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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


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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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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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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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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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