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Greenhouse Gas emission from high-rise buildings has been increasing mainly due to excessive energy consumption of the HVAC system, structural system and electrical system. Electricity consumption for pump system accounts for 15% of total electricity usage in building. Therefore the reduction of electricity in operation is crucial to the overall reduction of GHGs in urban areas.
Journal of Science and Technology in Civil Engineering NUCE 2018 12 (3): 123–131 OPTIMIZATION TO WATER SUPPLY SYSTEM DESIGN AND OPERATION SCHEME IN HIGH RISE BUILDINGS Nguyen Lan Huonga,∗, Nguyen Viet Anha , Dang Thi Thanh Huyena , Tran Hoai Sona , Dinh Viet Cuonga a Faculty of Environmental Engineering, National University of Civil Engineering, 55 Giai Phong road, Hai Ba Trung district, Hanoi, Vietnam Article history: Received 12 March 2018, Revised 03 April 2018, Accepted 27 April 2018 Abstract Greenhouse Gas emission from high-rise buildings has been increasing mainly due to excessive energy consumption of the HVAC system, structural system and electrical system Electricity consumption for pump system accounts for 15% of total electricity usage in building Therefore the reduction of electricity in operation is crucial to the overall reduction of GHGs in urban areas In this study, a lab-scale experiment was conducted to test the electricity consumption in applying different design approaches; the energy efficiency of the system was calculated Finally, this study proposes the advanced water supply design scheme to reduce electricity consumption of the pump system Keywords: Water supply system; high-rise building; energy consumption c 2018 National University of Civil Engineering Introduction Currently, the process of urbanization has led to a major change in the urban view with rapid growth of high-rise buildings and skyscrapers Efficient energy use in these buildings in order to reduce emissions and ensure green building elements is a critical demand in many municipalities in Vietnam [1] According to recent statistics [2], the total energy consumption of buildings accounts for 40–70% of the energy supply for the municipality, in which the high-rise buildings such as hotels, commercial buildings, etc consume about 35–40% of this part The cost of electricity to operate the pumps for water supply systems are relatively high (20-40%), based on a study of the 20 - year - life - cycle cost of water supply system in high-rise buildings [3] Burton [4] showed that raw and treated water pumping can account for up to 95% of water utility’s energy use Similarly, the Electric Power Research Institute [5] suggests that more than 85% of the energy use in water supply operations is consumed by pumps alone While Wong [6] rendered that in most cases, the energy efficiency for highrise water supply system is below 25% and more than 75% input energy is wasted Half of the energy loss attributes to water pumps ∗ Corresponding author E-mail address: huongnl2@nuce.edu.vn (Huong, N L.) 123 Huong, N L et al / Journal of Science and Technology in Civil Engineering It is found that two main kinds of systems may cause significant energy wasted [7] First is a kind of system that incorporates one pump to run continuously, even during low-flow or no-flow periods This system utilizes a thermal bleed solenoid valve to dump water that is overheated in the pump casing due to the impeller operating below the demand flow rate Both energy for pumps and water for pumping are wasted in this case The second is a kind of system that generates a single water pressure for the entire building that is high enough to satisfy the upper-level fixtures and then reduce that pressure through pressure-reducing valves to satisfy lower-level pressure zones in the building In this case, energy is wasted via the pressure-reducing valves Study on high-rise system shows that the design of water supply system for high-rise buildings is often not optimal, so that pump heads are usually 1.2–1.3 times higher than the height of the building (> 100 m H2 O), the pumping efficiency is very low at only 40–60%, electricity used for O&M is very high, resulting in high rate of energy waste and expense lost According to [8], optimization of the design and operation of indoor water supply and boosting system in mega cities of China can save 25% of energy consumption and reduce annual emission by 8,600 tCO2 e Energy saving and use of efficient energy source in high-rise buildings not only reduces budgets of investors but also comply with the Vietnam Government’s strategies for energy security, sustainable development and environment protection Therefore, the objectives of this research are (1) to study the electricity consumption and energy efficiency of different design approaches using lab-scale