1. www.alephnet.co.jp Aleph Networks Co. Inefficient Operation Recognized by Commissioning and Case Example of Countermeasures Ritsumeikan Uji HighSchool Purpose of Study Vol.4 1

2. www.alephnet.co.jp Aleph Networks Co. Target Heat Source System Outline Gas-fired absorption chiller/heater 450RT (14-7 ℃， 7 ℃ difference)×2 units 【 Target building information 】 Building ： Ritsumeikan Junior High/High School Location: Uji City in Kyoto Pref. Total floor area ： 19,172m2 （ 4 stories above ground ） Completion: August 2002 （ 8 years old) 【 Outline of heat source system for commissioning 】 ＊ The photos were obtained from the website of Ritsumeikan Uji High School. 1 inverter in 4 units Primary pump （ 3240ℓ/min ・ 15m ・ 15kW ） Cooling water pump （ 7500ℓ/min/20m ・ 37kW ） 【 Control details 】 ⇒ General control Control by the number of heat source units ･･･ Increased/decreased by thermal load （ one unit operates constantly ） Control by the number of secondary pump units ・・・ Increased/decreased by load flow Inverter control of secondary pump ・・・ PID control by pressure （ 1620ℓ/min ・ 30m ・ 15kW ） HVAC Secondary pump group 2

3. www.alephnet.co.jp Aleph Networks Co. Cx. Before Taking Measures on Heat Source System (1) Analysis of Load and Heat Source Operation Commissioning Before Taking Measures 【 No. of heat source units in operation 】 【 Analysis of operation load factor of heat source 】 ＊ Operation load factor = generated heat / rated performance ・ 60% at maximum ・ Load with less than 20% occurs most frequently ・ High proportion of extreme-low load operation ⇒ 2-unit operation occurred “0” time. 【 Analysis of chilled/hot water temp. difference at inlet and outlet of heat source 】 Rated temp. difference is 7 ℃. Difference is small due to low load. Rated temp. difference is 5.5 ℃ Difference is small due to low load. 【 Analysis of cooling water temp. difference at inlet/outlet of heat source 】 Rate of occurrence No. of heat source unit in operation 1 unit2 units Cooling season Heating season Chilled/hot water temp. difference at inlet/outlet ( ℃ ) 1 unit Cooling water temp. difference at inlet/outlet ( ℃ ) Cooling season Heating season Cooling season Heating season 3

4. www.alephnet.co.jp Aleph Networks Co. Cx. Before Taking Measures on Heat Source System (2) Analysis of Water Transport system （ Cooling Season ） Commissioning Before Taking Measures 【 Load flow analysis 】 【 Output analysis of secondary pump inverter 】 0%→0Hz ， 100%→60Hz ・ Output ranges between 30 and 100% ・ Output less than 30% did not occur. → Water pressure secured. ・ One secondary pump unit can manage operation. ・ Flow rate with low load is predominant. Rate of occurrence Load flow Low flow rate of secondary pump unit: less than 1620 L/min. Low flow rate of primary pump unit: less than 3240 L/min. Secondary pump inverter output [%] 4

5. www.alephnet.co.jp Aleph Networks Co. Cx. Before Taking Measures on Heat Source System (3) Analysis Results and Proposed Measures 【 Summary of analysis 】 1)Two-unit operation of heat source does not occur. 2)Hourly peak load takes only 60% of capacity of one unit. 3)Low load operation period with less than 20% of single unit is long.  Although method to control by the no. of heat source/secondary pump units was introduced as a measure for partial-load operation, real situation was constant operation with one unit of each all through the year. ⇒ No point controlling by the number of units  System was designed to cope with 7 degrees difference of cooling water temperature, but it is ineffective. Partial-load control at base unit operation is required. Commissioning Before Taking Measures 5

