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Solar panels + cold = A potential problem
151–160 of 228 posts
Re: Solar panels + cold = A potential problem
#152This is not a problem in a properly dimensioned system at all.
It is still well within the 'engineering reserve'. Solar panels produce the most power in mid March, when they are cooled very well by the ambient air but the sun is already lining up nicely with the panels at mid-day. But those conditions are pretty rare, and most inverters will handle this gracefully by simply dumping some of the excess power as heat - or in the better ones, by simply chopping the input voltage at a high frequency. This allows for very fine control over the average power and will help to keep the voltage under the isolation break down voltage (which usually is a very large factor over the voltages that you see in practice).
My own system is 50 panels, 1000V maximum on panels that nominally produce up to 100V, so I never have more than 8 of them in series. That leaves 200V to play with and I've never seen it get close to that 1000V. The inverters are easily capable of dealing with this and if the strings were to ever exceed 1000V then the inverters would simply disconnect those strings with their internal disconnect relays.
So, in closing: don't run your system 'on the limit' or rare conditions will push it over the limit. But even if you do: inverters are fairly bullet proof nowadays and if you over-volt the input the vast majority of the ones that you can normally buy are going to just switch off and move to an error state that will require you to power them down before they will be usable again.
Re: Solar panels + cold = A potential problem
#153I never tried the solar charging on my ecoflow so this fragility surprises me a bit. I've been able to run laundry in a machine with a 1/2hp motor using the inverter side on multiple occasions. No smoke or funny smells. My 2200w generator would trip out the instant the spin cycle tried to start.
Slightly OT, but how big of a capacitor would be needed to smooth out those current spikes? Solar-friendly could be a selling point for some appliances. I wonder if such a capacitor could even be retrofitted.
A capacitor wouldn't help in this case. They're most useful when you need to overcome transient situations like a locked rotor, not when you have a heavy drum that needs to be spun up from zero. During this phase the machine can consume well over 2kW of power for a few seconds. The circuit is rated for continuous 15A, but it has no problem supplying 20 or 25 for a brief period of time.
Re: Solar panels + cold = A potential problem
#154Earlier quoted context omitted.
Really? I have all sorts of electronics that say everything from 208V - 240V that all go in the wall, so I think all those numbers are probably close to each other in whatever a volt is. I think if I'm worried about a limit of some kind, being within 5% of that limit seems like I might as well be over-limit if the commonly seen distribution I see in my house is greater than 15%
I have a lot of electronics that accept 100-240v doesn’t mean I think they’re close together, just that they have compensating mechanisms to handle such voltages. The margins are generally lower for higher power devices because the electronics are more expensive. Thankfully these electronics in general are becoming cheaper which is one reason why they’re ending up in the hands of people inexperienced with them. Also…
> I have a lot of electronics that accept 100-240v doesn’t mean I think they’re close together, just that they have compensating mechanisms to handle such voltages.
I bet you also have a lot of electronics that don't though, and those that do probably say so.
My kitchen mixers, dishwasher, washing machine, driers, rice cooker, refrigerators, sauna, and pool pump aren't that tolerant by a long shot. I've got a few computers with a switch on the back to choose between 220v and 110v.
Plugging something that takes 110v into my house breaks the thing, so I've learned to check.
But I don't have anything that's 208v that can't go into the house. So I think whatever the situation is with volts, within 15% is "basically the same", so coming within 15% of the rated limit, is probably just like exceeding the limit by 15%.
And so this is why I would not expect something at 146V to be under the safety limit of 150V.
> Also try to tell someone they need an extra 30% in margin and often they'll think they’re being upsold.
Where do you get 30%?
Re: Solar panels + cold = A potential problem
#155Earlier quoted context omitted.
So on the one hand we have a product which isn't even remotely designed for the use case (hamsters), and during normal use shows obvious behaviour (cooking) that should imply risk to said hamsters. On the other side, we have a product designed to be installed in an electrical system, and shows no signs during normal use that it's installed unsafely, and where the advertised specs are not actually safe for normal usag…
Microwaves were originally specifically invented to microwave frozen hamsters: https://interestingengineering.com/videos/1950s-reanimating-...
