PHOSPHORIC ACID FUEL CELL

Phosphoric acid fuel cell

PHOSPHORIC ACID FUEL CELL (PAFC) is the most mature fuel cell technology in terms of system development and commercialization. It uses phosphoric acid (H3PO4) electrolyte in a Teflon? bonded silicon carbide matrix. Some acid fuel cells use a sulfuric acid electrolyte. Characteristics PAFCs have the following characteristics:

a. PAFC function at 150-220°C and 15 psig (1 barg). Each cell can produce 1.1 VDC.

b. The operation life exceeds 65000 hours.

c. The overall cell efficiency is up to 40% which can be boosted up to 60% using CHP.

d. Because the cells operate at high temperatures, pure hydrogen is not required as a fuel. This permits the cell to run on somewhat impure hydrogen from the fuel reforming process.

PAFC Structure The fundamental cell structure is a ceramic matrix filled with phosphoric acid solution, surrounded by porous electrodes for collecting ions and diffusing gases. The phosphoric acid-containing ceramic matrix is composed of 1 mm silicon carbide particles, with a matrix thickness of 0.1-0.2 mm. The porous structure of the matrix keeps the acid within the layer and prevents gas cross-over from anode to cathode. The operating temperature is around 150-220°C. The operating temperature requires platinum catalyst although at this temperature range it is sensitive to CO-poisoning

The oxygen needed for the cathode of the fuel cell is simply taken from the air. The hydrogen required for the anode must be extracted from liquid natural gas or methanol. This process is called reformation. The purified hydrogen is fed into the anode of the fuel cell. This fuel is fed through parallel grooves formed of carbon composite plates. These plates are electrically conductive and conduct electrons from the anode to the cathode of the adjacent cell. The design requires the plates to be “bi-polar” which means that one side supplies fuel to the anode, while the other side supplies air or oxygen to the cathode. All the hydrogen in the anode exhaust is not consumed in the fuel cell. The remaining anode exhaust is fed back into the reformer burner, which burns the remaining hydrogen and maintains the high temperature required for the reforming process. Also, water (steam) is recovered from the cathode exhaust to maintain the necessary water supply to the reformer. The water recovery procedure requires that the system be operated at temperatures around 190°C. If the water is not removed, it will dissolve in the phosphoric acid electrolyte and decompose the acid.

Phosphoric acid is employed as the electrolyte because it is the only inorganic acid that has the required thermal, chemical, and electrochemical stability. Carbon monoxide poisoning and carbonate formation is not a problem for PAFCs since phosphoric acid requires high operating temperatures and does not react with CO2.

Reactions

Anode reaction: H2 → 2H+ + 2e

Cathode reaction: ?O2 +2H+ + 2e- → H2O

Overall reaction: H2 + ?O2 → H2O

Advantages and Disadvantages

Advantages

a. Simple construction, low electrolyte volatility, and long-term working stability.

b. Are tolerant of carbon dioxide (up to 30%). So phosphoric acid fuel cells can use clean air as an oxidant and reformate as fuel

c. Higher overall efficiency with CHP Increased tolerance to impurities in hydrogen

Disadvantages

a. Can tolerate only about 50 ppm of total sulfur compounds

b. Use a corrosive liquid electrolyte causing material corrosion problems

c. Heated steam generated by PAFCs is too low in temperature to be used inside big, combined heat and power (CHP) systems.

d. Have a liquid electrolyte, introducing liquid handling problems. The electrolyte slowly evaporates over time

e. Allow product water to enter and dilute the electrolyte

f. Are big and heavy

g. Cannot auto-reform hydrocarbon fuels

h. Must be warmed up before they are operated or be continuously maintained at their operating temperature

i. Requires expensive platinum catalysts Low current and power Large size/weight

Applications The operative temperature of the PAFCs is too low to be successfully used inside big stationary power generating applications. But these are useful in small, distributed power generation.

Phosphoric acid fuel cells (PAFCs) were first designed and introduced in 1961 by G. V. Elmore and H.A. Tanner. In these cells, phosphoric acid is used as a non-conductive electrolyte to pass protons from the anode to the cathode and to force electrons to travel from anode to cathode through an external electrical circuit. These cells commonly work in temperatures of 150 to 200?°C. This high temperature will cause heat and energy loss if the heat is not removed and used properly. This heat can be used to produce steam for air conditioning systems or any other thermal energy-consuming system. Using this heat in cogeneration can enhance the efficiency of phosphoric acid fuel cells from 40 to 50% to about 80%. Since the proton production rate on the anode is small, platinum is used as a catalyst to increase this ionization rate. A key disadvantage of these cells is the use of an acidic electrolyte. This increases the corrosion or oxidation of components exposed to phosphoric acid.

Phosphoric Acid Fuel Cells

Acid electrolyte cells are more tolerant to CO2 and allow the use of normal air and non-pure hydrogen. But the corrosion problem restricts the choice of construction materials especially for the electrodes and the catalysts. The electrodes can be made out of gold, tatalum, titanium and carbon and only the platinum group metals can be used as catalysts. The acid used as the electrolyte must be non-volatile, such as sulfuric and phosphoric acids, so that only water is lost by evaporation.

The electrolyte in the PAFC is a paper matrix saturated with phosphoric acid, transporting the hydrogen ions. The operating temperature is around 200 °C. The operating temperature require platinum as catalyst which is supported being dispersed on graphite material. But platinum at this temperature is sensitive to CO-poisoning.

Cells which use hydrocarbons directly as fuel around 150 °C have low efficiency and current density, thus have been restricted to research investigations. Alcohol fuels and impure hydrogen (containning CO and CO2 produced by reforming hydrocarbons) have been used by various companies.

In general, the performances of acid cells are much lower than that of alkaline cells, due to the poorer performances of the air electrode, probably because of the increased stability of formed perroxides in an acid environment. However there are many compromises that can be made between alkaline and acid fuel cells, considering the constructions and operating temperature and regarding the probable use of the desired cell.

?Anode reaction:H2?→ 2H+ + 2e-??

Cathode reaction:??O2 +2H+ + 2e- → H2O?

Overall reaction:?H2 + ?O2 → H2O

The efficiency of a PAFC in generating electricity is greater than 40%. Simple construction, low electrolyte volatility, and long-term stability are additional advantages. Phosphoric acid (H3PO4) concentrated to 100% is used for the electrolyte in this fuel cell, which operates at 150–220°C, since the ionic conductivity of phosphoric acid is low at low temperatures. The relative stability of concentrated phosphoric acid is high compared to other common acids. In addition, the use of concentrated acid minimizes the water vapour pressure, so water management in the cell is not difficult. The matrix universally used to retain the acid is silicon carbide and the electrocatalyst in both the anode and cathode is platinum (Pt).

The charge carrier in this type of fuel cell is the hydrogen ion (H+, proton). The hydrogen introduced at the anode is split into its protons and electrons. The protons are transferred through the electrolyte and combine with the oxygen, usually from air, at the cathode to form water. In addition, CO2 does not affect the electrolyte or cell performance and can therefore be easily operated with reformed fossil fuels.

The charge carrier in this type of fuel cell is the hydrogen ion (H+, proton). The hydrogen introduced at the anode is split into its protons and electrons. The protons are transferred through the electrolyte and combine with the oxygen, usually from air, at the cathode to form water. In addition, CO2 does not affect the electrolyte or cell performance and can therefore be easily operated with reformed fossil fuels.

