Exergetic Efficiency Rate of Change and Fuel Cell Degradation

2019 ◽  
Vol 30 (1) ◽  
pp. 207-215 ◽  
Author(s):  
Mark Williams ◽  
A. Suzuki ◽  
A. Miyamoto
Keyword(s):  
Fuel Cell ◽  
Rate Of Change ◽  
Exergetic Efficiency ◽  
Efficiency Rate

scholarly journals The Use of Exergetic Efficiency Rate of Change to Evaluate Fuel Cell Performance from Various Fuels

2010 ◽  
Vol 57 (3) ◽  
pp. 120-127
Author(s):  
Mark C. WILLIAMS ◽  
Wolfgang WINKLER ◽  
Ai SUZUKI ◽  
Akira MIYAMOTO
Keyword(s):  
Fuel Cell ◽  
Rate Of Change ◽  
Cell Performance ◽  
Exergetic Efficiency ◽  
Fuel Cell Performance ◽  
Efficiency Rate

Exergetic Analysis of a Solar-Heated Fuel Cell System Fed by Methanol

2010 ◽  
Author(s):  
Nico Hotz ◽  
Ming-Tsang Lee ◽  
Costas P. Grigoropoulos ◽  
Raul Zimmerman ◽  
Gary Rosengarten ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Solar Radiation ◽  
Power Density ◽  
Cell System ◽  
Water Mixture ◽  
Exergetic Efficiency ◽  
Fuel Cell System ◽  
Solar Heat ◽  
Exergetic Analysis ◽  
Solar Powered

The present study proposes a combination of solar-powered components (two heaters, an evaporator, and a steam-reformer) with a Proton Exchange Membrane fuel cell to form a powerplant that converts methanol to electricity. The solar radiation heats up the mass flows of methanol-water mixture and air and sustains the endothermic methanol steam-reformer at a sufficient reaction temperature (typically between 220 and 300°C). In order to compare the different types of energy (thermal, chemical, and electrical), an exergetic analysis is applied to the entire system, considering only the useful part of energy that can be converted to work. The effect of the solar radiation intensity and of different operational and geometrical parameters like the total inlet flow rate of methanol-water mixture and the size of the fuel cell on the performance of the entire system is investigated. The results of the exergetic analysis prove that the proposed solar methanol fuel cell system has the potential to be operated with a high efficiency and power density by combining methanol steam-reforming and a PEM fuel cell with solar-powered heating. The chemical exergetic efficiency can be increased by a factor of around 1.6 (e.g. from 36% to 60% for the 1000 W m−2 incoming solar heat flux) by using solar radiation as a heat source instead of any other source (e.g. by burning a chemical fuel). This enhancement of effective exergetic efficiency by using solar power for heating the system amounts to even much higher values of up to above 10 for lower solar heat fluxes and very low flow rates of inlet fuel. The effective exergetic efficiency for the herein presented solar-powered system is significantly higher than any non-solar fuel cell system fed by hydrocarbon or alcoholic fuels. At the same time, an electrical power density per irradiated area of more than 986 W m−2 is obtained for a solar heat flux of 1000 W m−2. Comparable photovoltaic systems would need excessive sunlight-to-electricity efficiencies of more than 98%. Even for decreased intensities of solar radiation as low as 300 W m−2, the system achieves very satisfactory results regarding the solar power density (89.3 W m−2) and the chemical exergetic efficiency (61%). Therefore, the combination of exergy input in form of chemical fuel and solar radiation can be promising to achieve both, a high exergetic efficiency and a high power density per area irradiated by sunlight.

Enhancing the Performance Evaluation and Process Design of a Commercial-Grade Solid Oxide Fuel Cell via Exergy Concepts

2002 ◽  
Vol 124 (2) ◽  
pp. 95-104 ◽  
Author(s):  
Comas Haynes ◽  
William J. Wepfer
Keyword(s):  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Process Design ◽  
Solid Oxide ◽  
Operating Voltage ◽  
Operating Pressure ◽  
Oxide Fuel ◽  
Exergetic Efficiency ◽  
Fuel Cell Performance ◽  
Efficiency Measures

Fuel cell technology is a promising means of energy conversion. As the technology matures, process design and analysis are gaining importance. The conventional measures of fuel cell performance (i.e., gross real and voltage efficiencies) are limited indices-of- merit. Contemporary second law concepts (availability/exergy, irreversibility, exergetic efficiency) have been used to enhance fuel cell evaluation. A previously modeled solid oxide fuel cell has been analyzed using both conventional measures and the contemporary thermodynamic measures. Various cell irreversibilities were quantified, and their impact on cell inefficiency was better understood. Exergetic efficiency is more comprehensive than the conventional indices-of- performance. This parameter includes thermal irreversibilities, considers the value of effluent exergy, and has a consistent formulation. Usage of exergetic efficiency led to process design discoveries different from the trends observed in conjunction with the conventional efficiency measures. The decision variables analyzed were operating pressure, air stoichiometric number (inverse equivalence ratio), operating voltage and fuel utilization.

Basic Electrochemical Thermodynamic Studies of Fuel Cells and Fuel Cell Hybrids

2009 ◽  
Vol 6 (2) ◽  
Author(s):  
M. Williams ◽  
T. Horita ◽  
K. Yamagi ◽  
N. Sakai ◽  
H. Yokokawa
Keyword(s):  
Free Energy ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Hybrid System ◽  
Thermal Efficiency ◽  
Oxidation Reaction ◽  
Operating Temperature ◽  
Exergetic Efficiency ◽  
Standard State ◽  
Reversible Work

It is important to understand the maximum possible thermal efficiency a device is capable of obtaining and then what of this it actually achieves. In this paper it is shown that the thermal efficiency is a product of the voltage efficiency and the maximum possible thermal efficiency. One can mathematically demonstrate that for any elemental direct anodic oxidation reaction for a simple hybrid system, any fuel cell, and any operating temperature, any pressure, the maximum reversible work is equal to the free energy of reaction at the standard state. This is useful in defining an intrinsic fuel cell exergetic efficiency. An equation for thermal efficiency as a product of exergetic efficiency and maximum possible thermal efficiency is developed and presented for loosely integrated fuel cell turbine hybrids. From these simple studies alone one would conclude that the efficiency potential of fuel cells is expanded through simple fuel cell turbine hybrids.

Exergetic Analysis of Solar-Powered Hybrid Energy Conversion and Storage Scenarios for Stationary Applications

2010 ◽  
Author(s):  
Nico Hotz ◽  
Heng Pan ◽  
Costas P. Grigoropoulos ◽  
Seung H. Ko
Keyword(s):  
Fuel Cell ◽  
Solar Radiation ◽  
Energy Conversion ◽  
Electrical Energy ◽  
Pem Fuel Cell ◽  
Elevated Pressure ◽  
Direct Conversion ◽  
Solar Irradiation ◽  
Storage Device ◽  
Exergetic Efficiency

The idea of this study is to investigate possibilities to use sunlight as the main energy source to generate and store electrical energy via different methods and technologies. Several systems consisting of photovoltaics, photoelectrolytic converters and solarthermal reformers in combination with fuel cells have been investigated in terms of efficiency and costs. A simple energetic approach would not account for these different kinds of energy and their differing availabilities (radiant, thermal, chemical, and electrical energy). To consider different forms of energy and compare them in a fair manner, exergy as the useful part of energy (the part that can theoretically be completely converted to work) provides a perfect instrument for dealing with complex energy conversion systems. In this study, four different scenarios have been investigated: Scenario A describes the direct conversion of sunlight to electricity by photovoltaics. The electric power is used in a Polymer Electrolyte Membrane (PEM) electrolyzer to split water to hydrogen which is stored in a pressure tank. A PEM fuel cell converts hydrogen to electricity on demand. Scenario B deals with a photoelectrolytic cell splitting water to hydrogen by solar irradiation combined with a storage tank and a fuel cell. In Scenario C, solar radiation is converted by photovoltaic cells to electricity which is stored in different types of batteries. Scenario D combines a methanol steam reformer heated by solar power with a PEM fuel cell to generate electricity. The reformate gas mixture can be stored at elevated pressure in a gas tank. In contrast to routes A–C, scenario D has two exergy inputs: Solar radiation and chemical exergy in form of methanol as fuel. All systems are analyzed for an average day in July and February in Central California, including a storage device sufficient to store the energy for one week. Scenario D reaches an overall exergetic efficiency of more than 25% in summer at the expense of an additional exergy input in the form of methanol. The exergetic efficiency of scenario C amounts to 10–17% in summer (4–6% in winter) depending on the battery type and scenarios A and B achieve less than 10% efficiency even in summer. The systems of scenarios A and C would cost around $20k–$45k per 1 kW average electricity generation during the day in July. Scenario D leads to significantly lower costs and scenario B is the most expensive design due to the current immaturity of photoelectrolytic devices.

Sustainable 2,5-furandicarboxylic synthesis by a direct 5-hydroxymethylfurfural fuel cell based on a bifunctional PtNiSx catalyst

2020 ◽  
Vol 56 (88) ◽  
pp. 13611-13614
Author(s):  
Jialu Wang ◽  
Xian Zhang ◽  
Guozhong Wang ◽  
Yunxia Zhang ◽  
Haimin Zhang
Keyword(s):  
Fuel Cell ◽  
Electric Energy ◽  
Value Added ◽  
Chemical Energy ◽  
New Type

A new type of direct 5-hydroxymethylfurfural (HMF) oxidation fuel cell based on a bifunctional PtNiSx/CB catalyst not only transformed chemical energy into electric energy but also converted HMF into value-added 2,5-furandicarboxylic (FDCA).

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