Comment by elihu
5 years ago
The raw materials may continue to cost more for EVs. Motor windings are generally copper, and batteries contain lithium and (usually) cobalt and nickel. Permanent magnet motors sometimes contain rare earths.
One could make an EV with aluminum motor windings and electrical cabling, no rare earth magnets, and lithium iron phosphate batteries. That would keep expensive materials to a minimum.
EVs don't need a catalytic converter, so that's a big thing in their favor.
I'm looking forward to mass manufacturing continuing to bring down EV component prices. I think we're a long ways from the point where material costs are the bulk of the expense.
> EVs don't need a catalytic converter, so that's a big thing in their favor.
I feel there is some sort of scam going on with catalytic converters for the last few years. I actually worked in a small family owned auto shop in the early 2000's. If a car came in with a clogged cat, we'd first fix the source of the issue (usually a mis-firing cylinder allowing raw fuel into the exhaust) and then we'd cut out the cat, and weld in a universal fit one that we'd get from the auto store for $20. Then charge the customer $200-$400 for labor. I still see universal fit ones[0] although they are $80 now. But still, if you aren't dumping raw fuel or oil into your exhaust, cats are basically good for 300k+ "normal" driving miles. I assume they are expensive now because they are all mostly specially made/custom fit since all car manufactures keep cramming bigger and bigger engines into smaller and smaller spaces.
And while I'm ranting, there's always a negative for every positive and no doubt for the catalytic converter. For a catalytic converter to convert "greenhouse gases", the engine has to be burning fuel at a perfect air:fuel ratio of 14.7:1. While cruising down the highway, an engine could easily save fuel by running a more lean mixture, but this would cause more "greenhouse gases" to go out. So choose your poison I suppose.
[0] https://imgur.com/a/7X0sPlk
I don't think cats are to address greenhouse gasses; they're focused more on reducing pollutants that affect local air quality and human health.
The main greenhouse gas from a car is carbon dioxide. The amount you create is directly proportional to the amount of fuel you burn.
I don't know why modern cats are expensive; it might have to do with the price of platinum, palladium, and so on, and the relative amount of those materials. A cheap generic cat might have the bare minimum amount of catalyst, and might not do a very good job.
> I don't think cats are to address greenhouse gasses; they're focused more on reducing pollutants that affect local air quality and human health.
I thought the same thing, but interestingly that's only kinda true. If anything, cats increase CO_2 as a desired end goal, because it's better to have CO_2 than CO or NO_x (or so the EPA has decided, I am no where near qualified to decide that). The issue with running too lean is that the reactions in the cat would rather use plain O_2 than NO_x, and so if you have too much O_2 (lean) you won't get rid of any of the NO_x [0]. Before looking into this I thought lean engines produced more NO_x because of higher cylinder temps or something like that (which might be true as well).
Cats not reducing NO_x when lean is essentially why Volkswagen (and practically every other manufacturer has been caught doing similar things to diesel engines) was cheating the test. Diesels have no throttle so they are (almost) always lean, typically very lean.
This does make me wonder, though, does running lean actually increase fuel efficiency? Obviously rich lowers fuel economy because not all the fuel burns, but assuming it all burns what does it matter if you have 1 gram of fuel to 15 grams of air in the cylinder, or 1 gram of fuel to 18 grams of air in the cylinder? You'll still get the same amount of energy, right?
[0] https://en.wikipedia.org/wiki/Catalytic_converter#Three-way
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> A cheap generic cat might have the bare minimum amount of catalyst, and might not do a very good job
It depends on the car/engine. My old Mazda RX-8 had a huge cat - longer than the muffler and cost me $2,000 to replace (including labor) back in the late 2000's.
The rotary engine in that vehicle had a terribly difficult time passing California's emission laws even when it was brand new off the lot - which led to strange "hacks" including a blower motor that moved high volumes of air through the exhaust to heat the cat sooner and somehow improve it's numbers, among other things. I assume the extra-long cat was part of the shenanigans Mazda had to go through to get it compliant.
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On the other hand the quality and performance of those $80 catalytic converters are questionable at best. They have neither the longevity, nor the performance of the original part. They might last even 10 times less, and they're usually just barely good enough to pass the emissions tests, which is already the lowest bar to pass given how all manufacturers optimize for that. Real life emissions are far worse.
