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Slow Electricity: The Return of DC Power? (2016)

lowtechmagazine.com

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Re: Slow Electricity: The Return of DC Power? (2016)

#51

Post by dreamcompiler »

dheera wrote: post #36
musingsole wrote: post #33

Earlier quoted context omitted.

USB-C?

USB-C sucks, I break a USB-C cable a week. They're physically too weak. I've very rarely broken 120VAC plugs or cables. Also you can't exactly have a USB-C PD power strip of 10+ plugs without it costing a fortune because of all the negotiation needed per-port. Now they're onto some GaN bullshit just to make the PD adapters smaller. The standards are a shitshow, there are incredible number of non-compliant USB-C cable…

I have a bunch of USB-C PD boards. Each one is about 1x2 cm and costs around $1. That's small enough. And good cables exist.

Re: Slow Electricity: The Return of DC Power? (2016)

#52

Post by nick__m »

mdorazio wrote: post #15
monitron wrote: post #3

We're currently in the process of designing a house that we hope to build early next year. One thing that I dream of doing is lighting the entire house with LEDs wired in a low voltage DC "network." Even better if they're addressable, dimmable, even RGB recolorable. Power over Ethernet would be a pretty cool way of doing it if it was practical...that way you get the data to control the lights as well as the power to…

Other commenters here haven't really provided any good data to show the issue. If you want to run, say, 10A at 24V through DC wire on a circuit you end up needing stupidly thick wire (~6AWG) to avoid voltage drops over just 100ft. There are charts available to show you, for example [1]. If you're thinking of running normal hobby wire for 12V circuits around a house, the resistance losses are going to be huge. [1] htt…

many post like your's turn around those formulas

  V=RI and W=VI
combined to give

  WireLossInWatt = RI²
assume a 120W bulb and a 2.5mm diameter 1km long copper conductor (around 7ohm).

  at 120V you need 1A so you lose 1²A² × 7ohms = 7W

  at 12V you need 10A so you lose 10²A² × 7ohms = 700W
That example with a small diameter long cable is a bit extreme but I hope it's illustrative

Re: Slow Electricity: The Return of DC Power? (2016)

#53

Post by antisthenes »

malchow wrote: post #18

Solar energy is cheap, as in $0.03/kWhr. (PG&E charges you $0.30/kHWhr.) The best inverters convert solar DC to household AC at 97.6 % efficiency. [1] Adding more solar is a question of adding another panel. The inversion loss is a small price to pay for safe power. [2] DC is probably not coming back as a way to wire houses and buildings. [1] https://www4.enphase.com/sites/default/files/downloads/suppo... [2] https:/…

DC might come back as a separate in-tandem network specifically for ceiling LED lighting.

It's more convenient to simply plug into a low voltage DC current wiring with a LED fixture than to install a AC-DC converter.

It's certainly something I've entertained doing for my own place.

Re: Slow Electricity: The Return of DC Power? (2016)

#54

Post by dheera »

dreamcompiler wrote: post #51
dheera wrote: post #36

Earlier quoted context omitted.

USB-C sucks, I break a USB-C cable a week. They're physically too weak. I've very rarely broken 120VAC plugs or cables. Also you can't exactly have a USB-C PD power strip of 10+ plugs without it costing a fortune because of all the negotiation needed per-port. Now they're onto some GaN bullshit just to make the PD adapters smaller. The standards are a shitshow, there are incredible number of non-compliant USB-C cable…

I have a bunch of USB-C PD boards. Each one is about 1x2 cm and costs around $1. That's small enough. And good cables exist.

> Each one is about 1x2 cm and costs around $1.

Well, I don't. The 100W PD plugs I own cost typically $60 or more. Put yours on Amazon if they can do 100W and I'll happily buy them.

And if it doesn't support full 100W it's a PITA because that's more thing the user has to think about.

Re: Slow Electricity: The Return of DC Power? (2016)

#55

Post by ashtonkem »

IlliOnato wrote: post #37

I read the whole article with sympathetic interest, until the conclusion: > One way to solve the problem of high power devices is simply not to use them -- this is the approach that's followed in sailboats, motorhomes and caravans > Obviously, this strategy implies a change in our way of life. It would mean that electricity is used only for lighting, electronics and refrigeration, while non-electric alternatives are…

You do have to wonder if they’re confused on why this isn’t persuasive to normal people. Go cook outside on a rocket stove[0] and washing clothes by hand every day? Come on.

Meanwhile the thing that has actually gotten people out of their cars is the ebike. It turns out it’s much more effective to produce a more convenient and comfortable solution for people rather than just demand that they go back a century or two just because.

