Commercial Water Heater Performance: Laboratory Testing and Modeling

Transcription

1 Commercial Water Heater Performance: Laboratory Testing and Modeling Edwin Huestis, P.E. Mechanical Engineer PG&E Applied Technology Services ACEEE Hot Water Forum November 4, 2013

2 Presentation Objectives Identify the objectives/tasks of PIER effort Describe experimental methods - PG&E s Applied Technology Services Discuss experimental results Key take aways Identify opportunities for future research 2

3 PIER Effort Objectives Stimulate the purchase of high-efficiency [condensing] water heaters for both retrofit and new construction. Secure energy savings through a water heater RCx initiative including operational flue-damper, insulation, and optimizing distribution. Understand the impact that preheating inlet water will have on the performance of high-efficiency water heaters. Expand on best practice guidelines for designing and operating water heating systems in commercial food service. 3

4 Testing in Support of PIER Objectives Characterize 24-hour hot water system draw pattern at a commercial facility with a field monitoring effort Re-create a replica commercial hot water system in a laboratory environment, and subject the system to the same draw pattern Measure impacts of WH selection, recirculation, insulation, timeclock, aquastat, POU heating and flue damper position on system performance Measure impacts of pre-heating on water heater thermal efficiency Standby Losses 4

5 Field Characterization of Restaurant Hot Water Use (Completed by Fisher Nickel - FSTC) Fisher-Nickel conducted field monitoring at a quick service restaurant to gather a high resolution 24-hour real world hot water use profile

6 Measuring Commercial Water Heater System Performance: System Delivery Efficiency vs. WH Thermal Efficiency ~ Output Energy/Input Energy 6

7 PG&E Applied Technology Services Commercial Water Heater Laboratory Configuration RECIRCULATION LOOP WATER HEATER UNDER TEST END USES W/ AUTOMATED VALVES 7

8 PG&E Applied Technology Services Commercial Water Heater Laboratory Configuration (cont d) RECIRCULATION LOOP WATER HEATER UNDER TEST END USES W/ AUTOMATED VALVES 8

9 Measuring Commercial Water Heater System Performance: Instrument Uncertainty and Calibration 9

10 Energy Performance Impact: Water Heater Selection & Thermal Efficiency per ANSI Standard ANSI Standard Test Conditions: 70F inlet, 140F outlet 10

11 Energy Performance Impact: Preheating and Condensing Tankless Water Heaters Consider impacts of any pre-heating on water heater thermal efficiency Tests ran at steady state 11

12 Energy Performance Impact: Preheating and Condensing Tank-type Water Heaters Consider impacts of any pre-heating on water heater thermal efficiency Tests ran at steady state 12

13 Energy Performance Impact: Preheating and Mean Tank Temperature Condensing WH 13

14 Energy Performance Impact: Stratification in Standard Efficiency Tank-Type Water Heater Standby Loss & T.E. Standby Loss % (Btu/h) 14

15 Energy Performance Impact: Stratification in High Efficiency Tank-Type Water Heater Standby Loss & T.E. Standby Loss % Btu/h 15

16 Energy Performance Impact Summary: Standard Efficiency Tank-Type Water Heater - RCx and Retrofit Measures 16

17 Energy Performance Impact: Insulation of Distribution System Delivery Temperature RCx Measure: System Insulation Test Condition With Insulation With Partial Insulation With No Insulation System Delivery Efficiency Hand 3 Comp Mop Lavatory % Change in S.D.E. vs. w/ Recirc w/ Insulation 53.85% X 48.65% % 45.86% % 17

18 Energy Performance Impact: Insulation of Distribution System Variable Delivery Volume 18

19 Energy Performance Impact: Flue Damper Function Delivery Temperature RCx Measure: Disable Flue Damper Test Condition Base Case w/ Recirc Disable Damper (w/ins) Disable Damper (w/o ins) System Delivery Efficiency Hand 3 Comp Mop Lavatory % Change in S.D.E. vs. w/ Recirc w/ Insulation 53.85% X 48.79% % 42.10% % 19

20 Energy Performance Impact: Timeclock Delivery Temperature RCx Measure: Timeclock Test Condition Base Case w/ Recirc Timeclock (w/ins) System Delivery Efficiency Hand 3 Comp Mop Lavatory % Change in S.D.E. vs. w/ Recirc w/ Insulation 53.85% X 56.58% % 20

