Dynamical modeling of water transport in polymer electrolyte membrane fuel cell (PEMFC) design

A two-dimensional finite element computational fluid dynamics (CFD) model, including coupled partial differential equations of mass, momentum and charge conservation inside a membrane electrode assembly of a polymer electrolyte membrane fuel cell (PEMFC) are developed. The CFD model is solved for PEMFCs with conventional and interdigitated gas flow fields. For the PEMFC with interdigitated flow fields both coflow and counterflow designs are studied. Furthermore a dynamic lumped model based on the formulation of Pukrushpan et al. (2003) is developed with the addition of membrane's transient water transport. Models are validated by comparing the polarization curves with the experimental data of Ticianelli et al. (1988) for MEAs with conventional gas distributors and He et al. (2000) for MEAs with counterflow interdigitated gas distributors. The results of the lumped model and the CFD model for conventional design are shown to be comparable and lumped model proves to be a good substitute of CFD model for control studies. For the interdigitated case, coflow is found to be superior to counterflow in the performance of the cell. Transient and steady-state responses of the fuel cell system to changes in cell voltage, air pressure and relative humidity of air are investigated for each design. The effect of transient water transport is emphasized and it is observed that it plays a critical role in the operation of a PEMFC for both designs

Doğrudan Metanollü Yakıt Pili (DMYP) Sistemindeki Yoğuşturucunun Hava Tarafı Termal Modellemesi

Doğrudan metanollü yakıt pilleri (DMYP) kimyasal enerjiyi elektrik enerjisine doğrudan çeviren enerji dönüşüm cihazlarıdır. DMYP’de yakıt olarak kullanılan metanolün yüksek enerji yoğunluğuna (15,9 MJ/l) sahip olması, kolay depolanabi- liyor ve taşınabiliyor olması DMYP’nin önemli bir yakıt pili türü olmasını sağlar. Buna karşın, istenmeyen metanol geçişi, reaksiyonların yavaşlığı ve düşük sistem verimliliği devam eden olumsuzluklardır. Günümüzde bu olumsuzluklara rağmen, DMYP sistemleri istif makinelerinde, hafif elektrikli araçlarda (0,5 W-5 kW) ve kü- çük taşınabilir jeneratör uygulamalarında kullanılmaktadır. Bir DMYP sisteminde yoğuşturucu, fan, pompa ve karışım kabı gibi yardımcı donanımlar bulunur. Bu- rada, yoğuşturucu yakıt pilinden çıkan atık ısının dağıtılmasını ve yakıt pili çıkış gazın içerisinde yer alan su buharını yoğuşturup sisteme geri beslenilmesini sağ- lar. Bu çalışmada DMYP sistemlerinde kullanılabilecek uygun bir yoğuşturucunun hava tarafı için bir matematiksel model oluşturulacaktır. Bu model farklı DMYP çalışma koşulları altında yoğuşturucunun hava tarafının ısı transferi performansını verecektir.Direct methanol fuel cell is an energy conversion device which converts chemi- cal energy to electrical energy directly. Having high energy density (15,9 MJ/l) of methanol used as a fuel in DMFC, easy storage and transportability provide the DMFC an important fuel cell type. However, undesirable methanol crossover, slow reaction kinetic rate, and low system efficiency are still disadvantages. Nowadays, despite these disadvantages of DMFCs, they can be used in forklift, light-weight tracks (0.5 W-5 kW) and small portable generator applications. A DMFC system in- cludes auxiliary equipment such as the condenser, blower, pump, and mixing cham- ber. Here, the condenser provides water recovery to the system condensing water vapor existed in the exhaust gas of fuel cell and dissipate waste heat formed from the DMFC. In this study, an air-side mathematical model for an available condenser in the DMFC system is formed. This model gives the air-side heat transfer perfor- mance of condenser under different DMFC working conditions

Modeling and simulation of Power-to-X systems: A review

© 2021 Elsevier LtdPower to X (P-t-X) denotes methods for converting renewable energy into liquids or gases, which can be stored, distributed or converted to valuable products. Furthermore, P-t-X can provide grid stability in connection with fluctuating electricity from renewable sources. One of the essential steps in determining the feasibility of a P-t-X system for the market is the thermodynamic, techno-economic, and environmental assessment through mathematical modeling and simulation. In this review paper, different P-t-X system configurations with their performance, environmental impact, and cost are presented. This paper only includes literature about system-level mathematical modeling and simulation studies. In this regard, an introduction to various P-t-X processes including all the stages from the power generation to the upgrading of the final product (X) is firstly presented, followed by several key system-level P-t-X studies, which consist of thermodynamic, techno-economic, and life cycle assessment analyses, published between 2015 and 2020. Finally, conclusions drawn from the previous studies and suggestions for future studies are given

A mini review on mathematical modeling of co-electrolysis at cell, stack and system levels

Co-electrolysis is a promising electrochemical process where simultaneous electrochemical reduction of steam and carbon dioxide take place to produce syngas. The co-electrolyzer based electrochemical fuel synthesis has gained considerable attention for converting renewable electricity into high value-added, easy storable and transportable fuels (e.g., methane, methanol, and ethanol) due to its environmental and thermodynamic benefits. Several experimental works have been carried out on the co-electrolyzer technology, especially on testing various cell component materials. In the last few decades, numerous mathematical modeling studies with various approaches have also been conducted to understand different phenomena (e.g., heat and mass transfer, fluid flow and electrochemical kinetics) in cell, stack, and system-level of co-electrolyzer. Existing review studies on the co-electrolyzers are limited and they lack comprehensive investigation of macro (component) and system scale modeling approaches, (rather mainly focus on the material development). Therefore, the main contribution of this paper is to present an extensive discussion and comparison of the studies that address cell, stack, and system scale mathematical modeling of co-electrolyzers. Moreover, remarkable conclusions drawn from these studies and suggestions for future directions are presented

Scaling and performance assessment of power-to-methane system based on an operation scenario

In this study, scaling and performance assessment of a power-to-methane (PtM) system based on a new operation strategy is presented. The strategy is principally based on avoidance of hydrogen storage, selection of appropriate hydrogen content of product gas (mainly consisting of CO2, H2, and CH4), and catalyst loading in the reactor. In this regard, a zero-dimensional (0-D) mathematical model is developed for the CO2 methanation fixed bed reactor and the photovoltaic (PV) panels, while the alkaline electrolyzer is described based on an available polarization curve. The model developed for the reactor is then compared with the experimental study found in the literature. Simulation environment is created for a small scale PtM system based on arbitrary CO2 supply profile and solar irradiance data for one year. Based on this data, the main system components are sized. For example, three solar PV panels with the size of 2 m2 each can be sufficient to drive a 600 kW PtM system in September, while a system with two additional solar PV panels is required to drive a 900 kW PtM system in February. The system's electrical efficiency is found between 55 and 59 % under variable operating conditions