Comparative exergy analysis of direct alcohol fuel cells using fuel mixtures

Within the last years there has been increasing interest in direct liquid fuel cells as power sources for portable devices and, in the future, power plants for electric vehicles and other transport media as ships will join those applications. Methanol is considerably more convenient and easy to use than gaseous hydrogen and a considerable work is devoted to the development of direct methanol fuel cells. But ethanol has much lower toxicity and from an ecological viewpoint ethanol is exceptional among all other types of fuel as is the only chemical fuel in renewable supply. The aim of this study is to investigate the possibility of using direct alcohol fuel cells fed with alcohol mixtures. For this purpose, a comparative exergy analysis of a direct alcohol fuel cell fed with alcohol mixtures against the same fuel cell fed with single alcohols is performed. The exergetic ef���ciency and the exergy loss and destruction are calculated and compared in each case. When alcohol mixtures are fed to the fuel cell, the contribution of each fuel to the fuel cell performance is weighted attending to their relative proportion in the aqueous solution. The optimum alcohol composition for methanol/ethanol mixtures has been determined.

Perspectives on the design and use of direct alcohol fuel cells fed by alcohol blends

The fast-growing power demand by portable electronic devices has promoted the increase of global production of portable PEM fuel cell, a quarter of them consist of direct methanol fuel cell (DMFC) units. These present the advantage of being fuelled directly with a liquid fuel, as well as direct ethanol fuel cells (DEFC) do.

Fuel Cells: A Real Option for Unmanned Aerial Vehicles Propulsion

The possibility of implementing fuel cell technology in Unmanned Aerial Vehicle (UAV) propulsion systems is considered. Potential advantages of the Proton Exchange Membrane or Polymer Electrolyte Membrane (PEMFC) and Direct Methanol Fuel Cells (DMFC), their fuels (hydrogen and methanol), and their storage systems are revised from technical and environmental standpoints. Some operating commercial applications are described. Main constraints for these kinds of fuel cells are analyzed in order to elucidate the viability of future developments. Since the low power density is the main problem of fuel cells, hybridization with electric batteries, necessary in most cases, is also explored.

Electrochemical study of platinum deposited by electron beam evaporation for application as fuel cell electrodes

Platinum is the most used catalyst in electrodes for fuel cells due to its high catalytic activity. Polymer electrolyte and direct methanol fuel cells usually include Pt as catalyst in their electrodes. In order to diminish the cost of such electrodes, different Pt deposition methods that permit lowering the metal load whilst maintaining their electroactivity, are being investigated. In this work, the behaviour of electron beam Pt (e-beam Pt) deposited electrodes for fuel cells is studied. Three different Pt loadings have been investigated. The electrochemical behaviour by cyclic voltammetry in H2SO4, HClO4 and in HClO4+MeOH before and after the Pt deposition on carbon cloth has been analysed. The Pt improves the electrochemical properties of the carbon support used. The electrochemical performance of e-beam Pt deposited electrodes was finally studied in a single direct methanol fuel cell (DMFC) and the obtained results indicate that this is a promising and adequate method to prepare fuel cell electrodes.

Long Term Performance Study of a Direct Methanol Fuel Cell Fed with Alcohol Blends

The use of alcohol blends in direct alcohol fuel cells may be a more environmentally friendly and less toxic alternative to the use of methanol alone in direct methanol fuel cells. This paper assesses the behaviour of a direct methanol fuel cell fed with aqueous methanol, aqueous ethanol and aqueous methanol/ethanol blends in a long term experimental study followed by modelling of polarization curves. Fuel cell performance is seen to decrease as the ethanol content rises, and subsequent operation with aqueous methanol only partly reverts this loss of performance. It seems that the difference in the oxidation rate of these alcohols may not be the only factor affecting fuel cell performance.

Contribution sharing of a fuel mixture components to the fuel cell potencial of a direct alcohol fuel cell

The increasing worldwide demand for electricity impels to develop clean and renewable energy resources. In the field of portable power devices not only size and weight represent important aspects to take into account, but the fuel and its storage are also critical issues to consider. In this last sense, the direct methanol (MeOH) fuel cells (DMFC) play an important role as they can offer high power and energy density, low emissions, ambient operating conditions and fast and convenient refuelling.

