Maria E. Mondejar

A new IPSEpro library for the simulation of binary mixtures of real fluids in power cycle analysis

Increasing efforts to produce power from renewable resources and improve the efficiency of current industrial processes have turned the spotlight on organic Rankine cycles (ORC). The use of refrigerant mixtures in these cycles offers a wide range of possibilities for fluid selection and optimization. Moreover, zeotropic mixtures are reported to yield better cycle performances due to their better thermal match with the source and sink streams. In this work a new IPSEpro® library for the simulation of power cycles using binary mixtures was developed. With this library the working fluid can be defined as the mixture of any pair of suitable fluids contained in the Refprop database.

Aerodynamic Considerations in the Thermodynamic Analysis of Organic Rankine Cycles

Due to the increasing interest of producing power from renewable and non-conventional resources, organic Rankine cycles are finding their place in today’s thermal energy mix. The main influencers on the efficiency of an organic Rankine cycle are the working fluid and the expander. Therefore most of the research done up to date turns around the selection of the best performance working media and the optimization of the expansion unit design. However, few studies consider the interaction of the working fluids in the turbine design, and how this fact can affect the overall thermodynamic cycle analysis. In this work we aim at including the aerodynamic behavior of the working fluids and their effect on the turbine efficiency in the thermodynamic analysis of an organic Rankine cycle. To that end, we proposed a method for the estimation of the characteristics of an axial in-flow turbine in an organic Rankine cycle simulation model. The code developed for the characterization of the turbine behavior under the working fluid properties evaluated the irreversibilities associated to the aerodynamic losses in the turbine. The organic Rankine cycle was analyzed by using IPSEpro process simulator. A set of candidate working fluids composed of selected organofluorines and organochlorines was chosen for the analysis. The thermophysical properties of the fluids were estimated with the equations of state implemented in Refprop. Results on the energy and exergy overall performances of the cycle were analyzed for a case study with standard source and sink temperatures. For each fluid the number of stages and geometry of the turbine were optimized. It was observed that some working fluids that could initially be considered as advantageous from a thermodynamic point of view, had an unfavorable impact on the turbine efficiency, thus increasing the irreversibilities of the cycle. We concluded that if the influence of the working fluid on the turbine performance is underestimated, the real performance of the organic Rankine cycle could show unexpected deviations from the theoretical results. (Less)

Non-conventional working fluids for thermal power generation: A review

New technology requirements derived from the exploitation of novel energy resources, and the needs for improvement of the energy efficiency of current power generation systems are pushing the industry towards the search of alternative working fluids. The great challenge for these non-conventional fluids is to provide satisfactory performances and fill the existing lack of media for some innovative energy applications. In this review a number of emerging working fluids for thermal power generation are presented. Also, a special emphasis is devoted to the discussion about new promising fluids, such as nanofluids or ionic liquids, that could be an important breakdown for power generation in the near future.

Energy Integration of Organic Rankine Cycle, Exhaust Gas Recirculation and Scrubber

The vast majority of ships trafficking the oceans are fuelled by residual oil with sulphur high content, which produces sulphur oxides (SOx) when combusted. Additionally, the high pressures and temperatures in modern diesel engines also produce nitrogen oxides (NOx). These emissions are both a hazard to health and the local environment, and regulations enforced by the International Maritime Organization (IMO) are driving the maritime sector towards the use of either distillate fuels containing less sulphur, or the use of exhaust gas cleaning devices. Two common techniques for removing SOx and limiting NOx are the open loop wet scrubber and exhaust gas recirculation (EGR). A scrubber and EGR installation reduces the overall efficiency of the system as it needs significant pumping power, which means that the exhaust gases are cleaner but at the expense of higher CO2 emissions. In this paper we propose a method to integrate an exhaust gas cleaning device for both NOx and SOx with an organic Rankine cycle for Waste Heat Recovery (WHR), thereby enhancing the system efficiency. We investigate three ORC configurations, integrated with the energy flows from both an existing state-of-the-art EGR system and an additional open loop wet scrubber.

Geothermal Power Technologies

Although geothermal energy has been widely deployed for direct use in locations with especial geologic manifestations, its potential for power generation has been traditionally underestimated. Recent technology developments in drilling techniques and power conversion technologies from low-temperature heat resources are bringing geothermal energy to the spotlight as a renewable baseload energy option for a sustainable energy mix. Although the environmental impact and economic viability of geothermal exploitation must be carefully evaluated for each case, the use of deep low-temperature geothermal reservoirs could soon become an important contributor to the energy generation around the world.