Hydropower generation is one of the few environmentally benign options. It does not involve fuel cost if deploying mature technology, which is characterised by spectacular operational efficiency. This makes hydropower generation cost effective.
But the country?s hydropower generation programme has not made much headway. It contributes only a quarter of the total power generation capacity. The 11th Plan envisaged a capacity addition of 78,577 mw from conventional sources, which includes 16,553 mw from large hydro projects and 1,400 mw from small ones. Small hydro projects are those with a capacity of up to 25 mw.
One of the main reasons for the slow capacity expansion of large hydro projects is that it leads to human displacement, deforestation and big dams, and if not constructed with due care, can pose a security threat. Keeping in view the problems associated with large hydro projects, the government plans to promote small hydropower projects under the Union ministry for new & renewable energy. Such projects also help decentralise power generation and distribution.
Hydropower generation depends on the availability of surface water, which ultimately depends upon rainfall. Climate change has posed a problem of erratic rainfall. It has also become a threat, signalling the gradual drying up of glaciers, which feed perennial rivers. Small hydro projects would also lead to the diversion of water from agriculture, drinking and household uses in rural areas.
According to the government, the potential of small hydro projects is estimated at 14,294 mw, but their cumulative power generation up to December 2007 was only 2,045 mw. Across the country, 5,403 potential sites for small hydro projects have been identified, of which 607 have seen installations generating 2,013 mw. Another 216 projects with a capacity of 612 mw are under implementation.
The Alternate Hydro Energy Centre (AHEC), in collaboration with the UK?s Centre of Ecology & Hydrology, has developed software to assess the hydrology of potential project sites. A resource assessment for all renewable energy sources, including small hydro projects, and mapping of potential sites on the GIS platform are underway. Models have been developed that take into account regional flow duration curves, geological and seismological data, and vegetation cover for identification of potential sites.
The GIS technique is used to extract information on natural drops available in the river system. The water availability at these sites is then determined using a distributed rainfall runoff model called a soil & water assessment tool. The model uses terrain features, land use and soil data along with rainfall and other meteorological parameters to generate the flow time series. This model has been successfully tested on the Beas river basin and is being applied to other basins.
AHEC and IIT Roorkee are assessing standards, guidelines and manuals on hydropower developed by international and national bodies. At present, back-ended subsidy for small hydro projects is released on the basis of verification against the standards set by the International Electrotechnical Commission. AHEC and IIT Roorkee test the projects commissioned for their performance.
Some 19 states have announced policies for setting up commercial small hydro projects through private sector participation. The facilities include wheeling of power generated, banking, and power buyback for third-party sale. India has a strong base for the manufacture of small hydro project equipment. Indian manufacturers have international tie-ups and technical collaborations to produce a range of turbines, generators and control equipment. Water wheels have been traditionally used in the Himalayan region for rice hulling, milling of grain and for other mechanical applications. Improved versions of water wheels have been developed for power generation of 3-5 mw.
The equipment used in SHPs is now more efficient, reliable and automatic. Electronic governors have replaced the mechanical systems, and digital controls have replaced analogue ones so that projects are completely azutomated. There is now the need to improve civil design and hydraulic structures. Attention is being paid to the development of efficient desilting structures, self-cleaning water intakes and trash racks.