Kuala Lumpur 5th.Aug. 2009

Transcription

1 14th International Rainwater Catchment Systems Conference Y.R Chiu, C.H. Liaw, Y.L. Tsai Kuala Lumpur 5th.Aug

2 Introduction Water and Energy are both essential for human development Global rapid urbanization exhausts local water and energy resources, especially for booming hilly communities that surround many large cities and consume more energy for pumping water. Using on-site available rainwater can not only save water but also energy for urban water supply This paper present a model that integrate water- energy savings, temporal-spatial factors of rainfall, and economic analysis for evaluating, designing urban RHSs,, using case study in Taipei. 2

3 Content 1. Urban Water-Energy Dilemma 2. Challenge for RWCSs in Taiwan 3. Purpose 4. Method 5. Background and Case Study 6. Results and Discussion 3

4 1. Urban Water-Energy Dilemma Urban water supply consumes energy,especially especially for cities with limited flat area surrounded by hilly communities, e.g. Tokyo, Seoul, Taipei, Mexico City Energy consumption leads to Greenhouse gas emission and Water-Energy Dilemma, New prospect that integrates water and energy is needed in urban area 4

5 Purpose Endanger Urban Water-Energy Dilemma 5

6 國立台灣海洋大學河海工程研究所 6

7 Fuel Heat Heat Domestic Use Domestic Use Domest ic Pumpin g Domest ic Pumpin g Hilly Pumpi ng Hilly Pumpi ng Public Pumpin g Public Pumpin g Purifyin g Plant Purifyin g Plant Takin g Takin g Waste water Treat ment Waste water Treat ment Power Plant Power Plant Dam Discharge Rainfall Urban Runoff Urban Boundary Discharge CO 2 Heat Heat Heat Heat 7

8 Fuel Heat Heat Domestic Use Domestic Use Domest ic Pumpin g Domest ic Pumpin g Hilly Pumpi ng Hilly Pumpi ng Public Pumpin g Public Pumpin g Purifyin g Plant Purifyin g Plant Takin g Takin g Waste water Treat ment Waste water Treat ment Power Plant Power Plant Dam Discharge Rainfall Urban Runoff Urban Boundary Discharge CO 2 Heat Heat Heat Heat RWCS RWCS 8

9 2. Challenges for RWCS in Taiwan Taiwan Governments endeavor to promote RWCSs, also Legalize RWCSs in Green Building Index System Building Technical Guideline Effective for new building and demonstration But not for most existing building Economic Factors Low Water Price Policy Economic Effect not Well Defined Innate Constrain of RWCS Temporal and Spatial Variation of Rainfall Energy Savings and Environment Effect Are Neglected Hilly Community around Large Cities 9

10 The energy used for unit water supply in Taipei (Ceng, 2003) 10

11 11

12 國立台灣海洋大學河海工程研究所 12

13 3. Purpose In view of economic analysis,build GIS-based rainwater harvesting design system (GRHDS), incorporating temporal and spatial factors of rainfall, storage volume design, water savings,and energy savings, using Taipei Metropolis as case study Understand the Water Energy Relation in hilly communities Optimize the storage volumes Analyze the holistic effect for water and energy savings of applying RWCSs 13

14 Methodology GRHDS:System System structure Water-Energy Coefficient Water-Energy Savings Scenarios Hydraulic Simulation Optimization Method 14

15 4.1 System Structure Data Bank Rainfall Data Location of rain stations Daily rainfall record Community Data Locations Building types Number of houses Water-energy coefficient Data Processing Hydraulic Simulation Spatial Interpolation Data Input Tank size Roof area Water demand Economic Data Cost function of RWHSs Unit potable water price Unit energy price Interest rate Economic Feasibility Analysis Data Output Unit cost of savings Total water savings Total energy savings Mapping 15

16 4.2 Water-Energy Coefficient Energy consumed in purifying plant public pumping hilly pumping waste water treatment Energy for purifying plants and public pumping regarded as External While considering environmental effect total energy consumed energy should be taken into account β Hilly, i = j β Hilly, i, k = j R p, i, k Q (1/ η) p, i, k (1/ 24) β + Total, i = βpurifing + βp ump, i βhilly, i β Hilly,i : water-energy coefficient of i th community; β Hilly,i,k :coefficient of k th pumping station of i th community; R p,i,j : power of coefficient of k th pumping station of i th community ;η : mechanical efficiency(%); Q p,i,k : flow rate (m 3 /day) 16

