The authors "92%" efficiency calculations will be with the inverter and power supply at high load.
When drawing only 20 watts, I expect you'll see more like 80% efficiency, and maybe as low as 50%.
How much load can be served from 1m² of sunlight
61–70 of 141 posts
Re: How much load can be served from 1m² of sunlight
#62What if you ditch the OS and code the server on the bare metal?
The OS is very rarely the bottleneck.
Re: How much load can be served from 1m² of sunlight
#63Rather 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.
I wonder how much the efficiency loss from a laptop car charger would compare to just using something like a NUC -- IIRC some of their models have really wide input voltage ranges (12v-20v or something like that, depends on the model). The laptop is really just bringing a battery, compared to a NUC, for this application, and they are going panel->regulator->battery->converter anyway so the laptop battery seems redundant.
Re: How much load can be served from 1m² of sunlight
#64One question of great relevance is the change in the statistic implied by the article's title over the past couple decades, and the projected change in the decades to come. Is this Moore's-law-esque? If so, eventually, these concerns will be trivial. Is an asymptote approaching? If so, this metric becomes increasing relevant and crucial.
Re: How much load can be served from 1m² of sunlight
#65Adding the obligatory "what if M1" comment. Anandtech tested power draw of an M1 Mac Mini and found 4.2W at idle, 26.5W for the average multithreaded workload. 1/3rd idle power and the same power draw while running multithreaded benchmarks compared to the laptop serving a single client. Would be interesting to compare. https://www.anandtech.com/show/16252/mac-mini-apple-m1-teste...
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 if you factor in the need for actual CPU...
Re: How much load can be served from 1m² of sunlight
#66Earlier 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.?
Sure. "STM32L1 MCUs also feature the industry's lowest power consumption of 170 nA in low-power mode with SRAM retention. ". But I think we're looking for the 'most efficient' general purpose computer. https://www.st.com/en/microcontrollers-microprocessors/stm32...
Intel also made the quark which is a 486 that runs on a button cell battery, the same type that we'd call a cmos battery.
Re: How much load can be served from 1m² of sunlight
#67I 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).
Re: How much load can be served from 1m² of sunlight
#68Rather 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.
I wonder how much the efficiency loss from a laptop car charger would compare to just using something like a NUC -- IIRC some of their models have really wide input voltage ranges (12v-20v or something like that, depends on the model). The laptop is really just bringing a battery, compared to a NUC, for this application, and they are going panel->regulator->battery->converter anyway so the laptop battery seems redund…
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.
Re: How much load can be served from 1m² of sunlight
#69Re: How much load can be served from 1m² of sunlight
#70> With an idle load, this particular laptop draws 14W of power with the screen turned off. That's an extremely high idle power usage, I also have a laptop with a Ryzen 9 4900HS (the ROG Zephyrus G14, the only laptop with this chip, to my knowledge), and it idles around 9-11W with the screen on . Most of that is actually because of the RTX 2060 that's bundled with it, and won't turn off in Linux because Nvidia doesn't…
Check out https://gitlab.com/asus-linux/asusctl . It provides a cli mechanism for switching between igpu-only, dgpu-only, and hybrid (nvidia card sleeps unless called via prime). If you use version 3.x, everything is built into asusctl. With 4.x, they've extracted that functionality to supergfxd/supergfxctl (in the same project).
I'm currently using hybrid with PRIME offload and runtime D3 enabled, but no matter what, the runtime D3 status is indicated as "Not Supported".