Mini-micro hydel power stations

Article Index

Code No: TMS070 Price: 1050 Category: Energy: Generation


Summary  : The scope of present study has been limited to development of Mini and Micro hydel power generation systems, their technological status, and what is needed to upgrade technology.
It identifies reasons for slow growth of mini-micro hydel power stations, problems associated with cost reduction and identifies the appropriate technology with cost reduction and identifies the appropriate technology and its effective implementation in the most economical manner.


Year of Publication : 1993

Table Of Contents : 

  • Executive Summary
  • Mini-Micro Hydel-Definition and classification
  • Turbines
  • Governors & Load Controllers
  • Alternators
  • Technology available in India Vis-à-vis World’s scenario
  • Neighbouring countries (Their Efforts in Economising and results)
  • Technical and economic appraisal
  • Recommendation
  • Bibliography



i). The relationship and the importance of the selected subject of technology to the
broad one to which it belongs.

ii). The current status of the technology in the world and the country.

iii) Assessment of the technology and technology options available to India.

iv) The economic aspects of the technologies alongwith their feasibilities which
leads to the preferred option(s).

v) Impact of the preferred option by itself, its linkages to the broad area of
technology and spin-offs and

vi) Identification of agencies/groups/individuals and suggested action plan.


The hydro generation can be classified as large hydro power stations, small hydro power stations, mini hydro stations and micro hydro stations.

Scope of present study has been limited to development of mini and micro hydel power generation systems, their technological status, and what is needed to upgrade technology, identifying reasons for slow growth of mini-micro hydel power stations, and identification of appropriate technology and how to effectively implement it in most economical manner.


The preliminary literature survey was done from the published literature, i.e. books, periodicals, journals, reports of seminars/workshops etc. to assess present trend of technology on mini/micro hydel systems.

We have contacted various organizations, who are working on this subject. We have prepared a set of questionnaires and sent to these organizations, which include, department of power & Irrigation, Electricity Boards, R&D Organizations, Manufactures of mini/micro equipments, nodal agencies, and Engg. Colleges, etc., as per the list enclosed in Annexure.

Though we have sent questionnaires to State Electricity Boards, the response was not encouraging and they were found reluctant to give required details. We have even deputed our persons for personal discussions to collect the details.

The response from Indian manufacturers was also lukewarm and the complete information was not furnished by them inspite of repeated reminders & personal contacts.
We have also collected information from United Nations and other nearby countries about the developments of mini/micro hydel systems (MMH).                                                                                                                                          Back

After collecting all the data/details by way of literature, survey, replies to our questionnaire & personal interviews, the information was examined, synthesized and critically analyzed with respect to the Indian scenario. We have also discussed the preliminary findings/analysis with the experts, prior to finalizing the draft report.

Chapter I of the report contains details of the present energy scenario, requirement of energy region wise, demand projection by the end of the Five Year Plans upto yea 2010, tables on installed capacity and peak availability, peak load year wise, general assessment of the hydro power potential and to prove the necessity of increasing the generation of energy and harness the renewable energy sources so far which have not been properly utilized and providing a better living conditions to the population of remote areas.

The Chapter also contains a brief introduction of the historical perspective in India and a little information on international scene, use of energy from Micro Hydro Project. it also provides reference of use of water energy for generation of mechanical power for industrial application. References of some of the earliest hydro electric stations of 19th Century, India’s power scenario in 1947, it also covers explanations of MMH power as an appropriate energy source as it can reduce consumption of products, petroleum based fules that are frequently imported at high expense and efforts, while Hydro energy is virtually inflation proof. Even if today the MMH pow3er seems to be very costly but due to minimum operation cost and with year of use, it becomes cheaper and technologies get proven and it has a chance of continuous improvement. MMH power is a less complex technology, which in turn is both less expensive and easily understood.

Also it discusses various social benefits available from the development of MMH power particularly to villagers or tribles who are far from town and modern civilizations and are not having resources of their own to get the benefits. MMH power resources will permit the use of energy by tribles and villagers, and their dependence on fuel wood which they consider to be free but is also declining the forest cover and ultimately affects the environment. In comparison to large hydro power schemes where by large body of water behind a dam can have a variety of adverse impacts on the surrounding areas. Lots of objections are being pit forward by social service organisation now a day. Completing a large hydro power scheme in between empowers them for rural electrification by MMH power which is a more socially acceptable technology.

