| The media are full of news about electric cars. The | | | | electric energy in its battery, the combustion engine |
| $100,000 Tesla electric sports car is going to be sold | | | | powered car stores energy in the form of gasoline or |
| soon, automakers are falling over each other to | | | | diesel fuel in its fuel tank. |
| announce new electric vehicles, and entrepreneurs | | | | Now let us take a comparative look at the cost of |
| across the world are jockeying for venture capital. | | | | storing and paying for enough electric energy or liquid |
| Petroleum prices have jumped during the last year | | | | fuel energy to drive 100 miles. Let us assume that |
| and everybody is feeling the pain at the pump. Not a | | | | both cars will have the same power requirements to |
| single soul is concerned about filling up the batteries | | | | drive 100 miles. In this respect the match-up |
| of his next electric car with electricity. After all, you | | | | between Tesla and Corvette is perfect. But how do |
| just plug the car into the next receptacle and there | | | | we compare prices at the gas station with utility |
| seem to be no appreciable costs. | | | | costs at the receptacle? |
| Joe owns a Corvette, a high performance car | | | | Energy contained in gasoline can be converted into |
| manufactured by General Motors, which according to | | | | mechanical energy only at the limited energy |
| the car manufacturer drives 25 miles per gallon. | | | | conversion efficiency of a typical heat engine. The |
| Joe's monthly commute is 1000 miles, he drives very | | | | Corvette engine will have an energy conversion |
| carefully, and actually achieves 25 MPG on his daily | | | | efficiency of about 35%. (Fuel fired engines may |
| trip going to work and running errands. At $4.00 per | | | | eventually reach 50% peak energy conversion |
| gallon at the pump he is paying $160 for gasoline | | | | efficiency after decades of future advancements). |
| every month. | | | | Conversion efficiency of electric power from the |
| Joe is thinking about buying the Tesla, an electric | | | | receptacle into stored energy first and into |
| sports car. He tried to find the cost of electricity for | | | | mechanical energy later is much higher at about 85%. |
| driving this car. He could not find any data anywhere. | | | | The energy content of gasoline is 131 MJ/gallon |
| Joe knows that he must explain to his wife why he | | | | (megajoule per gallon). For driving 100 miles the |
| needs to save energy and money before buying the | | | | Corvette will burn four gallons of gasoline or 524 MJ |
| Tesla, a new, very fast electric sports car. | | | | 100 miles. Only 35% of the energy in gasoline or 183 |
| The Tesla will accelerate faster than his Corvette. | | | | MJ will be used to propel the Corvette. This is the |
| There is no doubt that an electric vehicle can have a | | | | mechanical energy transmitted to the rear wheels of |
| faster acceleration than a gasoline car. Electric motors | | | | the Corvette. Virtually the same amount of energy |
| and liquid fuel engines are just two different devices | | | | must be transferred to the wheels of the electric |
| converting electric energy or petroleum fuel energy | | | | car, the Tesla. Both cars are very similar in size and |
| into mechanical energy. Electric motors can generate | | | | driving characteristics. |
| much higher torque at the wheels at much lower | | | | However, the Tesla has to take a little more energy |
| turning speeds. | | | | from the receptacle because the charging, storing, |
| In comparison, electric motors will have several | | | | and discharging of electricity in the battery |
| shortcomings, too. They certainly will emit more | | | | experiences energy losses. These losses are about |
| pollutants and more carbon dioxide as long as coal is | | | | 15% of the electric energy taken from the |
| used for producing electric power. Overall energy | | | | receptacle and will not be available at the wheels. The |
| efficiency of the electric car, from power plant to | | | | Tesla owner will, therefore, pay 1.15 times as much |
| the road, is still worse than that of a modern | | | | to get the same energy to the wheels as the |
| automobile propelled by an advanced combustion | | | | Corvette or 211 MJ per 100 miles. Electric energy is |
| engine. | | | | priced in the form of dollar per kilowatt hour or $ |
| The biggest drawback of electric cars is the small | | | | kWh. The average price of electricity in the US is |
| number of miles they can drive after a complete | | | | $0.09/kWh. The factor for converting energy |
| recharge. Additionally, the charging of an empty | | | | measured in MJ to energy measured in kWh is 0.2778 |
| electric battery will take forever, high performance | | | | kWh/MJ. |
| batteries are expensive, and will only have a limited | | | | To drive 100 miles, the Tesla will consume 58.6 kWh |
| life expectancy. | | | | of electricity at a cost of $5.28. The Corvette will |
| What about energy costs for driving an electric car | | | | consume 4 gallons of gasoline at a cost of $16. Now |
| compared to a gasoline powered car? Both vehicles | | | | we know that the Tesla will save about $10 per 100 |
| will have to store energy. The electric car stores | | | | miles or $10,000 over 100,000 miles. |