Excess Supply Research Articles

Resource productivity and determinants of technical efficiency among cassava farmers’ in north central, Nigeria

This research analyzed resource productivity and determinants of technical efficiency among cassava farmers in North Central, Nigeria. This research employed a multi-stage sampling technique. Primary data were used based on a well-designed questionnaire. Inferential and descriptive statistics were employed for data analysis. The results of resource productivity of inputs show that cassava cuttings and fertilizer have the highest and lowest elasticities, respectively. The mean-TE (Technical Efficiency) score of 74% (0.74) indicates that an average smallholder cassava producer in the sample needs about 26% (0.26) additional inputs to get to the frontier. In the TE components, the coefficients of labour, and fertilizers are significant different from zero at 1% probability level. The coefficients of agrochemicals, land inputs are significantly different from zero at 5% probability level, while the coefficient of cassava cuttings are significant different from zero at 10% probability level. In the TIE (technical inefficiency), component the coefficients of age, credit received, members of cooperatives are significant different from zero at 1% probability level. The policy formulations should be directed towards considering technological substitutions and mechanized agriculture. Excessive labour supply, characteristics of the developing agriculture in sub-Saharan Africa, could be pushed into the secondary sector of the Nigerian economy such as the cassava processing industry, therefore generating income, employment and maintaining Nigeria in the first (1st) position in the world ranking in term of cassava output. Also, it is recommended that improved cuttings, agrochemicals, and fertilizers should be made available to cassava farmers at appropriate time to increase productivity. Furthermore, credit should be made available to cassava farmers at a single digit interest rate, devoid of cumbersome administrative procedures. Keywords: Resource productivity, technical efficiency, cassava farmers, stochastic frontier model, Nigeria

Benzodiazepine Utilization in Ischemic Stroke Survivors: Analyzing Initial Excess Supply and Longitudinal Trends.

Benzodiazepines are commonly prescribed for post-acute ischemic stroke for anxiety, insomnia, and agitation. While guidelines discourage use in those aged ≥65 years, little is known about prescription patterns at the national level. We analyzed a 20% sample of US Medicare claims from April 1, 2013, to September 30, 2021. We selected beneficiaries aged ≥65 years discharged alive following an acute ischemic stroke who had traditional Medicare coverage and 6 months' prior enrollment in Parts A (hospital insurance), B (Medical insurance), and D (drug coverage). We excluded those with prior benzodiazepine prescriptions, self-discharges, or discharge to skilled nursing facilities. We examined demographics, comorbidities, first prescription days' supply, cumulative incidences of benzodiazepine first prescription fills within 90 days after discharge, and geographic and yearly trends. We included 126 050 beneficiaries with a mean age of 78 years (SD, 8); 54% were female and 82% were White. Within 90 days, 6127 (4.9%) initiated a benzodiazepine. Among new prescriptions, lorazepam (40%) and alprazolam (33%) were the most prescribed. Most (76%) of first fills had a day's supply over 7 days and 55% between 15 and 30 days. Female initiation rates were higher (5.5% [95% CI, 5.3-5.7]) than male initiation rates (3.8% [95% CI, 3.6%-3.9%]). Rates were highest in the southeast (5.1% [95% CI, 4.8%-5.3%]) and lowest in the midwest (4.0% [95% CI, 3.8%-4.3%]), with a modest nationwide initiation decline from 2013 to 2021 (cumulative incidence difference, 1.6%). Despite a gradual decline in benzodiazepine initiation from 2013 to 2021, we noted excessive supplies in prescriptions post-acute ischemic stroke discharge, underscoring the need for improved policies.

The impact of all-inclusive offerings in a tourism destination’s competitiveness

This study analyzes the impact of all-inclusive offerings on a destination's competitiveness. When the rise in all-inclusive offerings causes a negative externality on complementary services, it creates a market-size effect. This results in an excessive supply of all-inclusive offerings in the market. Imposing different taxes on all-inclusive and non-all-inclusive offerings is more effective than a cap on the supply of all-inclusive offerings. Taxes can implement the optimal allocation. We expect the market-size effect to be harmful to competitiveness in mature destinations.

