• Energy Research

Abstract A new type of planar fuel cell based on printed circuit board (PCB) technology has been developed. This planar design consists of an open cathode side which allows a completely passive, self-breathing operation of the fuel cell. Power densities of 100 mW/cm2 at 500 mV with hydrogen were achieved. Long-term operation for more than 1500 h has been demonstrated. The operation behavior of planar hydrogen in free-breathing PEMFC concerning stability, water management and temperature distribution are examined. The effects of diffusion layer thickness and cathode opening ratios on the performance of this fuel cell type were characterized. Moreover, the amount of water removed from the anode and the temperature distribution of the cathode side were determined.

Abstract The use of planar PEMFCs in printed circuit board (PCB) technology with a thickness of less than 3.5 mm are presented. This planar design consists of an open cathode side which allows a completely passive, self-breathing operation of the fuel cell. Power densities of 100 mW/cm 2 at 500 mV with hydrogen as a fuel were achieved. A steady operation with this type of fuel cell was demonstrated over a week without any cell flooding. Since the electrical conducting elements of PCBs usually are made of copper, corrosion in the wet environment of a PEMFC is expected. Thus, a significant degradation in performance of fuel cells made of plain copper PCBs was seen in long-term operation. In order to avoid corrosion, the copper layer has to be coated. Fuel cells in PCB design with diverse coatings were tested in long-term operations up to 1000 h under load. Moreover, corrosion currents have been determined by the use of potentiodynamic scans. Promising coatings are electroplated Cr and Ni and a combination of Ni/Au.

A theoretical study of a planar and self-breathing fuel cell is presented. This work contains the development of a mathematical model for planar self-breathing fuel cells, the validation of the model, and a study of the behavior of this type of fuel cell. The mathematical model presented is two-dimensional and nonisothermal. The validation of the model is performed by comparison of the measured overall performance of a planar self-breathing fuel cell to the predictions of the model. For this type of cell, the maximum power density is in the range between 0.5 and 0.4 V, so the model is applied to study the behavior of the reference cell at a cell voltage of 0.4 V. The results of this study show the gas distribution, the potential distribution, and the temperature distribution are influenced strongly by the geometric design of the cathode end plate. The charge generation rate in the active area of the cathode and anode is affected by the ribs of the cathode end plate. A strong nonuniformity of the current distribution in the cathode is found. © 2004 The Electrochemical Society. All rights reserved.

In the version of ‘Supplementary Data 1’ originally published with this Article, the units for the ‘Capacity|Electricity|*’ variables in the ‘Non_Investment_Annual’ tab were incorrectly given as EJ/yr; they should have read GW. This has now been corrected. Also, some of the variables listed in the ‘Non_Investment_Variable_Defs’ were not required and have therefore been removed.

Low-carbon investments are necessary for driving the energy system transformation that is called for by both the Paris Agreement and Sustainable Development Goals. Improving understanding of the scale and nature of these investments under diverging technology and policy futures is therefore of great importance to decision makers. Here, using six global modelling frameworks, we show that the pronounced reallocation of the investment portfolio required to transform the energy system will not be initiated by the current suite of countries’ Nationally Determined Contributions. Charting a course toward ‘well below 2 °C’ instead sees low-carbon investments overtaking fossil investments globally by around 2025 or before and growing thereafter. Pursuing the 1.5 °C target demands a marked upscaling in low-carbon capital beyond that of a 2 °C-consistent future. Actions consistent with an energy transformation would increase the costs of achieving the goals of energy access and food security, but reduce the costs of achieving air-quality goals.

Abstract The effect of the diffusion layer on the performance and mass transport in a direct methanol fuel cell at ambient conditions is reported. Carbon cloths with variable Teflon contents and pore sizes, carbon paper and a metal wire cloth were investigated. Membrane-electrode-assemblies (MEAs) for direct methanol fuel cells (DMFCs) prepared after an in-house receipt are used, giving reproducible results after a pre-treatment involving polarisation with hydrogen and air. Long-term effects and methanol crossover were also briefly investigated. Adding Teflon to the diffusion layer leads to better gas transport, as gas and liquid transport takes place in different paths. Thus, the fuel cell power output is more stable. The same effect was seen with increasing pore size. Carbon paper is found not suitable as a diffusion layer for low temperature DMFC. The metal wire cloth yielded best performance giving 15.8 mW cm−2.

AbstractThis paper presents a model‐based analysis of a proton exchange membrane fuel cell (PEMFC) with a planar design as the power supply for portable applications.The cell is operated with hydrogen and consists of an open cathode side allowing for passive, self‐breathing, operation. This planar fuel cell is fabricated using printed circuit board (PCB) technology. Long‐term stability of this type of fuel cell has been demonstrated.A stationary, two‐dimensional, isothermal, mathematical model of the planar fuel cell is developed. Fickian diffusion of the gaseous components (O2, H2, H2O) in the gas diffusion layers and the catalyst layers is accounted for. The transport of water is considered in the gaseous phase only. The electrochemical reactions are described by the Tafel equation. The potential and current balance equations are solved separately for protons and electrons. The resulting system of partial differential equations is solved by a finite element method using FEMLAB (COMSOL Inc.) software.Three different cathode opening ratios are realized and the corresponding polarization curves are measured. The measurements are compared to numerical simulation results. The model reproduces the shape of the measured polarization curves and comparable limiting current density values, due to mass transport limitation, are obtained.The simulated distribution of gaseous water shows that an increase of the water concentration under the rib occurs. It is concluded that liquid water may condense under the rib leading to a reduction of the open pore space accessible for gas transport. Thus, a broad rib not only hinders the oxygen supply itself, but may also cause additional mass transport problems due to the condensation of water.

Abstract An in-depth analysis of the energy consumption and CO2 emissions of the European glass industry is presented. The analysis is based on data of the EU ETS for the period 2005–2007 (Phase I). The scope of this study comprises the European glass industry as a whole and its seven subsectors. The analysis is based on an assignment of the glass installations (ca. 450) within the EU ETS to the corresponding subsectors and an adequate matching of the respective production volumes. A result is the assessment of the overall final energy consumption (fuel, electricity) as well as the overall CO2 emissions (process, combustion and indirect emissions) of the glass industry and its subsectors in the EU25/27. Moreover, figures on fuel mix as well as fuel intensity and CO2 emissions intensity (i.e. carbon intensity) are presented for each of the subsectors on aggregated levels and for selected EU Member States separately. The average intensity of fuel consumption and direct CO2 emissions of the EU25 glass industry decreased from 2005 to 2007 by about 4% and amounted in 2007 to 7.8 GJ and 0.57 t CO 2 per tonne of saleable product, respectively. The economic energy intensity was evaluated with 0.46 toe/1000€ (EU27).