44:56

14:58:58

15:10:56

15:29:01

15:39:00

15:57:59

16:15:58

Time

Outlet air temp. of AHU 1 in L15 (°C)

Closing the valve

in the decouple

Reopen the valve in

the decouple

Reset supply water

temp. set point from

5.5°C to 5 °C

0

200

400

600

800

1000

1200

1400

1600

1800

11:19:56

11:30:02

11:42:58

11:52:59

12:05:56

12:16:58

12:32:03

12:46:56

12:57:00

13:07:04

13:17:59

13:31:59

13:48:03

13:56:01

14:09:57

14:28:03

14:39:56

14:48:00

14:57:59

Time

Total power (kW)

Using 'conceptual' check valvewith similar weather condition

by without using the check

valve

Test procedure Cooling energy of chillers

Supply air temperature Energy consumptions

Annual energy saving potential by using the check

valve in ICC is about 325,800 kWh when compared

to that without using the check valve.

Simplified

Models

Optimization

Strategies

Performance

Models

Diagnosis

Strategies

Performance

Prediction

Performance

Prediction

IBmanager

System Control Optimizer

Diagnostic Tool

Communication

Interfa

ces

Virtual Plants

Simulated

Online performance testing of control Online performance testing of control optimizers and diagnostic tools on the optimizers and diagnostic tools on the

simulated virtual systemsimulated virtual systemControl optimizers and diagnostic tools should be tested on the virtual

systems prior to site implementation

Saving Energy through

Control Optimization

Optimization for HVAC&R systems

Optimization allows the of HVAC&R systems

provide expected quality of services (comfort and

health environment) with reduced energy

consumption by means of :

• Optimizing design configuration;

• Optimizing the selection and sizing;

• Optimal operation and control.

Optimal control strategies for central Optimal control strategies for central airair--conditioning systemsconditioning systems

� Chiller sequence, optimal start

Optimal chiller sequence - based on a more accurate cooling load

prediction using data fusion method, and considering demand limiting

Adaptive online strategy for optimal start - based on simplified sub-

system dynamic models

� Ventilation strategy for multi-zone air-conditioning

system

Optimal ventilation control strategy - based on ventilation needs of

individual zones and the energy benefits of fresh air intake

� Peak demand limiting and global electricity cost

management

Optimal control strategies for central Optimal control strategies for central airair--conditioning systems (contconditioning systems (cont’’d)d)

� Chilled water system optimization

Optimal pressure differential set point reset strategy

Optimal pump sequence logic

Optimal heat exchanger sequence logic

Optimal control strategy for pumps in the cold water side of heat

exchangers

Optimal chilled water supply temperature set-point reset strategy

� Cooling water system optimization

Optimal condenser inlet water temperature set point reset strategy

Optimal cooling tower sequence

Optimal control of condenser Optimal control of condenser

cooling water systemscooling water systems

Optimal control of condenser cooling water systemsOptimal control of condenser cooling water systems (cont(cont’’d) d)

� Formulation of the optimal control strategy

• Objective function

++== ∑∑ ∑

== =

CTBch CTA

cdwcdw

N

j

iCTB

N

k

N

i

iCTAkchT

totT

WWWWJ1

,

1 1

,,minminsup,,sup,,

• The overall structure of the optimal control strategyOnline measurements

and control signals

Measurement filter

Simplified chiller

model

Simplified CTA and

CTB tower models

Define the search ranges

for Tw,cd,sup and Nct

Supervisory control strategy

Optimal control settings & cost

(Tw,cd,sup, NCTA , NCTB , Freq , Pch+Pct ) Optimization process

Cost estimation & optimization algorithm

FreqNCTA

Chiller plant control system

(BAS)

Interface

Performance prediction

Twb, Qev, Nch Qev, Nch, Tw,ev,in

Tw,cd,sup

Tw,cd,out

Nch &Twb

Tw,cd,sup& Nct

PchTw,cd,sup, NCTA, NCTB, Ma,, Pct , Freq

NCTB Tw,cd,sup

It consists of :

Performance predictor Performance predictor Performance predictor Performance predictor

Cost estimator Cost estimator Cost estimator Cost estimator

Optimization toolOptimization toolOptimization toolOptimization tool

Supervisory strategySupervisory strategySupervisory strategySupervisory strategy

It is designed using a model-based method


• Optimization tool ---HQS (hybrid quick search) method

++=

desev

ev

wb

on

cdwQ

QhThhT

,

210

,

sup,,

TTTTT on

cdwcdw

on

cdw ∆+≤≤∆− .

sup,,sup,,

,

sup,,

Search range

+Δx

-Δx

Low limit Search center (near optimal)

Upper limit

Time

Control setting

• Parameters to be optimized

� The condenser water supply temperature set-point

� The number of CTA towers operating

� The number of CTB towers operating

• Operating constraints

� basic energy and mass balances (i.e., flow, heat, etc.)

