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Hook
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Sep 10, 2015
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gjt77
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Sep 10, 2015
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HookLooking at the products you linked on Amazon, they claim to be using SunPower monocrystalline silicon solar cells. SunPower does have demonstrated R&D lab efficiencies of 25%, among the best around (they held one of the world records until very recently) -- and they are a US company, for those that care about such things. But those kinds of numbers are rarely seen in actual high-level production. Additionally, looking at the pictures, it doesn't look like they are actually using SunPower's highest-performance cells (difficult to say for sure, though). And when you package the cells behind the protective plastic sleeving, performance is going to drop (i.e. the plastic will reflect and absorb some of the incoming light). Add in other losses due to wiring and all that, and there's no chance you'd ever see 25% efficiency... Even 22% is highly unlikely. If their power ratings are based on these kind of efficiencies, then you'd never actually see them achieved.
I can't tell what kind of cells the SunJack products are using... They don't say anything other than "monocrystalline" (which means Si), no brand, etc. But their claim of 19% is much more realistic. Whether that's 19% bare cells in the lab or 19% in-product, I can't say. If these are the efficiencies used to predict the power output then you'd be more likely to get close (although realistic sunlight conditions are still likely to not match that of the carefully controlled lab testing).
Now, all this said, this isn't an indictment or a recommendation of any particular product. They could all be great (certainly the reviews in both the Amazon and SunJack cases seem to support this), or they could all have problems. But in my experience, when a company is more honest in the claims they make about their product, those products tend to be better quality. I just think it's awesome that products like this exist at all, that they work really well, and at prices that are totally reasonable; this wasn't possible even just a few years ago (what used to be available was low-efficiency junk).
(FYI: I am a solar power researcher/expert, but have no stake in SunPower or any other company.)
I can't tell what kind of cells the SunJack products are using... They don't say anything other than "monocrystalline" (which means Si), no brand, etc. But their claim of 19% is much more realistic. Whether that's 19% bare cells in the lab or 19% in-product, I can't say. If these are the efficiencies used to predict the power output then you'd be more likely to get close (although realistic sunlight conditions are still likely to not match that of the carefully controlled lab testing).
Now, all this said, this isn't an indictment or a recommendation of any particular product. They could all be great (certainly the reviews in both the Amazon and SunJack cases seem to support this), or they could all have problems. But in my experience, when a company is more honest in the claims they make about their product, those products tend to be better quality. I just think it's awesome that products like this exist at all, that they work really well, and at prices that are totally reasonable; this wasn't possible even just a few years ago (what used to be available was low-efficiency junk).
(FYI: I am a solar power researcher/expert, but have no stake in SunPower or any other company.)
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Amazon has a few similar 20 Watt panels for $58 and $56.
Both claim ~22-25% efficiency
http://smile.amazon.com/dp/B00NGKPX4Y http://smile.amazon.com/dp/B00YOCKV40
And with that you can snag a few power packs. 8,000 mAh ones are hard to find, so lets just bump it up to the 10,000 mAh ones. Looks like ~$14 to $20 each for those.
So all told, buying a non-SunJack equivalent to the 20W version of this comes in at 60 + 20 * 2 = $100, which (when considering shipping costs) undercuts even the 14W variation of this drop.
So: what differentiates these SunJack panels and power packs from others on the market? (and why does massdrop's comment renderer relocate all urls to the end?)