As Doc Brown would say, "Great Scott!"
Re: Solar panels + cold = A potential problem
#156Earlier 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.
Your converter doesn't need to like the voltage, it just can't break from it. In fact, if it's the type that shorts the panels for curtailing, it should be happy to just run them at the highest voltage it's comfortable with, loosing a few percent generation during exceptionally cold days.
> it just can't break from it
In fact, they can.
Re: Solar panels + cold = A potential problem
#157Earlier quoted context omitted.
Why not label the panel with the maximum possible voltage that it can produce? Or even have a little table showing the maximum possible voltage at various ambient temperatures. It's not as if there isn't room on the back of the panel for a big enough label.
The entire industry has standardized in having "typical" and "maximum" values decades ago. That problem there is completely self-imposed.
The flip side of this is also dumb labelling. ‘Product may contain traces of nuts’.
Completely unhelpful to those that need the info.
Re: Solar panels + cold = A potential problem
#158Earlier quoted context omitted.
Slightly OT, but how big of a capacitor would be needed to smooth out those current spikes? Solar-friendly could be a selling point for some appliances. I wonder if such a capacitor could even be retrofitted.
A capacitor wouldn't help in this case. They're most useful when you need to overcome transient situations like a locked rotor, not when you have a heavy drum that needs to be spun up from zero. During this phase the machine can consume well over 2kW of power for a few seconds. The circuit is rated for continuous 15A, but it has no problem supplying 20 or 25 for a brief period of time.
I'm sure that home mains would have no problem, but a solar installation might. Would a small li-ion help smooth over those amperage hills?
Re: Solar panels + cold = A potential problem
#159This is what happens when something goes mainstream. The background knowledge that "everybody knows" when it's niche, because only turbo-nerds are into it, simply isn't common sense for everybody in the wider population. Back when Home Power magazine started up, the panels were super expensive, and squeezing out every watt was important. Since high temperatures decrease voltage and output, keeping the panels cool (wh…
The input max is for most inverters on the market now a setpoint where they will simply disconnect, stop generating power and go into an error state that you need to hard-reset if you want to use the inverter again. It's pretty typical to have a 1000V hard limit on a nominally 800V or 600V system. If you're going to ride close to the limit then on some days you will see overvoltage and disconnects. So it is something you simply should not do. But people think that if the label says 1000V then 990V total nominal panel voltage should be fine, which it obviously is not. Panels are analog devices, they will produce an open circuit voltage much higher than their nominal use voltage and when you're on a switched mode inverter that means that the average voltage may well be 'in spec' but the voltage from one millisecond to another may well be outside of that if the system was built 'on the edge'. And because inverters have to take the grid side into account as well (they are not allowed to exceed certain voltages) there is always the risk of not being able to load the panels sufficiently to get the voltage to drop. So you should side your system so that the open loop voltage of your panels under ideal conditions is still comfortably lower than the max input voltage of the inverter. 800V nominal is pretty close to that limit, 700 is better and 600 is playing it safe.
I think one of the main reasons why installers tend to overprovision voltage wise is that they count on the inverters switching off the whole string every now and then versus being able to make more power without a lot of additional wiring under normal conditions. The net effect of that is positive.
Low quality inverters (the ones without the ability to disconnect the HV side autonomously) should be avoided like the plague anyway, those are simply unsafe and as far as I am concerned should not be allowed for re-sale at all.
My own system can make 17KW on a very good day in March at 1 pm or so, but normally it is closer to 12KW even in the summer. So those peaks are actually substantially over the normal output. Over a given day the average is about 5 KW or so from sunrise to sundown, and those first and last hours hardly contribute.
Re: Solar panels + cold = A potential problem
#160Can anyone comment on the "You can exceed the amperage specs" ? I made myself a little case study using 4x1W panels and using them in series and parallel. I got the distinct impression that running panels in parallel is better in not so bright conditions compared to a single panel. Whereas a serial configuration made it worse. Since the sun doesn't shine here that much. Running in parallel seems to be preferable, but it would slightly exceed the amperage spec of a few converter i sampled.