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A lightning bolt would be worth only about a nickel (2015)

engineering.mit.edu

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Re: A lightning bolt would be worth only about a nickel (2015)

#101

Post by a9h74j »

pxndxx wrote: post #45
a9h74j wrote: post #6

Earlier quoted context omitted.

Yes, and the Wired graphic was particularly misleading in that it showed, as I recall, multiple dollar amounts accumulating on per-session treadmill displays. On the other hand, it is possible to imagine lifestyles enhanced by various 10W contributions. 10W for heated clothing. 10W for a laptop. 10W average to power a several km electric bicycle or Aptera-size commute. And so on.

How are you proposing we produce 10W to heat clothes? we produce around 80W just by sitting idle, just wear insulating clothes! How do you produce 10W to power an electric bike? 10W is a laughable amount of power, just get rid of the electrics and pedal a bit. 10W is barely enough to charge a phone these days. Anything that gets moderately hot while in use is consuming more than 10W.

e.g., s/lifestyles/post-collapse lifestyles/

Based on Ali Express, heated clothing (5V power in a pocket) is popular enough in China.

Re: A lightning bolt would be worth only about a nickel (2015)

#102

Post by andrewla »

jfim wrote: post #94
andrewla wrote: post #76

Earlier quoted context omitted.

You're using a toy example to strawman the Joule counterpoint. How much do you use in a month, which is the typical billing cycle? Off-peak vs. on-peak cost?. In the end there's no practical utility to this. We just pretend that we're living in a world where you get a 100W light bulb and know exactly what it will cost you, and not a world where half your bulbs claim to be 100W but are actually 14W with 100W-incandesc…

To take your example, your 14 Watt lightbulb would use about 0.35kWh per day if running all day, or about 10kWh per month of nonstop usage. At 0.15$/kWh, that's about a dollar and fifty cents, assuming you'd want to leave it on all day and night. All of that math can be done in your head too, if you're willing to approximate the number of hours in a day to 25 and the numbers of days in a month to 30.

I'll take one more shot at explaining why this continues to be a strawman.

Why would I be running the light all day? The assumptions being made here are unrealistic enough that the answer becomes meaningless. The realistic question here, "how much money would I save by switching from a 100W incandescent bulb to a 14W LED bulb" is not helped by any of this kWh nonsense.

Re: A lightning bolt would be worth only about a nickel (2015)

#103

Post by andrewla »

ravi-delia wrote: post #95
andrewla wrote: post #60

> The average lightning strike contains about 1 million joules, enough energy to fry the founding father in his boots. “The typical house in the U.S. has 100 amp service or about 28 horsepower,” says Kirtley. Boy do I get frustrated when using compatible units without conversion. The unit that I hate more than any other unit in the universe is the KwH, which is dimensionally equivalent to the Joule, so I don't unders…

The KwH makes sense if you consider that while units are largely path-independent, mental calculations are not. At any given moment, the sensible measure of your house's electricity usage is in kW. And to work backwards to figure out consumption, the hour certainly beats the second. Sure, you could call it 3.6e6 joules, but at that what point what does it buy you? Horsepower is clearly insane though, I have no idea w…

For most realistic conversations you'd be talking about the relative consumption of two devices. Watts/kW is totally fine for this.

Regardless, head-math or otherwise, the vast majority of people will never do this calculation at all, except maybe to weigh the relative power consumption. And if they do the math, having a calculator and having all the units be compatible with each other (so just a natural conversion of W to J/s) is totally fine.

Re: A lightning bolt would be worth only about a nickel (2015)

#105

Post by andrewla »

johnwalkr wrote: post #100
jfim wrote: post #71

Earlier quoted context omitted.

The kilowatt hour is a fantastic unit when talking about electrical consumption. Are you running a 100W load (0.1kW) for an hour? That's 0.1kWh. Running it for ten would make a whole kilowatt hour. This allows for easy calculations of how much something is going to cost in electricity, and the units are such that it's easy to do the math in your head.

Hours are usually more convenient to work with than seconds when talking about energy use (even in this case when you are comparing to other things. Plus it's the de facto standard unit more people are familiar with. Power bills, electric car capacity, and energy efficiency are all normally described in kWh.

This is true, but it is exactly what I am railing against. It's just tradition -- energy in houses is kWh, so let's use that for other things too.

Instead, let's just use Joules everywhere. Easy peasy. Why are my batteries rated in Ah -- it's not like they're providing a variable voltage source; just give me Joules.

I know this is a ridiculous hill to die on, but I will die on it!

Re: A lightning bolt would be worth only about a nickel (2015)

#106

Post by andrewla »

MonkeyClub wrote: post #93
trelane wrote: post #88

Earlier quoted context omitted.