The phosphoric acid fuel cell (PAFC) is named for the catalyst that is used in it. The working principle of the PAFC is similar to that of the PEMFC. Hydrogen is used as a fuel and is oxidized at the anode, generating free electrons moving toward the external circuit and the protons moving through the selectively permeable membrane toward the cathode. At the cathode, a reduction reaction takes place where the oxygen reacts with the protons and electrons. The oxidation and reduction reactions are shown in Eqs. (2.59), (2.60), respectively. Fig. 2.28 shows the conversion process of the phosphoric acid fuel cell.

Oxidation at anode:

(2.59)Anode:2H2?4H++4e?

Reduction at cathode:

(2.60)Cathode:O2+4H++4e??2H2O

Phosphoric acid fuel cells (PAFCs) are fuel cells that use liquid phosphoric acid as an electrolyte – the acid is contained in a Teflon-bonded silicon carbide matrix – and porous carbon electrodes containing a platinum catalyst. The chemical reactions that take place in the cell are shown in the diagram.?

The phosphoric acid fuel cell is considered the "first generation" of modern fuel cells. It is one of the most mature cell types and the first to be used commercially. This type of fuel cell is typically used for stationary power generation, but some PAFCs have been used to power large vehicles such as city buses.?

PAFCs are more tolerant of impurities in fossil fuels that have been reformed into hydrogen than PEM cells, which are easily "poisoned" by carbon monoxide because carbon monoxide binds to the platinum catalyst at the anode, decreasing the fuel cell's efficiency. They are 85% efficient when used for the cogeneration of electricity and heat but less efficient at generating electricity alone (37%–42%). This is only slightly more efficient than combustion-based power plants, which typically operate at 33%–35% efficiency. PAFCs are also less powerful than other fuel cells, given the same weight and volume. As a result, these fuel cells are typically large and heavy. PAFCs are also expensive. Like PEM fuel cells, PAFCs require an expensive platinum catalyst, which raises the cost of the fuel cell. A typical phosphoric acid fuel cell costs between $4,000 and $4,500 per kilowatt to operate.

If gasoline or diesel is used as a basic fuel, sulfur must be removed from the fuel prior to use or it will damage the electrode catalyst.

PAFCs are more tolerant of impurities in fossil fuels that have been reformed into hydrogen than are PEMFCs.

The electrical efficiency for PAFCs is 40% to 50%, and when the energy produced by the waste heat is considered, the efficiency rises to about 80%. Today, PAFCs are used in commercial electrical production.

The PAFC can tolerate a concentration of carbon monoxide (CO) of about 1.5%, which is a larger concentration than can be tolerated by other types of fuel cells.

?Another advantage to the PAFC is that the phosphoric acid electrolyte can operate above the boiling point of water.

A disadvantage of the PAFC is that, when compared to other fuel cells of similar weight and volume, it produces less power.

Also, PAFCs are expensive because of the platinum catalyst and the need for corrosion-resistant materials (because of the acid).

Phosphoric acid fuel cells

Phosphoric acid fuel cells (PAFCs) use liquid phosphoric acid as an electrolyte—the acid is contained in a Teflon-bonded silicon carbide matrix—and porous carbon electrodes containing a platinum catalyst. The electro-chemical reactions that take place in the cell are shown in the diagram to the right.

The PAFC is considered the "first generation" of modern fuel cells. It is one of the most mature cell types and the first to be used commercially. This type of fuel cell is typically used for stationary power generation, but some PAFCs have been used to power large vehicles such as city buses.

PAFCs are more tolerant of impurities in fossil fuels that have been reformed into hydrogen than PEM cells, which are easily "poisoned" by carbon monoxide because carbon monoxide binds to the platinum catalyst at the anode, decreasing the fuel cell's efficiency. PAFCs are more than 85% efficient when used for the co-generation of electricity and heat but they are less efficient at generating electricity alone (37%–42%). PAFC efficiency is only slightly more than that of combustion-based power plants, which typically operate at around 33% efficiency. PAFCs are also less powerful than other fuel cells, given the same weight and volume. As a result, these fuel cells are typically large and heavy. PAFCs are also expensive. They require much higher loadings of expensive platinum catalyst than other types of fuel cells do, which raises the cost.

A phosphoric acid fuel cell consists of liquid phosphoric acid electrolyte sandwiched between an anode (negatively charged electrode) and a cathode (positively charged electrode). The processes that take place in the fuel cell are as follows:

1. Hydrogen fuel is channeled through field flow plates to the anode on one side of the fuel cell, while oxygen from the air is channeled to the cathode on the other side of the cell.

2. At the anode, a platinum catalyst causes the hydrogen to split into positive hydrogen ions (protons) and negatively charged electrons.

3. The phosphoric acid electrolyte allows only the positively charged ions to pass through it to the cathode. The negatively charged electrons must travel along an external circuit to the cathode, creating an electrical current.

4. At the cathode, the electrons and positively charged hydrogen ions combine with oxygen to form water, which flows out of the cell.

What is Phosphoric Acid Fuel Cell (PAFC)?

The Phosphoric Acid Fuel Cell (PAFC) is a power generation device that uses phosphoric acid as an electrolyte to convert chemical energy into electrical energy through chemical reactions.

?Phosphoric Acid Fuel Cells were first invented by the American scientist R.A. Huggins in the 1950s and saw commercial applications in the 1960s. With continuous technological advancements, both the manufacturing processes and performance of Phosphoric Acid Fuel Cells have been steadily improving. Simultaneously, their application fields have expanded.

?Currently, Phosphoric Acid Fuel Cells are widely utilized in various areas, including stationary power sources, transportation, portable power sources, etc. They have become an important direction in the development of clean energy, benefiting from advancements in technology and an increasing focus on sustainable energy solutions.?

Feature

Operating Temperature: PAFC operates at a relatively high temperature, typically between 150 to 200 degrees Celsius (approximately 302 to 392 degrees Fahrenheit). This higher temperature is necessary for phosphoric acid to act as an effective electrolyte.?

High energy density and power density: It refers to the capability of the Phosphoric Acid Fuel Cell, to store a large amount of energy and deliver a high amount of power per unit volume or weight.?

Achieving efficient energy conversion：It means that the Phosphoric Acid Fuel Cells (PAFCs) are capable of effectively converting chemical energy into electrical energy. Efficiency in energy conversion is crucial as it determines how much of the input energy is successfully transformed into usable electrical power.?

Longer lifespan: Phosphoric Acid Fuel Cells (PAFCs) indicates that these fuel cells have a relatively extended operational life. The lifespan of a fuel cell refers to the duration over which it can operate efficiently and reliably before experiencing a decline in performance.?

Principle of reaction?

Cathode：

O2+4H+4eˉ = 2H2O

Anode：

H3PO4+3H2O+8eˉ = 4H3O2H?

Types & Uses

Types:

Phosphoric Acid Fuel Cells can be classified into various types based on their environmental usage and applications, such as plate-type, cylindrical-type, tubular-type, etc.?

Stationary Power Source:

Phosphoric Acid Fuel Cells can serve as a stationary power source, providing power for urban, industrial, rural, and other areas. They are capable of meeting the long-duration and high-power electricity demands in various applications.?

Transportation:

Phosphoric Acid Fuel Cells can be utilized as a power source for new energy vehicles, offering advantages such as high energy density, low noise, and zero emissions. They can meet the environmental and energy-saving requirements in the field of transportation.?

Portable Power Source:

Phosphoric Acid Fuel Cells can also function as a portable power source, catering to power requirements in outdoor, emergency, and other situations. ?

