^ Rongnichu HPP: FLOVEL with its sister concern company TFV has recently supplied two spherical
valves (1,650 mm, PN 50) to the Rongnichu Hydro Power Project, Sikkim, India. These spherical
valves have been fitted with double movable metallic seals
Article By David Sear
Hydropower in India
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 are probably the most widely recognized forms of hydropower, comprising a dam across a river to create an artificial lake. Run-of-river facilities 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%. Run-ofriver plants make up perhaps a further 20% of the total, with pumped energy storage supplying 10%. 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% 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
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 thanks to the completely free through-flow and are often used as highpressure 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. Operation can be manual (handwheel or via a gearing system), electric, pneumatic or hydraulic. Counterweights may also be fitted to valves to assist in situations where fast closing is required. One manufacturer reports that valves can also be operated using water pressure upstream of the valve
And no surprises in saying that hydropower plants can require some very large valves indeed. 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.
Despite the disruption caused by the Covid-19 pandemic, the International Hydropower Association’s 2021 Status Report shows that global installed hydropower capacity rose by 1.6 per cent to 1,330 gigawatts (GW) over the past year.
To limit dangerous global warming and achieve net zero by 2050, the International Energy Agency (IEA) however says the water power sector will need to double in size to 2,600 GW. This equates to building the same amount of capacity in the next 30 years as was built in the last 100 years. “At the present rate of hydropower development, the global energy pathway to net zero emissions will not be realised,” warn IHA President Roger Gill and IHA Chief Executive Eddie Rich in the report’s foreword. “This is a wake-up call for policy-makers, hydropower developers and project financiers and provides clarity for the public."
“Investment in sustainably developed and responsibly operated hydropower is essential to support the massive expansion of variable renewables like wind and solar. However annual growth rates of 1.5 to 2 per cent cannot meet the doubling of installed capacity proposed by the International Energy Agency to achieve net zero by 2050.”
According to the report, the Covid-19 crisis has further underlined how the power system flexibility provided by hydropower is now a prerequisite for the clean energy transition. Hydropower’s critical role was illustrated by a recent near blackout incident in Europe in January 2021.Despite the slump in demand for fossil fuels experienced during 2020, hydropower generated a record 4,370 terawatt hours (TWh) of clean electricity – up from the previous record of 4,306 TWh in 2019. This is roughly equivalent to the entire annual electricity consumption of the United States.
During 2020, hydropower projects totalling 21 GW were put into operation, up on 2019’s 15.6 GW. Nearly two-thirds of this growth came from China, which saw 13.8 GW of new capacity. Among other countries that added new capacity, only Turkey (2.5 GW) contributed more than 1 GW.