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HIGH HEAD SMALL HYDRO

SPONSORED BY

NATURAL RESOURCES CANADAIN CONJUNCTION WITH THE

INTERNATIONAL ENERGY AGENCY

by Jim Gordon, P. Eng.

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DISCUSSION SUBJECTS (1)

• High Head Small Hydro - DEFINITION• ACCESS ROADS• BED-LOAD AND SEDIMENT• DIVERSION WEIR• INTAKE• CONDUIT OPTIMIZATION• CANAL PIPELINE & TUNNEL

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DISCUSSION SUBJECTS (2)

• PEAKING STORAGE• SURGE TANK• PENSTOCK• POWERHOUSE• EQUIPMENT• EQUIPMENT SELECTION PROGRAM• CONCLUSIONS

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High Head Small Hydro DEFINITION

• PLANT CAPACITY < 50MW• FLOW < 20 m3/s.

5Zongo storage dam, Bolivia. FSL = 4,634m.

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Harca Development. 25MW, 346m head, flow = 8.2m3/s.Equipment - Two 2-jet Pelton units with horizontal axis.

Schematic profile.

2,000m

500m

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ACCESS ROADS• Very expensive in mountainous terrain.• Require ample construction time.• A site with 600m of head, will require at

least 10km of road to reach intake from powerhouse at average grade of 6%.

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Zongo valley, Bolivia. Verydifficult access road construction terrain.

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BED LOAD AND SEDIMENT

• Must be excluded from intake.• Volume of sediment a function of average

river grade.• Size of sediment a function of average river

grade. Severe sand erosionon impulse needlecones. Head 398m.

Cañon del Pato, Peru.

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Sand and gravel in river bed.

Logs in river.

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Severe erosionand cavitationin a smallPelton runner.

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DIVERSION WEIR

• Should not restrict passage of sediment.• Weir crest at river bed level.• Rubber dam for crest level control.• Intake channel at right angles to flow.• Low level sluice downstream of entrance to

intake channel.• Gravel and/or sand trap in intake channel.

13Chururaqui weir on Zongo River, Bolivia.

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View looking upstreamfrom gravel trap area atstoplogs placed parallelto flow. Stoplogs set at just below water surfaceto skim off cleaner water.

Stoplogs adjusted dailyduring flood season.

Chururaqui intake, Zongovalley, Bolivia.

15Maggotty weir and gathering tube intake, Jamaica.

16Maggotty Weir in Jamaica.

Section through Gathering Tube Intake

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Rubber dam spillway at theSoo River development.13.5MW, 104m head.

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INTAKE

• Close trashrack spacing required.• Bar spacing is wider with Pelton units.• Francis and Turgo units require more

narrow bar spacing.• Clogging with twigs and leafs likely.• Where floating debris a problem, consider

using a gathering tube intake design.

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Andekaleka dam and intake, Madagascar.56MW, 214m head. 2 Francis units.

Section throughgathering tube intake.

Section throughsluices.

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< --Cañon del Patoclose spaced racks,opening about 35mm.

Severely erodedneedle ------------------->

Severely erodedneedle casing ---------------->

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CONDUIT OPTIMIZATION

• Conduit from intake to powerhouse usually most expensive project component.

• For pre-feasibility sizing use -4% to 6% head loss in energy plants.6% to 8% head loss in peaking plants.Head loss/m in penstock = 2 x head loss/m in conduit upstream of penstock.

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CANAL, PIPELINE & TUNNELWhere the side slope is steep -

• Avoid using canals.• Pipelines should be buried.• Tunnels are preferred - but minimum tunnel

size about 2.5m wide, 2.5m high.

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Zongo Dam. Crest EL 4,634m.|||V Small side-hill canal

Side hill canal captures glacial melt-waters

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Above - Spray side-hill canal,Bow valley, Canada.

Right - Harca side-hill canal,Zongo valley, Bolivia. Note tunnelentrance in center.

25Harca canal. Note danger from falling rocks on right.

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Pingston Creektunnel, British Columbia.

2.3m wide by 2.3m high

Minimum size forexcavation with railequipment.

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Doran-Taylorburied penstock.0.61m diametersteel pipe.Length, 1893m.

British Columbia.

Head = 652m.Capacity = 5.3MW.

28Corani penstock, BoliviaH = 585m. L = 1,158m.

Chururaqui penstock, Boliviad = 1.14m. H = 369m.