Application of Fuzzy Mamdani Method to Predict the Number of Blood Bags Based on Demand and Supply Data Using Matlab

Fuzzy logic is a control system technique in solving problems and is applied to systems, from basic systems to difficult or complex systems. Fuzzy logic is the proper method to plan an input space into an output space using MATLAB's mathematical theory of fuzzy sets. The reason for using fuzzy logic is because it is related to uncertainty. The unstable demand for blood bags in hospitals makes the supply of blood bags excessive or lacking from demand. The lack of blood supply results in the unfulfilled demand for blood needed by the hospital, while the excess blood supply worsens the quality of blood. In this study, we will predict the number of bags produced using the Mamdani Fuzzy Inference System (FIS) method based on the minimum demand and maximum demand values and the minimum supply and maximum supply that produce output from the defuzzification process. Applying the Mamdani Fuzzy Inference System (FIS) method based on demand and supply data obtains optimal output with MATLAB in predicting the number of blood bags produced. The results of the study showed that the Mean Absolute Percentage Error (MAPE) fuzzy logic Mamdani error value was 24%, the accuracy value of the Fuzzy Inference System (FIS) Mamdani in determining the number of blood bag production was 76%, and the production output generated through the Fuzzy Inference System (FIS) Mamdani was 4,774 blood bags. The number of blood requests at the hospital is 4,443 blood bags, so the amount of blood that must be produced to meet the hospital's demand is 4,774 bags.

Excess supply of sulfur mitigates thallium toxicity to rice (Oryza sativa L.) growth in hydroponic experiment

Sulfur (S) is an essential element for the growth of rice plants (Oryza sativa L.), crucial for enhancing crop yield and grain quality. However, its potential in mitigating thallium (Tl) toxicity in rice remains unclear. In this study, a hydroponic experiment was performed to investigate the effects of low, medium and high S application levels (LS, MS, HS) on Tl accumulation in rice at three Tl exposure levels (0, 0.5 and 1 mg·L−1). Our findings reveal that the exogenous S application could alleviate Tl toxicity, enhancing fresh weight and shoot length of rice plant. Additionally, HS (HS, SO42− content was 387.84 mg·L−1) group significantly increased chlorophyll and glutathione (GSH) content by 6.46 to 21.38 % and 2.15 to 7.31 % respectively, while reducing malondialdehyde (MDA) levels by 17.43 to 28.48 %, compared to MS (MS, SO42− content was 193.41 mg·L−1) group. Fe content in rice roots and iron plaque consistently increased with S provision under Tl-free and Tl-contaminated conditions. In Tl exposure environment, HS and LS (LS, SO42− content was 1.02 mg·L−1) groups exhibited significant differences in Fe contents and iron plaque in rice root. Moreover, in Tl exposure environment, S application reduced Tl concentration in iron plaque, root, and shoot, HS treatment showed Tl content reduction from 16.29 % to 25.89 %, compared to LS treatment. Our findings underscore the potential of S application in hydroponic environment to promote rice growth and mitigate Tl accumulation, offering insights for developing effective Tl remediation strategies by using S-contained fertilizers.

Keterkaitan pangan dan politik-ekonomi global

Background: Global food needs will continue to increase, this cannot be separated from the increase in population which has implications for the increase in food needs which until now the world's population has increased. The availability and unavailability of food are related to the relationship between supply and demand in a global context. Findings: The hegemony of food power is not absolutely influenced by food barn countries but global food politics that enter the food chain are one of the developing issues. The control that occurs is not only in the harvesting process but also the process from planting, maintenance, to post-harvest and processing. Therefore, each country has its own unique position even though it does not have a large food barn but is still able to control global food. Methods: This study uses a descriptive qualitative method with a primary and secondary database through data collection techniques using interview techniques. Conclusion: Factors that influence food politics and dynamics have a long chain, not only farmers and buyers but there are indirect agents who add to the food process chain. Global policy intervention through institutions is carried out directly on agricultural policies and in general development policies that overall encourage global market agriculture. Support for local agricultural development subsidies and building proxy policies for small farmers when there is a surplus or deficit in supply during exports or imports.