Marine Practice Guidelines for Fuel Cell Applications

This paper focuses on the implementation of fuel cells in marine systems as a propulsion system and energy source. The objective is to provide an overview of the pertinent legislation for marine applications of fuel cells. This work includes a characterization of some guidelines for the safe application of fuel cell systems on ships. It also describes two ships that have implemented fuel cells to obtain energy, the Viking Lady, the first marine ship to include this technology, and Greentug, a reference for new tugs

Conceptual design of offshore platform supply vessel based on hybrid diesel generator-fuel cell power plant

Nowadays increasing fuel prices and upcoming pollutant emission regulations are becoming a growing concern for the shipping industry worldwide. While fuel prices will keep rising in future years, the new International Convention for the Prevention of Pollution from Ships (MARPOL) and Sulphur Emissions Control Areas (SECA) regulations will forbid ships to use heavy fuel oils at certain situations. To fulfil with these regulations, the next step in the marine shipping business will comprise the use of cleaner fuels on board as well as developing new propulsion concept. In this work a new conceptual marine propulsion system is developed, based on the integration of diesel generators with fuel cells in a 2850 metric tonne of deadweight platform supply vessel. The efficiency of the two 250 kW methanol-fed Solid Oxide Fuel Cell (SOFC) system installed on board combined with the hydro dynamically optimized design of the hull of the ship will allow the ship to successfully operate at certain modes of operation while notably reduce the pollutant emissions to the atmosphere. Besides the cogeneration heat obtained from the fuel cell system will be used to answer different heating needs on board the vessel

Polipirrol, un buen soporte para electrodos de pilas de combustible de metanol directo (DMFC)

(SPA) El polipirrol es uno de los pol��meros conductores m��s utilizados en la preparaci��n de electrodos debido a su alta actividad catal��tica para la oxidaci��n y reducci��n del metanol. En este trabajo se ha depositado electroqu��micamente polipirrol a diferentes potenciales de dep��sito, Ed, sobre tela de carb��n no tejida Freudenberg en medio ��cido. Se ha analizado la morfolog��a y la respuesta electroqu��mica en medio HClO4 y en presencia de HClO4+MeOH antes y despu��s de la s��ntesis del polipirrol sobre ella. Lastructura de las pel��culas obtenidas se ha estudiado por espectroscopia infrarroja de transformada de Fourier, FTIR. Se observa que el polipirrol mejora las propiedades electroqu��micas de la tela de carb��n, obteni��ndose el mejor resultado para su aplicaci��n como soporte del catalizador en pilas de combustible con la pel��cula sintetizada a 1,0V. (ENG) Polypyrrole is one of the most used conducting polymers in electrode building due to its high catalytic activity to the methanol oxidation and reduction. By this motive, polypyrrole has been electrochemically synthesized at constant potential, Ed, on Freudenberg carbon cloth in acid medium. Carbon cloth morphology and electrochemical behaviour in HClO4 and in HClO4+MeOH before and after the polypyrrole eposition have been analysed. The structure of the films was studied by Fourier transform infrared spectroscopy, FTIR. The polypyrrole improves the electrochemical properties of the studied carbon cloth. The biggest charge of the electroactive area is the one synthesized at 1.0V, being the best for its application as catalyst support in fuel cells.

Comportamiento electroqu��mico y en pila de combustible de c��todos fabricados mediante evaporacion electr��nica de Pt frente a electrodos comerciales

(SPA) Con el objetivo de disminuir el coste de los electrodos utilizados en las pilas de combustible de membrana polim��rica se ha llevado a cabo un estudio de la influencia sobre la respuesta electroqu��mica y en ensayos en monocelda de pila de combustible de alcohol directo, de la deposici��n por evaporaci��n electr��nica de platino sobre tela de carb��n. Se han estudiado en las mismas condiciones dos electrodos comerciales con distinta carga de catalizador y dos electrodos preparados por evaporaci��n electr��nica de platino. Se encuentra que la evaporaci��n electr��nica de platino sobre tela de carb��n ahorra carga de catalizador, aumenta la superficie electroactiva y permite alcanzar rendimientos comparables a los de los electrodos comerciales, mejorando mucho la potencia obtenida por unidad de masa de material catal��tico. (ENG) In order to diminish the cost of the electrodes used in polymer membrane fuel cells a study of the influence on the electrochemical response and essays in a single direct methanol fuel cell of the deposition by electronic evaporation of Platinum on carbon cloth has been carried out. Two commercial electrodes with different catalyst loading and two electrodes prepared by electronic evaporation of Platinum have been studied in the same conditions. It can be concluded that electronic evaporation of Platinum on carbon cloth saves catalyst load, increases the electroactive surface area and reaches fuel cell performances comparable with those obtained using commercial electrodes, improving clearly the power obtained per unit mass of catalytic material.

