I sympathize! I tried to do something similar once (12V power for exterior lights though) and also was foiled by a piece-of-crap charge controller. Never did get it working properly TBH, though someday I’ll do something with the solar panel. In the end I own my house so I just ended up getting residential solar panels installed on the roof. No regrets.
The first disappointment came when I tried to power the solar panel from the lights in my apartment. That didn’t work whatsoever.
It’s not obvious because of the way our eyes work, but full sunlight is something like 100x brighter than a brightly lit room, and 1000x brighter than a dimly lit room.
…the temperature for the battery is wrong,..
Temperatures reported by batteries themselves are often (but not always) from sensors inside the packaging, so are commonly warmer than you’ll measure from the exterior of the battery. In this case though, that’s a pretty big difference, so you’re probably correct.
Perhaps …the window glass is blocking most of the power of the sun?
Unless they are tinted, shouldn’t be a concern. Window glass does block IR and UV radiation but afaik that’s not a particularly significant difference, maybe like 10% of the total energy. And I don’t think most solar panels can make use of those wavelengths anyway?
If I stay with the solar panel behind glass doors, I get 0.05A (no matter how close I stand behind the glass), if I open the doors and stay directly in the sunlight, I get 0.38A.
…or maybe I’m very wrong?!? Dang. This is weird!
Other random bits and pieces:
An overcast day can easily only produce 1/20th the power of a fully sunny day, so overspeccing the solar panel is a good idea.
Afaik measuring the voltage out of solar panels and lithium batteries is Weird ‘cause they’re nonlinear, how much voltage they produce depends on the load. This mostly measures amperage though, which shooooould be more stable? Not sure.
Some solar panels are built in such a way that if they are partially covered, no cell can produce more energy than the most shadowed cell. Most these days don’t have that problem… I think???
Similar to your earlier point, your eyes aren’t very good at estimating the light attenuation from a window. At least with modern triple-glazed windows, the difference is definitely visible to the naked eye if you partially open the window and look at a surface illuminated side by side directly by the sun and through the glass. I expect such a visible difference translates to 2-digit percentage attenuation. I wonder if the observed measurement can be explained by the combination of that with the cells’ nonlinear behaviour. (especially towards the minimum productive radiation threshold end on the cloudy day)
In the end I own my house so I just ended up getting residential solar panels installed on the roof. No regrets.
The conclusion I’ve reached with regards to domestic-scale energy collection is “go big or go home.” Except in very niche applications, it’s almost certainly not worth the expense and use of materials to bother with anything smaller than the classic 200-400W scale PV panels. Even if you don’t own your home, you can now get balcony-mounted full-size panels, and many European countries allow connecting these to the domestic mains via micro-inverters without explicit permission or certification by a licensed installer. (The limit tends to be around 600-800Wp max-spec backfeed.) This seems to be about the smallest scale that starts making any economic sense, and the tech is mainstream enough that it actually works without hassle.
If the goal is partial autonomy and the ability to power certain devices even through extended blackouts, things rapidly become expensive, but again there are economies of scale. I haven’t researched enough to see if there are robust, inexpensive, off-the-shelf PV-fed inverter-chargers which don’t backfeed more than those 600-800 Watts (or anything at all), but act as UPSes for downstream devices. It certainly seems like that’s a category that should exist. (If PV generation power exceeds maximum allowed backfeed + consumption, you’d need some algorithm for balancing between maximum PV energy and allowing battery discharge during times of no/low generation versus maintaining a minimum blackout bridge time.)
(Disclaimer: we’re running a 2-panel micro PV setup with a inverter, no battery. A pair of 375Wp panels screwed to the south wall of the house, connected to 600Wp inverter. We opted for this for the moment as although we own the house, there are likely upcoming modifications to the roof, so we’d rather get those out of the way before slapping 10kWp of panels on there only to have to move them a year later.)
At least with modern triple-glazed windows, the difference is definitely visible to the naked eye if you partially open the window and look at a surface illuminated side by side directly by the sun and through the glass.
Dang, I guess you’re right. Never really thought of it that way; triple-glazed windows would definitely make a difference.
Except in very niche applications, it’s almost certainly not worth the expense and use of materials to bother with anything smaller than the classic 200-400W scale PV panels.
Yeah but I gotta say that building a setup like the author describes is fun. Heinous bugs aside, at least.
…and many European countries allow connecting these to the domestic mains via micro-inverters without explicit permission or certification by a licensed installer.
That’s pretty cool! I don’t think the USA has anything like that yet, at least not that I’ve heard of. Maybe in some places…?