PHOSPHORIC ACID FUEL CELLS (PAFCs)

The phosphoric acid fuel cell (PAFC) was the first fuel cell technology to be commercialized. The number of units built exceeds any other fuel cell technology, with over 85 MW of demonstrators that have been tested, are being tested, or are being fabricated worldwide. Most of the plants are in 50 to 200 kW capacity range, but large plants of 1 MW and 5 MW have been built. The largest plant operated to date achieved 11 MW of grid quality ac power. Figure 18 depicts the operating configuration of the phosphoric acid cell. Figure 18: Principles of Operation of Phosphoric Acid Fuel Cell. The electrochemical reactions occurring in PAFCs are:

The electrochemical reactions occur on highly dispersed electro-catalyst particles supported on carbon black. Platinum (Pt) or Pt alloys are used as the catalyst at both electrodes. The PAFC have a similar design with the PEMFC. The electrolyte used for PAFC is concentrated phosphoric acid (H3PO4), allowing operation at temperatures higher than the PEMFC (i.e., over 100°C). This electrolyte is contained in a silicon carbide matrix, and catalysts are typically made of Pt.

Cell Components : There have been only minor changes in cell design in recent years. The major U.S. manufacturer, UTC Fuel Cells, has concentrated on improving cell stability and life, and in improving the reliability of system components at reduced cost. Technological advances of the components of this type of fuel cells have been extensively documented over the last 40 years, and a brief summary is presented in Table 2.

Table 2:

PAFC Component Characteristics

Component Ca.1965 Ca.1975 Current status

ANODE PTFE-bonded Pt black PTFE-bonded Pt/C PTFE-bonded Pt/C Vulcan XC-72 Vulcan XC-72 9 mg Pt/cm2 0.25 mg Pt/cm2 0.1 mg Pt/cm2

CATHODE PTFE-bonded Pt black PTFE-bonded Pt/C PTFE-bonded Pt/C

Vulcan XC-72 9 Vulcan XC-72 9

9 mg Pt/cm2 0.5 mg Pt/cm2 0.5 mg Pt/cm2

ELECTRODE SUPPORT TA MESH SCREEN CARBON PAPER CARBON PAPER

ELECTROLYTE SUPPORT GLASS FIBRE PAPER PTFE BONDED SIC PTFE BONDED SIC

ELECTROLYTE 85%H3PO4 95%H3PO4 100%H3PO4

The operating temperatures and acid concentrations of PAFCs have increased to achieve higher cell performance; temperatures of about 200 °C and acid concentrations of 100 % H3PO4 are commonly used today. Although the present practice is to operate at atmospheric pressure, the operating pressure of PAFCs surpassed 8 atm in the 11 MW electric utility demonstration plant, confirming an increase in power plant efficiency. However, a number of issues remain whether to design and operate PAFC units at atmospheric vs. pressurized conditions. Primarily, small, multi-kW PAFC power units that were the focus of initial commercial applications led to atmospheric pressure operation. Although pressurization increased efficiency (lower fuel cost), it complicated the power unit - resulting in higher capital cost. The economic trade-off favored simpler, atmospheric operation for early commercial units. Another important issue, independent of power unit size, is that pressure promotes corrosion. Phosphoric acid electrolyte (H3PO4) produces a vapor. This vapor, which forms over the electrolyte, is corrosive to cell locations other than the active cell area. These cell locations are at a mixed voltage (open circuit and cell voltage), that can be over ~0.8V/cell. That is the limit above which corrosion occurs (active area limited to operation under ~0.8 V/cell). An increase in cell total pressure causes the partial pressure of the H3PO4 vapor to increase, causing increased corrosion in the cell. Cell temperature must also be increased with pressurized conditions to produce steam for the steam reformer. Carbon black and graphite were sufficiently stable to replace the more expensive gold-plated tantalum cell hardware used at the time. The use of high-surface area graphite to support Pt permitted a dramatic reduction in Pt loading without sacrificing electrode performance. It was reported that "without graphite, a reasonably inexpensive acid fuel cell would be impossible, since no other material combines the necessary properties of electronic conductivity, good corrosion resistance, low density, surface properties (especially in high area form) and, above all, low cost". However, carbon corrosion and Pt dissolution become an issue at cell voltages above ~0.8 V. Consequently, low current densities at cell voltage above 0.8 V and hot idle at open circuit potential should be avoided. The porous electrodes contain a mixture of electro-catalyst supported on carbon black and a polymeric binder, usually PTFE (30 to 50 wt %). The PTFE binds the carbon black particles together to form an integral, but porous, structure that is supported on a porous graphite substrate. The graphite structure serves as a support for the electro-catalyst layer, as well as the current collector. A typical graphite structure used in PAFCs has an initial porosity of about 90 %, which is reduced to about 60 % by impregnation with 40 wt % PTFE. This wet-proof graphite structure contains macropores of 3 to 50 μm diameter (median pore diameter of about 12.5 μm) and micropores with a median pore diameter of about 34 ? for gas permeability. The composite structure, consisting of a carbon black/PTFE layer on the graphite substrate, forms a stable, three-phase interface in the fuel cell, with H3PO4 electrolyte on one side (electro-catalyst side) and the reactant gas environment on the other. A bipolar plate separates the individual cells and electrically connects them in series in a fuel cell stack. In some designs, the bipolar plate also contains gas channels that feed the reactant gases to the porous electrodes and remove the reaction products and inerts. Bipolar plates made from graphite resin mixtures that are carbonized at low temperature (~900 °C) are not suitable because of their rapid degradation in PAFC operating environments. However, corrosion stability is improved by heat treatment to 2,700 °C, i.e., the corrosion current is reduced by two orders of magnitude at 0.8 V in 97 % H3PO4 at 190°C and 4.8 atm. The all-graphite bipolar plates are sufficiently corrosion-resistant for a projected life of 40,000 hours in PAFCs, but they are still relatively costly to produce. A typical PAFC stack contains cells connected in series to obtain the practical voltage level desired for the load. In such an arrangement, individual cells are stacked with bipolar plates between the cells. The bipolar plates used in early PAFCs consisted of a single piece of graphite with gas channels machined on either side to direct the flow of fuel and oxidant. Currently, both bipolar plates of the previous design and new designs consisting of several components are being considered. In the multi-component bipolar plates, a thin impervious plate separates the reactant gases in adjacent cells in the stack, and separate porous plates with ribbed channels are used to direct gas flow. In a cell stack, the impervious plate is subdivided into two parts, and each joins one of the porous plates. The electrolyte vaporizes so that a portion of H3PO4 escapes from the cell in the air stream over time. An electrolyte reservoir plate (ERP), made of porous graphite, provides enough electrolyte to achieve a 40,000-hour cell life goal (there is no electrolyte replacement). The ERP also accommodates increases in electrolyte volume due to an increase in H2O, so the porous graphite electrodes don’t flood. These fluctuations in electrolyte volume occur during start-up and during transient operation. The porous structure, which allows rapid ?gas transport, is also used to store additional acid to replenish the supply lost by evaporation during the cell operating life. In PAFC stacks, provisions must be included to remove heat generated during cell operation. In practice, heat has been removed by either liquid (two-phase water or a dielectric fluid) or gas (air) coolants that are routed through cooling channels located (usually about every fifth cell) in the cell stack. Liquid cooling requires complex manifolds and connections, but better heat removal is achieved than with air-cooling. The advantage of gas cooling is its simplicity, reliability, and relatively low cost. However, the size of the cell is limited, and the air-cooling passages must be much larger than the liquid- cooling passages. Development Components Phosphoric acid electrode

