The Bhutanese Leading the way.
On 17th December 2024 two units of the P II project started generating power with its inauguration by the Minister for Energy and Natural Resources Gem Tshering. The two units are of 340 MW capacity and as per procedure it directly is not allowed to generate as much in one go, but 20 MW is added each time till the full capacity is reached.
The 340 MW generation may come down to 170 MW in January and February when rivers levels are lower, but it depends on hydrology.
The two units can be run right now due to the volume of the water in the river.
The dam can store 4 hours of water at a time and so in winter it can provide a useful service of peak power in Bhutan. For example, the maximum demand for power in Bhutan during winter is from 5 to 9 pm when heaters, geysers and devices are on and so the dam can store water for four hours in the afternoon and release it to meet this peak demand.
This 340 MW generation also offsets the import of power in winter. The highest import of power in December 2024 was 507 MW.
The onetime highest power import was in February at 1100 MW but this was for a peak for a short duration.
The import substitution is important for winter as while Bhutan exports power to India at an average tariff of Nu 3 the average import tariff is Nu 4 to 5.
The estimated project completion cost is Nu 94.456 billion (bn) and 98.25% of the work is complete with the remaining work being the spinning of the remaining 4 units in phases with all six units all expected to be online in June 2024 when the river has the water for it.
The commissioning of the first two units was hampered due to seepage from the roof or cavern of the Power House hall after the initial inauguration on 15th August 2024.
Officials now assure that the seepage is no longer there as penetron painting and grouting was done in the lower end of the HRT tunnel and surge shaft. A false ceiling which was anyhow supposed to be built is also now complete.
This is, however, only one of the many challenges faced by the project.
In 2013-14 the P II Dam foundation encountered a major shear zone which had to be treated delaying the project by a year and costing Nu 387 mn.
Then in March 2016 the crown of the Downstream Surge Gallery (DSG) collapsed burying 6 workers and delaying the project by 4 years.
In both the above instances the former Director Technical of the P-I and P-II project from 2010-2017, Yoginder Sharma, blamed the overall project consultant Water and Power Consultancy Services (WAPCOS) and the civil works consultant and expert Central Water Commission (CWC) for not doing adequate studies.
As if things could not get any worse in August 2019 the Phelraychu flash flood washed away electro mechanical equipment of BHEL.
Just when things were looking up COVID-19 hit from March 2020 which again slowed down things.
The tariff is in the final stages with a Joint Technical team of both countries making suggestions and the two power secretaries are supposed to meet. The likely tariff and Bhutan’s expectation is Nu 5.25 per unit which can generate Nu 22.8 bn in annual revenue.
Bhutan can keep the entire revenue for the first year and from the next year loan repayment starts at 10% interest rate. The project is built on 70 loan and 30 grant from the Government of India.
The unique feature of P II is that it is the first project in Bhutan to use the Francis turbines shaped like conches instead of the Pelton turbines shaped like buckets. The reason being that the P II has a good volume of water but lesser head or height.
Another unique feature is that the HRT tunnel which carries the dam water to the turbines has a widest diameter in South Asia at 8.6 meters.
Compared to Tala, which has analog controls the control system in P II is more advanced with a digital system.
An official said that the P II project is a testament to the collaboration between the two parties of GoI and the RGoB. He said the collaboration between the two sides also allowed for solutions to come up.
In terms of lesson learnt from the project an official said it is important not to deviate from the Detailed Project Report as a lot of studies are done for it.
The power house was supposed to be overground as per the original DPR, but it was moved underground to save money and muck digging but in the end the collapse of 2016 pushed up the costs anyhow and caused delays.
