To meet India’s ambitious renewable energy targets and climate commitments, the uptake of hydropower and pumped storage plants (PSPs) will be crucial. THDC India Limited, a PSU operating in the hydropower segment, has been actively working in the PSP space as well. At present, THDC’s portfolio consists of nine projects across hydro, thermal, wind and solar, with a combined capacity of 4,351 MW. This includes 1,587 MW operational projects and 2,764 MW under-construction projects. The PSU is currently developing one of India’s largest on-river and the first variable speed PSP at Tehri, which is expected to enhance the peak power capacity by 1,000 MW in the northern region.
Project characteristics
The Tehri complex, with a total capacity of 2,400 MW, comprises three distinct projects – the (4×250 MW=1,000 MW) Tehri Dam Stage I, (4×250 MW=1,000 MW) Tehri Dam PSP Stage II and (4×100 MW=400 MW) Koteshwar Dam stage III. The Tehri Project Stage I was completed in 2006-07. It includes a 260.5 metre high rockfill dam and an underground powerhouse near the dam site. The Koteshwar Dam Project, located 22 km downstream of the Tehri Dam, features a 97.5 metre high concrete gravity dam and was commissioned in 2011-12. The reservoir formed by the Tehri Dam and Koteshwar Dam will serve as both upstream and downstream reservoirs for the PSP. This plant will significantly aid in stabilising operations by meeting peak load demands and fulfilling balancing requirements. The construction of the Tehri PSP has been ongoing since July 2011. The contract for this project was awarded in 2011 to a consortium comprising Alstom Hydro France (now known as GE Hydro France), Hindustan Construction Company Limited and Alstom Project India Ltd (now known as GE Power India Limited).
The PSP project has distinctive characteristics, including a significant variation of approximately 90 metres between its maximum (830 metres) and minimum (740 metres) operating heads, accommodating reversible units. It also incorporates variable speed units designed to enhance cycle efficiency and improve power regulation capabilities across the varying head conditions. The operation of the Tehri PSP revolves around the recycling of water discharged between the upper and lower reservoirs. Upon completion, it will contribute an additional generating capacity of 1,000 MW in peaking power to the northern region, producing an annual generation of 2,475 MUs. The pumping operation for reversible units will necessitate approximately 3,104 MUs of off-peak energy.
Project cost
The Government of India sanctioned the construction of the Tehri PSP in July 2006 at a total cost of Rs 16.57 billion, which included interest during construction of Rs 816.4 million at the December 2005 price levels, with a debt-equity ratio of 70:30. Subsequently, a revised cost estimate (RCE-I) of Rs 29.78 billion at the April 2010 price levels was approved in November 2011. RCE-II, amounting to Rs 48.25 billion at the February 2019 price levels, was approved on July 31, 2021. Currently, RCE III has been prepared at the June 2023 price levels and submitted to the Central Electricity Authority (CEA) for approval. The proposal for time overrun is currently under examination by the CEA.
The project has faced some delays and cost overruns due to several reasons. There were a lot of agitations from the designated area of the dumping yard. Other reasons include various geological surprises. The tail race tunnels encountered a higher rock class than expected in the detailed project report. This caused a lot of time overrun during construction. Moreover, the project faced setbacks due to the impact of the Covid-19 pandemic, which also contributed to financial challenges experienced by the civil contractor.
The way forward
A key lesson learnt from the case study is that conducting survey and investigation studies religiously and thoroughly is crucial. Furthermore, financial health of hydro contractors is very poor, which leads to cost and time overruns, and the need for financial assistance. Moreover, scrutiny by the employer should be done during the execution of the project.
The Tehri PSP is at the final stages of implementation. The commissioning of the project is expected in the current financial year. In order to ensure the timely completion of the remaining work, the PSU should consider detailed micro-planning and take corrective actions. It is essential to closely monitor and optimise the cycle time for excavation and other tasks. Net, net, with the commissioning of the Tehri PSP, the country will have the distinction of installing the first variable speed PSP, however, with significant cost and time overruns.
