MINI  UPPER  TAMA-KOSI  HYDROPOWER For Quick Relief From Load-shedding Crisis

<br><EM>-&nbsp;Dr. AB Thapa</EM>

May 1, 2011, 5:45 p.m. Published in Magazine Issue: Vol. : 04 No.-21 April 29-2011 (Baisakh 16,2068)

The 456 MW Upper Tama-Kosi Hydropower Project proposed to be built by the NEA in remote   part of the Himalaya is a very attractive project.  Unfortunately, under present circumstances the implementation of this extremely large project could push the NEA  further  into  deep  financial  difficulties.  It   also could not be completely ruled out that as a result of it   even the economy of the entire country might   be  put in jeopardy.


Mini Upper Tama-Kosi Project
For quick relief from  the present power shortage crisis   relatively  a much  smaller  alternative of the NEA proposed 456 MW Upper Tama-Kosi Project would be best suited for implementation in near future. The proposed alternative to NEA’s 456 MW project  would involve  insignificantly  less risk of damages to structures at the time of glacier lakes outburst floods (GLOF). Similarly, the possibility of substantial drop in generation of electricity  resulting  from  the seepage  of water through the highly porous floor of the reservoir particularly in dry seasons ,  when the demand for electricity is the highest, would be almost totally avoided.


Considering  the nature of the present demand for electricity in our country and also the vulnerability of main project structures,  the installed capacity of the Upper Tama-Kosi Project must be limited to just over 100 MW. Even after such drastic reduction in installed capacity  the total generation of electric energy during the dry season period would still be equal or even exceeding the generation by the NEA proposed 456 MW project  despite the fact that the cost of such mini- project would be only about one third.  As the demand for peaking energy grows in future  the installed capacity could be raised with ease by providing additional structures.


Nature of Loadshedding
At present during  the wet season months  quite limited areas are affected by load-shedding lasting  only for a very short period in the evening. Even such limited disruption in supply of power might have been  to a  certain  extent the result of transmission lines congestion  coupled  with the NEA’s power purchase agreements biased in the IPP’s favour.  One of the executives of the NEA Keshav Upadhyay  has painfully written in  the NEA  Bulletin dated Falgun 2067 touching on the subject of power tariff    “…energy rate of NEA plants would have further lowered but for stiff conditions in power purchase agreements like  take or pay  which forces the system operator to shut down NEA owned run-off-river plants…”.   During the dry months the load-shedding is now reaching up to 16 hours a day.  Even the midnight hours when the electricity demand is the lowest are not excluded from load-shedding. It is  quite obvious  that the NEA is now facing acute shortage of base load energy  which could have been  produced at exceptionally low cost.  Thus,  the NEA proposed Upper Tama-Kosi  hydropower with a huge peaking capacity of 456 MW,  which  would be mostly generating  high  valued  expensive peaking energy,  could not be an appropriate project to resolve the present power shortage crisis.


The Mini Upper Tama-Kosi  hydropower would  be  relatively a very small project which could  be  implemented   within a   short period  to provide quick relief from the present severe  load-shedding. The generated electricity would be very cheap and thus it might not be necessary to raise the electricity tariff within the coming few years.




Misuse of Existing Projects
All the NEA owned hydropower projects,  like the Kali-Gandaki, both Trisuli, both Marshyangdi, both Kulekhani and others are  capable  to run at full capacity even during the dry season periods.  They  have  been built at enormous cost to supply electricity to meet the demand for peaking. Obviously,  the generation cost of such peaking energy is always very high. Unfortunately at present the full capacity  of these hydropower projects built  to generate high  valued  peaking  energy has  not been fully utilized during the critically important dry season periods.  They are now  operated to  produce   a  very large  proportion  of cheap energy to meet  the demand for base load.   Thus,  the  reservoirs, high barrages, turbines, generators, transmission lines and civil structures provided  to generate and transmit peaking energy have not been utilized to the full extent. It is one of the reasons why the generation cost of the NEA produced electricity  is high.


The generation cost of the peaking energy is about two to three  times more expensive than that of the energy supplied to meet the demand for  base load.   A  fifty percent proportion of the base load and the peak load capacities of the power stations operating in a power grid  is normally considered to be optimum mix. It implies in our case that the overall firm generating capacity of our power grid should have already grown very high on top of the existing 450 MW firm capacity ( 400 MW peaking capacity  and  50 MW base load capacity)  in order to effectively use the additional peaking capacity of the NEA proposed 456 MW Upper Tama-Kosi project.   Thus, it would be too uneconomic under present circumstances  to implement  a hydropower project suitable to produce excessively large peaking power such as the 456 MW Upper Tama-Kosi project.


Danger of  GLOF
There are several rapidly growing glacier lakes near the project site in Tibet.  The great  risk of glacier lakes outburst floods (GLOF) to high gated barrage  and other structures of the NEA proposed Upper Tama-kosi project  should not be underestimated. We already have a bitter experience of the 1984 Digcho GLOF  when the Namche hydropower built on the upper reach of the Dudh-Kosi river was completely washed away.


The reconstruction cost could be too much if the barrage and intake structure of the NEA proposed Upper Tama-Kosi project would be damaged by big GLOF. Power supply would be suspended for a very long time which would have terrible consequences for the economy of entire country.


The Mini Upper Tama-Kosi project would be  having only ungated simple weir across the river.  The GLOF would cause only limited damage to the weir.  The damage can be repaired within a short period  at a relatively  small cost.


Seepage through Reservoir floor
It is reported that the reservoir of the NEA proposed Upper Tama-kosi project to be built  on the flat reach of Tama-kosi is made of 300 meters high fill materials from landslides  over the original  river bed  that  had dammed the river.  There is a great possibility of excessively large seepage  of water from the reservoir.  As a result of such seepage, there can be significant reduction in electricity  generation in dry season.


The mini Upper Tama-kosi project would not require the provision of a reservoir.  The question of energy losses resulting from the seepage  through the floor of the reservoir does not arise.


In Conclusion
The Mini Upper Tama-Kosi project can play pivotal role in bringing about quick relief from the present load-shedding crisis  and   also in holding down the electricity tariff.

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