Building Energy Saving through Optimization and Life-cycle Commissioning The Approach and Experiences in ICC

Transcription

1 CPD Technical Seminar, CIBSE (Hong Kong Branch), ASHRAE (Hong Kong Chapter) and HKIE (BS division) 17, March 2010, Hong Kong Building Energy Saving through Optimization and Life-cycle Commissioning The Approach and Experiences in ICC Shengwei Wang ( 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 HVAC&R Systems in Operation - HVAC, lighting, lift, Building Energy Saving Design: Configuration, Components selection, etc. 10~20% Saving Potential HVAC&R Systems Energy Saving Potential 20~30% Saving Potential System operation and Control Optimization System, component and BAS commissioning and diagnosis

2 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) Six-star Hotel Floor Area: 490 m 118 F Hotel 70,000 (m 2 ) Office 286,000 (m 2 ) Commercial center High-rank commercial office 67,000 (m 2 ) Gross 440,000 (m 2 ) Commercial center and basement

3 A HX FROM PODIUM & BASEMENT TO PODIUM & BASEMENT HX (S-B) (S-B) SCHWP to 12 SCHWP to 02 A B C D E F G B Secondary water circuit for Zone 1 Secondary water circuit for Zone 2 Secondary water circuit for Zone 3 and Zone 4 Primary water circuit Chiller circuit Cooling water circuit Cooling tower circuit FROM OFFICCE FLOORS(7-41) TO OFFICE FLOORS(7-41) (S-B) SCHWP to 05 C FROM OFFICE FLOORS (79-98) TO OFFICE FLOORSS (79-98) SCHWP to 03 PCHWP PCHWP PCHWP HX HX HX SCHWP to 06 FROM OFFICE FLOORS (43-77) TO OFFICE FLOORS (43-77) PCHWP PCHWP PCHWP PCHWP PCHWP PCHWP PCHWP HX HX HX HX HX HX HX SCHWP to 09 (S-B) (S-B) (S-B) (S-B) SCHWP to 03 D PCHWP PCHWP PCHWP PCHWP PCHWP PCHWP E EVAPORAROR EVAPORATOR EVAPORATOR EVAPORATOR EVAPORATOR EVAPORATOR WCC-06a-01 (2040 Ton) WCC-06a-02 (2040 Ton) WCC-06a-03 (2040 Ton) WCC-06a-04 (2040 Ton) WCC-06a-05 (2040 Ton) WCC-06a-06 (2040 Ton) CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER F CDWP CDWP CDWP CDWP CDWP CDWP G 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-05 COOLING COOLING COOLING COOLING COOLING COOLING COOLING COOLING COOLING COOLING COOLING TOWER 1 TOWER 2 TOWER 3 TOWER 4 TOWER 5 TOWER 6 TOWER 7 TOWER 8 TOWER 9 TOWER 10 TOWER 11 CTA Towers (without heating coil) CTB Towers (with heating coil) Our Roles in ICC Project Independent Energy Consultant (Independent Commissioning Agent) Developer of HVAC Energy Optimization System (EOS) and Energy Performance Diagnosis System (EPDS)

4 Summary of design power load of main HVAC equipments Chiller Pump Cooling Tower Fan PAU Fan AHU Fan Total Number Rated Power (kw ) Total load (kw ) Percentage 41.99% 22.74% 8.69% 2.67% 23.91% Annual electricity consumption of the central air-conditioning system is about 50,000,000 kwh Principle of Commissioning ( 校核 / 校校及改進 ) 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.

5 Categories 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. Life-Cycle Commissioning 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 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 operation for ensuring that systems are designed, installed, functionally tested and capable of being operated and maintained properly. 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%.

6 Life-Cycle Commissioning 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 ICC project is the is one process of the throughout very first the whole full scale building trial lifecycle of the new rather concept that one-off of Commissioning task as conventional Test and Commissioning. and Independent Commissioning Agent in It is performed regularly throughout the whole building lifecycle from early very planning, large design, and construction complex and building installation system to operation in for ensuring that systems are designed, installed, functionally tested and Asia. capable It of being is a very operated attractive and maintained contribution properly. to the IEA Research programme Annex 47. 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 and examples of efforts at design, installation, T&C and operation stages

