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Comment by imbusy111 | Hacker News Reader

I couldn't get past the first two paragraphs without the article losing all credibility.

> And although there are many different kinds of electric motors, every single one of them, from the 200-kilowatt traction motor in your electric vehicle to the stepper motor in your quartz wristwatch, exploits the exact same physical phenomenon: electromagnetism.

Well, basically your whole experience of the world is just electromagnetism, nothing more. And electrostatics is part of electromagnetism theory.

> In some applications, these motors could offer an overall boost in efficiency ranging from 30 percent to close to 100 percent, according to experiment-based analysis.

What practical electric motor is even close to 30% efficient? This is laughably low.

Edit: it's BOOST over the current efficiency.

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> What practical electric motor is even close to 30% efficient? This is laughably low.

I think that means 30% over existing performance.

Got it, missed that part.

Still, assuming efficiency can't get past 100%, 100% boost can be achieved only on something that already has only 50% efficiency.

I assume that they are looking at in laymans terms, and saying that if an electromagnetic motor is 80% efficient, an electrostatic motor could increase efficiency of the remaining 20% by 30% to 100% (86-100% total efficiency). Not that it makes any sense, but I think that was their intention.

i wish people would just always use percentage points and never deviate from that.

I wish people would just explicitly state they can't believe their eyes that 100% efficiency can be asymptotically reached, i.e. no known law of the universe prevents us from building electromotors that are 90%, 99%, 99.9% etc... absolute efficient.

Then we could just remind them that Carnot efficiency does not apply to electrical / mechanical energy conversion.

This is absurd, detecting that a wrong interpretation is inconsistent (because it would result in overunity violation of energy conservation) and instead of rejecting the misinterpretation of the parent, concocting an even more convoluted interpretation.

All because people refuse to believe 100% energy conversion between electromagnetic domain and mechanical domain is impossible?

Turbosets have been doing this for a long time already, the Carnot efficiency limit does not apply to non-thermal energy conversions...

THey are in fact talking about absolute efficiency.

Conventional electromotors are designed with high efficiency... at a certain range of RPM and torque. For lower RPM's permanent magnet electromotors suffer dramatic decreases in efficiency and torque, unless you use a gearbox, which also produce heat due to frictional loss.

These electrostatic motors can achieve quasi reversible performance (i.e. asymptotically close to 100% efficient, not a violation of thermodynamics, since neither electrical nor mechanical energy are thermal forms of energy).

Turbosets also reach nearly 100% conversion efficiency.

Electrostatic motors started their niche with miniature motors, since they were more compact and it becomes progressively harder to miniaturize winding coils. Where a simple electrode surface would be more space efficient.

Pay attention to Macroscale in the title, its these miniature-niche low RPM motors slowly capturing larger torque and higher RPM lebensraum from the gearboxed permanent magnet electromotors.

Also, piezoelectric motors are a thing - sure, they're super tiny and for specific purposes (very fine movement), but beyond the fact that they use electricity to generate the vibrations that they then use for movement, I don't think it would be considered "electromagnetic".

Actually, in that same vein would be a Nitinol or similar "shape-memory alloy" motor - run power through it to have it change shape, then remove power to let it relax.

So yeah, unless I'm misremembering or grossly misusing terms, "piezoelectric" and "thermoelectric" electric motors both exist...

Yeah, that was some poor quality for IEEE. I'm pretty sure they confused "electromagnets" and "electromagnetism."

As far as the "boost in efficiency" sentence, I reread the paragraph around it several times and still have no clue WTF they are trying to say.

Spectrum is aimed at the general public and its articles are often university press release quality.

> I reread the paragraph around it several times and still have no clue WTF they are trying to say.

some advice: next time you don't understand some article, consider the possibility that it is not a case of:

> Yeah, that was some poor quality for IEEE. I'm pretty sure they confused "electromagnets" and "electromagnetism."

but that the problem might be your lack of understanding that you already detected. it's a press article, it can't teach you an undergraduate course in physics condensed to a few paragraphs of text...

I have taken several undergraduate courses in physics. If you have some clue what they are saying with:

> In some applications, these motors could offer an overall boost in efficiency ranging from 30 percent to close to 100 percent

please illuminate. Brushless DC motors across a wide variety of applications already exceed 50% efficiency. Perhaps there are applications in which they cannot reach 50% efficiency, so a 100% boost in efficiency would be possible.

The key is “in some applications.” Not in all applications. There are areas where brushless DC motors are inefficient, these are better in those areas - my guess is low speed, high torque use cases.

A) that's the sort of thing I wish the article had mentioned.

B) I know it's research, but low speed high torque situations usually involve a reduction gear-set. They make some surprisingly compact ones these days.

B) Yes, which involve losses and packaging changes. Exactly why a motor like this would be useful…

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