The global growth in electricity consumption and the shortcomings of renewable electricity generation technologies are some of the reasons why it is still relevant to evaluate the performance of power conversion technologies that are used in fossil fuel power stations. The power conversion technology that is widely used in fossil fuel power stations is the Rankine cycle. The goal of this study was to determine if the efficiency of a typical Rankine cycle can be improved by adding a heat pump as a bottoming cycle. Three simulation models were developed to perform this evaluation. The first is a simulation model of a Rankine cycle. A quite detailed Rankine cycle configuration was evaluated. The simulation model was used to determine the heating requirements of the heat pump cycle as well as its operating temperature ranges. The efficiency of this Rankine cycle was calculated as 43.05 %. A basic vapour compression cycle configuration was selected as the heat pump of the combined cycle. A simulation model of the vapour compression cycle and the interfaces with the Rankine cycle was developed as the second simulation model. Working fluids that are typically used in vapour compression cycles cannot be used for this application, due to temperature limitations. The vapour compression cycle’s simulation model was therefore also used to calculate the coefficient of performance (COP) for various working fluids in order to select a suitable working fluid. The best cycle COP (3.015 heating) was obtained with ethanol as working fluid. These simulation models were combined to form the simulation model of the Rankine-heat pump combined cycle. This model was used to evaluate the performance of the combined cycle for two different compressor power sources. This study showed that the concept of using steam turbine or electrical power to drive a compressor driven vapour compression cycle in the configuration proposed here does not improve the overall efficiency of the cycle. The reasons for this were discovered and warrant future investigation. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013.

Thesis (M.S.)--Mississippi State University. Department of Mechanical Engineering. / Title from title screen. Includes bibliographical references.

The Organic Rankine Cycle (ORC) may be the superior cycle for power generation using low temperature and low power heat sources due to the utilization of high molecular mass fluids with low boiling points. They are flexible, simple, easy to operate and maintain, and offer many possible areas of applications including waste heat recovery and power generation from biomass, geothermal and even solar energy. Therefore, they may prove to be of significant importance in reducing global greenhouse gas emission and in the mitigation of climate change. In this thesis the technical feasibility and economic profitability of implementing an ORC in a district heating boiler station is investigated. A model of ORC connected to the hot water circuit of one of the biomass boilers of the boiler station is simulated. The achieved evaporation temperature is estimated to 135 degrees C and the condensation temperature is found to vary in the range of about 70-100 degrees C. The results show that it is both possible and profitable to implement an ORC in the studied boiler station. A maximum net present value of 2.3 MSEK is achieved for a 400 kW system and a maximum internal rate of return of 8.5%, equivalent to a payback period of 9.5 years, is achieved for a 300 kW system. Furthermore, the investment is found to be most sensitive to changes in the electricity price, net electric efficiency and capital expenditure cost.