7 Development of Virtual Building System - Dynamic simulation platform of the complex HVACR system Tw,sup Mw & PDmeas Data Reader TYPE 9 Twb&Tdb CTA One TYPE 1 Mw,i Pump & network TYPE 13 Freq Pump sequence TYPE 39 HX sequence TYPE 39 Nhx Pump & network TYPE 14 Freq Mw,meas 1 Zone 1 On/Off of AHUs Npu Nhx Mw Mw,set Return pipe TYPE 31 Mw,tot& Trtn Ma,i&Ta,in AHUs TYPE 21 Tao,i TYPE 20 VPi PD optimizer TYPE 7 PDset Mixing TYPE 60 Tw,in &Mw HX modeling &mixing TYPE 41 Tw,out Tsup Cooling tower controller TYPE 3&54&55 Tw,out,i On/Off,i&Freq,i Load & status of AHUs TYPE 49 On/Off of AHUs Tw,sup Mw & PDmeas Zone 2 Mw & Tw,rtn Mw,tot & Tw,rtn Chiller One TYPE 23 On/Off of AHUs Ma,i&Ta,in Pump & network TYPE 12 Freq Pump sequence TYPE 39 Chiller Two TYPE 23 Chiller Three TYPE 23 Chiller Four TYPE 23 Mixing after chiller condensers TYPE 4 Chiller Five TYPE 23 Chiller Six TYPE 23 Chiller sequence controller Nch On/Off On/Off On/Off On/Off On/Off On/Off TYPE 50 Tw,cd,in CTA Two CTA Three CTA Four CTA Five CTA Six CTB One CTB Two CTB Three CTB Four TYPE 1 TYPE 1 TYPE 1 TYPE 1 TYPE 1 TYPE 2 TYPE 2 TYPE 2 TYPE 2 Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Mw,i Npu Mw & Tw,rtn Mixing after cooling towers TYPE 5 Tw,sup On/Off AHUs TYPE 63 Tao,i TYPE 42 VPi PD optimizer TYPE 6 PDset Mixing TYPE 48 of AHUs Mw & Tw,rtn Load Mixing & Bypass TYPE 67 Nhx Load & status of AHUs TYPE 35 On/Off of AHUs Mw,i Pump & network TYPE 18 Freq Pump sequence TYPE 39 HX sequence TYPE 39 Pump & network TYPE 16 Freq Mw,meas Npu Mw Nhx Ma,i&Ta,in AHUs TYPE 63 Tao,i TYPE 42 VPi PD optimizer TYPE 8 PDset Tw,out Mw,set Supply pipe TYPE 31 Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Nch Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Mw,tot&Tw,ct,in Zone airflow rates Zone 2 Mixing TYPE 61 Tw,rtn & Mw,tot Mw,tot&Tw,ct,out Tw,cd,out Pump sequence TYPE 39 Mw Npu Tsup On/Off of AHUs CTB Five TYPE 2 Tw,sup Mw & PDmeas On/Off of AHUs Pump & network TYPE 17 Freq Pump sequence TYPE 39 Mw,set Pump sequence TYPE 39 Tw,rtn & Mw Mixing & bypass Tw,sup & Mw TYPE 45 Ma,i&Ta,in Mw,i AHUs TYPE 63 Tao,i TYPE 42 VPi Npu PD optimizer TYPE 62 PDset Nhx Tw,out Tw,sup &Mw Mixing & bypass TYPE 19 On/Off of AHUs HX sequence Mixing Load TYPE 39 TYPE 47 Nhx Mixing Pump & network HX modeling Mw &mixing TYPE Zones 47 3&4 TYPE 15 TYPE 36 Freq Mw,meas Tw,in HX modeling &mixing TYPE 37 Mw & Tw,in Mw Npu TYPE XX: T: M: Load: Freq: N: VP: PD: Subscript w: meas: ao: in: rtn: cd: ct: hx: wb: Water Air outlet Inlet Return Condenser Number Tw,rtn& Mw Component type number Temperature Water or air flow rate Cooling load Frequency Valve position Pressure differential Measurement Cooling tower Heat exchanger Wet-bulb a: i: tot: pu: set: ch: out: sup: db: Mw,&w,in Tw,rtn& Mw Tw,sup Zone 3&4 Air Individual Total Pump Set-point Chiller Outlet Supply Dry-bulb Development of Virtual Building System - Dynamic simulation platform of the complex HVACR system Tw,sup Mw & PDmeas Mw,i Pump & network TYPE 13 Freq Data Reader TYPE 9 Pump sequence TYPE 39 HX sequence TYPE 39 Nhx Pump & network TYPE 14 Freq Mw,meas 1 Zone 1 On/Off of AHUs Npu Nhx Mw Mw,set Return pipe TYPE 31 Mw,tot& Trtn Ma,i&Ta,in AHUs TYPE 21 Tao,i TYPE 20 VPi PD optimizer TYPE 7 PDset Mixing TYPE 60 Tw,in &Mw HX modeling &mixing TYPE 41 Tw,out Tsup Load & status of AHUs TYPE 49 On/Off of AHUs Tw,sup Load & status of AHUs On/Off of AHUs Ma,i&Ta,in TYPE 35 Ma,i&Ta,in Pump & network Mw,i AHUs On/Off of AHUs Ma,i&Ta,in On/Off of AHUs TYPE 17 TYPE 63 Mw,i Pump & network AHUs Freq Tao,i Pump & network Mw,i AHUs TYPE 18 TYPE 63 Freq Tao,i TYPE 42 TYPE 12 TYPE 63 Tao,i VPi Freq TYPE 42 Pump sequence Npu PD optimizer TYPE 42 TYPE 39 TYPE 62 VPi Pump sequence PD PDset optimizer Pump sequence PD TYPE 39 TYPE 8 HX sequence Mixing optimizer TYPE 39 PDset TYPE 6 TYPE 39 TYPE 47 HX sequence Building VPi Npu Npu Load Nhx PDset Mixing Pump & network HX modeling Mw &mixing TYPE 39 Nhx TYPE Zones 47 3&4 TYPE 15 TYPE 36 Mixing Freq Mw,meas Tw,in HX modeling Zone 2 TYPE 48 Pump sequence &mixing TYPE 39 TYPE 37 Zone 2 Tw,sup Mw,set &Mw Mw & Tw,rtn Mw & Tw,rtn Pump & network Mixing & TYPE 16 bypass Tw,out TYPE 19 System Mw Npu Freq Mw,meas Mw,set Pump sequence Mixing TYPE 39 TYPE 61 Tw,rtn & Mw Mixing & bypass Mw & Tw,rtn Tw,sup & Mw TYPE 45 Zone 3&4 Tsup Supply pipe TYPE 31 Mixing & Bypass TYPE XX: Component type number TYPE 67 Simulated Mw,tot & Tw,rtn Tw,rtn & Mw,tot T: Temperature Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out Tw,ch,out M: Water or air flow rate Mw & PDmeas Mixing after cooling towers TYPE 5 Tw,sup On/Off of AHUs Chiller One Chiller Two Chiller Three Chiller Four Chiller Five Chiller Six Load: Cooling load TYPE 23 TYPE 23 TYPE 23 TYPE 23 TYPE 23 TYPE 23 Freq: Frequency Chiller sequence controller Nch On/Off On/Off On/Off On/Off TYPE 50 Cooling tower controller Mixing after chiller condensers (updated On/Off On/Off throughout N: Number Tw,cd,in VP: Valve position Nch Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out Tw,cd,out PD: Pressure differential Subscript TYPE 3&54&55 TYPE 4 Mw,tot&Tw,ct,in Tw,out,i On/Off,i&Freq,i Tw,cd,out w: Water a: Air CTA One CTA Two CTA Three CTA Four CTA Five CTA Six CTB One CTB Two CTB Three the CTB Fourentire CTB Five process) meas: Measurement i: Individual ao: Air outlet tot: Total in: Inlet pu: Pump rtn: Return set: Set-point TYPE 1 TYPE 1 TYPE 1 TYPE 1 TYPE 1 TYPE 1 TYPE 2 TYPE 2 TYPE 2 TYPE 2 TYPE 2 cd: Condenser ch: Chiller Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw Tw,out & Mw ct: Cooling tower out: Outlet Twb&Tdb Zone airflow rates Mw,tot&Tw,ct,out Load Nhx Mw Virtual On/Off of AHUs Tw,sup Mw & Tw,in Mw & PDmeas Mw Npu hx: wb: Nhx Tw,out Heat exchanger Wet-bulb Tw,rtn& Mw sup: db: Supply On/Off of AHUs Mw,&w,in Dry-bulb Tw,rtn& Mw Tw,sup

