Cover Image
close this book Local Experience With Micro-Hydro Technology
close this folder E. PROJECT EXAMPLES


a) Scheme Details

b) Power Transmission and Use

c) Implementation and Present State

d) Investment Cost

Salleri is a small but lively town and the district headquarters of the Solu Khumbu district in Eastern Nepal. Nearby there is a new village, inhabited by Tibetans who settled in Nepal in the early sixties, named Chialsa. While the people in Sallerie are occupied in government posts, agriculture and trade, the people from Chialsa derive their livelihood mainly from carpet making, because at the higher elevation of Chialsa, only marginal agriculture is possible. The wool used for carpet making has to be dyed prior to weaving. This is done in large vats, where the wool-dye and water solution is boiled for hours. The energy source used for this purpose is firewood. Over the last 15 years, this practice resulted in partial deforestation of the area, because in addition to the use of firewood in domestic cooking, about 500 kg of wood were used daily for wool-dyeing. This precarious situation was the starting point to investigate the construction of a small hydropower station. A good project site lies in the steep valey of the Solu Khola, about three kilometers south-west of Chialsa, and 4 km south of Salleri. The Solu Khola is a beautiful snow-fed mountain river. Even in the dry season the minimum runoff exceeds 2 m3/s. The river has almost no bed load; a rare exception for a Himalayan river of this size.

An almost natural intake exists, but the required canal of 450 m length needed to be cut along a very steep hill slope. Already in the feasibility stage it was realised that this would be the most difficult part. This was proved to be correct. In the monsoon season of 1980, land-slides occurred and major repairs were necessary. Another problem that had to be dealt with is the fact that there exists no road. A porter requires 12 days to reach the site from the nearest roadhead and otherwise only transportation by small aircraft is possible to a landing-strip about 5 km distant. The maximum load of the aircraft available is 540 kg. Porter loads of less than 50 kg and a maximum load around 500 kg for large items had to be considered.

During the feasibility study, several schemes were investigated: The first was a minimum cost scheme in which the same site would have been used but with lower head and flow, to give about 25 kW output. The dyeing operation in Chialsa would then have been moved to the site to avoid costs for electricity transmission. This scheme, while technically easy and economically viable, would have solved the problem of excessive use of firewood. Since it did not include other benefits such as lighting for the handicraft center and residential housing, it was rejected by the local people. A second scheme was to provide electricity to Chialsa, e.g. the village, handicraft center and dyeing section, with a single turbine unit of 40 kW output. People of Chialsa would have been quite happy with this solution but, naturally, people of Salleri and another village between the two, plus political leaders of the area were not very satisfied. They rejected the second scheme and instead strongly supported the third, which was then worked out in detail. The project envisaged finally to supply three villages with electricity, generated in a small hydropower station with an output of 80 kW (electrical).

Scheme Details


- Installed capacity:

1st stage

100 kVA

(2 turbines)


(+ 1 turbine)

2nd stage

150 kVa

- Design discharge:

1st stage

0.9 m³/s


2nd stage

1.35 m³/s

- Net head:


15.5 m

- Canal:


450 m

cross-section, trapezoidal

2.0 m²



1 %.

- Penstock:


800/600 mm



40 m


sheet thickness:

3 mm

- Turbines: 2, Cross-Flow T1-X400 made by BYS, Nepal


47 kW/unit

- Step-up transmission: positive drive belt, UNIROYAL


1 : 3.75

- Alternator: 1, 3-phase, 1500 RPM (50 Hz) self excited, synchronous, brushless, with 2 shaft extensions


115 kVA



380/220 V


french-made: Leroy Somer


- Speed control: Electronic 3-phase load-controller, EPFL Ballast: Hot water heater


- H.T. transmission:


