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How much load can be served from 1m² of sunlight

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Re: How much load can be served from 1m² of sunlight

#91

Post by ctdonath »

toddh wrote: post #78
wereHamster wrote: post #74

Earlier quoted context omitted.

I was recently traveling with a M1 MacBook, and had a 20W solar panel + a 24Ah power bank for charging. Worked like a treat for coding.

Can you elaborate a little more on your setup? That sounds interesting.

I do similar with gear from https://GoalZero.com, typically using a car-portable 100W panel + 100Wh battery with USB-C support when seriously traveling, and a briefcase-friendly 20W folding panel + same battery when mobile. Wait for specials at https://REI.com to get good prices.

Re: How much load can be served from 1m² of sunlight

#92

Post by ctdonath »

jacob019 wrote: post #10

You won't get 200W from a 200W panel in direct sunlight, but it will still generate some watts at other times, so it should work out. "A 4.6b year old yellow dwarf as a light source" loved that

Between experience and math, my rule is: on average, buffered with a battery, you'll get 10 watts out of a 100 watt panel (i.e.: 10% efficiency, all common conditions considered).

Re: How much load can be served from 1m² of sunlight

#93

Post by lazide »

bee_rider wrote: post #77
genewitch wrote: post #68

Earlier quoted context omitted.

Odroid H1/H2 iirc can run from like 10-22VDC, the issue is finding a solar panel that has an open circuit voltage less than 22V. I found a buck-boost that works with my old laptop and a "car charger" with my admittedly oddball solar panels, so this is possibly, but takes time shopping and reading specifications.

The design in the article (which does seem to have some redundant parts, so...) instead goes: Panel -> regulator -> battery -> inverter -> laptop So, the voltage of the panel shouldn't really matter too much, I think (I mean, you size the regulator input range as appropriate). OTOH, solar panels are a little magical from my point of view, so maybe that regulator ought to be replaced by some solarpanel specific thing,…

It isn’t a regulator, it’s a charger - depending on the design, you can get even higher voltage spikes. 12V batteries charge at 13-14V, but most chargers design for lead acid can get away with reallly really noisy voltage transients due to the way lead acid works. It’s a pretty insensitive chemistry and dampens them normally.

Some chargers with ‘equalize’ or even worse ‘desulphation’ can intentionally go even higher in voltage than normal charging voltages.

So basically ‘if you just assume it wouldn’t kill your laptop to directly connect it, you’re playing Russian roulette with your laptop’.

With a decent spec sheet (and oscilloscope) to verify nothing too crazy that the charger is doing, some decent power filtering capacitors, and good DC-DC power supply you’d be fine though.

Re: How much load can be served from 1m² of sunlight

#94

Post by lazide »

sfblah wrote: post #31
dreamcompiler wrote: post #22

Earlier quoted context omitted.

Or use a 20v MPPT with a higher-voltage panel (or two smaller panels in series) and skip the car charger.

Wouldn't the battery voltage be the controlling factor here? Probably could go with 2 12v batteries in series? I assume a 20v laptop charger is fine with that.

You really can’t assume much of anything here frankly. Voltages here are nominal, and open circuit voltages can be quite high, or when under load can drop quite a bit. MPPT charger will attempt to maintain and output voltage within it’s target range, but voltage transients and ripple can be a problem - they aren’t designed as a live power supply, they are design to charge huge energy sinks with specific chemistries (aka batteries), so they usually cut corners that would matter in this case but don’t for batteries.

Re: How much load can be served from 1m² of sunlight

#95

Post by lazide »

masklinn wrote: post #67
ananonymoususer wrote: post #37

I did this 20 years ago and ran the server for about 10 years. I down-scaled the server hardware when I transitioned to solar, but soon discovered that the low-power server just could not keep up with the demand. I upgraded to something in the middle that could handle a decent number of web users while still not using all the solar. I had 1280W of panels (16x80), a 1500W inverter, and three deep-cycle 12V 50AH batter…

What was the demand? 1200W seems like a lot, https://solar.lowtechmagazine.com runs on a 50W solar panel with a 168W lead-acid battery (non-deep-cycle so effectively 84Wh). However it gets to have fully static content, and benefits from relatively modern hardware: for under 2W it runs on a dual-core 1GHz ARM with 1GB RAM (and a 16GB SD card but it doesn't use anywhere near 16GB).

