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Output of solar panels depending on slope and azimut

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Adriaan Kragten:
Recently I found a very interesting website of PVGIS Europe. On this website you can find the output of solar panels depending on the country, the total peak power, the slope and the azimuth for every month of the year. I have written the small Dutch note: "Opbrengst van zonnepanelen in december afhankelijk van de dakhoek (slope) en de stand t.o.v. het zuiden (azimuth). This note can be copied from my website: www.kdwindturbines.nl at the menu KD-reports at the bottom of the list with reports. Figure 1 out of this note gives a direct impression of the effect of the slope and the azimuth for December. Although the note is in Dutch, this figure can be understood by everyone (dakhoek = slope). The figure gives the reduction factor for the output if the solar panel is compared to a panel with a slope of 75° and an azimuth of 0° in The Netherlands. December is the most difficult month for solar power at the northern hemisphere and therefore this month is chosen. But a similar figure can be made for every other month and every other country in Europe using the website of PVGIS Europe. For America, you have to chose a point on the map of Europe with the same latitude.

bigrockcandymountain:
susdesign.com has some great tools for North America on the same topic. I used their tools for slope planning on my rooftop solar.  I also used their overhang calculator to visualize how my overhangs would work on my south facing windows.  They worked out almost perfect.

My slope is 65 degrees in winter and 20 degrees in summer.  The winter should be steeper for good snow shedding.  Otherwise it works out well. 

The new panels on the shop are vertical (90 degrees) and do great in the middle of winter.  They wont make much power in june, but we usually have lots that time of year. 

taylorp035:
I use the NREL website for this.  It can output the monthly totals and is fairly customizable from just about every input you can think of.

https://pvwatts.nrel.gov/index.php

XeonPony:

--- Quote from: bigrockcandymountain on March 13, 2024, 09:01:36 AM ---susdesign.com has some great tools for North America on the same topic. I used their tools for slope planning on my rooftop solar.  I also used their overhang calculator to visualize how my overhangs would work on my south facing windows.  They worked out almost perfect.

My slope is 65 degrees in winter and 20 degrees in summer.  The winter should be steeper for good snow shedding.  Otherwise it works out well. 

The new panels on the shop are vertical (90 degrees) and do great in the middle of winter.  They wont make much power in june, but we usually have lots that time of year.

--- End quote ---

If you have a smart phone a great app is Sunontrack, it is a paid app, but has reality augmentation so gives virtual overlay of the sun at various seasons real time.

Used it a fiew times and is pretty accurate, and based on reviews around the globe

Adriaan Kragten:
I have written a similar note but now about the output in June which can be found at the same place on my website. The curves given in figure 1 of both notes are completely different. With both notes it is now easy to compare the output in December and June. In the second note, I have compared two systems. System 1 has 12, 400 W peak panels in the direction of east and 12 panels in the direction of west at a slope of 15°. System 2 has 24 panels in the direction of south at a slope of 60°. It appears that the gain in December because of the larger slope and the orientation to the south is more than the loss in June.

If the energy is supplied to the grid, energy supplied in the winter is much more valuable than energy supplied in the summer. So the finananciel output for a certain investment in solar panels and inverters is much higher for system 2 than for system 1. A disadvantage of system 2 is that you need a rather large distance in between the rows of panels to prevent that panels come in each others shadow. But if the ground is cheap, system 2 is still a better choice. System 2 also has as advantage that the ratio in between the energy supplied in December and the energy supplied in June is about a factor three higher than for system 1 and so system 2 creates less imbalance in the grid. System 2 also has as advantage that melting snow, leaves and dust are easier removed and so the panels of system 2 need less cleaning. The panels of system 1 are normally laid very close to each other and the ground below the panels will get almost no light and almost nothing will grow there. For system 2, a certain crop can grow in between the panels and so nature is more lively.

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