Realization and optimization of a binary cycle power generating system using a low-grade heat source

Abstract

Abstract The low-grade heat source thermoelectric system generates electricity using a working fluid at temperature lower than 100°C or gas at temperature lower than 250°C. The system is usually composed of binary (1 + 0.5 × 2) cycles. Positive net output power or high efficiency of the system can only be feasible after optimization. Most works focused on the cycle of working fluid and treated the power consumptions of the other cycles as constants. However, both cycles should be comprehensively considered in optimization, especially when power consumptions vary with working conditions. This research selected an organic Rankine cycle thermoelectric system for demonstration. A thermodynamic model conforming to the target system was built. The temperature of the heat source and the pressure at expander inlet were tailored using the genetic algorithm. The best efficiency is 1.89%, and the largest net output power is 5.80 kW. Both results are better than those (efficiency = 1.59% and net output power = 5.34 kW) from benchmarks under the highest temperature of heat source and inlet pressure among possible working conditions. Experimental results are provided for both validation of the model and confirmation of the superiority of optimization results.