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We Could Have Had Electric Cars from the Beginning

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Re: We Could Have Had Electric Cars from the Beginning

#251

Post by magduf »

avar wrote: post #243
magduf wrote: post #234

Earlier quoted context omitted.

>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.

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 opti…

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.

Re: We Could Have Had Electric Cars from the Beginning

#252

Post by RobertRoberts »

nostrademons wrote: post #136
RobertRoberts wrote: post #101

Earlier quoted context omitted.

I am not sure it's less efficient by default or simply because of lack of R&D into making steam engines better. I read about a government program in maybe the 70s (oil crisis?) where steam engines were reviewed to replace gas engines. The reason being is that burning fuel at atmospheric pressure means you burn it more cleanly and fully. This sounds like an efficiency balance at some level, certainly a pollution advan…

You run into Carnot cycle [1] physical limits. The efficiency of any heat engine is bounded by 1 - Tc/Th, i.e. the ratio of the absolute temperatures of the cold reservoir (usually the exhaust gases) to the hot reservoir (combustion temperature). To make an engine more efficient, it needs to run as hot as possible. Non-superheated steam engines are bounded by the boiling point of water (373 C); assuming 21 C outside…

It seems something is not possible until someone figures a way to do it. I could see steam/sterling engines combined with electric could do amazing things. Primarily because of low pollution (from what I read, almost none in some cases) of burning almost any combustible fuel.

Even if there are some efficiency limitations, a small steam generator (range extender) combined with an electric vehicle could be ideal.

I really don't think efficiency is the primary problem with steam/heat tech, I think it's politics and society and possibly greed.

Edit: a quick search, it seems the Carnot limit applies to ICE engines as well. So your argument seems to be contradictory. Can you clarify how ICE engine efficiency is different from steam, related to the Carnot limit?

Re: We Could Have Had Electric Cars from the Beginning

#253

Post by crimsonalucard »

magduf wrote: post #234
godelski wrote: post #129

Earlier quoted context omitted.

Another reason: Even today the energy density of batteries is SUBSTANTIALLY smaller than that of fossil fuels. [0] We frequently see this graph [1] showing how far batteries have come (they have! and we need to keep going) but not understanding this is part of the issue too. [0] is why we need to keep researching, but [0] is why electric was never going to win in the beginning. It is taking very advanced materials to…

>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.

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.

Re: We Could Have Had Electric Cars from the Beginning

#254

Post by crimsonalucard »

If we replaced all cars with EV's how much greenhouse gas would we actually curb? I know we're shifting the strain of the car producing greenhouse gases tp the power plant. Anybody know the numbers?

Intuitively I always thought the only way of actually making a dent in emissions is to change the way we live by shifting to public transportation. Suburbia is what makes the US the leading greenhouse gas producers and only changing the way we live to be more like cities such as NYC or Tokyo do we actually stand to make a change. We need to reduce the usage of cars to make a meaningful dent in greenhouse gas emissions.

Re: We Could Have Had Electric Cars from the Beginning

#255

Post by nostrademons »

RobertRoberts wrote: post #252
nostrademons wrote: post #136

Earlier quoted context omitted.

You run into Carnot cycle [1] physical limits. The efficiency of any heat engine is bounded by 1 - Tc/Th, i.e. the ratio of the absolute temperatures of the cold reservoir (usually the exhaust gases) to the hot reservoir (combustion temperature). To make an engine more efficient, it needs to run as hot as possible. Non-superheated steam engines are bounded by the boiling point of water (373 C); assuming 21 C outside…

It seems something is not possible until someone figures a way to do it. I could see steam/sterling engines combined with electric could do amazing things. Primarily because of low pollution (from what I read, almost none in some cases) of burning almost any combustible fuel. Even if there are some efficiency limitations, a small steam generator (range extender) combined with an electric vehicle could be ideal. I rea…

The Carnot limit is a simple statement about temperatures: the thermodynamic efficiency of a heat engine is 1 - the ratio of cold/hot temperatures in Kelvin. In practice that means that efficiency goes up the hotter you can make the engine's working fluid, and that (because you start at 294K) you have to go pretty high to get really good efficiencies.

