Tuesday, November 29, 2022

Building My "Outage-Proof" Solar Office ...

I'm trying to be conservative here by over-estimating my power needs (based on averages) and not expecting too much from my solar panels.

The goal:  A system that can power my cable modem, router, computer, and monitors 24/7 relying solely on solar panels (and battery storage thereof). Which would mean that I could still work when the power was out, as long as the cable was not also out. Or, if the cable was out, use the stored power to run other household stuff during/after a storm.

The consumption:

Average cable modem usage -- 55 watts, but I'm going to say 60 in case I'm above average.
Average router usage -- anywhere from 6 to 20 watts, so I'm going with 20.
Raspberry Pi usage: The maximum I've seen asserted is 9 watts, but let's call it 10.
Average 19" LED TV usage: The biggest number I found was 32 watts. Let's call it 35, and I run two of them, so 70 watts.

That's a total of 160 watts. So, running all of that at full tilt 24 hours per day would be 3,840 watt hours.

The generation:

According to Solar Info World, "[i]n a location with an average of 5 hours of direct sunlight per day, a 100-watt solar panel will generate between 280 and 450 watts per day."

In Gainesville, this year, we had 14 hours and 3 minutes of daylight around the summer solstice (longest daytime), and will have 10 hours and 14 minutes of daylight around the winter solstice (shortest daytime). Obviously that doesn't automatically mean that much direct sunlight on the panels, but I'm going to assume toward the high end because I believe I'll manage more than five hours per day of direct sunlight.

I'm guessing I can get 400 watt-hours per day from each 100-watt panel.

Wow ... I'd need TEN PANELS to meet my power needs.


I'm not running all that stuff full-tilt 24/7, am I?

The router and modem are always on and doing their thing.

The computer and monitor are inactive eight hours a night while I sleep and could be turned completely off during that time. And probably for another four hours a day, they're idle and on standby or, under some circumstances (I'm leaving the house and know they'll be unused) could be turned off.

Since I've tried to be expansive about usage and conservative about generation, I think it's reasonable to say those things are only used 12 hours per day. So instead of 80 watts, I'm down to 40, which halves their watt-hour needs to 960, and brings total usage down to 2,880 watt-hours.

So I could probably make do with seven 100-watt solar panels, and eight would almost certainly do the job.

But I also want to overbuild, in case my math is bad or my expectations unreasonably high.

And while I do have a 160-watt panel already on the way, I'm not wildly sure about whether it would easily wire into another set of panels.

My solution: An 800-watt kit with two 400-watt panels, charge controller, cabling, etc. for $349.99.

I'm already $300 into solar at the moment, and not planning to throw another $350 at it immediately.

But in case anyone thinks keeping me chained to this desk even when the power is out is worth $350, I've added the thing to my Amazon Wish List.

No comments: