Small Hydro Development in Nayar river valley in Lesser Himalayas – A Case Study
Devadutta Das Professor (Hydro-electric)
Department of Water Resources Development & Management Indian Institute of Technology, Roorkee Uttarakhand, INDIA – 247667
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WHY SMALL HYDRO? As many of the economical sites got exhausted, a re-look was necessitated towards the abandoned sites as well as for new small hydro sites, as a Governmental thrust for exploiting renewable energy, of which the hydro and notably small hydro are the most eligible candidates due
to their negligible impact on the environment.
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Project Area
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2975 m
3098 m
H AT TA L
G AD
DUNAO SHP 2 x 750 KW (Under Construction by Uttarakhand Jal Vidyut Nigam Ltd.) POND LEVEL : 1095.5 m EL TAIL WATER LEVEL : 1032.5 m EL
LANSDOWNE
BYALIGAON SHP 2 x 1125 KW
SATPULI
POND LEVEL : 628.0 m EL TAIL WATER LEVEL : 606.0 m EL
10.70 Km
7.0 Km
NAYAR RIVER
POND LEVEL : 589.0 m EL TAIL WATER LEVEL : 566.2 m EL
Km
PAURI
SANTOODHAR - II SHP 2 x 1000 KW
Km
POND LEVEL : 733.0 m EL TAIL WATER LEVEL : 702.6 m EL
11 .0
Km
60 3. ER IV R Km AR 0 .6 AY m 15 N K N 0 R 4.5 TE 4 ES W
0 .3 25
SANTOODHAR - I SHP 2 x 1000 KW
EA ST ER N 67 NA .7 Y 0 A Km R R IV ER K
BAIJRO
MARORA DAM NAYAR HEP 3 x 5666 KW POND LEVEL : 516.0 m EL TAIL WATER LEVEL : 458.5 m EL
Alaknanda River
˜ 6.0 Km
POWER HOUSE NEAR KHANDASAIN VILLAGE
Bhagirathi River
GANGA Dev Prayag
Vyas Ghat
RISHIKESH
HARDWAR
NOTE: Distances shown are approximate
SCHEMATIC DIAGRAM SHOWING HYDRO-ELECTRIC PROJECTS UNDER CONSTRUCTION & UNDER PLANNING IN THE NAYAR RIVER VALLEY
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VIEW OF THE DIVERSION DAM SITE FOR NAYAR SHP NEAR MARORA PALA VILLAGE
VIEW OF THE DIVERSION DAM SITE FOR BYALI GAON SHP
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VIEW OF THE DIVERSION DAM SITE FOR SANTOODHAR - I SHP
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VIEW OF THE DIVERSION DAM SITE FOR SANTOODHAR - II SHP
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FLOW DURATION CURVE FOR NAYAR RIVER DISHCRAGE GAUGED AT BUNGA GAUGING SITE
River Discharge in cumec
400 350 300 10 YEARS
250
50% Dependable Year 75% Dependable Year
200
90% Dependable Year
150 100 50 0 0
10
20
30
40
50
60
70
80
90
100
River Flows Available for the %Time of year (Equalled or Exceeded)
FLOW DURATION CURVE FOR NAYAR RIVER DISCHARGE GUAGED AT BUNGA GAUGING SITE
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Byaligaon SHP
Santoodhar – I SHP
Santoodhar – II SHP
Maximum discharge (cumec*)
198.51
120.19
165.18
Minimum discharge (cumec*)
1.02
0.62
0.85
50% dependable discharge (cumec*)
6.47
3.91
5.30
75% dependable discharge (cumec*)
4.35
2.63
3.61
90% dependable discharge (cumec*)
3.10
1.86
2.56
Maximum Flood (cumec*) for flood marks
1010
325
785
Maximum Flood (cumec*) (Dicken’s)
2402
1648
2092
Characteristics
Dicken’s empirical formula is given in equation Q = C.A0.75 Where, Q = Flood discharge in cumec C = A constant varying between 11 and 14 A = Catchment area in square kilometer For the Himalayan area, it has been found that a value of 14 for the constant C is 11 appropriate, and hence adopted.