> You're using a toy example to strawman the Joule counterpoint. Not a toy example. That's exactly how I estimate energy consumption for off the shelf devices. And for battery life (W*h but still). > 100W light bulb and know exactly what it will cost you, and not a world where half your bulbs claim to be 100W but are actually 14W with 100W-incandescent-equivalent and such. If you've lived with lighting you're respons…

Same here, I find the KWh to be a very useful unit for daily calculations of that sort, where I want a quick upper bound on things to make estimations. Last year I switched off my fully-functional 2008 workstation (a lovely Fujitsu Celsius W370 on OpenBSD, a furry joy) because of such an upper bound difference (300W vs 65W for the ThinkCentre that hides among the books on my desk's side). This sort of works in a simi…

> 300W vs 65W

A watt to watt comparison is fine. Why hours? I can tell you right now that the big one uses ~4.5x the power. Is it really that much easier to convert the time you're using the device to seconds? If you're going to multiply by the electricity cost anyway, might as well break out the calculator one step early.

Re: A lightning bolt would be worth only about a nickel (2015)

#107

Post by jfim »

andrewla wrote: post #102
jfim wrote: post #94

Earlier quoted context omitted.

To take your example, your 14 Watt lightbulb would use about 0.35kWh per day if running all day, or about 10kWh per month of nonstop usage. At 0.15$/kWh, that's about a dollar and fifty cents, assuming you'd want to leave it on all day and night. All of that math can be done in your head too, if you're willing to approximate the number of hours in a day to 25 and the numbers of days in a month to 30.

I'll take one more shot at explaining why this continues to be a strawman. Why would I be running the light all day? The assumptions being made here are unrealistic enough that the answer becomes meaningless. The realistic question here, "how much money would I save by switching from a 100W incandescent bulb to a 14W LED bulb" is not helped by any of this kWh nonsense.

Maybe your utility company bills in joules, but mine does in kWh. You can easily figure how many kilowatts your bulb does (divide by 1000), and you can come up with an estimate of how many hours you use it in a day/month/year, which is then easy to turn into an actual dollar amount.

A joule is just a watt second instead of a kilowatt hour, and the 3600 factor (seconds per hour) is really annoying to use in mental math.

Re: A lightning bolt would be worth only about a nickel (2015)

#108

Post by breakingcups »

mepiethree wrote: post #85
flyinghamster wrote: post #72

Earlier quoted context omitted.

> 100 amp service at 120V Strictly speaking, 240V. Normal electric service in North America is 240V split-phase, with the distribution transformer's center tap grounded and serving as the neutral line. We normally only use the full 240V for heavy loads like electric ovens, arc welders, large air conditioners, and such. Large buildings often use 208V three-phase power, yielding 120V phase-to-neutral, and large commerc…

Do you work in clean energy tech by any chance? Software people who know these things are like unicorns

There's probably a large overlap between software people and people who subscribe to Technology Connections: https://www.youtube.com/watch?v=jMmUoZh3Hq4

Re: A lightning bolt would be worth only about a nickel (2015)

#109

Post by trelane »

andrewla wrote: post #106
MonkeyClub wrote: post #93

Earlier quoted context omitted.

Same here, I find the KWh to be a very useful unit for daily calculations of that sort, where I want a quick upper bound on things to make estimations. Last year I switched off my fully-functional 2008 workstation (a lovely Fujitsu Celsius W370 on OpenBSD, a furry joy) because of such an upper bound difference (300W vs 65W for the ThinkCentre that hides among the books on my desk's side). This sort of works in a simi…

> 300W vs 65W A watt to watt comparison is fine. Why hours? I can tell you right now that the big one uses ~4.5x the power. Is it really that much easier to convert the time you're using the device to seconds? If you're going to multiply by the electricity cost anyway, might as well break out the calculator one step early.

I use watt when I want to compare power, and watt*hour when dealing with energy. Hours because hours are a lot closer to the real spans of time I use, and therefore much easier to calculate with. E.g. it's more common to run a 3kW AC for 3h than 3s. So, 9 kWh instead of 9 kWs (or 180kWs, for the same time span)

> If you're going to multiply by the electricity cost anyway

I don't usually convert to money. If it's a linear cost per kWh, then I can deal with that at the end or, more likely, don't actually really care.

The _actual_ cost you pay is often tiered anyway, so who knows what the price _actually_ is until you have the whole month's worth of power usage finalized. And then it's not clear what I could account to what tier.

> might as well break out the calculator one step early.

Bold to assume I use a calculator much.

Re: A lightning bolt would be worth only about a nickel (2015)

#110

Post by Schroedingersat »

andrewla wrote: post #60

> The average lightning strike contains about 1 million joules, enough energy to fry the founding father in his boots. “The typical house in the U.S. has 100 amp service or about 28 horsepower,” says Kirtley. Boy do I get frustrated when using compatible units without conversion. The unit that I hate more than any other unit in the universe is the KwH, which is dimensionally equivalent to the Joule, so I don't unders…

> The unit that I hate more than any other unit in the universe is the KwH, which is dimensionally equivalent to the Joule, so I don't understand why we don't just use that instead.

kWh/yr is worse. It's just watts but obfuscated. Gets used for appliances.

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