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Solar panels + cold = A potential problem

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Re: Solar panels + cold = A potential problem

#181

Post by [deleted] »

Workaccount2 wrote: post #170
beefnugs wrote: post #51

Earlier quoted context omitted.

Actually if "you work with electrical or electronic systems in practice" you get pissed off at everything for how dumb it all is: 12V DC batteries are more like 14 nominal? AC wall plugs dip voltage when printers turn on, random equipment you arent even sure in the building can trigger UPSes based on unknown settings in the device? International standards and communication protocols mean nothing as "a standard" becau…

This is what makes software engineering so seductive, everything works exactly as it was designed to (whether intended or not). Imagine trying to program for computers with memory that drifts values progressively more as it wears down.

[deleted]

Re: Solar panels + cold = A potential problem

#182

Post by ranger_danger »

jama211 wrote: post #165
hyperhello wrote: post #125

Earlier quoted context omitted.

Why does this kind of comment get downvoted that pinpoints the actual motivation? We just pretend that planned obsolescence is history.

Because it’s an extreme claim backed up with no evidence. Hanlon’s razor applies here.

Also see Hitchens' razor and Russel's teapot.

Re: Solar panels + cold = A potential problem

#183

Post by londons_explore »

Solar inverters could be designed smarter.

Today's inverters have a volt limit and an amp limit and you must stay within both.

But physics doesn't require that - you could instead design a solar inverter where you could stay within either!

It would work by detecting when one limit (volts or amps) was about to be exceeded, and pushing the operational point away from there. Remember that for solar there are two zero power - ie safe - points. I=0 is the usual one, but V=0 (ie short circuit) is equally safe for solar panels.

So this hypothetical inverter would operate between one of the safe points and the max power point.

Obviously whilst installing the system and humans unplugging wires, the V=0, huge current safe point is impractical. But that's why you have breakers.

Re: Solar panels + cold = A potential problem

#184

Post by londons_explore »

londons_explore wrote: post #183

Solar inverters could be designed smarter. Today's inverters have a volt limit and an amp limit and you must stay within both. But physics doesn't require that - you could instead design a solar inverter where you could stay within either ! It would work by detecting when one limit (volts or amps) was about to be exceeded, and pushing the operational point away from there. Remember that for solar there are two zero p…

Worth noting that the physics of electricity has an odd symmetry between voltage, power and current which means almost any circuit can be redesigned to effectively switch around all V's and I's and still work.

It is mere convention that we have decided that V should usually be regulated and constant and a property of the supply whilst I is variable and determined by the load.

Re: Solar panels + cold = A potential problem

#185

Post by rcxdude »

lazide wrote: post #119
rcxdude wrote: post #98

Earlier quoted context omitted.

The article presents it oddly, it's not that the converter maximum input gets lower, it's the solar panel output that gets higher from the nominal quoted value (which is not a maximum, and not really intended to be used as such). Derating your converter is equivalent for the purposes of ensuring margins, but it implies the issue is in the wrong place.

The idea of safety margins has died under the more pressing type - profit margins.

While in general most parts will work beyond their ratings to at least some degree, this isn't really a safety margin. A safety margin is known, rated, and validated, and usually a property of a system as opposed to just one part within it.

Re: Solar panels + cold = A potential problem

#186

Post by dotancohen »

jacquesm wrote: post #176
dotancohen wrote: post #175

Earlier quoted context omitted.

I actually meant a small li-ion inside the appliance, to smooth out the load. Do any batteries support 20C or 30C? That seems like enough to smooth such a load.

That's a very complex and potentially dangerous device.

I see, thanks.

Re: Solar panels + cold = A potential problem

#187

Post by jacquesm »

dotancohen wrote: post #186
jacquesm wrote: post #176

Earlier quoted context omitted.

That's a very complex and potentially dangerous device.

I see, thanks.

The problem would not even be making it initially, the problem would be to keep it safe in the long run. I am not a huge fan of all these embedded Lithium-Ion batteries, they're flooding the market (and our homes) and they are disproportionally large factor in house fires.

Re: Solar panels + cold = A potential problem

#188

Post by gsf_emergency_2 »

pfdietz wrote: post #103
gsf_emergency_2 wrote: post #70

To flip this into a potential solution to a wider problem-- global thermal balance-- combine solar panels with radiative cooling. https://www.sciencedirect.com/science/article/pii/S258900422... https://www.pv-magazine.com/2025/01/13/daytime-radiative-coo...

https://web.stanford.edu/group/fan/publication/Li_ACSPhotoni...

Ah yes, a paper from Fan Shanhui's group at Stanford, which kicked off the whole business. Should have linked that instead!

This is 5.7 deg (using metasurfaces to selectively reflect reflect absorb different wavelengths)

compared to a less fancy 4.9 deg from their seminal paper (2014)

https://www.nature.com/articles/nature13883

Maybe comparable cooling can be achieved with even cheaper techniques..?

Re: Solar panels + cold = A potential problem

#189

Post by jacquesm »

huxley wrote: post #177
jacquesm wrote: post #156

Earlier quoted context omitted.

> it just can't break from it In fact, they can.

I think they meant “it just can’t” in the sense of “it shouldn’t under any circumstances”

Even that interpretation would be be wrong because it can and it does and the circumstances are very clearly described. Every inverter worth considering for a home installation has this capability. Only really old ones are not able to disconnect from the HV side when things are about to go pear shaped. If I had an inverter without that capability I'd get rid of it immediately because that's an accident waiting to happen.

Re: Solar panels + cold = A potential problem

#190

Post by Dylan16807 »

rcxdude wrote: post #99
immibis wrote: post #96

Earlier quoted context omitted.

Very true. My computer says 240V on it, so I should only use it up to 192V.

No, you just shouldn't assume that that's the case. In the case of a computer and mains, both of those are nominal voltages and there will be a range of voltages which are expected to function, and if you want to check for sure, you should check those ranges.

The point is, voltages are usually a 1:1 match. That includes when you're working with ranges, you want the supply range to be inside the load range.

And even for amps where you see that 80% rule, that's for keeping the load smaller than the supply. Solar panels aren't a load and don't work that way.

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