Determination of optimum unit capacities of future coal power plants in Sri Lanka

Abstract

In Sri Lanka, future generation plan includes number of coal power plants according to Long Term Generation Expansion Plan (LTGEP) prepared by Ceylon Electricity Board. Proportion of coal power generation is significant and hence their technology and unit size are important parameters when planning future coal power plants. Therefore, this study focuses on a methodology to determine optimum unit size of future coal power plants in accordance with LTGEP. System stability constraint is identified as the limiting factor for larger units over conventional 300 MW size. In order to determine the constraint, off peak demand forecasting has been performed for next 20 years. Out of two forecasting methods, multiple regression analysis method is selected and based on off peak demand forecast, stability constraint is determined. Technologies used for coal power generation are studies along with their advantages and limitations. High efficient supercritical technology is more focused and alternative options have been considered for proposed coal power units in LTGEP considering determined constraint. Accordingly, two cases are selected for financial analysis. Discounted cash flow analysis is carried out for each case in order to compare supercritical single unit instead of two equal sized advanced subcritical units. Due to long project life time, constant cost basis is used to minimize error of financial forecast. NPV, IRR and LOCE figures were calculated and sensitivity is analysed against fuel price and selling price. Results show that high efficient supercritical unit is more economical than smaller units even under partial load operation condition at off peak period. Therefore, high efficient supercritical plant is recommended considering other driving factors such as reduction in hazardous emissions, ash products and environmental factors. Furthermore, findings of this study can be used for other technologies as well.