FACTS SHEETS OF Phosphoric acid (PAFC)

ELECTROLYTE : Phosphoric acid soaked in a porous matrix or imbibed in a polymer membrane

OPERATING TEMPERATURE : 150°–200°C

TYPICAL STACK SIZE : 5–400 kW, 100 kW module (liquid PAFC) <10 kW (polymer membrane)

ELECTRICAL EFFICIENCY LHV :40%

APPLICATIONS : Distributed generation

ADVANTAGES : Suitable for CHP, Increased tolerance to fuel impurities

CHALLENGES : Expensive catalysts, Long start-up time, Sulfur sensitivity

PHOSPHRIC ACID FUEL CELL : EFFICIENT ENERGY SOLUTION

• Phosphoric Acid Fuel Cells (PAFCs) have a rich history dating back to the 1960s and have evolved significantly over the years.
• Advancements in materials science and engineering have played a pivotal role in enhancing the performance and efficiency of PAFC technology.
• The commercialization of PAFCs gained momentum in the late 1980s, driving their market penetration in various industrial and commercial settings.
• PAFCs offer high power generation efficiency, reaching up to 40%, making them a compelling choice for sustainable energy production.
• Phosphoric Acid Fuel Cells have diverse applications, from power generation in commercial buildings to specialized industrial uses, contributing to the global sustainable energy landscape.

Early Research and Breakthroughs

Phosphoric acid fuel cells (PAFCs) have a rich history dating back to the 1960s when researchers began exploring the potential of this technology for efficient power generation. The breakthrough came in 1967 when G.E. Haddad and A.J. Appleby demonstrated the use of phosphoric acid as an electrolyte in a practical fuel cell system. This early research laid the foundation for the development of PAFCs with significantly enhanced performance and efficiency. Furthermore, in the 1970s, scientists made significant strides in improving the electrode materials, which contributed to the enhanced functionality and stability of PAFCs.

Advancements in Technology

Over the years, advancements in materials science and engineering have played a pivotal role in the evolution of PAFC technology. Innovations in catalyst materials and electrode designs have significantly improved the power output and operational stability of phosphoric acid fuel cells. The integration of advanced manufacturing techniques has further refined the production processes, resulting in more reliable and cost-effective PAFC systems.

Moreover, continuous research and development efforts have led to the optimization of cell stack architecture, thermal management systems, and water handling mechanisms, thereby enhancing the overall efficiency and durability of PAFCs.

Commercialization and Market Penetration

The commercialization of PAFCs gained momentum in the late 1980s, marking a crucial milestone in their development. Companies and institutions began deploying PAFC-based power generation systems in various applications, including commercial buildings, distributed power generation, and utility-scale plants. This period witnessed the widespread adoption of PAFC technology, establishing its position in the energy sector.

Advancements in manufacturing and economies of scale have made PAFCs more cost-competitive, driving market penetration and expanding their use in industrial and commercial settings.

Furthermore, advancements in manufacturing techniques and economies of scale have made PAFCs more cost-competitive, driving their market penetration and expanding their use in diverse industrial and commercial settings.

Current Innovations and Future Prospects

In the present era, the development of PAFCs continues to thrive, with a particular focus on enhancing their environmental footprint and operational flexibility. Ongoing research initiatives are exploring the integration of PAFC technology with renewable energy systems to create hybrid power generation solutions with even lower emissions and higher efficiency.

MECHANISMS AND PRINCIPLES OF OPERATION

Basic Working Principle of Phosphoric Acid Fuel Cells

At the core of phosphoric acid fuel cells (PAFCs) lies a straightforward principle. Hydrogen reacts with oxygen to produce electricity, heat, and water, as part of an electrochemical process . As hydrogen fuel continuously flows into the anode – the fuel cell's positively charged electrode, electrons are released and directed through an external circuit, generating electrical current. Meanwhile, the positively charged hydrogen ions move through the electrolyte to the cathode, the negatively charged electrode, where they combine with oxygen and the electrons to form water. This seamlessly continuous flow of electrons creates a steady source of electricity, delivering a clean and renewable power supply.

PAFCs offer a sustainable and efficient energy conversion method that plays a significant role in the clean energy revolution.

Fundamentally, the ingenious design of PAFCs allows for a sustainable and efficient method of energy conversion, contributing significantly to the clean energy revolution.

Electrochemical Reactions

The electrochemical reactions within PAFCs encompass a series of meticulously orchestrated processes. As the hydrogen molecules split into protons and electrons at the anode, the protons diffuse through the phosphoric acid electrolyte, while the electrons are directed through an external circuit, driving electrical devices. Subsequently, at the cathode, these electrons, protons, and oxygen ions react to produce water, thus completing the circuit. This intricate choreography of electrochemical reactions exemplifies the novel way in which PAFCs harness the power of hydrogen to generate electricity, all while minimizing environmental impact.

An intricate dance of electrons and protons within cells showcases clean and efficient energy generation for sustainable power solutions.

The intricate dance of electrons and protons within the cells paints a picture of clean and efficient energy generation, providing a glimpse into the promise of sustainable power solutions.

Role of Phosphoric Acid as an Electrolyte

Phosphoric acid serves as the vital conduit for the ions and creates the necessary environment for the electrochemical reactions to occur within PAFCs. With its distinct ability to conduct protons, phosphoric acid acts as the bridge between the negatively charged cathode and the positively charged anode. This characteristic makes it an essential element in facilitating the movement of hydrogen ions through the electrochemical cell. Furthermore, its high operational temperature enables efficient energy conversion. The role of phosphoric acid as an electrolyte emphasizes its critical function in the continuous production of clean energy.

Did you know that phosphoric acid fuel cells have an efficiency of around 40-80%, making them one of the most efficient types of fuel cells?

The unique properties of phosphoric acid as an electrolyte stand as a testament to the cutting-edge technology behind PAFCs, showcasing their potential to revolutionize the energy landscape.

Electrodes: Materials and Function

The intricate material designs and functionalities of electrodes in PAFCs enable efficient energy conversion, showcasing their potential as sustainable power sources.

The electrodes within PAFCs encompass intricate material designs and functionalities to ensure the seamless operation of the fuel cells. The anode, typically composed of platinum, facilitates the oxidation of hydrogen molecules, releasing electrons and protons. Conversely, the cathode, often containing platinum or palladium, serves to reduce oxygen and combine it with electrons and protons to generate water. This interplay of materials and functions within the electrodes exemplifies the complex yet efficient energy conversion process integral to PAFCs, underlining their potential as sustainable power sources.

The meticulous construction and functionality of the electrodes underscore the precision and innovation behind PAFCs, illuminating their capacity to drive forward the renewable energy movement.

Power Generation and Output Efficiency

The power generation and output efficiency of PAFCs showcase their remarkable potential for sustainable energy production. With efficiency levels reaching up to 40%, PAFCs offer a compelling alternative to traditional energy sources, providing a higher electrical output for the same input of hydrogen. Additionally, the generation of heat as a byproduct further enhances the overall energy utilization, making PAFCs an attractive choice for combined heat and power applications.This remarkable efficiency coupled with the capacity for cogeneration positions PAFCs as a game-changing technology in the pursuit of sustainable and efficient energy solutions.

PAFCs play a crucial role in advancing towards a cleaner and more sustainable energy future with their impressive power generation and efficiency.

