The Chem-E-Car Competition is an annual college engineering competition, mainly geared towards students studying Chemical Engineering or similar disciplines.
According to the competition's official rules, students must design small-scale automobiles that operate by chemical means, along with a poster describing their research. During the competition, they must drive their car a fixed distance (judged on how close the car is to the finish line) down a wedge-shaped course in order to demonstrate its capabilities. The exact distance (15-30 meters) and payload is revealed to the participants one hour before the competition. The size of designed cars cannot exceed certain specifications and cars must operate using "green" methods, which do not release any pollution or waste in the form of a visible liquid or gas, such as exhaust. The dimensions of the car are to be within 20x30x40 cm. [1] This competition is hosted in the United States by the AIChE (American Institute of Chemical Engineers), and winners of the competitions receive various awards, depending on how they placed. [1]
The competition has various rules: [1]
Each car is required to have a scientific poster explaining how the car runs (power source), some of its specific features, and how it is environmentally friendly. Judges score these posters on three general criteria: the quality of the poster and team member presentations (50%), the creativity of the design, unique features, and safety considerations (35%), and demonstration of knowledge of reactions, calibration methods by all team members, and ability by team members to answer questions posed by the judges (15%). [1]
Teams also must undergo a vehicle safety inspection during the poster session. Only teams that pass the safety inspection may continue to the performance competition. [1]
Some ideas for chemical reactions have been using pressurized gases [2] (creating oxygen or CO2 gas through a chemical reaction and allowing it to build pressure) or using electricity created by the dissolving of metals in certain acids (basic battery). One pedantic idea by Cooper Union was to use a fuel cell [3] (a cell that converts fuel to electricity via an electrochemical reaction) to power their car.
Winners in this competition are not determined by whether their car is faster or more powerful, but how accurate their chemical reaction to stop their vehicle is. This is quite difficult, especially when the distance the car has to travel is unknown until the day of the competition. So teams must find a method that is flexible enough to fit a range of distances, and reliable enough so it does not fail with real world variables (temperature, humidity, track roughness, changes in elevation, etc.). Winners in the past have had a variety of ways of dealing with this problem, such as an iodine clock reaction. [4] This reaction works by using two clear solutions (many variations) that change color after a time delay (the exact time can be found experimentally). When applied to the car, the team used a simple image sensor that could tell when the solutions changed color, at which point the cars power would shut off by cutting the circuit. [5] While the process itself is somewhat simple, accounting for the unknown variables like the payload and distance is quite difficult.