If the goal is partial autonomy and the ability to power certain devices even through extended blackouts…
Yeah I did some investigation into home battery systems but rapidly concluded that for my purposes it was not worth it. Where I live small power glitches do occasionally happen but long blackouts are fairly rare, maybe 0-2 per year that last more than an hour. Plus the power company doesn’t have different rates for on-peak or off-peak energy so a battery system won’t really save me money by time-shifting. Maybe someday, but for now it won’t do much that can’t be done by a couple UPS’s and some candles.
…there are likely upcoming modifications to the roof, so we’d rather get those out of the way before slapping 10kWp of panels on there only to have to move them a year later.
Big ol’ mood. I procrastinated on getting my own solar system because I knew the roof had to be replaced soon anyway.
I sympathize! I tried to do something similar once (12V power for exterior lights though) and also was foiled by a piece-of-crap charge controller. Never did get it working properly TBH, though someday I’ll do something with the solar panel. In the end I own my house so I just ended up getting residential solar panels installed on the roof. No regrets.
It’s not obvious because of the way our eyes work, but full sunlight is something like 100x brighter than a brightly lit room, and 1000x brighter than a dimly lit room.
Temperatures reported by batteries themselves are often (but not always) from sensors inside the packaging, so are commonly warmer than you’ll measure from the exterior of the battery. In this case though, that’s a pretty big difference, so you’re probably correct.
Unless they are tinted, shouldn’t be a concern. Window glass does block IR and UV radiation but afaik that’s not a particularly significant difference, maybe like 10% of the total energy. And I don’t think most solar panels can make use of those wavelengths anyway?
…or maybe I’m very wrong?!? Dang. This is weird!
Other random bits and pieces:
Similar to your earlier point, your eyes aren’t very good at estimating the light attenuation from a window. At least with modern triple-glazed windows, the difference is definitely visible to the naked eye if you partially open the window and look at a surface illuminated side by side directly by the sun and through the glass. I expect such a visible difference translates to 2-digit percentage attenuation. I wonder if the observed measurement can be explained by the combination of that with the cells’ nonlinear behaviour. (especially towards the minimum productive radiation threshold end on the cloudy day)
The conclusion I’ve reached with regards to domestic-scale energy collection is “go big or go home.” Except in very niche applications, it’s almost certainly not worth the expense and use of materials to bother with anything smaller than the classic 200-400W scale PV panels. Even if you don’t own your home, you can now get balcony-mounted full-size panels, and many European countries allow connecting these to the domestic mains via micro-inverters without explicit permission or certification by a licensed installer. (The limit tends to be around 600-800Wp max-spec backfeed.) This seems to be about the smallest scale that starts making any economic sense, and the tech is mainstream enough that it actually works without hassle.
If the goal is partial autonomy and the ability to power certain devices even through extended blackouts, things rapidly become expensive, but again there are economies of scale. I haven’t researched enough to see if there are robust, inexpensive, off-the-shelf PV-fed inverter-chargers which don’t backfeed more than those 600-800 Watts (or anything at all), but act as UPSes for downstream devices. It certainly seems like that’s a category that should exist. (If PV generation power exceeds maximum allowed backfeed + consumption, you’d need some algorithm for balancing between maximum PV energy and allowing battery discharge during times of no/low generation versus maintaining a minimum blackout bridge time.)
(Disclaimer: we’re running a 2-panel micro PV setup with a inverter, no battery. A pair of 375Wp panels screwed to the south wall of the house, connected to 600Wp inverter. We opted for this for the moment as although we own the house, there are likely upcoming modifications to the roof, so we’d rather get those out of the way before slapping 10kWp of panels on there only to have to move them a year later.)
Dang, I guess you’re right. Never really thought of it that way; triple-glazed windows would definitely make a difference.
Yeah but I gotta say that building a setup like the author describes is fun. Heinous bugs aside, at least.
That’s pretty cool! I don’t think the USA has anything like that yet, at least not that I’ve heard of. Maybe in some places…?
Yeah I did some investigation into home battery systems but rapidly concluded that for my purposes it was not worth it. Where I live small power glitches do occasionally happen but long blackouts are fairly rare, maybe 0-2 per year that last more than an hour. Plus the power company doesn’t have different rates for on-peak or off-peak energy so a battery system won’t really save me money by time-shifting. Maybe someday, but for now it won’t do much that can’t be done by a couple UPS’s and some candles.
Big ol’ mood. I procrastinated on getting my own solar system because I knew the roof had to be replaced soon anyway.