the use of ethanol and fuel cells in cars
...ethanol is currently graded into two types of commercially sold fuel. E85 is used for spark ignition engines and E95 is used for compression engines. E85 consists of 85% ethanol and 15% Gasoline. E95 consists of 95% ethanol and 5% petrol. In E85 the petrol is added to help the engine warm up to allow the ethanol to vaporize. The petrol in E95 is used to lower the ignition point in the compression engine. In comparison to Premium Un-Leaded Petrol (PULP), ethanol has 165% of the CO2 emissions, but of the emissions 85% of the carbon is classed as a renewable resource. CO Emissions are also slightly higher but all of this is a renewable resource. The energy produced is 10% less than PULP. E95 has an octane of roughly 105 octanes; PULP is 89-91 octanes. This means that the fuel needs more compression before it spontaneously combusts, saving the engine from firing before top dead centre is reached. This also means that the fuel is less volatile. The formula for the combustion of ethanol is: C2H5OH (l) + 3O2 (g) 2CO2 (g) + 3H2O (g) Currently there is a group of cars, which are classified as FFV’s or Flexible Fuel Vehicles. These vehicles are specially designed to run on any ethanol fuel blend from 0% to 85% ethanol. The car has a diagnostics unit, which is used to detect the levels of ethanol and petrol in the fuel. The Fuel sensor adjusts the fuel injection system and ignition/spark timings suited to what blend of ethanol is being used. The other parts of the car, eg tank and fuel lines, have to be changed slightly because ethanol is an alcohol which is extremely corrosive. The problem with ethanol is that it does not have the same energy content as petrol. The FFV vehicles are not optimized to E85, and they experience a 15% energy drop. Also not all of the ethanol is burnt, and some of this is expelled into the atmosphere. The fuel economy is also strongly affected by the temperature and conditions, which are being driven in. A fuel cell is very similar to a galvanic cell as a redox reaction occurs, and the electrons are diverted to generate electricity. The half reactions are 2H2 => 4H+ + 4e- and O2 + 4H+ + 4e- => 2H2O. The full reaction is 2H2 + O2 => 2H2O. This type of fuel cell is called a Proton Exchange Membrane Fuel Cell (PEMFC). The fuel cell is broken into four main parts, the anode, the cathode, the catalyst and the proton exchange membrane. The anode has the purpose of oxidising the hydrogen and passing the electrons through the circuit and also to disperse the hydrogen about the catalyst. The catalyst is a carbon paper or cloth that has been dusted with platinum powder. The Proton Exchange Membrane (PEM) is made of a material similar to glad wrap (polyethylene) which is designed to only let protons through and not electrons. When the protons are through the other side of the PEM and catalyst they are mixed with oxygen and draws the electrons through the external circuit. The reformed hydrogen and oxygen are joined to form water (H2O). This cycle continues and continues to create power. The problem is that the amount of power generated is roughly equivalent to .7 Volts which is nowhere near enough energy to power a car. So the fuel cells have to ...