Assessment of Hydrogen as suistinable clean energy

The progressive depletion of fossil fuels and their high contribution to the energy supply in this modern society forces that will be soon replaced by renewable fuels. But the dispersion and alternation of renewable energy production also undertake to reduce their costs to use as energy storage and hydrogen carrier. It is necessary to develop technologies for hydrogen production from all renewable energy storage technologies and the development of energy production from hydrogen fuel cells and cogeneration and tri generation systems. In order to propel this technological development discussed where the hydrogen plays a key role as energy storage and renewable energy, the National Centre of Hydrogen and Fuel Cell Technology Experimentation in Spain equipped with installations that enable scientific and technological design, develop, verify, certify, approve, test, measure and, more importantly, the facility ensures continuous operation for 24 hours a day, 365 days year. At the same time, the system is scalable so as to allow continuous adaptation of new technologies are developed and incorporated into the assembly to verify integration at the same time it checks the validity of their development. The transformation sector can be said to be the heart of the system, because without neglecting the other sectors, this should prove the validity of hydrogen as a carrier - energy storage are important efforts that have to do to demonstrate the suitability of fuel cells or internal combustion systems to realize the energy stored in hydrogen at prices competitive with conventional systems. The multiple roles to meet the fuel cells under different conditions of operation require to cover their operating conditions, many different sizes and applications. The fourth area focuses on integration is an essential complement within the installation. We must integrate not only the electricity produced, but also hydrogen is used and the heat generated in the process of using hydrogen energy. The energy management in its three forms: hydrogen chemical, electrical and thermal integration requires complicated and require a logic and artificial intelligence extremes to ensure maximum energy efficiency at the same time optimum utilization is achieved. Verification of the development and approval in the entire production system and, ultimately, as a demonstrator set to facilitate the simultaneous evolution of production technology, storage and distribution of hydrogen fuel cells has been assessed.

