Performance analysis of an absorption power cycle for ocean thermal energy conversion

An absorption power cycle with two ejectors is proposed for ocean thermal energy conversion. The ammonia–water is used as the working fluid. The ejectors are driven by vapor and solution from the sub-generator. Based on the first and second law, the mathematical model for this cycle is developed and theoretical analysis is conducted to evaluate the effects of thermodynamic parameters on the performance of this cycle. Results show that the absorption temperature is increased by 2.0–6.5 °C by employing the two-stage ejector sub-cycle, which indicates that this proposed cycle can be driven with a lower temperature difference. Further, the thermal efficiency, net thermal efficiency and exergy efficiency of this cycle can reach to 4.17%, 3.10% and 39.92% respectively. Besides, the generation pressure, the heating source temperature, the solution concentration, and the expansion ratio, as well as the entrainment ratio of the first stage ejector have significant effects on the absorption temperature, the thermal efficiency, the exergy efficiency and the exergy loss of this cycle. In addition, 49.80% of exergy loss in this proposed cycle occurs in the generators and reheater, followed by the ejectors of 36.12%.