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small hydro with high head
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1
HIGH HEAD SMALL HYDRO
SPONSORED BY
NATURAL RESOURCES CANADAIN CONJUNCTION WITH THE
INTERNATIONAL ENERGY AGENCY
by Jim Gordon, P. Eng.
2
DISCUSSION SUBJECTS (1)
• High Head Small Hydro - DEFINITION• ACCESS ROADS• BED-LOAD AND SEDIMENT• DIVERSION WEIR• INTAKE• CONDUIT OPTIMIZATION• CANAL PIPELINE & TUNNEL
3
DISCUSSION SUBJECTS (2)
• PEAKING STORAGE• SURGE TANK• PENSTOCK• POWERHOUSE• EQUIPMENT• EQUIPMENT SELECTION PROGRAM• CONCLUSIONS
6
Harca Development. 25MW, 346m head, flow = 8.2m3/s.Equipment - Two 2-jet Pelton units with horizontal axis.
Schematic profile.
2,000m
500m
7
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%.
9
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.
12
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.
14
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.
18
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.
19
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 ---------------->
21
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.
22
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.
23
Zongo Dam. Crest EL 4,634m.|||V Small side-hill canal
Side hill canal captures glacial melt-waters
24
Above - Spray side-hill canal,Bow valley, Canada.
Right - Harca side-hill canal,Zongo valley, Bolivia. Note tunnelentrance in center.
26
Pingston Creektunnel, British Columbia.
2.3m wide by 2.3m high
Minimum size forexcavation with railequipment.
27
Doran-Taylorburied penstock.0.61m diametersteel pipe.Length, 1893m.
British Columbia.
Head = 652m.Capacity = 5.3MW.
29
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.
30
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.
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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.
33
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.
34
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.
35
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.
37
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
41
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.
42
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.
43
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.
44
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.
45
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.
46
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 ----------->
47
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.
48
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.
49
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.