The relevance to ICE vs. steam is largely about material science. You're limited first of all by mechanism by which the working fluid is heated and second by the materials used to contain it. Regular non-superheated steam never gets past 100C (373K), because once it does it boils off and the steam transmits the heat away from the heat source into the engine. Superheated steam (as in a nuclear reactor or military-grade steam turbine) can get significantly higher than that, and reach corresponding efficiencies, but you have to figure out how to continue applying the heat source to the steam after it has boiled, and that steam will be under correspondingly high pressure (because of the ideal gas law: PV = nRT), so you need materials that can both contain the high pressure and don't degrade under heat. The working fluid within an ICE is entirely contained within the engine; thus, the primary constraint is that the material used to construct the cylinders can't melt or deform under the heat of combustion. The big advantage of ICEs is that you don't need any piping, though, so you can machine the engine out of a solid block of iron or similar material and get all the strength that results.

Electric or solar-thermal Stirling engines actually do have very good efficiency ratings. But the key here is for stationary uses. They are big, bulky things, because they have to be to provide sufficient heating to the working fluid and then move it to and through the engine without any pipes bursting.

Moving vehicles have a large constraint: any engine adds to the weight of the vehicle, and has to be accelerated along with the payload. So power-to-weight is crucial: an engine that has equal efficiency but weighs as much as a car has effectively half the efficiency, because you need to move twice as much weight around. That's why most of the interest is in either smaller (and hence lighter) ICE cars or in electric drive: electric motors have very good power-to-weight ratios if you can make the battery storage light enough.

Re: We Could Have Had Electric Cars from the Beginning

#256

Post by godelski »

magduf wrote: post #251
avar wrote: post #243

Earlier quoted context omitted.

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 opti…

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…

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).

Re: We Could Have Had Electric Cars from the Beginning

#257

Post by RobertRoberts »

nostrademons wrote: post #255
RobertRoberts wrote: post #252

Earlier quoted context omitted.

It seems something is not possible until someone figures a way to do it. I could see steam/sterling engines combined with electric could do amazing things. Primarily because of low pollution (from what I read, almost none in some cases) of burning almost any combustible fuel. Even if there are some efficiency limitations, a small steam generator (range extender) combined with an electric vehicle could be ideal. I rea…

The Carnot limit is a simple statement about temperatures: the thermodynamic efficiency of a heat engine is 1 - the ratio of cold/hot temperatures in Kelvin. In practice that means that efficiency goes up the hotter you can make the engine's working fluid, and that (because you start at 294K) you have to go pretty high to get really good efficiencies. The relevance to ICE vs. steam is largely about material science.…

Thanks for explaining this in more detail, it's hard to get a simple summary from google on a specific comparison like this.

Re: We Could Have Had Electric Cars from the Beginning

#258

Post by godelski »

hwillis wrote: post #184
godelski wrote: post #129

Earlier quoted context omitted.

Another reason: Even today the energy density of batteries is SUBSTANTIALLY smaller than that of fossil fuels. [0] We frequently see this graph [1] showing how far batteries have come (they have! and we need to keep going) but not understanding this is part of the issue too. [0] is why we need to keep researching, but [0] is why electric was never going to win in the beginning. It is taking very advanced materials to…

This is an incredibly myopic take masquerading as "first principles". First, you're flat wrong on the differences between gas and batteries, especially for cars. Second, you need an actual reason energy density is the fundamental metric- cars aren't rockets and weight isn't the end-all. It's impossible to neglect the efficiency here. Car-scale combustion engines have a real world efficiency of around ten percent comp…

First off, your comment is mainly about current technologies. That misses the entire point of my comment. They were working in the lead-acid regime. Calling my graphs out of date is moot (even when you consider that 500Wh/kg is only a slight bump in my [0] link). I do think EV will win in the end, but that that statement has nothing to do with what my original comment was about. Also current gasoline engines are more than 25% efficient, not 10. But that's beside the point.