The impressive power generation and exceptional efficiency of PAFCs emphasize their pivotal role in driving the transition towards cleaner and more sustainable energy sources, marking a significant step towards a greener future.

Cell Configuration

The cell configuration of phosphoric acid fuel cells (PAFCs) is crucial for their efficient operation. PAFCs typically consist of two porous electrodes (anode and cathode) separated by a phosphoric acid electrolyte. The cells are arranged in a stack to increase power output. Each cell operates at relatively high temperatures, typically around 150-200 degrees Celsius, to ensure optimal performance.

The design incorporates gas distribution channels for efficient fuel flow and uniform reactant distribution in the fuel cell.

Moreover, the design includes gas distribution channels within the fuel cell to facilitate the flow of hydrogen fuel to the anode and oxygen or air to the cathode, ensuring efficient electrochemical reactions. This careful configuration maximizes the active area for reactions and ensures uniform distribution of reactants across the electrode surfaces.

Materials Used in Construction

The selection of materials for construction plays a critical role in the reliability and longevity of PAFCs. The electrodes are usually made from conductive carbon materials, and the electrolyte matrix is impregnated with phosphoric acid to facilitate ion transport. Components such as bipolar plates and separators are often made from corrosion-resistant materials like graphite or certain metals to withstand the harsh chemical environment and high operating temperatures.

Additionally, the development of advanced materials such as nanocomposites and high-temperature polymers has shown promise in enhancing the durability and performance of PAFC components. These materials contribute to improved conductivity, corrosion resistance, and overall structural stability, thereby enhancing the cell's reliability and longevity.

Cell Stack Architecture

PAFC systems utilize a cell stack architecture with precise compression, thermal management, and series connection for optimal voltage and power output.

The cell stack architecture of PAFC systems consists of multiple individual fuel cells connected in series to achieve the desired voltage and power output. The cells are assembled into a stack with precise compression to ensure intimate contact between the electrodes and current collectors. The stack architecture also incorporates thermal management systems to control temperature gradients and ensure uniform operating conditions across all cells.

This careful arrangement and integration of individual cells into a stack are essential for optimizing the power density and overall performance of the fuel cell system, making it suitable for both stationary and mobile applications.

Thermal and Water Management Systems

Effective thermal and water management systems are essential for PAFCs to maintain optimal operating conditions and prevent performance issues.

Effective thermal management is critical for PAFCs to maintain their operating temperatures within the optimal range. Heat exchangers and coolant systems are integrated into the design to manage the high heat generated during operation and to provide consistent thermal conditions. Additionally, since PAFCs operate at elevated temperatures, water management systems are essential to control the water content within the fuel cell and prevent drying out of the phosphoric acid electrolyte, which can affect performance.

These systems ensure the efficient operation and longevity of the PAFCs by maintaining thermal balance and adequate hydration levels, contributing to their reliability in diverse operating conditions.

Mechanical and Structural Design Considerations

The mechanical and structural design of PAFC systems focuses on ensuring robustness, compactness, and ease of integration. The integration of seals and gaskets within the system is crucial to prevent gas leakage and electrolyte seepage, while also allowing for thermal expansion and contraction during operation. Additionally, the overall design aims to minimize internal resistance and pressure drops to maximize the fuel cell's performance and efficiency.

Furthermore, considerations for ease of maintenance, modularity, and scalability are integrated into the design to facilitate deployment in various applications and to enable future upgrades or replacements of individual components without significant downtime or cost implications.

Applications_and_Uses_of_Phosphoric_Acid_Fuel_Cells style=margin: 0px; padding: 0px; box-sizing: border-box;Applications and Uses of Phosphoric Acid Fuel Cells

Power Generation for Commercial Buildings

In the realm of commercial buildings, Phosphoric Acid Fuel Cells (PAFC) have emerged as a sustainable and efficient power generation solution. Their quiet operation and high reliability make them ideal for facilities where uninterrupted power supply is crucial, such as hospitals and data centers. Moreover, PAFCs offer combined heat and power (CHP) capabilities, enabling simultaneous production of electricity and useful heat, thereby significantly enhancing energy efficiency and reducing overall operating costs.

Furthermore, the deployment of PAFC systems in commercial buildings aligns with sustainability initiatives, contributing to the reduction of greenhouse gas emissions. This aligns with the growing global focus on environmentally-friendly practices, making PAFCs an attractive choice for forward-thinking businesses striving to minimize their carbon footprint.

Integration in the Transportation Sector

Phosphoric Acid Fuel Cells have also carved a niche in the transportation sector. Their high efficiency and low emissions make them a viable alternative to traditional internal combustion engines. With research and development efforts continually improving the performance and durability of PAFCs, they hold tremendous potential for applications in electric vehicles, particularly for heavy-duty transport such as buses and trucks.

Additionally, PAFCs present an appealing solution for reducing dependence on fossil fuels in maritime transportation. Their ability to generate power with minimal environmental impact positions them as a promising technology for powering vessels, contributing to the global drive towards sustainable shipping practices.

Utility-Scale Power Plants

At the utility scale, Phosphoric Acid Fuel Cells demonstrate remarkable utility for power generation. With their proven track record of high reliability and steady performance, PAFC systems are well-suited for large-scale power plants. Their capability to efficiently generate electricity and heat, combined with their low emissions profile, makes them particularly advantageous for catering to the energy demands of urban centers and industrial complexes.

Moreover, the modular nature of PAFC stacks allows for scalability, enabling utility-scale power plants to adapt to varying demands, thereby offering a versatile and sustainable solution for meeting the electricity needs of a rapidly expanding global population.

Residential and Small-Scale Applications

In the realm of residential and small-scale applications, Phosphoric Acid Fuel Cells have gained traction as a reliable decentralized energy generation solution. Their compact size and minimal emissions profile make them well-suited for providing power and heat to individual homes and small businesses. Additionally, their ability to operate in a combined heat and power mode aligns with the growing trend towards distributed energy systems, enabling consumers to efficiently utilize energy resources while reducing strain on traditional power grids.

Moreover, PAFCs offer the added advantage of grid resilience, providing homeowners and small-scale enterprises with a reliable backup power source during grid outages or emergencies, thereby bolstering energy security at the grassroots level.

Specialized Industrial Uses

Beyond the conventional applications, Phosphoric Acid Fuel Cells have found specialized industrial uses across a multitude of sectors. From serving as reliable primary or backup power sources for remote industrial facilities to providing sustainable energy solutions for critical infrastructure such as telecommunications towers and unmanned monitoring stations, PAFCs have proven their versatility and reliability in meeting the distinctive energy needs of various industrial operations. Their capability to operate seamlessly in off-grid locations and harsh environmental conditions positions them as a dependable energy solution for remote and challenging industrial applications.

Additionally, PAFCs serve as a dependable primary or backup power source for critical infrastructure, ensuring uninterrupted operations in scenarios where grid power may not be readily available or reliable, thereby enhancing the resilience and sustainability of industrial operations.

Fuel Cells

Fuel Cell Cars List: Top Models You Need to Know

Fuel Cells

Fuel Cell Companies Pioneering Clean Energy Solutions

Fuel Cells

Hydrogen Fuel Cell Components: What You Need to Know

Environmental_and_Economic_Impact style=margin: 0px; padding: 0px; box-sizing: border-box;Environmental and Economic Impact

Reduction in Greenhouse Gas Emissions

Phosphoric Acid Fuel Cells (PAFCs) play a pivotal role in reducing greenhouse gas emissions. Unlike traditional energy sources like coal or gas, which release significant amounts of carbon dioxide and other pollutants, PAFCs produce electricity with remarkably low emissions. This reduction in greenhouse gas emissions aligns with global efforts to combat climate change and minimize environmental impact.

