Best solar Panel output, mounted verticaly on a wall facing south in Cornwall UK or flat horizontal on a flat roof

[Chadd]

Good evening which will produce the most Solar Panel output.

Mounted vertically on balcony railings facing south in Cornwall UK, or flat on a flat roof ?

While we wait for some new panels to arrive, we have a single panel laying flat horizontal on the south facing balcony.

It produces some output, I intend to mount the new panels on the south facing balcony railings angled upwards towards the sun.

Working out and constructing the angled mounts is proving problematic, so to get the system up and running, I wondered about mounting them vertical on the balcony railings for now which will be simple.

I can work out mounts to angle them towards the sun later

I did find some custom made balcony mounts but delivery is January : )

God Bless Chadd

 

[sunshine_eggo]

Assumed Plymouth:

Vertical and Flat:




Multiply the monthly hours by your array wattage for your average daily Wh. Vertical is roughly 50% more in winter (though still very little) and about 40% less in summer vs. flat.

You must not have any shading, partial or full, from sunrise to sunset.

 

[teal95]

How good are those estimates? Obviously calculating for sun angle, but are they reducing output for typical number of cloudy days? If so what are they using for output on cloudy days? Are they improving the output for horizontal on cloudy days?

I'm not being negative, I'm truly curious how detailed their calculations are. I'm in Michigan and the lakes make for a lot of clouds for November until the end of January. For me the amount of cloud cover can vary somewhat drastically 20 miles farther east or west because we're far enough east that that winter overcast can start thinning by the time it gets this far east from Lake Michigan.

 

[sunshine_eggo]

It considers weather for the city entered. It's only as accurate as the weather data available. On a day-to-day basis, they can be astoundingly inaccurate as weather patterns can be substantially different even over small distances; however, they do factor in "average" weather. In most cases, they're typically accurate when you look at the average or sum for the monthly harvest.

Do you have any logged data showing improved output for flat panels on cloudy days? I don't. But when a 3kW array is only producing 200W on a cloudy day, and you get an extra ~25 Watts going from 29.6° to 0° tilt - I'm not convinced it's meaningful.

PVWatts uses the last 30 years of weather data. It looks at every hour of every July 11th over that 30 year period (and every other day), calculates the average weather on that day, and then selects the day that most closely matches the average calculation. It considers available solar on an hourly basis.

You can download that hourly performance data. I've done some random samples for my location, and they are representative of what I frequently see - clear mornings through peak solar with partly cloudy afternoons.

For every hour in the year, it reports:

Beam Irradiance (W/m^2)

Diffuse Irradiance (W/m^2)

Ambient Temperature (C)

Wind Speed (m/s)

Plane of Array Irradiance (W/m^2)

Cell Temperature (C)

It then uses all of the above to compute the DC Watts produced by the array and the AC watts available after conversion efficiencies for every hour of the year.

But again... it's only as good as the weather station is for your location. If you have a weather app on your phone for your location, and it typically reflects the conditions you observe, I would expect it to produce good AVERAGE results.

 

[nwmark]

Hi. I live in Washington state Close to the 49 parallel, We get plenty of sun in the summer. You can even put panels on a north facing roof and they will work. However in the winter it is another story. You have to place your panels to squeeze all the energy you can from those limited winter hours. Tilt your panels at the parallel you live at on your roof. Leave enough space between panels to prevent shading of one panel to another, in my case that was about five feet. Panels are more efficient in colder weather, which will help in squeezing out that energy during those light restricted hours

 

[nwmark]

Hi. I live in Washington state Close to the 49 parallel, We get plenty of sun in the summer. You can even put panels on a north facing roof and they will work. However in the winter it is another story. You have to place your panels to squeeze all the energy you can from those limited winter hours. Tilt your panels at the parallel you live at on your roof. Leave enough space between panels to prevent shading of one panel to another, in my case that was about five feet. Panels are more efficient in colder weather, which will help in squeezing out that energy during those light restricted hours

 

[Danke]

Play with the software, but generally it seems for someone with limited space (if you can afford it) is more panels spaced closer together vs. optimum angle spaced further apart to produce more electricity.

