Resolving Present Power Shortage Crisis

February 16, 2006
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By DR. AB THAPA

The Nepal Electricity Authority (NEA) has already started load shedding. Now we are having daily interruption of power supply in rotation starting from early morning to late evening hours. The duration of the daily power supply cut is about 2.6 hours. The nature of the load shedding indicates that the NEA is now experiencing shortage of capacity (KW) as well as energy (KWh).

The power shortage crisis is going to deepen in the years to come because the demand for electricity in our national grid with a total firm capacity of about 500 MW is expected to grow steadily at an annual rate of at least about 5 to 7 percent. Except for the 70 MW Middle Marshyangdi Project, other major new power projects are nowhere near which would have come into operation within the next 5 to 7 years. Thus we are now being dragged into a whirlpool of deep power shortage crisis due to our shortsighted planning. However, there might still be a way to soften the impact of this power shortage crisis if we launched a programme on war footing to utilize the full potential of the existing Kulekhani storage reservoir and hydropower stations ( Kulekhani 1 & 2 hydropower) to generate extra power by diverting from Kathmandu valley the surplus flow of the Bagmati river and later on the Melamchi river into the Kulekhani reservoir. The design of the proposed Kulekhani 3 Hydropower should also be reviewed and perhaps its capacity might have to be raised to about 150 MW to meet the steadily growing peak load demand if it is decided to divert the Bagmati water into the Kulekhani reservoir. .

The Kulekhani Reservoir and Power Stations

It is reported almost every year in local newspapers that the electricity generation of the Kulekhani hydropower stations is going to be reduced by a substantial margin because the Kulekhani storage reservoir is half-empty at the end of the monsoon season, with the result that the NEA would be forced to resort to load shedding in the coming dry season. This problem would certainly be solved if the surplus water from the rivers in the Kathmandu valley is pumped into the Kulekhani reservoir to be stored for the supply to the Kulekhani hydropower stations in the dry season.

The Kulekhani reservoir operation rule for the Kulekhani-1 with an installed capacity of 60MW is framed by a basic discharge pattern of 6.2 cum./sec. in the dry season from December to March and 2.1 cum./sec. in the wet season from April to November. The former is designed to generate four-hour peak power using the maximum discharge of 13.1 cum./sec. and 20-hour base load using 4.8 cum./sec. The latter is to utilize 6.55 cum./sec. for the peak power and 1.21 cum./sec. for the base load respectively.

Available water for the Kujlekhani-2 power station with an installed capacity of 32 MW is comprised of the outflow from the Kulekhani-1 and the runoff of the Mandu river. The firm discharge of the latter with 90% dependability at the intake is estimated to be 0.2 cum./sec. both in winter and summer. Thus the maximum Kulekhani-2 discharge is designed to be 13.3 cum./sec.

Diversion from Kathmandu to Kulekhani

The Bagmati river water in surplus to the need in the Kathmandu valley could be diverted into the Kulekhani reservoir from a place near Chobhar gorge. Mean flow of the Bagmati river at Chobhar is quite abundant during the monsoon seasons. Even in the winter months of the dry season starting from December to the end of March when the demand for the electricity in Nepal is very high the average flow of the Bagmati is expected to be over 2 cum./sec. The half empty space of the Kulekhani storage reservoir ( with an effective storage capacity of 73.3 million cubic meters) could be utilized to accommodate about 20 million cubic meters monsoon season flow of the Bagmati river. Thus the Kulekhani hydropower could be provided throughout the 4 winter months additional 4 cum./sec. flow. Out of this total flow, the water drawn directly from the Bagmati would be about 2 cum./sec. and the stored Bagmati water would provide the remaining 2 cum./sec.

The diversion of the surplus Bagnati water from Kathmandu valley to the Kulekhani reservoir could be a very simple and at the same time the most cost effective proposition despite the fact that at first glance it might appear to be a somewhat complicated engineering task. Let us consider that we are going to draw about 4 cum./sec. Bagmati. water from somewhere near Chobar. It is explained hereinafter that the total power generation of the Kulekhani 1& 2 hydropower plants would almost be doubled by investing about US $ 20 million in the construction of the proposed diversion structures including a pumping station.

The Proposed Design

We might have to build a 15 MW pump station at Chobar to lift 4 cum./sec water to a height of about 300 meters which might be equivalent in height to the full supply level (FSL) of the Kulekhani storage reservoir. It is equally possible that instead of one big pump station we might need several small pump stations with a total capacity of about 15 MW if the topography does not allow to provide single stage pumping. A 15 km long waterway might be needed to carry the water into the Kulekhani storage reservoir out of it the length of the tunnel could be about 9 kilometers. The total cost of such diversion could be about US $ 20 million.

The construction of the proposed Bagmati diversion works could be completed within 2 years with one additional year for the initial preparatory works. The NEA might not require external foreign investment. It could mobilize its own resources to finance this project.

After the completion of the proposed Melamchi river diversion into the Kathmandu valley there would be substantial increase in flow of the Bagmati river at Chobar. As a result, the electricity generation of the Kulekhani 1&2 hydropower stations would be further increased.

Rationale Behind the Bagmati Diversion

The proposed Bagmati diversion could be implemented within a very short period to meet the ever growing demand for power in our national grid. The proposed diversion is going to be perhaps the most economic project because we do not need to invest on construction of the reservoir, power stations and transmission lines. We are going to utilize the existing power stations, reservoir and other structures. For pumping surplus monsoon period water from the Bagmati river into the Kulekhani reservoir we can use seasonal energy generated by our run-of-the-river hydropower projects. At present the seasonal energy is almost entirely wasted.

Kulekhani-3 Hydropower

At present the Kulekhani-1&2 hydropower stations are operating at a capacity factor of about 25 percent. After the diversion of the Bagmati into the Kulekhani reservoir the capacity factor of the Kulekhani 1&2 hydropower stations would be increased. So it would be desirable as soon as possible to implement the Kulekhani-3 hydropower also to fulfill the demand for very short duration peaking load. The capacity cost of the 75 MW Kulekhani-3 hydropower would be more than 2 times cheaper than then any other projects such as the Kali-Gandaki-A, Modi, Bhote-Kosi etc. Central location, proximity to existing transmission lines and highways are the added advantages in favour of implementing the Kulekhani-3 hydropower in very near future.

(Thapa specialises on water resources. This article is reproduced here courtesy SPOTLIGHT newsmagazine. Please send your comments to [email protected])

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