The Experts below are selected from a list of 4092 Experts worldwide ranked by ideXlab platform

Hossein Esmaeilzadeh - One of the best experts on this subject based on the ideXlab platform.

  • determination of optimal operating conditions for a polymer electrolyte membrane fuel cell stack optimal operating condition based on multiple criteria
    International Journal of Energy Research, 2013
    Co-Authors: Hoseyn Sayyaadi, Hossein Esmaeilzadeh
    Abstract:

    SUMMARY A methodology for optimal control of the polymer electrolyte membrane fuel cell (PEMFC) with multiple criteria is presented here. In this regard, thermoelectric objectives and thermoeconomic objective are considered, simultaneously. The proposed fuel cell is a 1200 W Ballard PEMFC namely Nexa™ power module. The net power density and exergetic efficiency of the PEMFC are maximized, and the unit cost of the generated power is minimized in a multi-objective optimization procedure using the NSGA-II (non-dominated sorting genetic algorithm). Operating temperature and pressure, air Stoichiometric Coefficient at the cathode and the current density are considered as controlling parameters in order to acquire optimal performance of the PEMFC. A set of optimal solution namely the Pareto frontier is obtained, and a final optimal solution is selected from available solutions located on the Pareto frontier using the fuzzy decision-making process based on the Bellman–Zadeh approach. Results are compared with corresponding results obtained previously in single objective optimization scenarios. It has been shown that the optimal operating condition obtained based on the multiple criteria approach has least deviation from the ideal features of the fuel cell in comparison to the corresponding optimal solution obtained in conventional single-objective optimization approaches. Copyright © 2013 John Wiley & Sons, Ltd.

  • determination of optimal operating conditions for a polymer electrolyte membrane fuel cell stack optimal operating condition based on multiple criteria
    International Journal of Energy Research, 2013
    Co-Authors: Hoseyn Sayyaadi, Hossein Esmaeilzadeh
    Abstract:

    SUMMARY A methodology for optimal control of the polymer electrolyte membrane fuel cell (PEMFC) with multiple criteria is presented here. In this regard, thermoelectric objectives and thermoeconomic objective are considered, simultaneously. The proposed fuel cell is a 1200 W Ballard PEMFC namely Nexa™ power module. The net power density and exergetic efficiency of the PEMFC are maximized, and the unit cost of the generated power is minimized in a multi-objective optimization procedure using the NSGA-II (non-dominated sorting genetic algorithm). Operating temperature and pressure, air Stoichiometric Coefficient at the cathode and the current density are considered as controlling parameters in order to acquire optimal performance of the PEMFC. A set of optimal solution namely the Pareto frontier is obtained, and a final optimal solution is selected from available solutions located on the Pareto frontier using the fuzzy decision-making process based on the Bellman–Zadeh approach. Results are compared with corresponding results obtained previously in single objective optimization scenarios. It has been shown that the optimal operating condition obtained based on the multiple criteria approach has least deviation from the ideal features of the fuel cell in comparison to the corresponding optimal solution obtained in conventional single-objective optimization approaches. Copyright © 2013 John Wiley & Sons, Ltd.

Hoseyn Sayyaadi - One of the best experts on this subject based on the ideXlab platform.

  • determination of optimal operating conditions for a polymer electrolyte membrane fuel cell stack optimal operating condition based on multiple criteria
    International Journal of Energy Research, 2013
    Co-Authors: Hoseyn Sayyaadi, Hossein Esmaeilzadeh
    Abstract:

    SUMMARY A methodology for optimal control of the polymer electrolyte membrane fuel cell (PEMFC) with multiple criteria is presented here. In this regard, thermoelectric objectives and thermoeconomic objective are considered, simultaneously. The proposed fuel cell is a 1200 W Ballard PEMFC namely Nexa™ power module. The net power density and exergetic efficiency of the PEMFC are maximized, and the unit cost of the generated power is minimized in a multi-objective optimization procedure using the NSGA-II (non-dominated sorting genetic algorithm). Operating temperature and pressure, air Stoichiometric Coefficient at the cathode and the current density are considered as controlling parameters in order to acquire optimal performance of the PEMFC. A set of optimal solution namely the Pareto frontier is obtained, and a final optimal solution is selected from available solutions located on the Pareto frontier using the fuzzy decision-making process based on the Bellman–Zadeh approach. Results are compared with corresponding results obtained previously in single objective optimization scenarios. It has been shown that the optimal operating condition obtained based on the multiple criteria approach has least deviation from the ideal features of the fuel cell in comparison to the corresponding optimal solution obtained in conventional single-objective optimization approaches. Copyright © 2013 John Wiley & Sons, Ltd.