0 - It’s also telling that such advocates never seem to actually say who should be stuck doing all the labor that machines like washing machines now do for us. Washing clothes and dishes by hand is hard labor, and someone is going to have to give up their career or free time to do it if we’re going to ban these machines. No extra credit if you figure out who will get stuck with the task…

Re: Slow Electricity: The Return of DC Power? (2016)

#56

Post by pl-94 »

IlliOnato wrote: post #37

I read the whole article with sympathetic interest, until the conclusion: > One way to solve the problem of high power devices is simply not to use them -- this is the approach that's followed in sailboats, motorhomes and caravans > Obviously, this strategy implies a change in our way of life. It would mean that electricity is used only for lighting, electronics and refrigeration, while non-electric alternatives are…

This is a low tech blog. It is difficult to reduce your carbon footprint while experiencing an exponential urge to consume new tech.

Tech products footprint is either during consumption (most of the devices requiring heat or cold) or during production (the other devices like smartphones).

Obviously this rule is a trend and countries with low carbon electricity are exceptions.

While most people are OK for lasting a smartphone a bit longer, the same logic would imply to reduce the heat/cold consumption.

So yeah in this sense, a freezer is a luxe we can't afford.

Re: Slow Electricity: The Return of DC Power? (2016)

#57

Post by dreamcompiler »

mdorazio wrote: post #15
monitron wrote: post #3

We're currently in the process of designing a house that we hope to build early next year. One thing that I dream of doing is lighting the entire house with LEDs wired in a low voltage DC "network." Even better if they're addressable, dimmable, even RGB recolorable. Power over Ethernet would be a pretty cool way of doing it if it was practical...that way you get the data to control the lights as well as the power to…

Other commenters here haven't really provided any good data to show the issue. If you want to run, say, 10A at 24V through DC wire on a circuit you end up needing stupidly thick wire (~6AWG) to avoid voltage drops over just 100ft. There are charts available to show you, for example [1]. If you're thinking of running normal hobby wire for 12V circuits around a house, the resistance losses are going to be huge. [1] htt…

What? 12AWG Romex is rated for 20A in normal residences in the US and it's already in a lot of homes, so the retrofit would be easy. And for LED lighting you wouldn't need nearly that much current at 24V, so voltage losses would be negligible.

Re: Slow Electricity: The Return of DC Power? (2016)

#58

Post by stephen_g »

da_big_ghey wrote: post #7
prawn wrote: post #2

What might realistically happen for this to be achievable in an existing or new home? Or as a default for new homes? I camp a bit and spend more than enough time dealing with 12V lighting, recharging drone batteries from car/aux batteries, etc. Always end up wondering how much of my house actually needs AC, where in the house that occurs (fridge, ducted heating/cooling unit?) and what could get by without it. More an…

Motors, compressors still are more efficient on AC, for place like American South where air conditioning represent largest segment from electricity expense AC grid remains making sense.

Yes, but the very most efficient AC motors and compressors motors use variable frequency drives, and you can design a VFD powered by either AC or DC.

I still do think AC is still advantageous in a lot of ways for power grids though, just not on that particular point.

Re: Slow Electricity: The Return of DC Power? (2016)

#59

Post by spockz »

dheera wrote: post #36
musingsole wrote: post #33

Earlier quoted context omitted.

USB-C?

USB-C sucks, I break a USB-C cable a week. They're physically too weak. I've very rarely broken 120VAC plugs or cables. Also you can't exactly have a USB-C PD power strip of 10+ plugs without it costing a fortune because of all the negotiation needed per-port. Now they're onto some GaN bullshit just to make the PD adapters smaller. The standards are a shitshow, there are incredible number of non-compliant USB-C cable…

> But really the best would be straight up 48V on 2 rails and a bunch of plugs.

Isn’t that what the “old” PoE was before 802.3at/f? Just plain non negotiated 48V over a cable with RJ45 plugs?

Re: Slow Electricity: The Return of DC Power? (2016)

#60

Post by dreamcompiler »

monitron wrote: post #3

We're currently in the process of designing a house that we hope to build early next year. One thing that I dream of doing is lighting the entire house with LEDs wired in a low voltage DC "network." Even better if they're addressable, dimmable, even RGB recolorable. Power over Ethernet would be a pretty cool way of doing it if it was practical...that way you get the data to control the lights as well as the power to…

Ignore the naysayers herein. Your power requirements are low enough that 12AWG wire will work fine. Wire your lighting circuits with standard 12-2 Romex, power it with 24VDC, and use LEDs. The only hard part is finding the proper constant-current drivers for your fixtures, but they should be available.
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