BENEFITS OF CONSTRUCTION OF KHERSAN III DOUBLE CURVATURE DAM & H.E.P.P IN IRAN
Water Resources Engineer, Project Director of Khersan III Dam&HEPP,
Iran Water and Power Resources Development Co., Iran
Senior Geotech. Eng., Chief PhII Studies Engineer of Khersan III Dam&HEPP,
Iran Water and Power Resources Development Co., Iran
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
They impose lower maintenance costs rather than the others
The exploitation of hydro-electric power plants makes it possible to have multipurpose usage of the water resources
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.
There have been encountered natural disasters such as storms, floods and twisters as a result of the global warming. In addition, the raise in water level would cause lots of problems, namely protection of the beaches, submergence of the lands and making them briny.
Hence, the construction and exploitation of Khersan-III Reservoir Dam and HEPP was taken into account with the aim of generating hydro-electric energy.
2. POWER GENERATION HISTORY IN IRAN
The power consumption activities in Iran were commenced at the end of 12th 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
Khersan River Catchment is one of the tributaries of the Karun River Catchment. Most parts of this catchment are mountainous. Dena is the highest peak of this catchment with approx 4437m height; the mean height of this catchment is 2358m; its area up to proposed Location of Khersan-III Dam Site is approx 7733 km². The studies carried out on Khersan river have indicated this river has potential for the construction of three cascade dams with total installed capacity of 1250 MW and average energy production of 4000 GWh/year. Khersan III dam and H.E.P.P with the installed capacity of 315 MW produces 1014 GWh per year.
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
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
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)
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)
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 %.
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)
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.
Excluding the internal return rate, the other indices rely on the interest. In these assessments, the economical indices have been calculated by the rates of 8%.
Along the commissioning period there have been considered replacement costs and scrap value for the facilities with short and long terms effective lives respectively.
The total cost of the project estimated in 2008 amounts to about 4480 billion Rls (about 450 million US dollars).
6. MAIN POSITIVE IMPACTS OF THE PROJECT
Generation of 1014 GWh energy,
Regulating Khersan River discharge on a way that the produced energy will be increased at downstream dams over than 10 %
Stability of the electricity network
Economizing in the use of fuels
Economizing on the social expenses of the air polluters
Controlling the Khersan River floods,
Creating employment and job opportunities and labour skills for reducing poverty in vicinity towns
Providing suitable area for developing the aquatic sports, tourists, fish farming etc.
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.
 Mahab Ghodss Consulting Engineers, "Socio-economic studies of Khersan III Project." 2002
 Abanpajouh-Stucky JV , " Economical Overview of the Khersan III Project, 2008
 Abanpajouh-Stucky JV , " Technical Report of the Khersan III Project, 2005
The studies which were carried out in 1999 on the scheme of energy production in Iran indicated that near to 93 percent of consumed country energy is being supplied by means of fossil resources. Therefore making use of renewable energies in a more suitable economical condition could be an acceptable response to the problems which may be encountered with regard to the fossil fuels consumption.
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.
In south east of Iran Khersan river is one of the biggest origin of Khersan river and Khersan III dam and HPP is the first dam on this river. In this article some important aspects of this project and its influence in energy production has been discussed.
Key words: Khersan III Power Plant,