Solar efficency

[Tony N]

Sorry if this has been throughly discussed before, but I couldn't find it if it has.
We are considering the solar option on our build list, but are wondering what we can expect in terms of output when in various degrees of shade. If deep shade is the output decreased by 90%, 70%, 50%? How about dappled shade (50%), what can we expect? Not having to have electric would be a nice option, we don't plan on getting an inverter for high draw items (short microwave use), and would just get a suitcase panel if the rooftop seems too expensive. Looks like a suitcase would be roughly half the cost, more efficient, but more work to set up.
Thanks for any thoughts.
Tony

[ReagentGrade]

Tony,

Some things to may want to consider:

1) a 160w panel isn't terribly portable.

2) no one is likely to steal a rooftop panel

3) ETI's prices are in CAD. Amazon (portable) is in USD

4) the fixed panels work just as well on the road and in uncovered storage to keep you're battery typed off

5) if you usually camp in the shade, to can add a portable pretty easily.

6) adding a fixed panel later is a LOT harder than adding a portable panel later

Rich

[paulk]

Originally Posted by Tony N

Sorry if this has been throughly discussed before, but I couldn't find it if it has.
We are considering the solar option on our build list, but are wondering what we can expect in terms of output when in various degrees of shade. If deep shade is the output decreased by 90%, 70%, 50%? How about dappled shade (50%), what can we expect? Not having to have electric would be a nice option, we don't plan on getting an inverter for high draw items (short microwave use), and would just get a suitcase panel if the rooftop seems too expensive. Looks like a suitcase would be roughly half the cost, more efficient, but more work to set up.
Thanks for any thoughts.
Tony

From what I found researching this, about 10%-20% of the rated capacity in shaded spots. On the plus side, in shade, sun angle won't matter. A good rule of thumb is that the panel as a whole will produce a tad more than if the most shaded part covered the entire panel, so if you have a big leaf covering one part of the panel, expect 10%-20% even if the rest is in full sun. The resistance in the one bad part limits the entire output.

I added two panels to my build sheet to combat shade. I figured 2.5 amps would be enough for minimal partial use in bad conditions. If you don't use an inverter or anything plugged in, your fans will consume the most power (fridge, furnace, and MaxxFan).

Here are some numbers:
Maxxfan = 4 amps on max. Something like 0.2 amps on low.
Furnace = 2.6 amps (I think) when cycled on, so much less overall.
fridge on propane = even less (0.5 amp?)
LED lights = negligible

Obviously, you get far more bang for your buck on the first panel. Getting the second panel for what amounts to is 1.25 extra amps in bad conditions is something most people wouldn't get. I'm kind of questioning my own decision there in terms of financial trade off, but I do like the setup. I plan to camp quite a bit in shaded spots.

On an RV, I wouldn't worry too much about partial shading. Either you'll have full sun, or something like a tree/building/mountain will be covering a good part of the panels. There isn't much in between. It's not like on a boat where you have to worry about the mast, ropes, etc.

[citabria90]

Originally Posted by Tony N

Sorry if this has been throughly discussed before, but I couldn't find it if it has.
We are considering the solar option on our build list, but are wondering what we can expect in terms of output when in various degrees of shade. If deep shade is the output decreased by 90%, 70%, 50%? How about dappled shade (50%), what can we expect? Not having to have electric would be a nice option, we don't plan on getting an inverter for high draw items (short microwave use), and would just get a suitcase panel if the rooftop seems too expensive. Looks like a suitcase would be roughly half the cost, more efficient, but more work to set up.
Thanks for any thoughts.
Tony

While I don't have any direct experience with solar panels in the shade, it's my understanding that shade caused by tree branches, TV antennas, satellite receivers or air conditioners will dramatically affect the output of solar panels. This is because the individual cells within the solar panel are connected in series, and if shade falls across one of the cells, it effectively blocks the current flow. Kind of like the old series Christmas lights where when one bulb burned out, the whole string went dark.

Since there are usually 36 cells in a solar panel, just a small amount of shade is problematic.

I'd recommend doing some serious research if you think your solar panel will be shaded.

[Brian B-P]

Originally Posted by paulk

Furnace = 2.6 amps (I think) when cycled on, so much less overall.

Close enough... the specs say 2.4 amps.

[SeldomSeen]

Go here: https://handybobsolar.wordpress.com/...ging-puzzle-2/

Bob is a highly opinionated curmudgeon but has more experience than just about anybody. About 2/3 of the way down his "rv battery charging puzzle" are the photos and data you are looking for.

Glenn

[alanmalk]

I went through the same thought process and ended up adding a 150 watt panel to our camping equipment.

It came from Amazon, panel only with no legs or controller, to save money. I added my own "A" frame for angle adjustment, a couple of ground screws with lock and chain to keep honest people honest, about 40' of heavy, flexible wire so I could place the panel in the sunniest spot, and finally, an Anderson Powerpole connector for quick connection directly to the built-in controller.

I don't use it for short trips where the 200 Amp-Hour batteries will last nicely. I do use it in fall & early spring when the sun angle is low. (Saw my total charge triple in mid-October when plugging in the portable panel.) And I will probably take it this summer when we head to the Great Lakes area for a month - expecting much deep shade.

Haven't yet in 2 years pulled the batteries below 12.2. But we don't have very high power requirements such as coffee maker, microwave, toaster, hair dryer, etc.

You can always start with the Escape system and add a portable later after you gain experience. You might find no need to add extra power - or just the opposite.

--
Alan