In West Bengal, electricity producing units are 1. WBSEB, 2. West Bengal Electricity Production Corporation 3. Durgapur Power project Ltd, 4. Dishergarh Power Supply Corporation & 5. Calcutta Electricity Supply Corporation. In addition to that electricity is also taken from National thermal Power Corporation & DVC.

The major portion of electricity comes from the thermal power sector. The proportion of thermal: hydro electric power is very little here only 97:3. The main problem with thermal electricity is that its quality nose-dives during the peak hours. The under-frequency electricity disables high tech instruments and apparatuses. There is also a bad effect on the supply grid due to high pressure during the peak hours. The main problem with the thermal plants is that they cannot be switched off as par requirements.

On the other hand, hydro-electricity scores over its thermal counterpart on those points. The electricity produced on hydro-projects is qualitatively better having a constant frequency rate. It is needless to say ‘eco-friendly’.

Keeping these in mind, survey and Investigation engineers from WBSEB prepared a primary project report on the Purulia Pumped Storage Project at Ayodhya in 1978.

The detailed project report was subsequently made by the Electric Power Development Corporation, Japan in 1992. The project got approvals from 1. Central Electricity Board (1992), 2. Environment Deptt (1993), 3. Planning Commission of India ((1994).

The financier of the project is the Japan bank of International co-Operation. The estimated project cost is 3200 crores. The full project capacity is 900 mega watts. The project is made on a rivulet called “KESTOBAZAR NALA”. The water which will be used in this project will be sent back to the Subarnarekha River.

WHY A PUMPED STORAGE PROJECT ?
 
A small amount of power can be stored in a Battery Cell but for large power management the storage of electricity is not feasible. The electricity supply in an on line production, transmission and distribution, system. It is for this reason that the matching of demand and supply of electrical energy is a most intricate technology which demands a detailed in-depth techno-economical study of different power sources and their judicious combination. The load demand in a day widely varies from hour to hour depending on types of consumers like Domestic, Commercial, Industry, Irrigation public lighting and water supply system. Often in any particular period the load demand rise and fall very steeply. In a normal situation the load steeply rises at about 5.00 P.M. to 6.00 P.M. and fall between 9.00 P.M. to 10.00 P.M. The coal or nuclear base thermal power generation cannot steeply rise or fall matching the load demand. The thermal power generators cannot be put off and on quickly matching with load fluctuation .If the thermal power stations are to share both base and peak load then the power system become unstable with frequency excursions. Moreover the thermal plants in such conditions have to run at very low load for prolonged period needing fuel oil support and thus cost of generation become too high. With wide range of Frequency variation the industrial units consumer as well as thermal power units run their plants with risk and hazards of damage, their efficiency and life expectancy drastically reduces and the total power system become unstable with risk of grid collapse.
For an ideal power generating system the conventional Storage Hydro Projects, in the grid with sufficient installed capacity can share the peak load and base load can be shared by thermal plants. If storage hydro potential is not available then the other alternative is pumped storage project or gas based project. When natural gas is not available in the vicinity the cost of pipe line to carry gas from a distance place or importing liquid gas become prohibitive. The Pumped Storage Project then becomes the only and an ideal solution. Pump Storage Project does not require a large Reservoir. Reasonably Small Storage for 4 to 6 hrs. at upstream and downstream of the Power House with a short water conductor system can generate large power during peak demand period .It does not require perennial flow in the river.
