fuel cells and its types

Shroff S.R. Rotary Institue of Chemical Technology (SRICT)

• Name- RAJ PAREKH• Branch- MECHANICAL,SEM-1 • Enrollment no-140990119029• Topic- Introduction to fuel cells

What is a Fuel Cell ?· Fuel and air react when they come into contact through a porous membrane (electrolyte) which

separates them.· This reaction results in a transfer of electrons and ions across the

electrolyte from the anode to the cathode. · If an external load is attached to this arrangement, a complete circuit is

formed and a voltage is generated from the

flow of electrical current.

The voltage generated by a single cell is typically rather small (< 1 volt), so manycells are connected in series to create a useful voltage.

A Fuel Cell Converts Chemical Energy to Electrical Energy

Fuel

Hydrogen

Air or Oxygen

Load

Anode CathodeElectrolyte

e-

Catalyst Catalyst

H+

Gas Diffusion Layer

Gas Diffusion Layer

Some History…..

Fuel cell principle first discoveredby William Grove in 1839.

Grove used four large cells, eachcontaining hydrogen and oxygen,to produce electric power which wasthen used to split the water in thesmaller upper cell.

Composition of Fuel CellAnodeCathodeElectrolyte Catalyst

• About Anode− Negative post of the fuel cell. − Conducts the electrons that are freed from the

hydrogen molecules so that they can be used in an external circuit.

− Etched channels disperse hydrogen gas over the surface of catalyst.

• About Cathode− Positive post of the fuel cell− Etched channels distribute oxygen to the surface of

the catalyst.− Conducts electrons back from the external circuit to

the catalyst− Recombine with the hydrogen ions and oxygen to form

water. • About Electrolyte

− Proton exchange membrane.− Specially treated material, only conducts positively

charged ions.− Membrane blocks electrons.

• About Catalyst − Special material that facilitates reaction of oxygen and

hydrogen− Rough & porous maximizes surface area exposed to

hydrogen or oxygen

Working of Fuel Cells• The Fuel gas (hydrogen rich) is passed towards the

anode where the following oxidation reaction occurs:• H2 (g) = 2H+ + 2e-• The liberated electrons from hydrogen in anode side

do not migrate through electrolyte.• Therefore, they passes through the external circuit

where work is performed, then finally goes into the cathode.

• On the other hand, the positive hydrogen ions (H+) migrate across the electrolyte towards the cathode.

• At the cathode side the hydrogen atom reacts with oxygen gas (from air) and electrons to form water as byproduct according to:

• The overall cell reaction is

H2 + 1/2 O2 +2e - H2O + Heat

fuel + oxidant product + Heat

Working of Fuel Cell

Electrical power production by fuel cell

Rotating shaft connected to generator for electricity production

Fuel CellType Electrolyte Anode Gas Cathode Gas Temperature Efficiency

Proton Exchange Membrane(PEM) solid polymer membrane hydrogen pure or atmospheric oxygen 75°C

(180°F) 35–60%

Alkaline(AFC) potassium hydroxide hydrogen pure

oxygenbelow80°C 50–70%

Direct Methanol(DMFC) solid polymer membrane methanol solution in water atmospheric

oxygen75°C

(180°F) 35–40%

Phosphoric Acid(PAFC) Phosphoric Acid hydrogen atmospheric

oxygen210°C

(400°F) 35–50%

Molten Carbonate(MCFC)

Alkali-Carbonates

hydrogen,methane

atmosphericoxygen

650°C(1200°F) 40–55%

Solid Oxide(SOFC) Ceramic Oxide hydrogen,

methaneatmospheric

oxygen800–1000°C

(1500–1800°F) 45–60%

Advantages/Disadvantages of Fuel Cells

• Advantages− Water is the only discharge (pure H2)

• Disadvantages− CO2 discharged with methanol reform− Little more efficient than alternatives− Technology currently expensive

• Many design issues still in progress− Hydrogen often created using “dirty”

energy (e.g., coal)− Pure hydrogen is difficult to handle

• Refilling stations, storage tanks, …

Each type of fuel cell is particularly suited to certain applications:

• PEM: most versatile, used for portable power, transportation, and stationary power

• DMFC: used for portable power• SOFC: primarily used for stationary power, in

development for transportation (e.g. semi trucks)

• MCFC: power plants • AFC: power and water production for space

vehicles (e.g. Apollo and Space Shuttle spacecrafts), in development for more general use

• PAFC: stationary power, power plants

Galvanic cell (battery)Hydrogen fuel cell

· Open system· Anode and cathode are gases in contact with a platinum catalyst.·Reactants are externally supplied, no recharging required.

· Closed system· Anode and cathode are metals.· Reactants are internally consumed, need periodic recharging.

Fuel Cell Vs. Battery

Basic operating principles of both are very similar, but there are severalintrinsic differences.

Fuel Cells in Use: Stationary Systems

Fuel Cells in Use: Stationary Systems

Fuel cell system for submarine

Fuel Cells in Use: Transportation Systems

XCELLSiS fuel cell bus prototypes

Buses are most commerciallyadvanced applications of fuelcells to date.

Are currently being used by many American and Europeancities.

Fuel Cells in Use: Transportation Systems

Many of the major car companies are developing fuel cell car prototypeswhich should come to market during the next decade. The cars use eitherpure hydrogen or methanol with an on board reformer.

Power distribution application

• Fuel cells can be used for the distribution of power in various fields such as,

• Homes and small businesses

• Commercial and industrial sites

• Remote, off-grid locations (telecom towers,

weather stations)

SOLAR FUEL CELLS ?

THANK YOU