ASHRAE LV-11-002-2011 A New Study of Hot-Water Use in Canada.pdf

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1、2011 ASHRAE 673ABSTRACTIn 2007/2008 the Renewables and Integrated EnergySystems Group at Natural Resources Canada (NRCan), adepartment of the Canadian Federal Government, initiated anew study of residential hot-water use with the aim of deter-mining whether or not there had been any significant chan

2、gesince the last study conducted. The NRCan study utilized low-cost data loggers together with accurate flowmeters to monitorthe volume of hot water drawn every two to four seconds, fora period of approximately two to three weeks, at each test site.This study monitored 38 households in the greater O

3、ttawa areaand, as such, is believed to be the largest such study of its kindconducted since the earlier work completed by Perlman andMills (1985) or Werden and Spielvogel (1969a, 1969b).NRCan has now extended the hot-water use monitoring toother regions in Ontario, in collaboration with Union Gas,Lt

4、d., and with the assistance of Caneta Research, Inc., addinganother 36 households to the study. The new regions coveredincluded Hamilton, London, and Sudbury.As a result of our new study, we have found that peopleshabits have changed and that hot-water use today is quitedifferent to the assumptions

5、used in the current performancetest standards; for example, the total household average dailyhot-water volume appears to have decreased, the averagedraw volume flow rates are lower, and the average number ofdraws per day are much greater. The authors present the resultsof monitoring 74 households ho

6、t-water use and discuss theimplications of these results with respect to the water heaterperformance test standards and the derived energy factor.INTRODUCTIONIn Canada, approximately 347 PJ (3.3 1014Btu) ofenergy, or 9.5 billion m3(335 billion ft3) of natural gas equiv-alent, are used to heat water

7、for residential and commercial useon an annual basis, and this leads to approximately 18 mega-tons (18 megatons) of CO2equivalent GHG emissions.Given the relative difference in population size, the emissionsfrom the U.S. will be in the order of ten times that of Canada.The basis for the current wate

8、r-heating appliance perfor-mance standards in North America was established and cameinto effect about 17 years ago, during which time testing andmonitoring equipment has improved, water-heating technolo-gies have improved, and peoples habits have changed. Thishas led us (Natural Resources Canada) an

9、d others in NorthAmerica to ask the question, “Are these performance stan-dards still appropriate, and what changes could be made, ifnecessary, to make them more appropriate?” Given thatmodern test equipment is capable of logging and controlling atest to within a second, we could, if it seems approp

10、riate,change the draw schedule to a more realistic use pattern. In anymodified performance rating, we could also consider how theefficiency of a water heater may vary with how much hot wateris used on a daily basis. Prior to the initiation of this study, itwas thought that hot-water use may have dec

11、reased due to theintroduction of water metering, the widespread use of low-flow shower heads, the practice of cold-water clothes washing,and the common use of aerators on hot-water taps.One step in answering the above question was to comparethe real-life water-use patterns from a new field study to

12、thatof the water-draw patterns used in the current water heaterperformance standards, i.e., typically 6 draws of 40.6 L(10.7 gal) at a rate of 10.4 Lpm (3.0 gpm), each an hour apartA New Study of Hot-Water Use in CanadaM. Thomas, CEng, PEng A.C.S. Hayden, PEng O. GhiricociuMember ASHRAE Associate Me

13、mber ASHRAER.L.D. Cane, PEng R. Gagnon Member ASHRAEM. Thomas is a research engineer and A.C.S. Hayden is a science and technology director at CanmetENERGY, NRCan, Ottawa, Ontario,Canada. O. Ghiricociu is a technology research engineer at Union Gas, Ltd., Toronto, Ontario, Canada. R.L.D. Cane is a p

14、rincipal researchengineer and R. Gagnon is an assistant research scientist at Caneta Research, Inc., Mississauga, Ontario, Canada.LV-11-0022011. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (www.ashrae.org). Published in ASHRAE Transactions, Volume 117, Part 1. For

15、 personal use only. Additional reproduction, distribution, or transmission in either print or digital form is not permitted without ASHRAES prior written permission.674 ASHRAE Transactionsand then followed by 18 hours of standby. To that end, in 2007/2008, the Renewables and Integrated Energy System

16、s Groupat Natural Resources Canada (NRCan), a department of theCanadian Federal Government, initiated a new study of resi-dential hot-water use with the aim of determining whetherthere had been any significant change in hot-water use sincethe last study was conducted. The NRCan study utilized low-co

17、st data loggers together with accurate flowmeters to monitorthe volume of hot water drawn every two to four seconds, fora period of approximately two to three weeks, in each home.This first stage of the study monitored 38 households in thegreater Ottawa area. NRCan has now extended the hot-wateruse

