Method of propulsion of car :Fuel Cell: A fuel cell is a device that uses chemicals to create electricity. You can think of a fuel cell as a battery, which is a device that converts chemical energy to electric energy but there are two major differences1. A fuel cell converts reacting chemicals while a battery doesn’t.2. Also the fuel cell doesn’t use up the electrodes(or metal conductors inside them but the battery does ).This means the fuel cell can be used for a longer period of time than the battery, as long as the chemicals it uses are available.
Hydrogen Fuel Cell : It basically converts hydrogen and oxygen into electricity and water, and vice versa. It is called a reversible PEM fuel cell. The abbreviation PEM refers to the membrane that separates the hydrogen and the oxygen sides. PEM stands for proton exchange membrane. A thin foil made of special polymers serves as a membrane in the fuel cell and is located in the membrane electrode assembly in the center of the fuel cell. Reversible means that all processes can run in both directions. In other words, the cell can operate as both a fuel cell to produce electricity and water, or as an electrolysis device to split water into hydrogen and oxygen. In addition to the PEM, the MEA contains two electrodes on either side of the PEM. The MEA is sandwiched together with protective film, metal plates rubber gaskets in a clear plastic housing and head tightly together with four bolts.
The two electrodes the cathode and the anode. The hydrogen side is the anode and the oxygen side is the cathode. On the anode, electrically neutral hydrogen molecules which come from the hydrogen tank split into hydrogen ions and electrons with the help of a catalyst. The positively charged hydrogen ions travel through the polymer membrane towards the negatively charged cathode, while electrons travel through the circuit with an electrical load ( motor ) from anode to cathode. These hydrogen ions or protons are small enough to pass through the membranes small holes but larger oxygen ions cannot. The metal plates in the fuel cell conduct electrons from the anode through the circuit to the cathode. On the cathode the hydrogen ions react with the oxygen molecules that come from the oxygen tank and the electrons from the circuit to form water.
While it is necessary to put energy in splitting of water molecules during electrolysis, now energy is released upon recombination of the ions. In this way, an electrical voltage is produced across the fuel cell. If you connect an electric load ( motor in our case) to anode and cathode the electric current flows and motor runs. Since the conversion of hydrogen and oxygen takes place catalytically. The electrodes themselves do not change in the chemical reaction. The combustion is said to be “cold” as there are no flames involved. Nevertheless some heat is generated and one can feel the warming up of cell. Chemically the following reaction occurs :Cathode : O2 + 4H+ + 4e- 2H2OAnode: 2H2 4H+ + 4e-Overall Reaction : 2H2+O2H2O
Water is filled in the storage tank located towards the back of the car with the fuel cell in the center and themotor at the front. First the fuel cell is connected to a battery or a solar panel to produce hydrogen and oxygenby electrolysis of water and stored in the containers located in the storage tank which are connected with thepipe. Now this we disconnect the battery and connect the motor to the fuel cell to produce power which runs thecar .
The stopping mechanism for the car is to estimate the amount of fuel needed. Severe testing of the car was carried out at various possible conditions and the data was plotted in excel and regressed to obtain equations from the graph. So by varying the amount of charge supplied for splitting of water to the amount of distance the car would travel was obtained. And this was repeated with different amount of mass on the car. In the following slides you can see the various curves obtained in MS excel for different cases.
Everyone has heard about global warming, the greenhouse effect, environmental pollution, smog. Many people are concerned about the climatic changes and the toxic emissions into the air we breath. We know that these effects are a result of our own human activities. Many people are engaged in discussions of mitigating these negative impacts in the future. Several ideas for vehicular traffic and energy production have been proposed. Today many scientist and engineers are turning these ideas into reality. Fuel cells are thought of as an alternative source of energy. Hydrogen fuel cells are very clean with no toxic emissions and very efficient. The only by product is water . But fuel cells don’t generate energy out of nothing. They use hydrogen and hydrogen is an excellent carrier of energy. Hydrogen is non toxic, renewable and easily obtainable. When it combusts with oxygen water is formed. This water can again be split into hydrogen and oxygen and this process can be repeated limitlessly without any emissions. With fuel cells you can very efficiently convert hydrogen into current. Fossil fuels are converted into usable energy through combustion. The energy released is inherently difficult to capture and inefficient . It also produces carbon dioxide which cannot be converted into usable fuel. A fossil fuel engine in power plant is only about 30 – 40 % efficient. Engines in car are even less efficient 15-20 % on the other hand fuel cells operate at 40-65% efficiency. Experts even predict that with the efficiencies upto 75% are possible in the near future.
Efficiency = operating voltage/electrolysis voltage =.95v /1.6v=.59 =59%
1. Conceptually replacing oil based infrastructure with hydrogen would cost a large amount of money.2. Although hydrogen is abundant in the atmosphere, it still has to be extracted (in our case electrolysis ) , currently the process is cost prohibitive .3. Storage of hydrogen onboard , gas can escape and may be undetectable and it readily explodes.
Some Hydrogen fuel cell cars developed by Mercedes, Honda, BMW andGM