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--- electrical:solar [2019/10/01 13:03]
frater_secessus [do you really need solar?]
+++ electrical:solar [2020/05/10 10:31]
frater_secessus [temperature]
@@ Line 80: / Line 80: @@
 ===== weather-related issues =====
+Weather and [[electrical:solar:shading|shading]] have serious effects on [[electrical:solar:output|solar output]].
 ==== cloudy weather ====
@@ Line 94: / Line 95: @@
 ==== temperature ====
+[based on [[https://www.reddit.com/r/vandwellers/comments/ggxusl/solar_on_a_roof_rack_or_directly_on_the_roof/fq5yvel/|this reddit post]]]
 Panels yield the most power in cold temperatures.  Since panels are dark and get very hot in the sun they are generally raised rather than directly mounted;  this allows air circulation/cooling underneath.
+===== mounting the panels =====
+There are a few issues to consider:
+  * solar cells get very hot in sunlight, typically 25deg C hotter than ambient temps. Rating lab tests are performed when the cells are 25deg C (0deg C ambient, freezing)
+  * [[electrical:solar:output#panel_temperature|Panel output is reduced when the cells get hot]]
+hot panels re-radiate heat onto the roof of the van. "On my white van (even with a 5" airgap) it is hotter in the
+shade under the panels than on the roof in direct sunlight." - secessus
+  * we prefer fewer holes in the van roof when possible
+  * "flex" panels cost ~2x as much as rigid panels and last for years rather than decades
+  * airgapped panels will add height for drive-through adventures
+  * taller racks will likely increase air drag and MPG, particularly if you drive fast
+**Mounting hard panels to a rack** increases airflow (thereby reducing heat-related power losses), reduces heat transfer, and minimizes the number of holes in the van roof.
+**Mounting hard panels directly to the roof** still allows some airgap (the depth of the frame) and the roof corrugations will allow some airflow in the direction of the "valleys". Taller Z-brackets may give a bit more airgap.
+**Mounting flex panels to the roof** allows some airflow in the corrugations but no airgap. Good news: panel derating won't be so bad because the heat is conducted to your van roof. Which is bad news if it's already hot in your van.
+Opinion:  [[opinion:frater_secessus:beginner_mistakes#buying_the_wrong_panel|Bonus rant]] on panel/controller selection.

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