SELECTION OF DIVERSION STRUCTURE The rivers in Himalayas carry very heavy sediment load
and bed load during rainy season. For
small
hydro
power
projects,
the
diversion
arrangements may be one of the following depending upon the site conditions and cost factors:
Trench Weir
Un-gated overflow type raised weir
Gated weir
Dam with gated spillway
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TRENCH WEIR ď ś Catches the bed load especially the shingles thereby removal of heavier material in the desilting tanks makes
the latter larger in size and thus cost. ď ś With low gradient river slopes the shingles excluder length becomes very long thereby increasing the cost.
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14
15
16
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UNGATED OVERFLOW TYPE WEIR ď ś Has the advantage over the trench weir as it lends to increase in head appreciably incase of low and medium
head
projects
thereby
contributing
to
increasing power. ď ś Entry of bed load especially the shingles into the water conductor system can be prevented at the intake by
keeping the sill level at a higher level than the bed level of the river.
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20
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WEIR WITH GATES
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23
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DIVERSION WEIR To be designed to pass the probable maximum flood through gates. With narrow diversion sites the cost of constructing a weir with gates becomes higher due to excavation cost for widening the river section to provide enough section to pass the flood. For Santoodhar – II - Cost of ungated overflow weir Rs. 34.33 Million - Cost of gated weir Rs. 52.45 Million Hence, overflow type ungated weir with under sluice adopted.
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597.0 596.0
D/S Wing POND LEVEL
589.0 HFL
589.0
FLOW Stop Log
4 ROWS OF C.C.BLOCKS OF SIZE 1500X1500X1000
RIVER BED 582.0 m
Stilling Basin
582.0 m
Friction Blocks
pe se Slo Rever : 1
2.5 : 1
5000
588.0
FLOW
Gate
5
579.0
600
6 ROWS OF C.C.BLOCKS OF SIZE 1500X1500X1000 2500
HFL
582.0
9000 597.0
Firm Rock 600
1000 6000
2000
U/S HFL
600
1000
7500
596.0 ROCK SLOPE FACING WITH CC M20
1000
7500
30000
SECTION: B-B' THROUGH UNDERSLUICE POND LEVEL
589.0
589.50
589.0 D/S Wing 588.0 D/S HFL
2.5 1
FLOW 4 ROWS OF C.C.BLOCKS OF SIZE 1500X1500X1000
6 ROWS OF C.C.BLOCKS OF SIZE 1500X1500X1000
RR STONE MASONRY 1:6
2500 1000
1000
6000 12000
581.0
3000
RIVER BED 582.0 m
1000
9000
1000
Slope Lined with M20
2000
7500
4000
21250
10250
SECTION: A-A' THOURH OVER FLOW WEIR
32000
4 Rows of CC Blocks of Size 1.5 m x 1.5 m and 1.0 m height
600 1000 600 20000
FLOW
FLOW
Chute blocks @ 1.60 m spacing at end of sloping glacis
A
A'
DIVIDE WALL
1000
B 8000
B' FLOW
Two Rows of Friction Blocks of Size 0.6 m x 0.6 m, staggered @ 1.5 c/c
1500
2000
1000 R
3000
6 Rows of CC Blocks of Size 1.5 m x 1.5 m and 1.0 m height
600
600
60 00
6000
PLAN OF WEIR 3100
SANTOODHAR – II SHP UNDER SLUICE & OVER FLOW WEIR
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DE-SILTING BASIN The rivers in the Himalayan region carry a heavy amount of sediment load predominantly angular quartz particles.
The recommended practice for eliminating the sediment load in India are as below: Low Head
=
0.5 mm and above
Medium and High Head
=
0.2 mm and above 27
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POWER CHANNEL SECTIONS INDICATED : - Stone Masonry - Rectangular Reinforced Cement Concrete - Trapezoidal Cement Concrete Lined Sections
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POWER CHANNEL Stone Masonry
Larger Sections – Cost saved in channel lining is more than offset by higher excavation cost
RCC Channels Channel on hill slopes in Himalayas are prone to frequent
damage due to falling rocks and under cutting due to rain water seeping between the channel bed.
Lined trapezoidal section Hydraulically the best and cost effective
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32
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Comparative Physical Features and Costs of Rectangular RCC Section & Trapezoidal lined section
Channel Geometry
Base Cost Depth Velocity Discharge width Rs. meter m/sec cumec meter Million
Trapezoidal section- cement concrete lined
2.50
2.50
1.89
13.26
39.27
Rectangular- RCC
2.75
2.75
2.15
13.15
57.60
As the cement concrete lined trapezoidal section is cheaper by about 32%, the same has been adopted.
