Solar Energy Questions

[rm.w/aview]

Our power needs vary greatly among us and with this I've seen suggested ratios of solar panel to battery bank vary from 1:1 to 3:1, with the common thought of accounting for weather conditions being prevalent. Now these weather conditions will vary among the areas that we visit while we chase our own definition of good weather. Some will see most of the lower 48 and 1/2 dozen provinces while others will stay in a region they enjoy most, perhaps 1/2 dozen states. I ask you who remain in an area, defined by states or time zones, about what you've seen in the sky and our solar source, seasonal weather aside. Is it/ has it been clear & blue or more of a white sky, with blue seen through a mist? Have the "stripes" in the sky expanded to create a condition that didn't exist before the fly overs? Solar tech has improved greatly and probably compensates for any of this, so I'm interested in your visual observations as I'm not in an area long enough to have a valid viewpoint.

 

[John61CT]

Look for good solar maps

https://www.google.com/search?q=usa+map+insolation+OR+radiation+season

All that matters is

energy hitting the panel

relative angle to the sun

and temperature.

Light clouds not blocking the sun are irrelevant, contrails even more so

 

[jimindenver]

hmmmm

Light clouds can have a huge impact depending on the panels you chose. This isn't something seen on Google, only side by side testing reveals a panels low light abilities vs another.

As I have posted before, it isn't a watts to Ah ratio that matters. It is the ability to produce more than you need in the worse conditions that you will be in. That means the further north you camp, the more watts you need. Camp in the winter? More watts. Camp in the Colorado high country where it clouds up every day around noon? More solar. Camp during the monsoon? OMG lots more solar AND a generator back up.

So again it is the ratio of watts to your needs in the worse conditions. Need 100 watts in ideal conditions could mean 300 in bad.

 

[John61CT]

Sorry if I wasn't clear.

I just meant fluffy or wispy stuff in the sky, but that is not between the sun and your panels, is not going to impact their output.

 

[frater secessus]

Our power needs vary greatly among us and with this I've seen suggested ratios of solar panel to battery bank vary from 1:1 to 3:1, with the common thought of accounting for weather conditions being prevalent.

There are two conditions addressed by the ratios:

1. deep cycling the bank and being able to getting it back to full charge quickly (important); and/or,
2. maintaing the minimum charge current specified by the battery manufacturer (less important)

Folks who aren't deeply cycling their batteries might not even need 1:1, as others have pointed out. Example:  when I am hooked up to shore power my batteries only get about 130W from my little DIY converter.  That's 130:220 ratio, much less than the 1:1 minimum ratio.  But since it is on 100% of the time and I am running other loads off 110vac it works fine.

About the weather, in good conditions and full load my panels make about 75% of rated power.  
In partly cloudy weather they make somethuing like 30-60% of rated power.  A whole lot of variability here.
In overcast skies they make ~15% and in dark overcast (like daytime thunderstorms) about 10%.

Contrails and other high cloud formations don't make a big difference because they don't throw shadows;  when clouds are low and cause visual dimming they affect output.