Hydropower stations being refurbished and modernised
ENGINEER HUSSAIN AHMAD SIDDIQUI
ARTICLE (March 18 2010): Total installed capacity of hydroelectric power plants in Pakistan is 6,474 MW, which contributes about 33% to the combined installed generation capacity of all resources. During the financial year ending 30th June 2007, hydro energy generation of 31,846 GWh was dispersed through the national grid, at a cost ranging from Paisa 35 to paisa 167 per kWh unit for different power stations.
A significant number of the existent power stations are very old, almost 30-40 years, though a few small hydropower plants were even commissioned as early as in 1925 and 1938, and all are still operative. Generally, the manufacturers of generating units prescribe a useful life of hydropower station as 30 years, depending on the operating conditions.
But, total replacement of installed machinery after completion of its lifecycle is not considered techno-economically feasible as it entails huge capital outlay. Nonetheless, the power stations, generally, have potential for achieving higher efficiency and, in most cases, increased output too.
Hence, fundamental rehabilitation and refurbishment of the electromechanical equipment and system of existing plant is carried out, which enhances plant's operating life by another 20 years or more. This is achieved by incurring a nominal cost, comparing to installing new generating sets. Hydropower is a well proven and advanced technology, with modern power plants providing the most efficient power generation ie up to 90%, the lowest operating costs and longest plant life as compared to any other energy resource.
Pakistan Water and Power Development Authority (Wapda) is strongly committed to sustainable development of hydropower, at an accelerated pace, in order to secure national power supply to meet the growing demand. While work on its various new hydropower projects is in progress at varied ongoing stages of construction, development and planning, Wapda is alive to the need of undertaking rehabilitation, up-gradation and modernisation of turbines, generators and allied equipment at its major power station installations.
An extensive programme to renovate, upgrade and up-rate the major power stations, with total capital expenditure of billions of dollars, has been worked out to be implemented, progressively, during the next five years. This is in addition to carrying out annual maintenance, replacement of spares/components and periodic general overhauls of the machines installed, which remains an ongoing regular exercise.
The plan primarily aims at improving availability of power stations through enhancement of the turbo-generators' output and efficiency, ensuring reliable and economic power generation.
Latest technological advancements in metallurgy, instrumentation and controls, insulation materials for electrical equipment and quality control techniques, etc have made the modern equipment much better in performance and efficiency as compared to those installed in the power houses decades ago.
Increasing the capacity and energy output is possible either by carrying out modifications in existing turbine runners or by replacing with up-graded runners. Likewise, modern generator development, such as optimal cooling, design innovations and adopting lower class F insulations, has resulted in greater generator efficiency. Recent technical and safety improvements corresponding to the automation technology focuses on protection, excitation and enhancement of human-machine interfaces.
Mangla power station has an installed generation capacity of 1,000 MW. Ten generating units each of 100 MW were commissioned during the period July 1967 to July 1994. Though the power station has been operating largely trouble-free, the quality and reliability of the original electro-mechanical equipment has deteriorated and is no longer of satisfaction. Efficiency has reduced from the designed values of the respective equipment installed. It is therefore, envisaged to undertake refurbishment and rehabilitation.
Also, it is considered feasible to effectively enhance power station capacity from the present 1,000 MW to 1,250 MW, whereas improved power potential up to 1,500 MW cumulative capacity can be attained with the recent completion of Mangla Dam Raising Project. WAPDA is currently in the process of appointing international consultants, who would determine the most viable option for up-gradation and refurbishment of all the installed generating units, as well as achieving greater capacity of the existing power station.
Warsak power station, regarded as the pioneering medium-size hydropower project in the country, has an installed capacity of 243 MW. Four generating units of 40 MW each were commissioned in 1960, whereas its extension, carried out in 1980-81, has resulted in installation of another two units, each of over 41 MW capacity.
First phase of rehabilitation of power station was undertaken during the period from 1996 to 2006, to restore full generating capacity of 243 MW.
However, further ageing of electromechanical equipment, problems in civil works and sedimentation has now caused a net loss of 30 MW in power generation. This has necessitated undertaking the second phase of refurbishment and rehabilitation. Wapda has invited the EOI (expression of interest) for consultancy services to seek the most cost-efficient solution to restore and maintain the ability of power station to full generation capacity of 243 MW. The refurbishment and modernisation plan also covers rehabilitation of civil works and sedimentation management at the power house.
The largest hydropower station at Tarbela has 14 units, of cumulative installed capacity of 3,478 MW, in full operation. Four units of capacity 175 MW each were commissioned in 1977; another 6 units of 175 MW each during 1982-85, whereas the latest 4 units of 432 MW each were commissioned during 1992-93. The equipment has started showing signs of ageing. Selective up-grading and updating of the power station, based on the current international standards of safety and performance, is therefore, planned.
Despite obsolescence, all the existing hydropower stations have been giving excellent continuous service, under the given conditions and limitations. It has been made possible due to Wapda, having a strong backup of professionals and skilled manpower. Wapda engineers have shown very high levels of commitment and responsibility during breakdowns and accidents that occurred in recent past.
At times, on-site emergent repairs were undertaken without any foreign assistance, restoring power generation within the shortest possible time. Still, this is the high time that refurbishment and modernisation of power stations be undertaken at a large scale, with due emphasis on strengthening of its human resources by imparting advanced training.
Hydropower, the most economic form of renewable energy, which is environmental-friendly too, meets about 20% of the world's electricity requirements. The demand for hydropower is increasing globally and Pakistan is no exception. To optimise existing operations and maintenance of hydropower stations is a salutary measure in this direction.
Concerted efforts, however, should be made by Wapda to the expeditious implementation of the planned refurbishment and modernisation, aiming at accomplishing it within the stipulated timeframe and at reasonable cost.
(The writer is former Chairman of State Engineering Corporation, Ministry of Industries and Production.)
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