fuel cell for energy storage

FUEL CELL FOR ENERGY STORAGE

1. Abstract

This study provides a survey of fuel cell technology and application. A description of fuel cell operating principles is followed by a comparative analysis of the fuel cell technology together with advantages and disadvantages. A literature survey is done for six papers. A detailed study on research paper “Pyrolysis of Palm waste for the application of direct carbon fuel cell” has been done.

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2. Introduction

“A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction of positively charged hydrogen ions with oxygen or another oxidizing agent.”

A fuel cell is like a battery in that it generates electricity from an electrochemical reaction. Both batteries and fuel cells convert chemical energy into electrical energy and also, as a by-product of this process, into heat. However, a battery holds a closed store of energy within it and once this is depleted the battery must be discarded, or recharged by using an external supply of electricity to drive the electrochemical reaction in the reverse direction.

A fuel cell, on the other hand, uses an external supply of chemical energy and can run indefinitely, as long as it is supplied with a source of hydrogen and a source of oxygen (usually air). The source of hydrogen is generally referred to as the fuel and this gives the fuel cell its name, although there is no combustion involved. Oxidation of the hydrogen instead takes place electrochemically in a very efficient way. During oxidation, hydrogen atoms react with oxygen atoms to form water; in the process electrons are released and flow through an external circuit as an electric current.

Fuel cells can vary from tiny devices producing only a few watts of electricity, right up to large power plants producing megawatts. All fuel cells are based around a central design using two electrodes separated by a solid or liquid electrolyte that carries electrically charged particles between them. A catalyst is often used to speed up the reactions at the electrodes. Fuel cell types are generally classified according to the nature of the electrolyte they use. Each type requires particular materials and fuels and is suitable for different applications.

Figure 1 Fuel cell

Anode reaction: 2H2 4H+ + 4e‾

Cathode reaction: O2(g) + 4H+ + 4e‾ 2H2O

Overall cell reaction: fuel + oxidant product + Heat2H2 + O2 +4e- 2H2O + Heat

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3. History

The first references to hydrogen fuel cells appeared in Sketch of William Groove’s 1839 fuel cell. Groove later sketched his design, in 1842, in the same journal. The fuel cell he made used similar materials to today’s phosphoric-acid fuel cell.

In 1939, British engineer Francis Thomas Bacon successfully developed a 5 kW stationary fuel cell. In 1955, W.Thomas Grubb, a chemist working for the General Electric Company (GE), further modified the original fuel cell design by using a sulphonated polystyrene ion-exchange membrane as the electrolyte. In the 1960s, Pratt and Whitney licensed Bacon’s U.S. patents for use in the U.S. space program to supply electricity and drinking water (hydrogen and oxygen being readily available from the spacecraft tanks). In 1991, the first hydrogen fuel cell automobile was developed by Roger Billings.

Year History

1839 Sir William Robert Groove H2-O2 fuel cell

1889 Term fuel cell coined by Ludwig Mond, Charles Langer &they used Platinum as catalyst

1920 Development of SOFC in Germany

1950 Development of PEFC by GE

1959 Development of 5KW AFC by Francis Bacon

1960 Gemini and Apollo spacecraft by NASA

1980 US Navy uses fuel cell in submarine

1993 First bus powered by fuel cell

1996 Toyota demonstrates experimental PEMFC car with metal hybrid storage

2000 Honda FCX-V3 & NISSAN (FCV) vehicles GM H1 fuel cell vehicle

2001 Fuel cell bike by Aprilia

2004 Honda delivers hydrogen powered fuel cell vehicle to the MAYOR of San Francisco

2009 Residential fuel cell, portable fuel cell battery chargers were sold in JAPAN

4.Fuel Cell VS Battery

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Fuel Cell Battery

Generate Power Electrochemically Generate Power Electrochemically

Gases are the working materials Electrodes are the working materials

Electrodes do not get consumed Electrodes get consumed

Continue to operate as long as fuel gas is supplied

Limited operation

Conversion device Storage device

5.Engine VS Fuel Cell

Figure 2 Engine VS Fuel Cell

It is seen from above figure 2 thati. In fuel cell there is direct conversion of energy.

ii. Whereas in thermal power plant or engine chemical energy is converted to thermal further to mechanical and then to electricity so there are losses at each stage.