8 Design Commissioning The design commissioning mainly concerns the future operation and control performance of HVAC systems, and includes: 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) System Design Verification - Secondary water loop systems of 3rd and 4 th zones A FROM PODIUM & BASEMENT TO PODIUM & BASEMENT SCHWP to 12 HX-06 HX-06 (S-B) (S-B) SCHWP to 02 A B C D E F B Secondary water circuit for Zone 1 Secondary water circuit for Zone 2 Secondary water circuit for Zone 3 and Zone 4 Primary water circuit Chiller circuit Cooling water circuit FROM OFFICCE FLOORS(7-41) TO OFFICE FLOORS(7-41) (S-B) SCHWP to 05 C FROM OFFICE FLOORS (79-98) TO OFFICE FLOORSS (79-98) SCHWP to 03 PCHWP PCHWP PCHWP HX-78 HX-78 HX-78 SCHWP to 06 FROM OFFICE FLOORS (43-77) TO OFFICE FLOORS (43-77) PCHWP PCHWP PCHWP PCHWP PCHWP PCHWP PCHWP HX-42 HX-42 HX-42 HX-42 HX-42 HX-42 HX-42 SCHWP to 09 (S-B) (S-B) (S-B) (S-B) SCHWP to 03 SCHWP to 03 HX-78 HX-78 SCHWP to 06 HX-78 FROM OFFICE FLOORS (79-98) (S-B) (S-B) TO OFFICE FLOORSS (79-98) Flow meter Bypass valve FROM OFFICE FLOORS (43-77) TO OFFICE FLOORS (43-77) (S-B) SCHWP to 03 D PCHWP PCHWP PCHWP PCHWP PCHWP PCHWP HX-42 HX-42 HX-42 HX-42 HX-42 HX-42 HX-42 E EVAPORAROR EVAPORATOR EVAPORATOR EVAPORATOR EVAPORATOR EVAPORATOR WCC-06a-01 (2040 Ton) WCC-06a-02 (2040 Ton) WCC-06a-03 (2040 Ton) WCC-06a-04 (2040 Ton) WCC-06a-05 (2040 Ton) WCC-06a-06 (2040 Ton) F CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER CONDENSER CDWP CDWP CDWP CDWP CDWP CDWP From cooling towers Original System From Zone 3&4 SCHWP to 09 Primary pumps are omitted To cooling towers Revised System (operation mode) To Zone 3&4 (S-B)