Comprehensive review of energy management strategies: Considering battery energy storage system and renewable energy sources

AbstractThe transformation of power system networks is slowly taking shape, the advent of interruptive technological platforms dealing with digitalization and real‐time trading of power has gained attention based on incorporation of more renewables into the grid. The stochastic nature of renewables pauses security of supply challenges and other related stability concerns, and for this reason efficient methods are investigated in this review to build an understanding of microgrid energy management system (MG‐EMS) and distribution‐based energy management strategies aimed at transforming the conventional grid network into smart grid network. In essence, propagating a technological shift to microgrids which have proven to be ideal distribution networks for residential and commercial loads, have become indispensable in handling distributed energy resources (DER), such as solar, PV, wind, battery energy storage systems (BESS) and small‐scale microgrids, for example in case of excess supply, energy storage system (ESS) has been formulated as a solution to curb excess supply and can offer ancillary services to the grid network. Within the perspective of electricity generation and distribution, microgrid control methodologies, distribution network (DN) management approaches and incumbent optimization strategies used to coordinate and manage grid‐level uncertainties are investigated. In addition, this study proposes distributionally robust optimization (DRO), to manage and mitigate risks associated to shortage or oversupply of power from RESs.

Evaluation of Public Transportation System through Social Network Analysis Approach

In response to the phenomenon of global warming, the transportation sector aims to mitigate carbon emissions by promoting the use of public transportation. This study employs social network analysis to propose effective improvements to the public transportation system, focusing on bus stop locations and route networks in Hwaseong City, South Korea. Two networks were constructed based on existing public transportation routes and usage data at each bus stop. The findings and implications are as follows: Analyzing the public transportation network from a network perspective can effectively contribute to improving the public transportation network route system. By evaluating centrality and brokerage for the existing routes, it is possible to identify inefficient routes and develop efficient route modification plans. Based on actual usage patterns, excessive bus supply and unnecessary bus stop locations can be identified, allowing for the establishment of appropriate operational plans. This can lead to improved operational efficiency and cost savings. Rational route design and operational planning can enhance public transportation services and promote increased use of public transportation. Ultimately, this contributes to sustainable development through carbon reduction in the transportation sector.

Outward Foreign Direct Investment and Supply Chain Concentration: Evidence from China

The potential risks arising from excessive supply chain concentration have received more and more attention. In practice, high supply chain concentration hinders firms’ sustainable development, especially for firms in emerging markets. However, how to reduce supply chain concentration remains an underexplored problem. Outward foreign direct investment (OFDI) has been an important strategy for firms to reallocate and optimize their supply chain relationships. Thus, we tried to explore whether OFDI can serve as an effective method to reduce supply chain concentration by analyzing their relationship. Using the data of Chinese A-share listed firms from 2008 to 2022, this paper empirically examines the impact of OFDI on supply chain concentration through a two-way fixed-effects model. We find that OFDI significantly reduces supply chain concentration, and this conclusion still holds after using alternative measures of the independent variable and dependent variable, endogeneity treatment, the Heckman two-stage model test, controlling for provincial factors, and excluding special samples. Channel analysis reveals that OFDI reduces supply chain concentration mainly through increasing market share, enhancing innovation capacity, and improving reputation. Cross-sectional analysis shows that the negative effect of OFDI on supply chain concentration is more pronounced in state-owned firms, firms under high industry competition, and high-tech firms. Our findings have important implications for firms to build sustainable supply chain relationships and strengthen supply chain resilience, and for policymakers to guide OFDI reasonably. Future research could further explore the effect of firms’ investment decisions on supply chain configuration.