Sistema de instrumenta����o e controle para c��lulas a combust��vel

Este trabajo presenta un estudio sobre el funcionamiento y aplicaciones de las c��lulas de combustible de membrana tipo PEM, o de intercambio de protones, alimentadas con hidr��geno puro y oxigeno obtenido de aire comprimido. Una vez evaluado el proceso de dichas c��lulas y las variables que intervienen en el mismo, como presi��n, humedad y temperatura, se presenta una variedad de m��todos para la instrumentaci��n de tales variables as�� como m��todos y sistemas para la estabilidad y control de las mismas, en torno a los valores ��ptimos para una mayor eficacia en el proceso. Tomando como variable principal a controlar la temperatura del proceso, y exponiendo los valores concretos en torno a 80 grados cent��grados entre los que debe situarse, es realizado un modelo del proceso de calentamiento y evoluci��n de la temperatura en funci��n de la potencia del calentador resistivo en el dominio de la frecuencia compleja, y a su vez implementado un sistema de medici��n mediante sensores termopar de tipo K de respuesta casi lineal. La se��al medida por los sensores es amplificada de manera diferencial mediante amplificadores de instrumentaci��n INA2126, y es desarrollado un algoritmo de correcci��n de error de uni��n fr��a (error producido por la inclusi��n de nuevos metales del conector en el efecto termopar). Son incluidos los datos de test referentes al sistema de medici��n de temperatura , incluyendo las desviaciones o error respecto a los valores ideales de medida. Para la adquisici��n de datos y implementaci��n de algoritmos de control, es utilizado un PC con el software Labview de National Instruments, que permite una programaci��n intuitiva, vers��til y visual, y poder realizar interfaces de usuario gr��ficas simples. La conexi��n entre el hardware de instrumentaci��n y control de la c��lula y el PC se realiza mediante un interface de adquisici��n de datos USB NI 6800 que cuenta con un amplio n��mero de salidas y entradas anal��gicas. Una vez digitalizadas las muestras de la se��al medida, y corregido el error de uni��n fr��a anteriormente apuntado, es implementado en dicho software un controlador de tipo PID ( proporcional-integral-derivativo) , que se presenta como uno de los m��todos m��s adecuados por su simplicidad de programaci��n y su eficacia para el control de este tipo de variables. Para la evaluaci��n del comportamiento del sistema son expuestas simulaciones mediante el software Matlab y Simulink determinando por tanto las mejores estrategias para desarrollar el control PID, as�� como los posibles resultados del proceso. En cuanto al sistema de calentamiento de los fluidos, es empleado un elemento resistor calentador, cuya potencia es controlada mediante un circuito electr��nico compuesto por un detector de cruce por cero de la onda AC de alimentaci��n y un sistema formado por un elemento TRIAC y su circuito de accionamiento. De manera an��loga se expone el sistema de instrumentaci��n para la presi��n de los gases en el circuito, variable que oscila en valores pr��ximos a 3 atmosferas, para ello es empleado un sensor de presi��n con salida en corriente mediante bucle 4-20 mA, y un convertidor simple corriente a tensi��n para la entrada al sistema de adquisici��n de datos. Consecuentemente se presenta el esquema y componentes necesarios para la canalizaci��n, calentamiento y humidificaci��n de los gases empleados en el proceso as�� como la situaci��n de los sensores y actuadores. Por ��ltimo el trabajo expone la relaci��n de algoritmos desarrollados y un ap��ndice con informaci��n relativa al software Labview. ABTRACT This document presents a study about the operation and applications of PEM fuel cells (Proton exchange membrane fuel cells), fed with pure hydrogen and oxygen obtained from compressed air. Having evaluated the process of these cells and the variables involved on it, such as pressure, humidity and temperature, there is a variety of methods for implementing their control and to set up them around optimal values for greater efficiency in the process. Taking as primary process variable the temperature, and exposing its correct values around 80 degrees centigrade, between which must be placed, is carried out a model of the heating process and the temperature evolution related with the resistive heater power on the complex frequency domain, and is implemented a measuring system with thermocouple sensor type K performing a almost linear response. The differential signal measured by the sensor is amplified through INA2126 instrumentation amplifiers, and is developed a cold junction error correction algorithm (error produced by the inclusion of additional metals of connectors on the thermocouple effect). Data from the test concerning the temperature measurement system are included , including deviations or error regarding the ideal values of measurement. For data acquisition and implementation of control algorithms, is used a PC with LabVIEW software from National Instruments, which makes programming intuitive, versatile, visual, and useful to perform simple user interfaces. The connection between the instrumentation and control hardware of the cell and the PC interface is via a USB data acquisition NI 6800 that has a large number of analog inputs and outputs. Once stored the samples of the measured signal, and correct the error noted above junction, is implemented a software controller PID (proportional-integral-derivative), which is presented as one of the best methods for their programming simplicity and effectiveness for the control of such variables. To evaluate the performance of the system are presented simulations using Matlab and Simulink software thereby determining the best strategies to develop PID control, and possible outcomes of the process. As fluid heating system, is employed a heater resistor element whose power is controlled by an electronic circuit comprising a zero crossing detector of the AC power wave and a system consisting of a Triac and its drive circuit. As made with temperature variable it is developed an instrumentation system for gas pressure in the circuit, variable ranging in values around 3 atmospheres, it is employed a pressure sensor with a current output via 4-20 mA loop, and a single current to voltage converter to adequate the input to the data acquisition system. Consequently is developed the scheme and components needed for circulation, heating and humidification of the gases used in the process as well as the location of sensors and actuators. Finally the document presents the list of algorithms and an appendix with information about Labview software.

