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Energy in Gasoline

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					Energy in Gasoline
           Energy in Gasoline
  The Department of Energy [DOE] web page says
that there are 124262 BTU or 36.4 kWh of energy
 in a gallon of gasoline. They also say that 1 gallon
 of diesel has 138691 BTU or 40.6 kWh 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 kWh.
           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 kW from the battery to keep a
 small electric vehicle going at 60 mph on a level
  road. That would be 20 kWh for 60 miles or 3
 miles per kWh. That would be 25 kWh from the
       wall to deliver 17 kWh 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 / kWh 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 kWh
needed in a gasoline to electric conversion.
     Energy




 Russ Lemon
Russ@FarTooMuch.Info

				
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posted:12/7/2012
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