THE STUDY ON INTRODUCTION OF RENEWABLE ENERGIES IN RURAL AREAS IN MYANMAR FINAL REPORT. Volume 4 Main Report Manuals for Sustainable Small Hydros

Transcription

1 THE STUDY ON INTRODUCTION OF RENEWABLE ENERGIES IN RURAL AREAS IN MYANMAR FINAL REPORT Main Report Manuals for Sustainable Small Hydros Part 4-1 Part 4-2 Part 4-3 Part 4-4 O&M Manual-Small Hydros Design Manual-Small Hydros Design Manual-Village Hydros Institutional and Financial Aspects

2 THE STUDY ON INTRODUCTION OF RENEWABLE ENERGIES IN RURAL AREAS IN MYANMAR Final Report Manuals for Sustainable Small Hydros Part 4-2 Design Manual - Small Hydros TABLE OF CONTENTS 1 Investigation and Planning Estimate of Power Demand Measurement of Discharge and Head Measurement of Discharge and Head Available Power Discharge Surveys for Topography and Geology Layout of Power Facilities Hydropower Planning Design of Civil Structures Head Works De-silting Basin Power Canal Head Tank Regulating Pond Penstock Powerhouse Design of Generation Equipment Turbine Generator Control Unit Inlet valve...70 i

3 LIST OF TABLES Table Sample of Power Demand Estimate...4 Table Minimum Turbine Discharge...19 Table Various Types of Weir...24 Table Various Types of Intake...28 Table Hydraulic Requirements Applied to Side Intake...30 Table Facilities for a Canal...35 Table Velocities for Unlined Canals...36 Table Sand Flushing Capacity of 'Saxophone' Suction Head...46 Table 3.1 Type of Turbines and Applicable Range...55 LIST OF FIGURES Figure National Grid in Myanmar...1 Figure Power Demand Categories...1 Figure Example of Discharge Measurement...5 Figure Discharge Measurement by Current Meter...5 Figure Velocity Measurement by Current Meter...6 Figure Measurement of Sectional Area and Velocity...6 Figure Velocity and Depth...6 Figure Figure Measurement by Float...6 Discharge Measurement by Weir...7 Figure Water Level Gauge...7 Figure Example of Stage-Discharge Rating Curve...7 Figure Form of Discharge Measurement...8 ii

4 Figure Measurement of Discharge and Head...9 Figure Preliminary Planning of Layout Based an Q & H...9 Figure Figure Measurement of Head Using Carpenter s Level...9 Measurement of Head Using Pressure Gauge...9 Figure Tools for Measurement of Head...9 Figure Use of Water...10 Figure Example of Available Power Discharge...11 Figure Sample of GPS Mapping...13 Figure Test Pit...14 Figure Sample Log of Test Pit...14 Figure Relation between Length and Head...15 Figure Figure Mini/Micro Hydro Utilizing Drops or Falls...15 General Layout of Small Hydro...16 Figure General Profile of Open Waterway System...16 Figure Typical Profile of Waterway...17 Figure Figure Figure Figure Small Hydro Development Pattern Small Hydro Development Pattern Effective Head for Impulse Turbines...20 Effective Head for Reaction Turbines...20 Figure Flow Duration Curve...21 Figure Head Works...22 Figure Location of Intake...22 Figure Tyrolean Intake...23 Figure Profile of Tyrolean Intake...23 Figure Sand Flush Gate...23 Figure Figure Weir Level...25 Weir Profile...25 Figure Example of Rating Curve...25 Figure Flowchart to Estimate Inflow Discharge into Intake...26 iii

5 Figure Sample of Intake Plan...29 Figure Figure Schematic Profile of Intake Structures...29 Front Elevation of Skimmer Wall at Entrance...31 Figure Trash racks...31 Figure De-silting Basin...32 Figure Side Spillway...32 Figure Sand Drain Gate...32 Figure Overflow Discharge and Water Surface Profile in Side Spillway...33 Figure Power Canal...34 Figure Canal and Slope Failure...34 Figure Side Spillway...34 Figure Existing Footpath...35 Figure Structure without Canal...36 Figure2.3.6 Stone Masonry Canal...36 Figure Canal Design...37 Figure Side Channel Spillway...37 Figure Water Surface : Uniform Flow...37 Figure Discharge Calculation...38 Figure Type of Canal Lining...39 Figure Figure Cross Drain under Power Canal...39 Cross Drain over Power Canal...39 Figure Head Tank...40 Figure Head Tank with Spillway...40 Figure Head Tank...41 Figure Pondage Capacity...43 Figure Inflow Estimation...44 Figure 'Saxophone' Sand Flushing...45 Figure Penstock...47 Figure Water Hammer Analysis...49 iv

6 Figure Head Loss...50 Figure Head Loss of Trashrack...50 Figure Figure Head Loss of Penstock Inlet...51 Head Loss Coefficient for Reducer...51 Figure Powerhouse...53 Figure 3.1 Structure of Pelton Turbine Figure 3.2 Water Flow in Turgo Impulse Turbine Figure 3.3 Structure of Turgo Impulse Turbine Figure 3.4 Inner Shape of Turgo Impulse Turbine Figure 3.5 Installation of Turgo Impulse Turbine and Tailrace Figure 3.6 Structure of Cross Flow Turbine Figure 3.7 Water Flow in Cross Flow Turbine Figure 3.8 Characteristics of Cross Flow Turbine Figure 3.9 Runner Diameter and Width Figure 3.10 Draft Head of Cross flow Turbine Figure 3.11 Spiral-type Francis Turbine with Horizontal Shaft, Single Runner and Single Discharge Figure 3.12 Spiral-type Francis Turbine with Horizontal Shaft, Single Runner and Double Discharge Figure 3.13 Structure of Package-type Bulb Turbine Figure 3.14 Structure of S-shaped Tubular Turbine Figure 3.15 Reversible Pump Turbine Figure 3.16 Turbine Selection Diagram Figure 3.17 Concept Figure of Dummy Load Governor Figure 3.18 Excitating Circuit with AVR Figure 3.19 Structure of Butterfly Valve Figure 3.20 Structure of Through-flow Valve Figure 3.21 Structure of Sluice Valve v

7 LIST OF APENDICES (Presented in Part 6-2 of Volume 6) Appendix 1 Appendix 2 Appendix 3 Appendix 4 Nomograms Computer Programs Sample of Design Criteria Project Drawings Appendix 5 Appendix 6 Appendix 7 Appendix 8 Appendix 9 Appendix 10 Sample Specifications (included in Database) Sample of Cost Estimate for Nam Lan Hydropower Project Principal Dimensions of Turbines Principal Dimensions of Generators Unit Conversion Table of Weights and Measures Technical Terms vi

8 1 Investigation and Planning 1.1 Estimate of Power Demand (1) Need for Power Demand Survey There are many villages scattered around the rural areas of Myanmar, where by far the largest percentage of the population lives, that do not have electricity and where the electrification ratio has not reached 8%. Any further extension of the distribution lines from the national grid would be difficult, even to areas near the grid system, because of the shortage of generated power. In order to advance rural electrification under such circumstances, the development of isolated power systems would be more practical than extension of the power grid. Renewable energy such as small ~ Source: MEPE micro-scale hydropower, for which the potential is Figure abundant in the mountainous regions, would be one National Grid in Myanmar of the most effective sources for the areas, and the local technological expertise has been developing to some extent recently. It is essential to be able to estimate accurately the power demand for the target area when a small hydropower scheme is launched. Because hydropower is a site-specific energy, identification of hydro potentials to meet the required demand should be the basis for the planning of rural electrification. For the power supply in an isolated grid system, the power generated should be kept at a higher level than the load incurred, otherwise the following measures are needed: 1) Backup power by other power sources such as diesel generators 2) Adjustment of the power demand (2) Survey for Power Demand Population Demand Center Household The power demand in the rural areas in Myanmar can be classified into the following categories according to a rural society survey conducted by the JICA Study Team in June Local Industries Public Facilities Figure Power Demand Categories -1- The Study on Introduction of Renewable Energies

