Anion exchange membrane fuel cells (AEMFCs) have attracted great interest as a low-cost fuel cell technology for clean energy conversion and utilization for the future. AEMFCs have been considered ...the most promising succedaneum to proton exchange membrane fuel cells (PEMFCs) for addressing the cost issues associated with PEMFCs due to utilizing non-platinum group metals as electrocatalysts under alkaline conditions (such as Ag, Ni, and Co). Herein, we focus on a critical topic of AEMFCs—-anion-exchange polyelectrolytes (AEPs)—which are essential materials for low-cost AEMFCs. Specifically, AEPs have been used as anion-exchange membranes (AEMs) and binders (or ionomers) in AEMFCs. Years of study have allowed AEMFCs to recently achieve unprecedented progress, specifically in terms of power density and durability. These properties are comparable to or higher thanPEMFCs due to the recent development of high performance AEPs. Currently, most AEPs focused on the application of AEMs, and the importance of ionomer research has not been widely recognized. Moreover, a comprehensive review involving a systematic performance comparison of the state-of-the-art AEMs and ionomers is still lacking, making future research on AEMFCs unclear. This review systematically and comprehensively summarizes the development of AEPs and highlights the importance of cationic species and polymer backbone structures on durability with an emphasis on the importance of ionomer research. We further describe the differences between AEMs and ionomers by comparing the advantages and disadvantages of the state-of-the-art AEMs and ionomers to accurately guide future research on AEMFCs. We cover synthetic methods, degradation mechanisms, strategies to enhance performance, water transport behaviors, structure design criteria, and new challenges for AEMs and ionomers. This review is expected to expand further understanding of AEMs and ionomers and provide a future direction for designing AEMs and ionomers for future AEMFCs.
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During exhaustive ramp-incremental cycling tests, the incidence of O2 uptake (V̇o2) plateaus is low. To verify the attainment of maximum V̇o2 (V̇o2max), it is recommended that a trial at a power ...output (PO) corresponding to 110% of the ramp-derived peak (POpeak) is performed. It remains unclear whether verification trials set at this PO can be tolerated for long enough to allow attainment of V̇o2max. Eleven recreationally trained individuals performed five ramp tests of varying slope (5, 10, 15, 25, and 30 W/min), each followed, in series, by two verification trials: the first at 110% POpeak of the 25 W/min ramp and the second at 110% POpeak attained in the preceding ramp test. Exercise duration of the first verification trial was on average 81 ± 15 s (CV = 9 ± 3%) versus 162 ± 32, 121 ± 24, 103 ± 15, and 73 ± 10 s for the second verification trials at 110% of POpeak of the 5, 10, 15, and 30 W/min ramp tests, respectively (P < 0.05). Compared with the highest V̇o2 recorded during ramp tests, V̇o2 from the subsequent verification trials was not different for the 5, 10, and 15 W/min ramp tests (P > 0.05) but was lower for the 25 and 30 W/min ramp tests (P < 0.05). Verification trials at 110% POpeak of rapidly incrementing ramp tests (i.e., 25 W/min) were not sustained for long enough to allow the attainment of V̇o2max. With commonly used rapidly incrementing ramp tests engendering exhaustion within 8–12 min, verification trials less than POpeak should be preferred as they can be sustained sufficiently long to allow the attainment of V̇o2max.
Poly(aryl-co-aryl piperidinium) (c-PAP) has recently attracted wide attention in anion exchange membrane (AEM) fuel cells (AEMFCs). Here, we report poly(aryl-co-terphenyl piperidinium)-x (PDnTP-x) ...AEMs with different alkyl spacers (n = 0, 1, 2, 6, 10) in the backbone. Long alkyl chains (n = 6 or 10) improved the dimensional stability and gas tightness (H2 permeability <10 Barrer) of membranes, while short-chain-type PDnTP-x membranes displayed higher ion conductivity (>150 mS cm−1 at 80 °C). All the PDnTP-x membranes possessed excellent alkaline stability (1 M NaOH at 80 °C for 1000 h) and oxidative stability (200 h in Fenton's reagent). Short-chain-type PD0TP-x based AEMFC reached a new-record power density of 2.67 W cm−2 at 80 °C in polyaromatic AEMFCs, which is higher than that of long-chain-type cells (1.7 W cm−2). The short-chain-type PDnTP-x AEMFCs can run stably under a 0.4 A cm−2 current density for 220 h with a low voltage decay rate of ∼77 μV h−1.
