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Micro Hydro Power Plants in India
Essay Contents:
- Essay on the Introduction to Micro-Hydro Power Plants in India
- Essay on the Small Hydel Projects in India
- Essay on the River Current Energy
- Essay on the Poncelet Water Wheel
- Essay on the Darrieus Turbine Rotor
- Essay on the Installation of Micro Hydro Power Plants
- Essay on the Auxiliaries of Micro Hydro Power Plants
- Essay on the Conclusion to the Micro Hydro Power Plants
Essay # 1. Introduction to Micro-Hydro Power Plants in India:
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India has made great strides in industrialisation during post-independence years. This has brought prosperity to a selected few and created concentrated centres of employment near the industrial complexes and big cities where economic activities have flourished. The material and energy resources have been diverted to feed these industrial and commercial ‘gluttons’.
The high technology industry could not penetrate the traditionally agricultural rural and remote areas where nearly 78% of India’s population lives. The rural population felt neglected and many of them are flocking to the new economy centres in search of their livelihood. The continuous migration of population and uneven distribution of wealth, material and energy resources have created many social and political problems which can lead to very serious consequences, if not further checked.
The solution of the problem lies in concerted efforts for the development, welfare and prosperity of the rural areas which is turn depend upon the availability of cheap and abundant energy for domestic cooking, heating and lighting, community development, irrigation water, mechanised agriculture and small industries.
Transportation of commercial fuels like coal, diesel and patrol over long distances to remote and rural areas is very difficult and transmission and distribution of electricity through power grid to far flung areas are prohibitively expensive. The farmers and craftsmen are not in a position to pay for high costs of energy, thus small scale industries in these areas are reduced and there are limited irrigation possibilities in agriculture.
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The modern high technologies do not adopt to rural ecology an energy production technique based on renewable and appropriate technology which can be taken care by trained local people for its operation and maintenance problems is ideally suited. Only appropriate technology involving local resources, manpower and raw materials and environment can ensure environmental harmony and sustainability of the development. The utilisation of energy in flowing water through micro hydro schemes is a good example of appropriate technology for rural development.
Essay # 2. Small Hydel Projects in India:
Hydropower, available free of cost in the form of flowing water, is an important, pollution free renewable source of energy. The large potential of hydro-energy available from flowing water in the rivers and irrigation canals, however, still remains untapped, since generating power on a small scale from low and ultra-low head drops of 3 to 20 metres has not been an economic proposition because of the high civil and equipment costs as well as high operating cost to be incurred per unit of power generated. The situation is further deteriorated by very low load factors in rural areas.
Chinese have developed 1200 MW of power by small hydel projects by creating water heads of about 5m along the rivers. It is estimated that 5000 MW capacity of power can be created in India with the help of small hydro turbines of 200 kW to 1000 kW capacity each. M/s. Jyoti Limited, Baroda have the necessary know-how and capacity to manufacture these small hydro turbines, see Table P. 101.
There are also other organisations showing interest in the manufacture of such small sets. Bharat Heavy Electricals Limited also has the necessary know-how which can be passed on to some ancillary unit for quick manufacture of small hydro turbines without disturbing their main manufacturing plan for large sets.
Due to civil costs of dams, water conduits and diversion channels, independent small hydel projects become very costly. It may cost Rs. 18000 per kW installed. Such projects should be planned on the basis of multiple purpose use of water resources such as irrigation and power generation.
Even though these schemes are costlier when compared with the cost of unit power generation from major hydel projects, these are encouraging keeping long term energy availability in view. Also hydropower is renewable in nature, once built, there is built-in protection against inflation of cost, water is available essentially free, it can be instantaneously switched on, and it need not run continuously.
According to the size of hydro-turbine, the small hydel projects may be classified as:
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Micro Hydel Projects: 50 to 100 kW
Mini Hydel Projects: 100 to 1000 kW
Small Hydel Projects: 2 MW to 15 MW.
Small hydel projects can be completed in four to five years, mini and micro projects in three years provided civil works of irrigation projects are already completed. Here water released for irrigation only is used and power is therefore, generated for 6 to 7 months a year.
