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TN plans largest hydro project in Nilgiris by submerging several acres of forest

Though environmentalists feel this project will have deterimental effects, state government officials say that it does not have any other reliable hydro potential of this scale.

Published: 18th November 2019 10:07 PM  |   Last Updated: 19th November 2019 05:17 AM   |  A+A-

Cauvery

(File photo of Mettur dam| Express))

Express News Service

CHENNAI: Tamil Nadu government is planning to build its largest hydroelectricity and first Pumped Storage Project (PSP) in Nilgiris submerging hundreds of acres of forest land. Two reservoirs across Sillahalla and Kundah rivers are proposed to be built for the purpose.

Conceptualised at an estimated cost of Rs 4,200 crore by Tamil Nadu Generation and Distribution Corporation Limited (Tangedco), the Sillahalla Pumped Storage Hydro-electric Project Stage-1 will house four power plants with a combined capacity of 1,000 MW.

As per the official documents, accessed by Express, an upper dam across Sillahalla river and lower dam across Kundah river downstream of existing Kundah Palam dam will be built and interconnected by a tunnel to generate electricity for peak hours (6 hours daily) and recycle the water from lower to upper dam at the time of non-peak hours using reversible turbine/generator.

About 421 acres of land shall come under submergence. Additional land required for constructing dams, water conductor system, power house and other project appurtenances works out to 356 acres. The total land proposed to be acquired for the project is 777 acres, of which 445 acres is forest/government land and the remaining is private land. The construction would cause a permanent change to riverine system, the documents reveal.

However, Tangedco officials said the project site does not falls within any reserve forest or national park. "The impacts on flora and fauna on account of submergence of forest area will be assessed and appropriate management measures will be taken as a part of the Environment Impact Assessment (EIA) study."

As per the feasibility study conducted by WAPCOS Limited, a public sector enterprise under the aegis of the Union Ministry of Jal Shakti, the proposed project is likely to have negative environmental impacts, however, adverse impacts can be ameliorated to a large extent by implementing appropriate mitigation measures.

"Land requirement of 315 hectares is on lower side considering the size of the project of 1,000 MW. Tamil Nadu and Tangedco do not have reliable hydro potential of this scale. Hence, Sillahalla Pumped Storage is the only feasible alternative available with Tangedco. In view of mandatory large injection of renewables into the grid in near future, Tangedco needs advance planning to integrate it and Sillahalla
can be useful in this regard," study said.

Tangedco officials said both Sillahalla and Kundah are seasonal rivers and dry up or have little flow in non-monsoon or lean seasons. "The main storage for proposed scheme is upper reservoir. Once it is filled to the brim, the water will be recycled between the two reservoirs. A pumped-storage plant works much like a conventional hydroelectric station, except the same water can be used over and over again. In this process, there is no consumptive use of water. This is a proven and cost effective technology with high efficiency," an official privy to the project said and added that there was a precedence and current trend in favor of Pumped Storage projects. West Bengal has already constructed Purulia PSP (900 MW) and Turga PSP (1000 MW) is now under pre-construction.

Kundah Hydro Electric Complex in Nilgiris hills is already one of the biggest electricity generating schemes in Tamil Nadu with installed capacity of 585 MW. The group of peaks Devarbatta, Karaikada, Koulingabetta and Porthimund, all over 2,400 Metres ASL (above sea level) drain into two streams, Avalanche and Emerald. Avalanche and Emerald Dams, along with Upper Bhavani, form the major source of water for the Kundah hydro-electric project.

K Subash Chandra Bose, Chief Engineer (Projects-1), Tangedco, has submitted the project proposal to Union Environment Ministry seeking prior environmental clearance last month and the proposal will come-up for discussion before Expert Appraisal Committee dealing with river valley projects shortly.

Salient features:

Installed capacity: 1,000 MW
No. of units: 4
Unit size: 250 MW
Total cost: Rs 4,200 cr (approx)
Type: Pumped Storage Project

How does a pumped storage hydropower plant work?

  • Here, the turbine acts as a pump, moving water back uphill.
  • Duringperiods of high electricity demand, the stored water is released through turbines.
  • A pumped-storage plant works much like a conventional hydroelectric station, except the same water can be used over and over again.

Need for the project

1. Tamil Nadu and Tangedco do not have reliable hydro potential of this scale. Hence, Sillahalla Pumped Storage is the only feasible alternative available.

2. In view of mandatory large injection of renewables in to the grid in near future, Tangedco needs advance planning to integrate it and Sillahalla can be useful in this regard.

3. Pumped Storage is the natural battery with longer useful life and environmental friendly proposition of Energy Storage.

4. There is a precedence and current trend in favor of Pumped Storage projects. West Bengal has already constructed Purulia PSP (900 MW) and Turga PSP (1000 MW) is now under pre-construction.

Hydropower in TN

Hydro (Non irrigation) - 1,430.65 MW
Hydro (irrigation) - 877.25 MW
Total: 2,307.90 MW



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