9 Household use : light, TV, radio, refrigerator, rice cooker, etc. Public use : streetlight, temple/pagoda, clinic/hospital, school, etc. Industrial use : local industries, etc. An investigation of the rural society needs to be carried out at the initial stage of the planning to estimate the power demand, of which the main items are summarised as follows: a) Numbers of household and population in each village tract b) Numbers, scales, and time zone of electric appliances in home use, public use, and local industry use c) Existing power facilities and existing electrification ratio d) Future development The general information required for the planning is as follows: Administration of the township that covers the demand centre Location, area, and accessibility of the demand centre Main industries Willingness to electrification Income and ability to pay for electricity Possibility for rehabilitation of the existing power facilities and extension of distribution lines Land use in the river basin, and agricultural cropping patterns Land acquisition Sectional map showing the village tracts The load curves for seasonal and time fluctuations of the power demand should be estimated taking into account the usage patterns of electrical facilities/appliances, ratio of concurrent use, etc. by reference to the existing records in neighbouring power stations. Seasonal fluctuation : Agricultural processing, drying processing in monsoon regions Time fluctuation : Lighting in night-time use, local industries in daytime use -2- The Study on Introduction of Renewable Energies

10 Where electric motors are being operated, the gross power demand (Pd) for such facilities should be within a suitable range due to the inrush current required at the starting time. P d < (Total power output Other demand) x 40 % The main electrification demands in home use are for lighting, TV, radio and refrigerator in that order of priority, and the averaged household demand was estimated at 120 W for lighting, and 160 W after introducing rice cookers, according to the rural survey by JICA Study Team conducted in June Local cottage industries may consist of the main demand during daytime and can be an important factor for determining the electricity tariff system, local development, and sustainable management of the VEC. An investigation is needed to determine the number of units, power consumption, operating conditions, and diesel consumption required to service the electricity powered machines being operated in existing local cottage industries. (3) Sample of Power Demand Estimate A sample of the power demand estimate for a village with 2,082 household in the Northern Shan State is shown below: -3- The Study on Introduction of Renewable Energies

11 Table Sample of Power Demand Estimate Customer Number Step Night Daytime of Unit Con- Sim- Unit Con-Acce Estimat- Sub-totalUnit Con-Sim- Unit Con-Acce Estimat- Sub-total Custo- sumption ulta- sumption ssibi ed Power sumption ulta- sumption ssibi ed Power mer neou lity Demand neou lity Demand Watt s % Watt % kw kw Watt s % Watt % kw kw 1.Household 2, % % % % Public 2.1 Street % Light 2.2 Temple & 11 2,000 30% ,000 40% Pagoda 2.3 Hospital % % Clinic % % H.School 1 6, ,200 20% 1, M.School 0 1, ,640 20% P.School % Sub-total Business 3.1 Restaurant 3 3,185 30% ,185 30% Guest House 2 4,905 50% 2, ,905 30% 1, Sub-total Industry 4.1 Rice Mill 18 5, ,000 80% 4, Oil Mill 6 5, ,000 80% 4, Powder Mill 0 5, ,000 80% 4, Sugarcane 0 5, ,000 80% 4, Processing 4.5 Saw Mill 2 10, ,000 80% 8, Paper Mill 0 5, ,000 80% 4, Tofu Mf'g 3 4, ,000 80% 3, Noodle Mf'g 3 7, ,000 80% 5, Furniture 5 5, ,000 80% 4, Iron Work 5 4, ,000 80% 3, BCS 2 1, ,500 80% 1, Weaving 0 5, ,000 80% 4, Water Pump % Sub-total Total ,3, ,3, Gross Total ,3,4 Including 5% of transfer loss 270 Incl. 5% transfer loss ,3,4 Including 5% of transfer loss 350 Incl. 5% transfer loss 310 Population : 12,229 Household : 2,082 Existing electrification ratio : 13.6 % Willingness to pay for initial fee : K 23,000 Willingness to pay for monthly fee: K 680/month (surveyed in June 2001) -4- The Study on Introduction of Renewable Energies

12 1.2 Measurement of Discharge and Head (1) Measurement of Discharge In the rural areas of Myanmar, the existence of either discharge records or water level gauging station information is generally expected at the rivers where a small hydropower station is planned. When a small hydropower site is identified, the discharge measurement of the river through a year is preferable. It is indispensable for the planning to carry out the following: 1) Discharge measurement more than 10 times within a proper range that enable establishment of the stage-discharge rating curve at the intake site. 2) Establishment of the water level gauge, and as many as possible readings, especially during the dry season. The task of gathering such information may be sublet to the local inhabitants. Figure Example of Discharge Measurement. The river discharges are likely to decrease significantly in the dry season in Myanmar as compared with those in the rainy season. It is, accordingly, essential to investigate discharges, especially in the dry season, for the planning of a small hydro station with an isolated grid system to supply stable energy throughout a year. The following methods are available to measure the river discharge: 3) Current Meter -5- Figure Discharge Measurement by Current Meter The Study on Introduction of Renewable Energies

13 This is the most common method to measure velocities where the stream is not irregular and turbulent. A location for the measurement should be selected in a straight stretch of the river. Simple measurements as below may be sufficient for streams where a small hydropower scheme is planned: i) 2-point method V m = 1/2 x (V V 0.8 ) for depth > 1 m ii) 1-point method V m = V 0.6 for depth < 1 m where, V m : mean velocity, V 0.6 : velocity at 60% depth from surface. Current Meter b b b b b b v1 v2 v3 v4 v5 v6 0.6 d v 0.6 d1 d2 d3 d4 d5 d6 d7 d8 d9 d10 d 11 d11 Figure Velocity Measurement by Current Meter Figure Measurement of Sectional Area and Velocity The discharge of flow can be derived using the following equation: V s Q = V A Where, Q : discharge (m 3 /s) V : A : mean velocity (m/s) cross sectional area (m 2 ) d 0.8d 0.6d 0.2d V0.2 V0.6 V0.8 4) Float Method This is the easiest method to measure velocities in a stream without any special equipment. However, the accuracy cannot be expected where the stream is irregular, wide, and shallow. The discharge of flow is given by the following formula: Q = c V A Figure Velocity and Depth vm Float Figure Measurement by Float vs -6- The Study on Introduction of Renewable Energies

14 > 2h L > 3h > 2h Where, c = 0.85 for concrete channel 0.80 for smooth stream 0.65 for shallow stream h 5) Weir Method This method requires construction of a weir across the stream to measure discharge directly in the stream. The discharge of flow is given by the following formula: Q = 1.84 ( L 0.2 h) h Where, Q : discharge (m 3 /s) L : h : length of weir (m) overflow depth (m) 1.5 h > 4h > 2h Figure Discharge Measurement by Weir 6) Stage-Discharge Method This method consists of the following procedures: (i) Discharge measurement more than 10 times within the range required to establish a stage-discharge rating curve (ii) Water level gauge reading Figure Water Level Gauge The relation between water level and discharge can be expressed by a quadratic equation. It is noted that the stage-discharge rating curve should be reviewed periodically for calibration, especially after the flood season that may result in erosion or sedimentation on the riverbed. A form for discharge measurement is shown below: WL Gauge Reading (m) Example of Stage-Discharge Rating Curve 1.50 Q = 5.15H H Discharge (m 3 /s) Figure Example of Stage-Discharge Rating Curve -7- The Study on Introduction of Renewable Energies

