Advanced Diagnostic Techniques Applied to Polymer Electrolyte Fuel Cells

Polymer electrolyte fuel cells (PEFCs) are among the most promising energy conversion technologies for a broad range of applications, offering zero-emission electricity generation by converting hydrogen directly into electrical energy at high efficiencies. Tremendous advancements have been made in terms of performance and durability but technological challenges still exist which hinder their widespread adoption; these challenges range from material durability to system design and operating strategies. Developing this technology requires a comprehensive understanding of its fundamental operation, coupled with effective diagnostic techniques. Performance, temperature and hydration in a PEFC is a complex relationship governed by cause-and-effect, where a change in one factor alters the other. These problems are exacerbated during scale-up, advancing from small lab-scale single cells to large commercial automotive stacks, where operational heterogeneities encourage large current and temperature variations, resulting in varied local degradation rates and inefficient PEFC performance. This study characterises these parameters in-operando by adopting diagnostic techniques such as current, temperature and pressure mapping, coupled with electrochemical techniques, to garner a broader understanding of the formation of these heterogeneities. The development of new diagnostic techniques for both research and industry is also crucial for the commercialisation of PEFCs, as stack-level diagnostic resources are limited. These are required to be straightforward in application and interpretation, cost-effective and with short testing times. Novel diagnostic techniques are presented in this study which aim to bridge this gap in the diagnostic sector. Lock-in thermography is used to image sub-surface water content during cell operation using a thermal imaging camera, producing water distribution images at various penetration depths. A complementary transfer function technique is also developed, termed heat-stimulus thermo-electric impedance spectroscopy (HS-TEIS), which considers the complex relationship between imposed temperature change and electrical response as a function of frequency

Up in smoke: Considerations for lithium-ion batteries in disposable e-cigarettes

In recent years, the use of disposable electric (e)-cigarettes containing lithium-ion batteries in the UK has led to remarkable wastage, the full environmental impact of which is yet to be realized. This study investigates the suitability for reuse and safety aspects of cells found in disposable e-cigarettes. Through electrochemical and safety characterization techniques, the cells’ performance and hazards were evaluated. Rate capability and long-term cycling experiments showed that cells sold as disposable were capable of completing 474 cycles at 1C charge/discharge before reaching 80% capacity fade. A nail penetration test revealed significant gas expulsion and a maximum temperature of 495°C. However, the cell format prevented significant material ejection. This work outlines the potential health hazards and highlights the possibility for second-life use of disposable e-cigarette cells, shedding light on the environmental impact and safety considerations

Electrochemical recovery of lithium-ion battery materials from molten salts by microstructural characterization using X-ray imaging

Recycling spent lithium-ion batteries (LiBs) guarantees the conservation of important metal resources by reducing demands on raw supply and offsetting the energy and environmental costs associated with its manufacture. Employing a molten salt as a solvent for extraction affords a much greener and simpler route to metal recovery by electrochemical means. The current mechanistic understanding of the electrochemical recovery of metals in molten salts needs to be improved for the process to be optimized. X-ray computed tomography offers a non-destructive approach for 3D microstructure visualization and subsequent quantification. Here, we study the electrochemical deposition of recovered cobalt metal from lithium cobalt oxide, LiCoO2 in LiCl-KCl eutectic (LKE). This diagnostic approach has been applied to LiCoO2-LKE samples before and after electrolysis at 450°C, yielding key insights into the morphological evolution of product formation

Nonuniform compensation of current density distribution in polymer electrolyte fuel cells by local heating

A homogeneous current density distribution improves a fuel cell’s performance and prolongs its service life. Effective cell structure designs and uniform compression during assembly could support this goal by ensuring a homogeneous reaction rate across the activation area. Due to the coupling of hydro-electro-thermal relationships, for instance, the concentration of reactants along the flow field decreases continuously as the electrochemical reaction proceeds, and the subsequent accumulation of liquid water leads to a low current density at the outlet. The effect of operating conditions, such as local heating, on the current density distribution requires further investigation. This paper studies the impact of local heating on polymer electrolyte fuel cell (PEFC) performance and analyses the effects on voltage by mapping the current density distribution across the active area. Local heating was supplied to the three regions of the electrode, namely, fuel inlet, central and outlet regions, with the latter exhibiting the best performance (in the activation, Ohmic and mass transport controlled region, the output voltage increases compared to no local heating corresponding to 1.28%, 2.17% and 2.46%, respectively). Here, we show that in all local heating cases, outlet heating can compensate for the lowest current density region with the largest current density increased by 91.10 mA cm−2 and achieves a more homogeneous current distribution, while inlet heating aggravates heterogeneity. This study provides practical guidance for optimal thermal management system development whereby the cooling channel design should be locally optimised for more uniform distributions of current density and temperature compared to heating the cell uniformly