Chapter I also deals with the use of MMH power on canal-falls which continuously goes down the level and a slow gradient is always available for generation f some energy and a cascade type system of generating power after each km could be planned it also discusses various obstacles to viable MMH power schemes. Some of which costs high but these costs are more due to the over sophistication of equipment and its control and this over sophisticated also lead to the increase cost of operation and by requiring highly skilled technical manpower and infrastructural appropriate for such manpower.

Chapter 2 briefly describes the main components of a MHP station, like civil structure work, dam intake works conduit conduction system, a surge tank, penstock, power house, turbine, tail-race speed regulator, generator etc. It also covers various classifications used in MMH power stations according to power capacity in various countries. It also discusses the various technological concepts used in classifying the MMH power stations. And covers the methods of conceptually design and standardization of procedures to be adopted for preliminary design of MMH power schemes to ways to carry out reversibility analysis and design procedure to be adopted for screening and optimizing, eliminate designs of mini micro hydro schemes, procedures for standardization of designs for prospective mini micro hydro plant, flow chart for final design, specifications and capital cost estimates for evaluating viability of prospective schemes.

The Chapter also describes appropriate civil works design for MMH power scheme so as to keep the cost of the MMH within a controlled limitation. The various civil works involved like diversion of intake distilling chamber, water conductor system, forebay reservoir surge tanks. Pan stock intake etc. are described and use of minimum structure have been suggested to eliminate the MMH becoming a large plant.

The Chapter 3 deals with the various equipment used for construction of the MMH plant like various types of turbines, limitations of each turbine. Advantages and disadvantages of each turbine at different discharge head and other environmental conditions which are likely to affect selection of the turbine. Each turbine description will briefly help the study and act as a ready reckoner for choosing various turbines for the selection for particular MMH power stations. The other mechanical devices which could be used either as turbine or for direct conversion of energy from water fall to mechanical energy and its use in industry are also described, like water wheels and use of centrifugal pumps as turbine, as it is well-known that both centrifugal pumps and hydraulic turbines follow the same affinity laws. One method for reducing the cost of a hydropower installation is to use pumps in reverse direction as turbines and the same is gaining popularity. In this regard, centrifugal pumps offer the best and ready answer to meet the requirements of water turbines for small micro hydro power projects. It has been observed that much time can be saved in the manufacturing, if we do not try to duplicate work that has already done by others.

There are some other turbines which have been briefly mentioned which have also been used for using the large power of water like in stream or water-current turbine and Schneider engine for low-head application. Marine thrusters which can be used at coastal areas which are use in California with 60-70% efficiency and various coupling made for joining turbine to generators.                                                                                                                                                         Back

The Chapter 4 covers various types of governors and load controllers used for governing the speed of the turbine, and act as speed sensitive servomechanism. Its function is to restore the speed by exciting the flow of water to the turbine to suite the new conditions. Two factors influence the governing of water turbines when compared with other prime movers. Firstly, hydraulic and frictional loads which have to be overcome are much higher, requiring the use of oil operated servomotors with high energy potential. Secondly the water column associated with the turbine has considerable inertia and changes in guide-vane opening (which results in changes of water velocity) leading to variations in pressure across the turbine runner.
Governing is required when electricity is generated by a synchronous generator at an isolated power plant. Its frequency is determined by the speed of the generator and the number of poles. If this speed increases or decreases, the frequency generated increase or decreases proportionately in more competitive systems the governors sense unit speed and adjust water flow through the turbine to obtain the desired speed through mechanical or electronic device. Therefore various types of governors and combination of the systems for various types of turbines have been diagrammatically explained.

Similarly the load controller is an electronic device that maintains a constant electric load on a generator in spite of change in user load there by promoting the use of turbine with low flow regulator devices. The principal advantage of load controller is that over all system becomes simpler and less costly. It not only eliminates the need for intricate governor and actuating mechanism but it allows design of the turbine to be simplified. A less sophisticated system increases the chances for long term viability and reduces equipment cost considerably for plants in the micro-hydropower plant. If electronic components fail in the field, they probably cannot be repaired on the spot, however, a well-designed unit is composed of separate printed circuit boards that can be replaced easily with soar boards kept for that purpose.