The system load factor in West Bengal varies between 62 to 64%. Since the entire power, both base and peak load, has to be shared by thermal plants, the PLF cannot attain more than 62 to 64% even though availability factor may be as high as 85%. As per norms applicable in the Eastern Region the entire capital and O & M charges are booked in the tariff when a plant attain 64% PLF whereas Availability Based Tariff stipulates that availability factor of a plant should be 0.85 or more. When a pumped storage project is added to the system the off peak surplus power of thermal plants could be used for pumping with an incremental cost of generation equivalent to fuel cost per unit as capital and other O & M cost  are already booked in the tariff at 64% PLF. Thus pumping available from a thermal plant above 64% PLF will cost only the fuel charges which is now about Re 1.00 per unit. While cycle efficiency of Pumped Storage Plant is 74%, the loss of energy will contribute 25% higher cost. On the other hand ensuring higher PLF from 64% to 85% the fuel efficiency of the thermal plant will be increased by 20% thereby reducing the fuel cost by 20%.Thus the net cost of pumping charge will be around Re 1.05 per unit of generation of Pumped Storage Plant. The  cost of the Purulia Pumped Storage Project is Rs. 3.54 or per MW of  installed capacity which is equivalent to a cost of a thermal plant. The O & M cost is only 2% for Pumped Storage Project and auxiliary consumption is only 0.5% as opposed to 10% and 8% respectively in a thermal plant. Thus net cost of generation of Purulia Pumped Storage Project will remain same or even less than the cost of generation of a thermal plant constructed during same period. The level in tariff of Purulia Pumped Storage Project on above basis comes to Rs. 2.70 per unit. Thus there is more than adequate techno-economic justification for implementation of Pumped Storage Projects in West Bengal. A Pumped Storage Project will have an Upper Reservoir, Intake structure and water conductor system (mostly tunnels and shafts) which will feed the Turbines of the Power House and generate power. The water after power generation will flow through the tail race tunnel and would be is stored in the Lower Reservoir. During lean power – demand hours the surplus power available from the Thermal plants will flow back to the Pumped Storage plant through the same transmission line which was used to evacuate the power during peak demand hours. The generators will then run as motors and the turbines will operate as pumps to lift the water from lower to upper reservoir. The entire power and hydraulic system would run in the reversed mode. During next peak hour cycle the turbines and generators will operate in the normal mode to produce power. There are manifold advantages in the Pumped Storage Schemes. The coal based Thermal Projects will run at 75 to 85% PLF ensuring high efficiency and optimum fuel consumption. During pumping the extra cost will be only that of fuel consumption as all other fixed charge expenses like depreciation, interest, overhead, manpower cost etc. would have been otherwise incurred even if the machines were not running at their full capacity. By ensuring high PLF to the Thermal plants about 20% fuel efficiency would be achieved. Due to recycle of same water, the normal water flow through the scheme is not disturbed and the inflow and outflow of the stream would remain same before and after the scheme is implemented. The evaporation loss will be replenished by monsoon excess flow in each year. Once the Reservoirs are filled up with monsoon water, which otherwise flow unutilized as flood water, the normal flow of the stream in both upstream and downstream of the Power Station will continue in such a manner as if the Power Station is not there. The water from Upper Reservoir to Lower and vice-versa will recycle the water during generating and pumping mode ensuring load management and off peak utilization of Power.