Adapting micro-economy of energy corporations to macroeconomy policies aiming at a sustainable economy

Esta Tesis surgi�� ante la intensidad y verosimilitud de varias se��ales o ���warnings��� asociadas a pol��ticas dirigidas a reducir el peso del petr��leo en el sector energ��tico, tanto por razones econ��micas, como geopol��ticas, como ambientales. Como tal Tesis se consolid�� al ir incorporando elementos novedosos pero esenciales en el mundo petrol��fero, particularmente las ���tecnolog��as habilitantes���, tanto de incidencia directa, como el ���fracking��� como indirecta, del cual es un gran ejemplo el Veh��culo El��ctrico (puro). La Tesis se defini�� y estructur�� para elaborar una serie de indagaciones y disquisiciones, que comportaran un conjunto de conclusiones que fueran ��tiles para las corporaciones energ��ticas. Tambi��n para la comprensi��n de la propia evoluci��n del sector y de sus prestaciones t��cnicas y econ��micas, de cara a dar el servicio que los usuarios finales piden. Dentro de las tareas anal��ticas y reflexivas de la Tesis, se acu��aron ciertos t��rminos conceptuales para explicar m��s certeramente la realidad del sector, y tal es el caso del ���Investment burden���, que pondera la inversi��n espec��fica (���/W) requerida por una instalaci��n, con la duraci��n del per��odo de construcci��n y los riesgos tanto tangibles como regulatorios. Junto a ello la Tesis propone una herramienta de estudio y prognosis, denominada ���Market integrated energy efficiency���, especialmente aplicable a dicotom��as. Tal es el caso del coche t��rmico, versus coche el��ctrico. El objetivo es optimizar una determinada actividad energ��tica, o la productividad total del sector. Esta Tesis propone varias innovaciones, que se pueden agrupar en dos niveles: el primero dentro del campo de la Energ��a, y el segundo dentro del campo de las corporaciones, y de manera especial de las corporaciones del sector hidrocarburos. A nivel corporativo, la adaptaci��n a la nueva realidad ser�� funci��n directa de la capacidad de cada corporaci��n para desarrollar y/o comprar las tecnolog��as que permitan mantener o aumentar cuota de mercado. Las conclusiones de la Tesis apuntan a tres opciones principalmente para un replanteamiento corporativo: - Diversificaci��n energ��tica - Desplazamiento geogr��fico - Benefici��ndose de posibles nuevos nichos tecnol��gicos, como son: ��� En upstream: Recuperaci��n estimulada de petr��leo mediante uso de energ��as renovables ��� En downstream: Aditivos orientados a reducir emisiones ��� En gesti��n del cambio: Almacenamiento energ��tico con fines operativos Algunas pol��ticas energ��ticas siguen la tendencia de crecimiento cero de algunos pa��ses de la OCDE. No obstante, la realidad mundial es muy diferente a la de esos pa��ses. Por ejemplo, seg��n diversas estimaciones (basadas en bancos de datos solventes, referenciados en la Tesis) el n��mero de veh��culos aumentar�� desde aproximadamente mil millones en la actualidad hasta el doble en 2035; mientras que la producci��n de petr��leo s��lo aumentar�� de 95 a 145 millones de barriles al d��a. Un aumento del 50% frente a un aumento del 100%. Esto generar�� un curioso desajuste, que se empezar�� a sentir en unos pocos a��os. Las empresas y corporaciones del sector hidrocarburos pueden perder el monopolio que atesoran actualmente en el sector transporte frente a todas las dem��s fuentes energ��ticas. Esa p��rdida puede quedar compensada por una mejor gesti��n de todas sus capacidades y una participaci��n m��s integrada en el mundo de la energ��a, buscando sinergias donde hasta ahora no hab��a sino distanciamiento. Los productos petrol��feros pueden alimentar cualquier tipo de maquina t��rmica, como las turbinas Brayton, o alimentar reformadores para la producci��n masiva de H2 para su posterior uso en pilas combustible. El almacenamiento de productos derivados del petr��leo no es ning��n reto ni plantea problema alguno; y sin embargo este almacenamiento es la llave para resolver muchos problemas. Es posible que el comercio de petr��leo se haga menos vol��til debido a los efectos asociados al almacenamiento; pero lo que es seguro es que la eficiencia energ��tica de los usos de ese petr��leo ser�� m��s elevada. La Tesis part��a de ciertas amenazas sobre el futuro del petr��leo, pero tras el an��lisis realizado se puede vislumbrar un futuro prometedor en la fusi��n de pol��ticas medioambientales coercitivas y las nuevas tecnolog��as emergentes del actual portafolio de oportunidades t��cnicas. ABSTRACT This Thesis rises from the force and the credibility of a number of warning signs linked to policies aimed at reducing the role of petroleum in the energy industry due to economical, geopolitical and environmental drives. As such Thesis, it grew up based on aggregating new but essentials elements into the petroleum sector. This is