I M Sahai reports on pumped storage projects currently under development in India
FOR a country with one of the largest hydro resources in the world, the slow development of hydroelectric potential in India is well-documented. The share of hydro to the total installed capacity in the country, which was around 50% in the year 1962-63, steadily declined over the next four decades, falling to around 25% presently. This had been even worse in regions like western and eastern India, where it was between 12-13%.
India has an estimated 150GW of hydroelectric potential (around 84GW at 60% load-factor). Of that, only around 25GW has so far been developed. On the other hand, the installed capacity for thermal power has rapidly increased to around 75GW.
In 1978, the Central Electricity Authority (CEA), the technical wing of the federal Ministry of Power, undertook a comprehensive survey to identify the potential for pumped storage projects in India. The survey identified 56 sites with an estimated total capacity of about 94GW, with almost 40% of the total potential in the western region.
The states of Maharashtra and Madhya Pradesh, along with Karnataka in the south and Mizoram in the north-east, could locate a total of 36 pumped storage plants (64.3%) with an aggregate installed capacity of 56.5GW (60.2%). Even Gujarat state in the western region could set up a capacity of 1440MW from two schemes, including the Sardar Sarovar project.
Further surveys revealed that not only were many individual pumped storage plants techno-economically feasible but, by utilising the off-peak power of thermal plants for pumping water, they led to an increased efficiency of such plants. Yet the progress of the installation of pumped storage plants in the country has been very slow. The first pumped storage plant was commissioned in 1980, and in the following two decades until 2000, only a further eight plants had been commissioned with a total capacity of 1554MW, mostly by the state-owned utilities.
Another four plants (3250MW) were then under construction. These included the 1200MW river bed power house at Sardar Sarovar in Gujarat and the 900MW Purulia pumped storage plant in West Bengal, two States which badly needed projects. However, even on their completion, the total installed capacity of pumped storage plants in the country would be less than 5GW.
Progress of pumped storage
The first pumped storage project in India was installed in the 1980s at Nagarjunasagar in the southern state of Andhra Pradesh, where a unit of 110MW was already in operation. Utilising the existing infrastructure, seven units of 100MW were installed in two stages between the years 1980-85. The work was funded by loans from Japan’s OECF (now JBIC) amounting to US$69.9M and US$58M. The turbines, supplied by Japan’s Hitachi, are vertical shaft reversible Francis, operating under a net head of 93m and a rated discharge of 126m3/sec. Japan’s Mitsubishi supplied the generators. The plant has been envisaged for mixed generation, but has operated in the conventional mode in the absence of a tail pond dam.
Later, the Andhra Pradesh State Electricity Board decided to execute the 900MW (6 x 150MW) Srisailam left-bank pumped storage plant, which would utilise Nagarjunasagar as the lower reservoir. Srisailam project, on the left bank of river Krishna, supplements a conventional 770MW (7 x 110MW) power station on its right bank which was commissioned in two stages during 1982-87. Also funded by Japan’s OECF, Srisailam is a mixed type of scheme. It utilises the existing Srisailam reservoir as the upper storage. The power house is underground, with six reversible generating units of 150MW
each, operating under a rated net head of 91m, and supplied by Japan’s Sumitomo Corporation.
Also in the south, the 400MW Kadamparai pumped storage plant came up in Tamilnadu state during the years 1987-89. It is located on a river of the same name and utilises the base created for the earlier 60MW Aliyar project. An upper reservoir had to be created by construction of a masonry-earthen dam. Its underground power house has four vertical Francis reversible units rated at 102MW, with generators of 100MW. The first unit was supplied by Boving and GE of the UK, while the latter collaborated with India’s BHEL to supply the other three units, all of mixed type.
In 1991, the only pumped storage plant set up until now by a federal utility in India, was developed at Panchet Hill in Bihar State. It was set up by Damodar Valley Corporation, at the toe of an existing dam on river Damodar. To an existing 40MW unit of conventional type, a second reversible unit of the same capacity was added. The turbine was supplied by Voist Alpine and the generator by Elin Union of Austria.