For instance, a study conducted by the U.S. Department of Energy revealed that PAFCs result in approximately 50% to 100% lower CO2 emissions compared to conventional power plants. This reduction significantly contributes to mitigating the adverse effects of greenhouse gases on the environment.

Comparison to Traditional Energy Sources

In terms of efficiency and environmental impact, PAFCs outshine traditional energy sources. When compared to coal or natural gas power plants, which are notorious for their high emissions and inefficiencies, PAFCs demonstrate superior performance. According to the International Energy Agency, PAFCs boast an electrical efficiency of around 40-42%, surpassing the average efficiency of typical coal and gas plants, which range from 33-40%.

Furthermore, PAFCs offer the advantage of distributed generation, reducing energy losses associated with long-distance electricity transmission. This decentralized approach not only enhances efficiency but also minimizes environmental disturbances often caused by large-scale power infrastructure.

Cost-Benefit Analysis

A comprehensive cost-benefit analysis highlights the economic advantages of deploying PAFCs. Although the initial capital investment for PAFC technology may be higher compared to conventional options, the long-term operational benefits are substantial. Studies indicate that the total cost of ownership over the lifespan of PAFCs is competitive or even superior to traditional power generation systems.

Moreover, the potential for combined heat and power (CHP) applications further amplifies the economic benefits of PAFCs. The utilization of waste heat for heating or cooling purposes increases overall energy efficiency and provides attractive economic returns for commercial and industrial users.

Life Cycle and Sustainability

The life cycle and sustainability aspects of PAFCs are critical in assessing their overall environmental and economic impact. PAFC systems are designed with durability and longevity in mind, offering an extended operating life with proper maintenance. This longevity contributes to reduced material consumption and waste generation over time, aligning with sustainable resource management practices.

Furthermore, the utilization of phosphoric acid as an electrolyte in these fuel cells enhances their sustainability profile. Phosphoric acid, a non-toxic and non-corrosive substance, ensures the environmental compatibility of PAFCs throughout their life cycle. This focus on sustainability resonates with increasing global consciousness regarding the eco-friendliness of energy technologies.

Government Policies and Incentives

Government policies and incentives play a pivotal role in promoting the adoption of PAFCs and other sustainable energy technologies. Various countries across the globe have implemented supportive measures, such as feed-in tariffs, tax credits, and subsidies, to encourage the deployment of clean energy solutions including PAFCs. These initiatives not only facilitate the economic viability of PAFC projects but also drive innovation and technological advancements in the field.

Moreover, the integration of PAFCs aligns with national and international climate targets, allowing governments to fulfill their commitments to reduce carbon emissions and promote sustainable development. The strategic alignment of PAFC technologies with policy frameworks strengthens their position as a vital contributor to the transition towards a low-carbon and sustainable energy future.

PHOSPHORIC ACID FUEL CELL ADVANTAGES AND DISADVANTAGES

At an operating range of 150 to 200?°C, the expelled water can be converted to steam for air and water heating (combined heat and power). This potentially allows efficiency increases of up to 70%. PAFCs are CO2-tolerant and can tolerate a CO concentration of about 1.5%, which broadens the choice of fuels they can use. If gasoline is used, the sulfur must be removed. At lower temperatures phosphoric acid is a poor ionic conductor, and CO poisoning of the platinum electro-catalyst in the anode becomes severe. However, they are much less sensitive to CO than proton-exchange membrane fuel cells (PEMFC) and alkaline fuel cells (AFC).

Disadvantages include rather low power density and chemically aggressive electrolyte.

Applications

PAFC have been used for stationary power generators with output in the 100?kW to 400?kW range and are also finding application in large vehicles such as buses.

Major manufacturers of PAFC technology include Doosan Fuel Cell America Inc. (formerly Clear Edge Power & UTC Power) and Fuji Electric.

India's DRDO has developed PAFC based AIR-INDEPENDENT PROPULSION for integration into their kALVARI-CLASS SUBMARINES.

Phosphoric acid fuel cell

Phosphoric acid fuel cells (PAFC) are a type of fuel cell that uses liquid phosphoric acid as an electrolyte. They were the first fuel cells to be commercialized. Developed in the mid-1960s and field-tested since the 1970s, they have improved significantly in stability, performance, and cost. Such characteristics have made the PAFC a good candidate for early stationary applications.

Electrolyte is highly concentrated or pure liquid phosphoric acid (H3PO4) saturated in a silicon carbide (SiC) matrix. Operating range is about 150 to 210?°C. The electrodes are made of carbon paper coated with a finely dispersed platinum catalyst.

Anode reaction: 2H2(g) → 4H+ + 4e￣

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

Overall cell reaction: 2 H2 + O2 → 2H2O

At an operating range of 150 to 200?°C, the expelled water can be converted to steam for air and water heating (combined heat and power). This potentially allows efficiency increases of up to 70%. PAFCs are CO2-tolerant and can tolerate a CO concentration of about 1.5%, which broadens the choice of fuels they can use. If gasoline is used, the sulfur must be removed. At lower temperatures phosphoric acid is a poor ionic conductor, and CO poisoning of the platinum electro-catalyst in the anode becomes severe. However, they are much less sensitive to CO than proton-exchange membrane fuel cells (PEMFC) and alkaline fuel cells (AFC).

Disadvantages include rather low power density and chemically aggressive electrolyte.[clarification needed]

FREQUENTLY ASKED QUESTIONS

How does a phosphoric acid fuel cell work?

As the name suggests, PAFCs use phosphoric acid as the electrolyte. Positively charged hydrogen ions migrate through the electrolyte from the anode to the cathode. Electrons generated at the anode travel through an external circuit, providing electric power along the way, and return to the cathode.

What is the working principle of fuel cell?

How Fuel Cells Work. Fuel cells work like batteries, but they do not run down or need recharging. They produce electricity and heat as long as fuel is supplied. A fuel cell consists of two electrodes—a negative electrode (or anode) and a positive electrode (or cathode)—sandwiched around an electrolyte.

What is the working principle of PAFC?

The working principle of the PAFC is similar to that of the PEMFC. Hydrogen is used as a fuel and is oxidized at the anode, generating free electrons moving toward the external circuit and the protons moving through the selectively permeable membrane toward the cathode.

What is the working principle of methanol fuel cell?

The water in the fuel cell is oxidized to a hydroxy radical via the following reaction: H2O → OH? + H+ + e?. The hydroxy radical then oxidizes carbon monoxide to produce carbon dioxide, which is released from the surface as a gas: CO + OH? → CO2 + H+ + e?.

What is the function of phosphoric?

Uses. The dominant use of phosphoric acid is for fertilizers, consuming approximately 90% of production. Food-grade phosphoric acid (additive E338) is used to acidify foods and beverages such as various colas and jams, providing a tangy or sour taste. The phosphoric acid also serves as a preservative.

What is the catalyst in phosphoric acid fuel cells?

Phosphoric acid fuel cells (PAFCs) typically work at temperatures of about 200°C, at atmospheric pressure with an electric efficiency of approx. 40%. The electrodes are mainly based on Pt, Fe, or Co as catalyst combined with PTFE, which is set on carbon paper as a support

What is the working equation of fuel cell?