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In Maharashtra, 130 schemes of various categories of small hydro projects of about 11000 kW capacities for a layout of Rs. 2000 millions have been planned. A separate circle has been created in UP State Electricity Board with headquarters at Nainital for small hydel projects. Sixteen micro hydel schemes are already functioning in eight hill districts of UP with total installed capacity of 7730 kW. Four schemes are under construction for a total cost of Rs. 3.37 crores. The total installed capacity after completion of these schemes will be 8830 kW. Other 32 schemes of 20,000 kW are in the pipeline.
Other hilly states are also going for small and micro hydel schemes in a big way.
Essay # 3. River Current Energy:
Western Ghats of Maharashtra and regions of Uttar Pradesh, Himachal Pradesh, Jammu & Kashmir, Sikkim and North Eastern States located in the Himalayas are suitable sites for small hydel projects where medium to high heads can be available. Equipment costs are low in the high head schemes.
As we come down the hills, the available head decreases and equipment costs go up. For example, the cost of one hydro set of horizontal tubular design of 3.2 kW capacities operating at a head of 3m maybe Rs. 1.28 lacs, i.e., Rs. 40,000 per kW installed. The civil costs are site-specific but taking 30% of equipment costs, the total installed cost will be a high value of Rs. 52,000 per kW installed.
Most of our rivers flow through flat terrains which can be harnessed to produce power much in excess of 5000 MW as estimated above. Chinese model is difficult to develop due to different topography in India. Special ‘zero’ head turbines operating on kinetic energy of flowing water should be developed to harness huge river current energy.
The civil costs or micro hydel power projects can be drastically cut by using floating type plants. There is no need of diversion channels, deep excavations and massive foundations. The floating plant consists of two floats with a vertical (or horizontal) runner in between, which rotates by the velocity of water. The capacity developed is a function of the size of the runner and cube of water current speed.
The rotational speed of runner is rather low and electric generator can be operated via a transmission gear. The floating plant moves up and down with water level and gives constant performance all the year round which is a big advantage over firmly installed water turbines especially during monsoons.
The current energy of flowing water which can be exploited by floating type power plant may be expressed as:
P = 1/2 AV3 E(kW)
where,
P = Power generated
A = Embrassing area of runner (m2)
V = Water current speed (m/s)
E = Efficiency of runner and depends upon the type of the runner and varies between 0.5 to 0.85.
Although hydraulic wheels will operate at low water velocities, it is unlikely to be an economic proposition in current speeds below 1 m/s (2 knots).
Essay # 4. Poncelet Water Wheel:
In ancient times, floating mills were used in Germany on large rivers such as the Rhine, the Weser and the Elbe to drive electric generators and machine tools. A vertical undershot water wheel consisting of a horizontal shaft and radial blades fixed to it, was fitted on the side of a barge which was either moored to the bank or firmly anchored in the stream. A smaller barge was used to support the other end of the shaft. The hulls of the barges were built with local materials. The efficiencies realised were very low, in the range of 20 to 30% because of bad geometry (straight radial blades).
Poncelet water wheel is an improvement on the straight blades of undershot water wheel, which has suitable curvature. Water strikes the vanes practically without shock (inlet vane angle 15°) and drives it by impulse. Water is discharged from the blades almost vertically downwards. The efficiencies achieved are 55 to 65%.
The main drawback of such machines is low power output for a given size and weight because at any instant only a small part of it is actually in the water being driven by the current while the rest of the machine is idle.
Essay # 5. Darrieus Turbine Rotor:
Darrieus turbine rotor is similar to modern vertical-axis turbine which was first introduced in France by G.J.M. Darrieus in 1920’s. Its configuration consists of four hydrofoil blades which rotate at much higher speed than the water current speed. The speed of rotation is primarily dependent upon the machine overall dimensions. It has relatively low starting torque. Because of simplicity of the blade design and because they are relatively thin blade fabrication costs are low. They require no pitch control for synchronous applications.
Two prototypes have been developed by Intermediate Technology Development Group, London and are shown in Fig. P.10.1 and P.10.2.
The blades can be made out of timber or fabricated from steel, ferro-cement or glass fibre. The expected performances from these models are plotted in Fig. P. 10.4.
