Prefeasibility Study of Upper Khudi -A Hydropower Project

CE1.1.1 This project entitled “Prefeasibility Study of Upper Khudi -A hydropower project” is one prepared by group of five students in partial fulfilment of requirement for the bachelor’s degree in civil engineering. This project was carried out at Kantipur Engineering College, Dhapakhel, Lalitpur, affiliated to Tribhuwan University. Our team comprised of five members and the project itself was supervised by Er. Baburam Bharadwaj (Project Manager of Khudi hydropower limited)

CE1.1.2 Being the final year project of our engineering program, the timespan for this project was 1 year. We worked on it from June 2010 to November 2010. During this period, we presented the proposal, conducted the feasibility analysis, project analysis, project design, project defence, final presentation and final report. I was the team lead for my project and was a dedicated member from start to finish

CE.1.2 Background

CE1.2.1 As the name suggests, “Prefeasibility Study of Upper Khudi -A hydropower project”, is prefeasibility study aimed to use the theoretical knowledge we had from out text books to better understand the feasibility and optimization of the design of small scale hydropower project centered on Upper Khudi River in Lamjung district of Western Nepal. Majority of Nepalese households rely upon hydropower for their energy needs. So, developing small scale hydropower energy plants can be very efficient energy solutions as the rivers in Nepal are mostly mountain rivers with enough water throughout the year.

CE1.2.2 Khudi River has an average slope of 1 in 30 with gravels and boulders forming the river bed. It has a high sediment transport capacity. Upper Khudi Hydropower Project is a run of the river type hydropower scheme designed to produce power using the discharge of the Khudi River. It begins from the confluence of two Rivers, Sundar Khola and Khudi Khola. The catchments area of the River is 133 km² at the Department of Hydrology & Metrology (DHM) station located at Khudi Bazar, which when transformed to our catchments is 25 km², running from north to south.

CE1.2.3 The learning exercise included optimizing schemes per project capacity, sizes of hydraulic structures, penstock and electromechanical equipment and check the sensitivity analysis for the financial parameters which comprised of a significant result of in this feasibility analysis report. The study shows the feasibility of project with sufficient alternatives. We made sure we followed all the organizational rules and regulations of the University as well as the Hydropower Project.

CE1.2.4 The project was divided into five parts namely Data collection, Design and modelling, Cost estimation, Project planning and scheduling, Economic and financial analysis. Each member of the team was given one sector each as a main area of study and was responsible for the literature review of that part. I was given the Project planning and scheduling and the Design and Modelling part.

CE1.2.5 Organisational Chart

CE1.2.6 Project Objective

The objective of this study is to find the best project alternative and carry out the pre-feasibility study of the same. The main objectives are highlighted below:

• To be acquainted with the various aspects of hydropower planning and development.
• To find out the feasibility of project
• To know about the major components of the hydropower project.
• To select the best project alternative.
• To carry out the engineering design of hydropower components.
• To calculate the power and energy generated from the project.
• To carry out the quantity estimation and their cost.
• To prepare implementation schedule of the project.
• To carry out optimization of project capacity and components.
• To carry out financial analysis and sensitivity analysis of the project

CE1.3 Personal Engineering Activities

CE1.3.1 I have always been passionate about renewable energy and it is the main reason I took engineering as my career. In the context of Nepal, hydropower energy has a lot of scope. Most of the country in the upper hilly and mountainous parts are deprived of energy which is not a hard goal to achieve if small-scale hydropower projects implemented. I consulted my friends to form a group of five. We prepared the proposal to study for a hydropower project that could be used for a real project in the future. Then we prepared the proposal and submitted to the Dept. Of Civil Engineering with a detailed timeline graphed in a Gantt Chart. We consulted with the head engineer designated for this project and proposed that we would submit a study that could somehow facilitate the funded government project. He agreed to help us in every possible way and agreed to become our supervisor.

CE1.3.2 Before we started, we decided that we visit a similar small scale hydropower project. We drove to a similar hydropower project that powered a small city called Banepa east of Kathmandu. We talked to the authorities and they allowed us to walk through the entire project and see the dam, the turbines control room, and allowed us to take the specifications of the turbine so that we could have a rough idea of what equipment we had to choose to prepare the analysis of the hydropower project we had to do the project for. I also conducted weekly progress meetings with the team and supervisor to tackle any hurdles that we faced. We consulted with senior professors about my problems and ideas.

CE1.3.3 The entire work of this study is done by desk Study and field visit and survey by minor instrument such as Tape, and Abney level etc. All the data and information available from different sources were carefully analyzed to perform the preliminary study of all the necessary components. For the hydrological study of the project, mean monthly discharge of 13 years’ records of Khudi Khola at Khudi Bazar station (439.3) are obtained from DHM and analyzed using catchment area correlation method to find necessary hydrological parameters. Topographic maps (1:50000) of proposed site was studied for the allocation and design of civil as well as electro-mechanical components of the project.

The methodology employed to undertake the study were desk study and map study, field survey and social interaction, literature review, hydrological analysis, screening and selection of the best alternative, hydraulic design of the components of the chosen alternative, cost analysis and preparation of bill of quantities and finally report preparation and presentation.