21 Energy Performance Impact: Aquastat Delivery Temperature & Performance RCx Measure: Aquastat w/ Insulated System Test Condition Base Case w/ Recirc Aquastat (w/ins) System Delivery Efficiency Hand 3 Comp Mop Lavatory % Change in S.D.E. vs. w/ Recirc w/ Insulation 53.85% X 58.25% % RCx Measure: Aquastat - w/o System Insulation Test Condition Base Case w/ Recirc Aquastat System Delivery Efficiency Hand 3 Comp Mop Lavatory % Change in S.D.E. vs. w/ Recirc w/ Insulation 45.86% X 49.49% % 21

22 Energy Performance Impact: Water Heater Selection and Distribution System Recirculation 22

23 Key Take Aways Water Heater Thermal Efficiency Under the conditions outlined the ANSI Standard, the tank-type condensing water heater offered the highest thermal efficiency. Stratification within the tank provides a low temperature medium to recover latent energy contained in the exhaust gas. Under the conditions outlined the ANSI Standard, the standard efficiency tankless water heater was more efficient than the standard efficiency tank-type water heater. Under the conditions outlined the ANSI Standard, the thermal efficiency of the condensing tankless unit exceeded the thermal efficiency of both standard efficiency tank-type heaters, but was less efficient than the tank-type condensing water heater. 23

24 Key Take Aways Water Heater Standby Loss Standby loss of a high efficiency tank type water heater is half that of a standard efficiency tank-type water heater. Due to the stratification in a high efficiency tank-type water heater, the average tank temperature is reduced compared to a standard efficiency tank-type water heater. Tankless water heaters consume very little electric energy and no gas in standby. 24

25 Key Take Aways Hot Water System Delivery Efficiency Depending on the application, condensing tank-type water heaters operating in insulated systems with no recirculation offered great system delivery efficiency. Eliminating recirculation through the condensing tank-type water heater allowed for stratification within the tank, enabling sufficient temperature difference for latent heat capture from exhaust gases. Operating a high efficiency water heater, tank-type or tankless, with recirculation will reduce the system delivery efficiency (the amount depending on the temperature of recirculation, see task 4.4). 25

26 Key Take Aways Energy Savings through Retrocommissioning and Retrofit Insulation of the water heater distribution system generally improved its overall performance Less input energy was required to meet fixture demand Delivery temperature increased under most circumstances For applicable water heaters, bringing a flue damper back into service reduces input energy, but make no difference in delivery temperature. For applications where recirculation is not needed during specific times of the day, a timeclock can reduce input energy requirement by reducing system heat loss. Installation of an aquastat for controlling a system recirculation pump appears to result in an improvement of system delivery efficiency, but the actual improvement varied from test to test. If the aquastat does nothing that impacts the control of hot water temperature within the water heater it will at least reduce distribution system losses The performance of this device and subsequently the performance of the hot water system is dependent upon how the device is setup. Point of use heaters are not well suited for systems like the one under test in this effort, as removing the end use did nothing to reduce distribution system losses. If an extended length of pipe exists between the point of use, and distribution system heat loss can be reduced, point of use heaters may be a great option for saving energy. Site to source energy usage should be considered, along with the cost of electrical energy vs. gas energy. 26

27 Key Take Aways Impact of Preheating on Thermal Efficiency Thermal efficiency degrades with the increase in entering water temperature, especially above 90 o F, for both high efficiency tanktype and tankless water heaters. System designers should take into account this impact of entering water temperature on system performance. Tankless water heaters may limit output with increasing entering water temperature, while tank type heaters will not modulate in this way unless designed to do so. 27

28 Best Practice Recommendations Condensing tank-type water heaters operating in systems with no recirculation offered the best system delivery efficiency. When a recirculation pump was in use, the system delivery efficiency maintained constant for all types of tankless tank-type heaters, with the exception of the standard efficiency tank-type heater, which performed worse than the rest. Adding insulation to the distribution system increased the system delivery efficiency and delivery temperature at the fixtures. For systems where preheating of incoming water is being performed, heater efficiency was found to decrease rapidly with entering water temperatures exceeding 90 o F. 28

