Brief Introduction of SH/MH Components and Civil Engineering aspects of SH/MH

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1 Brief Introduction of SH/MH Components and Civil Engineering aspects of SH/MH Janak Das Koirala Treasurer - Nepal Micro Hydro Power Development Association (NMHDA) Executive Director - AG Power Company P. Ltd. Executive Director - DAT Engineering Consultancy P. Ltd.

2 INTRODUCTION A Micro Hydro (Or A Small Hydro) Power Project Is A System Of Electricity Generation By Water Driven Forces And Power Is Supplied To Villages/Cities For Different Uses. Generally Hydro Energy From MHP Is Basically Used For Lightening. Diesel Type Mills For Grain Grinding, Rice Hulling Etc. Are Replaced By Electrical Driven Type. History of Micro hydro in Nepal - since 1960 after establishment of Balaju Yantra Shala assisted by Swiss and at the same period United Mission to Nepal (UMN) support also initiated. Water Mills were used extensively during Private Manufacturing Companies spread up in eighties.

3 Contd.. Most of the equipments/components e.g.. Gate Valves, Turbines, Trash T racks, MS Pipes for penstocks, Conductors and Load Controllers are a in general locally manufactured in Nepal. Generators are imported from abroad especially from India and China, and also from Europe in some cases. Standardization started in late eighties. Intermediate Technology Development Group (ITDG) and Agricultural Development Bank Nepal (ADB/N) contributed for enhancement of technological base of the micro hydro installations in the country. After establishment of Alternative Promotion Centre quality aspects of micro hydro power project has been given more emphasize and standards has been established in survey, design, manufacturing/fabrication and installations steps.

4 Small Scale Water Power Schemes Power supply System S.N. Type of Scheme Capacity Isolated Grid 1 Full Scale hydro >10MW 2 Mini Hydro Scheme 300KW- 10 MW 3 Micro Hydro Scheme <300KW Note: 1. Above category was made by Adam Harvey and et all, Micro Hydro Design Manual 2. Micro Hydro Schemes may or may not generate electricity, may be grid connected also and normally are of Run of River Type.

5 Nepal hydro power S.N. Size Category 1 Project < 5kw Pico Hydro kw > Project > 5 Kw Micro Hydro 3 100Kw > Project > 1 MW Mini Hydro 4 10MW > Project > 1 MW Small Hydro 5 Project > 10MW Large Hydro

6 What we do in design of a MHP? Layout Design: We Specify the locations, sizes, materials, and other parameters of all civil engineering structures/components that are to be constructed or installed at the site. Design of Electro Mechanical Equipment We determine the sizes, types of Electrical and Mechanical equipments, depending up on the proved science and engineering laws as well as national and international guidelines and practiced Economical and financial Analysis We determine the financial viability of the project by determining ng some financial indicators like B/C Ratio, Net Present Value (NPV), Internal Rate of Return (IRR) etc. Operation and Maintenance Designer should mention the level of human resources, spare parts required, frequency of maintenance of different type of equipments etc. in the design report.

7 Ideal Design Optimize the use of resources. An ideal design should be such that based on it an experienced installer i should be able to construct the scheme independently of, with only nominal assistance from, the designer. Conclude the findings and recommend to the concerned parties developer, donor, approval committee etc. for required action. Base for design The design of the scheme is based primarily on the information obtained o during the various surveys. Therefore, it can only be as good as the results s of surveys. The design process is iterative since the dimensions and other parameters p of the MHP components are interdependent.

8 Design guidelines Various organizations and institutions has developed design guidelines incorporating the national and international standards, country situation, enhancing available indigenous technology etc. Example Micro Hydro Design Manual by Adam Harvey ITDG Detail Feasibility Study and Design Guidelines AEPC, Nepal Manual for Decentralized Distribution & Generation Projects (Based on Community Participan) Uttaranchal Renewable Energy Development Agency (UREDA), India Etc.

9 MHP Project Cycle in Nepal/AEPC 1. Request for survey by entrepreneur/community 2. Pre-feasibility study by pre-qualified consultants Quality Check by AEPC 3. Detailed feasibility study Consultants: QC -AEPC 4. Subsidy Approval Further QC - AEPC 5. Project construction: PQ installation companies & manufacturers QC by independent Inspectors 6. Power verification QC by Indpnt. Inspector year warranty check QC (Indpnt. Inspctr)

10 CIVIL COMPONENTS Intake Weir Spillway Desilting Basin Headrace Canal/ Pipe Forebay Support Structures Support Piers Anchor blocks Machine Foundation Power House Tailrace

