Energy Efficiency in Building Active Design Part II

Transcription

1 Energy Efficiency in Building Active Design Part II Presented by: CK Tang BSEEP Component 4 Manager Veritas Enviornment Sdn Bhd ck.tang@veritas.com.my Air Conditioning System System Sizing 1

2 Current Industry Practice Use rule of thumb to size Air-Conditioning? 200 ~ 220 Watt/m2, 80 ~ 90 Btu/ft2 Use manual spreadsheet? Compute solar gain, etc? Use a Computer Software Trane software Carrier E-20 Etc. CHW PUMP Chiller Load EVAPORATOR Heat Rejection Load O/A INTAKE DAMPER Cooling Coil Load COOLING COIL COMPRESSOR CONDENSER CCW PUMP COOLING TOWER RECYCLE AIR DAMPER FAN FILTER SPILL AIR DAMPER Space Load 2

3 LOAD Space Cooling Load Cooling Coil Load Chiller Load Heat Rejection Load HEAT 1. Internal Gain 2. External Gain 3. Fan Power 4. Fresh Air Intake 5. Duct Conduction Heat Gain 6. Chilled Water Pump Power 7. Pipe Conduction Heat Gain 8. Chiller Power 9. Condenser Water Pump Power Space Cooling Load Internal Heat Gain 3

4 People Heat Gain Degree of Activity Sensible Heat (W/person) Latent Heat (W/person) Seated at theater, night Seated, very light work Moderately active office work Standing, light work; walking (Department store; retail store) Bowling Taken from Ashrae 24 C Lighting Heat Gain Type/space Type of Usage Max. lighting power density W/m 2 Offices 15 Supermarkets/ Department Stores/ Shops 25 Actual Installed Lighting Power Density to be used! 9.8 W/m W/m W/m 2 Stores/ Warehouses/ Stairs/ Corridors/ Lavatories 10 MS 1525 (2007) 4

5 Equipment Heat Gain Load Density of Office Load Factor W/m² Light 5.4 Medium 10.8 Descriptions Assumes 15.5 m²/workstation (6.5 workstations per 100m²) with computer and monitor at each plus printer and fax. Computer monitor and fax diversity 0.67, printer diversity Assumes 11.6 m²/workstation (8.5 workstations per 100m²) ²) with computer and monitor at each plus printer and fax. Computer monitor and fax diversity 0.75, printer diversity Medium/Heav y 16.1 Assumes 9.3 m²/workstation (11 workstations per 100m²) with computer and monitor at each plus printer and fax. Computer monitor and fax diversity 0.75, printer diversity Heavy 21.5 Assumes 7.8 m²/workstation (13 workstations per 100m²) with computer and monitor at each plus printer and fax. Computer monitor and fax diversity 1, printer diversity Ashrae Fundamentals Space Cooling Load External Heat Gain 5

6 LOAD Space Cooling Load Cooling Coil Load Chiller Load Heat Rejection Load HEAT 1. Internal Gain 2. External Gain 3. Fan Power (blow through) 4. Fresh Air Intake 5. Duct Conduction Heat Gain 6. Chilled Water Pump Power 7. Pipe Conduction Heat Gain 8. Chiller Power 9. Condenser Water Pump Power Solar Gain Conduction Gain Computer Compute Design Weather Data Descriptions Ashrae design MS 1525 weather database v4.0 Recomme nded for KL Test Reference peak dry bulb temperature Test Reference peak enthalpy Dry Bulb Temperature ( C) Wet Bulb Temperature ( C)

7 Building Envelope Properties Used actual building properties! Ask for the Solar Heat Gain Coefficient of Glazing Ask for the U-value of wall and roof. Input the Thermal Capacity of material to model thermal mass Have faith in Science and in the 1 st Law of Thermodynamic. Infiltration heat gain A measured result of 10 government office buildings in 2010 by JKR indicates Average total fresh air in building is ~ 1 ach. Measured highest fresh air in building is ~ 2 ach. Based on occupant density of 10 m 2 /person and 4 m of height of office spaces. ~ 0.5 ach. This indicates that on average buildings have an additional infiltration of 0.5 ach. 7

