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> Internal combustion engine vehicles themselves turn 100% of the energy from gasoline into heat, localized to the roads they are driving on. Let's consider a

by tzs 2y ago

> Internal combustion engine vehicles themselves turn 100% of the energy from gasoline into heat, localized to the roads they are driving on. Let's consider a thought experiment. We have an ICE car at the bottom of a hill. The car has a trailer attached and there is a weight on the trailer. The mass of the trailer and the weight combined is 500 kg. The car is started, drives to the top of the hill which is an elevation gain of 100 m, drops off the trailer and weight, and drives back down to the bottom of the hill and is shut off. The trailer and weight has gained 9.8 m/s^2 x 500 kg x 100 m = 490 000 J of gravitational potential energy, which is not heat. If all of the energy from the car's gasoline became heat where did that 490 000 J of non-heat energy that the car gave the trailer and weight come from?

jeff_tyrrill 2y ago
100% of the energy becomes heat eventually. For a typical trip, this happens by the trip conclusion. (And also each time the car pauses, such as a stoplight.) For the trailer-on-hill example, it concludes when the trailer (eventually) is towed or rolls down the hill and comes to a rest from friction. The weighted trailer is being used like a battery and modifies the situation in the same way as if it were a hybrid car (non-plug-in battery that recharges through regenerative braking and/or directly from the ICE).
- tzs 2y ago
  If we are going to count energy that is delivered to the payload in a non-heat form that eventually becomes heat then yes, 100% of an ICE's energy from gas goes into heat--but so does 100% of an EV's energy or a bicycle's energy. The difference between an ICE and an EV with similar sizes and shapes as far as heat goes is that although all the energy from both eventually ends up as heat the EV produces less unnecessary heat. To move the payload a given distance the ICE will use about 4 times as much energy. Only 1/4 of the energy from the gasoline goes toward accomplishing the job of the vehicle. The other 3/4 is waste heat.

by tzs 2y ago

jeff_tyrrill 2y ago

100% of the energy becomes heat eventually. For a typical trip, this happens by the trip conclusion. (And also each time the car pauses, such as a stoplight.) For the trailer-on-hill example, it concludes when the trailer (eventually) is towed or rolls down the hill and comes to a rest from friction. The weighted trailer is being used like a battery and modifies the situation in the same way as if it were a hybrid car (non-plug-in battery that recharges through regenerative braking and/or directly from the ICE).

tzs 2y ago
If we are going to count energy that is delivered to the payload in a non-heat form that eventually becomes heat then yes, 100% of an ICE's energy from gas goes into heat--but so does 100% of an EV's energy or a bicycle's energy. The difference between an ICE and an EV with similar sizes and shapes as far as heat goes is that although all the energy from both eventually ends up as heat the EV produces less unnecessary heat. To move the payload a given distance the ICE will use about 4 times as much energy. Only 1/4 of the energy from the gasoline goes toward accomplishing the job of the vehicle. The other 3/4 is waste heat.