11 Civil Components of Micro Hydro Civil Components of Micro Hydro n3' hnljb't t cfof]hgfsf l;len ;+/rgfx? Trashrack Weir Intake WEIR Headrace Canal Spilway Spillway Source Desilting Basin Desilting Basin Canal River/Khola Canal Crossing Crossing Kholsa Spilway Forebay Forbay Spill way Anchor Block Support Pier Penstock Pipe Anchor Block N Anchor Block Support Piers Tailrace Power House Power House Tailrace Major Civil Components Of Micro Hydro Scheme

12 Diversion Works The diversion works of a micro-hydropower scheme control the flow of water from the source river in to the headrace. The diversion structures comprise a diversion weir, an intake, and sometimes Some river training works. Collectively the diversion works together with a gravel trap and spillway is termed as Headwork. Diversion Weir A diversion weir is a low structure (small dam) placed across the river which diverts the river flow safely in to the hydropower system s through side intake. The weir can be of a permanent, semi -permanent or temporary nature. The main function of a weir is to ensure that the channel flow is i maintained with the river in low flow period.

13 Function of Diversion works - Maintain the design flow with nominal head losses during both monsoon and dry season - prevent, or at least minimize, the bed load and other floating material entering the canal - safely contain peak flows in the river and away from the micro-hydro system so that damage is not caused to the structures.

14 Site selection General rules/principles: Diversion Weir contd Extraction of water from the river in a reliable and controllable way Use natural features of river if possible. eg. Natural Permanent pool in the river may provide the same function as a weir. Adopt traditional management known to local people Adopt traditional method of construction of temporary weirs as far as possible. Generally, It should be located m downstream of the intake depending on the site conditions. Should be located at a narrow part of the river

15 Diversion Weir contd Temporary Weir Temporary weir is constructed using boulders available at the site, stone masonry in mud mortars placed across a part or all of the river width. This is the traditional method used by Nepali farmers and quite extensively used in micro hydro schemes in Nepal. It is simple and low cost but it is not possible to divert all of the river flow in dry season by this structure. It is suitable only for the diversion of flows below 1 m3/sec Semi Permanent Weir Gabion structures can be use as semi permanent weir. If there is no significant boulder movement along the river stretch tch at the intake area, it may be effective It can tolerate some ground movement without significant damage on its body As the gabion wires are more vulnerable to damage by moving boulders, it cannot used in the steep streams, which carry such boulders. Seepage can be control by using an impermeable membrane.

16 Diversion Weir contd Permanent weir If flow is limited during dry season and river does not carry large boulders permanent weir may be built across the river. These are constructed of mass concrete, stone masonry in cement mortar and using plum concrete. A reinforced concrete surface layer may be provided to protect the t weir body from damage by boulders moving in flood season. A permanent weir should be considered in the following conditions, if: large boulders do not move in the river at the weir site. the river bed is not eroding, aggrading or shifting course. there is a scarcity of flow in dry season. there is sufficient fund for construction. the site is not in remote areas. Factors to be considered during design of weirs: If a weir across part of the river width is sufficient, it should d not be extended across the entire width. The weir length should allow safe passage of design flood. The weir height should be as low as possible but should be such that the water level rises above the upper edge of the intake mouth. The weir profile should be such that it is possible for the bed load to move the boulders to roll over it.

17 Photo : Temporary Weir

18 Photo : Permanent Weir

19 Intake/ Function of the intake/types An intake is a structure in the diversion works where the water to the power plant is either abstracted or separated from the river flow. To ensure the withdrawal of flow from the river in the required quantity and directing towards water ways of the scheme. To limit excess flow into the intake during high flow season. To control the sediment inflow towards water ways from the source e river. Minimizes hydraulic losses. Prevent formation of air vortices. Prevents floating debris, trash and ice from entering the water conveyance system. Types of intake structure are chiefly distinguished by the method d used to divert water from the river. In MHP generally two types of intake e are used: Side Intake Bottom Intake Coanda Intake ( Innovative Intake tested in a MHP in UK)

20 Side Intake A structure built along a river bank and in front of a canal / conduit end for diverting the required water safely. Side intakes are simple, less expensive, easy to build and maintain.