8 Exfiltration ~ 0.5 ach Cooling Coil Load 8

9 LOAD Space Cooling Load Cooling Coil Load Chiller Load Heat Rejection Load HEAT 1. Internal Gain 2. External Gain 3. Fan Power 4. Fresh Air Intake 5. Duct Conduction Heat Gain 6. Chilled Water Pump Power 7. Pipe Conduction Heat Gain 8. Chiller Power 9. Condenser Water Pump Power 9

10 Fan Power Heat Gain W f = Q P t μ f Where W f = Fan Power (Watt) Q = Volume of Air Flow Rate (m 3 /s) P t = Total Fan Pressure, (Pa) μ f = Total Fan Efficiency (%) 10

11 Total Fan Pressure ΔP t = SP d + PD af + PD c + D p Where, ΔP t = Fan Total Pressure (Pa) SP d = Duct Total Static Pressure (Pa) PD af = Pressure Drop in Air Filter (Pa) PD c = Pressure Drop in Cooling Coil (Pa) D p = Dynamic Air Pressure = 1 2 ρv2 ρ = air density (1.2 kg/m 3 ) V = velocity of air at fan exit (m/s) Total Fan Efficiency FE t = F e x M e xb e Where, FE t = Fan Total Efficiency (%) F e = Fan Efficiency (%) M e = Motor Efficiency (%) B e = Fan Belt & Pulley Efficiency (%) Where, B e = 100%, if fan is direct driven bythe motor 11

12 CONDUCTION HEAT GAIN FROM DUCT Chiller Load 12

13 LOAD Space Cooling Load Cooling Coil Load Chiller Load Heat Rejection Load HEAT 1. Internal Gain 2. External Gain 3. Fan Power (blow through) 4. Fresh Air Intake 5. Duct Conduction Heat Gain 6. Chilled Water Pump Power 7. Pipe Conduction Heat Gain 8. Chiller Power 9. Condenser Water Pump Power Chilled Water Pump Power Where did the pump energy go to? ~90% of pump energy ends up in water 13

14 Pump Power Input parameters 1. Design ΔT (temperature differences) of design supply and return chilled water temperature. 2. Total Pump Efficiency 3. Total Pump Head H = Pump Head A factor of the followings Flow Rate (~ fixed by building cooling load & Design ΔT) Pipe Size (~ designed by consultants) Number and types of bends (~ proposed by contractor) Valves and Fittings (~ proposed by contractor/supplier) Chiller Heat Exchanger (~ chiller selection) 14

15 Chilled Water Pipe Heat Gain To be of concern if chilled water pipe is running outdoor. Heat Rejection Load 15

16 LOAD Space Cooling Load Cooling Coil Load Chiller Load Heat Rejection Load HEAT 1. Internal Gain 2. External Gain 3. Fan Power (blow through) 4. Fresh Air Intake 5. Duct Conduction Heat Gain 6. Chilled Water Pump Power 7. Pipe Conduction Heat Gain 8. Chiller Power 9. Condenser Water Pump Power Chiller Power consumption Open Drive or Hermetic Drive. Open drive has an electric motor that is air cooled by the ambient air. A hermetic drive has an electric motor that is hermetically sealed and cooled with refrigerant. 16

17 Chiller Efficiency COP = Cooling Provided (kw cooling ) Electricity Consumed by Chiller (kw e ) kw per ton = 12 COP X Condenser Pump Power Also take note of direct sunlight heating up the condenser pipe! 17

18 Pump Power Input parameters 1. Design ΔT (temperature differences) of design supply and return chilled water temperature. 2. Total Pump Efficiency 3. Total Pump Head Energy Efficiency 1 st Estimates Simulation Studies Based on an Office Building Scenario 17 Floors 18

19 AIR SIDE Optimization Energy Efficiency Estimates Air Side Optimization 6 Items to Optimize 1. AHU Flow Rate (CAV vs. VAV) 2. AHU Total Fan Efficiency 3. AHU Total Pressure Loss 4. Optimal Design Off-coil Temperature 5. Active control of Fresh Air Intake 6. Heat Recovery Wheel and Infiltration Rate 19

