Evaluation of mixtures performances in Organic Rankine Cycle when utilizing the geothermal water with and without cogeneration

In this paper, performances of some zeotropic mixtures in Organic Rankine Cycle (ORC) have been assessed and evaluated for potential of utilizing the low-temperature and -caloric geothermal water. The options of single power generation and Combined Heat and Power (CHP) production through the common series and parallel configurations have been considered. The possible optimization of these applications when using the mixtures opposite pure fluids is the main objective and has been largely discussed. To reach this, the maximal power output level has been mainly focused as evaluation factor for variety of the heat source temperatures (up to 120°) and heat consumer parameters. The results showed that in case of stand-alone ORC the mixtures: R438A, R422A and R22M are more efficient than the pure fluids advised and can enhance the power productivity and geothermal water utilization at the sources' temperatures 80, 100 and 120 °C, respectively. R407A and R22D also offer attractive outputs at source temperatures of 80 °C and 100 °C, respectively. Furthermore, compared to R601a in the series CHP option using R22M in the parallel CHP circuit at heat source temperature 120 °C is more feasible and enables considerable promotions for a wide field of conditions. Similarly, R422A at source temperature 100 °C is also energetically favorable, but only at conditions matching the low till moderate heat loads or high supply temperatures. Finally, R22M and R422A are always much better than the pure R227ea in the parallel ORC-CHP system within this study.