6. www.alephnet.co.jp Aleph Networks Co. Control Method Introduced as Energy Saving Measures and Summary of Outcome （ Cooling Season ） Energy Saving Control 【 Diagram of new heat system instrumentation 】 ① Low-load operation avoidance control (0-unit operation control ） Elec. Consumption at primary pump － 6,000 kWh(31 ％ reduced) ② Control by utilizing surplus pressure in primary pump Elec. Consumption at secondary pump -10,000 kWh （ 93 ％ reduced ） ③ Cooling water pump inverter control -37,000 kWh(75 ％ reduced ） As a result of taking measures 1-3, receiving power demand was reduced as follows: 488kW→452kW →- 36kW reduced( reduction of 7%) Air conditioner Added meter Pressure sensor Temp. sensor Flow meter Control valve Ammeter Closed expansion tank 6

7. www.alephnet.co.jp Aleph Networks Co. 0-unit Operation Control (1) Problems in conventional control 【 Low load operation 】 【 Problems: inefficient operation due to low load 】 1) Low load operation is inefficient. ・ Load less than 20% of capacity ： Combustion control operates on- off. ・ Best efficiency is achieved when the output is 40-70% of capacity. 2) To protect equipment, it cannot be stopped while heat source unit is running. 【 0-unit operation control 】 ● At low load, it stops and only circulates water. ● With increased load, it restarts. ⇒ ・ Power reduction on auxiliary machinery ・ Long operation at good efficiency point. 【 0-unit operation control 】 Only auxiliary machinery cannot be stopped even at low load operation. Development of Partial-Load Control R-1 Gas absorption chiller R-1 Gas absorption chiller R-2 Gas absorption chiller R-1 Gas absorption chiller R-2 Gas absorption chiller HVAC n HVAC1 Heat Source main unit Chilled/hot water pump Cooling tower Cooling water pump Linked Cooling water inlet temp. Gas consumption rate (m3 (normal condition) /RT Refrigeration capacity (%) Fig.5.3 Gas absorption chiller characteristic chart (outlet temp. 7 degrees c constant) 7

8. www.alephnet.co.jp Aleph Networks Co. Control Method Introduced as Energy Saving Measures(1) - Low-Load Avoidance Control of Heat Source - Energy Saving Control 【 Low –load avoidance control of heat source 】 → At low load, the no. of heat source units in operation becomes “0” by stopping heat source as well as auxiliary machinery. 【 Constant operation with low load (conventional) 】 【 Changeover to 0-unit operation at low load 】 Expected effect 1 ） Reduced power consumption by stoppage of auxiliary machinery 2 ） Avoidance of inefficient low load operation →Improved load factor of heat source equipment 【 Decision point to start 0-unit operation 】 ・ Heat source load factor: 20% ・ Feedwater temp.: below 9 deg C. 【 One unit starts operation 】 ・ Feedwater temp. : 11 deg C and higher HVAC 1 HVAC n R-1 Gas absorption chiller R-2 Gas absorption chiller R-2 Gas absorption chiller R-1 Gas absorption chiller Fully-closed (0%) 8

9. www.alephnet.co.jp Aleph Networks Co. Control Method Introduced as Energy Saving Measures (2) -Control By Utilizing Surplus Pressure in the Primary Pump ① - Energy Saving Control 【 In case of small demand at load side: usually 】 【 Primary pump pressure is used for circulation of secondary 】 【 Outline of control by surplus pressure in the primary pump 】 1)Control valve is installed on the communicating tube. 2)Primary pump pressure can be used for circulation at the secondary side by closing this control valve properly. 3)Secondary pump inverter compensates only deficient pressure at primary pump. (end pressure control) 4)The flow rate through heat source unit should be set to more than 50% to avoid occurring stoppage by error. More than 50% of rated flow rate Inverter control by end pressure Valve closing direction Flow rate decreases Secondary pump stops Only primary pump circulates Close control valve Primary pump head is lost at communicating tube 9