20 CAV Design ΔT Optimization Reduced flow rate CAV Part Load Fine Tuning it based on Actual Condition can reduce significant amount of energy! 20

21 VAV Design ΔT Optimization CAV Vs. Full Load Descriptions BEI Units CAV (at 11 C off-coil) kwh/m².year VAV (at 11 C off-coil) kwh/m².year BEI VAV improvement 7.1 kwh/m².year % VAV improvement 4.3% Percentage 21

22 CAV Vs. Part Load 45% Reduction in Occupancy BEI Units VAV at design flow rate kwh/m².year CAV at reduced flow rate kwh/m².year BEI CAV improvement 4.0 kwh/m².year % CAV improvement 3.1% Percentage Fan Pressure & Efficiency 22

23 Fan Pressure & BEI Options for Reduction of Fan Total Pressure Larger Ducts, Less Bends Selection of Fittings 23

24 Air Filter Pressure drop Camfil Closed Pleat Pressure Drop Curve Cooling Coil Pressure Drop Reference/Application-Notes/Selecting-a-Heat- Exchanger 24

25 Face Velocity Reduction 2.5 m/s down to 2.0 m/s (or lower) Fan Efficiency & BEI 25

26 Demand Controlled Fresh Air CO2 Sensor 26

27 BEI & Actual Building Occupancy CO2 Level Set Point 27

28 Heat Recovery toilets toilets 28

29 Heat Recovery Using toilet exhaust for fresh air intake 29

30 WATER SIDE Water-Side Optimization 4 Items to Optimize 1. Chilled Water Distribution Energy Efficiency 2. Chiller Energy Efficiency 3. Condenser Water Distribution Energy Efficiency 4. Cooling Tower Energy Efficiency 30

31 BEI (kwh/m 2.year) 15/10/2014 Chilled Water Distribution Options Studied 1. System Selection Primary Constant Flow Primary Constant/Secondary Variable Flow Primary Variable Flow 2. High ΔT Chilled Water Distribution 3. Low Pump Head 4. High Pump Efficiency Chilled Water Distribution Specific Pump Power of 545 W per l/s Base Primary Constant Primary Variable Primary Secondary Primary Secondary (pump power add 10%) Primary Secondary (pump power add 20%) Primary Secondary (pump power add 30%) 31

32 High ΔT Chilled Water distribution H = 1.16 Q T Where, H = heat load (kw) (building cooling load) Q = water volume flow rate (m3/h) ΔT = temperature difference ( o C) Rewriting, Q = H 1.16 T Issues to consider for high ΔT Design option Pipe Sizes: Reduction in sizes, reduces capital cost, while maintaining the same pump head. Or, Maintain pipe sizes, while reducing pump head, increasing efficiency. Chilled Water Supply Temperature: Reduced temperature, reduces chiller efficiency, i.e C to 5.56 C (44 F to 42 F) Chilled Water Return Temperature: Increased ΔT, increases cooling coil sizes in AHU, increasing capital cost. 32

33 BEI (kwh/m2/year) BEI (kwh/m2.year) 15/10/2014 Pump Head Constant (~Pipe Size Reduced) Base Base DT 12F (44/56F) DT 14F (44/58F) DT 16F (44/60F) DT 18F (44/62F) DT 16F (42/58F) Chilled Water Temperature Different Primary Constant Primary Variable Primary Variable System Base Base DT 12F (44/56F) DT 14F (44/58F) DT 16F (44/60F) Chilled Water Temperature Different DT 18F (44/62F) DT 16F (42/58F) Pump Head Constant Pipe Sized Down, Maintaining Pressure Pump Head Reduced Pipe Size Maintained, Reducing Pressure 33

34 Pump head and efficiency Pump power Equation P h = q ρ g h 3. 6x10 6 x μ P h = Pump Power (kw) q = Flow Capacity (m 3 /h) ρ = fluid density (Water = 1,000 kg/m 3 ) g = gravity (9.81 m 2 /s) h = Pump Total Pressure (m of water) μ = Pump Total Efficiency (%) 34