Therefore, thermal efficiency of fuel cell is greater than that of engine.

6. Classification of Fuel Cells

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Alkaline FC Phosphoric Acid FC

Solid Oxide FC

Molten Carbonate FC

Polymer Membrane FC

Operating Temp range (K)

53-373 373-493 973-1273 923-1123 303-353

Charge Carrier

OH- H+ O2- CO32- H+

Electrolyte KOH H3PO4 YSZ Li2 CO3& K2CO3 NafionAnode Pt-Pd PTFE Ni/YSZ Ni PTFECathode Pt-Au PTFE Sr (Strontium) Li PTFEFuel H2 H2 H2,CO H2,CO H2

Oxidant O2 O2 O2 O2+CO2 O2

Current density

High Moderate High Moderate High

PTFE –Polytetrafluoroethylene

YSZ-Zirconia

7. Advantages

The main advantages of fuel cells are:1) Efficiency - Fuel cells are generally more efficient than combustion engines as they are

not limited by temperature as is the heat engine.2) Simplicity- Fuel cells are essentially simple with no moving parts. High reliability may

be attained with operational lifetimes exceeding 40,000 hours (the operational life is formally over when the rated power of the fuel cell is no longer satisfied)

3) Low emissions- Fuel cells running on direct hydrogen and air produce only water as the by product.

4) Silence- The operation of fuel cell systems are very quiet with only a few moving parts if any. This is in strong contrast with present combustion engines.

5) Flexibility - Modular installations can be used to match the load and increase reliability of the system.

8. Disadvantages

1) High market entry cost, production cost2) Unfamiliar technology to the power industry3) Almost no infrastructure4) Still at level of development

9. Applications1) Transportation

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2) Military3) Space

10. Literature Review

Paper 1 Paper 2 Paper 3Title Pyrolysis of Palm waste

for the application of direct carbon fuel cell

Fuel cell technology and application

Bioelectricity Generation and Treatment of Sugar MillEffluent Using a Microbial Fuel Cell

Description Heat treatment such as pyrolysis is utilized in converting the biomass into biochar which possesses slightly different physicochemical properties, such as higher C% and large surface area.

Palm shell pyrolyzed at temperature of 750°C, with heating rate of 10°C/min and residence time of 1 hour produced a highly potential biochar for DCFC application.

Provides a survey of fuel cell technology and application.

A description of fuel cell operating principles is followed by a comparative analysis of the current fuel cell technology together with issues concerning various fuels.

Microbial fuel cells are (MFCs) fascinating bioelectrochemical devices that use living catalysts to produce electric energy from organic matter present naturally in the environment or in waste

In this study, sugar mill effluent

(SME) was used as the anodic substrate in a double chambered

MFC for an application of electricity generation.

Conclusion Palm shell biochar produced by pyrolysis at temperature beyond 750 °C exhibit high similarities in term of chemical composition.

Furthermore, biochar obtained at 900 °C possesses much larger surface area as compared to carbon black.

These similarities give an indication that palm shell biochar could be a highly potential fuel for DCFC.

As fuel cell application increases and improved fuel storage methods and handling is developed, it is expected that the costs associated with fuel cell systems will fall dramatically in the future.

An MFC was operated using SME for bio electricity production and its treatment. Polyacrylonitrile carbon felt was used as the electrode material in both chambers of the MFC. The cell was operated for 15 days in batch-fed mode. The maximum power density 140 mW/m2was successfully achieved and maximum 56% reduction in COD was measured using 50% SME as a substrate

Paper 4 Paper 5 Paper 6Title Performance evaluation of

solid oxide fuel cell with A simplified PEM fuel cell model for building

Effect of temperature uncertainty on polymer

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in-situ methane reforming. cogeneration applications. electrolyte fuel cell performance.

