Solu Khola (Dudh Koshi) Hydroelectric Project (86 MW)

Project Brief

Solu Khola (Dudhkoshi) Hydroelectric Project (SKDKHEP) is an 86 MW Run Of River (RoR) type of project located at Solududhkunda Municipality & Thulung Dudh Koshi Gaupalika (Former Tingla, Kangel & Panchan VDCs) of Solukhumbu District, Sagarmatha Zone, Nepal. The project area is about 130 km (aerial) east of Kathmandu and is situated within longitude 86°37’35” to 86°41’15” East and latitude 27°21’53” to 27°25’15” North. The project utilizes a design discharge of 17.05m³/s from Solu Khola and the elevation difference between the proposed intake at Solu Khola and powerhouse at Dudhkoshi River for power generation.

The proposed headworks is located at Gairigaun village of Solududhkunda Municipality, about 600 m downstream of the suspension bridge over Solu Khola (River) at Sanghutar. Surface settling basin, headrace tunnel, pressure shaft tunnel passes along different places of Thulung Dudh Koshi Gaupalika. The proposed powerhouse, switchyard and tailrace canal all are located near Maikubesi of Thulung Dudh Koshi Gaupalika, on the right bank of Dudh Koshi River, about 1 km upstream of the suspension bridge over Dudh Koshi River at Jaleshwor Mahadev.and 3.5km upstream of the confluence of Solu Khola and Dudh Koshi River.

The project consists of a simple weir with undersluice, side intake, gravel trap, approach channel, an desalting basin, headrace tunnel, surge shaft, inclined pressure shaft and horizontal penstock tunnel, surface powerhouse and a tailrace canal.

Project Progress and Present Status:

Survey License obtained.
Feasibility study completed.
Connection agreement signed with NEA.
Generation License obtained.
PPA signed with NEA.
Syndicated Credit Facilities signed with NIBL as lead bank along with 10 other banks and investment company as consortium members.
Transmission Line Survey License obtained.
Hydro Venture Pvt. Ltd. acquired.
Generation License transferred to Sahas Urja Ltd.
Detailed Engineering Design being carried out by Hydro Consult Engineering Ltd.
Physical Model Tests carried out in Hydro Lab.
IEE for Transmission Line Approved.
Camp construction completed on headworks and powerhouse.
2 Bailey bridges installed at project area.
Access road to headworks and powerhouse completed.
Land Acquisition ongoing.
Civil construction work ongoing.
Hydromechanical work ongoing.
Electro-Mechanical work ongoing.
Transmission Line work ongoing.

Strengths of the project:

Smaller intake and waterway structures.
Shorter tunnel length.
Higher percentage of dry energy compared to other projects in Nepal.
Connection agreement signed for a nearby substation (<14 km)
Minimum length of access road to be constructed (<15 km)
Minimum socio-environmental impacts
Satisfactory social support to the Project.
Dedicated Transmission line in Double Circuit 132 KV transmission line to Lammane Substation, Necha-Salyan.
All expenses will be borne by NEA for construction of Substation.
Stable rock and good land area for penstock alignment.
Hydrology is very reliable and is justified with various hydrological data.
High head with low design discharge.
Flow of semi snowed river- dry season discharge is maintained

Salient Features

S.N.	Components
Project Location	Solukhumbu District, Province 1
Intake Site	Solududhkunda Municipality
Powerhouse Area	Thulung Dudhkoshi Gaupalika
Latitude	27°21’53”N to 27°25’15”N
Longitude	86°37’35”E to 86°41’15”E
General
Name of River	Solu Khola
Type of Scheme	Run-of-River
Gross Head	613.20 m
Net Head	598.09 m
Installed Capacity	86,000 kW
Hydrology
Catchment Area	454 km²
Design Discharge	17.05 m³/s
Design Flood Discharge	475 m³/s (100 Yr. Flood)
Diversion Weir
Type of Weir	Gravity free flow concrete
Length of Weir	31.8 m
Max. Height of Weir	13.50 m from foundation level
Crest Elevation	EL. 1,262.00 masl
Intake Structure
Type	3 no.s of Side intake
Size (W x H)	4.00 m (W) x 2.30 m (H)
Crest elevation of Intake	EL. 1,258.00 masl
Undersluice Structure
Type and number	3 nos with Gate
Size (W x H)	1.50 m (W) x 1.00 m (H)
Crest elevation of Undersluice	EL. 1,256.00 masl
Gravel Trap
Type	Rectangular, RCC
Size	5.00m (W) x 5.00 m (L)
Bed load size to trap	5 mm
Approach Canal
Type and Number	Free flow box culvert, total 3 nos
Size	2.6 m x 2.6 m
Desanding Basin
Type	Surface
No of Bays	3 Nos
Dimension (L x B x H) m	85 m (L) x 9.00 m (W) x 5.00 m (H)
Particle Size to be Settled	0.15 mm (90% trapping efficiency)
Outlet Water Level	EL. 1,259.30 m
Headrace box Culvert
Length	34.50 m
Size	4.5m (W) x 4.5m (H)
Numbers	1 (One)
Headrace Tunnel
Section Type	Inverted-D
Length	4469.61m
Size	4.0m (W) x 4.25m (H)
Support	Shotcrete, Ribs, Rock bolt
Surge Tunnel
Size	4.0m x 4.0m of 375.0m length in slope
Penstock
Length upto Bifurcation	1864.0 m
Horizontal section before Drop Shaft 1	220.0 m
Drop Shaft-1	189.0 m
Inclined Section 2	534.0 m
Drop Shaft-2	252.0 m
Inclined Section 3	669.0 m
Internal Diameter and length	2.50 m for 1^st 1130 m length, 2.25m for next 450m length and 2.1m for 270 m length (last portion)
Thickness of steel penstock	12 mm ~ 46 mm with yield strength 350 to 460 MPA
Powerhouse
Type	Surface
Size	49.6 m x 15.2 m x 32.96 m
Tailrace
Type	Free Flow, Box Culvert
Length	70 m
Size (B x H)	4.6 m x 1.9 m
Turbine
Type	3 no. Vertical Axis Pelton
Speed of Turbine	750 RPM
Rated Output Capacity per Unit	3 x 30.32 MW with 10% COL
Efficiency	91%
Governor
Type	Digital/Hydraulic with PID Control
Adjustment for Speed Drop	Between 0 to 5 %
Generator
Type	Synchronous 3 Phase
Rated Output Capacity per Unit	34.6 MVA
Voltage	11 kV
Efficiency	97%
Transformer
Type	Out Door, Oil Immersed
Rated Capacity per Unit	Three Phase 35 MVA total Nos 3
Frequency	50 Hz
Transmission Line
Length	12.0 km
Voltage	132 KV
Interconnection Point	Proposed NEA sub-station at Lammane, Tingla, Solu.
Power and Energy Generation
Mean annual energy per year	520.20 GWh (Dry- 100.27 GWh, Wet- 419.93 GWh)