So if you're going to attack me, attack me on my points. Don't create a false comparison. Petrol had more than 10% efficiency from the get go. 10% of 50MJ/kg is much larger than 100% of 0.18MJ/kg (upper end of Lead-acid). You'd have to have an engine under 0.1% efficiency for EV to be able to compete in the beginning. (You'd have to have that upper end of lead-acid) This is all my comment was about. The state of technology and manufacturing (both!) over a hundred years ago. I was responding to "We could have had electric cards from the beginning" not "We can have electric cars now". If I said the latter then I understand your visceral, but I didn't.

Yeah, things are different now. Those 1.8MJ/kg engines at 100% (we'll round up) are able to start competing with 25% of 50MJ/kg(12.5MJ/kg), but there's still a way to go. That's why a Camry and Model 3 have similar weights and the Camry gets twice the range. But yeah, things are looking much better for the EV's now because there are other factors that matter like torque, space, and we don't need to often go more than 200 mi. But most of these factors are, for the average user, less important and so don't matter as much. Especially in the beginning where electric vehicles were struggling to drive between cities.

I look forward to the future of EV, but that doesn't discredit the history. And that doesn't make lack of technology a myopic take. Reality is just that a petrol vehicle getting 100 miles range is easier than an electric and requires less advanced technology and manufacturing techniques. But technology and manufacturing has progressed A LOT in the last hundred years.

Re: We Could Have Had Electric Cars from the Beginning

#259

Post by avar »

magduf wrote: post #251
avar wrote: post #243

Earlier quoted context omitted.

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 opti…

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…

1) Guilty as charged. It's far from an apples to apples comparison, but if you compare like-to-like models of EVs and similar ICE vehicles you get the same story everywhere. Around 1/2 to 1/3 the range of the ICE vehicle, and 20-25% heavier.

E.g. the Chevy Sonic[1] & Bolt[2] are equivalent EV/ICE vehicles. They weigh 1300 & 1600 kg respectively, have the same cargo volume, but ranges of ~750 km (most pessimistic) & ~380 km (most optimistic).

So that's the like-to-like comparison. We can see that all things added up these vehicles are heavier and have much less range.

2) These volume savings are overstated and if anything work in the favor of ICEs, not EVs.

Look at a cutaway of the Chevy Bolt[3] or other reasonably priced EV like the Hyundai Ioniq or BMW i3[4]. Yes you get relatively more cargo volume in a Tesla Model S compared to other Sedans, but at that point you're paying tens of thousands for a luxury vehicle whose gimmick is things like the frunk. If you drop the same money on an ICE that optimizes for cargo space you'll come out way ahead.

3) A Tesla Model S's 85 kWh battery pack is 540 kg. If that's 3-4 adult Americans they've gotten a bit fatter on average since I last checked :)

In any case, that gets you a 420 km range, which tells you something about how heavy the car would be and how little space would be left for anything else if they were aiming for ICE-like range.

4) "Gas cars do not get significantly better fuel economy with empty fuel tanks": Yeah exactly. The point is that EVs inherently do not share this benefit.

5) Yeah we're talking about cars, but the point of bringing electric airplanes into it is to show how electric vehicles are weight and volume limited in an area where everything is done to bright the weight down, whereas someone might (wrongly) argue that for cars the weight doesn't matter that much.

1. https://media.chevrolet.com/media/us/en/chevrolet/vehicles/s...

2. https://media.chevrolet.com/media/us/en/chevrolet/vehicles/b...

3. http://www.boronextrication.com/2016/04/03/2017-chevrolet-bo...

4. https://www.autoblog.com/photos/bmw-i3-ev-cutaway/

Re: We Could Have Had Electric Cars from the Beginning

#260

Post by godelski »

crimsonalucard wrote: post #253
magduf wrote: post #234

Earlier quoted context omitted.

>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.

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.

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.
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