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PEAKING STORAGE

• Consider using nearby gully.• For tunnels, tunnel itself and side chambers

are an alternative.• For a headpond, divide in two, with small

pond at intake, connected to large pond through one-way flap gate in an overflow weir between ponds.

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SURGE TANK• Required in isolated developments and

where Francis unit in powerplant.• No surge tank = long governor times.• Program for surge tank sizing included in

software.

Black Bear Lake frequency chart61

59<----1 minute---->

Isolated mini-hydro plant with nosurge tank. Electronic load control.

31Small hydro surge tank Surge tank on hillside

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Virginia Falls.Flood level at dam, meters. = 457.00 Low supply level at dam, meters = 454.00Turbine rated head, m. = 140 Elevation at surge tank tee, meters = 432.00Design full load flow, m3/s. = 20.24 Upstream conduit length, meters. = 2100.00Upstream conduit diameter, meters. = 3 Average Manning friction coefficient= 0.011Conduit velocity m/s. = 2.86 Tank diameter, meters. = 6.41Elevation top of tank, meters. = 470.79 Elevation bottom of tank, meters. = 443.12Tank height, top to bottom, meters. = 27.67 Tank volume, cubic meters. = 892Steel weight in tank and legs, tonnes= 58.917 Total height of tank, tee to roof, m. = 38.79Cost of steel tank, millions of US$ = 0.339 If in rock, total tank/ris. volume, m3 = 971Rock excavation volume, allowing for a full concrete lining of tank and riser, m3. = 1323Concrete lining volume, m3. = 351 Curved formwork area, m2. = 662

Surge tank size & cost program - insert data in blue cells.Calculates tank diameter, top and bottom elevation, rockexcavation and concrete quantities if in rock, steel weightif above ground.

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PENSTOCK

• Preference for a buried hyperstatic (normal) design, with shut-off valve at upper end.

• Isostatic design has every second bend free ----------->- difficult to design.- no cost saving.- governing condition = earthquake + waterhammer + bend miter (with stress

intensification) stresses at junction.

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Pingston Creekpenstock. Cans beingplaced in trench readyfor welding and bury.Diameter = 1.2m.Length = 620m.

30 MW in two units.Head = 553m.Flow = 6.4m3/s.Horizontal axis, 2-jetPelton units.

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POWERHOUSE• Preference for surface powerplants.• Tailrace to discharge directly into conduit

for next downsteam powerplant.• Locate about 100m. downstream of

penstock cut, to avoid damage from -- water on penstock rupture.- boulders and debris rolling down

penstock excavation.

36Chururaqui powerhouse, Bolivia. Impulse units set well aboveflood water level.

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EQUIPMENT• Preference for horizontal axis units due to

easier access to turbine runner.• Preference for impulse units due to very flat

efficiency curve.4 - jet pelton efficiency - flow

0.87

0.88

0.89

0.90

0.91

0.92

0.0 0.2 0.4 0.6 0.8 1.0Flow ratio

Effici

ency

1 jet2 jet3 jet4 jet

382-jet Pelton turbineDoran-Taylor

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Section through Harca powerhouse.Horizontal shaft, 2-jet Pelton turbine, 12.5MW, 346m head.

40Soo River. Two horizontal axis, high head Francis turbines.

13.5MW.104m head

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EQUIPMENT SELECTION PROGRAM - INPUT DATA

• Total powerplant flow.• Desired number of units.• Normal forebay elevation.• Total conduit head loss.• Normal and max. tailrace elev.• System frequency.• Generator power factor.

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Virginia Falls SMTS/2002/2Total powerplant flow, (max = 20) m3/s. = 7.50 Comment Print pages 1, 2.Desired number of units in powerplant. = 3 CommentNormal forebay elevation for head rating, EL. (m). = 550.00 CommentTotal conduit losses at rated flow, m. = 15.00 CommentNormal minimum tailwater elevation, m = 278.80 CommentMaximum flood tailwater elevation, m = 283.50 CommentSystem frequency, Hz. = 50Generator power factor. (Range 0.9 to 1.0) = 0.95

Total W/W Total generator Peak turbineTurbine axis, jet and runner configuration. Cost $ US m. capacity, MW efficiency

Comment Comment CommentHorizontal axis, 2 jet, 1 runner impulse turbine 4.276 15.917 0.905Combination of capacity, head and flow is suitable for this type of turbine.Horizontal axis, 1 jet, 1 turgo runner impulse turbine 3.268 15.703 0.897Combination of capacity, head and flow is suitable for this type of turbine.Horizontal axis Francis turbine 2.593 16.669 0.920Combination of capacity, head and flow is suitable for this type of turbine.

