Exergetic and thermoeconomic analyses of the rice-husk power plant in Thailand

Abstract

The purpose of this study is to analyze a rice husk power plant, and consider the efficiency of the power plant through both the first law and the second law of thermodynamics. The energetic and exergetic performance criteria such as thermal efficiency, exergy efficiency, and exergy loss have been found to be useful methods in design, evaluation, optimization and improvement of thermal power plants. The exergetic efficiency of a power plant shows that the boiler is the major component contributing to total loss, with its exergetic efficiency of 30%, while the steam turbine has the exergetic efficiency of 76%. The study also evaluates the economic consideration of a rice-husk fired power plant for heat and power production. The capacity of the plant is 576 tons paddy/day. The total load of thermal energy consumption is 1,062 MJ/ ton paddy and the electrical energy consumption of the rice mill is 6,518 MWh/year. The total capital cost of the rice husk-fired cogeneration is US$ 1.2 million (1 US$=35 Baht). The capacity of the back pressure steamfired boiler is 18 tons/hour of steam and 25 bar (absolute), 400°C. The rice-husk fired cogeneration can generate power of 1,432 kWe. Economic analyses in terms of net present value (NPV), simple pay-back period (PBP), and internal rate of return (IRR) are also evaluated. Results show that the rice husk-fired cogeneration has NPV of US$ 0.303 million /year, PBP of 3.7 years and IRR of 27%. Results of the study also show that rice husk-fired cogeneration is beneficial to power generation.