18、monitoring to include 36 households in Hamilton,London, and Sudbury, in the province of Ontario. This secondstage of the study was conducted in collaboration with UnionGas, Ltd., and with the assistance of Caneta Research, Inc.,adding another 37 households to the study. With a total of 74test sites

19、monitored, our monitoring is believed to be the larg-est such study of its kind conducted since the earlier workcompleted by Perlman and Mills (1985), and by workconducted by L.G. Spielvogel.In Canada, the performance test standard for residentialgas-fired storage water heaters is the CSA P.3 (CSA 2

20、004a),for residential instantaneous water heaters its the CSA P.7(CSA 1998), and for residential electric storage water heatersits the CSA C191 (CSA 2004b). In the US, the performancetests for the above three water heater types is specified in theDOE Code of Federal Regulations, Title 10, Part 430,

21、Appen-dix E to Sub-Part B. The DOE test is also reflected by ANSI/ASHRAE Standard 118.2-2006, Method of Testing for RatingResidential Water Heaters. The ASHRAE standard is gener-alized and has the specific test parameters required by theDOE listed in an appendix to that document (Annex A). InCanada,

22、 the performance test for electric storage water heat-ers, the CSA C191, is significantly different to that used in theU.S. because it is a standby energy loss only test. Exceptingthe CSA C191 test, each of the other performance tests uses aparameter called the energy factor (EF) as a measure of eff

23、i-ciency. The EF is calculated as the ratio of the energy deliveredto the end user as hot water, divided by the total energyconsumed by the water heater over a 24-hour period in a simu-lated use test.Because of the different operating characteristics of stor-age and instantaneous water heaters, chan

24、ges to the totalvolume of hot water drawn per day and the draw scheduleemployed in the performance test standards will have differenteffects on the energy factor derived for each of these producttypes. For example, The Davis Energy Group has found thatthe real-use efficiency of instantaneous water h

25、eaters can bereduced by 8.8% when regular infrequent short draws of hotwater are made. NRCan has conducted its own study, whichhas confirmed the Davis Energy Groups noted drop in effi-ciency due to cyclic operation for tankless water heaters, asshown in Table 1. It is also known that the real-use ef

26、ficiency of storagewater heaters is greatly affected by the length of time theyspend on standby in comparison to the time spent in operation.The efficiency of a storage water heater could easily bereduced by 10 percentage points if the daily use of hot wateris reduced by about 22 gal. Using the curr

27、ent test standards, theefficiency (EF) of installed gas-fired storage water heaters inNorth America ranges from about 50% to 64% (up to 86% ifcondensing) and, in comparison, the efficiency of gas-firedinstantaneous water heaters ranges from 80% to 85% (up toTable 1. Efficiency Test Data for a Tankle

28、ss Water Heater under a Variety of Cyclic ConditionsTest Condition EfficiencySteady-state high input (flue loss) 84Steady-state low input (flue loss) 75P.7 (135F (57C) water, high and low input) 791 on/1 off, 135F (57C) water, 1.0 U.S. gpm (3.74 Lpm) 711 on/3 off, 135F (57C) water, 1.0 U.S. gpm (3.7

29、4 Lpm) 681 on/10 off, 135F (57C) water, 1.0 U.S. gpm (3.74 Lpm) 67Test 1, 115F (46C) water, 1.3 U.S. gpm (5.0 Lpm), 1.2 min on/15 off 64Test 2, 115F (46C) water, 1.3 U.S. gpm (5.0 Lpm), 0.75 min on/15 off 59Test 3, 115F (46C) water, 1.3 U.S. gpm (5.0 Lpm), 200 L drawn 68Test 4, 130F (54C)water, 1.9

30、U.S. gpm (7.0 Lpm), 1.33 min on/10 off 69Test 5, 130F (54C) water, 2.6 U.S. gpm (10 Lpm), 1.25 min on/10 min off 70Test 6, 180F (82C) water, 1.3 U.S. gpm (5.0 Lpm), 1.4 min on/15 min off 752011 ASHRAE 67598% if condensing). As discussed above, however, in the realworld these efficiencies may be sign

31、ificantly different depend-ing on how the water heater is used in practice. It can be seen that in any potential redesigning of the waterheater performance test standards it will be necessary to takeinto account the parameters that can affect the operating char-acteristics of the different water hea

32、ter types and also to havean accurate understanding of the general populations dailyhot-water use and usage habits. The results of this study,presented here, aims to help provide current information withregards to residential hot-water usage patterns.EQUIPMENT USED AND METHODOLOGYEquipment UtilizedT