Nonuniform compensation of current density distribution in polymer electrolyte fuel cells by local heating

A homogeneous current density distribution improves a fuel cell's performance and prolongs its service life. Effective cell structure designs and uniform compression during assembly could support this goal by ensuring a homogeneous reaction rate across the activation area. Due to the coupling of hydro-electro-thermal relationships, for instance, the concentration of reactants along the flow field decreases continuously as the electrochemical reaction proceeds, and the subsequent accumulation of liquid water leads to a low current density at the outlet. The effect of operating conditions, such as local heating, on the current density distribution requires further investigation. This paper studies the impact of local heating on polymer electrolyte fuel cell (PEFC) performance and analyses the effects on voltage by mapping the current density distribution across the active area. Local heating was supplied to the three regions of the electrode, namely, fuel inlet, central and outlet regions, with the latter exhibiting the best performance (in the activation, Ohmic and mass transport controlled region, the output voltage increases compared to no local heating corresponding to 1.28%, 2.17% and 2.46%, respectively). Here, we show that in all local heating cases, outlet heating can compensate for the lowest current density region with the largest current density increased by 91.10 mA cm−2 and achieves a more homogeneous current distribution, while inlet heating aggravates heterogeneity. This study provides practical guidance for optimal thermal management system development whereby the cooling channel design should be locally optimised for more uniform distributions of current density and temperature compared to heating the cell uniformly

Effects of an easy-to-implement water management strategy on performance and degradation of polymer electrolyte fuel cells

Intermittent switching between wet and dry reactant gases during operation in a polymer electrolyte fuel cell (PEFC) can improve performance stability, alleviating the effects of flooding by controlling the water content within the system. However, lifetime durability may be affected due to membrane electrode assembly (MEA) boundary delamination and membrane damage. Two relative humidity (RH) control strategies were investigated, using electrochemical performance and MEA degradation as critical indicators. It was found that intermittent switching between wet and dry gases does not accelerate fuel cell degradation if the duration of the dry gas period is set reasonably (dry gases stops before the voltage reaches the apex of the hump). Additionally, current and temperature distribution mapping was utilised to capture the dynamic response between these transitional stages. The switching of dry gases first makes the current density distribution homogeneous, and the maximum current density is reduced subsequently. Then, the current density near the inlet keeps decreasing. Intermittent switching between wet and dry reactant gases is easy to implement and overcomes limitations in mass transfer at medium and high current densities

Cardiovascular risk status of Afro-origin populations across the spectrum of economic development: findings from the Modeling the Epidemiologic Transition Study

Background: Cardiovascular risk factors are increasing in most developing countries. To date, however, very little standardized data has been collected on the primary risk factors across the spectrum of economic development. Data are particularly sparse from Africa. Methods: In the Modeling the Epidemiologic Transition Study (METS) we examined population-based samples of men and women, ages 25–45 of African ancestry in metropolitan Chicago, Kingston, Jamaica, rural Ghana, Cape Town, South Africa, and the Seychelles. Key measures of cardiovascular disease risk are described. Results: The risk factor profile varied widely in both total summary estimates of cardiovascular risk and in the magnitude of component factors. Hypertension ranged from 7% in women from Ghana to 35% in US men. Total cholesterol was well under 200 mg/dl for all groups, with a mean of 155 mg/dl among men in Ghana, South Africa and Jamaica. Among women total cholesterol values varied relatively little by country, following between 160 and 178 mg/dl for all 5 groups. Levels of HDL-C were virtually identical in men and women from all study sites. Obesity ranged from 64% among women in the US to 2% among Ghanaian men, with a roughly corresponding trend in diabetes. Based on the Framingham risk score a clear trend toward higher total risk in association with socioeconomic development was observed among men, while among women there was considerable overlap, with the US participants having only a modestly higher risk score. Conclusions: These data provide a comprehensive estimate of cardiovascular risk across a range of countries at differing stages of social and economic development and demonstrate the heterogeneity in the character and degree of emerging cardiovascular risk. Severe hypercholesterolemia, as characteristic in the US and much of Western Europe at the onset of the coronary epidemic, is unlikely to be a feature of the cardiovascular risk profile in these countries in the foreseeable future, suggesting that stroke may remain the dominant cardiovascular event

Functional balance and gait characteristics in men with lower urinary tract symptoms secondary to benign prostatic hyperplasia

