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Solar panels + cold = A potential problem

linspyre.com

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Re: Solar panels + cold = A potential problem

#141

Post by Pet_Ant »

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.

Your safety margin is my profit margin.

- Mr MBA

Re: Solar panels + cold = A potential problem

#143

Post by namibj »

Faaak wrote: post #85

Last year, I did yet another PV install at a friends house. While plugging the SMA inverter to the solar field (600V), I fucked up and inverted plus & minus. Nothing happened. I read the manual and realised that SMA inverters are protected against reverse polarity. Yeah, a bit more expensive, but well worth it

I'm more surprised you managed to plug them in reversed; did you have good reason to avoid the polarized semi-pwrmanently-latching connects that most panels ship with?

Re: Solar panels + cold = A potential problem

#144

Post by ramses0 »

dgfitz wrote: post #15
therein wrote: post #4

I am sure many are familiar but I found it amusing when someone explained to me why it is called magic smoke. It is because electronics work through magic so when you let the magic smoke out, they stop working.

I’ve never heard it called magic smoke before, but a regular saying at one of my old jobs was “ah yeah we let the smoke out” in relation to 100% electric drive vehicles. Smoked many inverters, shorted 96v bus to a 24v bus, etc. It was almost a rite of passage to “let the smoke out” in that org. That job was actually great because as a software engineer I happily spent a lot of time with a fluke, a wrench, arm buried…

Hackers dictionary: http://www.catb.org/jargon/html/M/magic-smoke.html

Re: Solar panels + cold = A potential problem

#145

Post by nerdralph »

Calculating temperature correction is in both the NEC and CEC. Here's the CEC version:

64-202 Voltage of solar photovoltaic systems (see Appendix B)

1) The maximum photovoltaic source and output circuit voltage shall be the rated open-circuit voltage of the photovoltaic power source multiplied by 125%.

2) Notwithstanding Subrule 1), the maximum photovoltaic source and output circuit voltage shall be permitted to be calculated using a) the rated open-circuit voltage of the photovoltaic power source; b) the difference between 25 °C and the lowest expected daily minimum temperature; and c) the voltage temperature coefficient as specified by the manufacturer.

Re: Solar panels + cold = A potential problem

#146

Post by PaulKeeble »

The cause of this problem is the standards for Solar Panels, that has the outputs measured at 25C so they are comparable with each other. The specification sheets for panels do list their peak voltage in other conditions but all the advertising is based on the standard. Solar installers know about this and size accordingly but your average consumer doesn't and is very quickly going to get into trouble with this.

I think what Delta needs to do here is accept that the standards mean all Solar will be sold this way and appropriately oversize the inverter so that it can cope with -10C sunny days. Yes its annoying for them but the reality is devices sold to people who don't know how all this works need to compensate for lack of expert knowledge in its user base.

Re: Solar panels + cold = A potential problem

#147

Post by dotancohen »

namibj wrote: post #137
dotancohen wrote: post #73

Earlier 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.

Don't bother; at that point just plug them into 200~300 V DC right to the battery (with just fuse and meter between, no need for any conversion, the washer motor controller that'd be needed to utilize a capacitor for smoothing these spikes would do just fine on a reasonable battery charge/discharge voltage spread.

Do any home battery systems, or home appliances, actually support this?

Re: Solar panels + cold = A potential problem

#148

Post by cameronh90 »

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.

I don’t know about the components they’re selling, but with electronic components, it’s on the buyer to properly read the data sheet and understand what the quoted nominal specs mean.

Unless it’s safety critical, you usually don’t want a system with a bunch of active electronics to prevent someone wiring it up wrong, because those components will interfere with whatever you’re hooking it up to, such as the MPPT, the battery, or whatever else.

This is like how AA batteries have a nominal voltage of 1.5V but the actual open circuit voltage is 0.9V~1.65V depending on charge level, temperature, etc. If you connect an AA to something that’ll explode at a voltage of 1.55V, that’s on you.

Similarly if you buy a 470 ohm resistor, you will find in on the data sheet that’s usually at 20°C. To know what it’ll be at any other temperature, you’ll need to use the temperature coefficient to calculate it.

Re: Solar panels + cold = A potential problem

#149

Post by stockresearcher »

1970-01-01 wrote: post #138

>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. Ok, that is a very bad answer. Diesel fuel contains more amounts of energy per drop as gasoline, but that doesn't mean engine damage will result. Diesel fuel will not damage an engine if you were stupid enough to get it wrong at the pump. It wil…

Maybe it’s different in the rest of the world (I doubt it), but the fuel nozzles for gasoline and diesel are different. You can’t put a diesel nozzle into the opening on a gasoline car, so it’s rather difficult to fill a gasoline car with diesel fuel.

The other way around is possible. You can fill a diesel tank with gasoline. Whether it destroys the engine or not depends on how much gasoline you put in. A gallon or two that is then diluted by filling the rest of the tank with diesel is not likely to cause any lasting damage. If you fill a tank 3/4 of the way with gasoline and try running it in a diesel you are probably going to need a new engine.

So yeah, the analogy is not good. Slightly exceeding the rated voltage and breaking the whole thing is usually not the same as putting a little gasoline in your diesel tank.

Re: Solar panels + cold = A potential problem

#150

Post by syntaxing »

namibj wrote: post #134
syntaxing wrote: post #82

Earlier quoted context omitted.

Another post commented but that’s exactly the point of the MPPT. Not only is it temperature dependent but solar incidence angle matters too (how the sun angle is relative to the surface). MPPT works by changing the internal impedance to match the ideal charging voltage. But there’s a limit to how much it can regulate but I think it’s very fair that a consumer would expect nominal voltage times panels in series is les…

There's a reason people don't install electric equipment without training. This is just like not upsizing wire gauge if you have a bunch that are loaded simultaneously buried together in a somewhat insulating wall. Without the burying under plaster, everything would be fine. But combine that with simultaneous loading during summer, and you fry/roast the PVC insulation.

> There's a reason people don't install electric equipment without training.

I’m not sure if I follow that logic and if your analogy follows. I would argue this is closer plugging in an appliance rather than running wires. If I run a 15A appliance on a 10A breaker, a normal person without training would expect the breaker to trip. This is like running a 10A appliance and the 15A breaker trips because the appliance is sometimes 16A when it works in the cold.

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