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Comment by askvictor | Hacker News Reader

A friend who is a materials engineer told me that there aren't enough rare-Earth metals in the world to supply the demand for magnets to replace all of the current petrol based cars with electric cars. No sources unfortunately, but this thing might not scale.

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That's part of the reason why practically all electric cars currently in production use induction motors, which only require copper.

Yes, it would require more rare earths than are currently economically feasible to mine if we replaced every fossil fuel engine with a permanent magnet electric motor of equal power.

The only real difference between the two is the design difficulty of the drive circuitry for the VFD to run the induction motor. That's largely a solved problem.

I think it's likely some other resource might be a constraint in that tight a timeline though. Either something for the cars themselves, or the infrastructure for charging them.

Do you have any reason to believe that?

Almost all car charging is done at night, when grid load is far lower. Charging will not be a problem, and there is no material shortage likely in the near future.

Just the ban being 5 years out.

I've certainly run into homes that couldn't add a clothes dryer circuit without major renovation involving the city.

Not saying it will be be an issue everywhere, but the span is too short for it not to be an issue in many places.

Given the short time frame, proof that there aren't issues would seem more prudent. Whether that's manufacturing capacity for batteries, or grid shortfalls in certain areas, or whatever.

Brand new flat or house built today in Madrid, Spain are fitted at best with a 20A connection. The standing charge alone is more than what I pay for electricity (standing charge and consumption) in a 2 bed flat in London. The vast majority of flat and house I have seen in Spain have 15A or 20A. That includes city, and country houses.

It is a cost cutting measure rather than an infrastructure limitation (people chose a 20A connection because of the standing charge cost) in the newer building, but I suspect that if a significant portion of the population need to double their contract and maxed it out during the night, there is going to be some work needed.

Seriously, 20A? How do you even run an air conditioner on that, much less an entire house? 200A (at 240V split phase) is standard here in the Midwestern US. It's easy and cheap to get more if you want a better connection, such as for an EV or a home shop with welders and large motors.

> Seriously, 20A? How do you even run an air conditioner on that, much less an entire house?

The poster mentioned Spain, which uses 230V (unlike the USA, which uses 120V), so 20A should be around 4600W if I did the calculation correctly. With a quick search I found a window AC with 18000 BTU using only 1700W, so even with 15A it would be possible to run one AC with plenty to spare.

The USA uses 120V for outlets and lighting, but most buildings have what we call "split phase" where 240V is available between two opposing sine waves. A neutral down the middle gives you 120 from either of these phases. Large appliances run on 240V dedicated circuits, the rest are 120.

And 4600 KW is only a couple tons. You'll need more than that for a 5-ton central HVAC to cool an average house in a hot or humid area.

What's a ton in this context? I'm hoping it's not the mass of the unit, but what do I know.

No, as the other poster pointed out, the US is 240 volts not 120 for this discussion. 120 volts is what you get to your general use outlets, but when we say a house in the US has 200 amps of mains service, we mean 200 amps at 240 volts, or 400 amps at 120 volts. The split to 120 volt happens in your mains panel after the main breaker.

> How do you even run an air conditioner on that, much less an entire house?

My guess is "they don't". A quick web search reveals less than 50% market penetration in homes of air conditioners.

That said I live in an apartment with 30A 100V service, and I've run 3 air conditioners at the same time no problem.

20A? In USA, 200A is not uncommon. Some cities in the bay have 100A service minimum in their building code..

UK houses are generally 50A, single phase.

Batteries, but that's why a lot of money is currently being invested in battery R&D and mass production.

Too bad your materials engineer friend has no idea that the most hyped EV car company, Tesla, doesn't even use rare earths in its motors because they're all induction motors.

And you could of course replace the copper with the incredibly plentiful aluminum, which actually has superior conductivity per unit mass to copper. (Copper is nice because it's volumetrically more compact and is easier to make electrical connections with, but if it were seriously in danger of a shortage, none of these are anything like showstoppers to switching to aluminum.)

TIL... I had just assumed that rare earth motors were more efficient and would be preferable in electric cars. I'll pass that on to him.

It depends on the Tesla.

the Model S and X use induction motors. The Model 3 uses a permanent magnet motor:

https://www.edmunds.com/car-news/auto-industry/2017-tesla-mo...

That's very interesting, thanks.

There's a real question as to whether we'll have enough copper, too.

I wonder if we can "mine" all of the old copper wires (telephones, etc)?

It's actually a problem with people breaking into unused houses and ripping out the wiring. Or stealing other metal.

Scrap yards in my state (and I'm sure many others) are required to take identification from anyone that sells them metal.

Copper recycling can be quite profitable. Enough so that people rob houses under construction just to recycle it for cash.

There is a very lucrative black market in "recycled" copper. It's been known to be stolen off trucks by the tonne.

World production is almost 20 million tonnes annually so that shouldnt be an issue. Its also not like electric cars use that much more copper than normal cars: normal cars have both a starter engine and an alternator plus all the engine wiring.

Also, electric motors can use aluminum wiring, and many induction motors have aluminum rotors since they can be cast at a lower temperature than copper.

So use aluminum, which has better conductivity per unit mass. And is essentially inexhaustible.

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