Low pH, high salinity: too much for Microbial Fuel Cells?

Twelve single chambered, air-cathode Tubular Microbial Fuel Cells (TMFCs) have been filled up with fruit and vegetable residues. The anodes were realized by means of a carbon fiber brush, while the cathodes were realized through a graphite-based porous ceramic disk with Nafion membranes (117 Dupont). The performances in terms of polarization curves and power production were assessed according to different operating conditions: percentage of solid substrate water dilution, adoption of freshwater and a 35mg/L NaCl water solution and, finally, the effect of an initial potentiostatic growth. All TMFCs operated at low pH (pH$=3.0 \pm 0.5$), as no pH amendment was carried out. Despite the harsh environmental conditions, our TMFCs showed a Power Density (PD) ranging from 20 to 55~mW/m$^2 \cdot$kg$_{\text{waste}}$ and a maximum CD of 20~mA/m$^2 \cdot$kg$_{\text{waste}}$, referred to the cathodic surface. COD removal after a $28-$day period was about $45 \%$. The remarkably low pH values as well as the fouling of Nafion membrane very likely limited TMFC performances. However, a scale-up estimation of our reactors provides interesting values in terms of power production, compared to actual anaerobic digestion plants. These results encourage further studies to characterize the graphite-based porous ceramic cathodes and to optimize the global TMFC performances, as they may provide a valid and sustainable alternative to anaerobic digestion technologies.Comment: 13 pages, 10 Figure

Hydrogen-based technologies in maritime sector: technical analysis and prospective

The maritime transportation sector is one of the main contributors to global emissions of greenhouse gases (GHGs). The International Maritime Organization (IMO) has adopted a strategy to reduce these emissions from international shipping >50% by 2050, compared to 2008’s emissions. Therefore, ship owners need to adopt solutions to bring emissions within these and other future limits by means of environmentally friendly fuels (hydrogen or hydrogen carriers) and high efficiency propulsion technologies (fuel cells). This paper focuses on the replacement of the conventional Diesel genset installed on a hybrid small-size ferry, with an innovative system based on PEMFC technology. A real case scenario is investigated: the total energy/power demand of the vessel is determined basing on a typical operational profile. Then, a preliminary redesign of its powertrain configuration is proposed along with an energy management strategy. The analysis has allowed to define the hydrogen consumption for a daily operation. Finally, different storage technologies involving both compressed and liquefied hydrogen have been considered and compared, in order to identify ship’s weight and space requirements

Coupling of Biomass Gasification and SOFC – Gas Turbine Hybrid System for Small Scale Cogeneration Applications☆

Abstract In this study the performances of small cogeneration power plants fed by biomass and based on conventional and advanced technologies are presented. Three system configurations have been considered and analyzed. They are characterized by: a) a biomass gasification (G) unit, based on down-draft technology; b) a power unit, based on the SOFC technology or on the micro gas turbine (MGT) technology or on a hybrid configuration SOFC-MGT; c) a thermal recovery unit. The energy analysis of the proposed power plants has been conducted by using thermochemical/thermodynamic models able to study the integrated systems and each unit in terms of operating and performance parameters

Romania\u27s Participation to the European Assessment Project Titled HyUnder, Multi-Criterial Analyses of Salt Cavern Locations

The scope of the work is to assess the potential, the actors and relevant business cases for large scale storage of renewable electricity by hydrogen underground storage in Romania. This presentation intends to provide a picture of the multi-criterial analyses of salt cavern locations in Romania. The energy sector is facing with the necessity to store large energy quantities for short to long term in order to adapt to the increasingly intermittent renewable energy. The results of this presentation have originated from an ongoing European assessment project by the name of HyUnder (FCH JU, grant 303417) regarding utilization of salt caverns for hydrogen underground storage. Currently, main uses of salt caverns include storage of hydrocarbons or wastes disposal. Salt caverns have stirred the interest of the scientific community regarding the potential applications in hydrogen economy. Romania has active mines or caverns and others closed, many of them have the potential to be used from hydrogen storage. These facts represent an interested situation in order to initiate studies or assessments of the potential hydrogen underground storage. The salt mines, hydrogen producers, renewable energy sources and research centers with high qualified scientists, represent essentially elements for new type of studies regarding hydrogen economy. In the context of scientific community\u27s efforts from Romania to assert active in the area of hydrogen technologies, this approach can certainly constitutes an attractive example for pan-European cooperation. The work disclaims the technic multi-criterial analyses of salt cavern locations regarding hydrogen underground storage. The introduction of hydrogen into economy offers the possibility to provide a number of advantages: sustainable development, valorization of local resources and improvement of competitiveness. The opportunities and viabilities of salt cavern locations are analyzed

