Skip to main content

Fuel Cells And Working of Fuel Cells

Fuel Cells are receiving prominent attention as clean, efficient and affordable alternative energy technologies for the future. A fuel Cell is the direct energy conversion device in which fuel and a oxidizer undergo a controlled chemical reaction, producing products and supplying electrical current directly to an external circuit. The fuel and oxidizer react in stages on two separate electrodes , a positive electrode called cathode, and a negative electrode called anode. The two electrodes are separated by an electrolyte. The rates of reaction are limited by the time it takes for diffusion of chemical species through the electrodes and the electrolyte and by the reaction kinetics. 



Fuel cells are of various kinds. The fuel is hydrogen, which diffuses through the porous anode and reacts on the anode surface with OH- ions, forming water and yielding free electrons, according to 

H2 + 2OH-  --------->  2H2O + 2e-

The electrons flow into the external circuit, and water passes on to the electrolyte. On the cathode surface, oxygen fed into the cell combines with water from the electrolyte and electrons from the external circuit to produce OH- ions and water according to 

(1 / 2)O2 + 2H2O + 2e- ------> 2(OH)-  + H2O 

The electrolyte separating the electrodes transports the OH- ions, completing , the circuit, and the water (products) is removed from the cell. The overall reaction is 

H2 + (1 / 2) O2 -----------> H2O 

which is same as the equation for the highly exothermic combustion reaction.

How ever is fuel cell, only a relatively small amount of heat transfer between the call and its surroundings takes place, and the temperature rise is also relatively much smaller.

Energy is removed from fuel cell as electrical energy, whereas energy is removed from a combustion reaction as heat or as heat and work together. Because the fuel cell operates almost isothermally and continuously , the extent to its conversion of chemical energy to electrical energy is not limited by second law of thermodynamics.

the fuel efficiency is defined as, 

E = Delta G / Delta H 

which can be less than , equal to, or greater than unity. the work done in a fuel cell can be written as,

W max = FnjV


Labels:

Comments

Post a Comment

Popular posts from this blog

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR :  The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve.  The float chamber is ventilated to atmosphere.  This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet  manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves.  One is to allow air into the mixing chamber known as choke valve. The other is to al...
Post a Comment
Read more

MELTING FURNACES FOR FERROUS METALS : CUPOLA AND ITS WORKING

Various types of melting furnaces are used in different foundry shops, depending upon the quantity of metal to be melted at a time, and the nature of work that is carried out in the shop.  The primary objective in cupola is to produce iron of desired composition, temperature and properties at the required rate in the most economical manner. Besides, this furnace has many distinct advantages over the other types, e.g., simplicity of operation, continuity of production, and increased output coupled with a high degree of efficiency.  Description Of a Cupola : The Cupola Furnace consists of a vertical, cylindrical steel sheet, 6 to 12 mm thick, and lined inside with acid refractory bricks or acid tamping clay. The refractory bricks or the tamping clay used consist of  silicon oxide acid (SiO2) and alumina (Al2O3). The lining is generally thicker in the lower where the temperatures encountered are higher than in the upper region. The shell is mounted either on a brick work fo...
Post a Comment
Read more

Advantages And Disadvantages Of Air Refrigeration System :

 Advantages Of  Air Refrigeration : 1. The refrigerant used namely air is cheap and easily available. 2. There is no danger of fire or toxic effects due to leakages. 3. The weight to ton of refrigeration ratio is less as compared to other systems. Disadvantages Of Air Refrigeration : 1. The quantity of  Refrigerant used per ton of refrigeration is high as compared to other systems. 2. The COP of the system is very low. Therefore running cost is high. 3. The danger of frosting at the expander valves is more as the air contains moisture content. 
Post a Comment
Read more