Hydrogen energy storage system integrated with the surplus energy from Hydropower plant in the context of Nepal: A parametric study

Abstract With the search for emission-free energy sources, hydrogen is considered a reliable alternative to store energy from renewable sources like wind, solar, thermal, and hydropower. Hydrogen has minimal environmental implications and can be stored and transported whenever there is an energy demand that other intermittent sources cannot suffice. This project aims to study the integration of hydropower with a hydrogen production and storage plant in Nepal to utilize excess energy supply that will exceed the country’s demand shortly. The excess power from the hydropower will be used to produce hydrogen from the water coming out from the tailrace. This water will also be a coolant for cooling the hydrogen before passing to the storage unit. This parametric analysis shows the effect of variation in the hydrogen inlet pressure before it enters the compressor unit and the impact of variation in storage tank pressure on the energy and exergy efficiency of the overall hydrogen production and storage system. In the first case, the inlet pressure varies from 0 to 20 MPa at three different constant storage pressures 40 MPa, 60 MPa, and 90 MPa. An increase in inlet pressure gradually increases energy and exergy efficiencies, but an increase in storage pressure lowers this efficiency. The reduction is more significant at a high value of inlet pressure. In the second case, the storage pressure varies between 20-80 MPa with constant inlet pressure at 0.1 MPa, 1 MPa, and 5 MPa. The increase in storage pressure gradually reduces efficiency, whereas the higher inlet pressure has higher efficiency. Hydrogen fills the gap between supply and demand of energy, so considering hydrogen production with multiple-stage compression and integration of three sources of energy: wind, solar, and hydropower has an excellent prospect for consistent and low carbon emission solutions.

A Fault Recovery Method for Distribution Networks With Distributed Power Sources Based on 5G Smart Terminal

Firstly, a smart terminal is designed based on 5G communication technology, which is embedded with various protection measurement devices to form a 5G smart terminal. A distributed control model for the distribution network is constructed based on 5G smart terminals, and an objective function is designed taking into account factors such as restoring important loads, surplus power supply in the distribution network, network losses, and the number of switch actions. Finally, the Sparrow Search Algorithm (SSA) is improved using elite reverse learning strategy and dynamic sine perturbation strategy, and it is used to solve the objective function. Based on the IEEE33 distribution network node system, experimental tests are conducted, and the results show that the average delay of 5G smart terminals is about 30ms. Taking 14:00 as an example, the proposed method achieves network loss, number of switch actions, recovered important load power, and power supply surplus of 46.39 kW, 3 times, 185.65 kW, 240.28 kW, respectively. The fault recovery effect of the distribution network is ideal.

Demand and Supply Drivers of Medicare and Non-Medicare Health Spending: An Analysis of U.S. States, 1991-2019.

For the last four decades, policymakers have attempted to control the United States's high health care costs by reducing patients' demand for care (e.g., by imposing managed-care restrictions or high costs on patients at the time of use). Yet studies based mostly on data from the public Medicare program, which covers mostly elderly Americans, suggest that supply (e.g., number of physicians or hospital beds) rather than demand drives aggregate service use and, hence, costs. Using variation between U.S. states in per enrollee Medicare spending versus per capita spending of all other (non-Medicare) individuals, we find that greater supply boosts costs for the entire population. Furthermore, we find that factors that suppress demand in the non-Medicare population do reduce non-Medicare health care spending, but simultaneously increase Medicare spending. This suggests that for a given supply of medical resources, suppressing demand for one group of patients may produce a compensatory increase in provision of care to those whose demand has not been suppressed. Health planning to assure adequate medical resources where they are needed while preventing excess supply where it is duplicative and wasteful is likely a more effective cost control strategy than the imposition of managed-care restrictions or imposing higher costs onto patients seeking care.

Smart nutrient management Nutrient Expert® enhances rice productivity through adjusting source-sink relationships during grain filling

