EU HARMONISED TEST PROTOCOLS FOR PEMFC MEA TESTING IN SINGLE CELL CONFIGURATION FOR AUTOMOTIVE APPLICATIONS

PEMFC due to their high energy density, low operating temperature and high efficiency are considered to be very suitable for vehicle propulsion. In such applications, fuel cells could encounter operating conditions which are severe to the materials involved. Fuel cell testing shall as close as possible reflect conditions encountered in real life. To enable a fair comparative assessment of the performance of MEA under operating conditions foreseen in future automotive applications, a set of representative operating conditions in addition with a test methodology is proposed. The aim of a unified set of harmonised operating conditions is to comparatively test and evaluate the performance of different MEAs in single cells. The current document is the result of a cumulative effort of industry and research organisations participating in FCH-JU funded projects for automotive applications, in establishing a harmonised test protocol for assessing PEMFC performance and durability at a single cell level. This document presents a set of reference operating conditions such as temperature, pressure, humidification, gas flow and composition at the fuel and oxidant inlet representative for future automotive applications. It also defines boundaries of these conditions within which the cell is expected to operate. While not specifying single cell design details, cell operation in counter flow is mandatory for comparative assessment. A methodology is established to examining the relative influence that the individual operating parameters exert on the MEA performance in single cell configuration once the cell is subjected to the more challenging boundary conditions defined in this document which are also called as stressor conditions. In addition to operating conditions, the most likely stressor conditions for single cell testing could be identified as follows: Load cycling, Mechanical effects, Fuel Air contaminants (impurities), and Environmental Conditions. In this document the focus is on stressors related to Operating Conditions and Load Cycling. Deviations from the automotive reference Operating Conditions may result in changes to both cell performance and durability. In principle the influence of each stressor on cell performance could be studied individually. However, since a number of stressors are inter-linked, (changing the value of one stressor could inevitably change the value of another), the stressor tests have been grouped into four families of Stressors, namely: Cell Temperature Stressor Tests, Reactants Gas Inlet Humidification Stressor Tests, Reactants Gas Inlet Pressure Stressor Tests, Oxidant Stoichiometry Stressor Tests. The aim of these tests is to study the effect of each stressor on the the cell voltage at three different current densities representative of activation, ohmic polarization and mass transfer regimes as a function of each stressor condition. The successful operation of a fuel cell depends not only on its performance but also on its durability. Fuel cell durability is evaluated through endurance testing by applying a repetitive load profile to the cell and measuring performance degradation in terms of cell voltage decrease as function of operating hours. To assess the cell degradation rate a dynamic load cycle for endurance testing is proposed. The Fuel Cell Dynamic Load Cycle is used in this document and is derived from the New European Driving Cycle modified for fuel cell applications. In addition to the definition of representative reference and stressor operating conditions, the document also provides a rationale for their selection. The use of sound science-based, industry-endorsed test methodologies and protocols enables true comparison of MEAs originating from different sources either commercial or developed within different projects. It also enables evaluating the rate of progress achieved towards reaching agreed technology performance targets.JRC.F.2-Energy Conversion and Storage Technologie

Fuel Cell Testing Protocols: An International Perspective

An overview of international polymer-electrolyte fuel cell (PEMFC) test procedures is presented. This overview is the first step in the global harmonization of testing methods. Many techniques and procedures determining stack performance and durability are discussed. Each approach has differences that may or may not impact the data and data quality. Through experiments, it was found that differences in the results from two methods for measuring sequential polarization curves are minimal. Answers to questions regarding differences in the aging duty cycles need to be determined experimentally. The results of these experiments are expected to help the harmonization process, to facilitate the understanding of test results, and, possibly, to accelerate the commercialization of PEMFCs.JRC.F.2-Cleaner energ

Influence of moisture contents on the fast pyrolysis of trommel fines in a bubbling fluidized bed reactor

In this study, the effect of moisture contents [2.69 wt% (bone-dry), 5 wt% and 10 wt%] on product yields and process conversion efficiency during fast pyrolysis of a pre-treated trommel fines feedstock was investigated at 500 °C. Experiments were carried out using a 300 g h −1 bubbling fluidised bed rig. Yields of organic liquids ranged from 15.2 to 19.6 wt% of feedstock, which decreased with increasing moisture content. Hence, the bone-dry feedstock gave the maximum yield and consequently the highest process conversion efficiency of 43%. Increased moisture content also led to increase formation of unidentified gas products, indicating increased conversion of organic liquids. Due to the high ash content of the feedstocks, about 52 wt% solid residues, containing around 82% ash was recovered in the char pot in each case. Hence, to maximize oil yields during fast pyrolysis, trommel fines would require extensive drying to remove the original 46 wt% moisture as well as reducing the ash content considerably. XRF analysis of the ash in the feedstock and solid residues showed that the main elements present included Ca, Si, Fe, Pb, K, Cl and Al. Apart from the presence of Pb (which may be from the glass contents of the feedstock), the solid residues could be used for land reclamation or co-incinerated at cement kilns for cement manufacture