7 km


A.C.S.R. section

25 mm²



6 kV


The layout in fig. 35 shows the situation at the site with the several structural components schematically. The intake (1) is almost natural and was improved by an arrangement of gabions and, in that way is of a semi-permanent nature. The canal (3), leads through difficult terrain (as mentioned before) and incorporates two aqueducts (2,4) that are needed to cross steep side gullies. Photographs in fig. 56 might give an idea of the difficulties in canal construction. The forebay (5) incorporates a trashrack and a spillway with discharge canal (6), and serves as the inlet to the penstock (7) of diameter 800 mm in the upper section, branching into two pipes of diameter 600 mm. These two branches incorporate one cast-iron gate valve each and lead to the two turbines in the powerhouse (8). Water discharged by the turbines exits through individual outlets and flows back to the river in the tail-race (9). A staff quarter (10) completes the list of structures. A step-up transformer (11) outside the power house is required to transport electricity via the 6 kV transmission line.


Fig. 55: Situation Plan of Powerplant

Source: Litscher, Small Hydel Development Board Nepal


All hydraulic conduits were designed for a discharge of 1,35 m3/s which will make later addition of another 40 kW possible, by adding another generating set. Towards this end, an extra turbine pit with outlet has also been included in the power-house structure. Connecting a third penstock branch is made possible by flanged/bolted execution of the penstock. For the second stage, one penstock section above the existing branch will have to be exchanged with another branching oars. The length of each penstock section is, incidentally, limited to 2 meters to make transportation possible.

Bearing in mind the great problems and cost of transportation, the use of local construction material to the greatest possible extent was of paramount importance. Specific technologies applied, appropriate to the situation, were:

- semi-permanent intake built with gabions

- canal lining in mud mortar implying a large canal section and a small slope for low flow-velocities (only the most difficult parts of the canal were done in stone lining with cement mortar pointing)

- the power house and staff quarter were done in mud mortar-stone masonry with local slate roofing

- other supporting structures and retaining walls were done with gabions.

These measures made it possible to limit the quantity of cement to 700 bags. Costs involved are still considerable, since one bag of cement costs Nits. 305.- at the site. This includes a transportation charge of Nits. 250.- per bag.

The generating equipment used comprises two locally made turbines (BYS, T1) that are installed under a net head of 15.5 meters. Both turbines are connected through a speed step-up transmission and a flywheel, shaft and semi-flexible coupling, to a single alternator, with a shaft extending on both ends. The transmission used is a positive-drive belt that needed to be imported. Fig. 57 shows the schematical equipment layout.

Fig. 57 Generating Equipment Layout Salleri/Chialsa, Nepal

Source: BYS, Nepal


The single-generator configuration was chosen to avoid sophistication of parallel operation with two units. Costs were another factor, since 2 generators of 40 kW each, cost more than one piece with a rating of 80 kW. The elevation of the site (approx. 1800 m above sea level) had to be considered for the size of the alternator. With a aerating factor of about 0.9, the selected machine of 115 kVA will be capable of producing an output of 80 kW (at a power factor of 0.8) on a continuous basis. For reasons of a minimal transportation weight it was necessary to import a brushless alternator from Europe. The one selected is more than 250 kg lighter compared to a slip-ring alternator offered by manufacturers in India.

Photograph fig. 58, gives an idea of what the equipment with the penstock branches looks like. The picture was taken during trial-assembly in the yard of BYS, Kathmandu.


b) Power Transmission and Use

To bring the electrical energy from the generation site to the consumers requires a high-tension transmission line due to distances involved. The system chosen is of 6 kV, with one step-up transformer outside the powerhouse and several smaller step-down transformers in the load centers. The length of hightension line is about 7 km, using local wooden poles of over ten meters length every 50 meters, and over 20 km of steel-reinforced aluminium cable of 25 mm2 cross section. In addition, some 500 insulators, H.T. fuses, lightning arrestors, earthing sets and a metal cross-arm and top-cap for each pole, are required. The diagram in fig. 59 shows the arrangement of H.T. lines and the approximate position of transformers. The line goes straight up to Chialsa with a branch to the north connecting the two villages of Salleri and Torphu. Several main distribution lines of 3-phase, 380 Volt are required in the various villages that have approximately equal length, except for the Chialsa Handicraft-Center which is very close to the transformer because its load is by far the largest. In all, about 8000 meters of steel-reinforced conductors are needed for 3-phase (4-wire system) overhead distribution lines and over 4000 meters of insulated 2-core cable for single-phase lines, with which about 250 individual consumers are connected.