booster system; (2) to propose the advanced water supply design scheme to reduce electricity consumption of the pump system for highrise building Materials and Method 2.1 Lab-scale experiment Two typical systems (roof tank system and booster system) [9] for water supply in high-rise buildings were chosen for the experiment (Fig 1) (RT) (R) (R) (P1) (BP)- Scheme Scheme Figure Water supply systems in high-rise buildings Figure Water supply systems in high-rise buildings Scheme City water supply to reservoir (R) at the basement of building, water is then lifted from reservoir (R) to the roof-tank (RT) on the most top floors by pump system (P1) at the basement The water tank will supply water to the below floors at the same time Scheme water Cityfor water supply to The reservoir (R)supplying at the basement building, then(P2); lifted from2 City water is reserves the upper floors water tank water to theof upper floors bywater boosterispump Scheme provided reservoir at the (RT) basement will supply water with constant pressure to all the floors reservoir (R)totoa the roof-tank on of thebuilding most topBooster floorspump by pump system (P1) at the basement continuously with the support of Booster Water is pumped from the water tank pump to the(BP) upper floors by booster pump (P2); A lab-scale experiment is set up to analyse the pump efficiency of different water supply system designs in high-rise building ( 124 Figure 2) The system consists of : 01 water tank with dimension BxLxH = 1250 x 750 x 350 mm, storage capacity of 280 liter; 02 (R) (R) (BP)(P1) Huong, N L et al / Journal of Science and Technology in Civil Engineering Scheme Scheme Figure Water supply systems in high-rise buildings Scheme City water is provided to a reservoir at the basement of building Booster pump will Scheme City constant water supply to reservoir (R)the at the basement of building,bywater is then lifted from reservoir (R) to the roofsupply water1.with pressure to all floors continuously booster pumps (BP) tank (RT)Aon the most top floors by pump system (P1) at the basement The water tank will supply water to the below floors at the lab-scale experiment is set up to analyze the pump efficiency of different water supply system same time reserves water for the upper floors The water tank supplying water to the upper floors by booster pump (P2); Scheme designs in high-rise building (Fig 2) The system consists of: 01 water tank with dimension B × City water is provided to a reservoir at the basement of building Booster pump will supply water with constant pressure to all the L continuously × H = 1250with × 750 × 350ofmm, storage of 280 liter; 02 vertical centrifugal pump unit with floors the support Booster pumpcapacity (BP) variable speed motor, each unit has the capacity of Q p = 3.5 m3 /hr and head Hmax = 30 m; pump A lab-scale experiment is set up to analyze the pump efficiency of different water supply system designs in high-rise building motor P = 0.37 kW The pump unit is installed in parallel on the pump base, connected with the inlet (Fig 2) The system consists of : 01 water tank with dimension BxLxH = 1250 x 750 x 350 mm, storage capacity of 280 liter; 02 pipecentrifugal D75 andpump discharge D75 Onmotor, the discharge pipe, were water meter (Grundfos, 0.6-12 vertical unit withpipe variable speed each unit has the there capacity of Qp= 3.5 m /hr and head Hmax=30m; pump motor m /hr),The pressure gauge (Grundfos, 0-10 atm), pressure sensor with (Danfoss, atm), Watt pipe meter P=0.37kW pump unit is installed in parallel on the pump base, connected the inlet 0-10 pipe D75 andand discharge D75 On the discharge pipe, there (Grundfos, 0-10 atm), pressuresystem sensor (Danfoss, 0-10 (Grundfos) Atwere onewater end meter of the(Grundfos, discharge0.6-12m3/hr), pipe, total pressure watergauge tap was installed The pump was atm),controlled and Watt meter (Grundfos) At one end of the discharge pipe, total water tap was installed The pump system was controlled by by the control panel Grundfos HYDRO-MPC E2XCRE3-05, the screen indicates various the control panel Grundfos HYDRO-MPC E2XCRE3-05, the screen indicates various system configurations such as: set up pump het system configurations such as: set up pump het (atm), actual pump head (atm), water volume (m3 /hr), (atm), actual pump head (atm), water volume (m3/hr), and electricity consumption (kW), percentage of motor speed to the full speed of electricity consumption (kW), percentage of motor speed to the full speed of 2950 r/min (%) 2950and r/min (%) Figure Lab-scale pump system outline and photo Figure Lab-scale pump system outline and photo 2.2 Pump configurations and data monitoring 2.2.1 Pump curves The pump operation curves at different operation modes are constructed by changing the pump discharge output through PLC unit The pump speed