Development of a code for the design and optimisation of Organic Rankine Cycles for power generation

Abstract

The aim of the present work is the parametric optimization of Organic Rankine Cycles (ORC) for its main application to medium-low temperature generic sources. For this purpose, a Matlab® [1] computational code has been developed, in which design parameters, mass flow ratios, cycle configuration and fluid selection (including mixtures) are simultaneously optimized to offer the best combination of variables for the maximization of the efficiency. Given its extraordinary reliability the reference thermodynamic database of the choice has been REFPROP® [2] v.9.1. The results accomplished por pure fluid configurations show great adaptability to previous validated optimization studies. Whereas, those for mixtures support the theoretical evidence that there is a significant efficiency growth to be accomplished when combining organic pure fluids into binary zeotropic mixtures. The main improvements of the present work with respect to previous ORC optimization studies are, in one hand the emphasis on looking for the most suitable mathematical method for optimization of variables, previous works lack more exhaustive considerations when choosing the theoretical nature of algorithm, for this purpose multiple algorithms had been put to test running the same model, concluding that heuristic and stochastic algorithms provide more accurate results in the job of converging to global optimal. In the other hand, regarding the specifics of ORC optimization, the goal of this work is to first develop a reliable computational tool for the analysis and optimization of ORC and then verificate it in orther to expand its performance to include the analysis of binary zeotropic mixtures, which is the ultimate objective of this study. It is a fact that the actual global situation calls for renewable and robust solutions for the energy production, these being one of the main reasons why there is a susbstantional increase of industries interest regarding the ORCtechnology. Aiming to represent a humble contribution to the promising future, this work pretendsto create an enlighting tool for the study of different ORC configurations and potential scenarios in the upcoming energy production world.