Slow Electricity: The Return of DC Power? (2016) • Hacker News Board

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

#61

Post by dreamcompiler » Wed, Aug 18, 2021, 4:57 AM UTC

wyager wrote: post #6

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…

Low voltage residential wiring is not very efficient for most applications because the conductors have to be so much larger.

That's true for incandescent lights. It's not true for LEDs because they need ~10x less power.

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

#62

Post by skybrian » Wed, Aug 18, 2021, 4:58 AM UTC

I'm not sure I care whether it's AC or DC, but it might be nice to have some parallel off-the-grid wiring that comes from a solar-charged battery and will run during a power outage.

What would work best for this?

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

#63

Post by dreamcompiler » Wed, Aug 18, 2021, 5:01 AM UTC

Johnny555 wrote: post #16

An LED doesn't run on 24V DC, what's the difference in efficiency between an LED lamp that runs off 120V AC and one that runs off 24V DC?

The power supply. An AC-to-DC converter is bigger, hotter, and more prone to failure than a much simpler 24VDC buck.

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

#64

Post by ip26 » Wed, Aug 18, 2021, 5:02 AM UTC

ashtonkem wrote: post #55

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…

never seem to actually say who should be stuck doing all the labor

They are probably not actually closet misogynists or anything like that, they probably just haven’t thought that far ahead.

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

#65

Post by dreamcompiler » Wed, Aug 18, 2021, 5:09 AM UTC

baybal2 wrote: post #9

Almost every type of DC-DC conversion requires some intermediate AC conversion anyway. And surprise, a lot of DC-DC topologies require a transformer too. Transformers still soundly beat solid state conversion on cost, and efficiency at above the wall outlet voltages. You can't run away from that entirely. If you were to give a free hand to a good EE to redesign the electric grid from scratch, I doubt the result will…

But that intermediate AC is square (not sinusoidal) which means the transistors spend almost no time in the linear range, which means they generate very little heat. And the frequency is much higher than 60Hz too. It's a very different kind of AC, with much more controllable and more efficient electronics.

Transformers still have their place but they're still basically big dumb (uncontrollable) chunks of copper and iron.

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

#66

Post by tootie » Wed, Aug 18, 2021, 5:11 AM UTC

function_seven wrote: post #44

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…

I get unreasonably angry when Victorian cosplayers think they've found the solution to our wasteful modern life. Simply eschew modern conveniences and spend hours each week beating your clothes against a rock! Simple , instead of grocery shopping twice a month, ditch that wasteful freezer and walk to the farmers' market down the block before dinner each night. Was it cloudy yesterday? Simple! , take a whore-bath¹ at…

It's frequently much more energy intensive too. Cars are a lot more efficient than horses and dishwashers are more efficient than hand washing.

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

#67

Post by [deleted] » Wed, Aug 18, 2021, 5:26 AM UTC

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:/…

[deleted]

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

#68

Post by zurn » Wed, Aug 18, 2021, 5:26 AM UTC

Many of the loads discussed, eg washing machines, are also reasonable matches a local solar power source, as it's much cheaper to buffer hot water than have large batteries.

(Water heating dominates the energy used in those, the mechanical sloshing around takes trivial power compared to it).

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

#69

Post by Johnny555 » Wed, Aug 18, 2021, 5:28 AM UTC

dreamcompiler wrote: post #63

Johnny555 wrote: post #16

An LED doesn't run on 24V DC, what's the difference in efficiency between an LED lamp that runs off 120V AC and one that runs off 24V DC?

The power supply. An AC-to-DC converter is bigger, hotter, and more prone to failure than a much simpler 24VDC buck.

Aren't efficient DC-DC converters just switching power supplies? Are they inherently more efficient or long lived than a 120VAC-DC switching power supply?

I'm using my ipad while plugged into a 120V USB charger, and the charger isn't even warm.

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

#70

Post by pkulak » Wed, Aug 18, 2021, 5:32 AM UTC

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…

Exactly. The problem here is that everyone will just switch to gas for everything. Dryer, stove, water heater, car, etc. That’s terrible!

The 380-volt DC sounded nice, so long as DC to DC is more efficient than AC to DC, but I have no idea if that’s true.