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>Another reason: Even today the energy density of batteries is SUBSTANTIALLY smaller than that of fossil fuels. That's irrelevant. The thing people keep forge

by magduf 7y ago

>Another reason: Even today the energy density of batteries is SUBSTANTIALLY smaller than that of fossil fuels. That's irrelevant. The thing people keep forgetting with fossil fuels is that most of that energy is being wasted to just produce heat. With an EV, 95-98% of the battery's energy is being used for propulsion (unless you turn on a heater of course). In short, you're comparing apples to oranges.

gnu8 7y ago
That heat is not wasted if you live in a place that has seasons. I’d like to see EVs with a petrol burning heating system that could provide cabin and battery heat during winter. Many gas stations sell untaxed kerosene that I think could be used because it’s for heating, not motor fuel.
avar 7y ago
It's not irrelevant. The high water mark for Li-Ion efficiency is 0.875 MJ/kg[1] (in practice e.g. a Tesla seems to be 0.7 MJ/kg). For petrol that's 46.4. Now, let's adjust that for the efficiency of the power train. Let's give the electric car 100% (in practice it's 95-97%). Production ICE engines are around 20%. That gives us 46.4 x 0.20 = 9.28 MJ/kg. That's a 10.6x difference in favor of petrol if we take the optimistic 0.875 number. The most fuel-efficient cars sold today consume around 5L/100km. A liter of petrol is 0.78 kg. A 1000 km of range is the probably holy grail for an electric car. A a car powered by petrol needs to carry 39 kg of fuel at the start of a trip for that range. That'll be at best ~390 kg for the Tesla at its theoretical limits, which isn't counting overhead weight associated with the battery pack, and unlike a petrol-powered car the weight doesn't reduce as you go through the trip (a significant hurdle for e.g. electrically powered airplanes). Of course the power train of an electric car is lighter than on the ICE-power vehicle, but the ICE still wins, and all of this is before we get to the battery needing much more volume than petrol, although as the Tesla shows you can win back some space by placing it in the floor, which isn't a realistic option for ICE. None of this means electric cars aren't viable, but the weight and volume differences for the same MJ are inherent, and aren't going to go away. 1. https://en.wikipedia.org/wiki/Energy_density https://en.wikipedia.org/wiki/Energy_density
- magduf 7y ago
  You're comparing solely based on the weight of the energy storage medium (fuel/batteries). Two problems here: 1) ICE cars have big, heavy engines to burn that fuel and produce mechanical power, whereas BEVs have much smaller motors, so there's a big weight advantage for the BEV. (I see you addressed this, but you're also missing the volume savings with electric motors; gas engines take up a ton of space with all the associated plumbing and systems). 2) In gas cars, the fuel isn't really a big component of the vehicle's weight, which is why Tesla is able to add another 500-1000 lbs of batteries and not have too much trouble with that. That's basically like adding 3-4 adult Americans. Gas cars do not get significantly better fuel economy with empty fuel tanks. As for airplanes, this discussion is about cars, not airplanes, where things are really different. Power-to-weight-ratio is far more important with aircraft since they have to fight gravity constantly. Aircraft will surely be the last bastion of fossil fuel usage because of this.
  - godelski 7y ago
    But electric vehicles weigh more than gas equivalents. A Model 3 (standard) is 3552lbs. I found that a Camry is similar in weight (3572lbs; similar weights for the Leaf and Volt). But if we compare the range the Model 3 has 220 mi while the Camry has 352/512 (city/highway). We can pretty conservatively say that Camry is going to get approximately twice the range for the same weight. And extra 500lbs on the Tesla only gets you another 100 miles. So while the gp to this comment and my original comment focus on the weight and density of the storage media this is one of the largest factors. What the graphs I linked to show is that basically the weight for gasoline is not a major part of the vehicle weight. But on the other hand, for electric vehicles it is a significant weight. The point I was making with my original comment wasn't that electric vehicles won't win (I think they will) but rather that it is a ridiculous notion that they would have won from the beginning. These new batteries take extremely complex engineering to achieve. And only because of these new batteries are they starting to win. If we go back to when everything was made from steel then your electric car is also going to gain more weight. Even from the get go petrol vehicles had longer ranges. My comment (and a lot of people are missing this) was not about NOW it was about the past. I want to stress that it has nothing to do with current tech. It has to do with what technologies they had available to them. Also how impressive the work is that has been done to create these new generations of batteries (and is still being put in). Petrol won because it was the easiest route. But EV is winning because it is superior (with the advancements and the path that it is on).
crimsonalucard 7y ago
Even with heat being wasted, the energy density is so high that it still outpaces batteries by a significant margin. For example... try making a battery powered 747 airliner... you can't because the weight is too high.
- godelski 7y ago
  I'm surprised many people missed this. That 10% of 50MJ/kg is still more than 100% of 1.8MJ/kg (current advanced batteries) and substantially more than 100% of 0.18MJ/kg (lead acid). Which my comment was about manufacturing and technology over a hundred years ago. My comment was focused on the latter comparison and not the former (which was just a side note). I guess everyone latched onto my side comment.