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•Elucidated the effect of alkyl chain in polymer backbone on fuel cell performance.•PDnTP-x showed excellent stability (1000 h in 1 M NaOH, 200 h in Fenton reagent).•PD1TP-25-based AEMFC reached a new-record power density of 2.67 W cm−2 at 80 °C.•PD2TP-25-based AEMFC can run for 220 h with a voltage decay rate of 77 μV h−1.
This paper is concerned with model-based dynamic peak-power evaluation for LiNMC and LiFePO 4 batteries under different operating conditions. The battery test and our prior study on ...linear-parameter-varying (LPV) battery modeling are briefly introduced. The peak-power estimation method that incorporates an explicit prediction horizon and design constraints on the battery current, voltage, and SOC are elaborated, and its computational load is analyzed. The discharge and charge peak powers are quantitatively assessed under different dynamic characterization tests, in which a comparison with the conventional PNGV-HPPC method and approaches using the less accurate models is conducted. The robustness of the peak-power estimation approach against varying battery temperatures and aging levels is investigated. The methods to improve the credibility of the peak-power assessment in the context of battery degradation are explored.
Charge recombination occurring inside the tribolayer limits the further improvement of triboelectric nanogenerator (TENG) output. While the doping of ferromagnetic medium in triboelectric materials ...has been proven effective in boosting the TENG output, its working mechanism in the tribolayer remains to be investigated. Herein, the dual tribolayer synergistic effect is demonstrated as a means of suppressing surface charge recombination, thus achieving a high peak power density of TENG based on a composite film of polymer/nickel nanoparticles. A dual tribolayer model is proposed to reveal the working mechanism of the ferromagnetic medium for suppressing charge recombination in the positive and negative tribolayer. The charge recombination ratio as a standardized assessment method is defined to quantify the surface charge loss. Owing to the dual tribolayer synergistic effect, the optimal TENG exhibits a record-high peak power density of 15.2 W m-2 Hz-1 with the ultra-low charge recombination ratio of 2.1%, representing a remarkable 3100% increase in comparison to pristine TENG in the atmospheric environment. A self-powered sitting posture monitoring system is developed based on the woven structured DT-TENGs benefiting from the dual-tribolayer synergistic effect. This work demonstrates the superior behavior of TENG in generating ultra-high-power output and provides a significant guidance in materials selection.
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•The charge recombination ratio is proposed to quantify the surface charge loss.•Doped ferromagnetic NPs assists in suppressing surface charge recombination.•A synergistic effect is found for DT-TENG via ferromagnetic NPs, especially greatly suppressing charge recombination.•A record-high power density of the DT-TENG can reach 15.2 W m-2 Hz-1 by tribolayer modulation.•A self-powered sitting posture monitoring system with a woven structure DT-TENG is designed.
Accurate prediction of building energy consumption is crucial for building energy management. However, the building energy consumption is affected by many factors and shows obvious nonlinear ...characteristics in the time series, which is difficult to predict. In this work, a novel hybrid model is proposed for predicting short-term building energy consumption. In this model, the raw data is decomposed into multiple smooth datasets using complete ensemble empirical mode decomposition with adaptive noise, and the building energy consumption is predicted by the traditional extreme gradient boosting. Taking the daily energy consumption of the City of Bloomington Intake Tower as the simulation object, the results show that the mean absolute percentage error of the proposed model is 4.85%, which is much lower than that of five benchmark models. The proposed model is also applied to the prediction of other parameters related to the energy consumption of the intake tower, and shows good prediction performance. Moreover, the influences of the sliding window length and data attributes on the prediction results are also discussed.
•A novel model combines CEEMDAN and XGBoost is proposed.•Real-world case study based on 8 years’ energy consumption is presented.•The improved model has only half of prediction error of XGBoost and outperforms other four models in the case study.
The primary purpose of this study was to determine the rate of peak power (PP) loss during the countermovement jump (CMJ) and split-squat jump (SSJ) across various loads within a set of high ...repetitions. Eleven collegiate track and field athletes who had several years of resistance training experience and were trained in the two types of jumps completed the study. The participants completed a familiarization session and 2 data collection sessions. The CMJ and SSJ were completed in random order during session 1 and 2 separated by a minimum of 72 hours. Three loads using dumbbells took place in random order with each session including body weight only (BW0), body weight plus 15% (BW15) and body weight plus 30% BW(30) for the SSJ and BW(0), BW(25), and BW(50) for the CMJ. PP was determined using the PUSH 2.0 3D accelerometer worn at the waist, which was connected to an ipad app using Bluetooth. The participants completed 14 repetitions each set with 8 min rest between sets. Repetition 3 demonstrated the highest mean PP (PPmax) within the set. No significant decrease in PP was observed until repetition 6 (3.6% below PPmax) during the SSJ and repetition 8 (5.2% below PPmax) during the CMJ. These data indicate that 5 or less repetitions should be completed during the CMJ and 7 or less for the SSJ when training for PP. Using 10% reduction in PP as an effective level to train for power endurance, we recommend completing a minimum of 12 repetitions during the CMJ and a minimum of 10 repetitions for the SSJ.