Heat pipe based municipal waste treatment unit for home energy recovery

A heat pipe based pyrolysis chamber has been developed and tested as an efficient, cost effective and space saving municipal waste treatment unit. The performance of the chamber was evaluated based on the temperature distributions inside the chamber, its electricity consumption and the chemical characteristics of the final pyrolysis products (bio-chars and pyro-oils) obtained from the process and validated by three test runs. In all the three tests, the type of waste treated was municipal waste obtained from households. In addition, special cases of challenging waste configurations, such as mixed domestic plastics and PVC are reported. The chemical analysis of the pyrolysis and the ash residues from the municipal solid waste showed no toxic elements in their composition. The main component of the char was calcium, the fluid oil obtained from the initial stages of pyrolysis had a similar composition to that of water, while the dense oil produced during the final stage of the process showed traces of iron and a potential composition match to commercial additive oils. The chemical analysis of the chars and ash obtained from the mixed domestic waste showed no toxicity for the mixed plastic char but a potential toxicity of the PVC char due to the existence of lead and chlorine. Calculations regarding the coefficient of performance (COP) of the heat pipe based pyrolysis unit indicated that the COP decreased with the increase of moisture content of the waste stream. For 0% moisture content in the waste stream the COP of the unit was 9.4 and the carbon footprint of the unit was 0.0782 kg CO2e per kg of treatment. On the other hand, for a maximum moisture content of 100% the COP was 0.53 and the CO2 emissions were 0.3873 kg CO2e per kg of treatment

Multi-gene genetic programming based predictive models for municipal solid waste gasification in a fluidized bed gasifier

A multi-gene genetic programming technique is proposed as a new method to predict syngas yield production and the lower heating value for municipal solid waste gasification in a fluidized bed gasifier. The study shows that the predicted outputs of the municipal solid waste gasification process are in good agreement with the experimental dataset and also generalise well to validation (untrained) data. Published experimental datasets are used for model training and validation purposes. The results show the effectiveness of the genetic programming technique for solving complex nonlinear regression problems. The multi-gene genetic programming are also compared with a single-gene genetic programming model to show the relative merits and demerits of the technique. This study demonstrates that the genetic programming based data-driven modelling strategy can be a good candidate for developing models for other types of fuels as well

Energy recovery by fast pyrolysis of pre-treated trommel fines derived from a UK-based MSW material recycling facility

In this experimental study, a physically pre-treated trommel fines feedstock, containing 44 wt% non-volatiles (ash and fixed carbon) and 56 wt% volatile matter (dry basis), was subjected to fast pyrolysis to recover energy from its organic load, using a 300 g h−1 bubbling fluidized bed (BFB) fast pyrolysis rig. A physical pre-treatment method (including crushing, grinding and sieving) was used to prepare a 0.5–2 mm sized trommel fines feedstock to make it suitable for fast pyrolysis in the BFB reactor. Experimental results from the fast pyrolysis process showed that the highest yield of organic liquid was obtained at around a temperature of 500 °C. However, both char and gas yields increased dramatically at temperatures above 500 °C, as a result of enhanced cracking of organic vapours, which reduced the yield of liquid products. Overall, energy recovery from the pyrolysis products (liquid and gas products as well as char pot residues) ranged from 63 to 70%, generally increasing with temperature. A large proportion of the high ash content (36 wt%) of the feedstock was found in the char pot (>62%), while smaller proportions were found in the reactor bed and some liquid products. The char pot ash residues composed mostly of non-hazardous earth materials and may be applied in bulk construction materials e.g. cement manufacture. Although, there was no problem with the pyrolysis rig during 1 h of operation, longer periods of operation would require periodic removal of accumulated solid residues and/or char pot modification to ensure continuous rig operation and process safety

Designing an optimised supply network for sustainable conversion of waste agricultural plastics into higher value products

Agricultural plastics are currently characterised by a predominantly linear take-make-dispose value chain, thus being a major stream of waste that contributes to significant environmental and economic issues. Therefore, policy makers have recently indicated the adoption of circular economy approaches as the way forward for plastics. This study addresses the problem of agricultural plastic waste as a major stream of landfilled waste by assessing the potential for recycling the plastic into higher value products through pyrolysis and by optimally designing the respective supply network to support this process. A Mixed Integer Linear Programming (MILP) model is developed to optimise the end-to-end supply network design, from the waste generation stage up to the end consumer of the produced material. The model is supported by experimental results on the pyrolysis performance for contaminated plastic samples. The model is applied in a case study of the Scottish agricultural sector to showcase its potential in assessing the feasibility and financial viability in addition to the positive environmental impact on agricultural plastic waste supply networks. The results demonstrate the potential of using the pyrolysis technology for agricultural plastic waste recycling as an example of a circular economy approach and the benefits of using the developed model for decision making purposes, as well as the potential for waste reduction and the implications for farmers’ operations