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close this book Local Experience With Micro-Hydro Technology
close this folder E. PROJECT EXAMPLES
View the document 1. SALLERI-CHIALSA MICRO HYDEL PROJECT, NEPAL
View the document 2. BHORLETAR TURBINE IRRIGATION PROJECT, NEPAL
View the document 3. NAM DANG HYDRO-ELECTRIC PROJECT, THAILAND

E. PROJECT EXAMPLES

To give the reader some more insight into technological solutions and to help in understanding the uniqueness of each project and the criteria that lead to the final configuration, a few actual small hydropower stations will be described here. None of them can be called "typical" in a strict sense, since all are very situation-specific. Still, there is no doubt that similar solutions - as regards technology involved - have been, and will be, possible in future under different circumstances. It should be noted that all the projects described are of a pilot-character. They are among the first of the kind for the region concerned and are surely not fully optimised regarding cost and technical details. Rather, while still being functional and hopefully economically viable, these projects are of great importance in terms of gaining experience and in building up institutional and individual skills.

1. SALLERI-CHIALSA MICRO HYDEL PROJECT, NEPAL

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

SPECIFICATIONS:

- 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:

length:

450 m

cross-section, trapezoidal

2.0 m²

 
 

gradient:

1 %.

- Penstock:

diameter:

800/600 mm

 

length:

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

ratio:

1 : 3.75

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

 

115 kVA

 

voltage:

380/220 V

 

french-made: Leroy Somer

 

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

   

- H.T. transmission:

length:

7 km

 

A.C.S.R. section

25 mm²

 

voltage

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,

Nepal

Source: Updated from: - Litscher & Meier

 

2. BHORLETAR TURBINE IRRIGATION PROJECT, NEPAL

a) Organisation and Management

b) Benefits

c) Project Execution

d) Technical Details

e) Investment Cost

 

This project, for which a feasibility study was done jointly by the Agricultural Development Bank, Nepal (ADB/N) and the turbine manufacturing company BYS, is of quite a different nature as compared to "standard" rural electrification projects. It was financed by ADB/N on commercial terms as one component in a package of measures, and executed jointly by the local people, ADB/N and BYS. As an introduction, passages from the project proposal report (ADS/N, Lift Irrigation Project for the Development ...) are printed here:

The project area is located at Bhorletar and Aarikosi village panchayat in Lamjung district in Western Nepal. The Midim Khola, with perennial water flow, separates the two villages. The area is roughly 20 km from the nearest road head e.g. only accessible on foot in a 4 to 5 hours walk. This, for Nepal, is a very favourable access situation.

At present irrigation facilities are limited to some areas in Karaputar permitting two or more crops a year, whereas a major part of the land at Bhorletar and Bhatbeshi has no access to irrigation facilities. As such, hardly a single crop is grown in these areas i.e., paddy under the coverage of monsoon rains. Crop productivity is presently very low.

Paddy and maize are the principal crops in the area followed by wheat, mustard and potato.

An increase in crop production and productivity of land is envisaged with the provision of irrigation and other supporting services under the proposed project.

Out of a total population of 3000, the project envisages to benefit about 100 households directly comprising 500 to 600 people. The project aims to provide a complete technological package of services and institutional support to the farming community of Bhorletar area for intensive agricultural development, mainly based on the development and installation of an effective irrigation system. Other activities which are identified feasible and therefore incorporated in this proposal include: crop-production, agro-processing facilities, credit and agri-inputs, distribution and marketing arrangements for farm produce. A second project stage envisages electricity supply to the nearby bazaar for lighting and electric power supply for running a small cottage industry.

The first project phase comprises the following integrated activities:

· Development and installation of lift irrigation facilities to cover a command area of about 50 hectares of land, 25 hectares each at Bhorletar and Bhatbeshitar areas. This will involve the following components:

- The water of Midim Khola will be diverted to a 4000 meter long 1.2 m x 0.5 m headrace canal to channel 570 to 630 l/s flow to two sets of water turbines via a 40 cm diameter penstock pipe.

- Two sets of water turbines capable of generating a total of about 70 to 80 kilowatts of power output (35 to 40 kW output each) will be installed under the roof of a permanent power-house. Both the water turbines will be purely mechanical-power generating units, which will be used to lift water up to the head of 22 meters at Bhorletar and 42 meters at Bhatbeshitar.