It has been a pressing challenge for human beings to reduce the energy consumption of buildings and decrease carbon emission. The application of photovoltaic (PV) system in buildings is identified as ...a renewable energy and carbon reduction approach. As a kind of typical building, the gymnasium usually has a large non-occupation roof area, which shows great application potential to cover the building demand by available photovoltaic source. This paper presents the performance of a grid-connected system integrated photovoltaic, battery storage, and electric vehicles (EV) applied in gymnasium buildings. The main building demand of gymnasium buildings can be easily covered by adopting an appropriate size of PV installation and battery capacity. The load cover ratio can achieve 0.95 when PV generation equals the energy consumption of the building and the battery with 2.7 times capacity of average daily building load is equipped. The proposed charging strategy for EVs can significantly decrease the peak power of the system compared with the constant power charging method. The peak grid power of the system adopted with the proposed charging strategy can be decreased by 51.7% of the rated load power on a typical day when PV generation is 1.4 times the energy consumption of the building and the battery capacity is 66% of the average daily building load. The results of this study show a reference for the configuration and operation scheme of PV system and electric vehicles in gymnasium buildings for renewable energy development and zero-carbon activity.
The COVID-19 pandemic and the associated lockdown can be regarded as a forced social experiment, the results of which show how to use energy under specific conditions. During this period, there was a ...reduction in electricity consumption at the level of the power system, but a different specificity distinguishes the group of household users. The article aims at presenting and analysing the identified issues concerning residential electricity users based on the experience from the COVID-19 pandemic lockdown. Data from energy meters from almost 7000 flats in Warsaw’s housing estates during the lockdown in 2020 and the analogous period before the pandemic were used. The analysis showed that, on average, residential users staying practically the whole day in their flats increased their energy consumption, but without increasing their average daily peak power, smoothing the profile in the morning hours to the level reaching the peak power that had occurred in the analogous period before the lockdown. The peak power of the sections feeding the different numbers of dwellings also remained practically unchanged during the lockdown compared to the pre-pandemic period. The pressure to work and educate remotely should contribute to an increase in the digital competence of society, which may result in an increased interest in new forms of activity and cooperation based on demand-side response and prosumption mechanisms, with digital settlements for energy exchange and services.
ABSTRACTWilk, M, Krzysztofik, M, Filip, A, Zajac, A, Bogdanis, GC, and Lockie, RG. Short-term blood flow restriction increases power output and bar velocity during the bench press. J Strength Cond ...Res XX(X)000–000, 2020—This study examined the effect of blood flow restriction (BFR) with 2 different types of cuffs on peak power output (PP), mean power output (MP), peak bar velocity (PV), and mean bar velocity (MV) in the bench press exercise (BP). Fourteen healthy strength-trained male athletes (age = 27.6 ± 3.5 years; body mass = 84.1 ± 8.0 kg; height = 175.8 ± 6.7 cm; BP 1 repetition maximum RM = 138.6 ± 17.8 kg) performed 3 different testing protocols as followswithout BFR (NO-BFR), BFR with a narrow cuff (BFRNARROW), and BFR with a wide cuff (BFRWIDE) in a randomized crossover design. During all sessions, subjects performed one set of 3 repetitions of the BP exercise using 70% 1RM. Cuff pressure was set to approximately 90% full arterial occlusion pressure of the upper limb at rest. Analyses of variance showed an increase in PP (by 21%, p < 0.01; effect size ES = 1.67), MP (by 16%, p < 0.01; ES = 0.93), PV (by 22%, p < 0.01; ES = 1.79), and MV (by 21%, p < 0.01; ES = 1.36) during BFRWIDE compared with NO-BFR and a significant increase in PP (by 15%, p < 0.01; ES = 1.07), MP (by 17%, p < 0.01; ES = 0.78), PV (by 18%, p < 0.01; ES = 1.65), and MV (by 13% p < 0.01; ES = 1.00) during BFRWIDE compared with BFRNARROW. There were no significant differences in any of the variable between NO-BFR and BFRNARROW. The results of the study indicate that short-term BFR training increases power output and bar velocity during the BP exercise. However, only BFRWIDE significantly influenced bar velocity and power output, which indicates that the width of the cuff is a critical factor determining acute exercise adaptation during BFR resistance training.
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