Tangsibji Hydro Energy Limited (THyE) is a wholly owned subsidiary of Druk Green Power Corporation Ltd. It was established on April 25, 2014 as a Special Purpose Vehicle (SPV) for the development of the 118 MW Nikachhu Hydropower Project, now known as the Nikachhu Hydropower Plant. The main civil and hydro-mechanical works (MP-1) contract was signed between M/s Hindustan Construction Company Ltd., India and THyE on April 20, 2016. The electro-mechanical works (MP-2) contract was awarded to M/s Voith Hydro Pvt. Ltd., India on December 30, 2015.
The Nikachhu Hydropower Project is a run-of-the-river scheme located in Tangsibji Gewog, Trongsa. The dam site is situated at Lorim, approximately 6 km downstream of Chendebji Chorten. The project diverts a design discharge of 25.45 m³/s through a 4-meter diameter headrace tunnel measuring 11,998.50m, supplying two Pelton turbines in the powerhouse with an installed capacity of 118 MW. The water is subsequently released into the Mangdechhu Hydropower Plant reservoir.
The project was initially estimated at BTN 11.96 billion, with a financing structure of 65:35 debt-to-equity, supported by funding from the Asian Development Bank (ADB) and Indian Commercial Banks (ICBs). The Commercial Operation Dates for Unit-2 and Unit-1 were achieved on January 25, 2024, and February 8, 2024, respectively. At completion, the total project cost increased to BTN 16.007 billion.
The project has a design energy generation of 491.52 MU per year. After accounting for royalty energy, 80% of the remaining energy is contracted with Power Trading Corporation, India for export. The remaining 20%, including royalty energy, is supplied to the domestic market and exported during surplus summer months via the Indian Energy Exchange. Royalty energy is set at 12% of saleable energy for the first 12 years of the concession period and 18% for the subsequent 18 years.
The initial Pre-Feasibility Study (PFS) for a 210 MW Nikachhu Hydropower Project was undertaken by DGPC in 2010 following approval from the Department of Energy (DoE). The study was upgraded to a Feasibility Study (FS) level in December 2009 and later approved by DoE in January 2011, initially considering an independent 210 MW scheme with tailwater discharge into the Nikachhu river.
To reduce geological risks and minimize social and environmental impacts, alternative configurations were explored, including relocating the surge shaft and powerhouse to Norbudoi and diverting tailwater into the Mangdechhu reservoir. This revised study approach was approved by the DGPC Board in October 2011.
The final feasibility study, submitted in September 2012, proposed a run-of-river scheme with an installed capacity of 115 MW and an average annual generation of 475.00 GWh from Nikachhu, along with 324.27 GWh additional generation from the Mangdechhu Hydropower Project, totaling 799.27 GWh annually. This was lower than the earlier estimate of 843.61 GWh for the standalone 210 MW scheme.
The selected configuration, which discharges tailwater into the Mangdechhu reservoir, was considered suitable for detailed project development. The Detailed Project Report (DPR) was prepared between April and September 2013. Due to an increase in dam height to enable 4 hours of peaking capacity, the final installed capacity was revised to 118 MW, with expected annual generation of 491.52 GWh from Nikachhu and 323.77 GWh additional generation benefiting the Mangdechhu plant.
The DPR was approved by DGPC in its 43rd Board Meeting on September 26, 2013, followed by Cabinet approval on March 04, 2014, and formal government approval communicated on March 20, 2014.
The 1st Extraordinary General Meeting of shareholders and the 1st Board Meeting of THyE were held on August 28, 2014, marking the operational commencement of the company.
While THyE’s CEO and Board provide strategic direction, governance oversight, and external representation, the operation and maintenance of the Nikachhu Hydropower Plant is carried out by the Operation & Maintenance Services Center of DGPC under a dedicated O&M Services Agreement.
