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ABSTRACT
To keep pace with ever increasing demand of electrical energy in world, coal based Power plants may not be sufficient .Also the generation of power by coal based power plants or nuclear plants causes pollution .The recent severe crisis has forced the world to develop new and alternative methods of power generation by using renewable sources of energy ,which could not have been adopted due to various reasons till now. The various other renewable sources of energy are solar cells ,fuel cells ,thermo-electric generator ,tidal power ,wind power, geo-thermal, bio-gas. This paper is an attempt to throw some light on the “CONCEPT OF FUEL CELLS .AND APPLICATIONS “. This paper spans over the various topics such as what is a fuel cell, Which tells about the basic function of fuel cell, about the evolution of fuel cell which deals about the origin of fuel cells , The latest developments of fuel cells , Applications of fuel cells in various fields, Sources of procuring hydrogen required for fuel cell ,Fuel cell benefits and obstacles and finally about conclusion . INTRODUCTION
Where as the 19th Century was the century of the steam engine and the 20th Century was the century of the internal combustion engine, it is likely that the 21st Century will be the century of the fuel cell. Fuel cells are now on the verge of being introduced commercially, revolutionizing the way we presently produce power. Fuel cells use hydrogen as a fuel, offering the prospect of supplying the world with clean, sustainable electrical power.
1. WHAT IS A FUEL CELL?
A fuel cell by definition is an electrical cell. They convert hydrogen, or hydrogen-containing fuels, directly into electrical energy plus heat through the electrochemical reaction of hydrogen and oxygen into water. The process is that of electrolysis in reverse.Overall reaction: 2 H2 (gas) + O2(gas) 2 H2O + energy Because hydrogen and oxygen gases are electrochemically converted into water, fuelcells have many advantages over heat engines. These include: high efficiency, virtuallysilent operation .
2. HISTORY OF FUEL CELLS
2.1 The “Gas Battery”
Sir William Grove (1811-96), a British lawyer and amateur scientist developed the firstfuel cell in 1839. When Sir William disconnected the battery from the electrolyzer andconnected the two electrodes together, he observed a current flowing in the oppositedirection, consuming the gases of hydrogen and oxygen (Fig.1). He called this device a‘gas battery’. His gas battery consisted of platinum electrodes placed in test tubes ofhydrogen and oxygen, immersed in a bath of dilute sulphuric acid. It generated voltagesof about one volt. . However, due to problems of corrosion of the electrodes and instability of the materials there was little research and further development of fuel cells for many years to follow.
3. FUEL CELL APPLICATIONS
3.1 Fuel cells for NASA
For space applications, fuel cells have the advantage over conventional batteries, in thatthey produce several times as much energy per equivalent unit of weight.In the1960s, International Fuel Cells developed a fuel cell power plant for the Apollo spacecraft. providing 1.5 KW of continuous electrical power and drinking water , without a single in- flight incident (IFC).In the 1970s, International Fuel Cells developed a more powerful alkaline fuel cell forNASA’s Space Shuttle Orbiter. The Orbiter uses three fuel cell power plants tosupply all of the electrical needs during flight. . Each fuel cell is capable of supplying 12 kilowatts continuously , and up to 16 kilowatts for short periods. In the Shuttle program, the fuel cells have demonstrated outstanding reliability (over 99% availability).
3.2 ALKALINE FUEL CELLS FOR TERRESTRIAL APPLICATIONS
.Compared with other types of fuel cells, the alkaline variety offered the advantage of ahigh power to weight ratio. Therefore alkaline fuel cells were ideal for space applications. However, for terrestrial use, the primary disadvantage of these cells is that of carbon dioxide poisoning of the electrolyte. This reduces the overall efficiency of the fuel cell. The eq is as shown: 2 KOH + CO2 K2CO3 + H2O Because of the complexity of isolating carbon dioxide from the alkaline electrolyte, most fuel cell developers have focused their attention on developing new types which are non-alkaline. These fuel cells include: solid oxide fuel cells (SOFC), phosphoric acid fuel cells (PAFC)
3.3 FUEL CELLS IN TRANSPORTATION
The NECAR 5 is the latest prototype fuel cell automobile by DaimlerChrysler.This automobile is fuelled with liquid methanol which is converted into hydrogen andcarbon dioxide through use of an onboard fuel processor. The vehicle has virtually nopollutant The efficiency of a fuel cell engine is about a factor of two higher than that of an internal combustion engine .The NECAR 5 drives and feels like a “normal” car. It has a top speed of over 150 km/hr(90 mph), with a power output of 75 kW (100 horsepower). It is also believed that thisvehicle will require less maintenance , has low emission levels , quietness , smoothness , while delivering a performance similar to that of an automobile with an internal combustion engine.There are also plans for buses and trucks all powered with fuel cell engines. In 2000,Ballard completed a two-year program of in-service field testing with six fuel cell buses,. The results of the tests were exemplary – the six buses travelled almost 75,000 miles andcarried over 200,000 passengers. The resulting data will be used to further develop a commercialfuel cell bus.
3.4 DISTRIBUTED POWER GENERATION
Electrical energy demands throughout the world are continuing to increase .Now how can these energy demands be met responsibly and safely? Distributed power plants using fuel cells can provide part of the solution Distributed or “decentralized” power plants, are plants located close to the consumer, with the capability of providing both heat and electrical power (a combination known as “cogeneration”). Heat, the by-product of electrical power generation, is transferred from the fuel cell to a heat exchanger. The exchanger transfers the heat to a water supply, providing hot water to local customers. The overall efficiency of a cogeneration system can be in excess of 80 percent, comparatively high compared to a system producing electricity alone. An increase in efficiency naturally corresponds to a decrease in fuel consumption. Distributed power plants have many additional advantages such as providing power to a remote location without the need of transporting electricity through transmission lines from a central plant , ability to quickly build up a power infrastructure . Using fuel cell power plants obviates the need for an electrical grid.
3.4.1 Grid-connect applications
Distributed power plants can provide either primary or back-up power. In primaryapplications they can provide base-load power, operating virtually continuously from theconsumption of natural gas, reducing the demand from the electrical grid. Should the power plant provide an excess of electricity, the excess can be fed back into the electrical grid, resulting in additional savings. Distributed power plant can supply power continuously eliminating the need for UPS
3.4.2 Non-grid connect applications
Other applications for fuel cell distributed power plants are also possible e.g. stand-aloneback-up power generators. The PEM fuel cell plant can be started in seconds, supplyingpower for as long as required from stored hydrogen, producing electrical power cleanlyand virtually silently. Shown in figure is a prototype fuel cell distributed power plant, by Ballard Power .Systems. This unit provides 250 kilowatts of electricity and an equivalent amount of heat. This is enough power for a community of about 50 homes, or a small hospital or a remote school.
3.5 FUEL CELL AS RESIDENTIAL POWER
Fuel cell power plants are also being developed by several manufacturers to provideelectricity and heat to single- family homes. These are fuelled by either natural gas or propane. Plug Power, based in Latham New York has developed a new fuel cell power plant that supplies 5 kilowatts of electricity plus heat, using natural gas as a fuel .Initially these fuel cell power plants will be operated in parallel with the grid. Eventually they will be able to operate either grid parallel or grid independent Plug Power is presently installing and testing these units in selected sites throughout North America, Europe and Japan