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--- electrical:solar:output [2023/02/11 12:42]
frater_secessus [insolation maps]
+++ electrical:solar:output [2024/02/21 11:49] (current)
frater_secessus [panel tilt]
@@ Line 14: / Line 14: @@
 Because the difference between lab and actual conditions is so large, some manufacturers also publish [[https://www.infiniteenergy.com.au/difference-between-max-power-stc-noct/|NOCT]]((Nominal Operating Cell Temperature)) specs, a //derated// (lowered) set of specs which might or might not be more indicative of what you will see in your use case.  NOCT is another tool in the toolbox, not gospel truth.
-In practical terms, it's common to see a maximum of 75% of STC under good conditions, more under great conditions, and much less under poor solar conditions.
+In practical terms, it's common to see a maximum of 75% of STC under good conditions, more under great conditions, and much less under poor solar conditions. And about half of that in winter.
+===== where and when =====
+The location and season both have profound effects on solar harvest. [[opinion:frater_secessus:panelsizesforinsolation#representative_areas|For example]], Phoenix AZ has **over 8.5x the amount of solar power** available in summer as Seattle WA in the winter.  For any given location, winter harvest will be about half of summer harvest.
+You can estimate solar harvest using [[electrical:solar:pvwatts|models like PVwatts]].
 ===== lack of demand =====
@@ Line 79: / Line 89: @@
 Tip:  you can work backwards from cosine calculations and observed power harvests to find your system's overall efficiency in different conditions.
+==== paradox of big solar ====
+All other things being equal, peak harvest will happen at local solar noon((rarely clock-noon)) when the sun is highest in the sky.
+This leads to a paradox:  some systems with [[electrical:solar:overpaneling#vs_battery_bank|relatively large arrays]] will have completed Bulk charging before solar noon and so do not have the chance to demonstrate full output.  In this scenario a smaller array could theoretically show higher //peak// output power but could not produce more overall Wh over the course of the day than the larger array.
@@ Line 86: / Line 101: @@
 //Insolation//((**In**coming **Sol**ar Radi**ation**)) is the the amount of solar power reaching the panels.  This can be affected by:
-    * hours of seasonal daylight
+    * short term
-    * clouds
+      * angle at which rays strikes the panel (angle of incidence) due to time of day.  At low angles effectively less panel area is exposed to sunlight.
-    * rain, fog
+      * amount of atmosphere the rays have to penetrate (less at solar noon, more at other times or anytime sun is relatively lower on the horizon)
-    * angle at which rays strikes the panel (angle of incidence).  At low angles effectively less panel area is exposed to sunlight.
+      * clouds
-    * amount of atmosphere the rays have to penetrate (less at solar noon, more at other times or anytime sun is relatively lower on the horizon)
+      * rain, fog
-    * air quality:  \\ smoke((http://www.cheaprvliving.com/forums/showthread.php?tid=26592&pid=333826#pid333826)),((http://www.cheaprvliving.com/forums/showthread.php?pid=331627#pid331627))
+      * air quality:  \\ smoke((http://www.cheaprvliving.com/forums/showthread.php?tid=26592&pid=333826#pid333826)),((http://www.cheaprvliving.com/forums/showthread.php?pid=331627#pid331627))
     * altitude (total irradiance ~+2.67%/1000')((https://www.sciencedirect.com/science/article/abs/pii/S1011134496000188))
     * humidity((https://www.researchgate.net/publication/338412686_Performance_study_of_Monocrystalline_and_Polycrystalline_solar_PV_modules_in_tropical_environments))
+    * long term - roughly speaking, you can expect ~half the harvest in winter compared to summer
+      * solar angle due to **time of year**.
+      *  hours of seasonal daylight
 Even the altitude and type of clouds can affect harvest:
@@ Line 124: / Line 143: @@
 ==== using PVWatts to find FSE and daily harvest ====
-You can use [[https://pvwatts.nrel.gov/index.php|PVWatts]] to find solar info for a particular place and month.
-=== pick a location ===
-First, pick a location using the search bar:
-{{https://img.mousetrap.net/misc/pvwatts0.jpg}}
-=== SOLAR RESOURCE DATA ===
-use the right-arrow graphic to accept these defaults.
-=== system info ===
-We need to make a couple changes here
-  * your array size in kW (200w = 0**.**200kW, mind the decimal!)
-  * if your panels are flat (most are) adjust tilt to zero
-  * accept the default losses for MPPT systems.  PWM systems should use something like 30%
-{{https://img.mousetrap.net/misc/pvwatts-annotated.jpg}}
-=== results ===
-The first column is kWh/square meter/**day**, AKA Hours of Full Sun Equivalent.
-The second column is kWh harvested per **month**. To find average maximal harvest per day divide this figure by the number of days in that month.
-Example:  In January in this location the system could make 17kWh.  17 divided by 31 days = 0.548kWh/day,  (548Wh/day).
-{{https://img.mousetrap.net/misc/pvwatts2-annotated.jpg}}
+this subsection has been [[electrical:solar:pvwatts|moved here]]
 ==== insolation maps ====
 Insolation maps attempt to combine the effects of the variables above to estimate hours of **full sun((1000W/square meter)) equivalent** (FSE) per day for large areas.  This can be helpful when planning [[camping:snowbirding|moves around the country]].
@@ Line 226: / Line 203: @@
 Pro:
-  * +30% daily harvest is possible, depending on the sun's position((peak harvest may be much higher at some times but daily harvest is more applicable for offgrid vanlife))
+  * optimal tilt will increase harvest when the sun is low and skies are clear.((peak harvest numbers are more impressive but of less import.))
-  * can be used to increase harvest if roof space is maxxed (cannot add more panel)
+  * can be used to further increase harvest if roof space is maxxed (cannot add more panel)
 Con:

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