Thermo-economic comparative analysis of a simple and cascaded organic Rankine power plants fired by rice husks

Abstract

The application of organic working fluids in the Organic Rankine Cycle (ORC) has been demonstrated to be an attractive option for shifted integrated power and heat production. The procedure allows for the implementation of low-temperature heat sources, which provides advantages in small-scale uses. This study models the organic Rankine cycle for use with rice husk waste from a typical agricultural farm. The comparative analysis of agro-fired simple and cascaded organic Rankine power plants. Toluene and R245fa were considered as the working fluids for both simple and cascaded ORCs. Basic thermodynamic and economic governing equations were utilized in the analyses and embedded in the Engineering Equation Solver. The net powers, energy, exergy, and economic analyses of the two ORCs form the basis for comparison. Afterward, sensitivity analysis was carried out to ascertain the effects of variability of pertinent parameters on the plants. Results revealed that the net power output, thermal and exergy efficiencies of the simple and cascade ORC plants were 1.154 MW, 15.53% and 20.38%, and 1.599 MW, 21.51%, and 28.23%, respectively. The largest exergy destruction rate was obtained in the combustion chamber (1531 kW), and the least exergy destruction was recorded in the recirculation working fluid pump (1.073 kW). The simple ORC showed better economic performance as reflected in the unit cost of energy of 35.11 N/kWh as against 37.68 N/kWh of the cascaded ORC. The proposed energy system has the potential for a viable business enterprise based on the favorable Federal Government of Nigeria's fiscal and energy policies.