The first turbine will be used to drive two units of water pumps (15 l/s capacity and consuming about 13 kW power each) which will lift up about 30 l/s of water to Bhatbeshitar area through a conveying canal, to irrigate about 25 hectares.

Similarly, the second turbine will be used to drive another two units of pumps in order to supply 30 l/s flow of water to Bhorletar to irrigate another 25 ha of land. The water supply pipes will be carried across from the power house to the newly constructed suspension bridge over Midim Khola to a height of 22 meters at Bhorletar irrigation command area.

Field channels will be constructed to convey irrigation water from the point of main supply to the farmers fields located both in the Bhorletar and Bhatbeshitar area.

· The establishment of an agro-processing unit is proposed to provide milling and processing facilities to the farmers of the project area in view of the expected increase in agricultural production. A paddy huller, a flour grinding unit and a small oil-expeller will be installed within the power house. The estimated power consumption will be about 10 kW when all three processing units are operated at a time. The mechanical power required for running these agro-processing units shall be directly supplied through either of the two sets of water turbines via belt drives.

· A storage building having a capacity of 100 metric tons will be constructed at a suitable site nearby the turbine and mill house. Locally available materials such as stones and river boulders will be used for most of the construction works.

·A Bank-guided co-operative society would be registered and established in the project area. A technical officer with a degree in Agriculture would be assigned by the Bank as a manager of the society. The cooperative would provide management and operational guidance to all project activities. It would also provide agricultural inputs, including production credit and other credit requirements for operating cottage industries. The co-operative will also arrange marketing of agricultural production of the farmers.

a) Organisation and Management

To execute the project, a Co-operative Society is proposed to he set up in the project area. The Co-operative Society will be governed by the Board of Directors. The manager will be assigned from the Bank and the management supervision of the Co-operative Society will be done by ADB/N up to the period of the loan. During this period, ADB/N would help the farmers to build up their own management skill. When the loan amount is fully recovered and effective operation of the project is ensured, the Bank will hand-over the management of the project to the farmers.

Besides the Board of Directors, a project implementation committee is envisaged. The committee will function as an advisory unit to the Board on operations relating to project implementation. The committee will consist of 3 progressive farmers and 2 group leaders. The latter will be elected by/among the farmers.

Balaju Yantra Shala (BYS) will be responsible for manufacturing, fabricating and installation of the irrigation and agro-processing system. BYS will manufacture the water turbine and generating equipment and will install the complete system including the agro-processing unit and then hand-over to the Co-operative Society. Construction of canals, forebay basin and pump/turbine house will be completed by the joint effort of the Co-operative Society and the farmers under the technical supervision of BYS and ADB/N.

On the operational level an effective water-distribution system would ensure optimum utilization of irrigation water. For this purpose, within the two farmers groups to be organized, specific water-users groups comprising several subgroups will be established. Their function will be:

· To ensure equitable supply and distribution of irrigation water to member farmers.

To arrange distribution of water to its members as per water distribution schedule worked out in consultation with all farmers within the group.

· To initiate the member farmers to level and improve their land structure and construction of water distribution channels so as to have optimum water utilization and minimize water losses.

· To promote cooperation among members sharing irrigation water and other inputs and to encourage the farmers for the adoption of improved farming methods.

· To help the Co-operative Society realise its loan installments and irrigation water charge from the member farmers.

· To settle disputes among member farmers in the utilization and distribution of irrigation water.

· To promote other activities related with irrigation and agricultural development within the groups.

The main canal will be constructed through joint efforts of the farmers groups whereas sub-channels will be constructed by the participating farmers themselves. Proper operation and maintenance of the turbine, main canal, agro-processing machinery and pumps etc. will be carried out by the mechanical section of the Co-operative Society, aided by staff from BYS where necessary.

b) Benefits

The project benefits envisaged may be summarised as follows:

· The project would benefit about 100 farm families of Bhorletar and Bhatbesitar by irrigating 50 hectares of "tar" areas.

· It will provide permanent employment for 11 persons and would generate additional employment to about 100 farm families at the full development of the project.

· It would provide easy access to processing of foodgrains by providing processing facilities to the farmers of Bhorletar, Bhatbesitar, Karaputar and other nearby villages.

· The project will help to utilise the water resource of Midim Khola to generate power to render irrigation and processing facilities to adjoining areas.

· Provision of storage facilities would improve distribution of agri-inputs, minimize losses and facilitate marketing of farm outputs.