15 Figure Form of Discharge Measurement DISCHARGE No Distance fro rig ban lef ban Outside Depth 1s 2n Av Measure depth Velocit Velocity 1s 2n Av Velocit Avera dischar (m/s Avera depth Inside Are Widt (m) Are (m 2 ) Tota (m 2 ) Dischar (m 3 ) Observ Conditi Curre mete Note Measuremen Calcualte Cal Resu Dat Measure Recorded Weath Wind Wind Tim Water level Typ Coefficie Measure Calc' Check Discharge 3 /s) Area 2 ) Ave velocity Sta En Av Gau Recor Sta En Av V= Rod / Wire / Boat / Bridge / The Study on Introduction of Renewable Energies

16 (2) Measurement of Head The detailed planning and design are to be made based on a topographic map with a scale of 1/500 or more, but in the preliminary planning stage, much quicker and less costly methods can be used for measurement of the head. The following tools are available to measure a head for the preliminary planning. Discharge Q (m 3 /s) Head Tank Penstock Power canal Powerhouse Intake Head H (m) Head (m) Discharge (m 3 /s) Tailrace Power (kw) = 9.8 Q H η Efficiency η = 0.5~0.7 Figure Measurement of Discharge and Head Figure Preliminary Planning of Layout Based on Q & H Y hn Y Plastic Tube filled with water Hg Xn Hg Presure Gauge Measurement of Head Using Carpenter's Level X2 X1 h X Level h Measurement of Head Using Pressure Gauge X Figure Measurement of Head Using Carpenter s Level Figure Measurement of Head Using Pressure Gauge GPS to measure coordinates & altitude Source: (Figure ~1.2.15) JICA Study Team Distance Meter Clinometer Portable Compass Figure Tools for Measurement of Head -9- The Study on Introduction of Renewable Energies

17 1.3 Available Power Discharge If paddy fields with single-cropping are developed in a river basin whose water is utilised for power generation, the irrigation water supply usually starts in May when the river discharge is at the minimum level in the end of the dry season. Therefore, the available discharge in May is likely to become the lowest under such circumstances. The first priority for water utilisation is generally given to the irrigation supply in rural areas in Myanmar. It is therefore required to investigate not only the river discharge, but also the existing water utilisation, irrigation system, and rainfall patterns to estimate the available power discharge. The following items need to be surveyed at the planning stage: Land utilisation in the areas affected by a hydropower station Irrigation area, the cropping patterns, and the irrigation supply discharge Future development plan for irrigation Basic stance of local inhabitants for the water utilisation When the water use produces a conflict between irrigation and power generation demands, the following needs to be considered: 1) The location of the power generation facilities should be carefully selected to minimise the conflict between irrigation water use and power discharge in the area where the river flow is utilised for the irrigation in the river stretch between the intake and the tailrace. Powerhouse Irrigation Canal Intake Irrigated Area 2) The river discharge and the irrigation demand in the areas affected by the hydropower plant should Figure Use of Water be investigated throughout one year to estimate the available power discharge, taking into account the existing irrigation practices. 3) Irrigation water for paddy fields is approximately 1.0 m 3 /s for 1,000 ha in general. Areas, cropping patterns, irrigation canal systems, return flow into the river, rainfall and supplemental discharge from the river are major factors to estimate the irrigation demand The Study on Introduction of Renewable Energies

18 Q (m 3 /s) Discharge at Hosang Chaung in Irrigation Requirement Available discharge for power generation River Discharge Source: Measurement and Assumption of JICA Study Team Figure Example of Available Power Discharge -11- The Study on Introduction of Renewable Energies

19 1.4 Surveys for Topography and Geology (1) Topography An Inch-mile map (1:63,360) is suitable to identify a hydropower scheme site for the initial planning and to determine accessibility from the demand centre. The use of a portable GPS may be a powerful tool to position easily and accurately the specific points in and around the project area at the initial planning stage. A sample mapping by GPS is shown figure in the next page. It is essential for the detailed design and construction to map the topography of the anticipated construction areas that will cover the open civil structures such as intake, de-silting basin, head tank, and powerhouse at a 1:500 scale or larger, based on a topographic survey. As for power canals, the profile and cross sectional surveys may be enough for the design, but further mapping of the areas around the related structures such as cross drains, side spillways, siphons, etc. will be required The Study on Introduction of Renewable Energies

20 Source: Field Study of JICA Study Team Figure Sample of GPS Mapping -13- The Study on Introduction of Renewable Energies

21 (2) Geology Test pitting is enough to confirm the foundation geology of the key structures for small hydropower schemes. A practical pit size is 1.8 m long x 1.2 m wide x 5.0 m deep. It can be manually dug with scoops and picks, using a rope and bucket to lift up the excavated soil without the use of any further heavy lifting equipment. A pit log should be prepared for every test pit, as a report of the test pitting, and should contain the pit number, its location, boundaries and depths, description of soil, groundwater table and bedrock surface, if any, and all other relevant information. Figure Test Pit Figure Sample Log of Test Pit -14- The Study on Introduction of Renewable Energies

22 1.5 Layout of Power Facilities Selection of Site Attention should be paid to the following points to identify the potential for a small hydropower scheme with an isolated grid system: 1) Discharges are stable even in the dry season. 2) Specific discharge (m 3 /sec / 100 km 2 ) is big. 3) (L/H) rate is small Main stream Tributary L / H < 40 L / H < 20 L / H < 15 where Potential Site-1 L1 H1 General outline Advantageous sheme Excellent scheme L : length of waterway H : head Potential Site-2 Figure Relation between Length and Head L2 H2 4) Distance from demand centre is short. Basic Layout The main components of the civil facilities are weir, intake, de-silting basin, power canal, head tank, pondage, penstock, powerhouse, and tailrace. It is rare for dam type power generation or tunnel waterway types to be adopted in a small hydropower facility. However, existing irrigation dams may be utilised for small/mini hydropower in a re-development plan. The existing irrigation canals with drops Figure Mini/Micro Hydro Utilizing Drops or Falls may be utilised for mini/micro hydropower. Penstock pipes can be connected to the intake or the de-silting basin without provision of a power canal. In such a case, since all or part of the irrigation water is to be used for power generation, the discharge fluctuation during irrigation and non-irrigation periods needs to be confirmed. Depending on the nature of the work and the design conditions involved, the combination of facilities may be varied. As have been experienced in many small hydropower plants constructed, the major issues relating to the civil components are i) sedimentation, and ii) hydraulic characteristics during floods. Therefore, suitable combinations and layouts responding to the specific site conditions need to be -15- The Study on Introduction of Renewable Energies

23 properly reflected in the design. A typical layout and profile of a small hydropower station is shown below together with technical notes: Nearby demand center Head Tank Penstock Cross drain at valley Power Canal Powerhouse Slope protection or box culver De-silting Basin Intake De-silting basin to be located next to intake Low velocity to regulate excessive flow & sand Steep slope enough to wash out sediment to river Intake to be located in a straight river stretch Side intake with weir or Tyrolean intake Sand flushing gate to be provided beside the weir Figure General Layout of Small Hydro Weir Intake De-silting Basin Power Canal Head Tank Spillway Trashracks Intake Gate Side Spillway De-silting basin velocity < 0.3 m/s slope steeper than 1/30 Trashracks Spillway River Outlet / Sand Flush Gate Figure Sand Drain Gate Power canal slope 1/500 ~ 1/2,000 General Profile of Open Waterway System Sand Drain Gate -16- The Study on Introduction of Renewable Energies

24 Head Tank Trashracks Spillway Sand Drain Gate Penstock Head Tank to be located on stable ridge capacity against load change spillway & sand drain Powerhouse Tailrace Penstock to avoid potential land slide area to be located on stable ridge to be located below hydraulic grade line slope protection & drain along penstock penstock directly from de-silting basin may be possible according to topography Anchor Block Powerhouse to be built on firm foundation to be located above FWL drainage around TWL Figure Typical Profile of Waterway -17- The Study on Introduction of Renewable Energies

