Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

Challenges and Opportunities of Affordable Fuel Cell

for Distributed Generation

Vijay Vaishampayan1, Adithya Vangari2

iChemical Department, 2Department of Electrical

Pune University Pune, India

1 vijay. vaishampayan20 J3@gmail.com

2 adithyavangari55555@gmail.com,

Abstract-Due to the rapid increase in global energy

consumption and the diminishing of fossil fuels, the customer

demand for new generation capacities and efficient energy

production, delivery and utilization keeps rising. Utilizing

distributed generation, and energy storage can potentially solve

such problems as energy shortage and global warming.

Especially Proton Exchange Membrane (PEM). Fuel Cell and

Solid Oxide Fuel Cell (SOFC) have been considered as the top

candidate as compared to other fuel cells because of various

factor such as enhanced efficiency, negligible emission, high

reliability and simple construction. PEMFC & SOFC can be used

to bridge the gap between the rapidly increasing demand and the

unavailability of resources to sustain them. In this paper we are

focusing on cost reduction technology and the contamination

issues of Proton Exchange Membrane fuel cell and Solid Oxide

Fuel Cell.

Index Terms-Fuel cells, Proton Exchange Membrane Fuel

Cell (pEMFC), Solid Oxide Fuel Cell (SOFC), Sustainability,

Cost reduction technology.

I. INTRODUCTION

The status of the energy sector of a country is one of the most important parameters in defining the rate of development of the respective country. There is no modem civilization which has been developed to greater heights without the development of its energy sector. In today's scenario almost all the countries over the globe are facing the heat of energy crises. The haphazard and uncontrolled increase in the population has lead to an extreme surge demand for energy. This has resulted into uncalculated exploitation of the nonrenewable resources i.e. fossil-fuels. Also another major problem which is being faced by almost all the countries across the globe is environmental degradation. The combustion of fossil-fuels results into the inducement of various gases like SOx, NOx, COx, etc. these gases are also known as green house gases which greatly contribute in the phenomena called as the green house effect. Thus the phenomena of energy crises and environmental degradation are interconnected to a greater extent. Thus an alternate source of energy which does not contribute to environmental degradation and sustains the energy demands would be greatly compatible to the present energy ecosystems of various countries across the globe. These guidelines are rightfully observed in the case of fuel cells. Fuel cells are systems which convert chemical energy into electrical

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Jaydeep Shah3

K. K. Wagh Institute of Engineering Education and Research Amrutdham, Nashik, India

3 setijaydeep@gmail.com

energy with high efficiency and low emission of hazardous pollutants. Also they have been recognized as a power source for portable, mobile and stationary applications. Due these particular characteristics fuel cells are on the way of creating a revolutionary change in the energy sector ecosystem and also in the way a consumer engages itself with the various energy demands.

According to the different electrolytes, fuel cells can be divided into several types, such as Alkaline fuel cell (AFC), Phosphoric Acid fuel cell (PAFC), Molten Carbonate fuel cell (MCFC), Solid oxide fuel cell (SOFC), and Proton exchange membrane fuel cell (PEMFC), etc. PEMFC and SOFC are preferred over the other fuel cells as they possess qualities such as enhanced efficiency, low emission, simple construction and much greater reliability. Thus by integrating the applications of PEM fuel cells in series with renewable energy storage and production methods, sustainable energy requirements may be realized. This paper provides with the working, challenges and mitigation techniques involved in various aspects of PEMFC's.

In section II, we have reviewed the fundamental working principles, supporting reactions, construction. In section III, we have covered the various challenges which involve various factors such as cold start, economic compatibility, contamination, etc. In section IV, we have explained mitigation techniques which include new materials, technologies and research directions being pursued to try to meet the demanding performance and durability needs of the PEM fuel cell industry. In section V, we have discussed on the cost reaction, high efficiency and high performance stability of Solid Oxide Fuel Cell (SOFC).

II. POLYMER ELECTROLYTE MEMBRANE FUEL CELL

Polymer electrolyte membrane fuel cell is an electrochemical apparatus that the chemical energy of fuel without fuel combustion turned to electrical energy [1]. Polymer electrolyte membrane fuel cell typically operates on pure hydrogen fuel to generate electricity. The PEMFC combines the hydrogen fuel with the oxygen from the atmosphere to produce water, electricity and always heat [4]. The PEMFC consist of cathode, anode, bipolar plates, electro catalyst (Pt) and solid polymeric electrolyte as Nafion membrane which has ability to exchange proton. This proton conducting polymer forms the heart of each cell and

ICONCE 2014

January 16 - 17, 2014, Kalyani, WB, India.

Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

electrodes (usually made up of porous carbon with catalytic platinum incorporated with them) are bounded to either side of it to form a piece membrane electrode assembly (MEA). The role of membrane between electrodes is the conduction of produced protons from anode to cathode [1]. In the PEMFC the electrolyte (Nafion) which is permeable to protons, but does not conduct electrons. The Hydrogen flows into the fuel cell on their anode and is split into hydrogen ions (protons) and electrons. The hydrogen ions permeate across the electrolyte to the cathode, while electrons flow through an external circuit and provide power. Oxygen, in the form of air, is supplied to the cathode and this combines with the electrons and the hydrogen ions to produce water. PEMFC operates at a temperature of around 40-80°C, at this low temperature the electrochemical reaction would normally occurs very slowly so they are catalyzed by a thin layer of platinum electrode.

Hydrogen --+

••

Anode (oj +J

Fig. I. Schematic sketch of polymer electrolyte membrane fuel cell [I]

Chemistry of a fuel cell [1]:

Anode

Cathode

Net Reaction

+ -2H 2 ---> 4 H + 4e

+ -02 + 4 H + 4e ---> 2 H20

2H2 + 02 ---> 2 H20

The PEMFC can be used to bridge the gap between the rapidly increasing demand for energy and the unavailability of resources to sustain them. PEMFC operates at relatively low temperature which allows them to start up rapidly from cold and have a high power density which makes them relatively compact. The SOx and NOx Emissions are negligible and there is no noise pollution observed. Its electrical efficiency is 53-58% for transportation and 35-42% for stationary applications. It can produce 1-250W of power. Also there is no corrosive fluid spillage because the only liquid present in the cell is water.

III. MAJOR CHALLENGES FOR PEMFC

A. Cold Start

The water transport in the membrane is a combination of two competing mechanisms. One is due to the proton displacement from the anode to the cathode. As protons are solvated, they drag some water molecules with them. This phenomenon is called electro-osmotic drag [6]. In winter conditions it is unavoidable for vehicles driving below the

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freezing point of water (O°c), therefore the success full commercialization of PEMFC in automotive applications rapid startups from subzero temperature must be achieved. The major problem of PEMFC cold start is that the product water freezes when the temperature inside the PEMFC is lower than the freezing pint of water. If the catalytic layer is fully covered by ice before the cell temperature rises above the freezing point the electrochemical reaction may be stopped due to the blockage of the reaction sites. Ice formation may also result in serious damage to the structure of the membrane electrode assembly (MEA) [7].

B. Economy Compatibility

For PEMFC systems, proton exchange membranes, precious metal catalysts (usually platinum), gas diffusion layers and bipolar plates make up 70% of systems cost, in order to competitively price (compared to gasoline powered vehicles), and fuel cell systems must cost approximately $ 501KW. PEMFCs have the disadvantage of high cost because platinum catalysis or the catalysis carrying carbon and fluorine resin mixtures, etc. are used. The capital cost of PEMFC originally used in space application $ 2,0001K W is too expensive for terrestrial applications and must be reduced in order to make it more competitive [2].

C. Contamination Issues

Due to the various components making up a PEM fuel cell, the contamination sources are abundant. The sources of various contaminants originate from the fuel (hydrogen), oxidant (air) and component materials used in the PEM fuel cell. Contamination of the fuel and oxidant feed results in catalytic contamination. Impurities of the air feed appear to be many and vary significantly depending on the air quality; however NOx and SOx seem to be the dominant air contaminant species. The presence of these species even at very low concentrations can result in severe losses in the performance of the cathode [5]. Due to the low operating temperature of PEM fuel cells and the technical and practical issues associated with the economic method of hydrogen production via steam reforming of hydrocarbon fuels (mostly natural gas), contamination of the hydrogen fuel stream by these species is inevitable. The use of high purity hydrogen as the fuel for PEM fuel cells is associated with many limitations from infrastructure to refueling processes to on-board and off-board storage issues [3]. The tolerance of PEM fuel cells towards the presence of CO in the fuel is very low. Poisoning of the cell by carbon monoxide is the most researched form of contamination. The platinum catalyst on the membrane is easily poisoned by carbon monoxide (no more than one part per million is usually acceptable) and the membrane is sensitive to things like metal ions, which can be introduced by corrosion of metallic bipolar plates, metallic components in the fuel cell system or from contaminants in the fuel/oxidant [3].

