By David Sear
Presenting a snapshot of the hydropower sector in India. The article starts with basic facts and figures indicating the current size and also the potential for growth in hydropower. The second section touches on some of the valve designs often found in hydropower facilities.
At over 1,559 TWh (2019 figure), it is no surprise to learn that India is well into the top five of the largest electricity-generating countries in the world. Whilst the bulk of India’s power plants still rely on the traditional coal there is however a sizable and growing renewables sector, in which hydropower is currently the main actor. That position may change given the emphasis being placed on solar but hydropower is and will remain very much in the picture thanks to the multiple projects already at various stages, from tentative planning right through to commissioning.
To give a rough frame of reference, India’s current total electricity generation capacity is around the 410GW mark. Of that total figure, almost one eighth, or some 50GW, is derived from hydropower. In turn, hydropower can be further broken down into three main sub categories, namely dams, run-of-river and pumped energy storage.
Dams
Dams are probably the most widely recognized forms of hydropower, comprising a dam across a river to create an artificial lake. Run-of-river facili-ties are often constructed in areas where flooding an area is considered undesirable. Pump energy storage works almost as a dam in reverse: during periods of oversupply, excess electricity can be used to pump water upstream for containment behind a dam. Later, when more electricity is required, that water is released to power a turbine. Currently, dams account for the lion’s share of all electricity generated by hydropower in India, with output indicated to be around 70 per cent. Run-of-river plants make up perhaps a further 20 per cent of the total, with pumped energy storage supplying 10 per cent.
Energy mix
However, it should be noted that this balance does seem to be slowly shifting. Figures for the number of hydropower projects both under construction and in the planning stage indicate that whilst dams will probably remain the major electrical source, the combined run-of-river and pumped energy storage technologies could account for half of all additional hydropower generation capacity in the near to mid-term. Returning to the broader perspective, if current projections for power plants, solar parks, hydropower units, etc, come to fruition, then hydropower may well jump from 12 to 25 per cent of India’s total energy mix. That is surely good news for all, as hydropower provides a reliable and stable electricity baseload and moreover accounts for almost negligible carbon releases once operational.
Valves for hydropower plants
As might be expected, valves can be found in various locations in a typical hydropower station. For example, on penstocks to open, close and control the flow of water, upstream of the turbine to connect or shut down the supply of water; and at other locations to change the direction of flow or to regulate the pressure.
Commonly used valve designs include gate, butterfly and spherical valves. The latter offer minimum head loss due to the completely free through-flow and are often used as high-pressure turbine inlet and pump valves. Butterfly valves are often modelled to ensure minimum flow head loss coefficient. Other types that may be encountered include plunger valves and fixed cone valves. The type of valve chosen depends on the application, such valves may operate regularly to moderate flow, others will only be used to shut off and isolate equipment for maintenance, whilst emergency valves may have to meet requirements for very fast closing.
Hydropower plants can require some very large valves. One valve manufacturer records installing cone valves up to 2.2 metres in diameter, spherical valves up to 3.3 metres, and butterfly valves up to 6 metres! Perhaps more surprising are the pressures involved: the same manufacturer lists design pressures of 64 bar for both cone and butterfly valves, and a massive 200 bar for spherical valves.
About this Featured Story
This Featured Story is an article from our Valve World Magazine August 2021 issue. To read other featured stories and many more articles, subscribe to our print magazine.
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