by magduf 7y ago

gnu8 7y ago

That heat is not wasted if you live in a place that has seasons. I’d like to see EVs with a petrol burning heating system that could provide cabin and battery heat during winter. Many gas stations sell untaxed kerosene that I think could be used because it’s for heating, not motor fuel.

avar 7y ago

It's not irrelevant. The high water mark for Li-Ion efficiency is 0.875 MJ/kg[1] (in practice e.g. a Tesla seems to be 0.7 MJ/kg). For petrol that's 46.4. Now, let's adjust that for the efficiency of the power train. Let's give the electric car 100% (in practice it's 95-97%). Production ICE engines are around 20%. That gives us 46.4 x 0.20 = 9.28 MJ/kg. That's a 10.6x difference in favor of petrol if we take the optimistic 0.875 number. The most fuel-efficient cars sold today consume around 5L/100km. A liter of petrol is 0.78 kg. A 1000 km of range is the probably holy grail for an electric car. A a car powered by petrol needs to carry 39 kg of fuel at the start of a trip for that range. That'll be at best ~390 kg for the Tesla at its theoretical limits, which isn't counting overhead weight associated with the battery pack, and unlike a petrol-powered car the weight doesn't reduce as you go through the trip (a significant hurdle for e.g. electrically powered airplanes). Of course the power train of an electric car is lighter than on the ICE-power vehicle, but the ICE still wins, and all of this is before we get to the battery needing much more volume than petrol, although as the Tesla shows you can win back some space by placing it in the floor, which isn't a realistic option for ICE. None of this means electric cars aren't viable, but the weight and volume differences for the same MJ are inherent, and aren't going to go away. 1. https://en.wikipedia.org/wiki/Energy_density https://en.wikipedia.org/wiki/Energy_density

magduf 7y ago
You're comparing solely based on the weight of the energy storage medium (fuel/batteries). Two problems here: 1) ICE cars have big, heavy engines to burn that fuel and produce mechanical power, whereas BEVs have much smaller motors, so there's a big weight advantage for the BEV. (I see you addressed this, but you're also missing the volume savings with electric motors; gas engines take up a ton of space with all the associated plumbing and systems). 2) In gas cars, the fuel isn't really a big component of the vehicle's weight, which is why Tesla is able to add another 500-1000 lbs of batteries and not have too much trouble with that. That's basically like adding 3-4 adult Americans. Gas cars do not get significantly better fuel economy with empty fuel tanks. As for airplanes, this discussion is about cars, not airplanes, where things are really different. Power-to-weight-ratio is far more important with aircraft since they have to fight gravity constantly. Aircraft will surely be the last bastion of fossil fuel usage because of this.
- godelski 7y ago
  But electric vehicles weigh more than gas equivalents. A Model 3 (standard) is 3552lbs. I found that a Camry is similar in weight (3572lbs; similar weights for the Leaf and Volt). But if we compare the range the Model 3 has 220 mi while the Camry has 352/512 (city/highway). We can pretty conservatively say that Camry is going to get approximately twice the range for the same weight. And extra 500lbs on the Tesla only gets you another 100 miles. So while the gp to this comment and my original comment focus on the weight and density of the storage media this is one of the largest factors. What the graphs I linked to show is that basically the weight for gasoline is not a major part of the vehicle weight. But on the other hand, for electric vehicles it is a significant weight. The point I was making with my original comment wasn't that electric vehicles won't win (I think they will) but rather that it is a ridiculous notion that they would have won from the beginning. These new batteries take extremely complex engineering to achieve. And only because of these new batteries are they starting to win. If we go back to when everything was made from steel then your electric car is also going to gain more weight. Even from the get go petrol vehicles had longer ranges. My comment (and a lot of people are missing this) was not about NOW it was about the past. I want to stress that it has nothing to do with current tech. It has to do with what technologies they had available to them. Also how impressive the work is that has been done to create these new generations of batteries (and is still being put in). Petrol won because it was the easiest route. But EV is winning because it is superior (with the advancements and the path that it is on).

crimsonalucard 7y ago

Even with heat being wasted, the energy density is so high that it still outpaces batteries by a significant margin. For example... try making a battery powered 747 airliner... you can't because the weight is too high.

godelski 7y ago
I'm surprised many people missed this. That 10% of 50MJ/kg is still more than 100% of 1.8MJ/kg (current advanced batteries) and substantially more than 100% of 0.18MJ/kg (lead acid). Which my comment was about manufacturing and technology over a hundred years ago. My comment was focused on the latter comparison and not the former (which was just a side note). I guess everyone latched onto my side comment.