A renewable energy and hydrogen storage system for residential electricity supply

Because of the intermittent behavior of renewable sources, efficient, reliable and clean energy storage technologies are needed to achieve a more stable and secure energy supply. In this context, hydrogen technologies play a key role because they can store large amount of energy for long time. In this study, a hydrogen-based electrical energy storage system, integrated with a solar power plant, is designed and analyzed from the energy perspective. The system consists of a photovoltaic power plant, an alkaline electrolysis unit, metal hydride tanks for hydrogen storage, a Li-ion battery unit and a polymer electrolyte membrane fuel cell module. The system is conceived for supplying a residential user. A numerical model is developed for sizing the system’s components and for evaluating their behaviors in terms of produced/stored electricity and hydrogen production. In this purpose, a sensitivity analysis varying PV plant size as well as the Li-ion battery capacity is performed for achieving the best compromise in terms of energy supply among all the considered power sources

NON-CONVENTIONAL WASTE-DERIVED FUELS FOR MOLTEN CARBONATE FUEL CELLS

Global energy consumption is expected to increase dramatically in the next decades, driven by the rising of the standards of living and by the growth of population worldwide. The increased need of energy will require enormous growth in energy generation capacity, more secure and diversified energy sources, and a successful strategy to control and to reduce greenhouse gases emissions. There is a huge challenge to provide an everyday product, energy – that is taken absolutely for granted – in a radically different, difficult, but fundamentally improved way, at accustomed and competitive cost. Also on the demand side severe corrections have to be undertaken: product and associated waste flows have to be interpreted differently, efficiency and sustainability becoming key issues. One of the most immediate, and effective, ways to tackle this challenge is to minimize losses and waste by maximizing the exploitation efficiency of the resources that are utilised. One valid way to reduce fossil fuels dependence and demand, for example, is the use of alternative or non-conventional fuels, derived from waste or biomass. These fuels, by nature of their transient origins, are generally poor in energy content, which imposes localized deployment and maximum efficiency in their utilization in order to obtain a useful amount of work and/or heat. In the effort to maximize the energetic yield from alternative energy sources like waste or biomass, and wanting to minimize environmental impact in terms of polluting or CO2 emissions, the coupling of Molten Carbonate Fuel Cells (MCFCs) to the fuel gas produced from these sources is an attractive option. Combining these resources with fuel cell applications would provide a significant contribution to environmentally friendly, efficient energy use. Currently, biofuels from waste and biomass are mainly used in engines and turbines with fairly low efficiencies and generate significant amounts of regulated pollutants (NOx, SOx and particulates). Replacement of these conventional heat engines with MCFCs would allow a more efficient use of biofuels but, more significantly, would reduce NOx, SOx and particulates to insignificant levels and increase CO2 benefits. This work is part of an ambitious Research Project under the Agreement between ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development) and MSE (Italian Ministry of Economic Development) on the MCFCs Research and Development. One of the main topic of this project is the use of MCFC with biofuels (biogas from anaerobic digestion and syngas from biomass gasification). The current Ph.D. work is finalized towards the coupling of a molten carbonate fuel cell (MCFC) to an anaerobic digestion process of organic residues or sludge from a wastewater treatment plant, and it has been carried out under the supervision of the Hydrogen & Fuel Cell Project, Energy Technologies, Renewable Energy Sources and Energy Saving Department, ENEA, Rome, Italy. The biogas produced through anaerobic digestion is ideally suited for electrochemical conversion in an MCFC thanks to the large content of readily reformable methane and the necessary diluent CO2. The crucial link between these two technologies (anaerobic digestion and the MCFC), however, is formed by the gas clean-up step. This is because the raw produced biogas contains trace elements that originate from the organic nature of the feedstock, and that have detrimental effects on fuel cell performance and durability. The most common contaminant contained in the biogas is hydrogen sulphide (H2S), relevant for harmful effects, both on the fuel cell electrodes as on the reforming catalysts. A large part of the current study was dedicated to the particular effects of H2S on the MCFC anode. In the last years several studies on the effects of H2S on the MCFC anode are reported in the literature, but the knowledge is still incomplete and requires more in deep study. Based on this knowledge a full experimental study was performed looking at the accurate knowledge of the conditions which are deleterious to MCFC, in order to facilitate safe and reliable operation of the fuel cell. A systematic experimental campaign was carried out, the results of which will be presented and discussed, showing the effects and implications of cell poisoning with H2S observed at several different levels of diagnosis (chemical, electrochemical, electrical, material). The objective is to ultimately identify the true, effective tolerance limits of current MCFC materials, especially as regards different concentrations of H2S that can occur due to composition variations of the produced biogas. In order to achieve this objective, many hours of long-term experimentation has been required and different single cells have been operated in MCFC Laboratory, at Center for Fuel Cell Research, Energy & Environment Research Division, KIST – Korea Institute of Science and Technology, Seoul, South Korea. The results of this experimental study allow to identify the main effect on the MCFC anode side by H2S and also to evaluate the important role played by the Electrochemical Impedance Spectroscopy (EIS) as added value for the interpretation of this results. The impedance measurements are carried out to identify the processes which take place in the anode and to better understand the reversibility of sulphur poisoning under the regeneration processes. After the technical approach, it’s relevant to consider also the economic feasibility to understand how and when the MCFC systems fed with biogas can be competitive with other technologies currently present on the market, as Internal Combustion Engine and Gas Turbine. A Cost-Benefit model will be performed and, based on it, a technical-economical analysis will be illustrated and discussed, considering the use of biogas in a 1.4 MW MCFC plant, in order to identify the most important economic parameters that affect the use of biogas in MCFC

