Low-Concentration Solar-Power Systems Based on Organic Rankine Cycles for Distributed-Scale Applications: Overview and Further Developments

This paper is concerned with the emergence and development of low-to-medium-grade thermal-energy-conversion systems for distributed power generation based on thermo- dynamic vapor-phase heat-engine cycles undergone by organic working uids, namely organic Rankine cycles (ORCs). ORC power systems are, to some extent, a relatively established and mature technology that is well-suited to converting low/medium-grade heat (at temperatures up to ~300–400°C) to useful work, at an output power scale from a few kilowatts to 10s of megawatts. Thermal ef ciencies in excess of 25% are achievable at higher temperatures and larger scales, and efforts are currently in progress to improve the overall economic viability and thus uptake of ORC power systems, by focusing on advanced architectures, working- uid selection, heat exchangers and expansion machines. Solar-power systems based on ORC technology have a signi cant potential to be used for distributed power generation, by converting thermal energy from simple and low-cost non-concentrated or low-concentration collectors to mechanical, hydrau- lic, or electrical energy. Current elds of use include mainly geothermal and biomass/ biogas, as well as the recovery and conversion of waste heat, leading to improved energy ef ciency, primary energy (i.e., fuel) use and emission minimization, yet the technology is highly transferable to solar-power generation as an affordable alternative to small-to- medium-scale photovoltaic systems. Solar-ORC systems offer naturally the advantages of providing a simultaneous thermal-energy output for hot water provision and/or space heating, and the particularly interesting possibility of relatively straightforward onsite (thermal) energy storage. Key performance characteristics are presented, and important heat transfer effects that act to limit performance are identi ed as noteworthy directions of future research for the further development of this technology

Optimisation of a high-efficiency solar-driven organic rankine cycle for applications in the built environment

Energy security, pollution and sustainability are major challenges presently facing the international community, in response to which increasing quantities of renewable energy are to be generated in the urban environment. Consequently, recent years have seen a strong increase in the uptake of solar technologies in the building sector. In this work, the potential of a solar combined heat and power (CHP) system based on an organic Rankine cycle (ORC) engine is investigated in a domestic setting. Unlike previous studies that focus on the optimisation of the ORC subsystem, this study performs a complete system optimisation considering both the design parameters of the solar collector array and the ORC engine simultaneously. Firstly, we present thermodynamic models of different collectors, including flat-plate and evacuated-tube designs, coupled to a non-recuperative sub-critical ORC architecture that delivers power and hot water by using thermal energy rejected from the engine. Optimisation of the complete system is first conducted, aimed at identifying operating conditions for which the power output is maximised. Then, hourly dynamic simulations of the optimised system configurations are performed to complete the system sizing. Results are presented of: (i) dynamic 3-D simulations of the solar collectors together with a thermal energy storage tank, and (ii) of an optimisation analysis to identify the most suitable working fluids for the ORC engine, in which the configuration and operational constraints of the collector array are considered. The best performing working fluids (R245fa and R1233zd) are then chosen for a whole-system annual simulation in a southern European climate. The system configuration combining an evacuated-tube collector array and an ORC engine is found to be best-suited for electricity prioritisation, delivering an electrical output of 3,605¿kWh/year from a 60¿m2 collector array. In addition, the system supplies 13,175¿kWh/year in the form of domestic hot water, which is equivalent to more than 6 times the average annual household demand. A brief cost analysis and comparison with photovoltaic (PV) systems is also performed, where despite the lower PV investment cost per kWel, the levelised energy costs of the different systems are found to be similar if the economic value of the thermal output is taken into account. Finally, a discussion of the modelled solar-CHP systems results shows how these could be used for real applications and extended to other locationsPeer ReviewedPostprint (updated version

Performance and operation of micro-ORC energy system using geothermal heat source