21 Site Intake

22 Site selection for Intake It should be possible to divert the design flow from the river towards t the headrace. The river should not change its course at the intake location over time. The river should not have high gradient at the intake site. Placed it at the side of rock outcrop or behind the large boulder Place at straight reach as far as possible In case of bend, it should be on the outer side of the bend never on the inner side of a bend. (Sediment deposit protection + dry season flow assurances)

23 Bottom Intake

24 Photo : Bottom Intake

25 HYDROLOGY

26 Design Discharge 11 month (~92%) exceedance criteria in MHP context The installed capacity should be available to the Community at least 11 months a year (12 Months for REDP Projects) Maximum demand during the winter season The driest season (12 month exceedance) is winter (mid Jan mid Feb) for streams that are snow fed & April May for streams that come from spring sources. In the absence of flow exceedance criteria, schemes could be oversized. ~ % of 11/12 months Discharge is taken as the designed discharge 5-10% for losses consideration 10% for down stream discharge

27 Civil Works General Requirement a. Flow Duration Curve (FDC) shall be established from stream gauging at least one lean season measurement. b. Q design < Q minm from FDC for stand alone mode, Down stream flow requirement must be as per government rules. c. Water conveyance system (excluding penstock and tailrace) shall be designed for 10 20% higher flow. d. Specification for drawing, c/s interval, etc.

28 Diversion and Intake a. Where to use lateral intake or a bottom intake? b. Flood period eg. For MHP<30Kw, it is 20years and for MHP>30Kw, it is 50 years. c. Orifice d. Stop log e. Provision for debris etc. Gravel Trap and Sand Trap a. Where these are not required- spring source b. Sluice gate requirement c. Size of grains to be settled are >0.2mm, minm. 90% should be settled tled for design head <100m. And it is 95% for head>100m d. L- slope should not be < 1:30 for side intake, flushing arrangement,

29 Forebay a. Shall house an overflow spillway, a drain valve or stop log gate to flush sediment, and a trash rack, Disposal requirement of spilled water b. Length, width, submergence for PSP, leakage etc. are mentioned c. Thickness of concrete Penstock a. Excavation/ depth in case of PVC/HDPE b. Types, sizes, of support piers, anchor blocks c. Movement and clearances in support structures d. About acting forces and their transmission e. Air vent and size

30 Power house a. Elevation with respect to high flood level b. Weather proof requirement, ventilation, doors, windows, roof, working space, store room, etc. c. Hoist for turbine/generator installation for >30kw d. Earthing system e. Foundation f. Drainage in cable ducts Tailrace a. Water level with respect to turbine runner b. V notch weir provision c. Energy dissipating provision

31 Weir and Intake

32 Orifice Intake Design Set V through the orifice Calculate Orifice Area required: A = Q V Set orifice height or width and calculate the other parameter: W = A H

33 Orifice Intake design (contd ) Check flow through the orifice using the submerged orifice equation: Q = AC 2g( h r hh ) Normal river water (hr) is set by weir height Canal height hh is set when sizing headrace. Ensure orifice is submerged

34 Orifice Intake design (contd ) Repeat calculations for flood flow condition Size initial headrace canal to accommodate flood flow Locate spillway as close as possible & size its capacity to spill the entire flood flow

35 CREST River / Khola C Possible Layout Possible Layout Left flood wall B B A Gabion Protection D 1:30 1:50 Gravel Trap C Gravel Flushing Gate D Spillway Canal Spillway

36 Headrace canal sizing Decide on canal type Earthen, cement masonry, concrete etc. Based on type of canal chosen, set velocity & side slopes Set either canal water depth or width and calculate the other based on Manning s equation: 1 Q = AR n 2 3 S, S = Qn AR 2 3 2

37 Headrace canal sizing Manning s s equation Q = flow in m3/s A = cross sectional area of canal (up to water depth), m2 S = Slope of the energy grade line ~ ground slope n = roughness coefficient of canal, also called Manning s roughness R = Hydraulic radius, A/P, P = Wetted perimeter sum of lengths of two sides and width of canal up to water depth: w + 2h Q = 1 n AR 2 3 S, S = Qn 2 AR 3 2

38 Headrace canal sizing Check for critical velocity (T = Top width in canal): Velocity in canal < 0.8V c to ensure stable uniform flow Sediment deposition in canals Shield s s formula d = 11RS d = Particle size transported in canal, m R Hydraulic radius, m S = canal slope V C = Design to ensure no deposition in canal. e.g., if G. trap is designed to settle particles larger than 2 mm, then, the canal from G. Trap to S. Basin must be able to transport particles up to 2 mm. Ag T

39 Canal

40 Spillway sizing Spillway required to spill excess flows during floods or for canal maintenance downstream: h overtop = C W Q xl weir 0.667

41 Spillway sizing C w for different weir Profile

42 Headrace 4.0 m 1.3 m Canal 0.98 m width = mm 0.80 m Note: required design depth = 0.5 m only, so add another spillway by reiteration Note: this headrace will be too expensive if continued downstream. Therefore, resize headrace downstream of spillway with design flow only.

