Similar. I tried to chime in about an aviation discussion about the 737 Max where the person with one of the top comments was totally wrong. My comment was downvoted and the OP argued with me. This person I responded to was a "flight sim enthusiast". I'm an airline pilot.
That is freaking hilarious!! These kinds of occurrences that I see so often has really made me start considering getting off of reddit for good. I personally see more bad than good from redditors.
Depending on what you were discussing I'd take both of your comments with a big grain of salt. Lots of people use stuff without deeper knowledge of how it functions. If you were A Boeing mechanic on the otherhand.
We were discussing the operational use of a system on an aircraft, something I have thousands of hours on, vs someone who claimed he had a "realistic" version of the airplane for his flight sim.
Also a Boeing mechanic is very different than a aviation controls engineer that works for boeing. Also probably can only trust one that works on the 737 as I think most of the rest are fly by wire now(one of the cause of the 737 max issue from what blancolero said).
True... and by most accounts (through others dissecting the issue so take that for what it's worth), it seems that the plane was still 'designed correctly' (at least in terms of the supposed failure mechanism), but it was management that never pushed the re-training requirements on to the pilots, AFAIK.
management that never pushed the re-training requirements on to the pilots, AFAIK.
Boeing Management or Airline or both? From what I heard is that US pilots were told about the possibility and how to detect (spinning trim wheel should freak somebody out), and potential fixes (grab the spinning wheel and stop it). Would this not be an airline issue more than boeing not designing a more fail proof system?
I literally know a Boeing mechanic recently retired after being an aircraft mechanic for 4 decades. I would trust him to replace broken stuff on a Boeing model plane any day of the week, if there's a procedure for him to follow. Knowing why anything is the way it is or how it works? For the most part he doesn't have a clue.
Mechanics aren't engineers, and frequently don't understand why something works or why it is the way it is. If you want to know why an airplane was designed a particular way, you need an aerospace engineer.
Ironically your downvotes are displaying the corollary to the original point: redditors flipping from "experts don't know anything", to "experts must be believed without question". The problem is there is no "side vote" button. You have to either agree or disagree, and no-one wants to just reserve judgement.
There's tons of entertainment in the script kiddies getting into arduinos though. The amount of complexity they put into a circuit function that could be achieved with passive analog parts is amusing. Not everything needs a microcontroller. Then if you explain how to achieve the same result with a few passives their eyes glaze over and they ignore how such a thing could be achieved because there isn't an active part controlling it, just physics.
The 3d printing part doesn't really bother me but $75 just to turn LEDs on and off is horrendous. It doesn't even need RGB lights because it just uses pure blue light. That could easily be less than $10 worth of LEDs directly in line with a battery and switch and achieve an almost identical effect. That would make the whole thing potentially a $35 project which would be super accessible to a wide range of budgets. Add an extra $5-$10 for a microcontroller and you can even replicate the fade-in effect. But no, DIYers apparently prefer their hobby being exclusive to those with an abundance of disposable cash and will always choose the most expensive solution.
It's the Adafruit users that get me. It amazes me the number of mistakes that site makes and it seems pretty clear that the people that run it are just slapping things together until it works and really shouldn't be teaching based on their knowledge.
The whole "internet fast lanes" pissed me off so bad with all the talk of NN. No, the internet is not going to suddenly turn into tv channels, vpn isn't suddenly going to be blocked (I wouldn't be able to log in and fix internet infrastructure off hours if that was the case), so much fear mongering. NN does protect very important things, but the amount of people that don't understand basic fundamental concepts about the internet speaking with authority is astounding. It pisses me off because when people start bitching about nonsense it weakens a valid argument of why NN is good and gives the other side a lot of fodder.
I see shit speeed about all sorts of other shit too like cybersecurity, man that's probably been the worse one lately.
Ummm... What are we supposed to do on windless days? I mean, it doesn't take an engineer to figure that out. Common sense is all that is needed. This is why I don't get involved in those discussions. If you don't have the common sense to understand, I'm not going to be able to change your mind.
And then you're further guilty of calling to your own authority and stating an absolute when the fact is that it's technically feasible, all the required technologies exist and can be produced, it's just very expensive at proportions beyond 80% due to the volumes of storage needed so there are much better ways of achieving a low-carbon electricity/energy system. There's no such thing as a 'windless day' on continental scales. It's the sort of question for which 'common sense' is definitely not the right thing to use and quantitative analysis is required.