33、he equipment employed in the hot-water use study canbe found in Appendix A.General MethodologyThe following general methodology was used. Furtherdetail can be found in Appendix A.1. Assemble equipment required (test to ensure function-ality).2. Recruit volunteers.3. Group volunteers by geographic lo

34、cation.4. Install monitoring equipment and monitor for a minimumof two weeks.5. Provide each homeowner with a questionnaire.6. Remove equipment and restore to original condition.7. Process data and analyze results.Information is presented relating to the key parameters,used in the CSA P.3, CSA P.7,

35、the DOE, and ANSI/ASHRAEStandard 118.2 performance test standards (CSA 2004a; CSA1998; DOE 2004; ASHRAE 2006), i.e., average daily hot-water use, the average number of hot-water draws per day, theaverage volume of hot water used per draw, and the averagedraw volume flow rate. RESULTS AND DISCUSSIOND

36、uring the first stage of the study we set the data loggerto record hot-water use every two seconds in order to definewith some accuracy when different water draws were takingplace; however, we found that there were many single pulseevents throughout the day, at all of the test sites monitored,with t

37、he total number of draws exceeding 200 in most cases.In discussing our preliminary results with other experts in thefield, we decided to eliminate all of these single pulse eventsfrom our data (this had a significant effect on the number ofdraws per day but only changed the average volume of hotwate

38、r used per day by less than 1% at each test site). It wasthought that these single pulse occurrences were probably dueto water pressure changes and/or convection currents in thewater pipes, triggering a pulse at the flowmeter. Anythingmore than a single pulse by itself was considered to be a genu-in

39、e hot-water draw.Daily Hot-Water UseOne key result from the study indicated that hot-water useappeared to have reduced over the last 17 years (as shown inFigures 1 and 2), with 83% of the monitored test sites usingFigure 1 Average daily hot-water use.676 ASHRAE Transactionsless than 243.4 L/day (64.

40、3 gal/day) at an average value of185.6 L (49 gal) per day. This is approximately 60 L (or 16 gal)per day less than the current performance test standardsassume. This change in total daily volume of hot water used isunlikely to have any impact on a gas-fired tankless waterheater, but because of the l

41、onger duration on standby, a gas-fired storage water heater may see a reduction in EF on theorder of 0.10, i.e., a 10 percentage point reduction in its effi-ciency, as discussed in the introduction.The study median (Figure 2) was found to be very similarto the study average value (Figure 1) for the

42、daily volume ofhot water used per household, indicating a possible normaldistribution; however, normality will need to be definitivelyverified through lengthier analysis, at a later date. Note that thedata collected from test site 30 in the second stage of this studywere corrupted and could not be u

43、sed in our analysis.All othersites had usable data. Test Site 12 data were examined becauseof its high hot-water use, but only one unrelated error wasfound in the data, which did not account for the high use, andseveral distinct large-volume water draws were identifiedmanually. Family Size and Hot-W

44、ater UseStatistics Canada Data indicates that the average familysize has decreased from 3.7 down to 3.0 over the last 35 yearsor so. From our study, family size did not seem to be a signif-icant indicator of daily hot-water use. For comparison to otherpopulations, the family configuration of the stu

45、dy participantsis shown in Figure 3. In this graph, the key indicates thenumber of adults and children per household. It should benoted that some participants did not provide this informationto us and thus could not be included in the chart. The onlyapparent conclusion to be made from this informati

46、on was thatyou could not assume that smaller families use less hot waterand that larger families use more hot water.Water Heater Type and Hot-Water UseIt has been speculated that end users with tankless waterheaters use more hot water than those with storage water heat-ers. This thought arises from

47、the fact that a tankless waterheater has an endless supply of hot water, whereas the supplyof hot water in a storage water heater is effectively limited bythe tank capacity. Another contributing factor could also be thenature of the operation of a tankless water heater; i.e., thewater flow rate must

48、 reach a pre-set minimum level before theburner fires to start heating the water; subsequently, there isalso a short delay ( 30 s) before the water is heated up totemperaturethese actions serve to increase the amount ofhot water used. In the first stage of the study, only one test sitehad a tankless

49、 water heater (Site # 5) and, as such, it was notpossible to draw any conclusions with regards to hot-water useand appliance type. However, in stage 2 of this study, 10 testsites had tankless water heaters installed (Sites 1, 2, 3, 4, 6, 8,10, 14, 16, and 17), with the rest being storage water heaters,and this has allowed us to investigate the differences betweentankless and storage water heater hot-water use. On a house-hold basis, it can be seen that average daily hot-water use isreduced for both technologies in comparison to the assump-tion used in the p