9 Pump power (kw ) Comparison between Two systems Original design Alternative design Time (h ) Typical sunnysummer day Annual Pump Energy Saving is 1M kwh System Design Verification- Cooling tower system 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 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. 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 Silencer 100 Pa Fill packing 300 Pa 50 Pa Pressure drop From chiller To chiller

10 Example of CO 2 Sensor Installation Flow stations Empty CO 2 CO 2 CO 2 CO 2 CO 2 AHU BB CO 2 CO 2 CO 2 Morgan Stanley CO 2 CO 2 CO 2 CO 2 AHU CO 2 Empty CO 2 CO 2 CO 2 CO 2 CO 2 Empty CO 2 CO 2 Kaishing IC CO 2 sensor calibration and commissioning Measurement accuracy of CO 2 sensors directly affects indoor air quality and energy performance of air side system, which is therefore essential for implementing optimal ventilation control strategy. CO2 concentration (ppm) Before calibration Fresh air (Measured) Return air (Measured) 250 Supply air (Measured) Supply air (Calculated) 200 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) After calibration Fresh air (Measured) Supply air (Measured) Return air (Measured) Supply air (Calculated) 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)

11 Example of air flow station Installation P Q = A v = A 2 P Cooling 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 energy saving potential greatly at partial load conditions!

12 Cooling 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 The for cooling savings requirement is about 607,000 of the kwh, 2.86% of inside motor. annual energy consumption of chillers and cooling towers due to the lower frequency limit. The manufacture finally confirmed the minimum frequency is 20 Hz ensuring the normal operation of the fan. This low frequency increases the energy saving potential greatly at partial load conditions! Low Delta-T Central Plant Syndrome 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 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. Water flow rate (L/s) Temp. difference after decouple Water flow Chiller operating number Sample time (hour) Chiller number and Temp. difference

13 Low Delta-T Central Plant Syndrome 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. 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. When the low delta-t syndrome exists, a series of operation problems will be resulted The inability to sufficiently load chillers; Excess water flow demand; An increase in pump energy; applications. Either an increase in chiller energy or a failure to meet cooling load; etc. Temp. difference after decouple Water flow Some causes can be avoided, 200 but some of them cannot be avoided in some -100 Water flow rate (L/s) Chiller operating number Sample time (hour) Chiller number and Temp. difference 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.

