Who has solar power and storage expertise?

"Rusty Vandura - www.tinyurl.com/keepoppo" (rustyvandura)
09/05/2020 at 14:20 • Filed to: None

I’d like to set up a self-contained power bank that can provide 500W 24/7. Charge during the day when the sun’s up, and discharge overnight when the sun’s down. Actual draw is about 450 watts, 24/7. Anybody can advise?

DISCUSSION (10)

Shane Moore > Rusty Vandura - www.tinyurl.com/keepoppo
09/05/2020 at 15:25

What voltage will you be running at? 12vdc, 24vdc or do you need to invert it to 120vac? I’ve got a autonomy calculator At work I’ve made for our re mote sites. Most are not near that draw but I can plug it in and see what is recommended.

Rusty Vandura - www.tinyurl.com/keepoppo > Shane Moore
09/05/2020 at 18:51

120 VAC

Shane Moore > Rusty Vandura - www.tinyurl.com/keepoppo
09/05/2020 at 19:07

That makes the battery requirements easier but adds an additional component. Two follow up questions:

1. Where do you live so I can calculate for average sun exposure?

2. What will you be powering with this?

2 1/2. Permanent install or portable?

sn4cktimes > Shane Moore
09/05/2020 at 19:32

Ooooo. Nifty that someone here has the know how. If you feel like doing another set I live in Calgary, Alberta. And my roof slope on one side is west with a very slight south inclination. The other side being east with a slight north inclination. 120VAC, solar (don’t think we’re allowed any wind turbines in city limits... I’d drill a geothermal if allowed), so permanent panels. Is it more cost feasible these days to battery store or just dump back into the grid?

Shane Moore > sn4cktimes
09/05/2020 at 19:53

All of my experience is either stand-alone systems that didn’t have shore power and needed to run on solar during the day and battery at night or l ong periods of high cloud cover. OR it has shore power but a storm has taken it out and needs to run until it is restored. Most of the times the requirements were 14 days of autonomy for a 24vdc system @ ~5A.

Said all that to say, I have no experience in putting it back into the grid. It would be interesting to look into it but I believe it requires certain equipment. A coworker at work tried to build his own and ended up with a large fire in his shed.

I can look at your requirements Tuesday at work. What exactly are you trying to power? Average Watts or Amps would also be required for a good recommendation.

Rusty Vandura - www.tinyurl.com/keepoppo > Shane Moore
09/05/2020 at 22:43

1. 5.58 hrs/day (94546)

2. Folding at Home Server

3. Does not need to be portble.

4. I just calculated that my F@h server costs $78-100/mo in electricity, which is a bit startling.

sn4cktimes > Shane Moore
09/06/2020 at 01:52

Hmmmm, without grid support my case might no t be worth calculating. It would be for normal house stuff. TV, laptop, desktop, lights; but also stuff like the fridge and oven and stove. So the amperage could be quite low for most of the day but there’s going to be some significant spikes in there. Plus I guess it’d ave to be 240V to tie into the panel as several things are 220/240. I know our microwave is on a 120VAC 30A, our stove is 240VAC at 30amp... so yeah. I doubt any solar system could fully cover it at a peak usage scenario.

Shane Moore > Rusty Vandura - www.tinyurl.com/keepoppo
09/08/2020 at 09:32

OK, That is quite the power draw from your computer. Here are the raw numbers from my calculations:

This will be based off of 12vDC but obviously can be scaled accordingly for 24v-48v if that would be more cost effective.

The DC amperage to get 500w @ 120vac would be 45-50A depending on inverter efficiency .

1,180 Amp Hours per day of Power would be needed.

~2,000 Amp Hours of Battery Power would be recommended in order to not discharge the batteries below 50% daily to preserve battery life.

You would need up to 5000 watts of solar panels. So 50 100w solar panels, and scale from there.

Now Disclaimer , this calculator was built for oil field applications which means it is very conservative with the calculations. It has a large margin of error built in. This means you could get away with half of what is suggested and turn off the load every 2-3 months in order to get full storage back. Only risk you would run is shortened battery life.

Now my suggestion....

Go with about a 35 00 watt system and 1200 amp hours of storage and scale from there .

You can estimate $1 per watt on solar panels and $1.50 per amp hour on AGM batteries.

I honestly don’t know the price for a solar controller this large but make sure it can be set for the battery you choose. A cheap controller can dry out an AGM by charging at the incorrect rate .

If you are simply plugging the computer into an i nverter that will be less than $500 for a pure sine wave inverter.

I’d budget another $1,000 for mounts, wiring, and any junctions you may need to parallel the panels.

Let me know any other questions you may have!

Shane Moore > sn4cktimes
09/08/2020 at 09:58

Hey Sn4ck, check out my response to Rusty and it should be relevant to your needs as well. The only difference would be an inverter that ties into the grid instead of directly to a device like his computer. It would cost slightly more.

sn4cktimes > Shane Moore
09/08/2020 at 13:22

Thanks!