The reaction is: O2 + 4H+ + 4e- → 2H2O. Overall Reaction: The overall reaction in a hydrogen fuel cell is the combination of the anode and cathode reactions, which can be represented as: 2H2 + O2 → 2H2O + electrical energy.

Which electrolyte is used in a fuel cell?

Alkaline fuel cells use an alkaline electrolyte such as potassium hydroxide or an alkaline membrane that conducts hydroxide ions rather than protons.

What is the efficiency of a fuel cell?

A conventional combustion-based power plant typically generates electricity at efficiencies of 33 to 35%, while fuel cell systems can generate electricity at ef- ficiencies up to 60% (and even higher with cogeneration).

What are the applications of PAFC?

PAFC have been used for stationary power generators with output in the 100 kW to 400 kW range and are also finding application in large vehicles such as buses. Major manufacturers of PAFC technology include Doosan Fuel Cell America Inc. (formerly ClearEdge power & UTC Power and Fuji Electric.

What is the full form of PAFC fuel cell?

Phosphoric acid fuel cells (PAFC) are a type of fuel cell that uses liquid phosphoric acid as an electrolyte. They were the first fuel cells to be commercialized. Developed in the mid-1960s and field-tested since the 1970s, they have improved significantly in stability, performance, and cost.

Which is better hydrogen or methanol fuel cell?

Yet one major drawback of using methanal in fuel cells is efficiency. While hydrogen fuel cells can achieve up to 60% efficiency, currently operating direct methanol fuel cells is around 20-30%.

What is the full form of DMFC?

A Direct Methanol Fuel Cell (DMFC) is an electrochemical energy conversion device that converts the chemical energy of methanol fuel directly into electricity, as long as fuel and oxidants are supplied.

What are the disadvantages of DMFC?

The main drawbacks of DMFCs are the slow reaction kinetics (requiring high catalysts loading) and the tendency of the electrolyte to allow a significant cross-over of methanol (bringing about loss of fuel and reduction of cell lifetime), so the electrical efficiency is rather low

What is the pH of phosphoric acid?

1.5

Food-grade phosphoric acid is generally produced by the electric-furnace method. This typically produces a phosphoric acid concentration in the range of 28– 32 percent with a pH of less than 1.5.

What is phosphoric process?

Phosphoric acid, H3PO4, is produced from phosphate rock by wet process or thermal process. 80% of the world's phosphoric acid is obtained by the wet process. The wet process consists of reaction, filtration and concentration steps. The phosphate rock is ground and acidified with sulfuric acid in the reactor vessel.

Is phosphoric acid weak or strong?

weak acid

Phosphoric Acid is a weak acid with the chemical formula H3PO4. Phosphoric Acid is an acid-containing four atoms of oxygen, one atom of phosphorus, and three atoms of hydrogen. It is also known as phosphoric(V) acid or orthophosphoric acid.

What are 5 uses of phosphoric acid?

phosphoric acid, (H3PO4), the most important oxygen acid of phosphorus, used to make phosphate salts for fertilizers. It is also used in dental cements, in the preparation of albumin derivatives, and in the sugar and textile industries. It serves as an acidic, fruitlike flavouring in food products

What is the color of phosphoric acid?

clear colorless

Phosphoric acid appears as a clear colorless liquid or transparent crystalline solid.

Is phosphoric acid soluble in water?

Water

Phosphoric acid / Soluble in

Chemical properties The second method is by burning elemental phosphorous and subsequent hydration of the phosphorous oxide. Phosphoric acid is a corrosive acid that can form three different classes of salts, namely primary phosphates, dibasic phosphates and tribasic phosphates. Phosphoric acid is soluble in water.

Where are phosphoric acid fuel cells used?

Phosphoric acid fuel cells It is one of the most mature cell types and the first to be used commercially. This type of fuel cell is typically used for stationary power generation, but some PAFCs have been used to power large vehicles such as city buses.

How does a methanol fuel cell work?

Methanol and water react electrochemically (the methanol is oxidised) at the anode to form carbon dioxide, protons and electrons. Protons are generated at the anode flow through the polymer electrolyte to the cathode, where they react with oxygen to produce water.

What is the power density of phosphoric acid fuel cell?

The power density of the PAFC is in the range of 0.14 W.cm-2. Although the PAFC used to dominate the demonstration market in the 100 – 200 kW range, it seems to be overtaken by both PEMFC and MCFC systems in this segment. Typical applications are in the industrial and commercial combined heat and power.

Which electrodes are used in a fuel cell?

A fuel cell is similar to electrochemical cells, which consists of a cathode, an anode, and an electrolyte. In these cells, the electrolyte enables the movement of the protons.

What are the advantages of a fuel cell?

The units run longer than lead-acid batteries and can be fueled in as little as three minutes, substantially reducing vehicle and personnel downtime. Additionally, simple maintenance and fewer site visits mean up to 84% lower operational costs when compared to combustion generators for stationary power.

What is the principle of fuel cell?

On the basic level, fuel cells convert chemical energy directly into electrical energy very efficiently through an electrochemical reaction. The principle is rather simple but the design can be complicated

What is the best electrolyte for fuel cells?

Generally, phosphoric acid has been found to be a suitable acid electrolyte for fuel cell applications.

Which fuel cell has the highest efficiency?

So, PEM fuel cells' efficiency comes out a clear winner over internal combustion engines. That said, lithium ion batteries are actually 90% efficient and lead acid batteries produce efficiency comparable to PEM fuel cells at a level of 50%.

What does a galvanic cell convert to?

A galvanic cell is an electrochemical cell which converts the free energy of a chemical process into electrical energy.

How is chemical energy converted to electrical energy in a galvanic cell?

A galvanic cell involves a chemical reaction that makes the electric energy available. During a redox reaction, a galvanic cell uses the energy transfer between electrons to convert chemical energy into electric energy.

How is the chemical energy in a battery converted to electrical energy?

When the electrons move from the cathode to the anode, they increase the chemical potential energy, thus charging the battery; when they move the other direction, they convert this chemical potential energy to electricity in the circuit and discharge the battery.

How do cells convert chemical energy into electrical energy?

i) Electrolytic cell is a device which converts electrical energy into a chemical energy by a process of electrolysis. ii) Electrochemical cell is a device which converts a chemical energy into electrical energy through a redox reaction.

What is the construction of phosphoric acid fuel cell?

Phosphoric acid fuel cells (PAFCs) use phosphoric acid as an electrolyte and an anode and cathode made of a finely dispersed platinum catalyst on a carbon and silicon carbide structure. They have been typically used for stationary power generation in buildings, hotels, hospitals, and utilities in USA, Europe and Asia.2

What are the applications of phosphoric acid fuel cells?

PAFC have been used for stationary power generators with output in the 100 kW to 400 kW range and are also finding application in large vehicles such as buses. Major manufacturers of PAFC technology include Doosan Fuel Cell America Inc. (formerly ClearEdge Power & UTC Power) and Fuji Electric.

What material is used for phosphoric acid pumps?

AxFlow have a number of mag drive and lined pumps suitable for pumping phosphoric acids. While some metals can be used in the construction of phosphoric acid pumps they may have a limited life. The best metals to use would be either 316 stainless steel or Hastelloy.

What are 5 uses of phosphoric acid?

phosphoric acid, (H3PO4), the most important oxygen acid of phosphorus, used to make phosphate salts for fertilizers. It is also used in dental cements, in the preparation of albumin derivatives, and in the sugar and textile industries. It serves as an acidic, fruitlike flavouring in food products.

What is the raw material of phosphoric acid?

Raw materials for the production of phosphoric acid by the thermal process are elemental (yellow) phosphorus, air, and water.

What is a good source of phosphoric acid?

Phosphoric acid can be found in soft drinks (e.g. Coca-Cola), food (e.g. jellies, preserves), animal food (e.g. cat food), some cleaning agents.

Is phosphoric acid flammable?

FIRE HAZARDS Phosphoric Acid is non-combustible but contact with Metals may form flammable Hydrogen gas causing a fire or explosion. Extinguish fire using an agent suitable for type of surrounding fire. * POISONOUS GASES ARE PRODUCED IN FIRE, including Phosphorous Oxides.

Is phosphoric acid harmful to humans?

According to the U.S. Food and Drug Administration (FDA), phosphoric acid is generally regarded as safe (GRAS). However, excessive phosphorus intake can cause harm to your heart, kidneys, and bones.

Who is the biggest producer of phosphoric acid?

China

Fueled by the rapid growth in the Chinese economy and the growing need for phosphate fertilizers, China has become the world's largest producer and consumer of phosphoric acid.

What are the benefits of phosphoric acid?

Phosphoric acid is made from the mineral phosphorus, which is found naturally in many foods. It works with calcium to form strong bones and teeth, according to the National Institutes of Health . It also helps support kidney function and the way your body uses and stores energy.

What is the difference between phosphorus and phosphoric acid?

Phosphoric acid is a mineral (inorganic) acid having the chemical formula H3PO4. Phosphorus(P) is an element and phosphoric acid(H3PO4) is a compound which is acidic in nature

What are 3 interesting facts about phosphoric acid?

Phosphoric acid is used as an acidifying agent to give colas their tangy flavor. Food-grade phosphoric acid is a mass-produced chemical, available cheaply and in large quantities. Phosphorus-containing substances occur naturally (0.1%-0.5%) in foods such as milk, meat, poultry, fish, nuts, and egg yolks.

What is the power density of phosphoric acid fuel cell?

The power density of the PAFC is in the range of 0.14 W.cm-2. Although the PAFC used to dominate the demonstration market in the 100 – 200 kW range, it seems to be overtaken by both PEMFC and MCFC systems in this segment. Typical applications are in the industrial and commercial combined heat and power.

What are the electrolytes in fuel cells?

The electrolyte substance, which usually defines the type of fuel cell, and can be made from a number of substances like potassium hydroxide, salt carbonates, and phosphoric acid. The fuel that is used. The most common fuel is hydrogen.

What are the major requirements for an effective fuel cell catalyst material?

Desirable characteristics of fuel cell electrolytes are not only high ionic conductivity (which results in high efficiency), but also impermeability to gases, negligible electronic conductivity, chemical stability under a wide range of conditions, and good mechanical integrity.

What is the function of the electrolyte in a hydrogen fuel cell?

Every fuel cell also has an electrolyte, which carries electrically charged particles from one electrode to the other, and a catalyst, which speeds the reactions at the electrodes. Hydrogen is the basic fuel, but fuel cells also require oxygen.

What are the requirements of a catalyst?

It must be strong enough to make the catalyst active whereas, not so strong that the reactant molecules get immobilized on the catalytic surface leaving no further space for the new reactants to get adsorbed. Generally for the hydrogenation reaction, from Group 5 to Group 11 metals, the catalytic activity increases.

What is the power density of phosphoric acid fuel cell?

The power density of the PAFC is in the range of 0.14 W.cm-2. Although the PAFC used to dominate the demonstration market in the 100 – 200 kW range, it seems to be overtaken by both PEMFC and MCFC systems in this segment. Typical applications are in the industrial and commercial combined heat and power.

What are the parts of phosphoric acid fuel cell?

Phosphoric acid fuel cells (PAFCs) use an electrolyte composed by concentrated phosphoric acid (H3PO4) dispersed in a silicon carbide matrix. The electrodes are composed by dispersed platinum particles on a porous graphitic substrate

What is the difference between the Fuel cell and batteries?

Batteries make use of metals and their ions or oxides to generate electrical power. Fuel cells require a continuous supply of fuel (considerably hydrogen), and oxygen (from air) to generate electricity. The Fuel cell keeps generating electricity for as long as the fuel is supplied.

What is an alkaline Fuel cell? What is the other name of Alkaline Fuel cell?

Alkaline Fuel cell is the most developed fuel cell technology with an efficiency of about 70%. This Fuel cell uses hydrogen and oxygen to produce potable water, heat and electricity. This cell is also known as Bacon Fuel cell.

Name the different types of Fuel cells.?

There are 6 types of Fuel cells namely:

1. Proton exchange membrane fuel cell (PEMFC)
2. Phosphoric acid fuel cell (PAFC)
3. Solid acid fuel cell
4. Alkaline fuel cell
5. High temperature fuel cell
6. Electric storage fuel cell

What is the relation between activation energy and reaction time?

The activation energy is the minimum amount of energy required for the reactants to undergo a chemical reaction. Hence, the activation energy is significantly related to the rate of the reaction as: the higher the activation energy the slower is the reaction.

What are the major requirements for an electrolyte in a fuel cell?

The major requirements for an electrolyte in a fuel cell are:

1. The electrolyte must have good water uptake even at high temperatures.
2. It must be resistant and very less permeable to reactant gases.
3. The electrolytes used are solids.
4. The electrolyte must be very much pure in order to protect the catalyst from harmful contamination.

What is a Fuel cell charge transport resistance?

The Fuel cells generate electrons which are referred to as “charge transport”. Charge transport is the movement of electrons (or charges) from the electrode to the load or where they are used. The difficulty in transport of these charges is called the Fuel cell charge transport resistance. This resistance results in the voltage loss of the Fuel cell. This voltage-loss is called the ohmic loss.

A Fuel cell is a ___.

Galvanic cell Explanation: Galvanic cells are the electrochemical cells that convert chemical energy into electrical energy.

Write the cell reaction of Bacon Fuel cell.

The fuel cells work on two redox reactions between hydrogen and oxygen. The half-cell reactions of the Bacon fuel cell are given below:

1. At anode, the hydrogen is oxidized producing water and electrons as:
2. H2 + 2OH– → 2H2O + 2e–
3. At cathode, the electrons produced at the anode return via an external circuit. In this half-cell reaction, the oxygen gets reduced by the incoming electrons and hydroxide ions are produced. The cathode-half reaction is:
4. O2 + 2H2O + 2 e– → 4OH–
5. The electricity and heat are produced as the by-products of these reactions.

Discuss the major advantages and disadvantages of fuel cells over other power conversion devices.?

The advantages of the Fuel cells include:

1. They leave no pollution when run on pure hydrogen, only pure water and electricity are the products of the reaction.
2. They have higher thermodynamic efficiency than heat engines.
3. They have higher part-load efficiency i.e. if the powerplant size decreases, these cells do not show a sudden drop in the efficiency.
4. The fuel cell systems do not require combustion of fuels to generate electricity.

The disadvantages of fuel cells are:

1. Pure hydrogen is difficult to manufacture and store.
2. Any contaminants such as sulphur and carbon compounds in the fuel may lead to the deactivation of the fuel cell catalyst and thus making the fuel cell unable to operate.
3. For automotive applications, platinum metal is used as a catalyst. Platinum metal is rare and very expensive.
4. Fuel cells require complex control and support systems..