14 System Improvement by using a Check Valve Primary pumps CHILLER 01 Secondary water circuit for Zone 1 Secondary water circuit for Zone 2 Secondary water circuit for Zone 3&4 CHILLER 02 AHU AHU AHU CHILLER 03 AHU AHU AHU Check valve CHILLER 04 CHILLER 05 AHU AHU AHU CHILLER 06 FM Secondary Pumps Secondary pumps Secondary pumps 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. Summary of experimental results 50 Closing the valve in the decouple Reopen the valve in the decouple Closing the valve in the decouple Reset supply water temp. set point from 5.5 C to 5 C Reopen the valve in the decouple Deficit flow (L/S) C set-point 5.0 C set-point Cooling load of chiller(kw) Outlet air temp. of AHU 1 in L15 ( C) :00:58 10:09:59 10:17:58 10:24:58 10:36:58 10:42:56 10:51:59 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 Time Test procedure 11:06:59 11:19:04 11:32:56 11:54:58 12:14:56 12:29:58 12:48:56 13:07:58 13:29:01 13:24:59 13:43:58 Time 13:37:59 13:56:59 13:50:59 14:13:58 14:08:59 14:38:58 14:34:00 14:52:04 14:44:56 15:02:58 15:16:57 14:58:58 15:33:04 15:10:56 15:47:59 15:29:01 16:06:59 15:39:00 16:23:01 15:57:59 16:15:58 Total power (kw) :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 Time Cooling energy of chillers Annual energy saving potential by using the check Closing the valve Reset supply water Reopen the valve in in the decouple temp. set point from the decouple C to 5 C valve in ICC is about 325, kWh when compared to that without using the check valve Using 'conceptual' check valve with similar weather condition by without using the check valve Supply air temperature 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 Time 13:50:59 14:08:59 14:34:00 14:44:56 14:58:58 15:10:56 15:29:01 15:39:00 13:31:59 13:48:03 13:56:01 14:09:57 14:28:03 14:39:56 15:57:59 16:15:58 14:48:00 14:57:59 Energy consumptions

15 Online performance testing of control optimizers and diagnostic tools on the simulated virtual system Control optimizers and diagnostic tools should be tested on the virtual systems prior to site implementation Virtual Plants Simulated Communication Interfaces IBmanager System Control Optimizer Simplified Models Optimization Strategies Performance Models Diagnosis Strategies Performance Prediction Diagnostic Tool Performance Prediction Saving Energy through Control Optimization

16 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 air-conditioning 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 subsystem 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

17 Optimal control strategies for central air-conditioning systems (cont 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 cooling water systems

18 Optimal control of condenser cooling water systems (cont d) Formulation of the optimal control strategy It is designed using a model-based method The overall structure of the optimal control strategy T wb, Q ev, N ch Define the search ranges for T w,cd,sup and N ct T w,cd,sup & N ct Online measurements and control signals Measurement filter T w,cd,sup N ch &T wb Simplified CTA and Performance prediction CTB tower models T w,cd,sup, N CTA, N CTB, M a,, P ct, Freq Cost estimation & optimization algorithm Supervisory control strategy Q ev, N ch, T w,ev,in Simplified chiller model T w,cd,out Optimal control settings & cost (T w,cd,sup, N CTA, N CTB, Freq, P ch +P ct ) Optimization process P ch It consists of : Performance predictor Cost estimator Optimization tool Supervisory strategy N CTA N CTB T w,cd,sup Freq Objective function Interface Chiller plant control system (BAS) N = ch NCTA N = + + CTB J minwtot min Wch, k WCTA, i W Tw, cd,sup Tw, cd,sup k= 1 i= 1 j= 1 CTB, i Optimal control of condenser cooling water systems (cont d) Parameters to be optimized The condenser water supply temperature set-point The number of CTA towers operating The number of CTB towers operating Optimization tool ---HQS (hybrid quick search) method T T n, o w, cd,sup n, o w, cd,sup = h 0 + h T 1 wb T T + h 2 w, cd,sup Q Qev ev T, des n. o w, cd,sup + T Control setting Upper limit Search range +Δx -Δx Operating constraints Low limit Search center (near optimal) Time basic energy and mass balances (i.e., flow, heat, etc.) mechanical limitations (i.e., fan speed, temperature, etc.)