25 1.6 Hydropower Planning (1) Design Discharge For a small hydropower station with an isolated grid system, the power generated should be above the load demanded when a backup power system cannot be provided. The main points for planning of such a small hydro plant are summarised as follows: 1) determination of the minimum power discharge based on the available minimum discharge for power generation ( 90 ~ 95% dependable discharge is a general target) 2) determination of the maximum power discharge depending on the peak load demand and the available discharge during the rainy season. Output (kw) Potential (Q min ) > Demand Discharge Q (m 3 /s) Firm Power Output Irrigation Spill out Non - Operation Period Demand Q min Min. Discharge Figure Small Hydro Development Pattern The Study on Introduction of Renewable Energies

26 Output (kw) Potential (Q min ) < Demand 24 hours Supply with Min. Power Max. Power Output or for 24-hour Peak Power Operation Max. Power Output Discharge Q (m 3 /s) Spill out Min. Power Output Demand Irrigation Peak power operation or Demand Control Q max Non - Operation Period Q min Figure Small Hydro Development Pattern-2 Min. Discharge Ratios of (minimum turbine discharge)/(maximum turbine discharge) and (minimum efficiency)/(maximum efficiency) are given for typical turbines below: Table Minimum Turbine Discharge Type (Q min / Q max ) (η min / η max ) Francis with horizontal shaft 30 ~ 40% 0.70 Pelton with horizontal shaft 15% nozzle Pelton with horizontal shaft 30% nozzle Cross flow 15% 0.75 guidevane divided Cross flow 40% 0.75 guidevane not divided Turgo impulse 10% nozzle Turgo impulse 20% nozzle Reversed Pump 100% Source: Estimation by JICA Study Team The numbers of turbines for a small hydropower plant are preferably 1 unit, or 2 units to cover the wide range of discharge fluctuation. When turbines without discharge control such as Reverse Type are adopted, several units may be installed to respond to available discharges in the rainy and dry seasons. The number of units required is closely related to the selection of turbine type as explained later. 2 Effective Head Effective head can be calculated by deducting the head losses from the gross head between the intake and the tailrace. However, the effective head for impulse turbines -19- The Study on Introduction of Renewable Energies

27 (Pelton, Turgo Impulse, Cross Flow) and that for reaction type turbines (Francis, Propeller, Tubular) are calculated differently as shown below: FSWL v1 2 /2 h1 Intake H e = H g h v1 Head Tank Penstock 1 h2 h3 Hg : gross head (m) He : effective head (m) h1 : head loss between Intake & head tank h2 : head loss between head tank & tailrace h3 : head between mean pitch level and TWL h2 He Hg Tailrace h3 Powerhouse TWL Figure Effective Head for Impulse Turbines FSWL v1 2 /2 h1 Intake H e = H g h h 1 v1 Head Tank Penstock 2 2 v2 h 2g 3 Hg : gross head (m) He : effective head (m) h1 : head loss between Intake & head tank h2 : head loss between head tank & tailrace h3 : head between draft tube WL and TWL h2 He Hg Tailrace Powerhouse v2 v2 2 /2 TWL h3 Figure Effective Head for Reaction Turbines Detailed calculation method for head losses are shown in Chapter 2.6 and Appendix 2-3 of Part 6-2 in Volume The Study on Introduction of Renewable Energies

28 3 Power Output and Annual Energy Power output is given by the following formula: P = 9.8 η Q H where, P η Q H :Power output (kw) :combined efficiency for turbine and generator :power discharge (m 3 /s) :effective head (m) Figure Flow Duration Curve If a run-of-river scheme requires a flow of more than the minimum river discharge, a flow duration curve is useful to estimate the approximate annual energy as follows: For maximum discharge Q 1 : ( area( A' BCDF') PlantFacto r ξ ) = 1 area( A' BGI ') Annual Energy E 1 = ξ 1 P 8,760 Where, E 1 : Annual energy (kwh) P : Max. power output (kw) For maximum discharge Q 2 : area( ABCDF ) PlantFacto r( ξ 2 ) = area( ABGI ) Annual Energy E 2 = ξ 2 P 8,760 When a bigger discharge (Q 1 ) is selected, a larger scale of power facility with a lower plant factor is required, while a smaller discharge (Q 2 ) gives a smaller plant facility with a higher plant factor. The optimum maximum design discharge to be finally selected should take into account the revenue generated and the cost incurred in principle, bearing in mind that the power tariff needs to be properly established The Study on Introduction of Renewable Energies

29 2 Design of Civil Structures 2.1 Head Works Weir Intake De-silting Basin Power Canal Head Tank Spillway Trashracks Intake Gate Side Spillway Trashracks Spillway Sand Flush Gate Sand Drain Gate Figure Head Works Sand Drain Gate Site Selection This section deals with run-of-river schemes that do not require dam construction, but employ a diversion structure or weir across the river. One of the most common problems affecting a small/mini/micro hydropower scheme is the Intake (A) damage to the intake caused by floods, and another is sedimentation deposited upstream of the intake or flowing into the waterway. The following points River Intake (C) are to be considered in locating the intake structures: Sandbar 1) Intake (A): The best location for an intake is to locate it along a relatively straight stretch of the stream 2) Intake (B): Susceptible to severe damage from floods, debris, and erosion Intake (B) Figure Location of Intake 3) Intake (C): Sediments tend to accumulate in front of the intake and can enter and/or block the intake -22- The Study on Introduction of Renewable Energies

30 Countermeasures against Sedimentation The Tyrolean intake is applicable to mini/micro hydropower stations located on steep rivers containing boulders and pebbles. The characteristics of Tyrolean type intake are as follows: 1) Intake facilities can be minimised. 2) Relatively large amounts of sediment will enter the intake especially during a flood, so a sand drain facility with enough hydraulic gradient and capacity to drain out the sediment is indispensable. Periodical sand draining operations are required. Figure Tyrolean Intake 3) Cleaning work for driftwood or leaves trapped on the screen is necessary. 4) An intake discharge of 0.1 ~ 0.3 m 3 /s/m 2, a screen slope gentler than 30 and a screen bar interval of 20 ~ 30 mm is generally practised. A sand flush gate should be located to one side of the weir to release sediments deposited upstream of the weir. The intake is located at a side of the river just upstream of the weir and to minimise sand volume entering the intake. The sill level of a sand flush gate is generally set at 0.5 ~ 1.0 m higher than the original riverbed level and 1.0 ~ 1.5 m lower than the intake floor level. The skimmer wall at the entrance of the inlet may be effective to prevent driftwood or an excessive flood flow from entering the intake. If slope failures or sediment yield are confirmed in the upstream basin, Flow Intake Figure Profile of Tyrolean Intake Weir Intake Flood Water Level Weir Skimmar Wall Weir Crest 1.0 ~ 1.5 m Sand Flush Gate EL.2 De-silting EL.3 Intake Sand Sand Flush Flush Gate Gate Trashracks Figure Sand Flush Gate Int Ga -23- The Study on Introduction of Renewable Energies

31 protection work such as a gabion wall may be effective to control the sediment outflow. Flow velocity at the intake should be limited to 0.5 ~ 1.0 m/s to avoid sediment flowing into the waterway. Weir Types of weir are summarised as follows: Table Various Types of Weir Type of Weir Specific Features Typical Figure Concrete Applicable on rock gravity foundations Most commonly used Durable and impervious Relatively high cost Floating concrete weir Applicable on gravel foundations Need an enough seepage path Durable Relatively high cost Gabion covered with concrete Applicable on gravel foundation Surface protection by concrete Relatively low cost Gabion Applicable on gravel foundation Flexible Low cost and easy maintenance Stone masonry Applicable on gravel foundation Low cost and easy maintenance -24- The Study on Introduction of Renewable Energies