IV. MlTIGA nON TECHNIQUES

A. Cost Reduction Technology

Reduction of membrane cost could be achieved by using

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Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

non-fluorinated polymer electrolyte membrane with a cheaper sulphonated polymer backbone. Sulphonation of poly (ether ketone), poly (styrene) and related material produces �igh proton conductivity polymer membrane free from fluonne. Grafting of short sulphonated side group would increase thermal stability [2]. The cost of bipolar plates could be reduced by substituting the graphite plates with composite plates formed by pressing a mixture of conducting and non­conducting polymer powders. DuPont's Nafion117 membrane is expensive, thus the large scale commercialization in an extremely competitive economy and cost sensitive markets is not compatible as the present need of the market is to manufacture functionally sound and cost viable products. use of commercially available polymer membranes such as PTFE, FEP and PF A to produce new electrolyte membranes by grafting them with styrene and sui phonic acid throu�h irradiation, looks very promising and further development IS underway to improve performance of membrane [2].

B. CO Tolarent Electrocatalyst

Since Pt is still the best electro catalyst, its low CO tolerant has been improved by using bifunctional catalysts such using alloys of Pt with Ru, Mo and Re. Electro-oxidation of C�, which would otherwise remain strongly absorbed onto Pt, IS catalyzed by oxygen-like or hydroxyl species absorbed onto neighboring Ru sites. However, bifunctional catalysts are more effective if it is arranged in a specific way but alloy molecules are arranged in random. Intermetallic compounds such as Pt-Bi may have more regular and more thermodynamically stable structure but no extensive work has been done in this area [2]. Air filters are used as a viable mitigation method of cathode contamination. Activated carbon filters are often used in the removal of nitrogen oxides and sulfur oxides from air streams and their efficiency depends highly on their physical properties [3]. Due to their effective removal of air stream contaminants, air filters have been used for the application of PEM fuel cells. The increase in water content in the membrane enhances the tolerance towards the poisoning of the membrane.

C. Non Hydrated Membrane

Effects of MEA characteristics on PEMFC cold start and the initial water content in Nafion membrane was controlled by different purging methods. They found that the best cold start capability is achieved with the lowest initial water content, because more product water can be taken by the membrane, resulting in less water freezing in the catalytic layer [7]. Current polymer electrolyte membranes must be fully hydrated for good proton conduction. The PEMFC system therefore requires the provision of a water management system that consists of air and fuel gas humidifiers and water recovery system. PEMFC system complexity could be reduced by the development of 'water­free' electrolytes that do not require hydration. It also enables the PEMFC to be operated under 'warm' conditions (i.e. above 100°C) thus further improving its efficiency. Capital cost could also be further reduced because at warmer conditions less Pt could be used [2].

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V. SOLID OXIDE FUEL CELL (SOFC)

Due to its high energy conversion efficiency and fuel flexibility, SOFCs are considered to be one of the most promising technologies for future central and distributed power generation systems. SOFC technology is most suited to applications in the distributed generation (i.e. stationary power) market because its high conversion efficiency provides the greatest benefit when fuel costs are higher, due to long fuel delivery systems to customer premises. SOFCs have a mod�lar and solid state construction and do not present any movmg parts, thereby are quiet enough to be installed in?oors. T�e high operating temperature of SOFCs produces high quality heat byproduct which can be used for co-generation, or for use in combined cycle applications. SOFCs do not contain noble metals that could be problematic in resource availability and price issue in high volume manufacture. It can generate from 1 to 1000kW. SOFCs typically operate at a temperature between 600°C and lOOO°C. Among other problems, if a reformed gas other than hydrogen is used as the fuel, cell performance tends to deteriorate due to exposure of the platinum catalyst of the electrode to carbon monoxide, and the performance of the electrolyte film itself may be reduced by long-term operation [9]. The high operation temperature makes internal reforming a feasible option so that they can directly operate using a hydrocarbon fuel such as natural gas and syngas. In addition, the high quality exhaust gas makes it an ideal candidate to form a bottoming cycle for a cogeneration system. It has been demonstrated that an atmospheric pressure tubular SOFC operate with a combined heat and power systems (CHP) can achieve electrical efficiencies greater than 45% and energy efficiencies near 75% [10]. It can be seen from degradation testing results that the cells tested at 750°C and 650°C have different degradation behaviors and structural changes that are related to carbon deposition. This similarity indicates that the dominant degradation mechanism may vary at different operation temperatures and is the effect of carbon deposition [11]. For the cell with a NilYSZ anode, however, there are two major problems when fueled with a natural gas related fuel. One problem is impurity poisoning i.e. contamination issues, such as sulfide, chloride and phosphide, which poisons the SOFC anode and leads to fast degradation. The concentration of these impurities should thus be reduced to ppb levels before feeding into the SOFC. The other problem is carbon depos�t�on because Ni is also an excellent catalyst for carbon depOSItion reactions, such as methane cracking, reduction of carbon monoxide and disproportionation of monoxide. The deposited carbon can deactivate the Ni catalyst and can cause rapid cell degradation [11].