Sub-Saharan Africa has an underutilised solar resource that is available to provide distributed-scale power to rural communities that are not reached by the current grid systems that are in place. Renewable power generation systems are typically infeasible for this purpose due to their high manufacturing and maintenance costs. This research proposes to address this by experimentally investigating the performance of a micro-scale, solar thermal Rankine cycle with direct steam generation using an affordable solar collector design. The intended power generation range is between 0.1 and 1 kW, which can be used for the direct mechanical pumping of rural irrigation systems or municipal water supplies. The study focuses on the performance of the solar collector (the solar reflector and the solar receiver) under realistic solar thermal conditions in sub-Saharan Africa, as it is considered to be one of the most important components in the solar thermal Rankine cycle. The performance of the solar collector was first characterised in an optical analysis of the new faceted dish reflector design, which comprised six Mylar membranes stretched over the elliptical rims of television satellite dishes. The optical analysis was conducted with the main goal of determining how much concentrated solar radiation would intercept the experimental receiver aperture during solar testing. This was determined by measuring the reflectivity of the reflector facets through ultraviolet and visible light (UV-VIS) spectroscopy and producing an intercept factor trend as a function of receiver aperture size through photographic lunar flux mapping. Based on the spectroscopy analysis, the spectral reflectivity of the clean Mylar facets was determined to be 97% for the visible light spectrum. The intercept factor was determined to be 87% for the designed receiver aperture diameter of 135 mm. The thermal testing took place on a clear, sunny day with low wind velocities. The solar collector followed the arc of the sun throughout the day with a 1° tracking error. During the testing, municipal water was passed through the receiver at 0.284 g/s and the temperature and pressure within the receiver were recorded. A 91-minute testing period occurred, where the inlet and outlet process flows obtained relatively constant operating temperatures with the inlet temperature at 54 °C and the outlet temperature at 343 °C. The total solar irradiance dropped from 801 to 705 W/m2 during this testing period. Using a reflector with a total incident area of 2.73 m2, the total radiation intercepted at the aperture dropped from 1 845 to 1 625 W during this period. The total power capture by the working fluid averaged at approximately 861 W and the total rate of heat loss was determined to be between 1 000 and 750 W. An average collector efficiency of 42% and an average receiver efficiency of 49% were determined for the testing period. An analysis of the heat loss showed that approximately 84% of the heat was lost through the aperture, of which, 31% was from reflected radiation. The second-law analysis showed that most of the irreversibility in the solar collector was caused by absorption of the concentrated radiation at the coil surface. This was because of the large temperature difference between the sun and the receiver coils. The experimental thermal analysis highlighted the design challenges of the micro-scale thermal Rankine cycle. However, the analysis showed that a solar collector can be constructed using locally sourced, affordable materials and can be used to produce power at a micro-scale. With appropriate attention given to optimising the collector design and determining the optimum operating conditions of the solar receiver, the power cycle would be able to compete with current technologies to provide decentralised power to communities in need. / Dissertation (MEng)--University of Pretoria, 2019. / Technology Innovation Agency (TIA); National Research Foundation (NRF); Department of Science and Innovation (DSI) / Mechanical and Aeronautical Engineering / MEng (Mechanical) / Unrestricted

No description available.

In this dissertation, different configurations of solar powered organic Rankine cycles (ORC) are investigated. The configurations include: a basic ORC, a regenerative ORC (R-ORC), and a basic ORC with electric energy storage (EES) (ORC-EES). The basic ORC and the R-ORC are evaluated using different dry organic fluids based on the first and second laws of thermodynamics and electricity production. The performance of both ORC systems is based on the potential for primary energy consumption (PEC) and carbon dioxide emission (CDE) savings, the electricity production, and the available capital cost (ACC) for the system. The R-ORC and basic ORC are both evaluated in Jackson, MS and Tucson, AZ to determine the effect of hourly solar irradiation and ambient temperature on both systems. For the basic ORC a parametric analysis is performed to determine the effects of cycle pressure, temperature, solar collector area, and turbine efficiency on the system performance. Similarly, for the R-ORC, a parametric analysis investigating the effect of open feed organic fluid heater intermediate pressure and turbine efficiency on the R-ORC is performed. Finally an ORC connected to an EES device located in Tucson, AZ is studied. The ORC-EES supplies electricity to three different commercial buildings. The ORC-EES is modeled to be charging when irradiation is available and discharging when there is not enough irradiation to generate electricity from the ORC. The performance of the system is based on the amount of electricity supplied, the potential for PEC, CDE, and cost savings, and the ACC. The effect of solar collector area on the percentage of supplied electricity, EES device size, and cost savings is also studied. It was determined that all the evaluated ORC configurations have the potential to produce PEC, CDE, and cost savings, but their performance is affected by the organic working fluid, solar collector area, and the location where the system is installed.

No description available.

This study investigates the potential of installing an integrated solar powered Organic Rankine Cycle (ORC) with electric energy storage (EES) to provide clean energy to commercial buildings in different climate zones in the US. Reducing the primary energy consumption (PEC), lowering the carbon dioxide emissions (CDE) and increasing the operational cost savings are primary objectives. Firstly, a large office building for eight US climates is studied. The EES is sized to store all the electricity generated by the system. Secondly, the system is studied for sixteen different commercial buildings, in the best climate zone, by considering two operational strategies. Finally, the influence of variable expander efficiency on the system performance is investigated. Results indicate that Phoenix is the best location in the US, among the evaluated locations, to install the ORC-EES. The model for the full-service restaurant shows higher savings and more electricity supply percentage than the other buildings. The model under the variable expander efficiency lowers the yearly PEC by 1.6% and CDE and operational cost savings both by 11%.

No description available.

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]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/84013