Benefits of construction of khersan III double curvature dam & H. E. P. P in iran

1. INTRODUCTION

With regard to the increase of power consumption in different parts of demands such as domestic, commercial, industrial, etc., the power generation system must be extended. In this process, the method of increasing the generation of the electrical energy is of vital importance.

In general, the power generating resources can be classified as thermal, hydropower and nuclear. 93% and 7% of energy of the country is being generated by thermal and hydropower resources respectively. The ratio of power generation in the world is 64% (thermal), 19% (hydropower) and 17% nuclear.

It should be mentioned that the energy generating resources are limited. On a way that the resources of coal, oil and gas, in Iran, could be used up to 120, 100 and 500 years from now on respectively; whilst, water as an everlasting source of energy is a reliable source for investment and exploitation.
The exploitation of water as a potential source of energy would have the following advantages:

• 
  The hydro-electric power plants have long life over 50 years
  

• 
  These power plants are relatively more efficient than the other power plants
  

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  They would cause no environmental problem
  

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  They impose lower maintenance costs rather than the others
  

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  The exploitation of hydro-electric power plants makes it possible to have multipurpose usage of the water resources
  

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  They have recyclable consumption resources
  

On the other hand, the phenomenon of global warming has caused the whole world to use water as the energy generating source. The greenhouse gases have substantial effects on global warming. Provided that no measure is taken to control and reduce Carbon Dioxide, the temperature of the earth would be raised approximately to 1.5°C to 4.5°C in 60 years.

2. POWER GENERATION HISTORY IN IRAN

The power consumption activities in Iran were commenced at the end of 12^th century of Iranian calendar. In 1282 (1903 Gregorian calendar), the first power generator was brought into operation in Iran. After elapse of two years, a two-timer steam piston engine equipped with three steam containers was brought into operation at the beginning of Cheragh-bargh Street of Tehran.
This machine was a generator made in Germany with the capacity of 400kW and the output of 380V. Gradually, the cities were expanded; huge industrial units were established; and the domestic demands caused the separated small generators to be changed to the power generation units with high capacity which were established by the governments.

3. INTRODUCING KHERSAN III H.E.P.P

In 1992, the studies related to the potentiality of Karun catchments tributaries were started and in these studies, Khersan River was found as one of the important rivers of this catchment. These preliminary studies were resulted in introducing three dams in cascade named Khersan-I, Khersan-II and Khersan-III dams.

Khersan-III Dam Site is located in the Upper Khersan River in the vicinity of Atashgah Villages 50km form Lordegan (Chahar Mahal-o-Bakhtiari Province in south-west of Iran). This River is flowing in north-west Hillside of Zagross Mountain Folded zone.(Figure 1)

Figure 1- Satellite Image of Khersan Catchment

4. TECHNICAL SPECIFICATION OF THE PROJECT

Khersan III project is the first double curvature concrete arch dam with 180 meters height and 402 meters crest length on Khersan River which has a reservoir capacity of 850 MCM with the main purpose of power generation. The power house with three units of Francis type turbines each with an installed capacity of 315 MW located on the left bank of the river. The general layout of dam and appurtenant structures are shown in figure 2.

Figure 2- General Layout of the Project
The diversion system includes the excavation and concrete lining works of a tunnel of 650m length with the complete diameter of 13m. The bottom outlet System includes two outlets in the dam body. With regard to the extreme height of the Dam as well as the high flow velocity in the outlets, there have been considered different levels for them. The lower outlet is located at the level of the 50 years sediments. The Max discharge capacity of the bottom outlets in full opening conditions, when the reservoir is at normal supply level (1418 masl), would be equivalent to 755 M³/s. In this case, the Max discharge capacity of the outlet located at 1330 masl would be 395 M³/s and the Max discharge capacity of another one would be 360 M³/s. The power tunnel inner diameter is 8.7m; the diameter of the steel lining is 7m & 5m. The total length of the conduit is approx 650m.

5. Fundamentals and Assumptions of Economical Calculations

5.1 General
The benefits and project costs are assessed from the view point of the whole society using the social cost benefit framework. In this part, the entire lost or attained opportunities are evaluated. In other words, the project advantages and disadvantages, comparing with the determined objectives, are considered as social benefit and social costs respectively.

So as to avoid complexity and to follow the study limitations, in the assessments, attention has been given to the significant economical-social aspects of the project. Therefore, for recognizing and classifying the effects and consequences of the project, the matters were assessed which could be evaluated and converted into financial values.

In the analysis framework of "benefit – social cost", at first the evaluated costs and benefits are taken into consideration. Nevertheless, there would be required a series of calculations for escalating and comparing the costs and benefits belonged to different years. In this respect, it is required to transfer the whole tariffs and benefits to a base year using the principals and techniques of engineering economy. In these assessments, the base year, construction finishing time of the dam, appurtenant structures and power station has been taken into consideration.

5.2 Interest Indices in Use

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  Ratio of Benefit to Cost (B/C): This coefficient indicates the economical efficiency of the project, where in this case is 1.82 (based on 8% interest discount rate)
  

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  Net Benefit(B/C): this index indicates the impact of the project on the increase of national income, where in this project amounts to 29.9 billion Rials (about 31 million US dollars)
  

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  Rate of Internal return: indicates a rate which makes the ratio of the benefit to cost equal to one and their subtraction equal to zero. In this project the IRR equals to 17.7 %.
  

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  Cost of 1KWh energy: indicates the total price of the generated power considering he project total costs which equals to 355 Rials (about 32 US cents)
  

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  Cost of 1kW installation capacity: indicates the total price of each 1kW installation capacity in power station which equals to 14.2 million Rials (about 1450 US dollars).
  

These studies have been performed regarding the fixed prices. In other words, it has been presumed that the effects of inflation rate on the benefits and costs are the same.

6. MAIN POSITIVE IMPACTS OF THE PROJECT

1. 
   Generation of 1014 GWh energy,
   
2. 
   Regulating Khersan River discharge on a way that the produced energy will be increased at downstream dams over than 10 %
   
3. 
   Stability of the electricity network
   
4. 
   Economizing in the use of fuels
   
5. 
   Economizing on the social expenses of the air polluters
   
6. 
   Controlling the Khersan River floods,
   
7. 
   Creating employment and job opportunities and labour skills for reducing poverty in vicinity towns
   
8. 
   Providing suitable area for developing the aquatic sports, tourists, fish farming etc.
   

7. 
   CONCLUSIONS
   

Khersan III hydroelectric project was put into construction with the main target of producing the electric power due to high demands in Iran's growing economy while it's final phase design studies were underway. The topography of the region shows the construction of a double curvature conventional concrete arch dam is the best choice. Economic appraisal studies of the project indicate a benefit to cost ratio equal to 1.89 which demonstrates it's attractiveness for starting construction activities. Another special aspect of this project is producing 1014 GWh energy per year and supplying water for agricultural consumes due to huge water reservoir which equals to 850 MCM which makes safe down stream side from huge floods of the basin.

[1] Mahab Ghodss Consulting Engineers, "Socio-economic studies of Khersan III Project." 2002

[2] Abanpajouh-Stucky JV , " Economical Overview of the Khersan III Project, 2008

[3] Abanpajouh-Stucky JV , " Technical Report of the Khersan III Project, 2005

SUMMARY

Hydro power plants are the most compatible types of all power plants with the ecological system which may also act as a multipurpose scheme to control floods and supply energy and other positive side effects like renew ability, longer life time and the existence of numerable hydro potentials in the country.