varies at 95%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50% of the full speed The consumption pattern was changed by opening the valves on the discharge pipe The pumps operate individually and in parallel, the output parameters were recorded and the curves were constructed as shown in Figs and 2.2.2 Pump system configuration Two lab-scale experiments are built: (1) Roof tank system: Q= m3 /h, h = 20 m, Tank volume m3 ; (2) Booster pump system, in which (2a) the first booster pump system with Q p = m3 /h, h = 20 m; (2b) the second pump system with Q p = 5.85 m3 /h, h = 10 m Both systems are run with the different Peak factor: Kh = 2.5; 2; 1.8 ([10, 11]) 125 a.Pump Pumpcurves curves a The pump operation curves at different operation modes are constructed by changing the pump discharge output through PLC unit The pump speed varies at 95%, 85%,operation 80%, 75%, 70%, 55%, 50% of the the pump fullthe speed The consumption wasPLC changed Thepump pump operation curves at different operation modes are 60%, constructed by changing pump discharge outputpattern through unit The The operation curves at90%, different modes are65%, constructed by changing discharge output through PLC unit The pump speedthe varies 95%, 90%, 85%, 80%, 75%, 50% full The speed The consumption pattern was changed by opening valves on the discharge pipe pump speed varies at at 95%, 90%, 85%, 80%, 75%, 70%,70%, 65%,65%, 60%,60%, 55%, 55%, 50% of the of fullthe speed consumption pattern was changed byopening openingthe thevalves valves discharge pipe by onon thethe discharge pipe The pumps operate individually and in parallel, the output parameters were recorded and the curves were constructed as shown in Figs pumps operate individually and in the parameters were recorded the were curves were constructed The pumps individually andL inetparallel, the output parameters were recorded theand curves constructed as shownas in shown Figs in Figs Huong, N al.parallel, / Journal of output Science and Technology inand Civil Engineering 3The and operate 33and and4.4 Huong, N L et al./ Journal of Science and Technology in Civil Engineering Efficiency, Head, configurations m 2.2 Pump and data % monitoring Efficiency, %% Efficiency, Head, Head, m m Power, kW a Pump curves Power, kW Power, kW The pump operation curves at different operation by Two changing theoperate pump discharge output through PLC unit The Pump11operates operates individually with speed (b) Two pumps operate in parallel with fullspeed (a)(a)Pump individually withfull fullmodes speedare constructed(b) pumps in parallel with fullspeed (a) Pump Pump1at1operates operates individually with full speed (b) Two pumps in parallel fullspeed (a) individually full speed (b)the Two pumps operate in parallel withwith fullspeed pump speed varies 95%, 90%, 85%, 80%,with 75%, 70%, 65%, 60%, 55%, 50% of full speed Theoperate consumption pattern was changed by opening the valves on the discharge pipe Figure Pump operation curves Figure 3.Figure Pump3.operation curvescurves Pump operation Figure Pump were operation curves The pumps operate individually and in parallel, the output parameters recorded and the curves were constructed as shown in Figs and kW kWkW (a) Head-Discharge curve (b) Power-Discharge curve Figure Pump operation curves when operating in parallel with different operation modes (variable speed pump) (a) Head-Discharge curve (b) Power-Discharge curve (a) Head-Discharge curve (b) Power-Discharge curvespeed pump) Figure Pump operation curves when operating in parallel with different operation modes (variable (a) Head-Discharge curve (b) Power-Discharge curve Efficiency, % curves when operating in parallel with different operation modes (variable speed pump) operation Head, mFigure Pump Power, kW Figure Pump operation curves when operating in parallel with different operation modes speed pump)(b) Two pumps operate in parallel with fullspeed (a) Pump operates individually with full speed (variable Figure Pump operation curves 2.2.3 Experiment process kW Roof-tank system: From the control panel, set the pump operation at the set point with: Q p = m3 /h, h = 20 m Maintain the operation and record the electricity consumption data by hours in 24 hours Booster pump system: From the peak-factor data, each hour set the operation point with corresponding Q p and h The water discharge was controlled by the water tap For each value in an hour, electricity consumption was recorded in 24 hours 126 (a) Head-Discharge curve (b) Power-Discharge curve Figure Pump operation curves when operating in parallel with different operation modes (variable speed pump) 3 Huong, N L et al / Journal of Science and Technology in Civil Engineering 2.2.4 Pump efficiency Pump efficiency is calculated as followed: Pump Hydraulic Efficiency (η pump , %) = Pump Hydraulic