Comprehensive Review on Fuel Cell Technology for Stationary Applications as Sustainable and Efficient Poly-Generation Energy Systems

Fuel cell technologies have several applications in stationary power production, such as units for primary power generation, grid stabilization, systems adopted to generate backup power, and combined-heat-and-power configurations (CHP). The main sectors where stationary fuel cells have been employed are (a) micro-CHP, (b) large stationary applications, (c) UPS, and IPS. The fuel cell size for stationary applications is strongly related to the power needed from the load. Since this sector ranges from simple backup systems to large facilities, the stationary fuel cell market includes few kWs and less (micro-generation) to larger sizes of MWs. The design parameters for the stationary fuel cell system differ for fuel cell technology (PEM, AFC, PAFC, MCFC, and SOFC), as well as the fuel type and supply. This paper aims to present a comprehensive review of two main trends of research on fuel-cell-based poly-generation systems: tracking the market trends and performance analysis. In deeper detail, the present review will list a potential breakdown of the current costs of PEM/SOFC production for building applications over a range of production scales and at representative specifications, as well as broken down by component/material. Inherent to the technical performance, a concise estimation of FC system durability, efficiency, production, maintenance, and capital cost will be presented

Fuel Cells in the Waste-to-Energy Chain: Distributed Generation Through Non-Conventional Fuels and Fuel Cells

As the availability of fossils fuels becomes more limited, the negative impact of their consumption becomes an increasingly relevant factor in our choices with regards to primary energy sources. The exponentially increasing demand for energy is reflected in the mass generation of by-products and waste flows which characterize current society’s development and use of fossil sources. The potential for recoverable material and energy in these ever-increasing refuse flows is huge, even after the separation of hazardous constituent elements, allowing safe and sustainable further exploitation of an otherwise 'wasted' resource.  Fuel Cells in the Waste-to-Energy Chain explores the concept of waste-to-energy through a 5 step process which reflects the stages during the transformation of  refuse flows to a valuable commodity such as clean energy. By providing selected, integrated alternatives to the current centralized, wasteful, fossil-fuel based infrastructure, Fuel Cells in the Waste-to-Energy Chain explores how the concept of waste-to-energy can be constructed and developed into a realistic solution. The entire spectrum of current and future energy problems is illuminated through the explanation of the operational, integration and marketing implications of high efficiency technological solutions using the real context of developed regions such as Europe. Up-to-date reviews are provided on the status of technology and demonstration, implementation and marketing perspectives. The detailed technological information and insight gathered from over twenty years of experience in the field makes Fuel Cells in the Waste-to-Energy Chain a valuable resource for all engineers and researchers in the fields of energy supply systems and waste conversion, as well as providing a key reference for discussions by policy makers, marketing experts and industry developers working in energy supply and waste management