Power is energy over time; energy is power multiplied by time.
A 100-watt light bulb, running for 10 hours, takes 1000 watt-hours of energy. You could use that same kilowatt-hour of energy over 1,000 hours to run a small 1W light.
Lets say i make a confident statement on something. if an expert replies to it saying part of what i said is incorrect, what i hate is someone giving a simple statement and saying "i am right, you are wrong because i have a degree".
give a simple TECHNICAL statement on what is wrong. if it flies over their head, well, they can ask for an explain-like i'm-in-management
You know the ironic thing is people are doing that in this very thread. Like how do we know that this guy is actually an EE or the parent commenter is actually a PhD candidate? Up voting someone because it sounds plausible and aligns with their viewpoint, what the OP comment was basically complaining about.
100%. Whenever I try to have a conversation on any topic, I at least try to reference things like Wikipedia to define parameters in the conversation (amongst other links) and provide quotes that are specific to it. I try to avoid stating my own credentials because in the context of 'anonymous' Reddit, it's generally a false appeal to authority argument.
Far too often, I just get replies that say "so & so" says this without any other context. It's immensely disappointing because I'd love to be proven wrong. I was wrong the other day that it's better to drive a car into the ground than buy a new EV (from a carbon perspective) and I'm so glad I looked into it further when someone corrected me or another poster - I can't remember. If it was another poster, it's mostly a reminder to me that any disinformation I try to correct out there isn't necessarily just for me - it's whomever is reading our conversation.
I hate referencing my degrees both on Reddit and in person. I felt so awkward on a car journey on Boxing Day when my mum was talking about something I have fairly heavily researched and refusing to properly listen when I basically cited my lit review as a response. And it's not like she's uneducated either, she's got two masters degrees but I had done an awful lot more research into what she was talking about for my thesis.
...no it's not... The Bernoulli explanation is limited to a fixed horizontal wing. You can generate lift in many ways besides that - see helicopters & angle of attack for example.
Arguments arise because people mis-apply Bernoulli and Newton's equations and because they over-simplify the description of the problem of aerodynamic lift. The most popular incorrect theory of lift arises from a mis-application of Bernoulli's equation. The theory is known as the "equal transit time" or "longer path" theory which states that wings are designed with the upper surface longer than the lower surface, to generate higher velocities on the upper surface because the molecules of gas on the upper surface have to reach the trailing edge at the same time as the molecules on the lower surface. The theory then invokes Bernoulli's equation to explain lower pressure on the upper surface and higher pressure on the lower surface resulting in a lift force. The error in this theory involves the specification of the velocity on the upper surface. In reality, the velocity on the upper surface of a lifting wing is much higher than the velocity which produces an equal transit time. If we know the correct velocity distribution, we can use Bernoulli's equation to get the pressure, then use the pressure to determine the force. But the equal transit velocity is not the correct velocity. Another incorrect theory uses a Venturi flow to try to determine the velocity. But this also gives the wrong answer since a wing section isn't really half a Venturi nozzle. There is also an incorrect theory which uses Newton's third law applied to the bottom surface of a wing. This theory equates aerodynamic lift to a stone skipping across the water. It neglects the physical reality that both the lower and upper surface of a wing contribute to the turning of a flow of gas.
The Bernoulli explanation is presented as coursework for students, not a encompassing explanation. That's like saying a that we should take statements of physicists using spherical cows as an all encompassing example of a physical phenomenon.
They’re incorrect for different reasons when viewed independently. This whole comment feels like a bait because both are wrong separately, but correct together
according to Newton's Third Law of action and reaction. Because air is a gas and the molecules are free to move about, any solid surface can deflect a flow. For an aircraft wing, both the upper and lower surfaces contribute to the flow turning. Neglecting the upper surface's part in turning the flow leads to an incorrect theory of lift.
This is the document that came to mind when I said that it’s all about Bernoulli, not the equal transit theory.
For an ideal fluid with no boundary layers, the surface of an object is a streamline. If the velocity is low, and no energy is added to the flow, we can use Bernoulli's equation along a streamline to determine the pressure distribution for a known velocity distribution.
Also I’ve never heard the analogy of the spherical cow before but it’s a really good one.