Abstract In the electricity production sector, geothermal energy is considered a reliable energy source because of its independence of seasonal, climatic and geographical conditions. Low-temperature geothermal wells present a huge potential of exploitation, as the development of binary cycles and the technological improvement in drilling make this heat source a competitive solution for electricity generated distribution and self-consumption. The Organic Rankine Cycle (ORC) is currently the best solution to convert heat into electricity using low enthalpy heat sources. The ORC technology is already mature and widespread for medium and large-scale power plants, applying for geothermal, solar, biomass or waste heat recovery exploitation. Micro-scale ORC applications are still not diffused in the market: the system layout, the working fluid selection and the expander architecture can significantly vary depending on the specific realization requirements, thus a standard configuration has not established yet. In this paper, a particular case study of a micro-ORC power system using a geothermal well is presented. The application in analysis is a plug-and-play ORC facility, currently installed and operating in a pool centre. The system layout and the main components are described. The heat source is a geothermal well, which continuously supplies (by pressure difference) liquid water at a temperature lower than 60 °C to a binary Rankine cycle working with R134a. The ORC system is driven by a prototypal radial-piston expander and adopts an external-gear feed pump and a recuperative cycle. It is developed for working continuously, delivering the generated electricity directly into the grid. The facility is provided with temperature, pressure and electric power sensors for monitoring the operation and for a preliminary evaluation of the performance. The global efficiency of expander and feed pump and the ORC net efficiency have been evaluated at the regular working conditions of the geothermal well, showing values equal to, respectively, 53 %, 41 % and 4.4 %

Experimental investigation of a cascaded organic Rankine cycle plant for the utilization of waste heat at high and low temperature levels

A power plant with two cascaded organic Rankine cycles (CORC) to exploit waste heat from a 800 kWe combined heat and power plant, fueled by biogas, is designed and tested. Heat from the exhaust gas is utilized with a high temperature organic Rankine cycle (HT-ORC), where toluene is employed as a working fluid. The heat discharged from the HT-ORC as well as heat from the engine coolant and additional heat from the exhaust gas is supplied to a low temperature ORC (LT-ORC) with the working fluid Solkatherm SES36. The design of the CORC and the selection of working fluids is presented, aiming at a maximum plant efficiency, but also complying with environmental, safety and practical issues. Furthermore, plant components and construction details are described. After manufacturing, initial tests are carried out, obtaining thermodynamic conditions that are close to the design of the HT-ORC, where a maximum electrical turbo-generator output of 17.5 kW is measured. The cascading of the low temperature heat sources and the transfer to the LT-ORC is shown as well as the basic operation of the LT-ORC. However, several problems occurred, such as a turbo-generator damage in the HT-ORC, a too high condensation pressure and a low working fluid mass flow rate in the LT-ORC, which are discussed together with proposed optimization measures

Equivalent temperature-based approach for thermal design and the selection of optimal working fluids for refrigeration and organic Rankine cycles

