Exploring a potential application of hydrate separation for composition adjustable combined cooling and power system

•A novel hydrate based composition adjustable cooling and power system is proposed.•Zeotropic mixture hydrate is firstly applied in thermodynamic system as separator.•The optimization selection criteria based on 3D T-s-θ diagram are established.•Second law efficiency ηII of novel system is 0.57 with R22/R32.•The ηII of novel system is increased by 21.26% contrasting to traditional system. At present stage, the thermodynamic perfection of cycles in the field of medium and low temperature heat is generally below 40%, and this poses a challenge in improving the efficiency of thermodynamic cycles. Therefore, exploring the energy-conversion potential of thermodynamic cycles becomes an urgent question to be addressed. In this study, the concept of hydrate regulating working fluid composition is first proposed, and a novel composition adjustable combined cooling and power system based on hydrate is studied. The separation work of regulating working fluid composition could be utilized in the form of hydrate formation/dissociation enthalpy. This system could realize the optimal match between the working fluids and the thermodynamic processes. Besides, the novel system could meet the demand of cooling and electricity demands. When R22/R32 mixture is employed as working fluid, the second law efficiency of the composition adjustable combined cooling and power system based on hydrate is 0.57, while the second law efficiency of pure working fluids (R22 or R32) systems is 0.48. Compared to the traditional pure working fluid systems, the second law efficiency could be increased up to 21.26% in the novel system. The performance of the novel system and traditional pure working fluid systems under different heat sources are also compared, the results show that performance of the novel system is still better than that of traditional pure working fluid systems. This study could provide a new solution for offshore energy demand.