Smart nutrient management optimises chemical fertiliser application while maintaining crop yields. Nutrient Expert® (NE) is a user-friendly smart nutrient management system designed to improve the productivity of smallholder farmers. However, the physiological mechanisms underlying the effects of nutrient management have yet to be fully understood. We analysed data from field experiments conducted in South and Northeast China to explore the effects of different nitrogen (N) fertiliser inputs and nutrient management systems on panicle weight and post-flowering source-sink relationships in various cropping seasons of rice. Treatments included NE recommendation, local farmers’ practices (FP), soil test based fertiliser recommendation (ST), and four N rate treatments with plus or minus 25 % and plus or minus 50 % of NE. Our analysis indicated that rice panicle weight and N accumulation increased with increasing N application rate up to a recommended rate by NE in most cases, beyond which there was little further increase. Moreover, NE significantly enhanced rice panicle weight and N accumulation compared to FP and ST in the single-season rice in Northeast China. In all experiments, both in South and Northeast China, the post-flowering source-sink difference gradually increased from negative to positive values with an increase in N application rate. Too low N application rate resulted in insufficient source supply, while too high N application rate gave excessive source supply since the sink demand reached its upper limit. Compared with FP and ST, NE achieved higher source supply and sink demand in the single-season rice, and mobilised more N from source organs to sink organs. Our analysis provides evidence for positive impacts of integrated nutrient management strategies on rice source-sink relationships and offers a physiological basis for improved rice productivity of designed NE nutrient management strategies.

Global Medical Supply Inequities

The global issue of medical supply inequity exists as some countries have excess medical supplies, which leads to large amounts of medical supply waste resulting in both economical and environmental harm. However, many countries face the opposite issue and instead have a shortage of necessary, life-saving medical supplies. The duality of the issue is a harsh and widespread reality throughout the world. For example, the United States generates about 4.7 million pounds of medical waste yearly (Zygourakis et al., 2015; Thiel et al., 2020). In contrast, India, especially during the COVID-19 epidemic, faced a massive shortage of essential equipment like N-95 respirators, face shields, as well as ventilators. To reduce the worldwide inequities that arise due to the imbalance of medical supplies, Blueprints for Pangaea (B4P), a medical surplus recovery organization was founded. B4P, headquartered at the University of Michigan in Ann Arbor, redistributes unused medical supplies to places in need both locally and internationally, effectively reducing medical supply inequities one shipment at a time. This paper aims to explore the key components and global dynamics contributing to medical waste and to consider B4P as a potential model for addressing this problem.

Glutamine enhances pneumococcal growth under methionine semi-starvation by elevating intracellular pH.

Bacteria frequently encounter nutrient limitation in nature. The ability of living in this nutrient shortage environment is vital for bacteria to preserve their population and important for some pathogenic bacteria to cause infectious diseases. Usually, we study how bacteria survive after nutrient depletion, a total starvation condition when bacteria almost cease growth and try to survive. However, nutrient limitation may not always lead to total starvation. Bacterial adaptation to nutrient shortage was studied by determining bacterial growth curves, intracellular pH, intracellular amino acid contents, gene transcription, protein expression, enzyme activity, and translation and replication activities. No exogenous supply of methionine results in growth attenuation of Streptococcus pneumoniae, a human pathogen. In this paper, we refer to this inhibited growth state between ceased growth under total starvation and full-speed growth with full nutrients as semi-starvation. Similar to total starvation, methionine semi-starvation also leads to intracellular acidification. Surprisingly, it is intracellular acidification but not insufficient methionine synthesis that causes growth attenuation under methionine semi-starvation. With excessive glutamine supply in the medium, intracellular methionine level was not changed, while bacterial intracellular pH was elevated to ~ 7.6 (the optimal intracellular pH for pneumococcal growth) by glutamine deamination, and bacterial growth under semi-starvation was restored fully. Our data suggest that intracellular acidification decreases translation level and glutamine supply increases intracellular pH to restore translation level, thus restoring bacterial growth. This growth with intracellular pH adjustment by glutamine is a novel strategy we found for bacterial adaptation to nutrient shortage, which may provide new drug targets to inhibit growth of pathogenic bacteria under semi-starvation.