Les systèmes de réfrigération et de puissance représentent la plus grande part de la consommation d'énergie dans les secteurs résidentiel et commercial à travers le monde. Les projections de la demande mondiale d'énergie montrent même une tendance vers une hausse significative au cours des prochaines années. Par conséquent et en raison des sources d'énergie fossiles limitées et de l'impact environnemental, l'optimisation de ces cycles thermodynamiques a attiré beaucoup l'attention des chercheurs. Les performances économiques, environnementales et de fonctionnement des cycles dépendent fortement de la sélection du fluide de travail, ainsi que des caractéristiques de conception et de fonctionnement du cycle. Le choix du fluide de travail est un problème complexe car il implique la sélection du fluide de travail approprié parmi un grand nombre de candidats ainsi que l’ensemble des conditions de fonctionnement possibles pour chaque candidat. Pour résoudre ce problème, une approche systématique doit être définie pour filtrer les alternatives. L'objectif principal de ce projet de recherche est d'introduire une approche systématique pour la conception thermique et la sélection des fluides de travail optimaux pour les cycles de Rankine organique et de réfrigération basés sur le concept de température équivalente. L'approche systématique introduite se compose de deux étapes, à savoir: l'optimisation des performances à l'échelle du système; et la conception à l'échelle des composants. Dans la première étape, l'efficacité maximale possible du système dans des circonstances idéales est déterminée, indépendamment du fluide de travail, basée sur les conditions existantes de la source externe. Étant donné que la température équivalente exprime implicitement la température de saturation, le sous-refroidissement et les degrés de surchauffe, l'utilisation d'une température équivalente au lieu de la température réelle nous fournit un nombre réduit de paramètres pour le problème d'optimisation. De plus, l'interprétation géométrique de la température équivalente sur le diagramme h-s ouvre la voie au calcul de la génération d'entropie à travers les composants du système qui reste un problème non résolu dans la littérature. Les résultats de l'optimisation des performances à l'échelle du système, ensuite, établissent des critères thermodynamiques pour présélectionner les fluides de travail potentiels. Dans la deuxième étape, une procédure de reconstruction est définie pour corréler les résultats d'optimisation, qui sont en termes de température équivalente, avec les paramètres de fonctionnement réels pour chaque fluide de travail présélectionné. Étant donné que les propriétés individuelles des fluides de travail présélectionnés sont disponibles, l'efficacité de la première loi et la conductance thermique totale sont considérées comme deux indicateurs économiques pour évaluer les performances de chaque fluide de travail. Par conséquent, le fluide de travail le plus approprié pourrait être sélectionné. L'approche a d'abord été appliquée à la réfrigération par compression de vapeur et au cycle organique de Rankine. Les résultats ont démontré la supériorité de cette approche par rapport aux approches existantes dans la littérature. Il a été démontré que l'utilisation d'une température équivalente entraînait un problème d'optimisation précis et, à son tour, une meilleure conception des systèmes. Par la suite, l'approche a été étendue au système de réfrigération à éjection où la complexité du flux de fluide à l'intérieur de l'éjecteur crée un obstacle d'optimisation à l'échelle du système. De plus, certaines hypothèses préliminaires, concernant les différences de température dans les échangeurs de chaleur, empêchent les chercheurs d'atteindre une approche de conception systématique efficace. Pour simplifier la complexité des phénomènes à l'intérieur de l'éjecteur, il a été remplacé par un compresseur-expanseur hypothétique, puis le taux de génération d'entropie résultant a été caractérisé en utilisant l'efficacité de l'éjecteur. Nous avons ensuite déterminé les variables d'optimisation et jeté les bases d'une détermination systématique des états de fonctionnement des fluides de travail potentiels, sans aucune hypothèse préliminaire. Pour valider notre conception thermodynamique, une technique CFD a été utilisée pour déterminer les paramètres géométriques de l'éjecteur qui fournissent les conditions d’opération désirées.Abstract: Refrigeration and power systems account for the largest portion of energy use by residential and commercial sectors around the world. Global energy demand projections show even a significant increasing trend by upcoming years. As a result and due to limited fossil fuel energy sources and the environmental impact of rising energy consumption, the optimization of such thermodynamic cycles has drawn much attention from researchers. The economic, environmental and operating performance of the cycles depends heavily on the selection of the working fluid, as well as the design and operating characteristics of the cycle. The choice of the working fluid is a complex problem because it implies the selection of the appropriate working fluid among a huge number of candidates as well as the sets of possible operating conditions for each candidate. To address this issue, a systematic approach needs to be defined to screen the alternatives. The main objective of this research project is to introduce a systematic approach for the thermal design and selection of the optimal working fluids for organic Rankine and refrigeration cycles based on the equivalent temperature concept. The introduced systematic approach is composed of two steps, namely: system-scale performance optimization; and component-scale design. In the first step, the maximum possible efficiency of the system under ideal circumstances is determined, independently of the working fluid, based on the existing external source conditions. Since equivalent temperature implicitly expresses the saturation temperature, subcooling, and superheating degrees, using equivalent temperature instead of actual temperature provides us with a reduced number of parameters for the optimization problem. Furthermore, the geometrical interpretation of equivalent temperature on the h-s diagram paves the way for the calculation of entropy generation through the system components which remained an unsolved issue in the literature. The results of system-scale performance optimization, then, establish thermodynamic criteria to pre-select the potential working fluids. In the second step, a reconstruction procedure is defined to correlate the optimization results, which are in terms of equivalent temperature, with the actual operating parameters for each pre-selected working fluid. Since the individual properties of the pre-selected working fluids are available, first-law efficiency and total thermal conductance are considered as two economic indicators to evaluate the performance of each working fluid. As a result, the most appropriate working fluid could be selected. The approach was, first, applied to the vapor-compression refrigeration and organic Rankine cycle (ORC). The results demonstrated the superiority of this approach compared to the existing approaches in the literature. It was shown that using equivalent temperature resulted in a precise optimization problem and, in turn, a better design of the systems. Afterward, the approach was extended to the ejector refrigeration system where the complexity of fluid flow inside the ejector creates an obstacle for system-scale optimization. Moreover, some preliminary assumptions, regarding temperature differences in heat exchangers, prevent researchers from reaching an efficient systematic design approach. To simplify the complexity of phenomena inside the ejector, it was replaced by a hypothetical expander-compressor, and then the resultant entropy generation rate was characterized by using the efficiency of the ejector. We subsequently determined the optimization variables and laid the foundation for a systematic determination of operating states for potential working fluids, without any preliminary assumptions. To validate our thermodynamic design, a CFD technique was employed to determine the ejector geometry parameters that deliver the desired operating conditions