  • determination of optimal operating conditions for a polymer electrolyte membrane fuel cell stack optimal operating condition based on multiple criteria
    International Journal of Energy Research, 2013
    Co-Authors: Hoseyn Sayyaadi, Hossein Esmaeilzadeh
    Abstract:

    SUMMARY A methodology for optimal control of the polymer electrolyte membrane fuel cell (PEMFC) with multiple criteria is presented here. In this regard, thermoelectric objectives and thermoeconomic objective are considered, simultaneously. The proposed fuel cell is a 1200 W Ballard PEMFC namely Nexa™ power module. The net power density and exergetic efficiency of the PEMFC are maximized, and the unit cost of the generated power is minimized in a multi-objective optimization procedure using the NSGA-II (non-dominated sorting genetic algorithm). Operating temperature and pressure, air Stoichiometric Coefficient at the cathode and the current density are considered as controlling parameters in order to acquire optimal performance of the PEMFC. A set of optimal solution namely the Pareto frontier is obtained, and a final optimal solution is selected from available solutions located on the Pareto frontier using the fuzzy decision-making process based on the Bellman–Zadeh approach. Results are compared with corresponding results obtained previously in single objective optimization scenarios. It has been shown that the optimal operating condition obtained based on the multiple criteria approach has least deviation from the ideal features of the fuel cell in comparison to the corresponding optimal solution obtained in conventional single-objective optimization approaches. Copyright © 2013 John Wiley & Sons, Ltd.

G A Ekama - One of the best experts on this subject based on the ideXlab platform.

  • anoxic growth of phosphate accumulating organisms paos in biological nutrient removal activated sludge systems
    Water Research, 2002
    Co-Authors: M C Wentzel, G A Ekama
    Abstract:

    In this paper, research on the growth performance of phosphate-accumulating organisms (PAOs) was conducted based on literature and experimental investigations on biological nutrient removal (BNR) activated sludge (BNRAS) systems. The research aims at presenting the occurrence of denitrifying PAOs (DPAOs), abstracting information on the kinetics and stoichiometry of PAOs under anoxic conditions and determining the conditions that stimulate the PAO growth under anoxic conditions. The research results indicate that the PAOs are capable of utilizing nitrate as electron acceptor instead of oxygen in BNRAS systems, particularly in external nitrification BNRAS (ENBNRAS) systems. However, the growth yield of PAOs under anoxic conditions should be reduced to about 70% of that under aerobic conditions, and further the Stoichiometric Coefficient for anoxic P uptake per PHB COD utilized should be reduced to about 80% of that under aerobic conditions as the DPAOs show a significantly lower BEPR performance and use the influent RBCOD less "efficiently" compared with aerobic PAOs (APAOs). The research results also indicate that the major factor influencing the occurrence of DPAOs and associated anoxic P uptake is the nitrate load into the anoxic reactor, i.e. the nitrate load should be large enough or exceeds the denitrification potential of ordinary heterotrophic organisms (OHOs), i.e. non-PAO organisms in the anoxic reactor to stimulate DPAOs in the system as the specific denitrification rate of OHOs (K'2 OHO) is significantly larger than that of PAOs (K'2 PAO). In terms of this competition, if the nitrate load into the main anoxic reactor is less than the denitrification potential of OHOs, then the OHOs will outcompete PAOs for using the limited nitrate, while if the nitrate load in the main anoxic reactor exceeds the denitrification potential of OHOs, then the PAOs would have opportunities to use the "excess" nitrate and so develop in the system. The other factors that influence DPAOs include the system aerobic mass fraction, sequence of reactors and frequency of sludge alternation between the aerobic and anoxic states. Although it does appear that these factors above may significantly influence the fraction of DPAOs (etaG), the quantitative relationship between these factors and etaG is not known, and the experimental observations indicate that this will be system-specific, and require calibration for each situation.