35 Rewriting it into Specific pump power Specific Pump Power P = ρ g h = 9.81 h μ x 1000 μ P = Specific Pump Power (W per l/s) ρ = fluid density (Water = 1,000 kg/m 3 ) g = gravity (9.81 m 2 /s) h = Pump Total Pressure (m of water) μ = Pump Total Efficiency (%) 35

36 BEI (kwh/m2.yer) 15/10/2014 Chilled Water Pump ΔT 6.67 C (44/56 F) Primary Variable System y = x R² = Specific Pump Power (W per l/s) Reducing Specific Pump Power by 100 W per l/s, reduces BEI by 100 x = 0.6 kwh/m2.year Pump Head Optimization A factor of the followings Flow Rate (~ fixed by building cooling load & Design ΔT) Pipe Size (~ designed by consultants) Number and types of bends (~ proposed by contractor) Valves and Fittings (~ proposed by contractor/supplier) Chiller Heat Exchanger (~ chiller selection) 36

37 Priorities 1. Specific Pump Power Reduction Pump Head Pump Efficiency 2. Primary Variable Flow or Primary/Secondary Flow 3. High ΔT & Maintain pipe size. Chiller Efficiency 37

38 Chiller Efficiency COP = Cooling Provided (kw cooling ) Electricity Consumed by Chiller (kw e ) kw per ton = 12 COP X

39 Caution on chiller study DOE-2 Chillers Performance Curve-Fit Centrifugal Chiller based on chillers manufactured around Newer centrifugal chiller can be significantly more efficient at part load. Screw Chiller curve-fit was updated recently. ~ 2006 updated VSD Chiller curve-fit is the latest introduction. ~ 2006 introduced. Based on a frictionless centrifugal chiller. Condenser Pump Efficiency 39

40 High ΔT Condenser Flow Rate Typical Design: 95/85 F (35/29.44 C) Flow Rate: 2.4 gpm/ton Higher Condenser Flow Rate Chiller efficiency is better But, Pump power increases Condition Tested: 93/85 F (33.9/29.4 C) 3.0 gpm/ton 95/85 F (35/29.4 C) 2.4 gpm/ton 97/85 F (36.1/29.44 C) gpm/ton, a reduction of 100 W per l/s, reduces BEI by: 100 x = 2.3 kwh/m2.year 40

41 Cooling Tower Fan Efficiency Reduction of 0.01 kwe/hrt = 0.01 x = ~ 1.5 kwh/m2.year reduction Variable Speed Fan Cooling Different Set Point Water Leaving Temperature. 41

42 Cooling Tower summary Bridging Design and Actual Operation Performance 42

43 Common Installation Issues Install It Right! Air Leakages Main Doors Missing Partition above false ceiling Porous walls Duct leakages Missing dampers in smoke ventilation ducts No seals between windows frame and wall 43

44 Piping and Ducting Layout What is wrong with this picture? oolingsystemupgrades.html Straight length of pipe before pump suction inlet Note the Flat Top Eccentric Reducer used to avoid air pocket at suction inlet. 44

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46 Appoint Building Energy Manager Need to appoint someone to take charge. Commissioning vs. TAB TAB = Testing, Adjusting and Balancing Commissioning = Professional Service for Energy Efficiency in Building Owner s Project Requirement Design Intent Commissioning Plan Basis of Design Commissioning Specifications Contract Review Submittal Review TAB before handing over Handing Over Periodic Testing Plan Training of Facility Manager 46

47 Fine-Tuning Match building to actual occupants requirements while optimizing efficiency. Lighting schedule Air-Conditioning schedule Sensors Calibration Temperature Set-Point Air Rebalancing Computer & Equipment Settings Occupant s Awareness Campaign Continuous Monitoring 1. Sub-meters 2. Energy Management System 47

48 Energy Management System Line Charts Bar Charts Daily Weekly Monthly Yearly The End 48