A. Low Cost Manufacturing Process

The cost of high temperature systems which are now in the confirmation test stage cannot still be considered competitive with other power generating systems. In order to reduce the cost of cells and stacks, it will be necessary to minimize the use of expensive materials, simplify the manufacturing process, and establish manufacturing methods suitable

.for

mass production. As the electrolyte and elect rode matenals

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Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

are ceramics, various technical issues must be solved in connection with the preparation of the ceramic raw material powders and the powder slurry and the subsequent molding and the sintering process as manufacturing processes peculiar to ceramics. In forming thin films of the electrolyte, gas phase methods such as pulsed-laser deposition (PLD) can be used in the laboratory, but when considering mass production in the future, a wet process film-forming technology such as the tape casting method is desired [9].

B. High Generating Performance and Long term Performance Stability

The investigation of the direct oxidation of natural gas suggested that the carbon deposition on a NiIYSZ anode could be avoided by lowering the operation temperature «700°C) and increasing the operation current density. These operation parameters, however, are difficult to attain in real SOFC systems. A high steam to carbon ratio (SIC) has also been used to avoid carbon deposition in the internal steam reforming of natural gas, but it reduces the cell electrical efficiency by diluting the fuel [11]. When using hydrocarbon fuels, it is necessary to set the reaction temperature of the fuel so as to prevent carbon precipitation and thereby avoid performance deterioration. In order to maintain the original performance of the FCs and minimize performance deterioration over time, it is important to select a combination of materials, including the electrolyte and electrode materials, which is suitable for service environment conditions, including the operating temperature. There is a possibility that all of the problems of maintaining long-term generating performance, Securing high reliability, and the like can be solved at once by reducing the operating temperature. To achieve this, it will be necessary to discover a new electrolyte which ha s low electrical resistance, in other words, an electrolyte with high ionic conductivity, in the low temperature region [9].

C. Improving Efficiency of so Fe SOFC's efficiency improves as the ionic conductivity of

the electrolyte used increases. This is explained by the fact that, in many cases, virtually all of the internal resistance in a cell is attributable to electrical resistance loss caused by resistance in the electrolyte. In high temperature (750°C­lOOO°C) SOFCs, much research has been done on yttria­stabilized zirconia (YSZ: Y 203 stabilized Zr02) as the electrolyte, nickel zirconia (Ni-Zr02) cermet as the fuel electrode material , lanthanum manganite ( LaMn03) as the air electrode material, and lanthanum chromite (LaCr03) as the separator. However, materials with high oxygen ion conduction, such as scandia-stabilized zirconia (SSZ: SC203 stabilized Zr02), lanthanum gallate (LaGa03), and others, have been the object of intensive research as non-YSZ electrolytes in recent years. In addition to these electrolytes, Research & Development is also being done on various hydrogen ion conductors, such as barium cerate (barium cerium oxide; BaCe03), strontium cerate (SrCe03), and related materials. Nevertheless, in terms of ion conduction characteristics, chemical stability, cost and the number of examples of R&D, even today YSZ continues to be the most

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important electrolyte. SSZ and LaGa03 are promlsmg materials for application as electrolytes for medium temperature SOFCs operating at 750°C and under. YSZ, the cerate based electrolytes, and LaGa03 reveal increasingly high oxygen ionic conductivity in that order [9].

VI. CONCLUSION

This paper gives an overview of the characteristics and performance of PEMFC and SOFC then working principle, and finally analyses its cost reduction techniques. With the development of renewable energy power generation, micro grid, which integrates distributed generations, is considered progressive to effectively meet the growing power demand, economize the investment and improve energy efficiency.

Due to there is an increasing demand for fuel cells especially Proton exchange fuel cells and Solid oxide fuel cell because of various factors such as enhanced efficiency, low emission simple construction, power source for portable, mobile and stationary applications. In this paper various challenges such as cold start, economic compatibility, contamination, etc which are involved with the various aspects of PEMFC's and SOFC's have been discussed. Also how to cope up with these issues have also discussed. As fuel cell system with huge energy production, wide operating temperature range, reliability and security, low maintenance, and its application in the automotive and stationary sector will promote the technological progress and gain greater economic benefits.

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Proceedings of 2014 1st International Conference on Non Conventional Energy (ICONCE 2014)

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