Objectives. To compare gait characteristics and functional balance abilities in men with LUTS secondary to BPH to those of matching controls under different conditions of increasing difficulties; single-task, dual-task motor, and dual-task cognitive. Subjects and methods. In this cross-sectional experimental study we recruited a group of 43 men diagnosed with symptomatic BPH and control group of 38 older men. Participants performed the timed up and go (TUG) and 10-meter walking tests under different conditions of increasing difficulties. Namely, single task, dual-task motor, and dual-task cognitive. Time to complete the tests and spatial and temporal gait parameters were compared between groups and conditions via mixed-design ANOVA. Results. Under dual-task conditions, individuals in both groups performed significantly worse in a functional balance task and a simple walking to usual walking. However, as the complexity of the walking task increased, from dual-task motor to dual-task cognitive, significant differences between groups emerged. In particular, men with PBH performed worse than older adults in tasks demanding increased attentional control. Conclusion. Health care providers for men with LUTS due to BPH should assess for abnormal gait and maintain vigilant for balance problems that may lead to decreased mobility and falls. Dual task approach seems a feasible method to distinguish gait and balance impairments in men with BPH

Effect of remote ischaemic conditioning on clinical outcomes in patients with acute myocardial infarction (CONDI-2/ERIC-PPCI): a single-blind randomised controlled trial.

BACKGROUND: Remote ischaemic conditioning with transient ischaemia and reperfusion applied to the arm has been shown to reduce myocardial infarct size in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI). We investigated whether remote ischaemic conditioning could reduce the incidence of cardiac death and hospitalisation for heart failure at 12 months. METHODS: We did an international investigator-initiated, prospective, single-blind, randomised controlled trial (CONDI-2/ERIC-PPCI) at 33 centres across the UK, Denmark, Spain, and Serbia. Patients (age >18 years) with suspected STEMI and who were eligible for PPCI were randomly allocated (1:1, stratified by centre with a permuted block method) to receive standard treatment (including a sham simulated remote ischaemic conditioning intervention at UK sites only) or remote ischaemic conditioning treatment (intermittent ischaemia and reperfusion applied to the arm through four cycles of 5-min inflation and 5-min deflation of an automated cuff device) before PPCI. Investigators responsible for data collection and outcome assessment were masked to treatment allocation. The primary combined endpoint was cardiac death or hospitalisation for heart failure at 12 months in the intention-to-treat population. This trial is registered with ClinicalTrials.gov (NCT02342522) and is completed. FINDINGS: Between Nov 6, 2013, and March 31, 2018, 5401 patients were randomly allocated to either the control group (n=2701) or the remote ischaemic conditioning group (n=2700). After exclusion of patients upon hospital arrival or loss to follow-up, 2569 patients in the control group and 2546 in the intervention group were included in the intention-to-treat analysis. At 12 months post-PPCI, the Kaplan-Meier-estimated frequencies of cardiac death or hospitalisation for heart failure (the primary endpoint) were 220 (8·6%) patients in the control group and 239 (9·4%) in the remote ischaemic conditioning group (hazard ratio 1·10 [95% CI 0·91-1·32], p=0·32 for intervention versus control). No important unexpected adverse events or side effects of remote ischaemic conditioning were observed. INTERPRETATION: Remote ischaemic conditioning does not improve clinical outcomes (cardiac death or hospitalisation for heart failure) at 12 months in patients with STEMI undergoing PPCI. FUNDING: British Heart Foundation, University College London Hospitals/University College London Biomedical Research Centre, Danish Innovation Foundation, Novo Nordisk Foundation, TrygFonden

Health and skill-related physical fitness of physiotherapy students

Physiotherapy is a physically demanding profession. Health and skill-related physical fitness should be emphasized in physiotherapy students for both the personal benefit on their own health and injury prevention and for the sustainability of their ability to meet job demands. This study aims to assess levels of health and skill-related physical fitness in undergraduate physiotherapy students in Jordan. A cross sectional study of 109 physiotherapy students; 23 males aged 19.57 (1.44) years and 86 females aged 20.02 (2.61) years. The following health and skill-related physical fitness components were assessed: body mass index (BMI), modified sit and reach, partial curl-up, push-ups, vertical jump, 20-m shuttle run, handgrip strength, 4x10 shuttle run, and star excursion balance tests. Most of the students had normal BMI (65.1%) but levels of physical fitness were mainly poor and below average except for hamstring flexibility which was excellent. Lack of normative data on agility and dynamic balance in healthy adults who are not athletes limited determining their level in our students. The results mainly demonstrated poor levels of health-related physical fitness of Jordanian physiotherapy students, which could have a significant effect on their performance and increase their risk of injury. Dynamic balance and agility results are presented for the first time in healthy adults (not athletes) which could be used in future research. It is suggested to encourage commitment towards lifestyle modification and health behaviour and increase awareness of the physical demands of the profession