Assessment of Hydroelecric Potentials of Owu and Ero-Omola Falls in Kwara State, Nigeria
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ASSESSMENT OF HYDROELECTRIC POTENTIALS AT THE OWU AND ERO-OMOLA FALLS IN KWARA STATE B. F. Sule K. M. Lawal K. A. Adeniran TECHNICAL REPORT NO. 7 ISBN: 978-978-915-055-7 NATIONAL CENTRE FOR HYDROPOWER RESEARCH AND DEVELOPMENT ENERGY COMMISSION OF NIGERIA UNIVERSITY OF ILORIN, ILORIN, NIGERIA MAY, 2011 Assessment of Hydroelecric Potentials of Owu and Ero-omola Falls in Kwara State, Nigeria TABLE OF CONTENTS 1. EXECUTIVE SUMMARY 3 CHAPTER ONE 1.0 Introduction 5 1.1 General Introduction 5 1.2 Sources of Energy 6 1.3 Statement of Problem 6 1.4 Why Small Hydro 7 1.5 Aim of the Study 7 1.6 Objective of the Study 7 1.7 Physical Characteristics and Description of the Study Areas 7 1.8 Demographic Data 8 2. CHAPTER TWO 2.0 Theory of Hydropower Generation 10 2.1 Energy Production 11 2.2 Hydropower System 14 3. CHAPTER THREE 3.0 Study Approach and Technology 14 3.1 Data Collection 14 3.2 Determination of Energy Demand 14 3.3 River Stage Measurement 16 3.4 Measurement of Discharge 16 4. CHAPTER FOUR 4.0 Field Output and Data Analysis 17 4.1 Introduction 17 4.2 Instrumentation Details 17 4.3 Stream Discharge 19 4.4 Development of a Monthly Flood Rating Curve 19 4.5 Extension of Streamflow Data at Ero-omola Fall 23 4.6 Model Development 25 4.7 Determination of the Required Reservoir Capacity 28 4.8 Evaluation of Sediment Load or Sediment transport 29 5. CHAPTER FIVE 5.0 Potential Energy Assessment 31 5.1 Potential Energy Assessment of Ero-omola Fall 31 5.2 Potential Energy Assessment of Owu Fall 33 5.3 Hydropower Power Demand 34 6. CHAPTER SIX 6.0 Financial Justification 35 6.1 Introduction 35 6.2 Engineering Economics 35 6.3 Economics Analysis 35 6.4 Cost of Generation Per Kilowatt 36 6.5 Internal Rate of Return 36 6.6 Amortization Analysis 36 7. APPENDIX 1 40 APPENDIX 2 41 APPENDIX 3 48 APPENDIX 4 49 APPENDIX 5 55 APPENDIX 6 56 APPENDIX 7 57 APPENDIX 8 58 APPENDIX 9 59 APPENDIX 10 60 APPENDIX 11 61 8. REFERENCES 61 Page 2 Assessment of Hydroelecric Potentials of Owu and Ero-omola Falls in Kwara State, Nigeria EXECUTIVE SUMMARY 1. General The study for the assessment of potential hydropower development of Owu and Ero-omola Falls commenced effectively by 20th of June, 2009. Various site visits were undertaken to facilitate gauge installation and hydraulic head survey. Gauge readers were recruited to monitor gauges, with provision of a motorbike for the gauge reader at Owu Fall, due to long distance of site from urban centre. Gauge readers were effectively engaged by 26th of November, 2009 and have since continued to monitor the gauge till date. Signboards were installed to indicate ownership of the measuring instrument at both sites. Ero-Omola has recorded about 450 days (15 months) of records while Owu Fall has about 217 days (7months) of records. The fewer months of records were due to conflict between the gauges readers employed for the site. Discharge measurement from both sites were evaluated to generate the discharge rating curves on excel programme and to establish the minimum and the maximum water level. 2. Discharge Computation Method There are different methods of determining river discharge. The choice of computation methods depends upon the equipment and observational method used during the gauging, flow conditions at the time of gauging, type of stream and the accuracy required. The arithmetic method is preferred, because it offers sufficient accuracy and quicker to perform than other methods. For the purpose of this report the Mean Section Method was utilized to evaluate the discharge. The raw data is presented in the annexure to this report. 3. Hydropower Potential a. Owu Fall with a hydraulic head of 95.5m has a potential hydro capacity of 8.81MW and annual generating capacity of 15425.12MWh. The minimum flow available for about 100% of the time from the flow duration curve is estimated at 9.9m3/s. Therefore a single pelton turbine is recommended. The total amount of energy so generated can be sold to National grid is estimated at N216,091,680.00 at N14.00/kWh. The internal rate of return was however negative. Owu Fall has a difficult terrain with relatively low runoff but consistent runoff yield. It is therefore suitable for only runoff river system as it is practically difficult to impound water behind the Fall. More so the distance to the 33kva National Grid at Omu Aran is about 189km, while that of Ero-Omola is just 48km. b. Ero-Omola Fall with an averages discharge of 22.8m3/s and a hydraulic head of 59.4m has a potential hydropower capacity of 8.64MW. The 100% flow rate from Ero-Omola may be bifurcated by 3 unit draft tube into the turbines at 7m3/s each. The total annual energy was estimated at 15137.28MWh at an economics cost of N211,921,820.00/annum