· The crop production would increase from the existing level of 456 metric tons to 752 metric tons at the full development stage (5th year onwards).

· Expected implementation of the project activities set for phase 2 would benefit the local community from the proposed supply of electric power to Karaputar Bazaar and the extension of irrigation facilities to Bhorletar and Kainbote areas.

So far the project proposal! What one may note that is different from other hydropower projects, are the following points:

· Rather than rural electrification per se, the project is based on other criteria, namely increased agricultural production.

· The development of hydropower is only a means to achieve a much broader goal, e.g. integrated rural development.

· Local participation has not been included as a theoretical requirement but is in fact a decisive factor in the implementation of the project.

· The project had to be viable from its inception in terms of qualifying for loans from a bank.

· The bank involved, on the other hand, realised after studying the local situation, what additional inputs would be required from their side and consequently included these in the proposal.

· By the development of a hydropower resource for a specific productive use, a second project stage that provides for the amenity of electric light must not be economically self-supporting, but can be done as a social measure.

c) Project Execution

During project execution it became clear that many of the problems occurring elsewhere did not exist, largely due to the integrated approach and the ultimate goal of the project. The scheme was understood and supported by local people from its inception. A farmer naturally knows what access to irrigation water all through the year means in an area where even a single rainfed crop sometimes fails due to the lack of rain. In fact, it was the local people who pushed the project all along; even though at several stages they lost courage for a while, when technical and administrative problems came up. Local participation was strong. At one point, the womenfolk of the area declared that they would take care of all material transportation. And so they did without much fuss. Cement, equipment parts, penstock and irrigation pipes were all carried on womens' back to the project site.

The men, meanwhile, were working on canal excavation and power-house construction. There were delays and difficulties largely due to the fact that, for all parties involved, it was the first time that a project on this scale was taken up. Today, the project is in operation; still in an early phase though, with agricultural production slowly developing. This was anticipated in the requirements of loan repayment with a sufficiently long grace period.

d) Technical Details

Some remarks on the technical configuration of the project may be of interest. The original idea during project prefeasibility studies was to generate electrical power with the water turbines and to operate water pumps with electricity in a pumping station at the river side. This would have resulted in a geodetic head of about 53 meters to pump water up to Bhorletar. Also, an additional civil engineering structure would have been necessary on the river bank, with intake and sedimentation tank for the water to be pumped.

In the configuration finally adopted, water to be pumped is taken from the headrace canal with a separate sedimentation arrangement in the forebay so that there are still fewer suspended particles as compared to water supplied to the turbine. This necessitates a separate supply pipe parallel to the penstock, to bring water to the pump sets with positive pressure. With this arrangement, the static pumping head to pump water up to Bhorletar amounts to 22 meters only, as can be seen from the schematical profile in fig. 61. On the other hand, a relatively long (about 1 km) delivery pipe is necessary, which involves conderable friction losses. Still, the dynamic head with the existing arrangement amounts to only 49 m as compared to 58 m with a pumping station on the river bank.


Fig. 61: Schematical Profile of Bhorletar Irrigation System

Source: BYS, Nepal

There were three criteria that helped in deciding which system to adopt, namely: technical feasibility, cost, and overall system-efficiency. The two possibilities studied were both considered technically feasible but the use of a mechanical power drive must be considered an advantage because it involves a considerably less sophisticated technology as compared to electricity generation. On the cost side, it was a comparison of cost of electricity generating equipment, including transmission and the construction of a pump-house with intake and sedimentation basin in the original configuration, versus a larger head-race canal section, a longer delivery pipe, and the cost of bringing the pipe across the river, in the final configuration. It was here possible to use an existing suspension foot-bridge to which the water delivery pipe could be attached and this cost item was therefore minimal. Adding all cost up and comparing them, showed a slight but not decisive advantages for the second system. Really of major importance, and at first surprising, was the comparison of efficiencies: The mechanical system with the pumps in the turbine building showed roughly an efficiency that was better by a factor of 2 as compared to the electric system, even though it involves a more than 600 meters longer delivery pipe..