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FOREBAY Forebay’s Active Volume made equal to 30 sec water requirement of the power plant at rated load.
PENSTOCK As length of penstock is less, two separate penstocks used feeding its turbine
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FIXATION OF INSTALLED CAPACITY The installed capacity of each of these projects has been determined considering the following factors: Maximum, Minimum and 50% dependable discharge available, Net Head availability, Normative plant load factor for recovery of full fixed charges fixed by the Uttarakhand Electricity Regulatory Commission , Difficulty in construction of large sized open channels in the hilly areas, and 37 Operation and Maintenance expenses.
FIXATION OF INSTALLED CAPACITY Considering difficulty in constructing large width
channel in unstable hill slopes. Maximum 15 cumec discharge adopted.
Bed slope of 1 in 700 adopted to assist in self cleaning. Normative Plant Load Factor for small hydro permitted by Uttarakhand Electricity Regulatory Commission is 45%. Installed capacity of 2000 KW for Santoodhar – II fulfilled the above criteria.
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TURBINE & GENERATOR The average net head available for the three SHPs are as under: Byaligaon SHP
Santoodhar – I Santoodhar – II SHP SHP
Average Net Head
16.80 m
26.40 m
18.80 m
Maximum Net Head
18.00 m
27.00 m
19.60 m
Minimum Net Head
16.40 m
26.00 m
18.30 m
Kaplan (Horizontal)
Francis (Horizontal)
Kaplan (Horizontal)
Type of turbine proposed
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TURBINE PARAMETERS AND SETTING ď ś With horizontal shaft alignment leakage from turbine seal is excessive if turbine is set below tail water level.
ď ś During maintenance, risk of flooding of turbine floor likely if turbine is set below tail water level. Therefore, specific speed of turbine so selected as to have positive suction head or at least a small negative suction head. 40
Turbine Parameters and Setting Byaligaon SHP
Santoodhar – I Santoodhar – II SHP SHP
No. of units & unit output
2 x 1225 KW
2 x 1000 KW
2 x 1000 KW
Turbine rotational speed, rpm
500
500
500
Specific speed, rpm (in kW-m units)
506
271
425.5
Runner Diameter (mm)
1150
860
1100
Suction Head, m
(-) 0.92
(+) 3.72
(+) 1.06
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42
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Motor operated slide gate 586.20 585.20
FLOW ROOF TRUSS
577.38
2000
576.50
574.50
575.0
50 0
569.50
CONTROL 500 ROOM
500
12000 SERVICE BAY FLOOR
566.00
566.0
TOP OF WING WALL 565.20
3000
564.70 MAX. TWL
1350
DRAFT TUBE GATE
11 6
4
5 7
9
12
563.40 MIN. TWL 13
C.C.BLOCKS INTERCONNECTED 1000X1000X500
562.30 1
8
562.5
561.30
500 5 1
L-SECTION OF POWER HOUSE
150
1000
559.05
2:1 R.C.C.M-20 OVER 150 THICK P.C.C. M-10
558.05
1000
556.90
3000
500
1000
350
2750
1100
1000
CABLE ROOM
1750
50 00 0
C/ LO FP EN ST OC K
1800
GATE
18 00
Trash Rack
10 00
F.S.L.
600 mm THICK INVERTED FILTER
12000
SANTOODHAR – II SHP CROSS – SECTION OF POWER HOUSE
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PROJECTED FINANCIAL PERFORMANCE PARAMETERS: Debt to equity ratio
: 70:30
Return on equity
: 14%
Construction Period
: 2 years
Licensing Period
: 40 years
Average annual energy production with 95%
availability 45
PROJECTED FINANCIAL PERFORMANCE Santoodhar – I Santoodhar – II SHP SHP
Characteristics
Byaligaon SHP
Average Annual Energy, kWhr
9.9 x 106
9.1 x 106
8.9 x 106
Net Energy available for sale, kWhr
9.75
8.95
8.79
Plant Load Factor
50.23
51.84
50.92
Estimated project cost, Rs. Million
205.79
180.92
176.92
Sale price, Rs./kWhr
3.47
3.37
3.29
Levelised sale price, Rs./kWhr
3.00
2.89
2.85
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CONCLUSIONS Sale Price competitive with sale price from other
hydro sources. Contribute to increased energy availability in the local rural network. Improvement in voltage profile Boost to Cottage, Horticultural and Agro Industries Energy for lighting homes Contribute to Socio – Economic Development
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