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--- electrical:solar [2017/10/09 13:08]
frater_secessus [do you really need solar?]
+++ electrical:solar [2022/01/28 19:12]
princess_fluffypants
@@ Line 2: / Line 2: @@
 ====== Solar power ======
+[Note:  a [[electrical:solar:gentle intro|gentle introduction to solar]] is also available]
 Solar (photovoltaic or PV) power is an excellent fit for 'dwellers and especially for boondockers.  It is silent, nearly maintenance-free, and requires no infrastructure or [[electrical:shore_power|grid]].  Downsides include expense, bulky panels, and the requirement for access to direct/unshaded sunlight.
@@ Line 12: / Line 14: @@
-===== do you really need solar? =====
+===== Do you need solar? =====
 Maybe not. If any of these conditions are met you probably don't need solar:
   * you stay in campgrounds or other places with access to [[electrical:shore_power|shore power]]
-  * you have a [[electrical:12v:lifepo4_batteries_thread|lithium]] or [[electrical:12v:carbon foam|carbon foam]] batteries that do not require [[electrical:12v:charging|smart (multistage) charging]]((carbon foam does require smart charging, but only 1x/month or so))
+  * you have a [[electrical:12v:deep_cycle_battery#lithium_chemistries|lithium]] or [[electrical:12v:carbon foam|carbon foam]] batteries that do not require [[electrical:12v:charging|smart (multistage) charging]]((carbon foam does require smart charging, but only 1x/month or so))
-===== practical considerations =====
+===== Practical considerations =====
   * [[electrical:solar:panels|solar panels]] take a lot of room and must not be shaded.  Where will you put them?
@@ Line 31: / Line 33: @@
   * how will you ensure your batteries don't run your batteries too low and damage them?
-===== scheduling your use of solar power =====
+===== Scheduling your use of solar power =====
 //When// you use power from your system can be as important as //how much// power you use.
@@ Line 42: / Line 44: @@
-===== things that affect solar power =====
+===== Things that affect solar power =====
   * Insolation (Intensity of sunlight)
@@ Line 55: / Line 57: @@
-===== how much solar? =====
+===== How much solar? =====
 Solar sizing has been moved to [[electrical:solar:sizing|its own page]].
@@ Line 76: / Line 78: @@
-===== weather-related issues =====
+===== Weather-related issues =====
-==== cloudy weather ====
+Weather and [[electrical:solar:shading|shading]] have serious effects on [[electrical:solar:output|solar output]].
+==== Cloudy weather ====
 **Cloud cover** can have paradoxical effects:
@@ Line 91: / Line 94: @@
 Dusty or snowy weather can cause a loss of output due to physical presence on the panels.
-==== temperature ====
+==== Temperature ====
 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 =====
+[based on [[https://www.reddit.com/r/vandwellers/comments/ggxusl/solar_on_a_roof_rack_or_directly_on_the_roof/fq5yvel/|this reddit post]]]
+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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