Energy in Gasoline Energy in Gasoline The Department

Energy in Gasoline

Energy in Gasoline The Department of Energy [DOE] web page says that there are 124262 BTU or 36. 4 k. Wh of energy in a gallon of gasoline. They also say that 1 gallon of diesel has 138691 BTU or 40. 6 k. Wh of energy. I met a petroleum engineer and asked him how much energy was in a gallon of California gasoline and he said about 107000 BTU depending on the time of year. California gasoline is 10% ethanol which has much less BTU/gallon then gasoline. 107000 BTU would be about 31. 4 k. Wh.

Motor Efficiency A long time ago I was told that a gasoline engine was about 20% efficient in city driving. I was told that a diesel engine was about 30% efficient and that a turbo-diesel could approach 40% efficiency. A DC motor and controller in an electric car is about 85% efficient. An AC motor and controller can approach 95% efficiency. In addition, the voltage needed to charge a batter is higher then what the battery provides. The battery charge/discharge cycle is about 80% efficient.

Energy Comparison It takes almost 20 k. W from the battery to keep a small electric vehicle going at 60 mph on a level road. That would be 20 k. Wh for 60 miles or 3 miles per k. Wh. That would be 25 k. Wh from the wall to deliver 17 k. Wh to the wheels To go 60 miles in an hour would require: (17/31. 4)/20% = 2. 71 gal CA gasoline (17/36. 4)/20% = 2. 34 gal AZ gasoline (17/40. 6)/30% = 1. 40 gal Diesel (17/40. 6)/40% = 1. 05 gal Diesel - Turbo

Energy Comparison In other words: 60/20 = 3 miles / k. Wh EV 60/2. 71 = 22. 1 mpg CA gasoline 60/2. 34 = 25. 6 mpg AZ gasoline 60/1. 40 = 42. 8 mpg diesel 60/1. 05 = 57. 1 mpg turbo diesel At a steady 60 mph on level road in a typical small car that can hold 4 passengers and luggage.

Energy Consumption Note that the calculations are a rough “back of envelope” or “ball park” since the power an actual vehicle requires depends on weight, aerodynamics, tire rolling resistance, driver ability, etc. If the mpg of a vehicle is known, this data can be used to estimate the k. Wh needed in a gasoline to electric conversion.

Energy Russ Lemon Russ@Far. Too. Much. Info