A semi-empirical model for efficiency evaluation of a direct methanol fuel cell

Chiu, Yu-Jen; Yu, T. Leon; Chung, Ya-Chien

doi:10.1016/j.jpowsour.2011.01.084

Cited by 24 publications

(9 citation statements)

References 28 publications

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“…This phenomenon has been found in [1][2][3][4][5][6][7] so that conducting the MPPT method fosters the DMFCs to approach MEP. In this paper, perturbation-and-observation method has been applied for maximum power point tracking, which has the advantage of simple implementation and low complexity.…”

Section: Loire -mentioning

confidence: 87%

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Direct methanol fuel cell systems with tri-stage energy management and maximum power point tracking

Huang

Cheng

et al. 2013

2013 1st International Future Energy Electronics Conference (IFEEC)

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Nowadays, most of portable electronic products are widely equipped with Li-ion battery to provide the sustained energy. Besides, direct methanol fuel cells (DMFCs) are widely researched for portable applications. Above all, it is easily taken as an alternative for charging batteries. However, DMFC is highly affected by methanol crossover rate. Its efficiency is low at low power and higher as the output power increases. Combined with this characteristic and unknown crossover rate makes the tracking of the maximum efficiency point (MEP) difficult. Fortunately, the maximum power point (MPP) is close to MEP. This paper utilizes the maximum power point tracking (MPPT) algorithm to approach the MPP and thus approach MEP. Moreover, in attempt to contain the energy supply, the tri-stage energy management's (TEM's) algorithm is implemented based on power deficit or surplus. The proposed SEPIC converter and the system algorithms will be discussed, and the experiments results are given.

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Section: Loire -mentioning

confidence: 87%

“…shows the P-I curve of the fuel cell[1][2][3][4][5]. At the right side of the MPP, the power increases as the output current increases while it decreases as the output current increases at the left side of the MPP.…”

mentioning

confidence: 99%

Direct methanol fuel cell systems with tri-stage energy management and maximum power point tracking

Huang

Cheng

et al. 2013

2013 1st International Future Energy Electronics Conference (IFEEC)

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“…From a thermodynamic point of view, it is useful to relate the efficiency to the Gibbs free energy, which has also frequently been undertaken in literature [20,21]. A third possibility is to use the higher heating value or enthalpy of combustion, which can also be found in literature [16,22]. The cell voltages for 100% voltage efficiency are U LHV = 1.10 V for the lower heating value, U HHV = 1.25 V for the higher heating value and U G = 1.21 V for the Gibbs free energy.…”

Section: Experiments and Calculationsmentioning

confidence: 99%

45% Cell Efficiency in DMFCs via Process Engineering

2020

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Methanol is a convenient liquid fuel for fuel cells, but is not converted as efficiently into electrical energy as hydrogen. This is due to the slower reaction of methanol at the anode as well as to methanol permeation. When optimizing the direct methanol fuel cell (DMFC) process, methanol concentration and flow rate, current density and air flow rate must also be taken into account. A high methanol concentration facilitates dynamic operation up to high current densities, but also leads to high methanol permeation. The air flow rate must be adjusted so that the cooling effect of evaporating water is balanced by the heat produced in the cell. Therefore, a cell with low permeation must be operated at low air flow rates to achieve autothermal operation at elevated temperatures, which can in turn reduce cell performance. For each current density, there is an optimum amount of methanol feed. In this paper, we show how these effects have to be balanced using air‐flow rates calculated to ensure thermal equilibrium. It is possible to achieve electrical cell efficiencies of up to 44% in a self‐heating DMFC. Another small increase in efficiency can be achieved by using humidified air at the cathode.

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“…In [87,88], for example, a fuel cell model indicates that the operating point of the current density provides different MPP and MEP. The air motor in SS-CAES also provides a different operating point for speed [13].…”

Section: Maximum Efficiency or Power Point Of Ss-caesmentioning

confidence: 99%

Maximum Power Point Tracking of a Small-Scale Compressed Air Energy Storage System

Kokaew

Sharkh²,

Moshrefi-Torbati

2016

IEEE Trans. Ind. Electron.

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The thesis is concerned with a small-scale compressed air energy storage (SS-CAES) system. Although these systems have relatively low energy density, they offer advantages of low environmental impact and ease of maintenance.The thesis focuses on solving a number of commonly known problems related to the perturb and observe (P&O) maximum power point tracking (MPPT) system for SS-CAES, including confusion under input power fluctuation conditions and operating point dither.A test rig was designed and built to be used for validation of the theoretical work. The rig comprised an air motor driving a permanent magnet DC generator whose power output is controlled by a buck converter. A speed control system was designed and implemented using a dSPACE controller. This enabled fast convergence of MPPT.Four MPPT systems were investigated. In the first system, the air motor characteristics were used to determine the operating speed corresponding to MPP for a given pressure. This was compared to a maximum efficiency point tracking (MEPT) system. Operating at the maximum power point resulted in 1% loss of efficiency compared to operating at the maximum efficiency point. But MPPT does not require an accurate model of the system that is needed for MEPT, which also requires more sensors.The second system that was investigated uses a hybrid MPPT approach that did not require a prior knowledge system model. It used the rate of change of power output with respect to the duty cycle of the buck converter as well as the change in duty cycle to avoid confusion under input power fluctuations. It also used a fine speed step in the vicinity of the MPP and a coarse speed step when the operating point was far from the MPP. Both simulation and experimental results demonstrate the efficiency of this proposed system. The third P&O MPPT system used a fuzzy logic approach which avoided confusion and eliminated operating point dither. This system was also implemented experimentally.A speed control system improved the controllable speed-range by using a buck-boost converter instead. The last MPPT system employed a hybrid P&O and incremental inductance (INC) approach to avoid confusion and eliminate operating point dither. The simulation results validate the design.Although the focus of the work is on SS-CAES, the results are generic in nature and could be applied to MPPT of other systems such as PV and wind turbine.

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A semi-empirical model for efficiency evaluation of a direct methanol fuel cell

Cited by 24 publications

References 28 publications

Direct methanol fuel cell systems with tri-stage energy management and maximum power point tracking

Direct methanol fuel cell systems with tri-stage energy management and maximum power point tracking

45% Cell Efficiency in DMFCs via Process Engineering

Maximum Power Point Tracking of a Small-Scale Compressed Air Energy Storage System

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