Power Output (kW) × 100 Pump input Shaft Power (kW) (1) The Pump Hydraulic Power Output is calculated for each design systems with formula as followed: N pump = ρ×g×H×Q (kW) 102 (2) in which: H: total head (m); Q: flowrate (m3 /s), ρ: density of the fluid (kg/m3 ); g: acceleration due to gravity (m/s2 ) Pump output Shaft Power is measured using voltage and current meter Head and Flow are recorded based on information display on the control panel of the pump system 2.3 Case study Based on the lab scale data, we design water supply system for a commercial apartment building (35 floors, basement) with 03 different design approach: - Roof-tank system 1.1: City water supply to reservoir (R) at the basement of building Water is then lifted from reservoir (R) to the water tank (WT) on the most top floors by pump system (P1) at the basement The water tank will supply water to the below floors at the same time reserves water for the upper floors The water tank supplying water to the upper floors by booster pump (P2) The system is divided into 04 zones (roof tank system) - Intermediate-tank system 1.2: City water was stored in a reservoir at the basement of building Water supply system is divided into different water pressure zones Each zone consists of 15-20 floors Every zone has a water tank and served by its own booster pump The pump only supplies water to the tanks of the above zones At the most top-floor a booster pump is installed In case of emergency, electricity breakdown, the tank will be able to provide water in12 hours (intermediate tank system) - Booster pump system 1.3: City water is provided to a reservoir at the basement of building Booster pump will supply water with constant pressure to all the floors continuously with the support of Variable Frequency Drive (VFD) The system consists of 02 sets of booster pumps to supply water to 02 pressure zones (Booster system) 2.4 Life-cycle cost Life cycle cost calculations for pumping systems of a 35 floor-building are conducted with three parameters taken into account: (i) capital costs; (ii) Maintenance cost and (iii) Operation costs - Capital cost for pump system, reservoir, water tank, piping and valves, Ci , is obtained from the manufacturer of the system supplying equipment with the equivalent capacity - Maintenance costs - Cm is obtained from manufacturer (estimation for booster sets is 50% of booster’s initial purchase price, pipe and pressure reduction valves 5% of initial investment, roof, base and break tanks 20% of tanks initial costs) Operation cost - Energy costs - Ce : Energy consumption is the result obtained from lab-scale experiment So the Life cycle cost (LCC) is the sum of the three components: LCC = Ci + Cm + Ce 127 (3) Huong, N L et al / Journal of Science and Technology in Civil Engineering Results and discussion 3.1 Experimental results Huong, N L et al./ Journal of Science and Technology in Civil Engineering Huong, N L et al./ Journal of Science and and Technology Civil Engineering Comparing the Energy consumption between roof tank pump in booster systems are showed in Fig Overall, the energy consumption for roof tank system was about 30% higher than that of booster pump system This result is consistent with the previous study by [2] The explanation lies Results discussion in the and fact the water is often pumped through where it is required (extra energy applied) and a Results andthat discussion 4.1 Experimental results number of pressure valves haveThe to be installed The energy consumption in the maximumnumber of pressure reducing valvesreducing have to be installed energy consumption in the maximum-water-using day of booster system 4.1 Experimental results was reducedwater-using around 27% to 33% day of booster systembetween was reduced to 33% Comparing the Energy consumption roof tank around and pump27% booster systems are showed in Fig Overall, the energy Comparing the Energy consumption between roof tank and pump booster systems are showed in Fig Overall, the energy consumption for for roofroof tanktank system waswas about 30% higher thanthan thatthat of booster pump system This result is consistent with thethe previous consumption system about 30% higher of booster pump system This result is consistent with previous study by [2] The explanation lies in the fact that the water is often pumped through where it is required (extra energy applied) andand a a study by [2] The explanation lies in the fact that the water is often pumped through where it is required (extra energy applied) number of pressure reducing valves have to be TheThe energy consumption in the maximum-water-using dayday of of booster system number of pressure reducing valves have to installed be installed energy consumption in the maximum-water-using booster system waswas reduced around 27%27% to 33% reduced around