The Chapter also describes low cost load control for head men made canals. This has been taken specifically as we have very large canal system of about 3,000 km. and many more systems are under plan. There is a possibility of using the canal heads for generation of some power at economic rates as that total canal system at each distance of one or two km could be utilized for the generation of energy. In some cases we have lift canal system used for lifting the water to certain height and finally the water goes through gradient. Part of energy used for lifting the water could be regenerated at different locations during the course of canal. Therefore, to establish such micro energy system it is essential that cost of generation and total investment should be within the limit and feasible for authorities to sanction them such systems can only function and can be financed when feasibility looks good therefore, technology which helps reduction of the cost are very important. In this context neighboring countries experience and their research finds use in the development good for 50kW schemes. Blade angle control and use of by-pass techniques have been described for cost control purposes.


Chapter 5 describes various alternators which are to be coupled with the turbine to convert mechanical energy and to electrical energy. Synchronous alternators have been the principal electric power source in utility system ever since A.C. current became preferred from of power supply. Synchronous alternators have undergone an impressive evaluation in terms of creating controlling methods and parameters but in their basic structure they have remained the same as they were first introduced.

Induction generators exhibit different dynamic characterstics which can affect the dominant type of stability problems i.e. break up of net and induction of power supply. Induction generators are incapable for controlling voltage. In this chapter both types of generators, advantages disadvantages and comparisons have been discussed and as a result, relevance of induction generators for MMH station have been presented. Use of induction generator with turbine eliminates the requirements of governors, to induction generatotrs run with a wide range of rotor speeds over synchronous speed depending upon the power demand on the unit. The variation in speed can be simply obtained by regulating the turbine gate opening which could be done either manually or automatically by remote control.

Induction generator has an advantage that it requires no excitor in governing mechanism and no synchrounous equipment. This results in saving of up to 20% in the cost of electric plant. Moreover, with small and variable amounts of water, which does not justify the erection of a normal power station, it is simple enough to arrage for a water wheel to drive an induction machine having a cage rotor. This shows why induction generators could be used for micro schemes where cost reduction is more important.                                                                                                                                                   Back

Chapter 6 describes world technology scenario and technology available in India. The various manufactures, suppliers their capability to supply equipment for MMH plants is very important factor to note at all of them have collaboration with one or other leading manufactures in Europe or U.S.A. and therefore are having sufficient technical backup as and when needed most of the collaborations also envisage sharing of R & D experiences and also have some R & D set up to come up with solutions to problems of smaller dimensions. They all have design engineering facilities but prefer to supply one out of standard design available as the detailed design of standard sizes and facilities of manufacture for normal size are available and would save time and cost of equipment. Some of the manufacturer/supplier is described here.

We have also gone through the reply submitted by them against our questionnaire and their suggestions for cost reduction are being recorded here. Most of them are of the view that reasons for slow growth of new MMH power stations are financial and bureaucratic hurdles. In their opinion, growth is achieved by standardization of machines and by soft loan/subsidy from Govt. of India. Subsidy could be considered as a part of social up liftmen of that particular village. They have also informed the cost could be reduced with use of cheaper materials which are highly developed, like use of aluminium plant instead of SS fore runner. Some of them have indicated that new technology like use of vertical type turbine compared to S type turbine could reduce manpower to one operator per shift and thereby reduction of cost and civil works and operation and maintenance cost in due course of time so as to make the MMH power feasible. Use of hydro pulser at MMH system could be another way of the cost reduction although hydro pulser is based on old technology of hydro ram. It uses devices which can raise the water upto 15 times the original height of the water fall. The hydro pulser does not need any external energy but works continuously and automatically. It employs the force generated by the moment of water fall and inertia of the machine. It works without electricity or fuel and requires very little maintenance and can be used for generation of small current by connecting a water turbine and an ordinary alternator or a centrifugal pump in a reverse manner. The falls from 2-10 m. will be able supply installation capable of producing 50-100 k W of electricity. Therefore, these system could be promoted for micro generation system as they have a negligible operating cost.

The Chapter 7 describes experience of neighboring countries where enormous development has taken place in development of micro hydel power. We have described in detail the experience of China where. Full utilization of the scattered small hydro Power potential in combination with water utilization for other purposes is ensured by constructing power stations to meet local electricity demand. There are many stations, each covering certain areas, scattered throughout the country. A local network is formed and connected to the government run grid. This should meet demand in rural areas for electricity and promote a quicker development of agriculture with less government investment.

