Analysis of Li-Air Battery: Voltage Loss due to Insoluble Discharge Formation

In this paper, we present analysis of air cathode performance, taking into account both electrode passivation and transport resistance raised by insoluble products. Both effects are theoretically evaluated and compared. Validation is carried out against experimental data under low currents. The effects of electrode pore structure, such as porosity and tortuosity, on both the influence of insoluble precipitates and discharge capability are investigated.

Novel Structured Electrolyte for All-Solid-State Lithium Ion Batteries

In this study, a multi-layer structure solid electrolyte (SE) for all-solid-state electrolyte lithium ion batteries (ASSLIBs) was fabricated and characterized. The SE was fabricated by laminating ceramic electrolyte Li1.3Al0.3Ti1.7(PO4)3 (LATP) with polymer (PEO)10-Li(N(CF3SO2)2 electrolyte and gel-polymer electrolyte of PVdF-HFP/ Li(N(CF3SO2)2. It is shown that the interfacial resistance is generated by poor contact at the interface of the solid electrolytes. The lamination protocol, material selection and fabrication method play a key role in the fabrication process of practical multi-layer SEs.

Integrated Anaerobic Digester and Fuel Cell Power Generation System for Community Use

New York State is expected to experience future population growth that is increasingly concentrated in urban areas, where there is already a heavy burden on the existing energy, water and waste management infrastructure. To meet aggressive environmental standards (such as that established by the State’s “80x50” goal), future electrical power capacity must produce substantially fewer greenhouse gas emissions than currently generated by coal- or natural gas-fired power plants. Currently, biogas is combusted to produce heat and electricity via an internal combustion engine generator set. A conventional internal combustion engine generator set is 22–45 % efficient in converting methane to electricity, thus wasting 65–78 % of the biogas energy content unless the lower temperature heat can be recovered. Fuel cells, on the other hand, are 40–60 % efficient in converting methane to electrical energy, and 80–90 % efficient for cogeneration if heat (> 400 °C) is recovered and utilized for heating and cooling in the community power system. This current research studies the feasibility of a community biomass-to-electricity power system which offers significant environmental, economic and resilience improvements over centrally-generated energy, with the additional benefit of reducing or eliminating disposal costs associated with landfills and publicly-owned treatment works (POTWs). Flame Fuel Cell (FFC) performance was investigated while modifying biogas content and fuel flow rate. A maximum power density peak at 748 mWcm-2 and an OCV of 0.856 V was achieved. It should be noted that the performance obtained with the model biofuel is comparable to the performances of direct methane fueled DC-SOFC and SC-SOFC. The common trends also concluded an acceptable range for optimal performance. Although the methane to CO2 ratios of 3:7 and 2:8 produced power, they are not the strongest ratios to have optimal performance, meaning that operation should stay between the 6:4/4:6 ratio range. Lastly, the amount of air added to the biogas mixture is crucial to achieving the optimal performance of the cell. The data obtained confirmed the feasibility of a biofuel driven fuel cell CHP device capable of achieving higher efficiency than existing technologies. The significant power output produced from the sustainable biogas composition is competitive with current hydrocarbon fuel sources. This idea can be expanded for a community waste management infrastructure.

Flame-Assisted Fuel Cell Operating With Methane for Combined Heating and Micro Power

Solid Oxide Fuel Cells (SOFCs) operating in a Flame-assisted Fuel Cell (FFC) setup have potential for Combined Heating and micro Power applications. The feasibility of a FFC furnace operating with natural gas is investigated by using methane/ air flames. The confrontation between the FFCs operating temperature and fuel concentration under various conditions was investigated which uncovered the complex performance behavior. Variations in the fuel/ air equivalence ratio, fuel flow rate and distance between the FFC anode and burner outlet were studied. A critical distance for FFC placement above the burner outlet was uncovered, which has a significant impact on the FFCs performance. A high power density of 791mW.cm−2 was achieved which is comparable to the dual chamber SOFC and single chamber SOFC. Carbon coking was observed on the anode surface, but was not detrimental to FFC performance during testing.

A One-Dimensional Modelling Approach for Planar Cylindrical Solid Oxide Fuel Cell

In this paper a 1-D steady-state model of a planar cylindrical Solid Oxide Fuel Cell (SOFC) is described. The SOFC 1-D model developed has been applied for both co-flow and counter-flow configurations. The computational domain selected is a symmetrical single cell slice with an angle of twenty degrees (i.e. one eighteen of the entire cell). The cell has been divided into computational units in the radial direction, for each of them energy, mass and electrochemical conservation equations have been solved. The cell is considered non-adiabatic with heat conduction inside the solid material and convective-radiative heat transfer mechanism between the outer section and the surrounding gases. Moreover, at the cell outlet the residual fuel mixes with the surrounding gases and is completely burnt (afterburning). The 1-D model has been verified making use of literature data generated from 3-D model of a planar cylindrical SOFC. The results obtained confirmed the good performance of the model developed and its applicability in a computational framework for the development of either control or diagnosis algorithm.