And the purpose of the catalytic converter is to make sure the CO, NOx, and unburned fuel are rapidly oxidized to CO2, N, and water before leaving the exhaust system. The outcome is that you will produce more greenhouse gases but fewer compounds that are more immediately dangerous to people, especially in cities. So it reduces localized pollution at the price of more CO2.
Catalytic converters don't reduce greenhouse gases. Their function is to reduce poisonous gases: NO, NO2, O3, CO, HO2, and sometimes HCN and H2CO. The good news is that all of these compounds are thermodynamically unstable so a catalyst can destroy them.
I don't know where you got the 14.7:1 number but I am certain that NOx are unstable at any concentration (at or near STP) and will always be depleted by a catalyst.
Another commenter is unsure whether the NOx or some GHGs should be reduced preferentially. To clarify: CO2 can't be removed, it is stable; only CH4, N2O and O3 can be removed, and they are not present at relevant levels (except ozone which is poisonous) anyway. The poisonous gases are far more important — NOx pollution alone kills thousands of people every year (statistically, considering excess deaths as correlated to air pollution).
The increased price of catalytic converters is partially related to the supply of palladium, which experienced a glut following the collapse of the USSR. The Soviet palladium ran out in 2012:
https://www.mining.com/russias-stockpiles-said-to-be-deplete...
>I don't know where you got the 14.7:1 number
The cat has to be hot to catalyze. The engine is run rich so unburnt fuel makes it to the cat and is combusted there, warming it up enough to also kill the undesirable gases. This is wasted heat... unless you mount a turbocharger after the cat, which has its own set of weird tradeoffs. (I've never heard of a factory car with a rear turbo)
The reason is the increasing price of Palladium which is used by catalytic converters and your dentist. That's why there is huge increase in theft of those converters as the material is scraped and sold in the black market.
Tesla already uses aluminum for power cabling because it’s cheap and lighter weight. Tesla Model S were induction motors (at first at least) with no rare earths, and Tesla is partnering with CATL for lithium iron phosphate batteries in lower cost versions of, if I believe, Model 3 and Y.
I thought CATL makes lithium iron phosphate batteries, and lithium sulfur hasn't been commercialized yet. Unless there's some news on that front I missed?
I think induction motors tend to be less efficient than permanent magnet motors (and thus require more cooling). The Netgain Hyper9 (a popular motor for conversions) is a permanent magnet motor which doesn't use rare earths. It's very efficient but not particularly powerful (though that may be due more to the relatively low voltage it runs at).
That's cool that Tesla is using aluminum for power cables. Makes sense to save cost and weight where you can.
Yes, I meant iron phosphate. (I’ve had sulfur on my mind from Bye Aerospace’s 925km range 8-seat electric aircraft, working with Oxis Energy.)
Note to replace copper wiring with aluminum, you have to go up at least one gauge size.
Or raise the voltage at the same time you change from Cu to Al.
Yeah, aluminum is a worse conductor so you need thicker cable. It's less dense, though, so I think it usually comes out as being lighter. Thicker cables can be more inconvenient. I think aluminum also tends to have more problems with oxidation causing too much resistance at electrical contacts.
I think for motors generally you just end up with a larger motor for the same amount of power.
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"Tesla already uses aluminum for power cabling because it’s cheap and lighter weight."
Ugh, really ? That offends my sensibilities ...
Why? A properly engineered aluminum power cable is superior to a copper one when weight is at a premium.
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cmon man. the total weight of pricey metals in a car is so low, there is no way its going to offset the cost of precision machining. tolerances < 1 thou and callouts for surface finish and perpendicularity are expensive!
Hard to say. Those tolerances would be expensive in general purpose machine work, but in engines those tolerances have been in place since at least the 1930s, and so economies of scale bring those costs down (ie, using specialized machines that are really good at boring precision holes and measuring them. The costs of those machines get amortized over every engine).
I'm sure a motor is cheaper than an engine (less steps to make), but they still require precision manufacturing, and all the other parts aside from the motor (driveshaft, axles, brakes, etc.) are more or less the same.
Plus, the cost of those other materials is going to increase if demand for EVs goes up.
evs could drive lithium but i really doubt they would influence copper that much, since it is used so much already
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Somehow car manufacturers are able to make engines, transmissions, transaxles, and differentials really cheaply, so apparently all that precision manufacturing doesn't really cost all that much when producing at high volume. This should be equally true of EVs and combustion-engine cars.
Raw material costs might still be less than the manufacturing costs, but they're pretty hard to avoid. Also, materials that are cheap now might not be if demand grows faster than supply.