  • anoxic growth of phosphate accumulating organisms paos in biological nutrient removal activated sludge systems
    Water Research, 2002
    Co-Authors: M C Wentzel, G A Ekama
    Abstract:

    In this paper, research on the growth performance of phosphate-accumulating organisms (PAOs) was conducted based on literature and experimental investigations on biological nutrient removal (BNR) activated sludge (BNRAS) systems. The research aims at presenting the occurrence of denitrifying PAOs (DPAOs), abstracting information on the kinetics and stoichiometry of PAOs under anoxic conditions and determining the conditions that stimulate the PAO growth under anoxic conditions. The research results indicate that the PAOs are capable of utilizing nitrate as electron acceptor instead of oxygen in BNRAS systems, particularly in external nitrification BNRAS (ENBNRAS) systems. However, the growth yield of PAOs under anoxic conditions should be reduced to about 70% of that under aerobic conditions, and further the Stoichiometric Coefficient for anoxic P uptake per PHB COD utilized should be reduced to about 80% of that under aerobic conditions as the DPAOs show a significantly lower BEPR performance and use the influent RBCOD less ‘‘efficiently’’ compared with aerobic PAOs (APAOs). The research results also indicate that the major factor influencing the occurrence of DPAOs and associated anoxic P uptake is the nitrate load into the anoxic reactor, i.e. the nitrate load should be large enough or exceeds the denitrification potential of ordinary heterotrophic organisms (OHOs), i.e. non-PAO organisms in the anoxic reactor to stimulate DPAOs in the system as the specific denitrification rate of OHOs (K 0 2 OHO) is significantly larger than that of PAOs (K 0 2 PAO). In terms of this competition, if the nitrate load into the main anoxic reactor is less than the denitrification potential of OHOs, then the OHOs will outcompete PAOs for using the limited nitrate, while if the nitrate load in the main anoxic reactor exceeds the denitrification potential of OHOs, then the PAOs would have opportunities to use the ‘‘excess’’ nitrate and so develop in the system. The other factors that influence DPAOs include the system aerobic mass fraction, sequence of reactors and frequency of sludge alternation between the aerobic and anoxic states. Although it does appear that these factors above may significantly influence the fraction of DPAOs (Z G ), the quantitative relationship between these factors and ZG is not known, and the experimental observations indicate that this will be system-specific, and require calibration for each situation. r 2002 Elsevier Science Ltd. All rights reserved.

M C Wentzel - One of the best experts on this subject based on the ideXlab platform.

  • anoxic growth of phosphate accumulating organisms paos in biological nutrient removal activated sludge systems
    Water Research, 2002
    Co-Authors: M C Wentzel, G A Ekama
    Abstract:

    In this paper, research on the growth performance of phosphate-accumulating organisms (PAOs) was conducted based on literature and experimental investigations on biological nutrient removal (BNR) activated sludge (BNRAS) systems. The research aims at presenting the occurrence of denitrifying PAOs (DPAOs), abstracting information on the kinetics and stoichiometry of PAOs under anoxic conditions and determining the conditions that stimulate the PAO growth under anoxic conditions. The research results indicate that the PAOs are capable of utilizing nitrate as electron acceptor instead of oxygen in BNRAS systems, particularly in external nitrification BNRAS (ENBNRAS) systems. However, the growth yield of PAOs under anoxic conditions should be reduced to about 70% of that under aerobic conditions, and further the Stoichiometric Coefficient for anoxic P uptake per PHB COD utilized should be reduced to about 80% of that under aerobic conditions as the DPAOs show a significantly lower BEPR performance and use the influent RBCOD less "efficiently" compared with aerobic PAOs (APAOs). The research results also indicate that the major factor influencing the occurrence of DPAOs and associated anoxic P uptake is the nitrate load into the anoxic reactor, i.e. the nitrate load should be large enough or exceeds the denitrification potential of ordinary heterotrophic organisms (OHOs), i.e. non-PAO organisms in the anoxic reactor to stimulate DPAOs in the system as the specific denitrification rate of OHOs (K'2 OHO) is significantly larger than that of PAOs (K'2 PAO). In terms of this competition, if the nitrate load into the main anoxic reactor is less than the denitrification potential of OHOs, then the OHOs will outcompete PAOs for using the limited nitrate, while if the nitrate load in the main anoxic reactor exceeds the denitrification potential of OHOs, then the PAOs would have opportunities to use the "excess" nitrate and so develop in the system. The other factors that influence DPAOs include the system aerobic mass fraction, sequence of reactors and frequency of sludge alternation between the aerobic and anoxic states. Although it does appear that these factors above may significantly influence the fraction of DPAOs (etaG), the quantitative relationship between these factors and etaG is not known, and the experimental observations indicate that this will be system-specific, and require calibration for each situation.