Small-Scale CCHP Systems for Waste Heat Recovery from Cement Plants: Thermodynamic, Sustainability and Economic Implications

In this paper, different combined cooling, heating and power (CCHP) systems are introduced and studied for waste heat recovery from a cement plant located in Şanliurfa, Turkey considering domestic applications. One of the systems is based on the steam Rankine cycle and the next is based on recuperative organic Rankine cycle (ORC), while both of them are equipped with a LiBr–H2O absorption chiller to produce cooling. Different working fluids are considered in the ORC simulation. Energy, exergy and exergoeconomic principles are applied to compare the examined systems from thermodynamic, sustainability and economic aspects. It is observed that utilizing siloxanes as the working fluid leads to efficient performance of the ORC. Besides, employed heat recovery steam generator in the Rankine cycle and evaporator in the ORC found to be the most exergy destructive components. Results revealed that the CCHP system operating with ORC (MM as working fluid) has a better performance thermodynamically with energy utilization factor, exergy efficiency and sustainability index of 98.07, 63.6% and 2.747, respectively. This is while, Rankine-based CCHP is economically preferable with a payback period of 4.738 year compared to the system operating with ORC and a payback period of 5.074 year

Study of Organic Rankine Cycles for Waste Heat Recovery in Transportation Vehicles