� mechanical limitations (i.e., fan speed, temperature, etc.)

• Evaluation of control accuracy and computation performance


Seasons Items

Spring Mild-summer Sunny-summer

Typical working conditions

Qload (kW) 25520.11 31213.61 37547.74

Nch 4 5 6

Tw,ev,in (°C) 9.92 9.82 9.83

Tw,ev,out (°C) 5.50 5.50 5.50

Tdb (°C) 22.55 27.76 33.66

Twb (°C) 15.86 20.11 24.99

Mw,cd (L/s) 410.10 410.10 410.10

Items Tools

HQS GA HQS GA HQS GA

Optimization results

Wch (kW) 3628.07 3644.90 5004.21 4994.37 6794.24 6799.59

Wct (kW) 285.74 268.91 386.11 396.08 538.74 533.42

Wch+Wct (kW) 3913.81 3913.81 5390.32 5390.45 7332.98 7333.01

Optimal Tw,cd,sup (°C) 21.85 21.88 26.65 26.64 31.80 31.80

NCTA 6 6 6 6 6 6

NCTB 5 5 5 5 5 5

Freq (Hz) 25.99 25.35 29.33 29.62 33.39 33.26 Computational cost(s) 0.152 3.610 0.144 3.512 0.134 3.589

The computational cost saving is 96.0%

� Performance tests and evaluation

� Comparison between the HQS and GA-based strategies

20.00

23.00

26.00

29.00

32.00

35.00

38.00

0 2 4 6 8 10 12 14 16 18 20 22 24

Time (h )

Temperature (°C)

Dry-bulb Temp.

Wet-bulb Temp.

Optimal Temp. set-point

Near optimal Temp. set-point

Upper limit of set-point

Low limit of set-point

14.00

17.00

20.00

23.00

26.00

29.00

32.00

0 2 4 6 8 10 12 14 16 18 20 22 24

Time (h )

Temperature (

°C)

Dry-bulb Temp.

Wet-bulb Temp.

Optimal Temp. set-point

Near optimal Temp. set-point

Upper limit of set-point

Low limit of set-point

Optimal temperature set-point

Near-optimal temperature set-point

• Evaluation of the Energy Performance


� Comparison of condenser water supply temperature set-

points using HQS-based strategy and near optimal strategy

Spring caseSpring caseSpring caseSpring case SunnySunnySunnySunny----summer casesummer casesummer casesummer case


� Comparison of the hourly-based power consumptions using

different control methods

-30

-20

-10

0

10

20

30

40

0 2 4 6 8 10 12 14 16 18 20 22 24

Time (h )

Power difference ( k

W)

Optimal strategy

Near optimal strategy

-30

0

30

60

90

120

150

180

210

0 2 4 6 8 10 12 14 16 18 20 22 24

Time (h )Power difference ( k

W)

Optimal strategy


HQS-based strategy


Fixed approach

Spring caseSpring caseSpring caseSpring case SunnySunnySunnySunny----summer casesummer casesummer casesummer case

Fixed

approach


� Comparison of daily and annual power consumptions of the

condenser cooling water system using different control methods

Fixed approach Near optimal strategy HQS-based strategy Operation

Strategies Wct+Wch

(kWh)

Wct+Wch

(kWh)

Saving

(kWh)

Saving

(%) Wct+Wch

(kWh)

Saving

(kWh)

Saving

(%)

Spring 51,738 51,623 114.53 0.221 51,404 334.30 0.646

Mild-summer 71,289 70,668 621.49 0.872 70,560 729.36 1.023

Sunny-

summer 91,653 90,878 775.44 0.846 90,356 1,297.50 1.416

• Daily power consumptions

• Annual power consumptions

Operation

strategies

Wch

(kWh)

Wct

(kWh)

Wcd,pu

(kWh) Wtot

(kWh) Saving (kWh)

Saving (%)