19 Optimal control of condenser cooling water systems (cont d) Performance tests and evaluation Evaluation of control accuracy and computation performance Comparison between the HQS and GA-based strategies Items Seasons Spring Mild-summer Sunny-summer Typical working conditions Items Q load (kw) N ch T w,ev,in ( C) T w,ev,out ( C) T db ( C) T wb ( C) M w,cd (L/s) Tools HQS GA HQS GA HQS GA Optimization results W ch (kw) W ct (kw) W ch +W ct (kw) Optimal T w,cd,sup ( C) N CTA N CTB Freq (Hz) Computational The cost(s) computational cost saving is % Optimal control of condenser cooling water systems (cont d) Evaluation of the Energy Performance Comparison of condenser water supply temperature setpoints using HQS-based strategy and near optimal strategy Optimal temperature set-point 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 Spring case 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 Sunny-summer case Time (h ) Time (h ) Near-optimal temperature set-point

20 Optimal control of condenser cooling water systems (cont d) Comparison of the hourly-based power consumptions using different control methods HQS-based strategy Optimal strategy Near optimal strategy Spring case Optimal strategy Near optimal strategy Sunny-summer case Power difference ( kw ) Fixed approach Power difference ( kw ) Fixed approach Time (h ) Time (h ) Near optimal strategy Optimal control of condenser cooling water systems (cont d) Comparison of daily and annual power consumptions of the condenser cooling water system using different control methods Daily power consumptions Fixed approach Near optimal strategy HQS-based strategy Operation W Strategies ct +W ch W ct +W ch Saving Saving W ct +W ch Saving Saving (kwh) (kwh) (kwh) (%) (kwh) (kwh) (%) Spring 51,738 51, , Mild-summer 71,289 70, , Sunnysummer 91,653 90, ,356 1, Annual power consumptions Operation strategies W ch (kwh) W ct (kwh) W cd,pu (kwh) W tot (kwh) Saving (kwh) Saving (%) Fixed approach 18,464,812 1,882,583 4,210,690 24,558, Near optimal 18,715,458 1,501,701 4,210,690 24,427, , HQS-based 18,715,134 1,448,765 4,210,690 24,374, ,

21 Plume Control and Energy Benefits Normal operation when there is no predicted plume occurs Decision maker Platform for predicting plume occurring possibility 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 Operating Condition Power Consumption Operation modes Cooling Cooling Cooling Cooling Water Chiller Total Tower Tower Tower Difference Temp Setpoint Power Power Additional Number energy Freq consumption Power for plume C control - could Hz be reduced kw from kw kw kw % Reference % to 5.5% or 1.5% at low Load First-level warning Second-level warming Using heat pumps CT+1HP Chiller Plant Sequencing Control of Enhanced Robustness Using Data Fusion Technique

22 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 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 (2) Total cooling load based chiller sequencing control Building cooling load measurement Maximum cooling capacity Optimal number of chillers to be put into operation N c = φ(q cl, Q max ) Problems Building cooling load cannot be measured accurately Chiller maximum cooling capacity vary with the operating conditions

23 Fused Cooling Load Measurement Cooling load measurement Direct measurement of building cooling load Q dm = c pw ρ w M w (T w,rtn -T w,sup ) where c pw is the water specific thermal capacity; ρ w is the water density; M w is water flow rate; T w,rtn,t w,sup are chilled water return/supply temp. Indirect measurement of building cooling load Q im = f(p com,t cd,t ev ) where f is the chiller inverse model; P com is chiller power consumption; T cd,t ev 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 Advanced soft measurement system Data Fusion Engine Q f γ f Q dm + Q im,1 Q im,n Direct measurement Chiller Model 1 Chiller Model n T rtn M w Chiller Model 1 P com,1 T ev,1,t cd,1 P com,n,t ev,n,t cd,n Chiller Model n T sup Central Chilling Plant

24 Robust Chiller Sequencing Control Building Cooling Load Measurement Technique Central chilling plant Building Automation System Direct measurement Parameters setting Indirect Measurement Data Fusion Engine Alarming subsystem Chiller sequencing control Periodical analysis Robust Cooling Load Measurement Database Optimal Control of Variable Speed Pumps Speed control of pumps distributing water to heat exchangers Original implemented strategy --- differential pressure controller by resorting to the modulating valve Secondary side of HX From terminal units To terminal units Temperature set-point Temperature set-point Temperature controller T T Temperature controller HX HX M M Modulating valves Primary side of HX Pressure differential set-point ΔP Differential pressure controller From cooling source To cooling source To terminal units Secondary side of HX From terminal units Temperature set-point TM T Temperature controller HX HX Water flow set-point Primary side of HX TM Water flow controller From cooling source To cooling source Proposed strategy --- cascade controller without using any modulating valve