Regulations for ICE-based transportation in the EU seek carbon dioxide emissions lower than 95 g CO2/km by 2020. In order to fulfill these limits, improvements in vehicle fuel consumption have to be achieved. One of the main losses of ICEs happens in the exhaust line. Internal combustion engines transform chemical energy into mechanical energy through combustion; however, only about 15-32% of this energy is effectively used to produce work, while most of the fuel energy is wasted through exhaust gases and coolant. Therefore, these sources can be exploited to improve the overall efficiency of the engine. Between these sources, exhaust gases show the largest potential of Waste Heat Recovery (WHR) due to its high level of exergy. Regarding WHR technologies, Rankine cycles are considered as the most promising candidates for improving Internal Combustion Engines. However, the implementation of this technology in modern passenger cars requires additional features to achieve a compact integration and controllability in the engine. While industrial applications typically operates in steady state operating points, there is a huge challenge taking into account its impact in the engine during typical daily driving profiles. This thesis contributes to the knowledge and characterization of an Organic Rankine Cycle coupled with an Internal Combustion Engine using ethanol as working fluid and a swash-plate expander as expansion machine. The main objective of this research work is to obtain and quantify the potential of Organic Rankine Cycles for the use of residual energy in automotive engines. To do this, an experimental ORC test bench was designed and built at CMT (Polytechnic University of Valencia), which can be coupled to different types of automotive combustion engines. Using these results, an estimation of the main variables of the cycle was obtained both in stationary and transient operating points. A potential of increasing ICE mechanical efficiency up to 3.7% could be reached at points of high load installing an ORC in a conventional turbocharged gasoline engine. Regarding transient conditions, a slightly simple and robust control based on adaptive PIDs, allows the control of the ORC in realistic driving profiles. High loads and hot conditions should be the starting ideal conditions to test and validate the control of the ORC in order to achieve high exhaust temperatures that justify the feasibility of the system. In order to deepen in the viability and characteristics of this particular application, some theoretical studies were done. A 1D model was developed using LMS Imagine.Lab Amesim platform. A potential improvement of 2.5% in fuel conversion efficiency was obtained at the high operating points as a direct consequence of the 23.5 g/kWh reduction in bsfc. To conclude, a thermo-economic study was developed taking into account the main elements of the installation costs and a minimum Specific Investment Cost value of 2030 €/kW was obtained. Moreover, an exergetic study showed that a total amount of 3.75 kW, 36.5% of exergy destruction rate, could be lowered in the forthcoming years, taking account the maximum efficiencies considering technical restrictions of the cycle components.Las normativas anticontaminantes para el transporte propulsado por motores de combustión interna alternativos en la Unión Europea muestran límites de emisión menores a 95 g CO2/km para el año 2020. Con el fin de cumplir estos límites, deberán ser realizadas mejoras en el consumo de combustible en los vehículos. Una de las principales pérdidas en los Motores de Combustión Interna Alternativos (MCIA) ocurre en la línea de escape. Los MCIA transforman la energía química en energía mecánica a través de la combustión; sin embargo, únicamente el 15-32% de esta energía es eficazmente usada para producir trabajo, mientras que la mayor parte es desperdiciada a través de los gases de escape y el agua de refrigeración del motor. Por ello, estas fuentes de energía pueden ser utilizadas para mejorar la eficiencia global del vehículo. De estas fuentes, los gases de escape muestran un potencial mayor de recuperación de energía residual debido a su mayor contenido exergético. De todos los tipos de Sistemas de Recuperación de Energía Residual, los Ciclos Rankine son considerados como los candidatos más prometedores para mejorar la eficiencia de los MCIA. Sin embargo, la implementación de esta tecnología en los vehículos de pasajeros modernos requiere nuevas características para conseguir una integración compacta y una buena controlabilidad del motor. Mientras que las aplicaciones industriales normalmente operan en puntos de operación estacionarios, en el caso de los vehículos con MCIA existen importantes retos teniendo en cuenta su impacto en el modo de conducción cotidianos. Esta Tesis contribuye al conocimiento y caracterización de un Ciclo Rankine Orgánico acoplado con un Motor de Combustión Interna Alternativo utilizando etanol como fluido de trabajo y un expansor tipo Swash-plate como máquina expansora. El principal objetivo de este trabajo de investigación es obtener y cuantificar el potencial de los Ciclos Rankine Orgánicos (ORC) para la recuperación de la energía residual en motores de automoción. Para ello, una instalación experimental con un Ciclo Rankine Orgánico fue diseñada y construida en el Instituto Universitario "CMT - Motores Térmicos" (Universidad Politécnica de Valencia), que puede ser acoplada a diferentes tipos de motores de combustión interna alternativos. Usando esta instalación, una estimación de las principales variables del ciclo fue obtenida tanto en puntos estacionarios como en transitorios. Un potencial de mejora en torno a un 3.7 % puede ser alcanzada en puntos de alta carga instalando un ORC en un motor gasolina turboalimentado. Respecto a las condiciones transitorias, un control sencillo y robusto basado en PIDs adaptativos permite el control del ORC en perfiles de conducción reales. Las condiciones ideales para testear y validar el control del ORC son alta carga en el motor comenzando con el motor en caliente para conseguir altas temperaturas en el escape que justifiquen la viabilidad de estos ciclos. Para tratar de profundizar en la viabilidad y características de esta aplicación particular, diversos estudios teóricos fueron realizados. Un modelo 1D fue desarrollado usando el software LMS Imagine.Lab Amesim. Un potencial de mejora en torno a un 2.5% en el rendimiento efectivo del motor fue obtenido en condiciones transitorias en los puntos de alta carga como una consecuencia directa de la reducción de 23.5 g/kWh del consumo específico. Para concluir, un estudio termo-económico fue desarrollado teniendo en cuenta los costes de los principales elementos de la instalación y un valor mínimo de 2030 €/kW fue obtenido en el parámetro de Coste Específico de inversión. Además, el estudio exergético muestra que un total de 3.75 kW, 36.5 % de la tasa de destrucción total de exergía, podría ser reducida en los años futuros, teniendo en cuenta las máximas eficiencias considerando restricciones técnicas en los componentes del ciclo.Les normatives anticontaminants per al transport propulsat per motors de combustió interna alternatius a la Unió Europea mostren límits d'emissió menors a 95 g·CO2/km per a l'any 2020. Per tal d'acomplir aquests límits, s'hauran de realitzar millores al consum de combustible dels vehicles. Una de les principals pèrdues als Motors de combustió interna alternatius (MCIA) ocorre a la línia d'escapament. Els MCIA transformen l'energia química en energia mecànica a través de la combustió; però, únicament el 15-32% d'aquesta energia és usada per produir treball, mentre que la major part és desaprofitada a través dels gasos d'escapament i l'aigua de refrigeració del motor. Per això, aquestes fonts d'energia poden ser utilitzades per millorar l'eficiència global del vehicle. Considerant aquestes dues fonts d'energia, els gasos d'escapament mostren un potencial major de recuperació d'energia residual debut al seu major contingut exergètic. De tots els tipus de Sistemes de Recuperació d'Energia Residual, els Cicles Rankine són considerats com els candidats més prometedors per millorar l'eficiència dels MCIA. No obstant, la implementació d'aquesta tecnologia en els vehicles de passatgers moderns requereix un desenvolupament addicional per aconseguir una integració compacta i una bona controlabilitat del motor. Mentre que les aplicacions industrials normalment operen en punts d'operació estacionaris, en el cas dels vehicles amb MCIA hi han importants reptes a solucionar tenint en compte el funcionament en condicions variables del motor i el seu impacte en la manera de conducció quotidiana del usuari. Aquesta Tesi contribueix al coneixement i caracterització d'un Cicle Rankine Orgànic (ORC) acoblat amb un motor de combustió interna alternatiu (MCIA) utilitzant etanol com a fluid de treball i un expansor tipus Swash-plate com a màquina expansora. El principal objectiu d'aquest treball de recerca és obtenir i quantificar el potencial dels ORCs per a la recuperació de l'energia residual en motors d'automoció. Per aconseguir-ho, una instal·lació experimental amb un ORC va ser dissenyada i construïda a l'Institut "CMT- Motores Térmicos" (Universitat Politècnica de València). Esta installació pot ser acoblada a diferents tipus de MCIAs. Mitjançant assajos experimentals en aquesta installació, una estimació de les principals variables del cicle va ser obtinguda tant en punts estacionaris com en punts transitoris. Un potencial de millora al voltant d'un 3.7% pot ser aconseguida en punts d'alta càrrega instal·lant un ORC acoblat a un motor gasolina turboalimentat. Pel que fa a les condicions transitòries, un control senzill i robust basat en PIDs adaptatius permet el control del ORC en perfils de conducció reals. Les condicions ideals per a testejar i validar el control de l'ORC són alta càrrega al motor començant amb el motor en calent per aconseguir altes temperatures d'escapament que justifiquen la viabilitat d'aquests cicles. Per tractar d'aprofundir en la viabilitat i característiques d'aquesta aplicació particular, diversos estudis teòrics van ser realitzats. Un model 1D va ser desenvolupat usant el programari LMS Imagine.Lab Amesim. Un potencial de millora al voltant d'un 2.5% en el rendiment efectiu del motor va ser obtingut en condicions transitòries en els punts d'alta càrrega com una conseqüència directa de la reducció de 23.5 g/kWh al consum específic. Per concloure, un estudi termo-econòmic va ser desenvolupat tenint en compte els costos dels principals elements de la installació i un valor mínim de 2030 €/kW va ser obtingut en el paràmetre del Cost Específic d'Inversió. A més, l'estudi exergètic mostra que un total de 3.75 kW, 36.5% de la taxa de destrucció total d'exergia, podria ser recuperat en un pròxim, considerant restriccions tècniques en els components del cicle i tenint en compte les màximes eficiències que es poden aconseguir.Royo Pascual, L. (2017). Study of Organic Rankine Cycles for Waste Heat Recovery in Transportation Vehicles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84013TESI