Turbine selection program. Enter data in blue cells. Output -1. W/W cost. 2. Plant MW. 3. Peak turbine efficiency.4. Statement on applicability of unit for horizontal axis 2-jet

Pelton, horiz. axis 1-jet Turgo and H or V axis Francis.

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EQUIPMENT SELECTION PROGRAM - OUTPUT DATA - 1• Powerplant output, MW.• Peak turbine efficiency.• Water to wire cost for -

- 2 - jet Pelton units.- 1 - jet Turgo units.- Francis units.

• Statement on applicability of unit.

Discarded Turgoturbine runner.22 buckets.

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Horizontal axis, 2 jet, 1 runner Pelton impulse turbineCalculated synchronous rotational speed ( rpm ) = 428.6 Rated head, m.= 249.00Calculated outside runner diameter ( m ) = 1.844 Jet diam (m) = 0.153Calculated minimum shaft centerline elevation, m = 285.34Calculated peak efficiency, all jets operating = 0.905 Peak eff. Q/jet= 0.938Calculated turbine full load output ( MW ) = 5.492 Generator MW = 5.306Calculated water to wire cost excluding subs. = 4.276 Million $ US. Comment

Horizontal axis Francis turbine CommentCalculated runner submergence "S" meters = -2.50 CommentCalculated number of runner blades = 15 Rated head, m.= 256.20Calculated runner throat diameter, ( d ) meters. = 0.595 Speed, rpm. = 1000.0Calculated peak efficiency. ( % ) = 92.03 Peak eff. Q = 2.359Calculated distributor or shaft CL. elevation, meters = 281.15 Comment Horizontal shaftCalc. turbine output at rated head & flow ( MW ) = 5.748 Generator MW= 5.556Estimated water to wire cost, excluding subst. = 2.593 Million $ US. Comment

Page 1.

Program output. 1. Runner speed. 2. Runner & jet diameter. 3. Shaft elevation. 4. Statement on shaft alignment - vertical or horizontal - for Francis unit.

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EQUIPMENT SELECTION PROGRAM - OUTPUT DATA - 2• Synchronous speed.• Impulse unit runner and jet diameters and

shaft centerline elevation.• Francis unit runner throat diameter and

number of blades, statement on whether horizontal or vertical unit, and shaft CL elev. if horizontal, or distributor casing CL elevation if vertical.

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EQUIPMENT SELECTION PROGRAM - OUTPUT DATA - 3• Efficiency versus power charts for all three

types of units. (one chart per unit)• One efficiency versus flow chart showing

comparison of efficiency for all three units.

ALSTOM turbineapplication chart ----------->

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Horizontal axis, 1 runner 2 - jet Pelton turbine efficiency - power

0.88

0.89

0.90

0.91

0.92

0.00 0.20 0.40 0.60 0.80 1.00Power ratio

Effi

cien

cy

1 jet 2 jet

Horizontal axis, 1 - jet turgo efficiency - power

0.84

0.86

0.88

0.90

0.92

0.0 0.2 0.4 0.6 0.8 1.0Power ratio

Effi

cien

cy

2-jet Pelton.Turgo

Francis turbine efficiency versus power

80

84

88

92

96

40 50 60 70 80 90 1 00

T u r bi ne po w e r r a t i o t o r a t e d po we r %

Francis turbine.

Efficiency comparison

0.4

0.6

0.8

1.0

0.2 0.4 0.6 0.8 1.0Flow ratio

Effic

ienc

y

Pelton 1 jet.Pelton 2 jet.TurgoFrancis

All 3 units.

3 charts, efficiency/power for 2-jet Pelton, 1-jet Turgo and onerunner Francis units. 1 chart efficiency/flow for all three units.

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CONCLUSIONS 1

• Roads - allow sufficient time and money.• Sediment - include sand traps.• Diversion weir - no obstruction to flow.• Intake - provide generous rack area.• Conduit optimization - loss/m in penstock =

2 x loss/m upstream conduit.• Low pressure conduit - tunnel preferred.

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CONCLUSIONS 2

• Peaking storage - in tunnel? In chambers?• Surge tank - required for Francis unit and

for isolated developments.• Penstock - buried pipe preferred.• Powerhouse - locate downstream of

penstock cut.• Equipment - prefer horizontal shaft units.

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Corani Powerhouse, Bolivia. Coscapa side hill canal, intakeand penstock, Bolivia.

THE END

THANKS FOR YOUR ATTENTION.