32 It should be noted that type of weir to be applied should be determined according to the power scale, importance, flood discharge, foundation condition, and maintenance requirements. The use of high quality materials and construction techniques will result in less maintenance and repair work over the life of the scheme. The weir crest level of is normally designed equal to the Full Supply Water Level (FSWL) under the maximum design B discharge. The hydraulic design of weir and intake should be made appropriately to take the proper discharge into the waterway. Since the flow taken from a river is not regulated in a run-of-river scheme, any excessive water above the maximum design discharge should be released safely from spillways. When a weir crest is set equal to the FSWL at the maximum design discharge, the inflow into the intake can be divided into the following cases: 1) (River flow) < (Maximum design discharge) Whole flow enters the intake. The water level varies between FSWL (EL.1) and the intake floor level (EL.2) The maximum design discharge flows into the intake at FSWL. The minimum flow to the downstream basin shall be released from the river outlet at any conditions if need be. 2) (River flow) > (Maximum design discharge) A water level is above FSWL (EL.1), when a part discharge is spilt over the weir and the remainder, that exceeds the maximum design discharge, enters the waterway. Any excessive discharge taken from the intake should be released from a side spillway, which needs to be provided at a suitable location of the waterway. WL. (m) EL. 1 FWL Spillway Sand Flush Gate EL.3 WL - Discharge Curve for Spillway Discharge & Inflow into Intake Inflow into Intake Weir Flow over Spillway Discharge (m 3 /s) Figure Example of Rating Curve H FSWL EL. 2 Figure Weir Level Intake H Intake EL. 4 FWL Spillway EL.1 Weir Profile EL. 3 Figure Weir Profile -25- The Study on Introduction of Renewable Energies

33 The intake gate should be closed during a flood to avoid excessive sediment inflow into the waterway. If a river water level is known from readings of a water level gauge provided at the forebay, a discharge entering the waterway can be estimated by the following sequences. Then, a rating curve (WL-Q) at the forebay can be prepared. Sequence to Estimate Inflow Discharge into Intake WLforebay is known Yes WL > FSWL No Overflow Discharge from Weir Qweir = C B (WL - FSWL) 1.5 Whole flow enters the Intake Assume Discharge Qintake Non-uniform flow analysis from Head Tank to Intake Calculation for Overflow Discharge from Side Spillway Yes WL > Spillway Crest No No Overflow from Side Spillway WLintake = WLforebay No Yes Assumption Qintake is correct Figure Flowchart to Estimate Inflow Discharge into Intake Overflow discharge from spillway and outflow discharge through sand flush gate can be calculated by the following formulas: Discharge from a weir spillway Q spill = 1.84 B H 1.5 Discharge from a sand flush gate where, Q spill : discharge from spillway (m 3 /s) B : width of spillway (m) H = WL - Crest Level (m) 1) For orifice flow Q : discharge through the gate (m 3 /s) Q = 0.6 A 2 g H A : Flow area (m 2 ) H = WL Centre level of orifice (m) -26- The Study on Introduction of Renewable Energies

34 2) For pipe flow Q = A 2 g H 1 + f f e + f e : loss coefficient for entrance (0.1 ~ 0.5) f : loss coefficient for friction = 124.5n 2 L/D (4/3) In order to carry out the peak power generation in the dry season without providing a regulating pond, a river channel storage may be effective if gates are provided on the weir. The gates should be open in the rainy season and be closed in the dry season if floods are not anticipated. Intake Types of intake are summaried as follows: -27- The Study on Introduction of Renewable Energies

35 Type of Intake Side Intake with Weir Table Various Types of Intake Specific Features Most commonly used for run-of-river type power schemes Sand flush gate is located aside the weir to release sediments deposited upstream of the weir. Typical Figure Sand Flush Gate Weir Intake Intake is located at a side of the river just upstream of the weir/sand flush gate. Intake gate is provided at upstream section of de-silting basin to close during sand drain operation or maintenance of the waterway. Weir Flow Intake Intake Gate Sand Flush Gate Side Spillway De-silting Basin Waterway Tyrolean Type Intake Suitable for steep rivers containing boulders Weir is not necessary Necessary to remove drift woods or leaves on the screen Necessary to remove fine sands entered the intake Intake to Utilise Pondage Applied to natural/artificial ponds to utilise the water for power generation The site selected for the headworks should be stable and suitable for reliable foundations. All excess water and debris taken from the river needs to be minimised in the design of headworks, and those entering during a flood flow need to return to the river before entering the canal or penstock The Study on Introduction of Renewable Energies

36 Hydraulic requirements generally applied to side intake with concrete weir are summarised as follows: Weir Flow Sand FlushGate Side Spillway Sand Drain Gate Intake Intake Gate De-silting Basin Power Canal Sample of Intake Plan, arranged from DHP drawing. Figure Sample of Intake Plan Skimmer Wall Flood Water Level Weir Crest Weir EL.2 Sand Flush Gate Trashracks EL.3 Intake Intake Gate 1 : n 1 Side Spillway EL.5 EL.7 1 : n 2 EL.6 De-silting Basin Sand Drain Gate Power Canal Schematic Profile of Intake Structures Figure Schematic Profile of Intake Structures -29- The Study on Introduction of Renewable Energies

37 Table Hydraulic Requirements Applied to Side Intake Item General Application Symbol Crest Level of Intake Weir = Full Supply Water Level EL. 1 Sill Level of Sand Flush = Original River Bed + (0.5m ~ 1.0m) EL. 2 Gate Floor Level of Intake = EL.2 + (1.0m ~ 1.5m) EL. 3 Velocity at Intake 0.5 ~ 1.0 m/sec approximately Top of Intake Deck = Flood Water Level + freeboard ( > 1.0m) EL. 4 Top of Intake Gate = FSWL Velocity at Intake Gate 1.0 ~1.5 m/sec approximately Crest of Side Spillway = FSWL - (0 ~ 10 cm) EL. 5 Slope of De-silting Basin 1:10 ~ 1:30 Velocity in De-silting Basin < 0.3 m/sec Length of De-silting Basin (2 ~ 3) x depth x velocity / sedimentation rate = (2 ~ 3) x depth x 0.3 / 0.1 = (6 ~ 9) x depth EL. of Sand Drain (Sand drain outlet level) > (Water level of the river) EL. 5 Floor Level of Power Canal = EL. 3 EL. 7 Slope of Power Canal 1:1,000 ~ 1:2,000 Velocity in Power Canal < 2 m/s maximum for lined canal -30- The Study on Introduction of Renewable Energies

38 A skimmer wall at the entrance of the intake will be effective not only to avoid driftwood entering or debris floating into the intake, but also to restrict an excessive inflow by making an orifice flow when the river water level is higher than the Full Supply Water Level (FSWL) during a flood. An intake gate is provided at the upstream section of the de-silting basin that can be closed during the sand drain operation or maintenance of the waterway. The gate is to be closed during floods to avoid excessive sediment inflow. The velocity through the intake gate opening should be limited to about 1.0 m/s. Trashracks are provided at the entrance of the intake to prevent trash, leaves, and floating debris from entering the waterway. The screen bars are generally arranged with 5 ~ 9 mm thick, 50 ~ 120 mm bar wide, 100 ~ 150 mm intervals, and 60 ~ 70ºangle to the horizontal. FWL Skimmer Wall FSWL v = 0.5 ~ 1.0 m/s Figure Front Elevation of Skimmer Wall at Entrance b t b Flow w θ Thickness t = 5 ~ 9 mm Width w = 50 ~ 120 mm Interval b = 100 ~ 150 mm Inclination θ = 60 ~ 70º Figure Trashracks -31- The Study on Introduction of Renewable Energies