Description Performance evaluation of SOFC fuelled with carbon based fuels like CH4 were

carried out on (LSGM) electrolyte supported single cell with symmetrical electrodes consisted of (LSCFN)and (GDC) functional layers and LSCFN current collect layers. In-situ reforming of methane by carbon dioxide at the anode was successfully achieved on LSCFN based anode, which greatly enhanced the cell performance.

On the building cogeneration applications of polymer electrolyte membrane(PEM) fuel cells because they have high power density (small stack size), high cogeneration efficiency (sum of heat and power), and fast startup time owing to their low operating temperature

PEM fuel cell systems generate power for buildings, and the recovered heat is used for domestic hot water or heating.

The temperature of operation is a key parameter in determining the performance and durability of a polymer electrolyte fuel cell (PEFC). Controlling temperature and understanding its distribution and dynamic response is vital for effective operation and design of better systems.

The sensitivity to temperature means that uncertainty in this parameter leads to variable response and can mask other factors affecting performance.

Conclusion In-situ reforming of methane by carbon dioxide at the anode was achieved with LSCFN based anode material.

Cell performance was dramatically promoted when CO2–CH4 mixture was used as anode fuel compared with pure CH4, which was mainly contributed by the formation of H2 and CO from CO2 dry reforming of methane reaction.

The maximum power density of the single cell was dramatically increased from 280 to 455 mW/cm2 when fuelled with 10% CO2

–

90% CH4 compared with pure methane at 850°C with a fuel inlet rate of 50 mL/min.

A cogeneration system provides savings in primary energy and cost.

A simplified fuel cell model is suggested for commercial packaged fuel cells by adding some new variables and validating through experimental and published data. This model is relatively simple compared to other models but can be easily utilized in some limited cases with performance predictions.

A simple lumped mathematical model is used to describe PEFC performance under temperature uncertainty. An analytical approach gives a measure of the sensitivity of performance to temperature at different nominal operating temperatures and electrical loadings.

Whereas a statistical approach, using Monte Carlo stochastic sampling, provides a ‘probability map’ of PEFC polarisation behaviour.

11. Concept (Research Paper): Pyrolysis of Palm waste for the application of direct carbon fuel cell

11.1 Abstract

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Direct carbon fuel cell (DCFC) is a high-temperature fuel cell which operates directly from solid carbon. From the past research, it is proven to be capable of achieving nearly 100% theoretical efficiency. Thus, DCFC commercialization would change the course of power generation industry into a more sustainable and environmental friendly means of generating electricity. Although biomass constitutes of carbon (C), they exist in different forms, making them unsuitable to be used directly as fuel in DCFC. For that purpose, heat treatment such as pyrolysis is utilized in converting the biomass into biochar which possesses slightly different physicochemical properties, such as higher C% and large surface area. It was found that, palm shell pyrolyzed at 750°C, with heating rate of 10°C/min and residence time of 1 hour produced a highly potential biochar for DCFC application.

11.2 Introduction

Current electricity generation mainly depends on combustion of fossil fuels, such as coal. This method releases significant amount of pollutants into atmosphere. Such problem could be avoided with the introduction of DCFC technology. Malaysia, as the second largest palm oil exporters in the world, has generated ample amount of palm waste each year. Such waste could be utilized in electricity generation, presenting a sustainable yet green energy solution. However, palm wastes are similar to other biomasses; due to their undesirable physicochemical properties, they could not be used readily in DCFC. The importance of high C% in DCFC performance has been reported, such that lack of C% in the fuel could lead to linear decrease in voltage at high current density region. This is due to the restricted consumption when large amount of electrons are flowing. Additionally, presence of inorganic compounds could have catalytic or negative effects on DCFC performance. Furthermore, surface oxygen functional groups could act as active sites for electrochemical oxidation; while textural properties such as extensive surface area and porosity provide extra contact between fuel and electrolyte, contributing to DCFC performance. Other than the influence of constituent biomass, characteristics of biochar are highly dependent on operating conditions of pyrolysis, such as pyrolysis temperature, heating rate and residence time. It was reported that an increase in pyrolysis temperature increases C% as well as creating high surface area. Moreover, long residence time and low heating rate would also promote desirable characteristics for the improvement in DCFC performance. In this study, experiment was carried out to explore the potential of using palm shell as fuel in DCFC. The effect of pyrolysis temperature on the characteristics of palm shell biochar was examined. The potential of the biochar as DCFC fuel is estimated by comparing their characteristics such as chemical composition, surface oxygen functional groups and textural properties with common DCFC fuel such as carbon black.

