How much load can be served from 1m² of sunlight • Hacker News Board

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

#31

Post by sfblah » Wed, Nov 03, 2021, 4:55 PM UTC

dreamcompiler wrote: post #22

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.

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.

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

#32

Post by 0xfaded » Wed, Nov 03, 2021, 4:55 PM UTC

na85 wrote: post #17

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.

Don't DC-DC transformers use AC internally?

Not necessarily. See voltage doubler:

https://en.m.wikipedia.org/wiki/Voltage_doubler

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

#33

Post by turtlebits » Wed, Nov 03, 2021, 4:57 PM UTC

dylan604 wrote: post #13

lmilcin wrote: post #6

Earlier quoted context omitted.

It is interesting concept for a blog post but ruined by very inefficient implementation. I would expect orders of magnitude more work done on ~20W. Also parsing a compressed 10MB JSON seems like an unusual request. It would maybe be more fun to put a Hello World or Pet Store and get some numbers that will be more relatable to a regular developer.

You must have a very low level of expectations of your fellow HN reader if you think that anything above a Hello World tutorial is relatable to a regular developer.

The test is for a web server, so you're optimizing for throughput on limited power, a static site would seem to be the best test.

If you want to test CPU load, the author should have tried Prime95 or some other similar test.

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

#34

Post by Amorymeltzer » Wed, Nov 03, 2021, 4:58 PM UTC

The point of the piece is at the bottom:

>By increasing our utilization rate, we have increased power efficiency by a factor of 6.

>Economies of scale are more important than intuition would suggest for efficiently serving requests

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

#35

Post by daneel_w » Wed, Nov 03, 2021, 5:03 PM UTC

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.

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

#36

Post by rexreed » Wed, Nov 03, 2021, 5:08 PM UTC

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

I thought that was factored in when he talked about 3 full-hours of 200W across the full day? The day in Australia is certainly longer than 3 hours, so I figured that accounted for panel inefficiencies, indirect sunlight, and other such things. But could be wrong. Not sure how the 3 hours was calculated, but I am sure some solar calculators will take your location, average annual sunlight, efficiency and spit out an "effective daily solar hours" value that can be multiplied by the indicated solar panel wattage.

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

#37

Post by ananonymoususer » Wed, Nov 03, 2021, 5:11 PM UTC

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 batteries.

The remnants of the system can still be seen here: http://jsl.com/solar

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

#38

Post by rzimmerman » Wed, Nov 03, 2021, 5:11 PM UTC

It would be interesting to set up a server/PC that throttled The CPUs/GPUs by power use rather than thermal readings. It’s analogous to the burst credit system used on some EC2 instances, but it would be a cool kernel or hardware feature for devices that are completely solar powered.

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

#39

Post by colejohnson66 » Wed, Nov 03, 2021, 5:12 PM UTC

jagger27 wrote: post #25

na85 wrote: post #17

Earlier quoted context omitted.

Don't DC-DC transformers use AC internally?

The point is to remove the laptop power brick. Let's say the laptop charger is 90% efficient, which is fairly typical. The post claims their 12VDC to 240VAC inverter is 92% efficient. A 12VDC to 20VDC voltage booster would only have to be >83% efficient to beat that setup.

Which isn’t that hard for a switch mode converter. Those are usually 85% or more IIRC.

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

#40

Post by louwrentius » Wed, Nov 03, 2021, 5:14 PM UTC

I run my static blog on a Raspberry Pi3B+ Powered by solar [0] and it doesn’t even flinch when it is hit by hacker news.

It idles at around 3.1 watts and that power usage includes a step down converter from 12 volt to 5 volt.

A bunch of lead acid batteries of various capacities provide backup. Lead acid is a terrible choice because charge times are long, but it is sufficient for now.

Just see it as performance art.

[0]: https://louwrentius.com/this-blog-is-now-running-on-solar-po...