To explain this requires perhaps some elaboration: In a comparison of the overall efficiency, all components that are equally required in both systems, need not be considered. These are: Turbines, step-up transmission, and water pumps. In the mechanical system, additional losses accrue from pipe friction only, while the electrical system involves losses in the generator, in electricity transmission, in electric motors and pipe friction. Input energy in both systems is equal, and what is of interest in terms of output is the amount of water pumped, e.g. if input energy is multiplied by all additional equipment efficiencies and divided by the dynamic head, the result will be mass flow rate of water at the irrigation outlet. A numerical comparison is thus very simple and may be presented as follows:


Fig. 62: System-Efficiency Comparison Bhorletar, Nepal

The relatively long canal of 400 meters made a number of different sections necessary, depending on terrain. At two places, rectangular wooden flumes were made to cross gullies. Another seasonal rivulet with quite a broad bed had to be crossed also. This was done by covering the canal with stone-slabs to prevent the bed-load being deposited in the canal. The photograph in fig. 63 gives an impression of canal construction that was all done manually and mostly in unlined execution.

The equipment in the power house comprises two turbine sets of type T1 to which water is fed through a common penstock, branching in two, above the turbines. The two turbines, working under a net head of more than 20 m may be operated independently of each other. Each set supplies power by chain-drive to an intermediary shaft from which two pumps (e.g. totally 4 pumps) are driven with vee-belts. A third intermediary shaft in front of the turbines may be connected to either turbine, to operate the agro-processing machinery. A 10 kW alternator, envisaged for the 2nd project stage, will be operated from this shaft alternatively. Fig. 64 shows the turbine sets installed, with construction of the power house - in local mud-mortar masonry - under progress.

A speed governor is not required for the system, because the operation of water pumps constitutes a constant load. Instead, turbines are equipped with a mechanism for manual operation of the gate. With this, it is quite simple to operate the pumps. To start, the pump inlet valves are opened with the turbine still at a standstill. Because of positive pressure on the inlet side, the delivery pipe fills without operating the pumps up to the level of the head race. Ther the turbine gate is opened and the pumps are run at reduced speed just sufficient to fill delivery pipes completely. Only thereafter is speed increased to develop full dynamic head and full flow. The optimal turbine speed can quite simply be read from a pressure gauge on the delivery pipe. This procedure prevents any water hammer in the pumping system from developing.

The pumps used are of centrifugal spiral-casing type. With the concept to use local technology to the largest possible extent, a number of enquiries for pumps were made first in the region, since Nepal itself does not produce any. By comparing characteristics of pumps from the regional market with those of pumps from Europe, it was found that much more water could be pumped with machines imported from overseas, due to better matching of the latter with the actual flow/head conditions and generally higher efficiencies. Consequently, pumps were imported from Europe, although it was clear that getting spare parts would be more difficult.

e) Investment Costs

Total investment costs were initially estimated to be Nits. 540'000.-. Successively, due to inflation and not foreseen technical difficulties, the overall costs finally reached about Nits. 700'000.-(estimate at cost level of 1979, 12 Nits. = U.S.$ 1). This is the amount for the integrated project including several other activities in addition to hydropower generation. It is not possible to separate the actual cost for hydropower development alone but on the higher side, an amount of NRs. 530'000.- seems reasonable. Fig. 65 gives a rough breakdown of cost into the systems components. Since the use of power is only possible with auxiliary equipment such as water pumps, piping, and milling machinery, this is also included.

It should be noted that costs as given here are not fully representative. Canal construction is relatively low due to involvement of partly voluntary labour. Also, supervising personnel of ADB/N and an expatriate expert of BYS have not been accounted for. From the side of power end use, it is of interest to note the cost of lift-irrigation on a unit of area basis, since in the existing situation, 50 hectares of land are irrigated, cost of development per hectare amounts to $ 886. This, however, does not include such additionally possible irrigation from head race overflow and tail race water.


Fig. 65: Cost Breakdown of Bhorletar Project

Source: ADB,/N+BYS Project proposal, and own estimate based on project progress report 1979

 

3. NAM DANG HYDRO-ELECTRIC PROJECT, THAILAND

a) Technical Details

b) Investment Cost

 

The Nam Dang project, recently built and also owned by the Water Shed Management Division of the Forestry Department, is another scheme using local technology. The turbines used are of the Cross-Flow type, designed by the design section of NEA's (National Energy Administration of Thailand) technical division, and built on contract basis by a small workshop in the northern city of Chieng Mai. NEA was also in charge for the planning of the entire installation and for technical supervision during construction.