MMH production costs are rather low, amounting to approximately 3-4 fen per kWH whereas the production cost of the small thermal cost or diesel-fuel power stations is about 10 ten or more per kWh.

China’s experience shows how the standardization of equipment, cost reduction technology in works handing over the running of the MMH power to the local community, complete control of the local community over the use of power for industrial development return on investment to re-invested in industrial and community development. The cost reduction for water resistance devices to be used in place of surge shaft, use of third harmonic voltage excitation system, cost of which is 50% of the older system requires less maintenance and repair work in comparison with SCR exitor which often requires mechanical processing and dealing with the commentator erosion. In China following the rapid development of MMH stations, small power networks have arisen in many places helping to improve the reliably of power supply. Usually the installed capacity of the grid on a county level (district level) ranges upto 10000 kws. Their experience is to improve the reliability of power supply, the establishment of a small local grid is necessary. A small local grid must be equipped with several units in order to bear the heaviest load to stabilize the running of the grid should have a sufficient installed capacity and enough spare capacity.

Similarly the Pakistan experience can also be utilized as they have worked with determination to keep appropriate technology in MMH utilization of local material association of the local people, design suited to local condition and living, implementation, management, operation and maintenance to communicate because the remotness of villages their small population and lack of income generated enterprises combined to make rural electrification by grid extension uneconomical. Hey also developed new designs for the civil work and new approach in implementation is adopted in designs that emphasis the use of local rather than imported materials and manual labour.

Villagers designated by the community operate and maintain the plant thus envolving local operators with technical assistance for technical staff, learning various tasks from various appropriate operations because the plant system does not operate a governor. Principal task of operator is to manually operate the light around the village. The operator therefore, is not required to adjust the water turbine continuously to keep pace with changes of electrical load.

Nepal is another country where the government has undertaken small-hydropower programme. Faced with a difficult situation few roads, scattered but dense population in certain parts of the country, rugged terrain, major deforestation, and not indigenous oil reserves, the Nepalese see decentralized hydropower as a promising source of energy. Efforts are made by Balaju Yantra Shaala to localize the small water power installations. This private sector approach to the implementation of a micro-hydro power program illustrates an encouraging alternative to the more costly, bureaucratic governmental approach.

BYS, BTI two prominent organization of Nepal are involved in developing approapriate technology, have emphasized the use of only indigenous equipment, without importing, which could be easier. Although it took them sometime but they were able to successfully fabricate and install number of MMH power stations and over the years have improved their expertise for doing so. All their efforts have been explained in this chapter and they have also emphasized the use of direct mechanical energy for running the rice miller flour mills also emphasized the use of direct mechanical energy for running the rice miller flour mills the processing machinery would be properly integrated into the overall project designs. They also lowered the turbine levels and put the other industrial machinery at a higher floor thus avoiding waiting of the mills floors. They also utilize the mechanical generator for drying of agricultural products using hydro power instead of generating electricity and then to use it to force air passd electrical heaters thus avoiding the costly in between equipments.                                                    Back

Chapter 8 deals with technical and economic appraisal of the MMH and various attempts for cost reduction to make the MMH viable alternative have been discussed. The appropriate technology should be used has laid down a necessity method to arrive at appropriate technology for this. Report mentions that value engineering and value analysis technology are the alternative for judging the appropriateness of technologies unit wise and equipment wise as eliminates the hidden cost after comparing the various alternatives in a metrix system. Therefore, some marks could also be assigned for the social related advantages and they also become accountable for feasibility of a MMH power stations. We have also tried to analyze one MW mini hydro plant and CBS has been done on the basis of construction of unit wise plan for kW generation capacity as made may various load factors and price of energy to be Rs.1/- in one case and Rs.1.60/- in another case. This CBA does not care of various social impacts which are addressed to the development of MMH power stations. However the net present value area indicative of the feasibility of a project, this may not be necessarily the binding principle for desisting about a Mini-micro Hydel Power Stations, overriding principle would find out ways and means. Therefore, we briefly describe the advantages of generation by MMH power stations below:

If properly used in a good site, small scale hydroelectric generation has many advantages over most of the conventional means of electrical generation like.

Cost – Hydro Plants usually cost more to build than plants that make electricity by burning coal, oil, or natural gas. But once they are built, cost to run them is free, while thermal generating plants must pay for their fuel. The hydro plants are also inflation-proof, while the cost of fuel for other plants has increased enormously. Hydro plants also last longer than most other kinds of generating plants.

