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--- opinion:frater_secessus:how_much_excess_solar_power [2022/12/14 18:50]
frater_secessus [system efficiency]
+++ opinion:frater_secessus:how_much_excess_solar_power [2025/12/24 22:58] (current)
@@ Line 1: / Line 1: @@
 DRAFT
+FIXME
 ====== How much extra solar power do I have? ======
@@ Line 9: / Line 11: @@
-===== Pareto summary =====
+===== TLDR =====
@@ Line 21: / Line 23: @@
-===== empirical testing =====
+===== direct testing =====
-===== observation and prediction =====
+Plug it in and see if the solar can support it [[electrical:solar:offthepanel|without affecting the battery bank]].  Easy peasy.
+The downside is this is a YES/NO answer;  it tells you a specific load will run but does not tell you about how much power is actually available.  If you want to see the Bigger Picture then read on...
+===== prediction =====
-==== overall system efficiency ====
+==== looking up daily insolation (FSE) =====
-You can get a feel for overall system efficiency by
+Hours of Full Sun Equivalent (FSE) is a convenient way to think of the amount of sunlight reaching the ground over the entire day.  4.5 hours of FSE means 4.5kWh of power reaching the ground per square meter.
-   - watching your system over time, as described above
+To predict daily harvest we will use
-   - comparing real-time harvest to theoretical harvest
+  * FSE
+  * your panel wattage
+  * and your system's overall efficiency
-===== average power harvest for a given time/place =====
-==== theoretical power available ====
-=== predicted daily harvest ===
+==== calculating power available (W)  ====
-=== predicted harvest at a specific time ===
 Real-time harvest is a bit easier since there is no time component.  We are working in Watts (W) rather than Watt-hours (Wh). What we are doing is comparing the strength of sunlight reaching the ground (perpendicular) vs [[electrical:solar:output#zenith_angle|the cosine of the angle at which it actually strikes the ground]], or strikes a flat-mounted panel.
@@ Line 52: / Line 53: @@
 This cosine is [[https://www.esrl.noaa.gov/gmd/grad/solcalc/azel.html|calculable for a given time and place]].
-**Example**: if you have 200w of panels and calculated cosine is .70 then **140w of light is landing on your panels**.
+**Example**: if you have 200w of panels and calculated cosine is .70 then **140w of direct light is landing on your panels** in clear skies.
-==== system efficiency ====
+==== finding and using system efficiency ====
 For [[electrical:solar:output|various reasons]] your solar setup will not be able to harvest all the power landing on the panels. For systems with PWM controllers the percent harvested will be something like 70%.  For MPPT it might be 83%.  These constants will be placeholders you can use until you figure out your specific system's overall efficiency.

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