Real-world solar gain

[canuckrv]

I'm thinking of installing a 200w solar kit from Renogy. What could I expect in the real world, (semi-shaded site and horizontal panels) in the way of solar gain? 20amph a day? more? less? just trying to see if it makes sense to do the installation.

 

[Jayflight]

First off the capacity of solar is only as good as your battery and the reserve capacity. What type of battery are you using and what type of unit are you planning to install your solar on, which will be consuming the battery power? 200 watt is just a starting point for most requirements of small and mid range towables and vans.

 

[canuckrv]

I'm sorry but I fail to see what that has to do with the original question, which is what can I expect from 200 watts panel array under those conditions.

 

[Utclmjmpr]

Jayflight is right on,,you don't know what you don't know,, storage is as or more important than what you can produce.. Example: My brother has a two 12V battery bank and I have a 4 6V battery bank.. I installed a 4 100 watt panels because I have the CAPACITY to store it as it's being produced,, he does not,, we installed a three 100 watt panels on his and he is fully charged in the Arizona sunlight by ten AM from 50% to 100%.. Mine takes more time under the same conditions due to the increased CAPACITY that needs to be satisfied.. Any more panels on his rig would be a total waste of money..>>>Dan

 

[canuckrv]

I know my system all I don't know is what I can expect from a couple of panels. This would be a much better forum if people stuck to what is asked. There is another recent thread about the dunes around Yuma and he gets information on the wall. Just stick to the question instead of just spouting useless information.

 

[NY_Dutch]

You'll get something less than 200 watts under all but ideal conditions. How much less? No one can answer that without knowing more about the exact conditions and the complete system.

 

[Jayflight]

I know my system all I don't know is what I can expect from a couple of panels. This would be a much better forum if people stuck to what is asked. There is another recent thread about the dunes around Yuma and he gets information on the wall. Just stick to the question instead of just spouting useless information.

Well I am not trained in solving mysteries. For example If you have a 50 ah battery and have a day of low charge and have equal amounts of usage over the course of several days, which is probably not going to happen in the real world, you have less reserve than if you have a 200 ah battery or total amount of batteries. Again 200 watts is basically a starting point for most solar setups, unless you are just operating a light bulb, so to speak. I consider that a trickle charge setup.

 

[Utclmjmpr]

Even tho your attitude sucks,, this may help.. A 100 watt 12V panel under the best conditions will only deliver a max of 5.75 AMPS of power,, due the math..>>>Dan

 

[stillRV]

Plan on getting around 50% of what your panels are rated for.

I have 480W on my roof. It puts around 100-120ah into my (12v) batteries most days, in September-October in the midwest.

At that rate your panels would give you around 40-50ah a day.

Each installation varies so much, and also depends on the weather and what part of the country you are in and the ambient temperature and your losses in wiring. It's a difficult question to answer.

 

[Lou Schneider]

The big variable you're asking about is "partially shaded". This has two definitions, either the entire panel is uniformly in the shade or there is localized deep shading affecting only part of the panel.

If the panel is uniformly shaded the amount of power it produces is directly proportional to the intensity of the sunlight falling on it. But having part of the panel in deep shade while the rest is in full sunlight can be worse. Depending on whether the panel has bypass diodes around individual cells (few do, most only bypass individual columns or even just the entire panel) a deep shadow on a single cell can drastically reduce the output of an entire row of cells or even of the entire panel.

 

[Gary RV_Wizard]

From what I read here and elsewhere, really good performance yields about 80% of the rated watt output. "Partial shade" (whatever that means) is going to be less, maybe 60% or 40% or even 0% (see Lou's reply).

As for how many amp-hours you will get, how many hours of full sun will the panel receive each day? 2? 6? It varies by latitude and maybe the surrounding terrain too.

So, if it's 60% x 200W x 6 hours, that's 720 watt-hours. To charge batteries you will be feeding them at about 14v, so that's only about 50 AH.

 

[Ksouers]

I'm thinking of installing a 200w solar kit from Renogy. What could I expect in the real world, (semi-shaded site and horizontal panels) in the way of solar gain? 20amph a day? more? less? just trying to see if it makes sense to do the installation.

Too many variables to give an accurate answer. Your handle suggests a location in Canada, so with an unknown high latitude, the panels flat on the roof, in shade, I think you will be very hard pressed to get anywhere close to 20 amp-hours a day out of 200 watt rated panels.

Is that closer to the answer you were looking for?

Kevin

 

[solarman]

I'm thinking of installing a 200w solar kit from Renogy. What could I expect in the real world, (semi-shaded site and horizontal panels) in the way of solar gain? 20amph a day? more? less? just trying to see if it makes sense to do the installation.

your panel in full sun in the summer could yield anywere from 85 to 95% of rated output.
daily harvest would depend on where your are located and what time of year.
if you are in AZ in the summer, you could yield somewhere in the region of 1200 W/hrs per day.
same setup in the winter might yield 400 W/hrs.

shading a panel is the worst scenario, depending on the panel type could drop to 20% of rated output.
I have seen 350 W panels drop to 90 W when shaded..

No 1. rule for panels = NO SHADE

 

[Ex-Calif]

So, if it's 60% x 200W x 6 hours, that's 720 watt-hours. To charge batteries you will be feeding them at about 14v, so that's only about 50 AH.

This is the rule of thumb that I have used for years except I use 80% efficiency.

200 X 6 X .8 = 68 ah @14V.

In general a 200 a/h battery bank and 200 W of solar will run a smallish trailer with an estimated 40-50 ah consumption per day. You can probably go for a 3 day weekend with no sun and your bank will be mostly depleted.

Let's say you have a 150 a/h deficit on day 3. You still need 45 amps to run the trailer and have a 23 amp reserve - It would take about 6 days to charge the bank back to full without shore charging.

You have to adjust the collection period based on your latitude and time of year. Western deserts probably have 10 hours of collection a day and very little cloud cover in the summer.

 

[Contributor]

I have 2 x 100W Renogy panels with Renogy PWM controller. I use 2 x 6V GC2 batteries. In the summer, full sunny days I get about 10A at noon. Since we use up about 25A per day camping, our batteries are full by noon and won't accept the extra power. We use the extra power to run a small inverter and charge various devices for use at night. I have the panels in parallel on either side of the trailer. In the morning depending on the sun orientation, one panel gets more sun while in the afternoon,the other one does.
We were in the Sierras this past week and the sun was low in the sky and some tree shading. We still got all the power we needed and the batteries were full by noon. My shunt was reading 93% battery state in the morning and 100% by noon.

 

[Mark_K5LXP]

To nail that down to a hard number is literally impossible due to the vagaries of location - maximum possible illumination (insolation) minus local weather factors. There are solar websites that will calculate "average" power for a specific location and over the course of a year factoring local weather, +/- panel tilt, which will get you as close as you can reasonably expect for an estimate.

Another data point is to put up a panel of any size and watch it for a few weeks. Over that period of time you'll have at least a few days where the weather is as good as it gets, and you can use those peak days as the "best" you'll see in your location.

Mark B.
Albuquerque, NM

 

[cully]

Hey Canuck Man, maybe mind your frigging manners? This is not a bash the members forum. You're are confusing it with someplace other than here. Just a thought