So, I used to be "team DC" as well, but after learning up a bit, I realized there are still a lot of advantages to AC in the 21st Century.<p>One reason DC power is more viable nowadays is (as others here have mentioned) the use of DC-DC converters. They internally actually use AC to do the conversion (usually at much higher frequency to save weight and cost on inductive elements). But they're not super cheap (not cheaper than transformers) and they can also be inefficient.<p>But part of my problem with this article is it kind of sandbags the efficiency. We can get pretty high efficiency inverters and rectifiers. >90% is common and 95-98% is feasible (and not uncommon). Low voltage DC (like 12V) requires MUCH thicker cables for the same power, which means a lot more copper (and copper mining). Typical line voltage can be very lightweight.<p>With DC, nothing is really at the same voltage, so you need DC-DC converters all over anyway, so you're not saving anything (although not losing much, either!).<p>Another important thing that really drives some of the advantages is: breakers, relays, and (much less important) current measurements of existing cables. All these are feasible for both DC and AC, but cheaper and easier with AC. AC is self-extinguishing as it crosses zero 120 times a second. That means you can switch a circuit on or off when the applied voltage is very low, meaning you can use cheaper and lighter power electronics. Plus, at a given voltage, there's a safety advantage as arcs will more easily stop with AC.<p>I actually think it's funny to see this in a "low tech" blog. DC ubiquity is something really only practical for significant use (i.e. beyond automotive or RV) with modern 21st century power electronics.
I read the whole article with sympathetic interest, until the conclusion:<p>> 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<p>> 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 chosen for all other appliances. Not coincidentally, this is quite similar to how DC grids were operated in the late nineteenth century, when the only electric load was for lighting -- first arc lamps and later incandescent bulbs.<p>> Thus, no dishwasher, but doing the dishes by hand. No washing machine, but doing the laundry in a laundromat or with a manually operated machine. No tumble dryer, but a clothes line. No convenient and time-saving kitchen appliances like electric kettles, microwaves and coffee machines, but a traditional cooking stove operated by (bio)gas, a solar cooker, or a rocket stove. No vacuum cleaner, but a broom and a carpet-beater. No freezer, but fresh ingredients. No electric warm water boiler, but a solar boiler and a small wash at the sink if the sun doesn't shine. No electric car, but a bicycle.
"Early DC power stations had a dynamo for every light bulb. Source unknown."<p>I have no idea where they got that picture either. Edison's Pearl St. station did not work that way, and that was the first power station. The generator shown is Edison's famous "long-waisted Mary Ann". But Edison never built a one generator per bulb power station. He was able to calculate ROI [1]. This is probably some conceptual drawing of what would have been necessary had the "subdivision of the electric light" (a hot issue around 1889)[2] had not been accomplished.<p>"In other words, a DC electrical system could make a solar PV system more energy efficient." Not clear that it matters much in terms of raw conversion efficiency. Solar inverters are now up around 96-98% efficiency. If you're going to have batteries, you need something that handles battery charging, discharging, and some constant output, and while you can get all that stuff for 12VDC or 24VDC, it's not any more efficient than outputting 120VAC.<p>The real argument they're making is to save power by using small boat or RV sized appliances. They're available, efficient, undersized, and about 3x as expensive as line-powered units.[3]<p>[1] <a href="https://www.hup.harvard.edu/catalog.php?isbn=9780674423640" rel="nofollow">https://www.hup.harvard.edu/catalog.php?isbn=9780674423640</a><p>[2] <a href="https://www.nature.com/articles/040152a0.pdf" rel="nofollow">https://www.nature.com/articles/040152a0.pdf</a><p>[3] <a href="https://www.thecabindepot.com/collections/appliances" rel="nofollow">https://www.thecabindepot.com/collections/appliances</a>
Solar energy is cheap, as in $0.03/kWhr. (PG&E charges you $0.30/kHWhr.)<p>The best inverters convert solar DC to household AC at 97.6 % efficiency. [1]<p>Adding more solar is a question of adding another panel.<p>The inversion loss is a small price to pay for safe power. [2]<p>DC is probably not coming back as a way to wire houses and buildings.<p>[1] <a href="https://www4.enphase.com/sites/default/files/downloads/support/IQ7-IQ7plus-DS-EN-US.pdf" rel="nofollow">https://www4.enphase.com/sites/default/files/downloads/suppo...</a><p>[2] <a href="https://www.businessinsider.com/tesla-solar-panel-fires-become-nightmare-some-homeowners-2019-10" rel="nofollow">https://www.businessinsider.com/tesla-solar-panel-fires-beco...</a>
DC wiring is already standard in many office buildings in the form of power over Ethernet (PoE). It powers access points, lighting, and infrastructure, and high power variants can do 100W+. Since it's under 50V, the IT guy can install it without a qualified electrician.