to 33% kWh kWh Peak-factor K Roof-tank Roof-tank Booster Booster Figure Electricity consumption of two water supply systems with different Kh in the maximum-water-using day Figure Electricity consumption of two water supply systems with different Kh the maximum-water-using day consumption of the systems changes closely with Peak-factor K the Peak-factor K electricity Studying the working chart of direct booster pump in systems shows that the water use patterns according to the different non-harmonic water use coefficients Figure Electricity consumption of two water supply systems with different Kh K inh the maximum-water-using dayday Figure Electricity consumption of two water supply systems with different in the maximum-water-using The pumps are controlled by the inverter system that when changing the flow by closing orthe opening the valves, the speeds of pump Studying the working chart ofso direct booster pump systems shows that electricity consumption are changed of automatically to suit the installation pressure of the system The pump efficiency is still higher than 50%changes (Figure Studying the working chart of direct booster pump systems shows that the electricity consumption of the systems the Studying systemsthechanges with booster the water patterns to theconsumption different non-harmonic working closely chart of direct pumpuse systems shows according that the electricity of the systems changes 6, 7, 8).The high efficiency of pump isaccording from 40% to 55% (Figure 7) The water pump efficiency reduces to under 10% in the low water use closely withwith therange water use patterns to the different non-harmonic use coefficients closely the water use patterns according to the different non-harmonic water use coefficients water use coefficients period time (From am to am) (Figure 6, Figure 8), at this period time the flow is very low compared to the average flow, but the The pumps are are controlled by the inverter so that when changing flow bychanging closing opening thethe valves, thethe speeds The pumps arecontrolled controlled by thesystem inverter system so thatthework when the flow by closing or ofwith The pumps by the inverter system so that that when changing the flow by or opening valves, speeds of the pump is still working with the installation pressure point so the pumps in theclosing lowor efficiency zone However, pump are are changed automatically to suit the the installation pressure of the system TheThe pump efficiency is still higher than 50% (Figs 6, 6, 7, 7, pump changed automatically to suit installation pressure of the system pump efficiency is still higher than 50% (Figs valves, theconsumption speeds of pump are system changed automatically installation operation in opening 24 hours, the the electricity of booster is much lower thanto thesuit roofthe tank system pressure of 8).The highhigh efficiency range of pump is from 40% to 55% (Fig 7) 7) TheThe pump efficiency reduces to to under 10% in in thethe low water useuse 8).The efficiency range of pump is from 40% to 55% (Fig pump efficiency reduces under 10% low water the system The pump efficiency is 8), still higher than (Figs 6,low 7, 8).Thetohigh efficiency range of period time (From am to 5toam) (Figs and 8), at this period time the50% flow is very low compared the average flow, but thethe pump is is period time (From am am) (Figs and at this period time the flow is very compared to the average flow, but pump iswith from to 55% (Fig.point 7) The pump efficiency to under 10% in the low water usein in stillpump working the40% installation pressure so that thethe pumps work in the lowlow efficiency zone However, with thethe operation 2424 still working with the installation pressure point so that pumps work inreduces the efficiency zone However, with operation hours, the the electricity consumption of booster system is much lower than thethe roofroof tank system hours, electricity consumption of booster system is much lower than tank system Figure Electricity consumption of booster pump Figure Electricity consumption of booster pump system with peak factor Kh=2.5 system with peak factor Kh=2.0 Figure Electricity consumption of booster system with Figure consumption of of booster pump system with Figure consumption of booster pump system with Figure Figure Electricity consumption booster pump system with Figure Electricity Electricity consumption ofpump booster pump Electricity Electricity consumption of booster pump peak factor Kh=2.5 peak factor K =2.0 peak factor Kh=2.5 peak factor K =2.0 h h system with peak factor Kh = 2.5 system with peak factor Kh = 2.0 128 Huong, N L et al / Journal of Science and Technology in Civil Engineering period time (From am to am) (Figs and 8), at this period time the flow is very low compared to the average flow but the pump is still working