  • anoxic growth of phosphate accumulating organisms paos in biological nutrient removal activated sludge systems
    Water Research, 2002
    Co-Authors: M C Wentzel, G A Ekama
    Abstract:

    In this paper, research on the growth performance of phosphate-accumulating organisms (PAOs) was conducted based on literature and experimental investigations on biological nutrient removal (BNR) activated sludge (BNRAS) systems. The research aims at presenting the occurrence of denitrifying PAOs (DPAOs), abstracting information on the kinetics and stoichiometry of PAOs under anoxic conditions and determining the conditions that stimulate the PAO growth under anoxic conditions. The research results indicate that the PAOs are capable of utilizing nitrate as electron acceptor instead of oxygen in BNRAS systems, particularly in external nitrification BNRAS (ENBNRAS) systems. However, the growth yield of PAOs under anoxic conditions should be reduced to about 70% of that under aerobic conditions, and further the Stoichiometric Coefficient for anoxic P uptake per PHB COD utilized should be reduced to about 80% of that under aerobic conditions as the DPAOs show a significantly lower BEPR performance and use the influent RBCOD less ‘‘efficiently’’ compared with aerobic PAOs (APAOs). The research results also indicate that the major factor influencing the occurrence of DPAOs and associated anoxic P uptake is the nitrate load into the anoxic reactor, i.e. the nitrate load should be large enough or exceeds the denitrification potential of ordinary heterotrophic organisms (OHOs), i.e. non-PAO organisms in the anoxic reactor to stimulate DPAOs in the system as the specific denitrification rate of OHOs (K 0 2 OHO) is significantly larger than that of PAOs (K 0 2 PAO). In terms of this competition, if the nitrate load into the main anoxic reactor is less than the denitrification potential of OHOs, then the OHOs will outcompete PAOs for using the limited nitrate, while if the nitrate load in the main anoxic reactor exceeds the denitrification potential of OHOs, then the PAOs would have opportunities to use the ‘‘excess’’ nitrate and so develop in the system. The other factors that influence DPAOs include the system aerobic mass fraction, sequence of reactors and frequency of sludge alternation between the aerobic and anoxic states. Although it does appear that these factors above may significantly influence the fraction of DPAOs (Z G ), the quantitative relationship between these factors and ZG is not known, and the experimental observations indicate that this will be system-specific, and require calibration for each situation. r 2002 Elsevier Science Ltd. All rights reserved.

J. Carlos Aledo - One of the best experts on this subject based on the ideXlab platform.

  • What Process Is Glycolytic Stoichiometry Optimal For
    Journal of molecular evolution, 2006
    Co-Authors: Alicia Esteban Del Valle, J. Carlos Aledo
    Abstract:

    It has been proposed that the glycolytic stoichiometry of 2 ATP per glucose is the result of an optimization that maximizes the rate of ATP production. However, using a nonequilibrium thermodynamic approach, we show here that glycolysis operates under optimal output power and not at optimal flow of ATP production. Furthermore, it can be proved that the same maximal output power can be achieved with different stoichiometries. However, changes in the glycolytic stoichiometry would dramatically affect the efficiency of all those cellular processes powered by ATP. Our results suggest that the Stoichiometric Coefficient, as found in most contemporary cells, may be the outcome of an evolutionary process leading to yield an operative quantum energy for the hydrolysis of ATP.