the case of ���enabling technologies��� that have a direct impact on the petroleum industry (such as fracking), or an indirect but deep impact (such as the full electrical vehicle). The Thesis was defined and structured in such a way that could convey useful conclusions for energy corporations through a series of inquiries and treatises. In addition to this, the Thesis also aims at understating la evolution of the energy industry and its capabilities both technical and economical, towards delivering the services required by end users. Within the analytical task performed in the Thesis, new terms were coined. They depict concepts that aid at explaining the facts of the energy industry. This is the case for ���Investment burden���, it weights the specific capital investment (���/W) required to build a facility with the time that takes to build it, as well as other tangible risks as those posed by regulation. In addition to this, the Thesis puts forward an application designed for reviewing and predicting: the so called ���Market integrated energy efficiency���, especially well-suited for dichotomies, very appealing for the case of the thermal car versus the electric car. The aim is to optimize energy related activity; or even the overall productivity of the system. The innovations proposed in this Thesis can be classified in two tiers. Tier one, within the energy sector; and tier two, related to Energy Corporation in general, but with oil and gas corporations at heart. From a corporate level, the adaptation to new energy era will be linked with the corporation capability to develop or acquire those technologies that will yield to retaining or enhancing market share. The Thesis highlights three options for corporate evolution: - diversification within Energy - geographic displacement - profiting new technologies relevant to important niches of work for the future, as: o Upstream: enhanced oil recovery using renewable energy sources (for upstream companies in the petroleum business) o Downstream: additives for reducing combustion emissions o Management of Change: operational energy storage Some energy policies tend to follow the zero-growth of some OECD countries, but the real thing could be very different. For instance, and according to estimates the number of vehicles in use will grow from 1 billion to more than double this figure 2035; but oil production will only grow from 95 million barrel/day to 145 (a 50% rise of versus an intensification of over a 100%). Hydrocarbon Corporation can lose the monopoly they currently hold over the supply of energy to transportation. This lose can be mitigated through an enhanced used of their capabilities and a higher degree of integration in the world of energy, exploring for synergies in those places were gaps were present. Petroleum products can be used to feed any type of thermal machine, as Brayton turbines, or steam reformers to produce H2 to be exploited in fuel cells. Storing petroleum products does not present any problem, but very many problems can be solved with them. Petroleum trading will likely be less volatile because of the smoothing effects of distributed storage, and indeed the efficiency in petroleum consumption will be much higher. The Thesis kicked off with a menace on the future of petroleum. However, at the end of the analysis, a bright future can be foreseen in the merging between highly demanding environmental policies and the relevant technologies of the currently emerging technical portfolio.

Self-organized colloidal quantum dots and metal nanoparticles for plasmon-enhanced intermediate-band solar cells

A colloidal deposition technique is presented to construct long-range ordered hybrid arrays of self-assembled quantum dots and metal nanoparticles. Quantum dots are promising for novel opto-electronic devices but, in most cases, their optical transitions of interest lack sufficient light absorption to provide a significant impact in their implementation. A potential solution is to couple the dots with localized plasmons in metal nanoparticles. The extreme confinement of light in the near-field produced by the nanoparticles can potentially boost the absorption in the quantum dots by up to two orders of magnitude. In this work, light extinction measurements are employed to probe the plasmon resonance of spherical gold nanoparticles in lead sulfide colloidal quantum dots and amorphous silicon thin-films. Mie theory computations are used to analyze the experimental results and determine the absorption enhancement that can be generated by the highly intense near-field produced in the vicinity of the gold nanoparticles at their surface plasmon resonance. The results presented here are of interest for the development of plasmon-enhanced colloidal nanostructured photovoltaic materials, such as colloidal quantum dot intermediate-band solar cells.