Outline of the project: - Two water reservoir will be made at different heights of Ayodhya hills each having a dam on their outside. The length of the dams at the upper and lower end reservoirs are one and half & 300 mt respectively. The work is expected to be finished by 2007. Both the reservoirs will be connected by tunnels.
The main powerhouse will be housed inside the Ayodhya hills. The electricity produced by the project will be fed into the main grid at Durgapur and Arambag by 400KV line for proper distribution

At Ayodhya Pahar, Purulia Pumped Storage Project (Hydel) (4 X 225 MW), Lot 4, West Bengal is being built for West Bengal State Electricity Board Underground works for 900 MW Powerhouse in JV with L&T, as sub-contractor of Taisei, Japan. In all, 6.40 kms of tunneling out of 6.58 kms complete. Excavation work in progress in power house, transformer hall, cable tunnel, tail race shaft-1. Concreting in diversion tunnel, ventilation tunnel, and diversion tunnel inlet is complete.

ROLE OF PURULIA PUMPED STORAGE PROJECT ( PPSP )
The Purulia Pumped Storage Project can black start from Zero to 900 MW within minutes and can cater hundreds of MW of load within seconds. No other power generating system can accept and reject the load so quickly without slightest variation of frequency in the system. It will not only stabilize the Power system of West Bengal but also will make the state self sufficient with power from the day of its commissioning. The major project work has commenced in 2000 and plant will be commissioned in January, 2007. With the available thermal power stations under WBSEB, WBPDCL, DPL and CESC the base load including pumping power can be managed efficiently and the entire peak power can be catered by the PPSP. The typical daily load curve during 2007 show the peak sharing of load by PPSP with base load by thermal stations
OTHER PUMPED STORAGE PROJECT
Addition of Turga Pumped Storage Project (600 MW) in 2008-2009 and Kathlajal Pumped Storage Project (900 MW) in 2011-12 as envisaged in the power perspective planning in West Bengal will add to the peaking capacity of 1500 MW with judicious addition of thermal power in the system. In the 2011-2012 when peak shortage was anticipated to be 1248 MW in the system a judicious addition of thermal power will cater entire peak shortage by PPSP ( 900 MW) TPSP (600MW) and KPSP (900 MW).The load curve during  2011-2012 shows the participation of PPSP, TPSP and KPSP in the peak load management with thermal power as base load.
 
 

SALIENT FEATURES OF PPSP

Special aspect of the project: - .

• Completely environment friendly. No pollution due to emission of fumes.
• No flooding of existing residential localities
• No family is to be displaced from the project area. The nature of the Ayodhya hills is being disturbed to the minimum. Reforestation is being done in alternative areas to replace the forest area utilized by the project.
• The water reservoir will attract the seasonal birds as well as tourists. A new tourism industry is expected to start to supplement the income of the local people

PRESENT STATUS
 ‘Joint Venture-Purulia’ consisting of M/s. EPDC, Japan and M/s. WAPCOS, India was appointed as Main Consultants for detailed design, tendering, construction supervision of the Project and an agreement was executed on 31.10.1995. The work started on Ist January 1996 and is progressing.

 The Project in its present form involved construction of two Rock fill dams with Central clay core for Upper and Lower Reservoirs with a live storage of 13 million m3 each, twin water conductor through tunnels and shafts, an underground power house to accommodate four reversible pump turbine of 225 MW each, an underground transformer cavern with an access tunnel, 400 KV Gas Insulated Sub-Station linked through a cable tunnel. Two 400 KV double circuit transmission lines connecting Durgapur and Arambag with the Project will also be developed to transmit and receive bulk power.

The field investigation & preparation of Detailed Project Report (DPR) was completed by the West Bengal State Electricity Board with the loan assistance of Japan Bank for International Cooperation ( JBIC), erstwhile Overseas Economic Cooperation Fund (OECF), Japan. M/s. Water & Power Consultancy Services (WAPCOS) in association with Central Electricity Authority (CEA) and Central Water Commission (CWC) Govt. of India organizations were associated for the project as local Consultants and M/s. Electric Power Development Company (EPDC), Japan as Foreign Consultant.

The Project was cleared by Planning Commission in 1994. The Loan Agreement with OECF ( now renamed as JBIC ) concluded in 1995. However after detailed design and layout, first stage land acquisition, preparation of National and International competitive Bidding documents as per JBIC guidelines and the infrastructure work could start only in 1997 – 1998. At present all infrastructure work like road, colony, office, construction power line etc are completed to start the main works. All major tenders are also finalized. 232.42 ha of forest land for Reservoirs and part of Main Civil Works is diverted. Out of 142.75 ha of additional forest land required for Quarry/ Stockpile Yard & Processing Area / Construction facility / Transmission Lines etc, formal clearance for diversion of 131.67 ha excluding 11.08 ha for rock quarry was accorded by MOEF/Govt. of India on 07.02.2002 and the permission from the State Forest department to take up work on above land was obtained through the letter dated 11.03.2002. In regard to diversion of 11.08 ha of additional forest land for rock quarry needed to construct Upper Dam of the Project, after protracted persuasion the Ministry agreed that additional forest land of 9.07 ha shall be given instead of 11.08 ha as was proposed earlier. Conditional clearance i.e. Stage-I clearance of the above land was accorded by the MOEF vide their letter No. 8-112/99-FC (Vol. II) dated 12.08.2002. Further actions are in process to get the final clearance. 
Prospects: - After the successful commissioning of the project, a number of such projects are on the anvil.

• Turga Pumped Storage Project 600 mw
• Kathla Pumped Storage Project 300 mw
• Bachhunala Pumped Storage Project 300 mw
• Kulbera Pumped Storage Project 600 mw

Completion of these projects will change the entire electricity scenario of the eastern zone

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