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Solar panels + cold = A potential problem

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Re: Solar panels + cold = A potential problem

#91

Post by myself248 »

This 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 (while baking in the sun!) was top-of-mind for every installation. And right along with learning that critical consideration, everyone also learned the caveat that in the bitter cold, that very same phenomenon means they can produce significantly more. Temperature coefficient was simply something "everyone knew".

Now they're so cheap nobody cares. The magazine shut down because "alternative power" and EVs aren't exactly alternative anymore, you can buy one off the dealer's lot, it's nuts. And the panels are crazy cheap now. If you lose 10% because the panels are hot, it's likely cheaper to just buy 10% more panels, than to redesign your support brackets to allow better airflow. But nobody highlights the phenomenon behind the efficiency loss.

"Everybody knew" that the ratings on the panel are at Standard Test Conditions: 25°C and 1000W/m². That's almost never the conditions in the real world, but it establishes a legal baseline whereby panels can be compared apples-to-apples and advertising kept honest (if anyone cared), but deviate from STC and output will go down, or up. Again, ask today's consumer what the ratings on the label mean, and most of 'em have never heard of STC nor could define how the nameplate wattage is just one point on a curve.

Is this the panel manufacturer's fault? They're labeling things precisely the same as they've labeled them for 40-plus years. (Perhaps there's even more data on the panel label now, as Vmp and Imp are typically specified now, and they weren't always universal.)

Edit to add: The label doesn't typically specify the temperature coefficient, but for every panel I've checked, it is in the datasheet. But who reads datasheets?

Is it the inverter manufacturer's fault? They're labeling things precisely the same as they've labeled them for 40-plus years. The input max is a hard limit where the silicon can take no more, and there's a certain amount of headroom required between that and the panels' max, after compensating for temperature coefficient. Of course you calculate your panel voltage for your local conditions before comparing it to the inverter input, duh!

Everyone knows that! Except now they don't.

Re: Solar panels + cold = A potential problem

#92

Post by metalman »

Where to start, eh! So most everything to do with off grid specifications can be listed as "nominal", ish, depending on, etc.Not knowing this means that persistance will provide the circumstance to be educated. There are a number of ways to get things wrong and melt stuff, or get hurt. Batteries should always be treated as unpredictable dangerous beasts, happy as a clam if they are treated just right, but capable of producing trouble and disaster, or just del8vering a viscious bite to the unsuspecting and surviving to do it again. A 48volt (nominal) battery bank will happily turn the required 10mm wrench into single demonstration of a wide range of metelurgical and other phenomina. For fun on a cold morning take the leads from a 3 kw solar array, off, and then strike the wires to produce a realy big fat arc, h3y hey! The simple fact, that I tell enthused,nice, but clearly unprepared people who express interest in "off grid", is that I do it, but it's not for everybody, as there is a significant technical learning curve, plus the required physical skills to mount panels, run wireing, deal with battery banks,set up the systems, and if costs are to be kept to a minimum then source parts from distributors or import directly.

Re: Solar panels + cold = A potential problem

#93

Post by [deleted] »

dotancohen wrote: post #73
bob1029 wrote: post #35

I 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.

[deleted]

Re: Solar panels + cold = A potential problem

#94

Post by cowsandmilk »

teiferer wrote: post #25

Maybe they should just improve their product to make it more resiliant, rather than blaming customers for thinking that 148 V is below 150 V? Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer. And no matter what happens, customer support should help the customer, not blame them.

Considering the electric code has an 80% rule for loads, anyone assuming they can use 100% of what is on a label probably should not be doing electrical work.

Re: Solar panels + cold = A potential problem

#95

Post by rcxdude »

saghm wrote: post #42
syntaxing wrote: post #13

> Plugging in four 400w solar panels in series is similar to filling your gasoline powered car with diesel and wondering why the car manufacturer isn't replacing your new car. I don’t think this analogy works. The solar input works like Diesel or Gasoline in different temperature. It’s pretty unreasonable to assume the consumer knows when depending on temperature unless the explicitly state in the manual (I’m willing…

Agreed. No one needs to change which type of gas they use because it happens to be a warm sunny day.

Because they run their engines well within the margins of their design. If you were running at the edge of the envelope you would find that the temperature does matter.

Re: Solar panels + cold = A potential problem

#96

Post by immibis »

cowsandmilk wrote: post #94
teiferer wrote: post #25

Maybe they should just improve their product to make it more resiliant, rather than blaming customers for thinking that 148 V is below 150 V? Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer. And no matter what happens, customer support should help the customer, not blame them.

Considering the electric code has an 80% rule for loads, anyone assuming they can use 100% of what is on a label probably should not be doing electrical work.

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

Re: Solar panels + cold = A potential problem

#97

Post by immibis »

cornholio wrote: post #36
geocar wrote: post #29

Earlier quoted context omitted.

> Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer. Idk. I don't have a PHD, but 220V sounds like 240V to me. I wouldn't do this. I feel like getting advice about how to wire up electronics should not be so hard. > Maybe they should just improve their product to make it more resiliant Adding "re…

> Adding "resilience" usually adds to the per-unit cost. In this case, the cost is much less than a dollar (say, a varistor that blows the existing fuse) and it prevents a catastrophic failure.

But they want you to have to buy another one.

Re: Solar panels + cold = A potential problem

#98

Post by rcxdude »

Zanfa wrote: post #34
teiferer wrote: post #25

Maybe they should just improve their product to make it more resiliant, rather than blaming customers for thinking that 148 V is below 150 V? Not everybody buying these has a Ph.D. in physics and if it says 148 V on the label and 150 V on the other label then it's your product that has a problem, not the customer. And no matter what happens, customer support should help the customer, not blame them.

This is 100% on the manufacturer if they intentionally chose to highlight the "best case" 150V, rather than the 120V lower end. Especially without any additional safety mechanisms.

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.

Re: Solar panels + cold = A potential problem

#99

Post by rcxdude »

immibis wrote: post #96
cowsandmilk wrote: post #94

Earlier quoted context omitted.

Considering the electric code has an 80% rule for loads, anyone assuming they can use 100% of what is on a label probably should not be doing electrical work.

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.

Re: Solar panels + cold = A potential problem

#100

Post by happosai »

saghm wrote: post #42
syntaxing wrote: post #13

> Plugging in four 400w solar panels in series is similar to filling your gasoline powered car with diesel and wondering why the car manufacturer isn't replacing your new car. I don’t think this analogy works. The solar input works like Diesel or Gasoline in different temperature. It’s pretty unreasonable to assume the consumer knows when depending on temperature unless the explicitly state in the manual (I’m willing…

Agreed. No one needs to change which type of gas they use because it happens to be a warm sunny day.

True for gas not for diesel. You have to switch to winter- or arctic diesel if the temperature goes below -20c.
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