Keep in mind, 1200w would be maximum peak power consumption most likely (as you need to size for that, depending on how many seconds the chosen inverter could sustain above peak). A good sized gaming rig would require that type of peak consumption, even if 99% of the time it’s consumption maybe be zero.

Re: How much load can be served from 1m² of sunlight

#96

Post by lazide »

jacob019 wrote: post #24
dreamcompiler wrote: post #21

Earlier quoted context omitted.

Did you mean " except in direct sunlight"?

The nominal rating is a peak rating, in my experience the sustained output will be somewhat less, even in direct sunlight.

Nod, unless you are in a place on the planet with perfect insolation (which would still only happen a few weeks of the year), it will nearly always will be below nameplate rating. The nameplate rating/testing if ever done, is done in a test bed with artificial light and perfect angle.

Edit: I remember I did once get an above nameplate actual power output from a panel once - using MPPT, at high altitude, at the maximum insolation time for the year (mid-California in the mountains, right around the summer solstice). It only lasted for 20 minutes though.

Re: How much load can be served from 1m² of sunlight

#97

Post by lazide »

daneel_w wrote: post #35
tantalor wrote: post #19

What is the bottleneck is this system?

The detour of 12 volts -> mains voltage -> back to low voltage is a big one, for starters.

Also what most folks end up doing for convenience. It can be surprisingly inconvenient and expensive to source a power supply at 12v/24v/48v or whatever, and battery voltages are always nominal (think barely approximate), so you can’t get clean power regulated directly sufficient for running a computer. For instance, “12v” automotive voltages can vary from 8v to 15v during normal vehicle operation - like starting the vehicle, charging at full tilt on the highway, etc. a full battery can provide 13.7-14.8v depending on chemistry too.

Re: How much load can be served from 1m² of sunlight

#98

Post by cogman10 »

masklinn wrote: post #65
sfblah wrote: post #29

Earlier quoted context omitted.

For the load expected for pulling data from a simple redis cache, is an M1 actually the most efficient chip? Isn't the point of the M1 that it supports a bunch of complex workflows while remaining efficient? Aren't there even more power efficient chips out there that focus exclusively on simple integer operations, etc.?

> For the load expected for pulling data from a simple redis cache, is an M1 actually the most efficient chip? I think that's a good question with no trivial answer, there are certainly boards which consume significantly less energy than that and can serve traffic (using nginx and static content you can serve quite a lot on a watt or two, per https://solar.lowtechmagazine.com/2020/01/how-sustainable-is... ), however…

Mobile phone SoCs would likely be the way to go for the best processing per watt.

The problem really is one of "how much is enough" more than anything else. Assuming someone wanted to really optimize something like this, a specialty built ARM cpu with lots of cores at a low frequency would likely provide the most ability to act as web server with a small power budget.

Such SoCs, AFAIK, don't really exist. You don't need a particularly fast CPU for web service stuff. You certainly don't need all the mobile extras (AI chips, GPUs, etc). What you need more than anything is core count.

Re: How much load can be served from 1m² of sunlight

#99

Post by cogman10 »

ananonymoususer wrote: post #41
danuker wrote: post #2

Rather than inverting 12V DC to 240V AC and back, you could skip a step and use a laptop car charger, converting 12V DC straight to ~20V DC.

You could also use a desktop with one of these ATX power supplies that runs on 12VDC instead of 120/240VAC: https://www.cartft.com/catalog/il/2302

Looking at the size of this thing, I sort of doubt it's much more efficient than doing a DC->AC->DC conversion. In fact, I'll betcha that's exactly what's happening inside this beast to both get the right voltages and stabilize them.

Re: How much load can be served from 1m² of sunlight

#100

Post by tyrells »

consumer451 wrote: post #73
ananonymoususer wrote: post #41

Earlier quoted context omitted.

You could also use a desktop with one of these ATX power supplies that runs on 12VDC instead of 120/240VAC: https://www.cartft.com/catalog/il/2302

Wow, I was not expecting that price! Is this just a rare item or is there something particularity expensive inside it?

Definitely are cheaper options too: https://www.mini-box.com/picoPSU-160-XT
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