with the installation pressure point so that the pumps work efficiency zone However, with theEngineering operation in 24 hours, the electricity consumption Huong, N L.inetthe al./ low Journal of Science and Technology in Civil of booster system is much lower than the roof tank system s 3.2 Case study results e study m can 0, 11): shows that the optimization of the The result from case study shows that the optimization of the be studied under various design water supply system can be studied under various design approaches (Figures 9, 10, 11): as lowest initial- costs: less investment for System 1.1 has lowest initial costs: less investment for 3.2 Case study results n contrast, this systempump has highest electricity system, tanks In contrast, this system has highest all of the pump power is used liftconsumption water electricity because all of theofpump The result from tocase study to shows that the optimization the power is usedsystem to lift water the topunder floors water supply can betostudied various design - compared System 1.2 higher initial costs compared to system (Figures 9, has 10, 11): higher initialapproaches costs to system 1.1 - 1.1 System 1.1 has costs: investmentintermediate for because of lowest higherinitial costs for less purchasing ts for purchasing intermediate pump systems pump system, tanks In contrast, this system hasthe highest pump systems and break tanks, but total LCC he total LCC reduces because the consumption electricity because all of the pump power electricitybecause reduces the electricity consumption cost uces is used to lift water to the top floors reduces - because Systemof1.2 higher initial costs compared to system highest initial costs the has highest costs 1.1 because of higher costs for purchasing intermediate Figure Electricity consumption of booster pump system The booster pump sets equipped with frequency System 1.3 has highest costs of the highest 8.and Electricity consumption of booster pump system Figure with peak8.factor Kh = 1.8 consumption of boost pump Figure systems break initial tanks, but the because total LCC Electricity with peak factor Kh=1.8 xpensive than the normal pump sets However, costs for pump installation The booster pump sets equipped reduces because the electricity consumption cost system with peak factor Kh=1.8 and construction costswith reduce because there is no frequency converter is more expensive than the normal reduces in the system In addition, electricity consumption the lowest compared the other systems The results pumpthesets However, other iscosts for pipes and toconstruction Case study results consumption for3.2 this system can reducedinitial by 1.6costs times Regarding the electricity consumption per volume - booster System 1.3 has highest highest costs reduce because there is nobecause need of forthe break tanks in the In consumption addition, theofelectricity consumption is Figure system Electricity booster pump costs for pump installation The the booster pump sets(Fig equipped , the booster systems consume much times lesssystems then other systems 10) that compared to6.1 the other The results show electricity consumption for this booster system can red system with peak factor Kh=1.8 The result fromconverter case study shows thatthan thethe optimization of the water supply system can besystems studiedconsume mu with frequency is more expensive normal times Regarding the electricity consumption per volume of water consumption, the booster gain are similar to thosepump in previous study [3,other 13] in which they that the booster system and intermediate sets.design However, costs for pipesfound construction underless various approaches (Figs 9,and10, 11): then the other systems (Figure 10) ior to the roof tank solution when it comes to is initial investment, maintenance and energyInefficient operation costs- both reduce because there no need for break tanks in the system addition, the electricity consumption is the lowest System 1.1 has lowest initial costs: less investment for pump system, tanks In contrast, ndered to explain, for instance, booster sets and low pressure levels can create compared to theconfigurations other systems.with Theseveral resultsbooster show that electricity consumption for this booster system can reducedthis by 1.6 These findings again are similar to those in previous study [3, 13] in which they found that the system times Regarding the electricity consumption per volume of water consumption, the booster systems consume muchto 6.1the timesand interm here is little or system no flow, while break tanks made it possible to use water on stock all in order to adapt to power peak flow has highest electricity consumption because of the pump is used to liftbooster water system are superior the roofcantank solution -water bothatwhen it comes to initial