Lots of people talking about buying solar panels.

[quixoticgeek@social.v.st]

Lots of people talking about buying solar panels. Alas if you look online there's a lot of retailers with all sorts of panels for sale, not all of which are honest. Want an easy way to check if the listed power output is plausible?
Example using a 50w panel listed on Amazon. It's 370x820mm.
Step 1 calculate the area in square meters. (0.37*0.82=0.3034)
Step 2 multiply by 1000w. (0.3034*1000=303.4)
Step 3 assume 20% efficiency and multiply (303.4x0.2=60.68)

60.68>50w. It's Plausible.

#SolarPunk

[boydstephensmithjr@hachyderm.io]

@quixoticgeek So, solar flux at the surface (of Earth) is approximately 1kW/m^2?

[quixoticgeek@social.v.st]

@BoydStephenSmithJr essentially yeah. It varies of course across the planet. But panel rating is based on 1kw/m², and typical efficiency is about 20%.

[disorderlyf@todon.eu]

@quixoticgeek Are you saying solar panel manufacturers are underreporting the max wattage of their panels? Because when I read the first part of this, I assumed you meant the inverse

[quixoticgeek@social.v.st]

@disorderlyf no they under report. The 60 is higher than the 50 rating for the panel, as the panel has a border round it and not 100% of the area is silicon. The 50w panel in the sample has a border of about 20-30mm round the edge that is structural, but not power generating.

But I've also seen panels the same size listed as 100w. And that's clearly not gonna happen.

[oneinterestingfact@mastodon.ie]

@quixoticgeek @BoydStephenSmithJr
And, to return to an earlier theme, slightly more in earth orbit. Going to make cooling those orbiting data centres so much fun.

[quixoticgeek@social.v.st]

@OneInterestingFact @BoydStephenSmithJr exactly. Orbit is a stupid place for a datacentre.

[oneinterestingfact@mastodon.ie]

@quixoticgeek @BoydStephenSmithJr
I suspect Musk knows that. But do the mugs?

[quixoticgeek@social.v.st]

@OneInterestingFact @BoydStephenSmithJr no. It's all greater fool theory.

[oneinterestingfact@mastodon.ie]

@quixoticgeek @BoydStephenSmithJr
so like donnie's golden phone they'll pour money in, Musk will pretend to spend it while using it for whatever nazis spend their money on and they'll see no return whatsoever.

[disorderlyf@todon.eu]

@quixoticgeek Yeah, I'd been waiting for efficiency to get to the point where we actually could get 100w out of a panel that size, but it's looking like I might just want to shell out for a bigger battery and (relative to its capacity) drip feed it solar. I want a panel I could fit inset into a window since I'll likely be living in a rental for at least another year.

[ariaflame@masto.ai]

@BoydStephenSmithJr @quixoticgeek That's the approximate peak illumination at the peak of the day. 9am-3pm have reasonable illumination but most commercial panels have efficiencies in the low 20 percent it's a reasonable way of telling if they're bullshitting. You probably won't get that much because of the effect of heat on efficiency mind you.

[annantidote@chitter.xyz]

@quixoticgeek @disorderlyf ...and probably they are counting on different weathers, latitudes and angles, as in not promising close to the optimum case.

[disorderlyf@todon.eu]

@annantidote @quixoticgeek I'm in BC, so I'm already expecting things to not be optimal, but I also might have a place to put it where it'll get as much sun as it possibly can.

[terrybtwo@ohai.social]

@quixoticgeek The UK has lots of information in data sheets. What there isn’t is anything useful Like how long to repay the cost. Getting a straight answer from installers is tougher than getting a politician to say yes. Getting advice on if they’ll repay the cost within your lifetime is close to impossible. Then there’s the battery.
We got ours from Costco because they were the only ones not trying to sell panels + battery as a package. We got a battery later - I’m not sure it was a good idea.

[quixoticgeek@social.v.st]

@disorderlyf @annantidote note that the angle that gets best yield in summer, Vs best yield in winter is very different. Also where in BC matters a lot.

Btw. Happy to offer advice, and sanity check designs for anyone doing a solar build.

[quixoticgeek@social.v.st]

@disorderlyf if you're putting a panel behind a glass window. Assume about 50% less power from it. I have a 100w panel behind a double glazed window and get about 50w from it peak.

[edavies@functional.cafe]

@annantidote @disorderlyf No, there are standard test conditions for which panels are rated. As @quixoticgeek says it assumes insolation of 1 kW/m², also a specific spectrum of light (corresponding to a panel standing on flat dusty red ground in Texas with the sun at a particular elevation IIRC) and particular temperatures for the ambient air.

But, yes, panels can produce more than the “peak” output quoted. E.g., when a cloud has just blown away so the panel is cooler and therefore operating more efficiently and there's also more sunlight because of the reflections from the cloud just out of the line of sight. So “peak” would be better called ”nominal” output.

[quixoticgeek@social.v.st]

@TerryBTwo it depends a lot on what your usage is like, how big a battery you can afford, do you want to charge an EV? Power a heat pump? Etc... There's a lot of variables. I think with a modern solar install, the average household is likely to pay back a suitable solar install in 3-5 years. But it does depend a lot. Gone are the days where ROI was double digits years.

[vgarzareyna@mstdn.mx]

@quixoticgeek why only 20%?:0