Energy Excercise

Energy exercise Fossil fuel power plants operate by using the energy from burning the fuel to boil steam as in Figure 1. The steam passes through a turbine, which converts the steam’s energy into rotational motion. A generator then converts the rotational energy into electricity. Typically, about 80% of the energy from the burning fuel is transferred to the steam and 30% of this energy is converted to electricity. In the case of coal, 27 MJ of energy are released for every kg of coal burned, and coal is 78% carbon by mass. Assuming all the carbon from the fuel produces CO2 (limited amounts of carbon monoxide CO and other gasses are also formed), compute the mass of CO2 produced for every MJ of electricity produced. Internal combustion engines burn gasoline (or diesel) to generate shaft power to drive automobiles. Typically, about 15% of the heat from combustion is lost and about 20% of the remaining energy is converted to shaft power. Gasoline releases approximately 47 MJ for every kg burned, and is composed of 89% carbon by mass. Compute the mass of CO2 produced for every MJ of shaft power produced. Compare the CO2 emissions for power plants and internal combustion engines. If the car can travel 25 miles on a gallon of gas, compute the mass of CO2 expelled when travelling 100 miles. A plug-in electric vehicle uses electricity to charge an onboard battery which converts the stored energy to shaft power to drive the vehicle. Battery energy is converted to shaft power at efficiencies around 80%. Transmission losses of 6% occur when transmitting electricity from the power plant to the charging station. Assuming the electric vehicle requires the same shaft energy as the internal combustion automobile to travel 100 miles, calculate the mass of CO2 expelled during electricity generation for the 100 mile trip. Compare the CO2 emissions from internal combustion engines and electric vehicles. In order to perform the calculations, find the percentage of electricity generated from fossil fuels in Georgia and assume all fossil plants exhibit similar performance as the coal plant described here. As a comparison find the fractions of energy generated by nuclear, fossil, and renewable sources for Georgia, Washington state, and the national average.