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Optimization of a Chem-E-Car New Jersey Governor’S School of Engineering and Technology 2014

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Optimization of a Chem-E-Car New Jersey Governor’S School of Engineering and Technology 2014 Optimization of a Chem-E-Car New Jersey Governor’s School of Engineering and Technology 2014 Michael Amoako David Fan Wendy Ide [email protected] [email protected] [email protected] Teaneck High School Montgomery High School High Technology HS Nina Lin Marcus Loo [email protected] [email protected] Lenape High School Park Ridge High School Abstract Introduction In light of the recent movement towards The need for affordable and efficient reducing fossil fuel consumption, the need alternative energy sources is a defining issue for a suitable alternative energy source is of the twenty-first century that is receiving greater than ever. To explore the utility of growing attention from both the scientific household products as unconventional yet community and the public alike. While efficient energy sources, a car powered hydrocarbons have driven a majority of the entirely by chemical reactions was built. world’s energy consumption for over a Fuel cell batteries of varying salinity, pH, century, such sources are both unsustainable and designs were built and tested while a and environmentally detrimental. If the stopping mechanism was calibrated. A world’s energy needs continue to grow at shoebox-sized car was then built with both their current rate, fossil fuel reserves are the battery and stopping mechanism estimated to deplete by 2052, followed by implemented and tested at various distances natural gas by 2060 and coal by 2088.1 The and loads. It was found that increasing consequences of using these energy sources salinity increased battery current but did not to the end will be unprecedented, both for affect the voltage, while increasing and the environment and the global economy. decreasing pH both increased current and Thus, it is clear that the world needs to find voltage. The iodine clock reaction was also a feasible alternative. found to follow a first-order law, with a While substantial advances in reaction time linearly proportional to the alternative energy have recently been made concentration of iodine. Ultimately, the car in the automobile industry, current was able to stop at each intended distance alternative energy sources for powering through the iodine clock reaction. Although vehicles are either expensive or not widely the aluminum batteries and iodine clock accessible to all. Ethanol fuels, for example, were implemented to power only a shoebox are not practical because they provide low sized car, the scale-up of similar, widely mileage per gallon and require a large available materials could possibly mean a amount of organic material and land to future of globally accessible transportation. produce, land that is increasingly difficult to provide.2 Currently, hydrogen fuel cars are . very expensive and often require high 1 running temperatures, reducing their the cathode half-cell is the site of reduction, longevity and efficacy. In addition, and both are connected by a salt bridge. The hydrogen fuel is difficult to safely transport salt bridge contains an electrolyte or for mass distribution because it needs to be aqueous solution of ions, which flow freely compressed and purified.2 Because of the between the anode and cathode to maintain public’s inaccessibility to many “green” charge neutrality in each. Without the salt technologies, the future depends on bridge, the cathode would become developing a less demanding way to progressively more negative as it gains encourage the use of alternative energy in electrons, while the anode would become vehicles. progressively more positive.4 Since The objective of this project is to electrons always flow from the substance investigate and employ common household being oxidized to the substance being products as nonconventional energy sources reduced, this buildup of charge would render in a car powered entirely by chemical the cell nonfunctional. reactions. The car must also be able to travel Cell potential, the difference in ability variable distances and carry variable loads of electrons to flow from one place to with no additional user input. In addition, another or the difference between the anode the goal is to gain a better understanding of and cathode potential to become oxidized, how chemical reactions can be calibrated to can be quantified in volts (V) as voltage. automate processes and how engineers Cell potential can also be thought of as the optimize what is available to achieve the potential energy that drives redox intended goal. The project began by reactions.4,5 In this sense, electrons fall from conceptualizing, building, and optimizing a the anode, which has a higher potential to battery system and stopping mechanism become oxidized, to the cathode which has a before finally building the actual car and lower potential to become oxidized. Cell testing it. potential is calculated by subtracting the reduction potentials of the anode half- reaction from