investment, maintenance and energy efficien less then thetoother systems (Figure 10) e two booster system and intermediate systems provide enough acceptable low power consumption top floors Some reasons were rendered to explain, for instance, booster configurations with several booster sets and low pressure level -findings System 1.2there has higher initial costswhile compared system 1.1 higher costs purchasThese again are similar to those in previous study [3, 13] to in whichmade they found that theof booster system andfor intermediate tank to adapt t even pressure when is little or no flow, break tanks it because possible to use water on stock in order system are superior to the roof tank solution - both when it comesbut to initial investment, maintenance and energy efficient operation situations Thus, these two booster system and intermediate systems can LCC provide enoughbecause water atthe acceptable low power ing intermediate pump systems and break tanks, the total reduces electricity Some reasons were rendered to explain, for instance, booster configurations with several booster sets and low pressure levels can create consumption even pressure whencost therereduces is little or no flow, while break tanks made it possible to use water on stock in order to adapt to peak flow situations Thus, these two booster system and intermediate systems can provide enough water at acceptable low power consumption Construction (tanks) US$400,000 Pipe & PRVs US$400,000US$300,000 Pump set Sy st em US$300,000US$200,000 US$200,000 st em US$100,000 US$100,000 l cost for different water supply systems US$- US$Figure 10 Operational cost (mostly electric consumption) for System the total life span of 20 years System System 1.1 System System System 1.2 1.3 1.1 1.2 1.3 Figure 10 Operational cost (mostly electric consumptio Figure 10 Operational cost (mostly electric the Figure 10 Operational cost (mostly electric Co total lifeconsumption) span of 20for years Figure Capital cost for different water supply systems kW/m3 kW/m3 6.0 6.0 4.0 4.0 2.0 2.0 US$500,000 US$500,000 US$400,000 US$400,000 129 US$300,000 US$300,000 US$200,000 US$200,000 US$100,000 US$100,000 US$US$3 8.0 8.0 total 20 years consumption) forlife thespan totaloflife span of 20 years systems Figure Capital cost for different water supply Figure Capital cost for different watersystems supply đờ Co Maintenance Mainten Operation Operati Construction Constru US$400,000 US$400,000 US$300,000 US$300,000 US$200,000 Huong, N L et al / Journal of Science and Technology in Civil Engineering US$200,000 US$100,000 - System 1.3 has highest initial costs because of the highest costs for pump installation The US$100,000 booster pump sets equipped with frequency converter is more expensive than the normal pump sets US$However, other costs for pipes and construction costs reduceUS$because there is no System need forSystem break System System System System tanks in the system In addition, the electricity consumption is the lowest compared to the other 1.1 1.2 1.3 1.3 by 1.6 systems The results show that electricity consumption for this booster1.1 system 1.2 can reduced Figure Regarding Capital cost the for different water supply systems Figureof10 Operational cost (mostly electric consumption) for the times electricity consumption volume water consumption, the booster systems Figure Capital cost for different water supply systems perFigure 10 Operational cost (mostly electric consumption) for the C total life span of 20 years consume much 6.1 times less then the other systems (Fig 10) total life span of 20 years đ US$500,000 US$500,000 US$400,000 US$400,000 US$300,000 US$300,000 US$200,000 US$200,000 US$100,000 US$100,000 US$- US$- 2.02.0 0.00.0 Construction Construction System System System System System System 1.11.1 1.2 1.2 1.3 1.3 4.04.0 Operation Operation ste m kW/m3 kW/m3 6.06.0 Figure 11 Electricity consumption per volume water supply (kW/m3 ) C Maintenance Maintenance Sy ste m SSy ysst teem m SSyy 1.12 ssttee mm Sy 1.23 8.08.0 Initial Initial investment investment Figure 12 Life-cycle cost assessment results for case study These findings again are similar to those in previous study [3, 12] in which they found that the booster system and intermediate tank system are superior to the roof tank solution - both when it comes to initial investment, maintenance and energy efficient operation Some reasons were rendered to explain, for instance, booster configurations with several booster sets and low pressure levels can create even pressure when there is little or no flow, while break tanks made it possible to use water on stock in order to adapt to peak flow situations Thus, these two booster system and intermediate systems can provide enough water at acceptable low power consumption The system LCC assessment for 20 years (Fig 