The World Bank and the Asian Infrastructure Investment Bank (AIIB) will co-finance the construction of strategic $823.5 million Tarbela 5th Extension Hydropower Project, which has recently been launched by Water and Power Development Authority (WAPDA). The World Bank will provide $390 million and the AIIB $300 million, while remaining project cost, in equivalent Pakistani rupees, is to be borne by the Pakistan government, through WAPDA ($124.5 million) and National Transmission and Despatch Company-NTDC ($9 million). Interestingly, this is one of the first investments made by the AIIB.
Tarbela Dam, consisting of the existing five tunnels, is primarily an irrigation and flood control project, and electricity is considered a by-product. Fourteen power generating units have been installed at the three tunnels, during various stages, with a cumulative installed capacity of 3,478MW. The remaining two tunnels were planned and designed as dedicated for irrigation releases only. It was a Pakistani engineer, late GK Ashai (a chief engineer of Tarbela power-station), who envisioned, more than three decades ago, generating power from the fourth tunnel during the high flow season, without affecting the capacity for irrigation releases. The idea was developed further by local and foreign consultants, establishing technical and economic viability of setting up a powerhouse on Tunnel-4. Fortunately, the project has now materialised.
Commencement of the construction of Tarbela 4th Extension project of 1,410MW capacity (three units of 470MW each) was made in October 2013. Total project cost is $795.8 million, optimising use of existing facilities. It will utilise an existing irrigation tunnel (Tunnel-4) extending from the original plant. Having achieved satisfactory physical progress meanwhile, the powerhouse is now at an advanced stage of completion. Dry tests of the turbo-generator units have been carried out, while wet tests are to be done by early February. It is scheduled to be connected to the national grid before peak demand period of this summer season. Consequently, the first turbo-generator unit will be commissioned on February 25, the second on April 25 and the third on May 30, 2018. Construction cost overrun, which is a normal phenomenon in developing large hydropower projects, is the minimum in this case.
Meanwhile, the Tarbela 5th Extension project, of the same capacity and configuration (3x470MW) and with similar arrangement, has received approval from Pakistan government. Project PC-1 was approved by the Executive Committee of the National Economic Council (ECNEC) on December 20, 2016, while the Indus River System Authority (IRSA) had issued the no objection certificate (NOC) to the project on May 17, 2016. It will use existing irrigation tunnel (Tunnel-5), which will be modified into a power generation source. Also, a 52 kilometre transmission line, with about 60 towers, will be laid to evacuate additional power from this powerhouse, linking to the national grid. WAPDA has already invited expressions of interest for civil works and electromechanical works. Scope of civil works includes modification of Tunnel-5 intake, construction of powerhouse, and commissioning of penstocks, which will be done without impacting the operational dam.
Electromechanical package will cover design, supply, installation, commissioning and testing of turbines, generators, power transformers, main inlet and relief valves, 500-kV circuit breakers, switchgear, control instrumentation and SCADA systems. Power generation at the 5th Extension will be without disrupting generation from Tunnel-4 - the 4th Extension powerhouse. Currently, prequalification of contractors is in hand, and its evaluation reports are with the World Bank for review. Appointment of consultants for the project is in process. The project, planned for completion by March 2022, has already suffered delays since construction or modification of Tunnel-5 was scheduled to start in January last year. It is envisaged that project construction period will be 39 months. The project, which involves large-scale construction at Tarbela Dam compared to the 4th Extension Project, poses critical challenges of environmental and social management, including compensation. Tarbela Hydropower Station, on completion of the 4th and 5th Extension projects, will almost double its total installed power generation capacity—from existing 3,478MW to initially 4,888MW (on commissioning of the 4th Extension), and finally 6,298MW (on completion of the 5th Extension). However, the net total annual generation will increase only by 34 percent - from the current 14,175GWh to 18,975GWh on connecting the two projects to the national grid.
The 4th Extension Project will generate about 3,000GWh and 5th Extension Project about 1,800GWh annually, due to constraints of water availability for power generation resulting in a lower plant availability factor for the 5th Extension Project.
Still, both the projects are technically and economically feasible, for generating clean, low-cost renewable energy in a short time, also helping in reducing electricity load-shedding, decreasing cost of power generation, and, most importantly, improving sustainability of power sector, besides socioeconomic development of the area. On completion, the two extension projects will result in net reduction of greenhouse gas emissions by 20 million tons of carbon dioxide over its projected lifetime, and reduction in power generation cost from existing Rs7.02 to Rs6.85/kWh.
The writer is the former chairman of State Engineering Corporation