17 4.3 Water Energy Saving Scenarios Traditionally, water savings and energy saving seldom designed together 3 Scenarios:water saving only energy saving only water and energy saving designed together Scenario 1 Scenario 2 Scenario 3 ( B ) C W, i, v = ( B ) C E, i, v = ( B ) C W + E, i, v = UWF UWSC UEF UESC UWF i, v + β i, v Hiily, i UWSC i, v UEF UWF is unit water fee;uef is unit energy fee 17

18 4.4 Hydraulic Simulation Using YBS(Yield Before Spillage) behavior model for simulation and annual water savings as indicator Y S t Q t t = t Min( Dt, S 1) = t Min ( S 1 + Q Y, V = C I t A t t ) WS = 365 n t n = 1 Y t Y is yield from tank; D is water demand;s is storage in the tank;q is roof runoff;c is runoff coefficient;v is tank volume; I is rainfall depth;ws is annual water savings 18

19 4.5 Optimization Method Maximize the Annual Water Savings within the economic feasible region in 3 different Scenarios Max. WS = f(v) s.t. B C 1 (Scenario 1, 2 and 3) 19

20 Input Location of RWCS Input Design Parameters Output of Evaluation 20

21 5. Background and Case Study Taipei Metropolis with population of 6.36 million, 81.5% of hilly area,has lunched many hilly community project science communities supported by Taipei Water Department were investigated 1. Rainfall databank 2. RWCS assumption 3. Details of the communities 21

22 5.1 Rainfall Databank Daily rainfall data of 31rainfall station( ) was used in databank Average annual rainfall is 2,981(mm/yr) with highest 6,124(mm/yr) (C0A860);and lowest 1.758(mm/yr) (C1A970) Different for 3.5 time,but distance only 17.2kM Revealing the importance of adopting spatial technology in RWCS evaluation 22

23 23

24 5.2 RWCS assumption Adopting most commonly used stainless steel tank in Taiwan Cost function modified by Liaw & Tasi(2004)(25 year life span,interest rate 3%) C v ( V ) V 2 = R 2 =0.997 Cv(V) :cost function;v :tank volume 24

25 5.3 Details of the communities Name Annua l Rainfall mm β Hilly,I,j longitude latitude β Pump,i βhill,i j=1 j=2 j=3 j=4 逸仙社區 2, o 121 o 玫瑰中國城 2, o 121 o 台北小城 2, o 121 o 萬芳社區 2, o 121 o 舊莊里 3, o 121 o 指南里 3, o 121 o 潭之鄉 3, o 121 o 木柵二期 3, o 121 o

26 6. Results and Discussion Comparing the result of evaluation with current Green Building Method Optimal volume design Contribution to urban water-energy energy savings Sensitivity Analysis on water and energy price Compared to Solar PV systems 26

27 國立台灣海洋大學河海工程研究所 Simulated Annual Water Savings (100 m 2 ; 4 person family for toilet flushing) 27

28 120 Water Savings (WS, m3/yr) Green Building Method Hydraulic Simulation Average Annual Rainfall(mm/yr) Comparing Results with Green Building Evaluation Method 28

29 6.2 Optimal Design 節水效益 ( 元 /m 3 ) 節水節電效益 ( 元 /m 3 ) 逸仙社區 玫瑰中國城 Volume for Scenario 1 (m 3 ) Volume for Scenario 2 (m 3 ) Volume for Scenario 3 (m 3 ) 台北小城 萬芳社區 舊莊里 指南里 潭之鄉 木柵二期

30 6.3 Contribution to urban water-energy energy savings Total annual water savings:307,173(m 3 /yr) Averagely very household can save 78(m 3 /yr),about 21.3% of total water use Total annual energy savings:561,438(kwh/yr) Averagely every household can save 138.6(kWh/yr), Reducing 21.3% of energy consumption in hilly pumping Averagely every household can save 88.4 Kg CO 2 emission per year 30

31 6.3 Sensitivity Analysis on water and 對總節水量 energy price 31

32 In term of total energy savings and CO2 reduction 32

33 6. Compared to Solar PV systems People are familiar with energy savings of solar PV but not RWCS The unit energy saving cost of solar PV system in Taipei Metropolis is (NT$/kWh) The unit energy saving cost of RWCSs of communities ranges from 6.4 to 30.8 (NT$/kWh), 85% households are more cost effective 33

34 7. Conclusion The important issue, i.e. water-energy energy relation, has been defined GRHDS which considering temporal and spatial factor is an useful tool for RWCS evaluation and design. Integrated design of water and energy saving can bring a new prospect GRHDS is potential to be further enhanced as a decision supporting system for urban water- energy savings to address the rapid urbanization 34

35 35