796 Integrating Sustainability in Surgical Practice – the Student MedAID London Way

Abstract Aim Recognizing the imperative need for sustainable healthcare education given only 2-5% of students have had exposure within their degree, Student MedAID London (SMAL) was established to promote global health awareness by redistributing excess medical supplies and fostering a platform for increasing insight into this field. Method Volunteers actively engage with local healthcare providers to secure excess medical equipment, employing a screening process to ensure responsible donations. Teaching series, such as "Learn with Med-Aid" and online seminars, delve into global health topics often overlooked in medical school curriculum. This methodology offers a unique opportunity to integrate sustainability principles into the education of future surgeons. Results Social media and seminar engagement increased by 62% respectively since establishment in 2021, attracting over 1000+ followers across social media channels. The demographic has expanded beyond London medical students to include young healthcare professionals from across the UK and the USA. Furthermore, SMAL has acquired substantial storage space for medical donations and made successful donations to Tripoli Hospital in Lebanon. Notably, 90% of seminar attendees expressed a strong desire for more events, alongside 50% reporting it increased their confidence in global health and sustainability. Conclusions As the future generation of healthcare professionals increasingly expresses a heightened interest in sustainable practice, SMAL's endeavours uniquely underscore the profound impact that sustainability can have on surgical education. By raising awareness and actively engaging in the redistribution of medical supplies, the organization sets the stage for a paradigm shift towards more environmentally conscious healthcare initiatives in surgery.

Investigation and control of an outbreak of methicillin-susceptible Staphylococcus aureus skin and soft tissue infections in a level IV NICU

Background: Neonatal intensive care units (NICU) outbreaks caused by methicillin-susceptible Staphylococcus aureus (MSSA) are less commonly reported than outbreaks caused by methicillin-resistant S. aureus. We report an unusual outbreak of MSSA skin and soft tissue infections (SSTIs) in a level IV NICU investigated by whole genome sequencing (WGS) and molecular typing. Methods: An investigation was initiated in a 56-single-bed NICU after four patients developed MSSA SSTIs in Week 1. Case-patients had positive MSSA cultures identified by clinical cultures or surveillance sampling (bilateral nares, axillae, umbilicus, and groin), and antibiotic susceptibility testing was performed. WGS and assessment of isolate relatedness through mutation event analysis and multi-locus sequence typing (MLST) was performed by the NYS DOH. Demographic and isolate characteristics were compared using Wilcoxon rank sum test, Fisher’s exact test and Pearson’s Chi-squared test, as appropriate. Results: From Week 2 to Week 32, 9 rounds of surveillance for MSSA colonization were conducted. In all, 30 case-patients had MSSA colonization and 16 infants developed infections including impetigo (n=7), pustules (n=5), staphylococcal scalded skin syndrome (SSSS, n=2), abscess (n=1), and bacteremia (n=1). All SSTI cases presented on infants’ faces, all of whom were on non-invasive respiratory support. MLST identified 4 distinct types including MLST 121 (n=12), MLST 398 (n=10), MLST 30 (n=6), and MLST 15 (n=6). Eight isolates were unrelated to other isolates. MLST 398 and MLST 30 included isolates not closely related (>9 mutation events). The 12 MLST 121 isolates were closely related (≤9 mutational events between all isolates), harbored the mupA gene, and were mupirocin-resistant (MIC>1024 ug/ml). Clinical infection and mupirocin resistance were associated with MLST 121 (Table 1). Multiple infection control measures were implemented, including increased availability of alcohol-based hand sanitizers, introducing bare-below-the-elbows practice for staff, contact precautions for case-patients, decolonization with mupirocin and chlorhexidine baths, environmental cleaning/disinfection, and removing excess equipment and supplies. No new cases of mupirocin-resistant or MLST 121 SSTIs occurred after Week 25. Conclusion: We report a MSSA outbreak associated with multiple MLST types and a predominant mupirocin-resistant strain. This report highlights the ability of molecular typing to characterize strains causing infections versus colonization and the potential loss of mupirocin as a control measure when outbreaks are caused by mupirocin-resistant strains. WGS analysis allows for increased discrimination of mutation events allowing for improved resolution of case relatedness compared to other typing methods. Successful control of this outbreak was achieved with a multitude of infection prevention and control.