Assessment of the integration of an organic Rankine cycle for waste heat recovery from bleed air for implementation on board an aircraft

This project assesses the possibility of putting an organic Rankine cycle on board an aircraft for waste heat recovery using bleed air coming from the engine’s compressor as a heat source. Into this task the main subject taken into account was the weight of the system, since this will mean a trade-off between the power generated and the extra weight that is necessary to add. In recent years, little research on waste heat recovery on aircraft has been done. The main source of heat for these systems comes from the engine and not from the bleed air as in this project but in all cases penalties like changes in engine design, excessive weight from the heat exchangers and a loss in thrust were faced. On the other side, some of these penalties were surpassed by the amount of power that the organic Rankine cycles provided. To develop this project a model was designed on MATLAB varying the mass flow of the organic fluid to find out for the best arrangement that gives the most power output with the less weight. The model was performed under cruise conditions from an Airbus A320, a single aisle aircraft. The ORC was assessed in two locations; before the entrance of the precooler, a system that cools down the air before going into the pneumatic system, and before the air conditioning (AC) packs. The results show that heat recovery is possible only when the ORC is placed before the precooler but certain conditions need to be met so the energy balances result in positive outcomes. Current techniques were used to estimate the weight of the heat exchangers but improvements of these or availability of new materials in the future will increase the amount of energy that could be saved. The implementation of an ORC using the bleed system gives an option to recover wasted energy from aircraft since the conditions available are suitable for the system