SomeoneSomewhere

joined 1 year ago
[–] [email protected] 2 points 3 days ago

Even 95% is on the low side. Most residential-grade PV grid-tie inverters are listed as something like 97.5%. Higher voltage versions tend to do better.

Yeah, filters essentially store power during one part of the cycle and release it during another. Net power lost is fairly minimal, though not zero. DC needs filtering too: all those switchmode power supplies are very choppy.

[–] [email protected] 31 points 2 weeks ago

B key vs M key. Laptop likely needs a SATA M.2 using B or B+M keying, you have a PCIe x4 drive with M keying.

[–] [email protected] 2 points 3 weeks ago* (last edited 3 weeks ago)

I'm not sure there are any power grids past the tens-of-megawatt range that aren't just a 2/3/4 terminal HVDC link.

Railway DC supplies usually just have fat rectifiers and transformers from the AC mains to supply fault current/clearing and stability.

Ships are where I would expect to start seeing them arrive, or aircraft.

Almost all land-based standalone DC networks (again, not few-terminal HVDC links) are heavily battery backed and run at battery voltage - that's not practical once you leave one property.

I'm sure there are some pretty detailed reports and simulations, though. A reduction in cost of multi-kV converters and DC circuit breakers is essential.

[–] [email protected] 23 points 3 weeks ago (5 children)

PV inverters often have around 1-2% losses. This is not very significant. You also need to convert the voltage anyway because PV output voltage varies with light level.

Buck/boost converters work by converting the DC current to (messy) AC, then back to DC. If you want an isolating converter (necessary for most applications for safety reasons) that converter needs to handle the full power. If it's non isolating, then it's proportional to the voltage step.

Frequency provides a somewhat convenient method for all parties to know whether the grid is over- or under- supplied on a sub-second basis. Operating solely on voltage is more prone to oscillation and requires compensation for voltage drop, plus the information is typically lost at buck/boost sites. A DC grid would likely require much more robust and faster real-time comms.

The AC grid relies on significant (>10x overcurrent) short-term (<5s) overload capability. Inrush and motor starting requires small/short overloads (though still significant). Faults are detected and cleared primarily through the excess current drawn. Fuses/breakers in series will all see the same current from the same fault, but we want only the device closest to the fault to operate to minimise disruption. That's achieved (called discrimination, coordination, or selectivity) by having each device take progressively more time to trip on a fault of a given size, and progressively higher fault current so that the devices upstream still rapidly detect a fault.

RCDs/GFCIs don't coordinate well because there isn't enough room between the smallest fault required to be detected and the maximum disconnection time to fit increasingly less sensitive devices.

Generators are perfectly able to provide this extra fault current through short term temperature rise and inertia. Inverters cannot provide 5-fold overcurrent without being significantly oversized. We even install synchronous condensers (a generator without any actual energy source) in areas far from actual generators to provide local inertia.

AC arcs inherently self-extinguish in most cases. DC arcs do not.

This means that breakers and expulsion type fuses have to be significantly, significantly larger and more expensive. It also means more protection is needed against arcs caused by poor connection, cable clashes, and insulation damage.

Solid state breakers alleviate this somewhat, but it's going to take 20+ years to improve cost, size, and power loss to acceptable levels.

I expect that any 'next generation' system is likely to demand a step increase in safety, not merely matching the existing performance. I suspect that's going to require a 100% coverage fibre comms network parallel to the power conductors, and in accessible areas possibly fully screened cable and isolated supply.

EVs and PV arrays get away with DC networks because they're willing to shut down the whole system in the event of a fault. You don't want a whole neighborhood to go dark because your neighbour's cat gnawed on a laptop charger.

[–] [email protected] 13 points 1 month ago

There should be no need for tuning, tweaking, or optimizing on functionality this basic.

If you ask the processor, it will spit out a graph like this telling you what threads/cores share resources, all the way up to (on large or server platforms) some RAM or PCIe slots being closer to certain groups of cores.

[–] [email protected] 14 points 3 months ago

Essentially no processors follow a standard. There are some that have become a de facto standard and had both backwards compatibility and clones produced like x86. But it is certainly not an open standard, and many lawsuits have been filed to limit the ability of other companies to produce compatible replacement chips.

RISC-V is an attempt to make an open instruction set that any manufacturer can make a compatible chip for, and any software developer can code for.

[–] [email protected] 15 points 4 months ago (2 children)

It's pretty common to own a domain but not actually host the email server; doing on-premises email is a security PITA and most providers simply blacklist large swathes of residential and leasable (e.g. VPS) IPs.

Unfortunately, if you get someone else to host your email, they often charge by the account, not by the domain. Setting up a new mailbox is therefore irritatingly expensive.

A catch-all email works well, though, and is free from most of the hosting providers. Downside is you get spam...

Jane@JaneDoe certainly seems more common than mail@JaneDoe.

[–] [email protected] 11 points 4 months ago (1 children)

I've certainly never heard of a chicken ranch, but plenty of chicken farms.

[–] [email protected] 3 points 6 months ago

"I thought it would be helpful" to the boss being CCed in.

[–] [email protected] 24 points 6 months ago (2 children)

I expect they are talking about the 'irrevocably' part, as one of the core tenets of GDPR is that consent can be withdrawn.

I couldn't say whether or not that applies here.

[–] [email protected] 6 points 6 months ago

Swifts and Mirages can be under 900kg.

[–] [email protected] 16 points 7 months ago (7 children)

Secondhand stuff can be really cheap if you know where to look, but the drawbacks are usually power and noise.

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