Forecast Analysis of Fruit Supply Using Time-Series Method: A Study at PT Aerofood Indonesia

PT Aerofood Indonesia is an entity operating in the aviation logistics industry, specifically as a partner of the Garuda Indonesia airline. The main problem faced is the tendency to have excessive supplies of raw materials, especially in the aspect of purchasing fruit because it is susceptible to damage. This phenomenon often recurs and peaks beyond dry goods capacity limits, especially the availability of papaya fruit which often exceeds capacity by more than 50%. Therefore, this research aims to identify the optimal forecasting method for papaya fruit to overcome the problem of excessive stock. In this research, four forecasting approaches were tested, namely Trend Analysis, Single Average Exponential, Double Average Exponential, and Holt's Winter Method. Forecasting calculations were carried out using a manual approach and supported by Minitab 18 software. The research results showed that the Holt's Winter method with a multiplicative approach produced the lowest Mean Absolute Percentage Error (MAPE), namely 16%. The Holt's Winter method with a multiplicative approach has proven to be effective in producing accurate forecasts. By implementing this recommended forecasting method, it is hoped that companies can be more efficient in managing inventory and reduce the impact of losses due to excess stock.

Effect of oxidant quantity and humidification temperature on performance of PEMFC with twin inlet and twin outlet flow field

The paper presents an analysis of the performance of a Proton Exchange Membrane (PEM) fuel cell, which is equipped with a flow field design featuring dual inlets and outlets, while operating under conditions of excess stoichiometry. These experiments were conducted using a fuel cell system connected to a station that allowed for the precise adjustment of gas flow rates. During the initial phase of experimentation, various proportions of excess oxygen were systematically applied, while maintaining constant hydrogen flow rates of 80 mL/min and 100 mL/min. Particularly noteworthy, for the case of a 100 mL/min hydrogen gas flow rate and the optimized excess oxygen proportion of 150%, further experiments were undertaken to ascertain the ideal humidification conditions. The outcomes of these experiments revealed that a hydrogen gas flow rate of 100 mL/min consistently outperformed the 80 mL/min flow rate in terms of fuel cell performance. Moreover, it was observed that the introduction of excess oxygen significantly improved performance, up to a 50% oxygen proportion for the 80 mL/min hydrogen flow rate and up to a 150% proportion for the 100 mL/min hydrogen flow rate. One intriguing observation pertained to the influence of humidification. Specifically, it was found that the utilization of a humidification temperature of 100°C, or the absence of humidification altogether, resulted in notably diminished power output. In contrast, intermediate humidification temperatures of 60°C, 70°C, 80°C, and 90°C consistently yielded identical maximum power points (MPP) when combined with a 150% excess oxygen supply and a hydrogen flow rate of 100 mL/min. The twin inlet-twin outlet flow field provides a slight advantage over the conventional serpentine flow field in the overall analysis.

Oxygen excess ratio feedforward control based on ESO for PEMFC in DC off-grid hydrogen production systems

Oxygen excess ratio (OER), which is influenced by the air flow input to the cathode, is one of the important factors affecting the performance of fuel cell system. Insufficient oxygen supply will result in a sharp drop in output voltage, while an excessive supply will bring about a large parasitic power load on the air compressor, reducing the net output power of the system and operating efficiency. Both insufficient and excess oxygen supply can adversely affect the operating life of the proton exchange membrane fuel cell (PEMFC). Due to the serious nonlinear, hysteresis, uncertainty and interference in the process of OER control, this paper proposes an OER feedforward control based on extended state observer (ESO) for a PEMFC auxiliary system with the ESO to predict the total disturbance to improve the dynamic response of the system with large time delay utilizing terminal sliding mode control (TSMC). The control strategy is divided into two stages. The first stage constructs an ESO to realize real-time observation of the state variables required for the internal operation of the auxiliary machine system and the PEMFC, and yields the air compressor voltage control signal through terminal sliding mode control. In the second stage, combined with V/f control for the compressor, the transmitted air flow is adjusted, ultimately achieving the goal of changing the OER of the PEMFC and improving operating efficiency. The simulation results show that the proposed control strategy has good anti-interference capabilities, a faster response, and less overshoot. The gas flow transmission in the gas supply system is more robust, the PEMFC operation is safer, and its lifespan is extended.