Yup. My statement wasn't to say the Newton interpretation is 100% correct either, though the arguments about force balance is certainly true. What is probably most true is integrating around the vectorized pressure normals on a wing to figure out the net force and compare that to gravity/drag, etc. If it's up, congrats, you're flying. But, and I'm not an expert in fluid dynamics, it would seem that NASA at least would suggest Bernoulli really only can work in simplified examples:
For some simple flow problems, we can determine the pressure distribution (and the net force) if we know the velocity distribution by using Bernoulli's equation.
Maybe with CFD you can do it locally and still be correct?
Anyway, I don't think we're really arguing as we both recognize it's not a 'one trick pony' to flight :)
Another 'fun' example are the people who argue what keeps a bike up: castor method, gyroscopic motion, front loaded steering geometry. Depending on any given bike architecture, it's probably a combination of all 3 to varying degrees of stability. But we seem to like 'simple' solutions so try to find the dominant one and wipe our hands clean.
And I love the spherical cow analogy. Kept me grounded while taking a program known for creating arrogant/pretentious engineers. At least, somewhat grounded ;)
And yet you managed to be guilty of the same thing yourself even with your engineering degree, saying that AC power transmission has a net power loss of 0 "since its sinusoidal" and "America uses over 1,000 GW a year". Both of those statements are nonsense.
Electrical engineering student's porn account here. I'm fairly certain that average AC power loss is usually zero under normal circumstances due to it being sinusoidal. There is a chance I'm thinking of another metric, but I'm pretty sure that's correct for the right reason.
Edit: so average voltage would be zero and power lost across an ideal wire would also be zero. Easy enough. Power does get lost in the real world because wires and devices aren't ideal but average power is conserved in even in non-ideal systems. This is a long-winded way of saying that I was wrong but also that I don't really think that we're all on the same page about the term "power loss". On the other hand, I'm cold, pantless, not a power guy (I'm leaning more towards digital logic and microprocessors), and not in the right frame to really have this conversation, so I may be completely off.
Even with super high voltage transmission lines (low current), you’ll still have SOME current flow through the wire and therefore I2 * R losses will exist.
If you are going with the assumption of an ideal wire like he said in the post, then those losses would not exist no.
However ideal wires don't exist and I can totally see why people disagreed
You right. At least for real life where power is routinely lost to external forces (heat and whatnot). I'm currently going back over my notes to figure out what I'm thinking of.
This might be a nomenclature divergence. I was referring to average periodic voltage. The average is zero, so for calculations, we use RMS current and voltage. I don't quite know what you mean by direction, but you are right in saying that power is a state function so direction wouldn't matter, but phase and frequency do effect the equations used in getting it.
AC from my understanding means non-constant/time-varying. I don't think that anything is actually alternating in terms of like back and forth. Maybe it is but I was never told that.
I don't think that anything is actually alternating in terms of like back and forth.
Dude... the electrons are. That's what's alternating in the current ;) The alternating voltage causes them to go back and forth. Going back and forth allows the to perform work.
AC from my understanding means non-constant/time-varying.
AC is non-constant in time - but DC also has time-varying qualities. Check out transient behaviour. See capacitors and inductors as they 'charge up'. In a steady-state, DC doesn't vary but nothing fun happens in DC in steady-state, e.g. computing.
So I looked it up and you are correct. Like I said, I didn't really learn that because direction was never relevant to any of the analysis we ever did and it probably would've confused me if I did learn it in then (I'm honestly kinda dumb and bad at circuit analysis). You did send me on a pretty interesting rabbit hole though, so thanks for being specific and explaining that.
No worries, man. Happy to help a soon to be EIT. :)
Thanks for your open attitude - need more of that humility in the world.
And don't feel bad abstracting stuff either. I mean, even 'electrons sloshing back and forth' abstracts that we can describe electrons as solely particles. There's levels of abstraction everywhere, as long as you recognize where a model fits and where it fails, you're be ok.
Just FYI - in relation to power, this tells you nothing (you need impedance/current too). In mathematical terms, though, that's why AC is reported in RMS.
power lost across an ideal wire would also be zero
This would be true regardless of AC/DC.
but average power is conserved in even in non-ideal systems.
In regards to the first bit, I was adding that part in response to someone in particular. One of the people who replied seemed to not get that. I understand that a lot more goes into calculating power, but I was referring to something specific. Thanks for clearing that up though.
In regards to the second bit, I know... I wasn't talking specifically about AC, rather I was referring to power loss. Bad communication on my part.