Fig. 59 Schematic of H.T. Transmission Salleri/Chialsa, Nepal

Source: Meier et al., Project Proposal, Kathmandu 1976


The largest single electricity consumer will be the dyeing section of the Chialsa Handicraft Center, where dyeing pots are to be equipped with electric heating elements amounting to 24 kW, which will be required during 10 to 12 hours daily. For the rest, at least initially, no other electricity use but for lighting in individual households, offices and main streets, will exist. With an average of 120 W installed for each individual consumer and 1 to 2 kW each for the various schools, other public houses and street lighting, the installed load will amount to approximately 40 kW, bringing the installed total to about 64 kW. Lighting, naturally, will be required for a few hours only every day, so that even with a good load on the part of the dyeing section, the average overall plant utilisation factor may be as low as 20 %. This is an unsatisfactory situation since the amount of saleable energy will be relatively small in relation to the investment costs. It will therefore be a very important task to promote power use in the initial phase of operation.

c) Implementation and Present State

The implementation of the hydropower project at Salleri/Chialsa met with quite a number of problems. An initial survey was carried out by personnel of SATA (Swiss Association for Technical Assistance) and the turbine manufacturing company BYS. In the absence of a capable local organisation to implement the project, SATA could have done the job with expatriate experts. However, this would not have made local institution-building possible. The idea was to assist a local organisation in executing the project, so that this body would gain relevant experience and train their own personnel for future activities in this field. Some time later, the Electricity Department of HMO (His Majesty's Government of Nepal) created an agency named SHDB (Small Hydel Development Board ), with the task of taking care of small hydro electric power development, and SATA chose this partner to work on the Salleri/Chialsa project, and also provided an expatriate engineer, assigned to the project. It was a very difficult job for SHDB to establish itself, execute the first project, and get busy with the design of new projects, virtually all at the same time. Delays were inescapable and the far away site at Salleri caused additional problems of logistics. To cite but one example, cement ordered for the project, took one year to arrive at the site.

The state today is that the project is not operational yet. As earlier mentioned, major repairs are necessary on the most difficult section of the canal, which was damaged by land-slides during the last rainy season. The installation of the generating equipment and electrical equipment are in progress only now, and as of this writing (may 1981), a number of problems as regards ownership, staffing, operation and administration of the hydropower station remain to be solved. As a concluding remark, one may perhaps state that the project - while it may succeed finally, if due attention is paid to open questions - is a difficult one to start with, for reasons of its pilot character, remoteness, and technical difficulties. Still, if experience gained is fully used in the planning, designing, and executing of new projects, many of the problems can be avoided in future. It is perhaps useful to list some of the points to which, evidently, more very careful attention has to be paid: (Material used from Krayenbühl & Ledergerber, SHDB: Program Evaluation ...)

· Size of the plant in relation to energy requirements and also technical feasibility on the construction side.

· The need for effective load promotion to achieve a higher load factor, while avoiding load peaks of short duration.

· Avoidance of over-staffing by outside personnel who are relatively highly paid, resulting in high operation costs.

· Obtaining more participation of the local people during the construction period and possibly in ownership and administration/operation.

d) Investment Costs

The total investment cost for the project is expected to reach Nits. 2.9 million (adjusted for inflation in the last construction phase) including H.T. transmission, low tension distribution and house connections. This is relatively high and due largely to high transportation costs and difficult canal construction. Inflation during the construction period of more than 4 years has also played a role. For transportation alone some NRs. 400'000 (estimate) will have been spent once construction is finished. This would amount to more than 13 % of total cost.

The rough breakdown of costs, itemised for the various components of the system, is as per fig. 60:

Fig. 60: Cost Breakdown of Salleri/Chialsa Project,


Source: Updated from: - Litscher & Meier