11.3 Experimental works

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Palm shell was dried in the oven for 24 hours at 110°C for moisture removal. The dried palm shell was then grinded and sieved to obtain a size ranging from 0.5 mm-1 mm. 0.5 g palm shell underwent pyrolysis at 450, 600, 750 and 900°C respectively. Pyrolysis was carried out at heating rate of 10°C/min, residence time of 1 hour, and N2 flow rate of 2 L/min. Pyrolyzed palm shell samples are denoted as PS450, PS600, PS750 and PS900 with respect to their pyrolysis temperature. Results from proximate analysis were used in the selecting biochar of high similarities with carbon black in terms of chemical composition. The selected biochar were further examined in terms of surface area, porosity and functional groups throughN2

adsorption, and Fourier transforms infrared spectroscopy (FTIR), respectively.

11.4 Results and discussion

Samples Moisture Volatile matter Fixed carbon Ash content

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Dried Oven for 24 hrs,110°CFor Moisture removal

Grinded Size 0.5mm to 1mm

Pyrolysis0.5g450°C,600°C,750°C,900°CPS450,PS600,PS750,PS900HR=10°C/min,Residence time 1hr,N2 flow rate=2 L/min


Carbon black 2 0 94 4PS450 5 29 63 3PS600 4 11 81 4PS750 4 6 86 4PS900 5 3 87 5

Table 1 Proximate analysis of biochar samples and carbon black

As shown in Table 1, the volatile matter, C% and ash content increase with increasing pyrolysis temperature. However, the increment is non-linear and stays rather constant after 750°C. It was reported that a high concentration of volatiles will be released during pyrolysis at high temperature and part of the volatiles could be trapped within the carbon matrix of biomass, forming secondary char that contributes to a high C% [4]. Beyond thermal treatment at 750°C, the release of volatiles and C formation are almost completed, and resulting in consistency in chemical composition of biochar samples. By comparing PS450 to the rest of biochar samples and carbon black, it is evident that the release of volatiles is incomplete, and the C% may be too low to be used as DCFC fuel. As for PS600, the volatile content is rather high. In terms of chemical composition, PS750 and PS900 have higher degree of similarity with that of carbon black, making them highly potential as DCFC fuel. Thus, PS750 and PS900 were selected for further characterization.

Samples Surface area ( m2/gm )Carbon black 202.99PS750 204.31PS900 270.88

Table 2 Surface areas, volumes, and average pore size of biochar and carbon

Figure 3 Adsorption isotherms of (a) Carbon black (b) PS750 (c) PS900

As shown in Table 2, PS750 and PS 900 possessed higher surface area as compared to carbon black. Surface area increases with increasing pyrolysis temperature. As observed in Figure 3, the adsorption isotherms of PS750 and PS900 belong to Type I isotherm, suggesting adsorption occurs on microporous solids, this result is in conjunction with the micropore structure of biochar, which contributes to most of the total surface area. However, with the increase in relative pressure, a slight decrease in quantity of N2adsorbed is observed. This situation could be due to the insufficient energy possessed by N2 for adsorption. CO2

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adsorption will produce a more accurate measurement [5]. As for carbon black, it exhibits Type III isotherm, which suggests the structure is non-porous. Furthermore, the average pore diameter of carbon black is 7.90 nm and this confirmed the lack of micropores in carbon black. The higher surface area of biochar samples is believed to be able to compensate for the lack of fixed carbon as compared to carbon black. Higher surface area enables more contact between fuel particles and anode layer, enabling higher electrochemical oxidation rate of carbon in DCFC.