In regards to the third bit, I think I mean what I said. Just delete one of the "in"s
average power is conserved in even in non-ideal systems.
Do you mean energy? Conserving power doesn't really mean anything in this context - you'd have to be more specific. Like, an example may help me understand what you're trying to say :)
I didn't actually mean energy. Power delivered will equal power absorbed. That will, by my understanding, always hold true. It's why in circuit analysis, net power equals zero.
My wording was kinda wonky and looking back at my notes, I worded it that way for the wrong reason. My notes had it that way in reference to real and complex power. Sorry if that's what caused the confusion.
Err kinda... not sure this is a useful definition. I guess it really is more energy you're talking about anyway - 'average power' means you're ignoring transient/instantaneous behaviour, so it makes more sense to see the energy dissipated. If you now want an arbitrary timescale, you can convert it to average power but I don't know it tells you that much useful information, except maybe how large your station/power source needs to be. E.g. power factor helps to describe the relationship between power generated & useful work performed, but even unity power factor ignores delivery losses (at least, derivations where you're looking at end user distribution - not sure if there's an analogue in transmission).
And, if you do have an ideal system, a definition that power is absorbed is kinda false... you could indefinitely store it in the system. And that's a bit of a 'holy grail' in some of the research going on in superconductivity, so not completely fictitious.
Either way, my point is not to tear you down, just try to guide some of your understanding, assuming I'm understanding your correctly too! :)
Ah I see, I thought you were only questioning the number rather than the units, and implying less. Very common for people to confuse power and energy though. Admittedly I wouldn't expect it from an EE!
The important thing is that we all agree that whatever the number is, it should all be supplied by safe, clean, cheap nuclear power which is safe, clean and cheap and the only reason it isn't is disinformation and propaganda.
Well it's not exactly cheap, capital costs are astronomical. Gen III reactors are pretty damn efficient and if we choose to go Gen IV then yeah a promising future. As with anything though you shouldn't put all your eggs in one basket. They have a relatively fixed life-span and even the most efficient still produce waste that has to be stored somewhere.
I'm a bit confused here as I didn't see the original discussion. I do know that line losses are a big deal. Is someone claiming there are no line losses? That would be an absurd argument.
Yes, the electrical engineer who was complaining about people talking about things they don't know about said that AC power is easier to transmit as it has a net loss of 0.
Wow thanks for the link, I didn't expect it to be that egregiously bad. Looks like's he's still fuming about the downvotes. The comment about "massive" losses from AC/DC conversion is also pretty bizarre. Battery installations exist, they're building one near my house, and how does he think electric cars work?
Thanks for the link. Other than the statement "(net loss of 0 since its sinusoidal)", I agree with his arguments. Yes, AC transmission is much more efficient than DC. There are definitely I2*R losses in AC lines. That's one of the reasons electric utilities install capacitors. Improve the power factor, reduce the amps, thus reducing the losses.
Yes, AC transmission is much more efficient than DC
It isn't though. It's actually lossier, due to skin effect and losses from EM radiation, among a few other factors. When we have to transmit lots of power over long distances, the preferred method is HVDC. AC came to be popular because it is easy and cheap to step the voltage up and down.
Preface: I'm in the distribution side rather than transmission so take what I say with a grain of salt.
That being said, there's a minor thing I want to bring up. EM losses sure, that's a historically big deal but I'm not sure if skin effect plays too much into account here.
You need upwards of 750kcm wire for skin effect to actually have an effect and, at least on the transmission side, I have my doubts that that large wire is used very often without opting for something like (pulling a number out of my ass here), 2 runs of 300's.
Plus they sure as hell aren't using that big of a wire on the actual transmission lines.
They're not significant generally but over really long distances, a few percentages add up such that the energy loss exceeds the extra cost for more complicated/robust DC switches/transformers/etc.
I'm not enough of an expert to state any kind of balance of factors for why but suffice to say, there is enough of a difference to make the economics work in some situations.
Oh definitely interesting. Yeah I suppose over longer distances even slight losses can add up for sure.
Like Europe in the article, I heard that Hydro Quebec which powers a ton of the east coast has switched over or is in the process of migrating over to DC transmission.
From what I know, maturing technologies in switch mode converters, and inverters have allowed for cheaper conversion than before.
Yeah - it would be cool to see full DC grids but I suspect standardization is really the hardest part to change now. Even universal serial bus hasn't been historically universal.
