Fuel cell uses the chemical energy of hydrogen to cleanly and efficiently produce electricity, with water and heat as by products. Fuel cells are unique in terms of the variety of their potential applications; they can provide energy for systems as large as a utility power station and as small as a laptop computer. Fuel cells have several benefits over conventional combustion-based technologies currently used in many power plants and passenger vehicles. They produce much smaller quantities of greenhouse gases and none of the air pollutants that create smog and cause health problems. If pure hydrogen is used as a fuel, fuel cells emit only heat and water as a byproduct.

Polymer electrolyte membrane fuel cells are the current focus of research world over. National Physical Laboratory, New Delhi has developed the know-how for the manufacture of porous conducting paper used in the fuel cell. The complete process is divided into two parts.

A.  The formation of chopped carbon fibre preform mat following the paper making technique

B.  Impregnation of the preform with suitable binder followed by composite making technique.

The major steps to be used in the process are

-    Choice of suitable grade of carbon fibre

-    Selection of appropriate length of the chopped fibres

-    Designing of experimental set up for the uniform dispersion of chopped   carbon fibres  to make porous carbon fibre preform

-    Impregnation of preform with thermosat resin

-    Curing of the resin under specific conditions

-    Carbonization  and  Graphitization of the green perform 

SPECIFICATIONS OF THE POROUS CONDUCTING CARBON PAPER SAMPLE

THICKNESS                                                                      0.26-0.35 (mm)
BULK DENSITY                                                                  0.5 (gm/cm³)
POROSITY                                                                        >70 (%)
GAS PERMEABILITY                                                            30 (mm²/mm)
ELECTRICAL RESISTIVITY THROUGH PLANE                             0.05, ( W cm)
IN PLANE                                                                          0.005 (W  cm)
FLEXURAL STRENGTH                                                          40 MPa
FINAL SIZE                                                                       40 X 40 x 0.03 cm3

CHARACTERIZATION:

Following scheme of characterization of the samples is followed/proposed during different stages of processing

PHYSICAL PROPERTIES: Fibre/matrix volume fraction, Vf, / Vm, Density, Porosity, Gas permeability, electrical resistivity) 

MECHANICAL PROPERTIES :  Flexural Strength, Flexural  Modulus

THERMAL PROPERTIES:

Thermal conductivity, Coefficient of thermal expansion, Specific heat etc.

Moulding of the preform with resin matrix

The carbon fibre preform is impregnated with calculated amount of phenolic resin and moulded into sheet in the special dies between the platens of the hydraulic press. The curing cycle was followed as recommended by manufacturer and further evaluated by a presssure of about 50 Kg/cm2 was maintained during the curing cycle as recommended by manufacturer and further evaluated by DSC.

Carbonization and graphitization

The green samples are heat treated to  a maximum temperature of 2500°C in the graphitization furnace and again characterized for various parameters as specified.

Techno-economics of the plant:

Capacity: 3000 sheets per year of size 400mm x400mm x 0.3mm  per year ( 300 working days)

Land required for plant and buildings: 15m x15 m Shed

Raw Material

High Modulus carbon, Resin and chemicals

Equipment for commercial plant

Hydraulic Press, Paper making plant