Assume that half of the gasoline usage in the nation could be replaced with batt
ID: 1718608 • Letter: A
Question
Assume that half of the gasoline usage in the nation could be replaced with battery powered electric vehicles. Do we have enough electrical capacity at present to supply this electric energy during off peak hours, when batteries would normally be charged on off peak usage electric rates? Note, gasoline, from previous problems, represents 45% of the 7E9 barrels of oil consumer per year, at 6.0GJ per barrel of oil (6.0E9 J). Assume that the current transportation fleet to be replaced with electric power has a thermal efficiency of 16% for their internal combustion engines. Assume the electric efficiency (batteries and motors) is 75% (85% for electric motors, including regenerative braking, and 90% for the batteries). Also assume that 30% of the nation's installed electric capacity is available for 10 off-peak hours per day. (30% of 1,000,000 MW).Explanation / Answer
Energy obtainable from gasoline per year = 0.5 * 0.45 * 7 * 10^9 * 6 * 10^9 J
Energy usage from gasoline per year = 0.16 * 0.5 * 0.45 * 7 * 10^9 * 6 * 10^9 J = 151200 * 10^13 Joules
Energy obtainable from electricity every year = 0.3 * 10^ 12 * 10 * 3600 * 365
Energy usage from electricity per year = 0.75 * 0.3 * 10^ 12 * 10 * 3600 * 365 J
= 295650 * 10^13 Joules
therefore we have enough electrical energy to provide for this.