A modified ammonia-water power cycle using a distillation stage for more efficient power generation

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An ammonia-water power cycle with a distillation stage is proposed, two Kalina cycles and one Organic Rankine Cycle (ORC) are selected for comparisons under two scenarios: medium (346 °C) and low (146 °C) heat source temperatures. The optimization efforts are aimed at maximizing net power production for all concerning cycles, the results show that the proposed cycle can produce 9% and 8% more power than the reference Kalina cycles, while a better thermal performance is achieved for thermal efficiency and exergy efficiency. When the proposed cycle compares with ORC, the amount of net power can be produced is improved by 9% and 3%, respectively. On the other hand, the thermal performance of Kalina cycles and ORC are largely relied on the design of internal heat exchangers, requiring relatively larger size of internal heat exchangers. The proposed cycle, however, is much more compact because of less amount of internal heat transfer needed, leading to less irreversibilities. The proposed cycle can be further simplified by using a solution cooled absorber which eventually decreases the system complexity. A parametrical study shows that the proposed cycle has a better capability of adaptation to a wider temperature range of heat source conditions while maintaining a better performance.