Trends in domestic hot water consumption in Estonian apartment buildings

Transcription

1 Proc. Estonian Acad. Sci. Eng., 26, 12, 1, 72 8 Trends in domestic ot water consumption in Estonian apartment buildings Teet-Andrus Kõiv and Alvar Toode Department of Environmental Engineering, Tallinn University of Tecnology, Eitajate tee 5, 1986 Tallinn, Estonia; teet.koiv@ttu.ee Received 16 September 25, in revised form 5 January 26 Abstract. Domestic ot water consumption trends in Estonian apartment buildings during te last 3 years ave been investigated. Measurement results sow tat te factual maximum consumption values are substantially less tan te design values. For dimensioning instantaneous eat excangers for domestic ot water eating a new load calculation formula is recommended. Key words: apartment building, domestic ot water, consumption profile. 1. INTRODUCTION In te 197s te domestic ot water consumption in residential buildings was relatively ig; for example, in te former Soviet Union 95 l/d per person or more [ 1,2 ]. Te latest investigations tell us about a decrease in domestic ot water consumption: in Russia l/d per person (as design values) [ 3 ], in Finland about 85 l/d per person [ 4 ] and in USA residential omes l/d per person [ 5 ]. Canges in te consumption profile are different in different countries. Tere are only minimal canges in domestic ot water consumption profile in Russia [ 6 ]. Nowadays, domestic ot water consumption profile of apartment buildings in Estonia [ 7 ] is close to consumption profiles in USA [ 8 ] and Denmark [ 9 ]. Te sare of eat consumption for water eating in Estonian apartment buildings in te general eat consumption as been about 2 4% during te last 3 years. Te larger numbers belong to te 197s. Te total eat consumption in apartment buildings as canged from 35 in te 197s to 2 kw/m 2 per year in

2 Te first investigation of domestic ot water consumption in te 199s was carried out in Tallinn in 1998 [ 1 ]. Te first more extensive analysis of domestic ot water consumption by te autors of te paper was made in 2 on te basis of te 1999 consumption data [ 11 ]. Te latest one was made in 25 [ 7 ]. 2. CHANGES IN DOMESTIC HOT WATER CONSUMPTION Te domestic ot water consumption dynamics in apartment buildings from 1999 to 24 is sown in Table 1. We can see a considerable decrease in consumption. In small cities of Estonia te domestic ot water consumption is about 15% less. Comparison of te weekly consumption data in 1974 and 25 is sown in Fig. 1. From 1974 to 25 te domestic ot water consumption in apartment buildings as decreased more tan tree times. Table 1. Domestic ot water consumption l/(m 2 d) in investigated apartment buildings from 1999 to 24 Consumption Average * Range * 44 l/d per person. d) Consumption, l/(m M T W T F Sat Sun Average Fig. 1. Domestic ot water consumption on weekdays and on average in 1974 and 24; te area is te general area of apartments. 73

3 3. DOMESTIC HOT WATER CONSUMPTION PROFILE Maximum domestic ot water consumption and consumption profile in apartment buildings were investigated in 1974 (using an experimental data logging system) and in 25 using impulse water meters (one impulse per one litre), wic were connected wit data loggers; te measurement scema is sown in Fig. 2. Te water consumption data collection of different apartment buildings was made during a week. During 3 years considerable canges in people s lifestyle ave taken place. To prove it, daily consumption profiles of two apartment buildings in 1974 and 25 are sown in Figs. 3 and 4. 1 impulse water meter, 2 datalogger, 3 data processing Fig. 2. Data measurement and processing system Consumption, l/ Time, Fig. 3. Consumption profile of a 9-apartment building in 1974 (on Monday). 74

4 Consumption, l/ Time, Fig. 4. Consumption profile of a 3-apartment building in 25 (on Tuesday). Te maximum ourly variation in domestic ot water consumption is caracterized by te ratio k of te maximum ourly consumption to te average ourly consumption of a week, wic is calculated as: k max avg G =, (1) G max avg were G is te maximum and G is te average ourly domestic ot water consumption of te week. Te dependence of k on te number of apartments in a building is sown in Fig. 5. k y = 8.76x Fig. 5. Te dependence of k on te number of apartments in te building. 75

5 In recent years great canges in te relative domestic ot water consumption during te weekend ave taken place. Te increase in te consumption during te weekend is not so considerable any more. In comparison wit te water consumption on workdays te rise in te weekend consumption in 1974 was 1.5 times wile now it is only 1.2 times. At present te daily consumption is caracterized by te morning maximum (Fig. 4) and it is more close to te consumption profiles in te West European countries [ 9 ] and USA [ 8 ]. 4. MAXIMUM CONSUMPTION AND A NEW LOAD CALCULATION FORMULA Te maximum domestic ot water consumption as decreased and is considerably lower tan tat calculated using [ 12 ] (Fig. 6). Calculation of te domestic ot water design flow rate in residential buildings is based on te sum of nominal flows of standard type of water outlets. Calculation is made using a grap, table or formula q q Q q A q Q q d = N + Θ( N ) + m Θ N, (2) were q d is te design flow rate of te domestic ot water (l/s), q N is te maximum flow rate of domestic ot water for water outlets (l/s), q m is te weigted mean flow rate of domestic ot water for water outlets (.2 l/s), Q is te sum of te nominal flow rates of domestic ot water for water outlets (nominal flow rates are.2 l/s for sower,.3 l/s for bat tube and.2 l/s for kitcen sink), A and θ are constants depending on te desired safety against overloading (for residential buildings A = 3.1 and θ =.15). Consumption, l/s y =.5123e.59x Measured Calculated Fig. 6. Measured and calculated (on te basis of EVS [ 12 ]) values of maximum domestic ot water consumption in different apartment buildings in

