Investigation on efficiency improvement of a Kalina cycle by sliding condensation pressure method

- The KSG-1 Kalina cycle using sliding condensation pressure is analyzed.
- Effect of ammonia mass fraction is discussed.
- Annual averaged efficiency can be enhanced significantly.
- Further composition tuning can only improve the performance slightly.
- Sliding condensation pressure is compared with composition tuning method.

Conventional Kalina cycle-based geothermal power plants are designed with a fixed working point determined by the local maximum ambient temperature during the year. A previous study indicated that the plant's annual average thermal efficiency would be improved if the ammonia mass fraction of the Kalina cycle could be tuned to adapt to the ambient conditions. In this paper, another sliding condensation pressure method is investigated. A theoretical model is set up and then a numerical program is developed to analyze the cycle performance. The condensation pressure adjustment in accordance to the changing ambient temperature has been numerically demonstrated under various ammonia-water mixture concentrations. The results indicate that the Kalina cycle using sliding condensation pressure method can achieve much better annual average thermal efficiency than a conventional Kalina cycle through matching the cycle with the changing ambient temperature via controlling condensation pressure. Furthermore, the sliding condensation pressure method is compared with the composition tuning method. The results show that the annual average efficiency improvement of the sliding condensation pressure method is higher than that of the composition tuning method.