Essay # 6. Installation of Micro Hydro Power Plants:
Floating type micro hydro power plants are suitable for use in situations where there is no ‘head’ of water available and are designed to extract kinetic energy from a river or canal current. Therefore appropriate sites are along the banks of large rivers or on irrigation canals.
As the energy flux depends upon the cube of water velocity, the latter must be as large as possible. The depth of water required for a 4m2 runner is at least 2.5m.
The Darrieus turbine rotor is a low speed machine. It is low solidity device which is completely submerged during operation and this, together with its high efficiency (above 50%), means that a rotor of moderate size and modest materials content can extract useful amounts of energy from current speeds as low as 1m/s (2 knots).
Irrigation canals are expected to be an important area of application for floating type micro hydro power plants. In a large canal, the turbine rotor could be mounted on a pontoon as in a river situation, whereas on a small canal it might be cheaper to mount the rotor on a bridge or beam over the canal. The power output from the rotor could be increased by shaping the canal banks to form a venturi to increase the water velocity through the rotor.
The mooring details and site requirements are shown in Fig. P.10.3 and P.10.5 respectively. The mooring cable arrangement protects the rotor against submerged or semi-submerged objects striking the blades.
The pontoon which carries the turbine, generator and the transmission system, can float on two rows of barges or oil drums under which wooden keels are affixed. The mooring cable can be adjusted with a winch to ensure sufficient angle of the keels to the current direction so that water side thrust on the keels keeps the pontoon at a distance from the bank.
Essay # 7. Auxiliaries of Micro Hydro Power Plants:
The rotational speed of Darrieus turbine is very low 13.5 rpm for vertical axis and 32 rpm for horizontal axis turbines as shown in Fig. P.10.1 & P.10.2. For Poncelet turbine, the peripheral velocity of runner is about half of water current speed. Therefore multi-stage belt drives or gear boxes are needed to increase the speed of the generator shaft to about 950 rpm.
Permanent magnet alternators or induction generators are preferred over synchronous generators. To reduce equipment costs, the conventional mechanical or hydro mechanical speed governor should be dispensed with. The intertia of rotor being small, there is a problem of instability m power supply quality.
The above problems can be solved by use of the flywheel which can ensure stable power supply and can shave-off power demand fluctuations. A flywheel designed for this purpose can be accelerated to extremely high speeds without any risk of breaking apart. It can be made from concentric rings of quartz fibre as windings, the rings being fitted over one another and close gaps filled with an elastic substance to keep the piles of the rims together.
The flywheel is coupled to a generator and enclosed in a sealed evacuated casing to reduce wind age losses. The device operates as a generator when power demand on the system grows, and as electric motor, when it is time to accumulate energy. According to some calculations, the cost of 1 kW will be less than that with pumped hydroelectric storage. A project has been described contemplating a 5m diameter flywheel of 1.96 MN weights that could be charged to 20 MWh. The operating speed is 3500 rpm.
The mechanical energy storage system as described above can fit into appropriate technology level suitable for rural environment. The load governors based on electronic circulatory or microprocessor technology may be able to solve the problem to some extent but may not be easily acceptable in rural areas because of higher levels of technology involved. Further, these load governors do not operate happily against unstable operation of turbine rotor.
Load governors invariably require an auxiliary load or another hybrid system to store surplus electric power generated by hydel power plant during low demand period. This is not always a good decision thermodynamically, as electrical energy is the highest form of energy and hybrid systems help to degrade the energy form and in addition there are heavy conversion losses.
Essay # 8. Conclusion to the Micro Hydro Power Plants:
Floating type micro hydro power plants can be a very attractive proposition to harness enormous amounts of hydro energy available as river current energy in the flat country side. Civil costs are reduced and cheap and reliable equipment can be developed for tapping the flow energy in the irrigation canals by constructing the banks into venture shapes. Research and development efforts are needed to develop efficient turbine rotors working on the principle of wind turbines or old time water wheels followed by intensive field trials.
The problem of stability and energy storage to improve load factors can be solved by the development of suitable flywheels. The development efforts must be constrained keeping in view the principles of appropriate technology suitable for harmonious development of rural areas involving local people, local materials and local resources.