12) shows that booster system (system 1.3) has the lowest electricity consumption (46% of total LLC) but highest initial investment costs (45% of total LCC) This makes sense in a way that for the booster system, more pumps are installed This should be kept in mind that using booster system shall be vulnerable in case of pump failure and quite sensitive to electrical fall outs The intermediate system has the lowest operational cost for total life span of 20 years, but it normally requires spaces on service floor, which eventually take away potential revenue-generating space and has high risk of micro-bacterial growth in break tanks [2] Conclusions The results from experiment shows that energy consumption for booster system does not have much difference with the intermediate tank systems, this might be the results of operating conditions (the flow is adjusted with the water tap that effect the pump efficiency) This suggests that booster pump set could have better energy performance if the water consumption is more stable (smaller difference between the max/min flow) i.e large buildings The result from case study calculation shows that: Roof tank system (system 1.1) and intermediate system (system 1.2) has not much difference in the total life cycle costs Depending the number of floors and the water consumption pattern (building type), we can design a suitable system 130 Huong, N L et al / Journal of Science and Technology in Civil Engineering The result from case study for LCC assessment for 20 years shows that booster system (system 1.3) has lowest electricity consumption (46% of total LLC) but highest initial investment costs (45% of total LCC) Based on this study’s results, when optimizing the indoor water supply systems the engineers need to consider the various factors include: Energy saving, small carbon footprint, lower life cycle cost, type of buildings (number of floors, purpose of building) The author suggests utilizing a booster system for long-term economical and environmental impact Acknowledgement The authors express grateful appreciation to KURITA, KARG-AIT fund for financial support; Mr Nguyen Manh Hung and colleagues from Grundfos Company for technical support; and student research group of 59MNE, National University of Civil Engineering for their support during survey and experiment trials References [1] Chinh, P M (2011) Assessing energy saving of heat recovery ventilation equipment in ventilation and air conditioning system Journal of Science and Technology in Civil Engineering (STCE)-NUCE, 5(3): 128–133 (in Vietnamese) [2] International Energy Agency (2012) CO2 emissions from fuel combustion beyond 2020 (Online database) [3] Jens, N and Anders, N (2014) Water supply in tall buildings: Roof tanks vs pressurised systems Grundfos Water Boosting [4] Burton, F (1996) Water and wastewater industries: Characteristics and energy management opportunities No Rep CR-106941), Electric Power Research Institute, Palo Alto, CA [5] Electric Power Research Institute (2002) Water and sustainability (volume 4): U.S electricity consumption for water supply and treatment - the next half century (No Technical Rep 1006787), Palo Alto, CA [6] Wong, L T., Mui, K W., Lau, C P., and Zhou, Y (2014) Pump efficiency of water supply systems in buildings of Hong Kong Energy Procedia, 61:335–338 [7] Jim, B (2007) Domestic water system design for high-rise buildings Plumbing Systems & Design Magazine, (May/June 2007):40–45 [8] Smith, K., Liu, S., Liu, Y., Liu, Y., and Wu, Y (2017) Reducing energy use for water supply to Chinas high-rises Energy and Buildings, 135:119–127 [9] Nhue, T H., Ha, T D., Hai, D., Dung, U Q., and Tin, N V (1996) Water supply and sanitation Science and Technology Publication House (in Vietnamese) [10] Surendran, S., Tanyimboh, T T., and Tabesh, M (2005) Peaking demand factor-based reliability analysis of water distribution systems Advances in Engineering Software, 36(11-12):789–796 [11] Ministry of Construction (2006) Vietnam technical standard TCVN 33:2006: Water supply - water distribution network and water works design [12] Tin, N V (2014) Study on design code for water supply and drainage system for high scrappers in Vietnam Project report (in Vietnamese) 131 ... (BP)- Scheme Scheme Figure Water supply systems in high- rise buildings Figure Water supply systems in high- rise buildings Scheme City water supply to reservoir (R) at the basement of building, water. .. of Science and Technology in Civil Engineering Scheme Scheme Figure Water supply systems in high- rise buildings Scheme City water is provided to a reservoir at the basement of building Booster... the pump system for highrise building Materials and Method 2.1 Lab-scale experiment Two typical systems (roof tank system and booster system) [9] for water supply in high- rise buildings were