Fixed approach 18,464,812 1,882,583 4,210,690 24,558,085 --- ---

Near optimal 18,715,458 1,501,701 4,210,690 24,427,849 130,236 0.530

HQS-based 18,715,134 1,448,765 4,210,690 24,374,589 183,496 0.747

Operating Condition Power Consumption

Cooling

Water

Temp Set-

point

Cooling

Tower

Number

Cooling

Tower

Freq

Chiller

Power

Cooling

Tower

Power

Total

Power Difference

Operation modes

°C - Hz kW kW kW kW %

Reference 22.7 3 26.51 856.2 59.1 915.35 -- --

First-level warning 21.3 3 30.74 836.2 93.0 929.2 14.0 1.5

Second-level warming 20.1 3 35.52 819.9 145.9 965.8 50.6 5.5

Using heat pumps 22.7 3CT+1HP 26.51 856.2 59.1 1215.2 300 32.8

Plume Control and Energy Benefits

At first-level warning, increase airflow rate

by 20% when plume potential is marginal

At second-level warning, increase airflow

by 40% when plume potential is high

Start heating using heat pumps when

visual plume is observed

Decision

maker

Platform for predicting

plume occurring possibility

Normal operation when there is

no predicted plume occurs

Additional energy consumption for

plume control could be reduced from

32.8% to 5.5% or 1.5% at low Load

Chiller Plant Sequencing Control

of Enhanced Robustness

Using Data Fusion Technique

Types of chiller sequencing control

� Return chilled water temperature based sequencing

control

� Bypass flow based sequencing control

� Direct power based sequencing control

� Total cooling load based sequencing control

Background (1)

Chiller sequencing control

� Aims to determine how many and which chillers are to be

put into operation according to building cooling load

� Plays a significant role for building energy efficiency

Total cooling load based chiller sequencing control

� Building cooling load measurement

�Maximum cooling capacity

� Optimal number of chillers to be put into operation

Nc = φ(Qcl, Qmax)

Background (2)

Problems

� Building cooling load cannot be measured accurately

� Chiller maximum cooling capacity vary with the

operating conditions

Fused Cooling Load Measurement

Cooling load measurement

� Direct measurement of building cooling load

Qdm = cpwρwMw(Tw,rtn-Tw,sup)

where cpw is the water specific thermal capacity; ρw is the

water density; Mw is water flow rate; Tw,rtn,Tw,sup are

chilled water return/supply temp.

� Indirect measurement of building cooling load

Qim = f(Pcom,Tcd,Tev)

where f is the chiller inverse model; Pcom is chiller power

consumption; Tcd,Tev are chiller condensing/evaporating

temperature

Robust building cooling load measurement technique

� Data fusion to merge “Direct measurement” and

“Indirect measurement” improving the accuracy and

reliability of building cooling load measurement

Chiller

Model 1Chiller

Model n

Central Chilling Plant

Chiller

Model 1

Chiller

Model nDirect

measurement

Data Fusion

Engine

Pcom,1 Tev,1,Tcd,1

+

Pcom,n,Tev,n,Tcd,n

Trtn Mw

Tsup

Qdm

Qim,1Qim,n

Qf

γf

…

Advanced soft measurement system

Robust Chiller Sequencing Control Building Cooling Load

Measurement Technique

Central chilling

plant

Indirect

Measurement

Data Fusion

EngineParameters

setting

Periodical

analysis

Alarming

subsystem

Chiller sequencing

control

Database

Building Automation

System

Direct

measurement

Robust Cooling Load

Measurement

From cooling source

HX

HX

Temperature controller

Differential pressure controller

Temperature

set-pointPressure

differential set-point

To coolingsource

Secondary side of HX Primary side of HX


Temperature

set-point

MM

ΔP

TT

TT

To terminal

units

From terminal units

Modulating

valves

MM

HX

HX

TT TM


Water flowcontroller

Temperature

set-point

Water flow

set-point

To terminal

units

From terminal units

Secondary side of HX Primary side of HX

TM

From cooling source

To coolingsource

� Original implemented strategy --- differential pressure controller by resorting to the modulating valve

� Proposed strategy --- cascade controller without using any modulating valve

Optimal Control of Variable Speed Pumps

� Speed control of pumps distributing water to

heat exchangers

� Site practically test showed that the proposed strategy can provide stable and reliable control. Compared to original implemented strategy, about 22.0% savings for pumps before heat exchangers in Zone 1 was achieved.

� Due to the low load of Zone 1 in ICC at current stage, a simulation test of annual energy savings by using PolyU strategy is performed.

Energy consumption (kWh)

Pumps Number

(standby) Original

strategy

(kWh)

Alternative

Strategy

(kWh)

Saving

(kWh)

Primary pumps in Zone 1 1(1) 528,008 456,132 71,876

Primary pumps for Zones 3&4 3(1) 921,235 795,830 125,405

Primary pumps in Zone 4 2(1) 401,008 346,420 54,588

Total saving of the primary pumps 251,869

Energy saving of primary pumps before

heat exchanges due to the use of

PolyU strategy is about 250000 kWh.

� Performance test and evaluation

Static pressure

Outdoor air

controller

Adaptive DCV

strategy

Model-based

outdoor air flow rate

Control strategy

P

Static pressure

controller

Static pressure

set point

Set point

The 1st floor

The 7th floor

………….