29 Opportunities for Future Research Human Factors 29

30 Opportunities for Future Research Distribution System Scenarios PG&E CHWH 30

31 Opportunities for Future Research Residental Water Heating System Performance Approach 31

32 Opportunities for Future Research The overarching recommendation is to expand research on heater and system performance under conditions not explored within the scope this effort. ANSI efficiency testing can be expanded to include new water heater technologies suitable for commercial facilities including hybrid (combination of ministorage and tankless heater technologies) water heaters and tankless heaters operated in a boiler style configuration by utilizing a large volume storage tank to manage peak volume flows and recirculation systems. Impacts of recirculation through the water heater on thermal efficiency should also be explored with the control volume drawn around the heater itself to quantify real world heater operating efficiency. The distribution system configurations in the laboratory can be expanded by adding a demand circulation scenario and recirculation line lengthened from 200 to 400 feet to better represent distribution systems in medium sized full-service restaurants. Full-service restaurants are a great candidate for testing as major problems with performance are common in larger restaurants with dishwashers and the energy savings potential is much greater by optimizing the system (Fisher, D. 2007), (Delagah, A. 2010). Research can be expanded to test scenarios that improve hot water delivery performance at hand sinks without increasing energy use such as reducing pipe diameter in the branch and twig piping leading to the water using equipment or sink. Upon performing this recommended research, further recommendations can be made for incrementally improving water heater system efficiency. There are many ways to expand on the existing research in the laboratory and ATS will be meeting with stakeholders to build a roadmap for future testing. 32

33 Appendix A Heaters Under Test HEATER 1: High Efficiency Tank: A. O. Smith Cyclone Xi, Model #:BTH , 100 gallon, 199,900 Btu/h input, 95% TE HEATER 2: Standard Efficiency Tank: A.O. Smith Master-Fit, Model #:BTR , 100 gallon, 199,000 Btu/h input, 80% TE HEATER 3: High Efficiency Tankless*: Takagi Flash T-H1, 199,000 Btu/h input, 92% EF HEATER 4: Standard Efficiency Tankless*: Rinnai R94LSi, M/N REU- VA2535FFUD-UC, 199,000 Btu/h input, 82% Energy Factor 33

34 Appendix B Water Heater Thermal Efficiency Std. Eff Tank-Type 34

35 Appendix C Impact of Mean Tank Temperature on T.E. High Efficiency Tank-Type Water Heater 35

36 Appendix D Impact of Mean Tank Temperature on T.E. High Efficiency Tank-Type Water Heater 36

37 Appendix E Quantifying System Heat Loss and Correcting System Delivery Efficiency for Volume Per Test 37

38 Appendix F Quantifying System Heat Loss and Correcting System Delivery Efficiency for Volume Per Test 38

39 Appendix G Without Recirculation vs. Aquastat Delivery Temperature 39

40 Appendix H: Energy Performance Comparison: System Performance Line and Test Volume Normalization IE500 IETEST Energy Input QLOSS Energy Output OETEST OE500 40

41 Appendix I: Energy Performance Impact: Standard Efficiency Tank-Type Water Heater - RCx and Retrofit Measures 41

42 Appendix J: Energy Performance Impact: Summary of RCx and Retrofit Measures System Delivery Efficiency With Insulated Distribution System Hand 3 Comp Mop Lavatory Difference in S.D.E. vs. w/ Recirc w/ Insulation Base Case w/o Recirc 63.25% % w/ Recirc 53.85% X RCx Measure Disable Damper 48.79% % Timeclock 56.58% % Aquastat 58.25% % Point of Use - A 45.43% % Point of Use - B 54.32% % 160F Setpoint X X X X X X Partially Insulated Distribution System w/ Recirc 48.65% % System Delivery Efficiency Without Insulated Distribution System Hand 3 Comp Mop Lavatory Difference in S.D.E. vs. w/ Recirc w/o Insulation Difference in S.D.E. vs. w/ Recirc w/ Insulation Base Case w/o Recirc 54.17% % 0.32% w/ Recirc 45.86% X -7.99% RCx Measure Disable Damper 42.10% % % Timeclock 47.59% % -6.26% Aquastat 49.49% % -4.36% Point of Use - A 38.80% % % Point of Use - B 42.60% % % 160F Setpoint 45.35% % -8.50% 42

43 Appendix K Instantaneous Delivery Temp w/ Recirc 43