Comparisons of Performances and Liquid Water Distributions Within Bio-Inspired and Single-Serpentine PEM Fuel Cell Channels

Flow field design in Proton Exchange Membrane (PEM) fuel cells is a major area of research for performance improvement. Bio-inspired flow field designs are a relatively recent development in fuel cell technology evolution. These novel designs have potential for performance improvements by effective distribution of reactant gases with better water management capabilities. This work investigates the performance and water distribution in a bio-inspired flow field design, formulated using Murray’s law and mimicking a typical leaf venation pattern, in comparison to a conventional single serpentine design. Experiments were conducted using a transparent fuel cell with copper as the conductive channel and current collector. The results indicated the superior performance of the bio-inspired design with a 30% increase in peak power density in comparison to the single serpentine design. Additionally, the flow regimes based on two-phase flows in micro channels were identified and their effects on fuel cell stability were determined.

Investigation of Gas Diffusion Layer Properties Using X-Ray Microtomography

An essential part of proton exchange membrane fuel cells (PEMFCs) is the gas diffusion layer (GDL), which provides pathways for by-products to be removed from PEMFCs. One of the main properties of GDLs is porosity. The two widely used experimental methods for finding the porosity of GDLs are mercury intrusion porosimetry (MIP) and method of standard porosimetry (MSP). In addition to these methods, the porosity of GDLs can be calculated based on the high resolution 3D images that are acquired using X-ray microtomography (μXCT) as shown in recent studies (e.g., [7,12]). Despite the general success of using μXCT to measure GDL porosity, different porosity values have been reported for similar GDLs. These variations are due to different assumptions made for determining the surface of the sample, and hence, its external dimensions. In this research, current methods used for calculating porosity of GDLs from μXCT images are discussed, and a new surface identification method based on a rolling ball algorithm is introduced. The main advantage of this new method is that variations in surface topology or roughness are taken into account when calculating porosity. The new method is not only applicable to GDLs, but can be applied to characterize a wide range of highly porous media.

Model-Based Analysis of Electrode Design in a Direct Methanol Microscale Fuel Cell

The performance of microscale fuel cells with high-aspect-ratio electrodes, defined as the ratio of electrode length to width, is often limited by the depletion of fuel along the length of the anode. Here we present a mathematical model to study electrode aspect ratio in a direct methanol microscale fuel cell. The model is supported with experimental data to show that low-aspect-ratio electrodes achieve higher power densities via improved mass transport to electrodes. The influence of electrode width on overall cell performance was investigated by varying the catalyst deposition region in low-aspect-ratio electrodes. The performance of our experimental fuel cell is consistent with our modeling studies, achieving a maximum power density of 25.3 mW/cm2 at room temperature with 1 M methanol. The model presented here can be used to further improve the geometric design of electrodes in a microscale fuel cell.

Needs and Approaches for Novel Characterization of Direct Hybrid Fuel Cell/Gas Turbines

Solid oxide fuel cell (SOFC)/ gas turbine (GT) hybrid systems possess the capacity for unprecedented performances, such as electric efficiencies nearly twice that of conventional heat engines at variable scale power ratings inclusive of distributed generation. Additionally, these hybrids can have excellent operational flexibility with turndowns possibly as great as 85%. There are, however, developmental needs such as turbomachinery characterization and re-design. A leading example is that of greater propensity to have occurrences of stall-surge given the significantly different operating environment in contrast to conventional heat engines. Additionally, dynamic variation in power generation has to be done with significant a priori insight to avoid thermomechanical threats to cell stack and turbomachinery. State-of-the-art approaches involving hardware-in-the-loop simulation and, ultimately, additive manufacturing are being pursued to enable such characterization and re-design considerations given variable and dynamic operability requirements. Compressor performance in hybrid systems has been characterized at the United States National Energy Technology Laboratory (NETL), inclusive of a capability of feed forward hardware-in-the-loop simulation of hybrid systems under dynamic conditions and a capability of replacing turbine and compressor components at a relatively low cost. This paper highlights some of the simulation results, and the net result is an approach that addresses hybrid system developmental needs for accommodating generation transients.