Nam Dang is a very remote hill station, at 1'400 m altitude, about 120 km northwest of Chieng Mail The station is situated right in the heart of the water shed area and has a negligible impact on the environment, since it is integrated into the reforestation program. The 100 kW power plant, of which powerhouse and penstock are visible in fig. 66, will be supplying electricity to three forestry stations and to a village inhabited by resettled hilltribes. A high-tension transmission line of 11 kV will be necessary for this purpose and will also make supply to other villages possible

There is a fundamental difference in this project, as compared to most hydropower schemes in Nepal, in the existence of an access road. This, naturally, reduces transportation and other costs considerably. Earthwork, for instance, was done by bulldozer at marginal cost, since this machine was engaged nearby in the construction and maintenance of a service road for reforestation.

a) Technical Details

SPECIFICATIONS :

- Installed capacity:

 

120 kVA

- Design discharge:

 

130 l/s

- Head:

gross:

79 m

 

net:

70 m

- Canal: open, trapezoidal, cement-mortar lined, length:

 

1'400 m

- Penstock:

diameter:

450/200 mm

 

length:

224 m

- Turbines:

   

2, Cross-Flow type

   

NEA design, runner

   

Ø :

 

400 mm

output:

 

62 kw/unit

- Step-up transmission: chain drive (triplex, 5/8") ratio:

 

1 : 2

- Alternator: 2, 3-phase, 1500 PRM

   

(50 Hz), self-excited, synchronous, brushless, italian-made: ANSALDO

   

voltage:

 

380/220 V

- Speed control: Oil-pressure, mechanical governor, JAHNS, AA2

   

(2 sets) speed:

 

900 RPM

capacity:

 

45 mkg

- H.T. transmission:

length:

18 km

 

voltage:

11 kV

The civil engineering structures are of a conventional type in terms of the material used, e.g. mostly cement concrete structures, the reason being that cement is easily available and transportation is no problem. Compared to the situation in Salleri/Chialsa, cement costs about seven times less in the Nam Dang project.

The intake is built with a weir-type barrage of about 1 meter height, across the river at the site of a natural pool, with a box-type sedimentation tank and inlet visible on the right in fig. 67. For this structure, about 200 m³ of concrete were used. The canal is fully lined and comprises several sections with closed conduits made from concrete pipe, to prevent side gullies from filling those sections with sediment. The forebay, at which the head-race canal ends, is again a concrete structure, perhaps a bit oversized, with a perpendicular overflow weir and a bottom flush-gate for flushing out sediment (refer to fig. 68). The trashrack, divided into two parts, is arranged vertically in the submerged part and sloping above the water level. As may be seen from fig. 65, the penstock, in rolled steel sheet/welded construction, is above ground on concrete supports with a number of anchor blocks that are larger than strictly necessary. The same may be said of the power-house, which is a piece of architecture in itself.

All civil construction work is done very neatly, somewhat more elaborate than strictly necessary, perhaps due to the pilot character of the project and easy accessibility.

The two Cross-Flow turbines used are actually the prototypes of the NEA design with a runner diameter of 400 mm and a nozzle width of 50 mm. The material used for the runner blades is stainless steel, as compared to common mild steel used by BYS in Nepal. The optimal turbine speed of 750 RPM necessitates a step-up transmission. For this, a chain-drive is used of Triplex, 5/8" pitch and 118 links configuration. Sprocket and pinion are made locally from steel plate.

For speed control, a flow-control governor of conventional type is used. This governor, connected with a flat belt to the turbine shaft (refer to fig. 69), is of the oil-pressure, flyweight variety, and imported from Europe. This item is rather costly and constitutes near about 40 % of total equipment cost (excl. penstock). As is usual, the governor requires also a flywheel that was cast in steel in the country and has a diameter of 750 mm and an operating speed of 1'500 RPM.

Fig. 70 is a detail of the Cross-Flow turbine, with one main bearing, the inlet part with gate-operating lever, and a part of the governor connecting-rod visible. The two sets of the installation are identical in all details and will be switched in parallel into a common network with a transmission voltage of 11 kV.

b) Investment Costs

For a comparison of costs with other installations described, it should be noted that the main difference is in a higher head which is generally cheaper to develop on a cost per unit basis. Further, construction materials and transportation have lower costs in Thailand, perhaps compensated to a degree by more elaborate construction. Also, in the case of Nam Dang, the cost of earthwork is not included since this was done by the Forest Department itself. In all three examples, design and engineering studies were not accounted for fully.


Fig. 71: Cost Breakdown of Nam Dang Project, Thailand

Source: All information pertaining to Nam Dang by courtesy of NEA