43 Headrace & Spillway

44 Sizing of headrace pipe 1. Select pipe velocity based on whether upstream of G. Trap/S. basin or downstream. V ~ 1.5 m/s for headrace u/s of G. trap & ~3.0 m/s m for d/s of G. Trap 2. Calculate actual velocity: V = velocity m/s Q = design flow in m 3 /s D = pipe inner diameter in m 3. Total loss = wall loss + turbulence loss 4. Calculate head loss in pipe length, inlet & bends V Q = A = 4xQ 2 Πd

45 Gravel trap/settling basin Gravel trap/settling basin - Gravels/particles should settle in the basin - It should be possible to safely flush the settled particles from the basin - Gravels should not deposit upstream - Max gravel size governed by coarse trashrack spacing

46 Settling Basin Basic theory Ideal basin: A particle entering water surface at beginning of settling basin (point X) should reach the end of the basin (point Y) if it is to be settled

47 Settling Basin Basic theory L = settling zone length B = Settling zone width y = mean water depth or hydraulic depth t = time for particle to travel L (s) V p = horizontal velocity w = fall velocity (from Shield s s graph) Q = discharge

48 Settling Basin Basic theory For particle to reach from X to Y, these equations have to be valid: y = wt ( a) L = V Q = p BV t ( b) p y ( c) => From a, b, c, Q = BLw

49 Settling Basin Basic theory Q = BLw Therefore, for a given Q, & particle size to be settled, ideal dimensions can be determined: In practice larger basin required because: - turbulence in basin - imperfect flow distribution at entrance & - converge flow at exits, curves etc. Thus, required plan area should be doubled.

50 Settling Basin-Basic Basic theory Smooth transition L/B = 4 10 can be 27 o (1:2 1:5). d limit h < 10 m, d limit = mm 10 m < h < 100 m, d limit = mm h >100 m, d limit = mm V = Q By < 0.44 d limit If not increase cross sectional area

51 Desilting Basin Incorrect: High velocity in centre stream and turbulence in corners Correct: Low velocity throught width, no turbulence

52 Desilting Basin

53 Forebay - design criteria - Trashrack, V < 0.6 m/s, 3:1 slope - Spillway must - Air vent - Some clearance for penstock at bottom - 15 second flow storage volume above penstock pipe. - incorporate a spillway While, the minimum submergence head required for the penstock pipe h submergence 2 V = 1.5 2* g

54 Forebay Cum Desilting Basin L(exit) L(settling) = L(entry) = Trash Rack Airvent Pipe Sluice gate W(settling) = 2.50 Over Flow Length = 6.00 A. Block-1 Expansion Joint Penstock Pipe HDPE pipe (spill way)

55 Forebay

56 SUPPORT STRUCTURES

57 Penstock Alignment Support piers

58 Support piers Use of Tar paper (asbestos sheet) minimizes friction between pipe & support pier Base plate provides additional safety

59 Spacing of support piers Diameter (mm) Thickness mm support piers spacing in meter

61 Sizing of Anchor Blocks Thumb rule for P < 20 KW & h < 60 m i. Straight section: Place 1 anchor block every 30 m by keying 1 m 3 of concrete for every 300 mm pipe dia.

62 Sizing of Anchor Blocks ii.bends < 45 o Double the concrete volume than for straight section e.g., if dia=200 mm, bend = 20 o Anchor block volume=2x(200/300) =1.33 m 3

63 Sizing of Anchor Blocks iii. bends > 45 o Treble the concrete than for straight section e.g., dia. = 350 mm, Bend = 58 o Volume required = 3 x (350/300) = 3.5 m 3 Note: 1 anchor block every 30 m even if there is not a bend at this length.

64 Sizing of Anchor Blocks

65 Some construction details

66 Machine Foundation A Turbine Generator Tailrace canal PLAN A T/G Base frame Turbine Generator Anchor rods (20 mm dia.) 100 mm 1 : 1.5 : 3 Pre cast slab stone soling 1 : 1.5 : 3 RCC Stone masonry in 1:4 c/s mortar Tailrace canal (Slope=3.5%) mm RCC ( 1:1.5:3) 300 mm stone soling SECTION - AA

67 Machine Foundation

68 Power House CGI Sheet Roofing A Penstock Pipe ELC Valve BT W OPERATOR QUARTER W1 T G W D1 D1 D W Tailrace 1:40 Slope W1 A 75 mm PCC (1:2:4) 200 mm soling

69 Powerhouse and Tailrace

70 Thank You!

Types of Hydropower Facilities

Types of Hydropower Facilities 1 Impoundment Hydropower- uses a dam to store water. Water may be released either to meet changing electricity needs or to maintain a constant water level. 2 Run-of-River