In the Western Region, Maharashtra state has seen three pumped storage plants installed (including the only one in the private sector), while a fourth is under construction. In 1984, a 12MW unit was set up at the toe of an existing irrigation dam at Paithon in Aurangabad district. The reversible Francis unit was supplied by Japan’s Fuji and funded by OECF. A 12MW unit was also commissioned at Ujjani in Solapur district in 1994. It was supplied by Japan’s Nissho Iwai, with a loan again from OECF.
Bombay-based Tata Electric Co (now Tata Power) had set up a conventional hydroelectric plant in 1927 at Bhira, south-east of Bombay, to supply power to its consumers in that metropolis. The company decided to add a 150MW pumped storage unit at the power station, with a maximum gross-head of 515m. Here, the existing base was utilised with some modifications. The vertical reversible Francis turbine-generator was supplied by Sulzer Siemens of Germany, and the project commissioned in 1995.
A 250MW (2 x 125) plant at Ghatghar in Ahmed Nagar district has also been developed, with a masonry dam over Pravara river. Its underground power house has two units of vertical reversible Francis type operating under a design head of 385.6m. The project has been funded through a loan of US$94.6M by OECF sanctioned in 1989.
When the CEA undertook its 1978 survey of potential pumped storage sites in India, it looked at the Western Region in the context only of the states of Maharashtra and Madhya Pradesh. Gujarat State, with its dependence on thermal power, was not included. Yet, by the year 1990, the first pumped storage plant in Gujarat – Kadana (120MW first stage) – had been commissioned, followed by a 120MW second stage in 1997. Located in Panchmahal district, on Gujarat’s border with Madhya Pradesh, the Kadana project utilises the water of the river Mahi. The scheme is mixed, permitting both conventional and pumped storage generation.
Gujarat is also home to the largest pumped storage plant in India – the Sardar Sarovar Project (SSP). SSP is a multi-purpose, inter-state scheme, having components of power, irrigation, water-supply and flood control.
Sardar sarovar project
The Sardar Sarovar project, under development for over two decades, is based on a main dam across the river Narmada, a major west-flowing river of India. The concrete-gravity dam presently under construction will be 163m high and 1210m long. It will create a reservoir with a live storage of 5800Mm3, a maximum gross storage of 9500Mm3, and a catchment area of 88,000km2.
Water from this reservoir will be taken by six penstocks, each 110m long, 7.72m in diameter and 240m3 capacity. A lower reservoir is being created by raising a weir across the Narmada river at Garudeshwar, about 12km downstream of the main dam. The weir will be 990m long, 28m high, and have a live storage of 34.36Mm3 and gross storage of 124Mm3.
The 1200MW river-bed power house will be underground, on the right bank of Narmada, and located about 165m downstream of the main dam. It will have six units of 200MW, vertical Francis reversible turbine-generators, operating under a rated head of 100m, varying between 80.6-112.8m.
The power house was originally scheduled to have been commissioned in the years 1994-95. However, apart from the long delays in the project itself caused by a number of major factors, Sardar Sarovar Narmada Nigam Ltd, the project executor, had a dispute with the supplier of the generating units, Sumitomo Corporation of Japan. As a result, the latter stopped production of those units for almost eight years, and also withheld deliveries of the equipment already fabricated. The dispute has since been resolved, and deliveries have resumed, but commissioning of the power house has been delayed by almost a decade.
India’s eastern state of West Bengal has been facing a particular problem in its power generation. As it was, the hydro-non-hydro ratio in installed capacity in the Eastern region had been an unsatisfactory 12:87 (against a national ratio of 25:75). West Bengal’s own ratio was even poorer, and getting worse as big coal-fired plants were developed, both in the public and private sectors.
According to the state-owned West Bengal State Electricity Board (WESEB), due to the paucity of hydro power, the entire power demand in the state, both base and peak load, had to be shared by thermal power. Since the storage hydro potential in the state was found to be limited, pumped storage became the only practicable option available to WBSEB.
