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Mini & Micro Hydro Power

Though hydro power had been in use over a century, only in the last decade, there was a large growth in mini and micro hydro power in Asia. Several country level government programmes, technical assistance and support from donor organizations are the key reasons for the development of power plants.

The definition given to this plant varies from country to country. In general micro hydro is less than 100 kW capacity. Mini hydro ranges from above 100 kW to less than 10 MW. Pico hydro is a very small scale power generation up to 10 kW.

The advantage of small hydro power plants is their cost effectiveness and reliability of providing clean electricity. Small and micro hydro power systems can be installed in rivers or streams with little or no negative environmental impacts and most of the systems do not require a dam.

Micro hydro power generation is a good option for rural electrification and several such plants are in operation in developing countries serving rural communities. The electric power generation

   

potential is proportional to the height (head) of water, flow rate and hydraulic efficiency of the turbine. The efficiency of these hydro plants range from 60 to 80%. The efficiency of hydro power plants increases with the increase in size.

In general, the operating life of hydro power plants is much higher than the conventional power plants. It also requires considerably less labour for operation. There are several equipment suppliers in India and China supplying low cost mini and micro hydro plants. However, life cycle cost should be taken into account before buying the hydro power plant.

Small/mini-hydro plants of several MW on the other hand involve considerable investment, which should normally be based on reliable multi-annual water flow measurements and professional feasibility studies. The business model for running such a plant requires formal management & maintenance structures and must also be in line with the rules and regulations for electricity generation and distribution.

Pico-hydro plants for instance are mostly used at a household level. Because the pico-hydro technology is quite cheap and not particularly sophisticated, these plants are normally installed by local craftsmen on the basis of tacit knowledge and without a feasibility study. Most pico-hydro plants are maintained by household members and thus do not involve electricity fees. But still, the specific capital costs of this technology are much higher than for micro- or mini-hydro installations. Besides scale, the feasibility and specific cost of a SHP plant is determined by several basic design parameters such as:

Water supply should be sufficient throughout the year. Strong seasonal flow variations with strong peaks during the rainy season often        require heavy civil construction works to protect the installation from damage due to flooding
Low water flows during the dry season increase investment cost for off-grid applications because these require hybrid solutions involving        other sources of energy (e.g. diesel or solar)
It is an important design feature whether an SHP shall feed into the grid or operate off-grid. On-grid installations tend to make better use of       the available hydraulic resources than off-grid installations because the latter are normally designed for the minimum annual flow while the        former can make profitable use even with part-time hydraulic resources
High loads of sand and silt (in particular during the rainy season) reduce the life-time of turbines, valves and other mechanical equipment and        require special construction features, which increase investment and maintenance cost
SHP feasibility is constrained wherever water resources are scarce and used for competing purposes (e.g. for irrigation). This situation become        sensitive during dry season
Because of seasonal variations of flow and sand/silt loads vary significantly down the years, hydraulic measurements must not be one-off       exercises but should be multi-annual exercises (for larger installations covering at least five years). Average flow rates are not a information        for SHP design
The specific cost of an SHP turbine decreases with increase in water head. Low-head turbines are more voluminous than high-head turbines       and therefore relatively more expensive. In addition, low-head installations often involve more heavy civil construction works (dams), which        can lead to prohibitive costs
The distance between the powerhouse and the points of electricity use is of critical importance. Transmitting electricity over distances of more       than about 2 km involves stepping up transmission voltage (depending on distance and power). Transformers and other equipment required        lead to a significant increase in installation costs

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