6 For calculating te domestic ot water load Φ for dimensioning instantaneous eat excangers, te following formula was derived: Φ = B( n +.2 n), (3) were n is te number of apartments, B is a coefficient tat takes into account te domestic ot water temperature ( B = 1. if ot water design temperature is 55 C, B = 1.1, if tis temperature is 6 C and B = 1.2, if tis temperature is 65 C). Equation (3) is valid for apartments wit one batroom and a kitcen. Figure 7 sows domestic ot water eating load values for dimensioning instantaneous eat excangers in different apartment buildings on te basis of Eq. (3). Figure 8 presents domestic ot water eating load design values calculated by formula (3), by te Estonian Standard EVS 835:23 (identical wit D1 te Finnis Construction Code), by SDHA (te Swedis District Heating Association) metod and by SNiP (te Soviet Construction Code). Calculation formulas are presented in te article Kõiv and Toode (21) [ 3 ]. In Fig. 8 we can see tat te results calculated by formula (3) are closer to te SDHA metod, te reason being a very close number of residents in apartments. Figure 9 sows design loads, calculated by formula (3), by te EVS/D1 metod and by te measured values in 25. We can see tat for large apartment buildings EVS and D1 give about twice iger loads., kw Φ By formula (3) Measured 25 Fig. 7. Domestic ot water eating load values for dimensioning instantaneous eat excangers in different apartment buildings, calculated using Eq. (3), and values calculated on te basis of measured domestic ot water consumption values. 77

7 , kw Φ EVS/ D1 SDHA SNiP Formula (3) Fig. 8. Domestic ot water eating load design values calculated by different metods: EVS Estonian Standard EVS 835:23; D1 Finnis Construction Code; SDHA Swedis District Heating Association; SNiP Soviet Construction Code SNiP , kw Φ By formula (3) Measured 25 EVS/D1 Fig. 9. Comparison of domestic ot water eating loads calculated by formula (3), by te EVS/D1 metod and on te basis of measured values. 78

8 5. CONCLUSIONS In te last 3 years great canges in domestic ot water consumption in apartment buildings ave taken place (Fig. 1). Te main reasons for te decrease in domestic ot water consumption are: consumption metering in apartments and payment for real consumption; increasing cost of water and eat; extensive renovation of domestic ot water systems, including renovation of te circulation; use of modern water saving equipment (taps, sowers). At te same time tere ave been considerable canges in maximum water consumption. Following tat a new metods for dimensioning instantaneous eat excangers in apartment buildings is recommended. Tis improves te control of domestic ot water temperature, especially in conditions of low external temperature, and decreases expenses on te equipment. ACKNOWLEDGEMENT Te autors are grateful to te Ministry of Economy and Communication for supporting te investigation. REFERENCES 1. Borodkin, J. D. and Dvoretskov, N. G. Profile of domestic ot water consumption in residential buildings and influence of te control of eat supply. Teplosnabzenie gorodov, Nautsnye trudy AKH imeni K. D. Pamfilova, 1973, No. 95, (in Russian). 2. Kõiv, T.-A. Experimental researc of domestic ot water consumption profiles by residents in Tallinn. Proc. TPI, 1977, No. 42, (in Russian). 3. Pukkal, V. Selection of equipment for measuring te volume and flow rate of water in domestic ot water systems. Inzenernye sistemy (AVOK Severo-Zapad), 22, No. 2(6), (in Russian). 4. Seppänen, O. Rakennusten lämmitys. Gummerus OY, Jyväskyla, Domestic Hot Water System Modeling for te Design of Energy Efficient Systems. NAHB Researc Center, USA, Pukkal, V. Calculation of domestic ot water consumption in existing residential buildings. Inzenernye sistemy (AVOK Severo-Zapad), 23, No. 2(1), (in Russian). 7. Toode, A. and Kõiv, T.-A. Domestic ot water consumption investigation in apartment buildings. Proc. Estonian Acad. Sci. Eng., 25, 11, Fairey, P. and Parke, D. A Review of Hot Water Draw Profiles Used in Performance Analysis of Residential Domestic Hot Water Systems Sonne, P. Peak saving. News from Danis Board of District Heating. 1994, No Kõiv, T.-A. Heat energy consumption in eating and ot tap water systems in apartment buildings. Proc. Estonian Acad. Sci. Eng., 1998, 4, Kõiv, T.-A. and Toode, A. Heat energy and water consumption in apartment buildings. Proc. Estonian Acad. Sci. Eng., 21, 7, Kinnistu veevärgi projekteerimine. EVS 835:23. Eesti Standardikeskus, Tallinn,

9 Muutustest Eesti kortermajade sooja vee tarbimises Teet-Andrus Kõiv ja Alvar Toode Sooja vee tarbimine ja selle ebaütlus sõltuvad elanike arjumustest ja seda mõjutavad maksustamine, kasutatavad seadmed ja süsteemi seisukord. Artiklis on esile on toodud väga suured muutused sooja vee tarbimises ja tarbimisrežiimis viimasel paarikümnel aastal Eestis. Ajavaemikus 1974 kuni 24 väenes sooja vee tarbimine üle kolme korra. Uurimistulemused näitavad, et sooja vee tarbimise tegelikud maksimumväärtused on kuni kaks korda väiksemad arvutuslikest. Sellest tulenevalt on esitatud uus valem sooja tarbevee soojendamiskoormuse määramiseks kiirveesoojendite dimensioneerimisel. 8