High power loads like motors and heaters will continue to require AC but I see no reason why small loads can't use PoE. I would love to see it take off for residential use, especially for IoT stuff.
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.<p>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 run them.<p>Does anything like this exist in a way that won't get me fired by the builder for even mentioning it?
There is a line that’s incorrect in the article:<p>> AC won, mainly because of its higher efficiency when transported over long distances.<p>AC is not actually more efficient at long distance transmission, it’s <i>less</i> efficient due to the skin effect. AC is just easier to convert.
Almost every type of DC-DC conversion requires some intermediate AC conversion anyway.<p>And surprise, a lot of DC-DC topologies require a transformer too.<p>Transformers still soundly beat solid state conversion on cost, and efficiency at above the wall outlet voltages.<p>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 differ much from what the world has already.
To all the detractors here. I lived on a boat for many years which was 12v only and didn't have the mod cons. You adapt pretty quick then hardly think about it.<p>So everyone saying how it's fantasy to expect peoples behaviour to change, just remember if you haven't tried it you are likely highly over estimating how much effort it is, and not aware of many of the unexpected advantages.
Well yes, but frankly given the small losses due to modern conversion systems being so efficient I think we're worrying about catching that last small%age if energy losses.<p>As much as I personally hate them, would it not be better to install 120% of solar cells required to match the load upfront. Given the energy is free at generation write off this small inefficiency as being built into the system. It's not like the sun will come after you for capturing more than your fair share.<p>This feels like a problem for 2100 imo once we've moved to much lower carbon supplies.
This doesn’t make any sense. Power transmission with DC still requires high voltage for any reasonable efficiency. Then you have to convert it back down to a residential voltage (still probably >100V for conductor material efficiency) and then devices have to convert that down to low voltage. So you’re not actually saving any conversion steps. On top of that, you have to use DC-DC power electronics, which are much more expensive than transformers etc. at high power levels.<p>There is an argument for using DC over AC but avoiding conversion losses is not a compelling part of it.
> Last but not least, low-voltage DC grids (up to 24V) are considered safe from shock or fire hazard<p>This is absolutely untrue. You may be safer from shocks, but it's a much _worse_ fire hazard. The currents need to be higher at lower voltages. Higher voltages need less current for the same power, decreasing the fire risk.
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.<p>(Water heating dominates the energy used in those, the mechanical sloshing around takes trivial power compared to it).
Seems like distributing power at low voltages, whether DC or AC will result in lower efficiency so it seems like using low voltage DC for higher efficiency distribution is a bit of a wash. It’s likely AC conversion efficiency will increase over time anyway.
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.<p>What would work best for this?
What might realistically happen for this to be achievable in an existing or new home? Or as a default for new homes?<p>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 and more of my power tools are battery based too. Would AC to the kitchen and garage be enough?
The contrast of articles currently on the HN front page is amusing.<p>We have this article that discusses changing home design in order to limit cabling losses (crazy) and not using "high power" appliances that we associate with modern life... and another article discussing Livermore labs achieving net positive fusion, a milestone that seemingly hints we're on the cusp of a carbon free renaissance of power generation.<p>Schrodinger comes to mind
If you read to the end... This kind of system only makes sense where there aren't major appliances. (Think RVs, off-grid cottages, and developing countries.)<p>I wonder what would happen if we redesigned the grid today? Would it be AC or DC? If AC, would it be a higher frequency? (Smaller transformers) Is modern DC-DC voltage conversation easier than AC-DC? What voltages would we use?
I would love 12VDC wired around my house with step down converters for each room. It would allow Our kids to plug in and unplug most of their things themselves (music players, lights, etc).
Meanwhile, we can't even manage to phase out the penny.<p>Sorry to be so pessimistic on my first post, but I don't see this happening for a long, long time.