Rapid construction – Smaller projects such as mini-hydro plants can be built more quickly if properly planned providing electricity long before large hydro plant or most kinds of fule-burning generators. This means faster development, less interest paid on construction loans, and quicker benefits to the country. There is also much less risk of long delays in construction with cost over runs, and a reduced risk of ordering an expensive plant far in advance, then binding out that it isn’t needed after all.

Local self-sufficiency-As a renewable resource, hydropower does not depend on imported oil, coal, or uranium; and it is much less dependent on foreign experts and technology than other kind of electric generation. mini-hydro plants can promote self-sufficiency within a country-if necessary, a town, a cooperative, or an industry can build its own electric plant, without waiting for a national electrification, project, and without depending on fuel supplied which may be unreliable and expensive to get.

Appropriate technology-Compared to other means of generating electricity Mini-hydro is labour intensive and suited to operation by local people. Although the initial cost of the plant can quite high, a good part of this cost comes from on-site construction, which cn provide jobs and training to local resident. Most other kinds of generating plants require much more skilled labour, which must be imported at great expense from long distances.

Beneficial side-Effects-Small-hydro-electric development is often accompanied by other beneficial developments such as irrigation, water-supply and sanitation, fishing and fish faming. The value of the electric power generated can often make the difference between a practical, profitable project and one which is too expensive.

This Chapter also covers how the hidden cost which is to be eliminated and using some of case studies carried out earlier by other authors obtained from HPMC record. Various appropriate technologies using local materials and reasonable site works have also been described.

Finally report also mentiones that a computer program should be developed so as to aid development of an optimal design package for Micro Hydro System. Package should contain use of local data and have user friendly feature and should be able to give various alternatives of designs appropriate to the site conditions.                                                                  Back


The chapter on recommendation covers various suggestions which will help in development of MMH power stations and use of technologies some of them are described below:

1. Development of MMH has to be treated as a national measure to provide electricity to people residing to remove areas.

2. Being non polluting renewable source of energy and generating from MMH power stations will meet them less of obstacles.

3. Nation wise assessment should be carried out separately by all states.

4. All canals should be used to generate some power by using low cost equipment at a distance of 1-2 km.

5. All canals to constructed in future should have a provision for MMH power station i.e. instead of continuous drop, a sudden fall at 1-2 km distance would be useful so that these can be harnessed in future.

6. All Central/State organisations, PWD, R&D should help in identifying Micro schemes.

7. All the MMH power stations may have irrigation plant, cost of irrigation development should not be considered as a plant cost for feasibility of a MMH power stations.

8. On canal falls exploitation should be based on entire flow even if they are not continous through out the year.

9. Local people should be involved in implementation and operation of the MMH power stations.

10. Private entrepreneurs should be encouraged to take over construction and running of MINi-Micro Hydel Power Stations.

11. Plants under 100kW should not be Govt. owned to cut down operating cost. They should be maintained by village communities, small businessmen or millers.

12. Plants under one MW should be run by utility district communities but not by the State Government.

13. MMH power stations should not be mini model of large hydro power station.

14. Civil works to be reduced to where minimum use of induction generator has to be promoted.

15. Use of centrifugal pumps as generator should be promoted.

16. The turbine the centre place of a MMH power stations and other components are to be manufactured in simple mechanical work job. Only in this way technical sustainability can be achieved.

17. MMH power stations are to be used in manner to keep a high load factor during the day for agro processing or use direct power which is easier and cheaper and mechanical for lightning night time.

18. Integrated approach for more sustainable development through MMH power stations is needed. This will change:

a. The added value of agro processing industries in the village, income of the village rises and small trade cycle will be created.

b. Village life, light, radio, television will be more active and more attractive reducing the migration and load of cities.

c. Villagers devoting more time in agricultural and productive activity.

19. Creation of research and development scheme oriented towards program objectives of improving the rural condition of life through the increased use of available micro hydro power potential not only by lighting but a possible share of regularly produced components.


While carrying out the study, we have drawn upon the experienced and advise of institutions and individuals who are actively involved in the field of MINI / MICRO HYDEL SYSTEMS. There are so many persons and organizations who have directly or indirectly contributed in the preparation of this Report that it is not possible to acknowledge their contributions individually.