10. www.alephnet.co.jp Aleph Networks Co. Verification of Effect 【 Monthly percentage of 0-unit operation （ 0-unit operation in July is “invalid” ）】 The lower the load factor becomes, the higher the percentage of 0-unit operation becomes. Effect Verification of Introduced Energy Saving Control (1) - Low-Load Operation Avoidance Control - MayJuneAugustSeptember Load factor [%] Percentage of 0-unit operation Percentage of 1-unit operation Load factor 10

11. www.alephnet.co.jp Aleph Networks Co. Verification of Effect 【 Comparison of power consumption on chiller/heater primary pump 】 With introduction of low-load operation avoidance control, heat source operation hours were reduced. Power consumption on chiller/heater primary pump was also reduced accordingly. Effect Verification of Introduced Energy Saving Control (2) 2008 (Before introduction) 2010 (After introduction) 31% reduced Power consumption [kWh] Primary pump power consumption MaySeptemberAugustJulyJune Time [h] Generated heatHeat source group command ON Total operation hours of R-1 & 2 23% reduced 11

12. www.alephnet.co.jp Aleph Networks Co. Effect Verification of Introduced Energy Saving Control (3) Verification of Effect 【 Comparison of secondary pump inverter output 】 By utilizing surplus pressure at primary pump, the inverter output at secondary pump reduced drastically. 【 Comparison of power consumption on chiller/heater secondary pump 】 2008 (Before introduction) 2010 (After introduction) 2010 (After)2008 (Before) Power consumption [kWh] Secondary pump power consumption MayJuneJulyAugustSeptember MayJuneJulyAugustSeptember Average output of secondary pump inv. [%] 93% reduced Lowered INV. output ※ Average INV. output in secondary pump operation: 100%=60Hz 0%=Hz 12

13. www.alephnet.co.jp Aleph Networks Co. Effect Verification of Introduced Energy Saving Control (4) Verification of Effect Inverter installed in cooling water pump (cooling water variable flow control) → Inverter PID control by temp. difference (4 deg C) of cooling water at inlet/outlet of heat source machine. Power on cooling water transport decreased, reducing electricity consumption drastically. 【 Comparison of power consumption on cooling water pump 】 2008 (Before introduction) 2010 (After introduction) Power consumption [kWh] MayJuneJulyAugustSeptember Cooling water pump power consumption 75% reduced 13

14. www.alephnet.co.jp Aleph Networks Co. Verification of Effect Maximum demands were compared between before and after introduction. Entire heat source system: 46kW reduced. Power receiving point: 36kW reduced. Power charges were reduced by reviewing the contract with Power Company. Effect Verification of Introduced Energy Saving Control (5) 【 Comparison of receiving power demand 】 【 Comparison of power demand of heat source system 】 Jul.17, 2009 (before introduction: the day max. demand occurred)Jul.10, 2010 (after introduction: the day max. demand occurred) Chiller/heater prim. pump Chiller/heater second. pump Heat source body Cooling towerCooling water pumpCooling towerCooling water pump 46kW reduced Receiving power demand [kW] 36kW lowered 2009 (before introduction) Max. demand occurred on Jul.17 2010 (after introduction) Max. demand occurred on Jul.10 Power consumption[kWh] 14

15. www.alephnet.co.jp Aleph Networks Co. Energy Saving Control Control Method Introduced as Energy Saving Measures and Summary of Outcome （ Cooling Season ） 【 Diagram of new heat system instrumentation 】 ① Low-load operation avoidance control (0-unit operation control ） Elec. Consumption at primary pump － 6,000 kWh(31 ％ reduced) ② Control to utilize surplus pressure in primary pump Elec. Consumption at secondary pump -10,000 kWh （ 93 ％ reduced ） ③ Cooling water pump inverter control -37,000 kWh(75 ％ reduced ） As a result of taking measures 1-3, receiving power demand was reduced as follows: 488kW→452kW →- 36kW reduced( reduction of 7%) Air conditioner Added meter Pressure sensor Temp. sensor Flow meter Control valve Ammeter Closed expansion tank Reprint 15