Figure 4 FTIR Spectra of carbon back and biochar samples PS750 and PS900

As shown in Figure 4, it is evident that all three curves are of highly similarity, suggesting the presence of similar functional groups. Band at 3400cm-1 corresponds to O-H stretching due to presence of H2O,phenol or alcohol groups. Band at 2900cm-1 is associated with C-H stretching of aromatics. Band at1600cm-1 is associated with C=C stretching of aromatic compounds. Bands at 1400 cm-1 and 1100cm-1 correspond to O-H bending of alcohol or carboxylic acid and C-O stretching of alcohol, respectively. A band at 2260 cm-1 corresponds to nitrile group, can be observed for carbon black and PS750. The absence of nitrile group in PS900 could be due to high thermal treatment on the biochar, which possibly causes thermal degradation of the nitrile group [6]. The high similarities in terms of presence of oxygen-based functional groups in both carbon black and biochar samples further elevate the potential of biochar as DCFC fuel. These oxygen functional groups provide active sites for carbon oxidation in DCFC.

11.5 Conclusion

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Palm shell biochar produced by pyrolysis at temperature beyond 750 ºC exhibit high similarities in term of chemical composition. Furthermore, biochar obtained at 900 ºC possesses much larger surface area as compared to carbon black. Both biochar and carbon black contain similar oxygen functional groups. These similarities give an indication that palm shell biochar could be a highly potential fuel for DCFC. Nevertheless, reaction testing of biochar in DCFC is recommended to give a quantitative measurement of its suitability. Furthermore, additional characteristics such as morphology and degree of graphitization should be examined for in depth comparison with carbon black.

12 References

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[1] Ahn SY, Eom SY, Rhie YH, Sung YM, Moon CE, Choi GM, Kim DJ. Utilization of wood biomass char in a direct carbon fuel cell (DCFC) system. Applied Energy 2013;105: 207-216.

[2] Li X, Zhu Z, De Marco R, Bradley J, Dicks A. Evaluation of raw coals as fuels for direct carbon fuel cells. Journal of Power Sources 2010;195: 4051-8.

[3] Li X., Zhu Z, Chen J, De Marco R, Dicks A, Bradley J, Lu G. Surface modification of carbon fuels for direct carbon fuel cells. Journal of Power Sources 2009;186: 1-9.

[4] Lua, AC, Lau FY, Guo J. Influence of pyrolysis conditions on pore development of oil-palm-shell activated carbons. Journal of analytical and applied pyrolysis 2006;76: 96-102.

[5] McLaughlin H, Shields F, Jagiello J, Thiele G. Analytical Options For Biochar Adsorption and Surface Area. US Biochar Conference session on Char Characterization. 2012

[6] Grassie N, McNeill I. Thermal degradation of polymethacrylonitrile. Part II. The coloration reaction.Journal of Polymer Science 1958; 27: 207-218.

[7] Fuel Cells Principles and Applications by B Vishwanathan,MAuliceScibioh

[8] Fuel Cell Technology and Application by B.J. Holland, J.G. Zhu, and L. Jamet.

[9] Bioelectricity Generation and Treatment of Sugar Mill Effluent Using a Microbial Fuel Cell by Ravinder Kumar, Lakhveer Singh, and A.W. Zularisam .Journal of Clean Energy Technologies, Vol. 4, No. 4, July 2016

[10] Performance evaluation of solid oxide fuel cell with in-situ methane reforming by Tenglong Zhu, Zhibin Yang ,Minfang Han.

[11] A simplified PEM fuel cell model for building cogeneration applications by Sang-Woo Ham, Su-Young Jo, Hye-Won Dong, Jae-Weon Jeong.

[12] Effect of temperature uncertainty on polymer electrolyte fuel cell performance byMozhdeh Noorkami a, James B. Robinson, Quentin Meyer, Oluwamayowa A. Obeisun, Eric S. Fraga, Tobias Reisch, Paul R. Shearing.

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