using the NIPP multi-year tariff order of N14.00/Kwh. The total amount derivable from the power generation excluding other charges amount to about N213million with an internal rate of return (IRR) of 18.00%. This IRR although lower than the prevailing interest rate of 21% is still acceptable on the premise that, the present commercial interest rate in Nigeria is relatively high. Ero-Omola water Page 3 Assessment of Hydroelecric Potentials of Owu and Ero-omola Falls in Kwara State, Nigeria year is between April to March with a two to three month break of hydrological cycle. It is therefore necessary to provide a reservoir, sufficient enough to regulate flow for the turbines and to provide domestic and irrigation water supply to the host communities downstream. This off course is an additional cost to the investor. The benefit/cost ratio is however encouraging. 4. Constraints The Centre must collaborate with State Government to see that the only access roads to Owu Fall are rehabilitated. The deplorable condition of the road makes it un-passable during the rainy season and make site visit difficult. The present security situation of Owu site does not encourage installations of expensive instrument for now, due to constant vandalization, removal or theft. 5. Financial Positions The total budgetary provision for the two sites would have been draw down completely by the end of April 2011. It is therefore important to provide fund for the salary and wages of the gauge readers beginning from May 2011. The budgetary provision for the two site is estimated at N650,000.00 each, bringing the total sum required annually to about N1,300,000.00(this includes salary and wages of gauge readers, fuelling of motorbikes, instrument maintenance, site visits etc.). This request becomes necessary if the centre is to continue to sustain continuous and uninterrupted data acquisition of both sites. 6. Recommendations a. The next phase of this study is to provide detail topography of the site and to locate position of power house, fore bay, penstocks with detail engineering drawing and subject the overall cost to economic analysis. b. Thereafter this report will be publicly presented to provide the necessary information to investors to appraise and executes the project. c. An automatic data logger should be provided at Ero-omola. This is to minimize research cost and expenditure on data acquisition. Self-recording gauges that maintain a continuous record of stage are based on various types of sensors. The three most commonly used types of sensors are float- driven, pressure, and ultrasonic. In a typical installation of a float-driven, water-level sensor, the vertical movement of a float in a stilling basin, resulting from fluctuations in water level, is translated by a mechanical movement or an electronic signal. Ultrasonic sensors use acoustic pulses to sense water levels either by contact or noncontact methods. Stage-discharge relations may have to be periodically updated due to changes in the hydraulic characteristics of a stream reach over time, caused by erosion and sedimentation, bank vegetation, and other changes. It is therefore extremely important to make provision for continuous regular site visits, whenever the need arises. Page 4 Assessment of Hydroelecric Potentials of Owu and Ero-omola Falls in Kwara State, Nigeria CHAPTER ONE 1.0 INTRODUCTION 1.1 General Introduction Power is a very important infrastructural development of a nation. It is widely believed that an appropriate level of energy generation has always gone hand in hand with industrialization and economic development. Similarly a functional energy generation system often serves as an effective tool for National Economic Development. The need for comprehensive studies of hydropower operation of large water resources system is increasing at rapid pace because of the increasing interest in all facets of resources use and management. Complexity of water resource planning, design and operations studies, demand for a mathematical procedure that will select the optimum sizes and characteristics of components to produce a desired result. Many failures of water related projects are due to project planning on the basis of inadequate hydrological data, due in part to two factors: a. Data which are not accurately measured b. Too short time series of hydrological data not allowing reliable estimates of system performance In the later case some scientist suggests the postponement of the project until more reliable and accurate data are available. Although this suggestion is theoretically sound, it however lacks the requirement and needs of engineering practice. A better way to solving the problem may be the use of hydrological data from synoptic station within the same catchment which in combination with available hydrological data may improve the planning results.