25 Performance test and evaluation 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. Pumps Number (standby) Energy consumption (kwh) Original Alternative strategy Strategy (kwh) (kwh) Energy saving of primary pumps before heat exchanges due to the use of PolyU strategy is about kwh. Saving (kwh) Primary pumps in Zone 1 1(1) 528, ,132 71,876 Primary pumps for Zones 3&4 3(1) 921, , ,405 Primary pumps in Zone 4 2(1) 401, ,420 54,588 Total saving of the primary pumps 251,869 Optimal Outdoor air Ventilation Control Static pressure set point Static pressure P The 7 th floor Static pressure controller. Outdoor air controller Set point Adaptive DCV strategy Model-based outdoor air flow rate Control strategy The 1 st floor

26 Energy-based outdoor air flow rate set-point resetting scheme W cost = W fan + Q COP outdoor = C k v M k out, set + M k out, set ( H k out COP H k rtn ) Outdoor Air Optimal Scheme Least Square Algorithm Set point trails Iterative algorithm Cost function estimator Model-based predictor Optimal set point Supervisor Range of set point Constrains Parameter estimators Parameter identification of the fan model Real process of the multi-zone air conditioning system Demand-controlled Ventilation control 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 Number of occupancy Counted Predicted 0 8:30 9:30 10:30 11:30 12:30 13:30 14:30 15:30 16:30 17:30 18:30 Time (hour) Comparison between counted and predicted occupancies

27 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. AHU1 AHU2 Study cases Control strategy Fixed flow PolyU Fixed flow PolyU About 662,000 Primary fan energy kwh consumption energy savings can be Site test case (kwh) (PolyU strategy achieved only applied to by Primary using fan energy saving PolyU (%) - ventilation control typical floor) (Nov., 2009) Energy saved due to fresh air cooling (kwh) strategy for all floors per year in Zone 2! Estimation case (PolyU strategy applied to all floors in Zone 2) Summer case (PolyU strategy applied to all floors in Zone 2) Primary fan energy consumption (kwh) Primary fan energy saving (%) Primary fan energy consumption (kwh) Fresh air cooling energy consumption (kwh) Total energy consumption (kwh) Total energy saving (%) Site Implementation of The Control Strategies

28 Implementation Strategy of Optimal Control and Diagnosis Tools in ICC Control Parameters Optimizer Diagnosis Overall KVA, etc. Chiller Plant Control Optimizer and Diagnosis IBmanager BACnet SDK Control Setting from PolyU Control Setting from ATC Decision Supervisor ATC Manual Control Building Management System LAN Supply air control optimizer Fresh air control optimizer Fresh air terminal VAV Box AHU PAU 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.

29 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 PoyU control strategies based on the original design; Summary of Energy Benefits 1,000,000 Saving by kwh Commissioning energy consumption (Improving is saved the due system to the modification on the secondary water loops of Zone 3 & 4; configuration and selection compared with the 2,360,000 kwh, (about 5.1% of annual energy original design. 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, Saving 500,000 by kwh Control (about Optimization 7%) of the total energy consumption of HVAC system) can be saved using PoyU case control when strategies the HVAC based system on the original operates design; correctly Saving by Control Optimization compared with the according to the original design intend.

30 Summary of Energy Benefits 1,000,000 Saving by kwh Commissioning energy consumption (Improving is saved the due system to the modification on the secondary water loops of Zone 3 & 4; configuration and selection compared with the 2,360,000 kwh, (about 5.1% of annual energy original design. 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. The annual total energy 607,000 kwh, (about 2.8% of annual energy consumption of chillers saving and cooling is towers) about of the 7.0M cooling kwh system will! be wasted when the lowest frequency is limited at 37 Hz. 3, Saving 500,000 by kwh Control (about Optimization 7%) of the total energy consumption of HVAC system) can be saved using PoyU case control when strategies the HVAC based system on the original operates design; correctly Saving by Control Optimization compared with the according to the original design intend. 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.

31