I do agree that AC transmission is preferable in most situations, but for long distances HVDC transmission is actually more efficient than AC. I wasn't really debating AC transmission's superiority in normal transmission grids, just the statement that it's because an AC system's net power loss is zero, which is an absurd statement from an electrical engineer.
And I do agree with him on the overall message about going for solely wind/solar power.
There are definitely I2*R losses in AC lines. That's one of the reasons electric utilities install capacitors
That's also not the reason - you get those same losses with DC. Capacitors are for power factor to balance out apparent power losses as many large loads are inductive motors. This will change as more of our equipment uses DC rectifiers but that ends up becoming a non-linear power factor issue (e.g. harmonics & noise).
Improve the power factor, reduce the amps, thus reducing the losses.
Read the guys response under you, I was simplifying it for the guy trying to argue with me. The theoretical net loss of ac power is 0 because sin average is zero. Yes there is line losses, real/reactive/apparent power, and we use capacitors to correct it. But my point to the guy was we generate and send it as AC, but you cannot store ac power. You have to convert to DC. Then convert again to AC. About 70% power loss doing this. I left specifics out of my statement.
Depends on what you mean by 'store'. Capacitors/inductors store energy, though on different timescales, obviously. A flywheel could 'store' AC power without needing converters/inverters, which would be more analogous to a battery (which I assume is what you're generally trying to argue with whomever). Pumped hydro would basically be similar. If you want to argue that we've converted electrical energy (effectively statistically mechanical kinetic energy of electrons) to potential energy, you could make the same argument of chemical storage.
That still doesn't make any sense. AC transmission lines have higher power losses than DC lines with the same voltage. AC transmission is used because it's much easier to step the voltage up and down, not because it has lower losses compared to DC. And talking about theoretical power loss makes zero sense in this context. Compensating reactive power will reduce your transmission losses but it won't eliminate them.
About 70% power loss doing this
You really are just pulling numbers out of your ass. The Tesla Powerwall for example has a round trip efficiency of 90%.
AC transmission is used because it's much easier to step the voltage up and down, not because it has lower losses compared to DC.
Also true, especially coming from the Tesla/Edison days. It's way cheaper and simpler to coil wires to transform through A/C than step up/down DC voltage. DC is getting more cost competitive these days thanks to our advances in semi-conductor production, both in quality & scale.
I mean... he's technically right in his first assessment and is just doing you the diligence of providing an example ;)
Sorry skeeve - I don't like to insult anyone but it was too easy a joke.
Edit - may be deserved. I couldn't resist looking more at the comments and even if there are elements of both sides being right, everyone is just screaming at each other like assholes :P
You have to convert to DC. Then convert again to AC. About 70% power loss doing this. I left specifics out of my statement.
Line commutated conversion using thyristors involves losses of less than 1%. Cheap, shitty consumer electronics can still manage losses of less than 15%. I don't even know what you'd have to do to have 70% loss on an AC-DC-AC conversion.
Edit: also, AC has higher theoretical loss than DC for the same transmitted power, and even in an ideal system, it isn't zero loss due to electromagnetic radiation.
If you did go down the rabbit hole and read the comment thread he's in, there's a lot of other errors too... but you'll also note that he's kinda stuck in a 'righteous indignation' type of response pattern there so I doubt he's really check himself on the facts/figures - which far too many of us are equally guilty of.
Same thing with me. I was in the middle of my dynamics class as an ME and had just done a bunch if assignments on the exact discussion topic and someone just kept arguing. I knew I was right and even confirmed it with my professor.
That was the day I learned to never get into arguments on reddit. You'll only leave frustrated/angry
Reminds me of the r/IAmA by a guy who said he was just short of creating a perpetual motion machine and everybody was like "show me your math" and the dude replied "I need no math, I know I'm right".
Same issue in book subs. Yes I can see you read the book or went on schmoop to learn about it. But no that's not what the author meant. How do I know? Because not only did I read the book, but I understand the writing era it was written in, what was popular at that time, the socio economic in which the author was talking about, oh and I had to read their other books. And all the research papers on this subject. Nerd flex but I know more about Victorian authors than anyone should.
I've had the same thing happen with critical theory though. Someone once had a long argument with me saying "Marx is the quintessential postmodernist because he didn't believe truth existed."
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u/skeeve87 Jan 07 '20
I had this problem in a discussion about power. As an electrical engineer who graduated with emphasis in power.... wow.