39 2.2 De-silting Basin The de-silting basin is designed to settle sands bigger than 0.5 ~ 1.0 mm diameter of which the settling velocity corresponds to 0.1 m/s. Average flow velocity in a de-silting basin is generally 0.3 m/s, and the channel slope is 1/10 ~ 1/30. The length of de-silting basin is given by the following empirical formula: L = (2 ~ 3) v u h s Trashracks Intake Gate Slope 1 : 10 ~ 1 : 30 1 : 10 ~ 1 : 30 Side Spillway L L s Side Spillway v < 0.3m/s Figure De-silting Basin u h where, L : length of de-silting basin (m) h s : depth of de-silting basin (m) v : average velocity in de-silting basin (m/s) = Q / (B x h s ) = 0.3 m/s u : settling velocity for target sand particle (m/s) = 0.1 m/s for sand grains of 0.5 ~ 1.0 mm Side Spillway Sand Drain Sand Drain Gate Figure Side Spillway Figure Sand Drain Gate A side spillway should be provided at the de-silting basin to release an excessive inflow during a flood. The length required to overflow the excessive discharge and the water surface profile can be computed by the following De-Marchi s equations: -32- The Study on Introduction of Renewable Energies

40 L B Flow h 0 h 1 h w 3 / 2 q = 1.84 ( h w) 2g B h1 h0 L = { φ( ) φ( )} 1.84 H H 2H 3w H φ = ( H w h h ) w 1 / 2 3 tan 1 x H ( h 0 h ) w Figure Overflow Discharge and Water Surface Profile in Side Spillway It is noted that the outflow path needs to be protected against scouring. 1 / 2 Where q : unit overflow discharge (m 3 /s/m) h : depth of flow (m) B : width of channel w : height of weir (m) h 0 : depth at downstream section (m) h 1 : depth at upstream section (m) H = h + Q 2 /{2g (B h ) 2 } (m) Overflow Discharge & Water Surface Profile in Side Spillway -33- The Study on Introduction of Renewable Energies

41 2.3 Power Canal Weir Intake De-silting Basin B Trashrack Intake Spillway Side Spillway FSWL Power Canal Head Tank Trashracks Spillway Sand Flush Gate Sand Drain Sand Drain Figure Power Canal Route Selection This section deals with open canals only, which are most commonly applied to small/mini/micro hydropower schemes, especially in Myanmar. A route for the power canal needs to be selected after consideration of the topographic features along the canal for the following points: 1) Stability against slope above and/or below the canal 2) Specific conditions such as streams, roads, and the existing structures to be crossed Selection of the canal route and the design of canals should be made in consideration of the fact that the water level in a canal may rise for any of several possible reasons: Sliding of slope by overflow Debris Sliding may be induced by overflow from a canal in which debris enters the canal. Figure Canal and Slope Failure 1) When the canal flow is obstructed by a landslide or closure of a gate at the downstream facilities 2) When excessive water enters the intake during a flood. 3) When excessive running water is drained into the canal during heavy rain Side spillway to overflow excessive inflow Figure Side Spillway The Study on Introduction of Renewable Energies

42 The following facilities for a canal may need to be designed for the above conditions: Table Facilities for a Canal Potential Landslide (a) Box culvert or canal cover (concrete/wood) (b) Slope protection by structural reinforcement of the slope, excavation in a gentler slope, and vegetation such as sodding or planting Crossing of stream (a) Aqueduct to by-pass the flows from a flood or debris flow or valley (b) Siphon to path under the stream (c) Drainage facilities to collect the running water in the catchment basin and to release it safely to protect the canal from being Crossing of roads or existing structures Excessive inflow attacked or eroded by the drained flow or debris (a) Box culvert or bridge to connect the existing road. (b) Steel pipe or concrete conduit embedded under the existing structures. (a) Side spillway to overflow the excessive flow over the max. design discharge. An appropriate protection work against scouring by the overflow is indispensable (b) Drainage facilities to avoid excessive inflow into the canal When selecting the canal route, the existing structures such as foot pass and irrigation channel can be utilised to minimise the construction cost of the canal as well as ease of access. Depending on the topographic conditions, it may be possible to omit the power canal and the penstock may be connected directly to the de-silting basin or the head tank. Existing footpath or irrigation canal may be utilized for power canal Figure Existing Footpath -35- The Study on Introduction of Renewable Energies

43 Canal Dimensions Power canals are to be designed in consideration of 1) flow capacity, 2) velocity, 3) roughness, 4) slope, 5) sectional shape, 6) lining (with or without, material), and 5) maintenance. The velocity in a canal should be low enough to prevent erosion of the canal, especially if it is unlined, and to keep effective head as high as possible. The velocity in a canal should be high enough to prevent sedimentation and to avoid the growth of aquatic plants especially in unlined earth canals. Omission of canal, and utilization of existing structures Figure Structure without Canal V min = 0.3 m/s for sedimentation for flow carrying silty water V min = 0.3 ~ 0.5 m/s for sedimentation for flow carrying fine sand V min = 0.7 m/s to prevent aquatic plants Maximum permissible velocities for unlined canals to avoid erosion are given as follows: Table Velocities for Unlined Canals Material n V max (m/s) Permeability (x 10-6 m 3 /s/m 2 ) Fine sand > 8.3 Sandy loam Clayey loam Clay For a lined canal, wear of abrasion sets the upper limit on velocity. Velocities above 10 m/s will not damage a concrete lined canal when the water is clear, but velocities above 4 m/s containing sand and gravel may scour the lining. The steeper the slope of the canal, the smaller the sectional area required; however the effective head is decreased. The best combination of a canal size and a slope should be examined within a suitable range of flow velocity. The maximum velocity in a lined canal is normally smaller than 2.0 m/s. Stone-masonry canal with screen Figure2.3.6 Stone Masonry Canal -36- The Study on Introduction of Renewable Energies

44 A canal slope, depending on the topographic conditions, is generally as follows: 1/500 ~ 1/1,000 : to minimise the canal size in high head plant 1/1,000 ~ 1/1,500 : general application 1/1,500 ~ 1/2,000 : to minimise a head drawdown in low head plant Roughness coefficient n is an empirical measure of surface roughness of a waterway. The following values are usually applied : Steel : ~ Concrete : Stone-masonry : ~ For unlined canals, a trapezoid cross-section is the most common. Side slopes of a canal are 1.0 (V):0.5 (H) for rock foundation, and 1.0(V):2.0(H) for sandy loam foundation. For lined canals, a rectangular or a trapezoid cross-section is commonly used for stone masonry lining, and a rectangular section for concrete lining. Properly designed lined canal reduces the canal size and the excavation volume to convey the same discharge Figure Canal Design B A side channel spillway is generally provided at the de-silting basin and the head tank; however, it may be necessary to be designed in a suitable section of the power canal depending on the design conditions. The outflow path needs to be protected against scouring. Figure Side Channel Spillway Power Canal Head Tank Water Surface Profile Uniform depth for design discharge The canal floor elevation at the downstream end (EL.4 in the figure) is commonly fixed to provide a uniform flow depth for the maximum design discharge when the water level in the head tank or the regulating pond is at the Full Supply Water Figure Water Surface : Uniform Flow Level (FSWL). In this condition, the flow depth in the canal is uniform over the whole stretch if the canal slope is uniform. EL. 4 FSWL Uniform flow state at the downstream end of the canal at FSWL -37- The Study on Introduction of Renewable Energies

