EFFECT OF RAINFALL ON HYDROELECTRIC POWER GENERATION IN NIGERIA: CASE STUDY OF KAINJI HYDROELECTRIC GENERATION STATION

Abstract

Energy is one of the most basic needs of all people in the world and Electricity is the cornerstone on which every modern economy depends. Hydroelectricity in its own quota contributes about 19% of the World electricity consumption today and 27% to Nigeria’s national electricity grid. Hydropower has among the best conversion efficiencies of all known energy sources (about 90% efficiency, water to wire). Hydropower is a renewable form of energy and currently accounts for around 68% of the world total renewable energy production. Hydroelectricity gets it renewability from rainfall. The use of dam in hydroelectricity is for the purpose of creating head and at the same time storing up water in its potential energy form in periods of rainfall for sustained energy generation even in dry season. Energy generation by means of water is dependent on two main factors: Head and Flow. In a storage-type hydropower system, the higher the head, the higher the energy generated. Increase in head is as a result of increase in headwater elevation and increase in headwater elevation depends on high inflow which derives its volume from rainfall. Months of highest rainfall are generally associated with high inflow and high discharges. A study on the effect of rainfall on hydroelectric power generation in Nigeria: a case study of Kainji dam has been carried out. Monthly rainfall values were used. Also used are daily data of energy generation values, headwater elevation values and tailwater elevation values for a period of six years, from 2006 – 2011. The methodology involved correlation analysis and comparison of the mean annual values of the variables used. The results showed that peak rainfall occurred within the months of July – October in different years. It further revealed that the correlation between monthly headwater elevation and rainfall, and monthly energy generation and rainfall, were of none direct inversely related. The monthly comparison of headwater elevation, energy generation and rainfall showed that the months of highest headwater elevation corresponded to months of highest energy generation which were in dry seasons. Contradictorily, the years of highest/lowest annual values of rainfall corresponded to that of highest/lowest annual headwater elevation values but not so for energy generation. The annual comparison in contradicting the monthly result proves that on annual basis, high headwater elevation depends on high rainfall. It was discovered that nonconformity of highest/lowest annual energy generation with highest/lowest annual headwater elevation and highest/lowest annual rainfall can be traceable to consistent plant breakdown within the years. Also, the nonstrategic release of water from the dam during the months of peak rainfall over the years studied have been the reason for low headwater elevation and low energy generation within these months. However, after having found out that the anomalies obtained in the results and the noncorrespondence between the monthly variations and annual variations were as a result of weak operational policies and under-performance of dam managers/operators in optimizing all year round appreciable energy generation. I recommend that there should be consistent maintenance and were applicable replacement of turbines/plants so as to have all the plants functional in all seasons, thereby increasing turbine discharge and reducing spillage in periods of high rainfall/inflow and also the operational policy the dam with respect to water release should be reviewed in a way to optimize rainfall in its season.