Optimal Outdoor air Ventilation Control

COP

HHMMC

COP

QWW

k

rtn

k

out

k

setoutk

setout

k

voutdoor

fant

)(,

,cos

−⋅+⋅=+=

Parameter identification of the fan model

Parameter estimators

Real process of the multi-zone

air conditioning system

Cost function

estimator

Iterative

algorithm

Model-based

predictor

Supervisor Constrains

Optimal set point Range of set point

Set point trailsLeast Square Algorithm

Outdoor Air Optimal Scheme

Energy-based outdoor air flow rate set-point

resetting scheme

� Site Implementation and Validation of Optimal Ventilation Strategy for Fresh Air Control

� CO2-based occupancy detection

� Site counting the number of occupancy in the typical floor

� Comparison between counted and predicted occupancies

0

10

20

30

40

50

60

70

80

90

100

8:30 9:30 10:30 11:30 12:30 13:30 14:30 15:30 16:30 17:30 18:30

Time (hour)

Num

ber of occupancy

Counted

Predicted

Demand-controlled Ventilation control

� Practically test and validation of the ventilation control strategy

Tests aimed at validating the actual operational performance of the

ventilation control strategy and also for verifying whether the control

settings provided by PolyU strategy can be properly sent to the ATC

system and further be used in practical control.

+45.8-+58.9-Total energy saving (%)

2050.13780.22203.55366.7Total energy consumption (kWh)

1725.62985.61915.24754.4Fresh air cooling energy

consumption (kWh)

324.5794.60288.3612.29Primary fan energy consumption

(kWh)

Summer case

(PolyU strategy applied to all

floors in Zone 2)

+59.2-+52.9-Primary fan energy saving (%)


(kWh)Estimation case

(PolyU strategy applied to all

floors in Zone 2)

2.814.963.047.90Energy saved due to fresh air

cooling (kWh)

+4.11-+0.70-Primary fan energy saving (%)


(kWh)Site test case

(PolyU strategy only applied to

typical floor)

(Nov., 2009)

PolyUFixed flowPolyUFixed flow

AHU2AHU1Control strategyStudy cases

About 662,000 kWh energy savings can be

achieved by using PolyU ventilation control

strategy for all floors per year in Zone 2!

Site Implementation of The

Control Strategies

Implementation Strategy of Optimal Control and Diagnosis

Tools in ICC

LAN

VAV BoxAHU PAU

Supply air control

optimizer

Fresh air control

optimizer

Fresh air

terminal

ATC

Decision Supervisor

Building

Management

System

DiagnosisOptimizer

Overall KVA, etc. Control

Parameters

Chiller Plant Control Optimizer

and Diagnosis

Control Setting

from PolyU

Control Setting

from ATC

Manual

Control

Control Setting

from PolyU

Control Setting

from ATC

Manual

Control

BA

CnetS

DK

IBmanager

Intelligent building management system

-- based on IBmanager� IBmanager is an open and integrated management platform. It

employs standard middleware and web-service technologies to

support the integration and interoperation among distributed BASs.

Summary of Energy Benefits• 1,000,000 kWh energy consumption is saved due to the

modification on the secondary water loops of Zone 3 & 4;

• 2,360,000 kWh , (about 5.1% of annual energy consumption of chillers and cooling towers) of the cooling system can be saving due to the change from single speed to variable speed using VFD.

• 607,000 kWh , (about 2.8% of annual energy consumption of chillers and cooling towers) of the cooling system will be wasted when the lowest frequency is limited at 37 Hz.

• 3, 500,000 kWh (about 7%) of the total energy consumption of HVAC system) can be saved using PoyUcontrol strategies based on the original design;






Saving by Control OptimizationSaving by Control OptimizationSaving by Control OptimizationSaving by Control Optimization – compared with the

case when the HVAC system operates correctly

according to the original design intend.

Saving by CommissioningSaving by CommissioningSaving by CommissioningSaving by Commissioning (Improving the system (Improving the system (Improving the system (Improving the system configuration and selectionconfiguration and selectionconfiguration and selectionconfiguration and selection – compared with the

original design.






Saving by Control OptimizationSaving by Control OptimizationSaving by Control OptimizationSaving by Control Optimization – compared with the

case when the HVAC system operates correctly

according to the original design intend.

Saving by CommissioningSaving by CommissioningSaving by CommissioningSaving by Commissioning (Improving the system (Improving the system (Improving the system (Improving the system configuration and selectionconfiguration and selectionconfiguration and selectionconfiguration and selection – compared with the

original design.

The annual total energy

saving is about 7.0M kWh !

Summary of Experience in ICC• Significant energy saving can be achieved by

allowing the system as good as the design intention by identifying and correcting the errors at different stages;

• Significant energy saving can be achieved by making the system better than the design intention by enhancing and optimizing the systems at different stages;

• The involvement of a professional energy consultant (commissioning agent) does not introduce troubles to the building construction project, but instead it facilitates different parties involved to support each other to do their jobs smoothly and correctly.

Documents

Building Energy Saving through Optimization and Life-cycle … on ICC... · 2010-03-22 · Building Energy Saving through Optimization and Life-cycle Commissioning –The Approach