45 A non-uniform flow analysis should be carried out in the full section of the waterway starting from the head tank or the regulating pond up to the intake, varying parameters such as discharge, roughness coefficient, and the initial water level at the head tank. The wall height of the canal is to be designed so that the energy line for the maximum inflow into the canal should be lower than the wall crest. Q = A n 2 3 R I 1 2 For a rectangular section A = b h For a triangular section A = h( b + mh) Q = V A R = R = h h b + 2h b h( b + mh ) 1 + m where, Q : discharge (m 3 /s), n : roughness coefficient, b : width of canal (m) h : depth of flow (m), R : hydraulic radius (m), I : slope of canal Figure Discharge Calculation 2 Uniform flow depth in a canal can be calculated by Manning s Formula: Uniform flow analyses can be made by the computer programs attached in Appendix α Q A b n Q 2 i + ( ) dh ga b x R A = 2 dx α Q α A 1 3 ga h Non-uniform flow analysis involves solving the following differential equation: Non-uniform flow analysis can be made by the computer programs attached in Appendix 2-2. m 1 b b h h Lining Types The lining type of earth canal has the following characteristics: (a) easy for construction and maintenance, (b) low cost, (c) not applicable to pervious and erosive foundation, (c) velocity < 0.3 m/s, (d) roughness coefficient n = on an average, seepage loss = 1.0 (clay) ~ 8.0 (sand) x 10-6 m 3 /s/m 2 The lining type of stone masonry canal has the following characteristics:(a) easy for construction and maintenance, (b) velocity <1.5 m/s (dry stone masonry) and velocity <2.0 m/s (wet stone masonry), (c) roughness coefficient n = (dry stone masonry) and roughness coefficient n = (wet stone masonry) -38- The Study on Introduction of Renewable Energies

46 The lining type of concrete lining canal has the following characteristics: (a) durable, (b) relatively high cost, (c) velocity < 3.0 m/s, (d) roughness coefficient n = on an average. Earth Canal Stone Masonry Canal Figure Type of Canal Lining Concrete Canal Cross Drain If a power canal passes through valleys with catchment areas, drain facilities that cross under or over the power canal should be provided to protect the canal structure from attack from running water with containing debris during rainfall. Box culverts, concrete pipes, polyethylene pipes, etc. are used as under drains, and open chutes as over drains. Under drains need adequate flow area, since they are likely to be clogged with debris, soil, etc. A minimum inner space of 60 cm is preferable for manual cleaning. Power Canal Flow & Debris Figure Cross Drain under Power Canal Power Canal Figure Cross Drain over Power Canal Slope steeper than 1/50 Size bigger than φ 60cm Enough flow area not to be clogged Maintenance for clogging -39- The Study on Introduction of Renewable Energies

47 2.4 Head Tank Weir Intake De-silting Basin B Trashrack Intake Spillway Side Spillway FSWL Power Canal Head Tank Trashracks Spillway Sand Flush Gate Sand Drain Sand Drain Site Selection Figure Head Tank A head tank is provided between a power canal and a penstock pipe to adjust a turbine discharge corresponding to the load fluctuation, while a surge tank is required when a pressure tunnel or conduit is applied as headrace. When a penstock pipe is connected directly to a de-silting basin, a de-silting basin may be designed to have functions of a head tank. Figure Head Tank with Spillway The location of a head tank is selected generally to be on a ridge with firm foundations, depending on the topographical and geological conditions. A spillway and a sand drain gate should be considered and incorporated into the head tank. When a spillway is provided (it may be omitted under some conditions), the route of the spillway should be properly designed so as to not cause sliding or erosion of the slope. Hydraulic Design The capacity of the head tank is determined according to the responsive characteristics of the governors installed in the power plant. 1) Mechanical governors and manual operation V > (Q max ) x (120 ~ 180) Where, V : capacity of tank (m 3 ) A : surface area of tank (m 2 ) Q max : max.design discharge (m 3 /s) -40- The Study on Introduction of Renewable Energies

48 2) Electric governor, computer governor and dummy load governor V > (Q max ) x 20 sec +A x 0.8 Spillway discharge can be calculated as follows: Q = 1.84 Bs H 1.5 Where, Q : spill-out discharge (m 3 /s) Bs : length of spillway (m) H : overflow depth (m) A discharge capacity of sand drain gate is calculated by the following formulas: 1) For orifice flow Q = 0.6 A 2 g H Where, Q : discharge through the gate (m 3 /s) A : Flow area (m 2 ) H = WL Centre level of orifice (m) 2) For pipe flow Q = A 2 g H 1+ f + f e b + f f e : loss coefficient for entrance (0.1 ~ 0.5) f b : loss coefficient for bend ={ (D/R) 3.5 } (θ/90) 0.5 D : pipe diameter (m) R : radius of curvature (m) θ : bend angle (º) f : loss coefficient for friction = 124.5n 2 L/D (4/3) L : length of pipe Power Canal Head Tank Air Vent Pipe Uniform flow depth at Q design Bs Penstock Gate Trashracks h FSWL Spillway MOL φ Sand Drain Gate 30 ~ 50 cm Figure Head Tank Water depth between the Minimum Operational Level (MOL) and the centre level of the penstock inlet is given by the following: -41- The Study on Introduction of Renewable Energies

49 h > φ (φ < 1.0 m) h > φ 2 (φ > 1.0 m) Where, h : depth between MOL and pipe centre (m) φ : diameter of penstock pipe (m) An air vent pipe is required when the inlet gate is provided on the inlet of the penstock. The diameter of the air vent pipe is given by the following empirical formula: Where, φ : diameter of air vent pipe (m) 2 P L φ = ( ) P : power output (kw) H L : length of air vent pipe (m) H : head of penstock (m) The sectional shapes of head tank should be designed to avoid any abrupt changes that can cause the occurrence of a vortex. An average slope of head tank is 1/15 ~ 1/50 in order to drain the sediment deposited in the tank through a sand drain gate. Omission of Spillway The spillway of the head tank can be omitted when the discharge is regulated in the intake and the following conditions are applied: 1) Deflectors are attached for Pelton or Turgo Impulse type turbines. 2) An outlet valve, branched from the penstock pipe, is provided to release the discharge during load rejection. The valve opening is connected with the closure of the guide vane. 3) A dummy load governor, which is applied to mini/micro hydropower schemes smaller than 300 kw, is provided to respond to load rejection The Study on Introduction of Renewable Energies

50 2.5 Regulating Pond A regulating pond is provided for daily peak power generation, of which the location is selected at a flat area to accommodate the required pond capacity, which needs to be enough to meet a power demand, especially during a dry season. Q (m 3 /s) River Discharge Irrigation water Required pond capacity Max. turbine discharge without pondage Available power Discharge Max. turbine discharge with pondage The pondage capacity should be determined to allow supply, Figure Pondage Capacity with a supplementary discharge during a target operation period of time when the available discharge is insufficient for the power demand, while reserving the available water during the rest of the day. The peak power operation can be made by monitoring the water level gauge to be equipped in the pondage. Inflow discharges can be estimated by the following equations: dv dt dh dt dv dh dh = = S( H ) = ( Q in Qout ) 3,600 dh dt dt ( Qin Qout ) 3,600 = S( H ) dh S( H ) Q = + dt 3,600 in Q out The following is an example of inflow estimate: Where, H : Water level in the pond (m) dh/dt : Fluctuation of water level in the pond in one hour (m/hour) Q in : Inflow into the pond (m 3 /s) Q out : Turbine discharge (m 3 /s) S(H) : Surface area of the pond at water level of H (m 2 ), which is expressed as (ah 2 + bh + c) -43- The Study on Introduction of Renewable Energies

