Before this year, it never occurred to me the relevance of thermodynamics in the study of environmental sciences. But if there is one thing I’ve learned this year, it is that EVERYTHING has something to do with our environment. Heat is a form of energy and there stands the intimate relationship between thermodynamics and the environment…
Heat is both a form of energy and a form of motion (at the atomic level). The internal combustion engine (ICE), like the one found in cars, makes use of both of the forms of heat. The main characteristic of an internal combustion engine is that it burns fuel inside the engine itself in order to convert it into useful work. An ICE’s efficiency depends on the percentage of the fuel (input) that can be converted into useful work.
First, the battery (ex. car battery) powers the starter motor… A typical ICE functions on a 4-step cycle:
1. “The piston moves down the cylinder creating a partial vacuum and the inlet valve opens to introduce air and some fuel, such as petrol.” A car, for example, first converts the chemical energy of the fuel into thermal energy to then use it in mechanical work.
2. “The inlet valves close while the piston moves forward compressing the fuel-air mixture. Once maximally compressed, the mixture is ignited by the spark plug.”
3. “The burning mixture reaches high-pressure and expands to push the piston back and perform work on the car.”
4. The burnt remains (exhaust) are squeezed out as the outlet valve opens and the piston pushes inward again.
The original source of energy in this system (car engine) is the chemical potential energy within the hydrocarbon bonds in the gasoline. Fuel is burnt so make the energy within these bonds more accessible to form stronger bonds with the oxygen in the air. by burning the gasoline as hot as possible and releasing the exhaust at the closest possible ambient temperature (ensures the greatest amount of heat is used) maximum efficiency is attained. One way to allow exhaust to cool is by providing the exhaust gases to expand as much as possible before being removed.
The environmental “issue” with the use of fossil fuels, especially in ICEs, is that fossils fuels are carbon-rich nonrenewable energy deposits. Fossil fuels are extremely polluting because their combustion releases sulfur, nitrogen oxides, and carbon dioxide. Fossil fuel emissions make up more than half of the global total of CO2 emissions.
To tie it back to thermodynamics, creating efficient ICEs will not only reduce the amount of needed “dirty” fossil fuels. And by reducing the quantity of fossils fuels needed, less are burned, and less CO2 lingers in the atmosphere.
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SOURCES:
http://staff.science.nus.edu.sg/~parwani/htw/c2/node37.html
http://www.epa.gov/climatechange/emissions/globalghg.html
1 comments:
good topic and analysis
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