this post was submitted on 17 Feb 2024
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Showerthoughts

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A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. The most popular seem to be lighthearted clever little truths, hidden in daily life.

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If a machine is never 100% efficient transforming energy into work because part of the energy is converted into heat, does it mean an electric heater is 100% efficient? @[email protected]

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[–] [email protected] 100 points 1 year ago (1 children)

Not quite. Some is lost in magnetic flux and mechanical deformation. But that is a VERY small about.

[–] [email protected] 17 points 1 year ago (1 children)

Do those not end up as heat later down the line as well?

[–] [email protected] 27 points 1 year ago (1 children)

Yes, but magnetic flux causes radio waves and there isn't a guarantee these will turn into heat in the space you are heating.

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[–] [email protected] 73 points 1 year ago* (last edited 1 year ago) (1 children)

Yes, but, it is also possible to achieve greater than 100% efficiency in using electrical energy for heat. You can use electricity to move heat from where you don't need it to where you want it. The amount of heat energy you move can be greater than the amount of electrical energy put into the system, so it's greater than 100% electrically efficient. It's well below 100% thermal efficiency, of course.

[–] [email protected] 61 points 1 year ago (4 children)
[–] [email protected] 14 points 1 year ago (1 children)

Same link with site tracking removed: https://youtu.be/7J52mDjZzto

I am not a bot, and this action was performed manually.

[–] [email protected] 7 points 1 year ago

Here is an alternative Piped link(s):

https://piped.video/7J52mDjZzto

Piped is a privacy-respecting open-source alternative frontend to YouTube.

I'm open-source; check me out at GitHub.

[–] [email protected] 13 points 1 year ago* (last edited 1 year ago) (1 children)

THIS IS THE COMMENT THREAD YOU WANT TO LOOK INTO.

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[–] [email protected] 11 points 1 year ago

KNEW it was gonna be the technology connections video.

was literally just talking about, and recommended this video, IRL like 10 minutes ago.

[–] [email protected] 6 points 1 year ago

Here is an alternative Piped link(s):

https://piped.video/7J52mDjZzto?si=i57lMtNvpoLUxKGK

Piped is a privacy-respecting open-source alternative frontend to YouTube.

I'm open-source; check me out at GitHub.

[–] [email protected] 59 points 1 year ago* (last edited 1 year ago) (4 children)

Technically, yes. Even the internal resistances outside of the heating elements eventually radiate into the space. Since the purpose is space heating, it's not a waste product and they can be roughly considered 100% efficient.

The reason heat pumps are more efficient (i.e. around 300% or more) is not that they create more heat from the same amount of energy but because they concentrate and move existing heat from one source to another.

[–] [email protected] 18 points 1 year ago (1 children)

This is correct, but it's also, it's only 100% of the heat at that point in the circuit.

Technically, using natural gas to make electricity, then sending that electricity to an electric heater would be less efficient than burning that natural gas for heat at the source.

So it depends on where you start counting from.

[–] [email protected] 14 points 1 year ago

True, and also the transmission losses between the power plant and your outlets are also factors. I just treated the question like a high school physics one where you're allowed to disregard air resistance. lol

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[–] [email protected] 41 points 1 year ago

Yes, but a heat pump for heating is somwhere from 200% to 500% efficient.

[–] [email protected] 37 points 1 year ago (1 children)

Yes, except a heat pump is capable of being more than 100% efficient because the using the power to move heat around is more efficient than converting power directly to heat

[–] [email protected] 7 points 1 year ago (1 children)

but but muh thermodynamics

[–] [email protected] 7 points 1 year ago

I get you are joking, but incase someone doesn't see the /s. As the top comment said it's easier to move heat around than creating it. Regardless if it's warmer or colder outside there's still energy there that we can use.

It's easier to move your clothes from the laundry basket to the wardrobe, than to go out and buy new clothes (or is it?).

[–] [email protected] 22 points 1 year ago (4 children)

Essentially all electrical devices are, in addition to whatever else they do, also basically 100% efficient space heaters. A PC running on 300 watts is doing things with that 300 watts but it all ends up as heat, the vast majority of which stays in the room. A light bulb puts out light, but little of that light leaves the house, it's all getting reflected and absorbed until it's mostly a heater in your house.

[–] [email protected] 12 points 1 year ago (3 children)

Consuming energy to do something the device isn't intended to do is the definition of inefficiency. You've basically redefined efficiency so as to make it meaningless.

[–] [email protected] 11 points 1 year ago

What are you confused about?
That's why they phrased it "also basically 100% efficient space heaters."

Every electric device is a something% effective whatever work they are meant for device, but ALSO a 100% effective space heater.
That second part is meaningless to the devices normal function, but very relevant to the post question.

[–] [email protected] 7 points 1 year ago

They didn't redefine efficiency. They changed the purpose scoping.

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[–] [email protected] 19 points 1 year ago

Heaters sometimes produce a little light or sound, so not 100%, but very close.

[–] [email protected] 14 points 1 year ago (1 children)

There's an interesting aspect of this that I have not seen mentioned yet. While this is true you are usually better off using your residential heater rather than an electric space heater because residential heaters are frequently over 100% efficient. That is, they deliver more heat for the energy expenditure than if you had converted the energy directly by redirecting ambient heat. Heat pumps are this same principle taken to the extreme.

[–] [email protected] 6 points 1 year ago (1 children)

But there's a flip side to that as well - if you've got heat pump heating your whole home but you only really need to heat 1 room, you may be "wasting" a good chunk of that bonus efficiency.

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[–] [email protected] 11 points 1 year ago* (last edited 1 year ago) (1 children)

But you can heat an area with 'better than 100% efficiency' if you use a heat pump and move heat from one place to another. Coefficients of performance (cop) of about 2.5 I think are pretty common, meaning if you put 100 watts into moving heat, the area will get 250 watts warmer.

[–] [email protected] 4 points 1 year ago

Total amount of heat for the entire closed system does not increase over 100% of energy used to drive the heat pump. Like you said, you just moved heat around

[–] [email protected] 10 points 1 year ago (1 children)

tl;dr, yes If you want to watch a 20 minute video about it instead of 1 word answers, https://youtu.be/V-jmSjy2ArM

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[–] [email protected] 9 points 1 year ago

Only in the sense of releasing heat into the surrounding environment. But for instance, an electric boiler is not 100% efficient because not all of the heat goes to the water. The heat that doesn't go to the intended recipient of the heat is treated as loss.

[–] [email protected] 7 points 1 year ago

Yes. The end form of all energy is heat.

The problem is that heat is a high-entropy source of energy. As a result, the losses come when you try to convert all that delicious heat back into electricity (like with a steam turbine). The "efficiencies" only go one way (and I put efficiencies in quotes because, as you pointed out, getting energy into the form of heat is inevitable, whether that's the form you wanted or not)

[–] [email protected] 6 points 1 year ago

I so want this to be true, but dont they produce radio waves?

[–] [email protected] 5 points 1 year ago (2 children)

I believe, in terms of work, that would be 0% efficient. You're basically going all-in on entropy.

[–] [email protected] 6 points 1 year ago

You’re basically going all-in on entropy.

We all do that eventually.

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