In 1979, WBSEB identified four sites for pumped storage plants, all in one particular area in the state – Ayodhya hills in the Purulia district. Of these, Purulia pumped storage plant was taken up for development first. The other three sites were at Turga, Kathlajal, and Badhunala.
The 900MW Purulia project was sanctioned in February 1994, with a loan agreement signed by WBSEB with Japan’s OECF, signed in February 1995. WBSEB appointed two consultants in October 1995 for the detailed design, tendering, and construction supervision of the project. These were Electric Power Development Co (EPDC) of Japan as the overseas consultant, and Water and Power Consultancy Services (WAPCOS) of India as the local consultant.
Purulia pumped storage plant is to be located on a small stream called Kistobazar Nullah. The project site is about 300km northwest of Calcutta. It involves construction of two rockfill dams with central clay-core for the upper and lower reservoirs with a live storage of 13Mm3 each, and catchment areas between 9.25-9.50km2. The upper dam would be 71m high and 1505m long, while the lower dam would be 95m high and 310m long.
The project will have two horizontal intakes with maximum level of 526m and total discharge capacity of 600m3/sec. The water-conductor system will comprise two steel-lined headrace tunnels, each 475m long, 7.7m in diameter with a discharge capacity of 300m3/sec.
There will be an underground powerhouse 157 x 22.5 x 47.7m in size, housing four vertical shaft, Francis reversible turbine-generator units of 225MW each. The head variation in the generating mode should vary between 149.4-214.5m, and in pumping mode between 159.0-218.8m. The maximum turbine and pump discharges will be 150 and 141.2m3/sec respectively.
Purulia will be a pure pumped-storage scheme without any conventional energy generation, and is expected to provide the entire peaking power required at present in the state, operating for six hours daily. The power will be evacuated by two double-circuit, 400kV transmission lines 150km and 160km in length.
All infrastructure on the project works, which began in 1997, has already been completed. All major tenders have been finalised, while those for the transmission lines are being processed. The project authorities are also following up with the federal Ministry of Environment and Forests to get approval progressively for the forest clearance in the project area. The cost of the project, originally sanctioned at US$304.7M, has more than doubled to US$667M.
As per the schedule drawn up by WBSEB, the commissioning of the four units of Purulia would follow a reverse order, with the fourth unit coming into operation first, on 12 April 2007. The remaining three would be commissioned at three-month intervals with the whole project expected to be in operation by January 2008.
Of the remaining three sites identified in the Purulia district of West Bengal State, the feasibility of the 600MW (4×150) Turga pumped storage plant is already being examined. Utilising a financial grant from the French Government, EdF of France had been engaged by WBSEB for the preparation of a pre-feasibility report for the Turga project. A draft report was submitted by EdF in November 1998. A final report, according to WBSEB, ‘is under preparation, and will be submitted soon’.
In view of a projected shortfall in energy of 1248MW in West Bengal expected by the year 2011, WBSEB is taking up the remaining two projects – the 900MW Kathlajal and the 1224MW Badhunala pumped storage projects. Both have been posed to Japan’s JICA for a detailed investigation and for preparation of project reports.
Collaboration with nhpc
As with most State-owned utilities, a major reason for the slow progress of power projects in West Bengal had been the resource-constraint with WBSEB. Keeping that in mind, the latter entered into a memorandum of understanding (MoU) with the federal-owned National Hydroelectric Power Corporation (NHPC) in May 2001.
Under the MoU, the two partners would set up a joint-venture company to develop and execute the Purulia project. NHPC would hold 67% equity in the new company, which would be headed by NHPC’s chairman and managing director. The existing mode of financing the project through the JBIC loan would continue. The State Government would have the first option to buy Purulia power, and WBSEB would enter into a power-purchase agreement with the new company for that purpose, the price to be calculated ‘according to the prevailing statutes’.
It is understood that the new company will also take up the execution of Turga project. For NHPC, seeking to increase its installed capacity from around 2200MW as at present to around 30,000MW by the end of the next decade, its collaboration in these two projects would be a welcome addition to its business.