 

[Chadd]

Thank you for the advice and the application to see comparisons great : )

 

[Mithril]

Assumed Plymouth:

Vertical and Flat:

View attachment 112165 View attachment 112166


Multiply the monthly hours by your array wattage for your average daily Wh. Vertical is roughly 50% more in winter (though still very little) and about 40% less in summer vs. flat.

You must not have any shading, partial or full, from sunrise to sunset.

What site did you use for this? Just currious

 

[sunshine_eggo]

What site did you use for this? Just currious

Check @snoobler signature, #5.

 

[John Frum]

Check @snoobler signature, #5.

Haven't seen that old son of a gun around here in many moons.
Some say he went out in the desert and never came back.

 

[sunshine_eggo]

Haven't seen that old son of a gun around here in many moons.
Some say he went out in the desert and never came back.

I heard he had a reputation for insulting people.

 

[John Frum]

I heard he had a reputation for insulting people.

He is probably berating a cactus right now.

 

[Mithril]

Check @snoobler signature, #5.

Found the link, thanks!
For the 90deg (vertical) is that assuming freestanding bifacial or on a structure?
If it's assuming a structure, would a freestanding bifacial be roughly double?
I'm generally looking to optimize for winter, and "offgrid" (more like critical systems backup with lighter regular use at least as I build up the system over time)

 

[MaximusAnonus]

Assumed Plymouth:

Vertical and Flat:

View attachment 112165 View attachment 112166


Multiply the monthly hours by your array wattage for your average daily Wh. Vertical is roughly 50% more in winter (though still very little) and about 40% less in summer vs. flat.

You must not have any shading, partial or full, from sunrise to sunset.

man I don't know, these numbers (at least for my place) seem waaaay too positive
1kWh/m2/day in deep December? Here? that's like 20-30% more over my average on my old array

 

[Mithril]

man I don't know, these numbers (at least for my place) seem waaaay too positive
1kWh/m2/day in deep December? Here? that's like 20-30% more over my average on my old array

I assume all numbers are for no shading no clouds etc. The steeper the angle the less likely "no shading" applies for all hours of sunlight.

 

[MaximusAnonus]

I assume all numbers are for no shading no clouds etc. The steeper the angle the less likely "no shading" applies for all hours of sunlight.

No?

This irradiance calculator takes data collated over a 22 year period to provide monthly average insolation figures.

That implies it takes data from long term weather stations and then operates with that.

 

[sunshine_eggo]

He is probably berating a cactus right now.

And losing the argument

Found the link, thanks!
For the 90deg (vertical) is that assuming freestanding bifacial or on a structure?

It assumes neither. It reports insolation is on the face of the panel.

If it's assuming a structure, would a freestanding bifacial be roughly double?

No. Never. Bifacials quote max of 30% benefit from the back side assuming you have good sun, are at least 1m above the mounting surface AND the surrounding surfaces are reflective.

man I don't know, these numbers (at least for my place) seem waaaay too positive
1kWh/m2/day in deep December? Here? that's like 20-30% more over my average on my old array

Weather data is only good at the relevant weather station. It can vary wildly even a short distance away. Unfortunately, this is all we have for planning. Once must sanity check the data. With PVWatts, you can download hourly insolation data for the entire year.

 

[MaximusAnonus]

PVWatts

That's US only I'm afraid.

For EU we have this tool. It's kinda neat. Doesn't take weather into consideration at all IMHO.

 

[sunshine_eggo]

That's US only I'm afraid.

For EU we have this tool. It's kinda neat. Doesn't take weather into consideration at all IMHO.

PVWatts kinda works globally if you select a nearby weather station. I use the JRC site for the U.S. as well because it draws from the NSRDB. I particularly enjoy the off-grid performance tab for determining % of days battery is empty. I dont' see that it allows download of the hourly performance data like PVWatts.