that of the cathode half- 0 0 0 2. Background reaction (E cell = E cathode - E anode), or adding the oxidation potential of the anode half- 2.1 Basic Electrochemistry reaction to the reduction potential of the 0 0 cathode half-reaction (E cell = E anode + Electrochemical processes employ both 0 E cathode). Oxidation potential is the negative oxidation and reduction, which are the loss of reduction potential since both are and gain of electrons, respectively. When opposite processes. paired together in a redox reaction, electrons flow from the reducing agent (substance that 2.2 Circuits is oxidized—loses electrons) to the oxidizing agent (substance that is reduced—gains Circuit configuration is essential to electrons), generating electrical potential maximizing voltage and current output as energy that can be harnessed to perform differently designed circuits have various work, i.e., on a motor. electrical properties. Series circuits allow Galvanic cells can harness this energy electrons to flow in only one direction, while by separating the oxidation and reduction parallel circuits allow electrons to flow in 6 processes and diverting the electrons multiple directions. Electron flow is produced through an external circuit.3 The severed when one component of a series anode half-cell is the site of oxidation while circuit fails. Because the car photoreceptor, 2 motor, and power source are wired in series, parallel, the components experience the circuit is broken when the photoreceptor equivalent voltage drops and split current no longer receives light (see Diagram 1). proportionally. Since voltage is constant However, in a parallel circuit, if one over resistors in parallel, I and R are component fails, the rest of the components inversely proportional to each other. This still receive electron flow.7 means that higher resistors let less current pass through them than lower resistors when in parallel. When batteries are wired in series, their voltages add. On the other hand, when batteries are wired in parallel, the total voltage equals the voltage of a single cell. The advantage to wiring batteries in parallel is that the overall current capacity increases. In order to generate enough current to power Diagram 1 the car, three different wiring methods can be followed—series, parallel or a hybrid configuration. Three definitions that require an understanding of basic circuitry are as follow: 2.3 Aluminum-Air Batteries 1. Voltage (V) is the measure of potential difference between two points, in Aluminum and oxygen act as the volts (V) anode and cathode, respectively, in the car. 2. Current (I) accounts for the amount While oxygen itself is reduced in the battery, of electrons that flow in the wire, in amperes activated carbon is used as an adsorbent to (A) capture oxygen upon contact with the air. 3. Resistance (R) measures any Because activated carbon is very porous, its hindrance of movement for the electrons, in large surface area allows it to capture ohms (Ω) oxygen on its surface, facilitating the reaction of oxygen with water to form Mathematically, voltage, current, and hydroxide ion, which then reacts with resistance are related by Ohm’s Law: V = aluminum itself. Paper towels drenched in IR.5 Power (Watts) is defined as P = IV for saline solution serve as the salt-bridge that ohmic circuits. preserves charge neutrality in each half-cell, In a series circuit, the total resistance while copper wires transfer electron flow to equals the sum of the individual resistances the DC motor. of the components. Current is uniform throughout a series circuit and voltage drops The consistency of carbon directly split proportionally. Note that since current affects oxygen’s rate of diffusion through (I) is constant through a series circuit for the salt solution and into the aluminum resistors, V and R are directly proportional. anode. According to Fick’s Law, the rate of Therefore, higher resistors experience diffusion is directly proportional to surface greater voltage drops than lower resistors. area and concentration difference, but In a parallel circuit, total resistance is inversely proportional to the distance over the reciprocal of the sum of the reciprocals which diffusion occurs.7 The size of the of each individual resistance. When wired in activated carbon particles gives perspective 3 into the manner in which mass transport has a higher reduction potential, is reduced occurs in a reaction chamber. In this case, instead of oxygen. Thus, both increasing and oxygen from the air diffuses into the porous decreasing pH are hypothesized to increase medium with the help of activated carbon. cell voltage and current.8 This can be seen in The surface of the carbon between particles Equations 4 and 5. act as a ‘oxygen carrier’ and eventually - - - initiates the reduction process with the (4) ClO- + H2O + 2e → Cl + 2OH o electrolyte solution. Larger particles will not E net = 0.89 be able to carry out the adsorption process + - (5) HOCl + H + e → ½Cl2 (g) + H2O due to their limited surface area, while o E net = 1.63 smaller particles will impede the diffusion of oxygen.
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