Mature Technology: Focus on pumped storage for clean and balancing power

Pumped storage plants (PSPs) are be­ing recognised as one of the largest forms of storage available at a competitive cost. It is a mature technology that offers the benefits of simple design, ease of scalability and operation, and quick ramping. Further, in view of the large renewable energy capacity ad­d­ition planned for the next few years, PSPs are expected to play a vital role in pro­viding clean and balancing power. This will help address the variability and un­certainty issues associated with rene­wable energy sources. Pumped hydro en­ergy storage (PHES) not only generates and stores electricity but also has other use cases such as round-the-clock su­pport, load following, energy arbitr­age, peak shaving, renewable energy sm­oo­thening and ancillary services.

Status of PSP development

As per the Central Electricity Authority (CEA), India has eight pumped storage projects, with a total capacity of 4,745.6 MW as of November 2021, installed in va­ri­ous locations across the country. How­ever, only six plants with an ins­ta­lled capacity of 3,305 MW are working in the pumped mode. The remaining 1,480 MW of capacity across two sites is not curren­tly operational because of the delay in the construction of tail pool dams and vibrational issues. Further, there are two under-construction PSP projects with a total capacity of 1,500 MW. The 1,000 MW (4×250 MW) Tehri Stage II project in Uttarakhand being implemented by THDC Limited is likely to be commissioned by 2023-24. It will be the first PSP in the central sector. The 500 MW (4×250 MW) Kundah PSP Stages I, II, III and IV, being implemented by the Tamil Nadu Generation and Distribu­tion Corporation in Tamil Nadu, is likely to be commissioned by 2023-24. Mean­while, construction of the Koyna Left Bank (80 MW) po­wer project in Maharashtra, being implemented by the Water Resources Depart­ment of the state, is held up.

The CEA has estimated the overall po­t­ential of PSPs in the country at 96,524 MW across 63 projects. Currently, survey and investigation are in progress for 17 projects totalling 16,770 MW. The detai­­l­ed project report (DPR) for the Turga project (4×250 MW) in West Bengal has been approved, while the 1,200 MW Pinna­pu­ram project in Andhra Pradesh is under examination. In addition, DPR/ preliminary investigation report/pre-fe­a­sibility report (PFR) has been prepared for 7,755 MW. However, the PFR for 1,100 MW is under preparation.

Issues and challenges

Despite various advantages of a PSP, the growth of PSPs in the country is slow. The CEA has estimated a PSP potential of 96 GW, of which only 3.3 GW is currently operational in India. This sl­ow pace can be attributed to the high cost associated with the commissioning of PSP, the long gestation period (due to de­la­ys in obtaining environmental cl­ear­an­ces) and poor recovery from the existing pricing mechanism of PHES. There are also issues regarding finding a suitable site, finalising the project layout, op­e­ra­t­ing restrictions during the monsoon, ma­chine selection and equipment delivery schedules. PSP adoption is further ha­m­pered by monopoly in equipment su­pply and limited financing options. An­other issue pertains to the existing tariff mechanism for PSPs, which en­sures the recovery of the full cost of the PSP over the years. This hampers private invest­m­e­nt in the sector. That said, there is an ur­gent need for a pricing mechanism that can ensure profit generation for developers over and above their fixed cost and variable cost components. Last but not the least, guidelines for the development of pu­mp­ed storage also need to be fram­ed.

The way forward

Going forward, as per the CEA’s optimal generation mix, it is expected that pu­mped hydro storage will almost triple by 2030. With hydropower stations’ fast-ramping capability and the ability to respond more quickly than thermal stations, storage and pondage hydropower stations are proposed to be gainfully uti­lised for regulation services to meet the system requirements. Flexibility of PSPs, that is, fast ramp rates, fast start-up and shutdown, and low cycling costs, make th­em ideal suppliers of regulation and contingency reserve ancillary services. With greater integration of renewable energy, the role of PSPs is expected to inc­rease in the coming years as they can act as energy reservoirs to balance load.