CE1.3.4 The topography of the site is steep and rocky and thus we proceeded deciding that tunneling is the best possible alternative for waterway. As I was given the responsibility of design and modelling, I am explaining what the engineering design from the headwork to the penstock is comprised of in brief.

CE1.3.5 The headwork was located at 1290 m elevation. The trench weir was provided for diversion of flow to the intake and passage of high flood water. For design of the weir with length 10m, the design flood is taken as 40.073 m³/s for hundred years-return periods. The trench size has been calculated considering 50% of the trash rack is clogged and the design discharge will be conveyed. The intake was designed to allow abstraction of water from the source with as little sediment as possible, thereby minimizing maintenance and operational costs and providing some measure of protection against damage too (e.g. blocking of the conduit by incoming sediment and debris).

A.) Design Aspects of Gravel Trap and Settling Basin: The main design principle of the gravel rap was that the velocity through it should be less than that required to move the smallest size of gravel to be removed. Since the water abstracted from sediment loaded river not only reduces the capacity of the conveyancesystem but also damages the hydro turbines, thereby causing operation and maintenance problems. To cope with economy of energy generation from this, I wanted to design and construct a settling basin before water enters the plant, which helps to limit the entry of sediment into the plant by trapping the particle size greater than 0.2 mm.

B.) Headrace Tunnel: The shape as well as the dimensions of the tunnel should be selected such that it should be readily accessible from every direction for control, maintenance and repair. In pressure tunnels operating under high heads, the provisions of lining of concrete (PCC or RCC) and even steel lining including steel pipes may be embedded. To reduce construction costs, relatively high flow velocities should be permitted in tunnels, higher ones than those of open canals.  In addition to this I also calculated Friction losses Darcy Weisbach formula. The resulting dimension of the tunnel after all analysis was Inverted D shape 2m in diameter and 1500 m in length.

C.) Surge tank: A surge tank is generally constructed immediately prior to penstock or pressure shaft so as to damp out the oscillation in water level as soon as possible and to store water during load rejection until the new velocity has been established. Final design composed of a circular surge with diameter 2 m and height of 13.5 having upsurge and down surge of 6.256m and 4.704 m respectively.

D.) Penstock: Penstock is usually the pipeline in between surge tank and turbine inlet. Penstock may be low pressure or high-pressure penstock. Usually it is high pressure. The materials used are usually of steel, reinforced concrete. The pipe diameter and the thickness are such that the stress in steel computed from hoop stress criteria is well within the allowable limit. The hoop stress developed is given by the thin cylinder theory. I design we used inclined underground shaft made of mild steel.

E.) Turbine: To maintain the supply even in peak load conditions, two units of Pelton turbines with horizontal Shaft are in housed in the Powerhouse. Two units of generator are used to generate electrical energy. Turbine was selected on the analysis based on available head and design discharge.  Two units are provided for continuation of supply on maintenance of one unit also.

Also, a tailrace was set to convey the water leaving the power plant back to the river. The tailrace should be designed to maintain the water surface at the elevation specified by the turbine manufacturer and to protect the power plant against flooding by the expected design flood level in the river.

E.) Power generation: A 66 KV transmission line has been proposed for the safe and economic transmission of the generated power, along a length of 30 Km for the interconnection of the supply to the national grid at Udaypur.

CE1.3.6 The subjects that I was enrolled in the undergraduate like fluid mechanics, hydraulics, water supply, engineering hydrology, survey, engineering drawing etc. helped me a lot to complete and prepare my project. I tried to utilise all my knowledge in utmost way to realise a hydropower project. While doing this project, I not only experienced the applied part of civil and hydropower engineering but also learned a lot of practical skills like communication skills, time management, project presentation and team work. During this project interval, being a group leader I had to solve not only my own but I have to help my group members in technical and other calculation part as well.

CE1.3.7 Me along with my team members worked together very hard and could complete the project in the defined time. We could study the pre-feasibility of Upper Khudi and prepare the final report in the designated time. After the completion of this project, I felt a big rise in my confidence level as an engineer and I felt I could easily tackle the obstacles by studying about it, applying the solutions in real life problems. We used various software like MS-Word, MS-Excel, MS-PowerPoint to document the report, prepare presentations and analyze available data. I feel like my reporting skills, drafting skills and drawing skills also utilised professionally over the course of this project.

CE1.4 Summary

Undertaking this project helped me to use my theoretical knowledge on practical and real life work scenarios relating design and construction of a hydro power plant. We were very happy that the project met all the initial objectives. The project has a conventional B/C ratio of 2.1 and modified of 2.13 and IRR of 23.4%. The total cost of the project is NRs 605,089,628.69 and cost per kilowatt is within the range of prevailing Cost per KW for the projects recently built in Nepal.  Hence, the project was financially, technically, socially and environmentally viable, and can be forwarded for further study. In a nutshell, I was efficiently and successfully able to undertake, manage and complete the project ensuring that it met all its objectives within a designated time frame.