51 Qin (m 3 /s) Nomogram for Inflow Estimation dh/hour : fluctuation of water level in 1 hour Average water level : EL unit operation 1) Power operation with 2-unit (320 kw, Qout=0.65 m 3 /s) 2) 2) Reading of water level in the pond by pressure gauge 3) 3) When fluctuation of water level during unit operation hour is -0.35m, and average water level is m under 2-unit operation Q in = x ( ) x ( ) / 3, = m 3 /s dh/hour (m/hour) Figure Inflow Estimation The opening degree of the guide-vanes are to be kept constant during the time on peak. Sand Flushing through the Saxophone Suction Head To utilise a head between the pondage and outlet without using other energy such as electricity or diesel. Sand flushing can be made under power generation, therefore it is not necessary to stop power generation during a sand flushing operation. There is a experimental data reported that about 10% of the sand volume density can be flushed. However, it is noted that such a flushing percentage is subject to the nature of sediment deposit. It is reported that this metod is suitable to flush sediment in a pondage or a de-silting basin where sediment is light and particle size small. Consequently, simple and small-scale flushing facilities are needed for such a pondage or a de-silting basin The Study on Introduction of Renewable Energies

52 Sediments Head Open Slots Source: D.K.Lysne, New Norwegian Institute of Technology Figure 'Saxophone' Sand Flushing Example: Pipe φ = 15 cm, L = 20 m V 2g H = 1 + f + N f e b + f f e = 1.00 (inlet loss), N f b = 0.40 (bend loss), f = f r (L/D)=4.5 (friction loss) f r = 12.7g n 2 D 1/3 = and n = (roughness coefficient) When H (head) = 1.5 m, V (velocity) = 2.06 m/s, Pipe φ = 15 cm, L = 20 m, H = 1.5 m, V = 2.06 m/s Q = m 3 /s (= 2.19 m 3 /min = 131 m 3 /hr) : discharge flushed Sand= 131 m 3 /hr x 10%* 1 = 13.1 m 3 /hr (= 315 m 3 /day *2 ): sand volume flushed Note: *1 : In reference to the experimental data as a calculation example. *2 : In application of 24 hours as a calculation example for the daily working hours of the sand flushing device The Study on Introduction of Renewable Energies

53 Table Sand Flushing Capacity of 'Saxophone' Suction Head Dia. L H V Q Q Sand Sand (m) (m) (m) (m/s) (m 3 /s) (m 3 /hr) (m 3 /hr) (m 3 /day) The Study on Introduction of Renewable Energies

54 2.6 Penstock Head Tank Trashracks Spillway FSWL MOL Sand Drain Gate Penstock Max. Pressure Rise Min. Pressure Drawdown > Penstock Elevation Static Head Powerhouse Hydraulic Grade Lines Anchor Block Negtive pressure occurs Hydraulic Grade Line 50 ~ 100 m max. Max. velocity 2.5 m/s (inlet) ~ 5.0 m/s (outlet) 55º max. TWL Figure Penstock Alignment of the penstock should be designed to be located below the minimum hydraulic grade line during the load rejection to avoid negative pressure The Study on Introduction of Renewable Energies

55 Types of Penstock are summarised as follows: Table Types and Features of Penstock Type Open type L1 φ 1 l 1 α 1 O2 y Features l 2 L2 b Fille b Saddle x O ψ O4 α 2 O Anchor Block φ 2 w 60 Most commonly applied to small hydro schemes Anchor blocks are provided at bend portions, which should be founded on firm foundations enough to support the blocks with penstock pipes against sliding, over turning and bearing. Interval of each anchor block should be less than 100 m generally. Saddle piers are provided at 6 m interval. Maximum angle of pipe inclination should be 55 Drainage and slope protection should be considered for the open excavated areas. Expansion joints just below the head tank and between each anchor. Bitumen between pipes and anchors/saddles to avoid corrosion. Buried type Applicable to the following conditions: (a) soft foundations not to support the anchor blocks (b) areas susceptible to attack of landslides or running water (c) gentle slopes to keep the stability of backfill materials Steel pipes should be galvanised, and double coated with either bitumen or high zinc content paint. Tunnel type Generally not applied in small/mini hydropower schemes The Study on Introduction of Renewable Energies

56 Water hammer analysis Water hammer can be computed by the Allievi s Equations for simple penstock pipes without branches. The computer programs and the example are attached in Appendix 2-7 of Part 6-2 in Volume 6.. Wave Velocity of Water Hammer a = 1 w0 1 1 D [ + ] g K E t Equivalent Sectional Area Equivalent Wave Velocity A a m m = Li = L i A ) ( i L L ( i i i a ) t r Allievi's Equations (1) 1st phase ' H 1 1 = 2 ρ (1 ψ 1 H ' 1 ) t i = t 1 + ( i 1) µ 2 ' 2 2 ' 2 H1 (2 + 4ρ + 4ρ ψ 1 ) H1 + (1 + 2ρ) = 0 i µ ψ i = 1 T µ = 2L a (2) after 2nd phase H ' ' + H 2 = 2ρ ( ψ H ψ ' ' i 1 i i 1 i 1 i i H ) ρ = ρ = a V0 2g H a V0 2g H 0 0 H A ' 2 i ( B 2A) H + A ' i 2 = 0 ' ' = H i 1 2 2ρψ i 1 H i 1 H ' i = hi + H H 0 0 B = ( i 2ρψ ) 2 Head Tank FSWL Penstock Max. Pressure Rise Static Head Figure Powerhouse TWL H/H Water Hammer at Turbine Time (sec) Water Hammer Analysis -49- The Study on Introduction of Renewable Energies

57 Head loss An effective head to be used for the estimate of power output can be obtained from a head difference between Full Supply Water Level (FSWL) at the head tank and Tail Water Level (TWL) at the powerhouse after deducting head losses. The head losses between the head tank and the powerhouse are expressed as follows: Head Tank Penstock Powerhouse Trashracks FSWL vin 2 /2g vin FSWL Anchor Block vout 2 /2g vout TWL Figure Head Loss (1) Velocity Head in Head Tank 2 v h = in 2g V 1 in : velocity in head tank (2) Head Loss at Trashracks h2 = f r 2 v1 2g f r b t = 2.34(sinθ )( ) b t b V1 4 3 θ h 2 : head loss of trashracks (m) f r : head loss coefficient V 1 : velocity before trashracks (m/s) θ : inclination of trashracks (º) θ = 60 ~ 70º t : width of bar (mm) t = 5 ~ 9 mm b :space between bars (mm) b = b 100 = 100 ~ 150 ~ mm Figure Head Loss of Trashrack -50- The Study on Introduction of Renewable Energies

58 (3) Head Loss at Penstock Inlet 2 v2 h3 = f e 2g v2 v2 v2 fe = 0.5 fe = 0.25 fe = 0.2 Figure Head Loss of Penstock Inlet h 3 : head loss at entrance (m) f e : head loss coefficient of entrance v 2 : velocity after entrance (m/s) (4) Head Loss due to Friction in Pipe h 4 = 124.5n 4 3 D 2 2 v L 2g (5) Head Loss due to Bend h D = { ( ) R θ } ( ) v 2g h 4 : head loss due to friction (m) n : roughness coefficient of pipe D : pipe diameter (m) L : pipe length (m) v : velocity in pipe (m/s) h 5 : head loss due to bend (m) D : pipe diameter (m) R : bend radius (m) θ : bend angle (º) v : velocity in pipe (m/s) D R v θ f gc (6) Head Loss due to Pipe Reducer 2 v h = 2 6 f gc 2g A1 v1 θ L v2 A2 h 6 : head loss due to pipe reducer (m) f gc : head loss coefficient of reducer θ : reducer angle (º) L : reducer length (m) v 1 : velocity before reducer (m/s) v 2 : velocity after reducer (m/s) θ º (7) Head Loss due to Branch Source: Hatsuen Suiryoku Ensyuu Figure Head Loss Coefficient for Reducer -51- The Study on Introduction of Renewable Energies