16. www.alephnet.co.jp Aleph Networks Co. Summary (Significance of Taking Measures Based on Data Analysis) This case example showed that commissioning based on data analysis made issues in the performance clear in quantitative form. →This enabled us to propose realistic measures to be taken, envisaging exact effects. As shown in this case, it is pointed out that many heat source systems in business buildings are mostly running with inefficient partial-load operation. →Commonly-used control method by the number of heat source and pump units cannot make big effect as measures for partial-load operation. Control method to improve efficiency of partial-load operation implemented in this project has proved to be a very effective method at low cost. →This technique is quite useful as “a bridging technique” until the next large-scale refurbishment including renewal of heat source or other equipment. Summary 16

17. www.alephnet.co.jp Aleph Networks Co. 2 Renewal of The Heat Source Machines 17

18. www.alephnet.co.jp Aleph Networks Co. Consideration at Renewal of Heat Source System Purpose of Study  Optimal renewal approach needs to be examined based on the real picture of annual load condition, refurbishment cost, running cost after refurbishment including energy consumption, maintenance of equipment and CO2 emission cost. 1) Review the current capacity → Can be downsized to suit the real situation 2) Application of highly-efficient heat source system 3) Combination of heat source equipments ・ Electric type ＋ gas type （ level the power demand ） ・ Combination of capacity → combination of heat source equipments small capacity (for low load) + large capacity ・ Combination with thermal storage → Introduction of ice thermal energy storage system (level the power demand) ・ Application of free cooling → Natural energy  Enhancement of control system counts in the operation of complex heat source system. 18

19. www.alephnet.co.jp Aleph Networks Co. Highly-Efficient Heat Source System Highly-efficient heat source system 1)Heat pump technology (electric heat source) 2)High efficiency in partial load a. Modularization b. Inverter Purpose of Study Compressor When refrigerant gets compressed, temp. rises. Expansion valve When pressure decreased rapidly, temp. lowers Indoor side outdoor side Refrigerant (gas) Refrigerant (liquid) Heat taken from room Energy input to compressor Enthalpy (KJ/kg) Pressure Liquid Liquid + Gas Compression Gas Expansion Evaporation Condensation CondenserEvaporator Electric power 19

20. www.alephnet.co.jp Aleph Networks Co. Consideration at Renewal of Heat Source System Leveling of power consumption 1)Combination of electric type and gas type (absorption) heat source equipment 2)Application of night time thermal storage Other ・ Free cooling Purpose of Study Chiller Load Chiller Brine piping Ice thermal storage tank Heat source equip. A/C 20

21. www.alephnet.co.jp Aleph Networks Co. Purpose of Study Centrifugal water chilling unit Partial load characteristic curve of fixed speed Partial load characteristic curve of variable speed High Efficiency heat source machine Cooling water ( ℃ ) Load (%) Figures on the lines are cooling water temperature COP improves in the entire operation. COP of partial load improves. COP improves due to expansion of lower limit temperature of cooling : Old machine : New machine water Load (%) 21

22. www.alephnet.co.jp Aleph Networks Co. Purpose of Study High Efficiency heat source machine Modular chillers Partial load characteristic curve Load % Unit COP Most used range Partial load characteristic curve at sequential unload start Atmospheric temperature accords to IPLV calculation of ARI 550/590 22

23. www.alephnet.co.jp Aleph Networks Co. Purpose of Study In the Case of Air-Conditioning System What has happened to air-conditioning system? 5-2. Partial-load efficiency There is a big difference between air conditioner today and that of 15 years ago in terms of partial-load efficiency. ■ 15 years ago:Designed so as to have maximum COP at the rated value. ■ Today: Designed so as to have maximum COP with the load around 50%. Fig.4 Examples of partial load factor/ temperature characteristics of air conditioner Partial-load factor [-]Temperature [deg C] Correction of COP by partial-load factor [%] Correction of COP by temperature [%] Heating Cooling Defrosting mode 23