Different Types of Fuel Cells And Its Working Principle

Various types of fuel cells have been introduced by the scientists. Some are discussed below.

Alkali Fuel Cells
Alkali fuel cells perform on condensed or compressed oxygen and hydrogen. Using electrolyte is the ordinary solution of potassium hydroxide in water. It shows the efficiency about seventy percent and operating temperature inside these are approximate 150 to 200 degree centigrade. The output ranges of these cells vary from 300 watts to 5 kilowatts.

Electrolyte allows the hydroxyl ions migrating from cathode to anode. Hydrogen gases are supplied externally into anode where hydroxyl ions react with the hydrogen gases to generate electrons and water. These generated electrons are circulated from anode to cathode with an external circuit. The migrated electrons react with the oxygen and water to produce hydroxyl ions which are also again migrated from cathode to anode permitted by the electrolyte.

The alkali fuel cells have been considered as the logical choice of spacecraft because they produce water in addition to generate electricity. Requirement of pure hydrogen and few unwanted chemical reactions are the major drawbacks. In order to increase the reaction time, it needs large amount of platinum catalysts which are very costly. Scientists are working hard to reduce the necessary of large amount expensive platinum catalysts in order to make the system cost efficient.

The proton exchange membrane fuel cell

It has been mainly developed to end up powering buses, cars, is now considered as a promising technique to generate power in this field. It uses a polymer electrolyte in the form of permeable sheet. Platinum is used as a catalyst on the anode in quest to split the hydrogen into positive ions and negative electrons. The hydrogen ions pass through the electrolyte membrane from anode to cathode. And the negative electrons are circulated through an external circuit with creating electricity. And eventually electrons will rejoin with positive ions and oxygen to create water. As the operating temperature varying from 20 to 100 degree centigrade, the efficiency has been calculated 40 to 50 percent. And 50 to 250 Kilowatt is the range of general performance. In order to minimize the anti reaction of carbon monoxide, and efficient gas purification system has to be installed. Otherwise, carbon monoxide will react with platinum catalysts.

Phosphoric Acid Fuel Cell

The working principle of this type of fuel cell is exactly similar as the proton exchange membrane fuel cell apart from this uses phosphoric acid as electrolyte instead of polymer electrolyte. The efficiency range is 40 to 80 percent depending upon the application and the range of the operating temperature is 150 to 200 degree centigrade. It shows the output up to 200kilowatt. And 11 megawatt units have been installed for testing. The major advantage of using this is that it can tolerate a concentration of carbon monoxide. The chemical reactions are exactly same as the proton exchange membrane.

Molten Carbonate Fuel Cell

These types of fuel cell have been developed for various kinds of electrical utility, military and industrial application. It uses salt carbonate as the electrolyte which is basically high temperature compound. Around 650 degree centigrade is the operating temperature and the range of efficiency is the 60 to 40 percent. The practical output units have been constructed up to 2 megawatt and the designs have been constructed in lab up to 100 megawatt so far.

It consists of molten carbonate electrolyte which is placed in the middle of anode and cathode. When hydrogen reaches the anode, it split into proton and electron due to the encouragement of the catalysts. The membrane doesn't allow driving the electrons. The electron will divert through an external circuit to cathode and generate electricity. When electron reaches the cathode, it combines with the oxygen and carbon dioxide and forms carbonate molecule. Carbonate will pass through the membrane to the anode where again combines with the proton. Eventually they generate high temperature which is the offspring and probably major drawback of this reaction.

Solid Oxide Fuel Cell

It uses solid ceramic materials for electrolyte. The reformed cells attack the oxygen ions from the cathode when these cross the anode. The oxygen ions react with fuel for generating electricity, water and small amount of carbon dioxide. The efficiency and the output range are respectively 60 percent and 100 kilowatt. Despite it has the high operating temperature around 1000 degree centigrade, it is easier to handle with comparison to all others.

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