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--- opinion:frater_secessus:panelsizesforinsolation [2021/12/30 14:59]
frater_secessus [Table] fixed seattle alternator
+++ opinion:frater_secessus:panelsizesforinsolation [2022/07/20 16:40]
frater_secessus [Amount of solar wattage required per 100Ah of Pb] further reading
@@ Line 10: / Line 10: @@
 This page is a rough attempt to show how geographical location and meteorological conditions affect the amount of solar wattage one needs.
-**Reminder:**  available sunlight ([[electrical:solar:output#insolation|insolation]]) is expressed in Hours of Full Sun Equivalent (FSE) compared to lab conditions.  So an entire cloudy day might provide only 2 hours of FSE, meaning it would be the same amount of sunlight as 2 hours of full sunlight under lab conditions.  Historical weather info is also used to calculate FSE, so good/bad weather is already baked into the average.
+**Reminder:**  available sunlight ([[electrical:solar:output#insolation|insolation]]) is expressed in Hours of **Full Sun Equivalent (FSE)** compared to lab conditions.  So an entire cloudy day might provide only 2 hours of FSE, meaning it would be the same amount of sunlight as 2 hours of full sunlight under lab conditions (1000w/sq meter).  Therefore **2 hours of FSE = 2kWh**.((and 7.2MJ (megajoules) for our metric friends))  Multiply [FSE for the time/place] x [rated panel wattage] to see what see how many watts your system would harvest on average if it were perfectly efficient.((hint:  it's not)).  Example:  4 hours of FSE x 200w = 800Wh, or 0.8kWh, before various losses.((see Assumptions section at bottom for typical losses))
+Historical weather info is also used to calculate FSE, so good/bad weather is already baked into the average.
-Ambient temperatures also affect panel output, and that is silently factored into the bottom table.
@@ Line 36: / Line 39: @@
 ===== Amount of solar wattage required per 100Ah of Pb =====
-These figures have [[electrical:solar:output#panel_temperature|temperature-related derating]] baked in, then are rounded off to usable numbers.
+These are crude estimates about the panel wattage required to fully charge 100Ah of AGM from 50% DoD each day.  See the list of assumptions below the chart.
-Assumptions:((I think the charging assumptions from alternator and generator are too high;  I will revisit at some point and re-evaluate at 50% and 75% charging, respectively -- secessus))
-  * battery is discharged to [[electrical:depth_of_discharge|50% DoD]] nightly
-  * MPPT controller is 95% efficient
-  * PWM yields, overall, 85% of MPPT yield.  PWM yields will be quite close to MPPT yields when other forms of charging is present, as PWM will no longer be [[electrical:solar:pwm_tweaking|hamstrung by low Vbatt]].
-  * isolator charging is done in early morning, and discontinued when alternator no longer raises voltage.  The chart assumes at that point [[opinion:frater_secessus:charging_faster|~70% of charging will be done]].
-  * DC-DC (or generator) charging is is done in early morning, and discontinued when Vabs is achieved.  We assume at this point 85% of charging will be done.((adjust as necessary for your charging current))
-  * wattage listed as ''any'' means "any amount over 100w".
-  * solar-only charging the same number of amps into lithium would require about 15% less panel than lead.  Lithium can be charged successfully off alternator/generator only so no panel would be required.
 ^ Location       ^ [[electrical:solar:charge_controller#mppt|MPPT]] only  ^ [[electrical:solar:charge_controller#pwm|PWM]] only  ^ w/ [[electrical:12v:alternator|isolator]]  ^ w/ [[electrical:12v:b2b|DC-DC charger]] or [[electrical:generator|generator]]  ^
@@ Line 61: / Line 53: @@
 | Phoenix - Dec  | 369w                                                   | 434w                                                 | 184w                                       | 135w                                                                           |
 | Phoenix - Jul  | 149w                                                   | 175w                                                 | 74w                                        | 55w                                                                            |
+Assumptions:
+  * panel output is temperature-derated according to daily average high at each time/place
+  * **no other loads** other than charging are present
+  * AGM deep cycle battery is discharged to [[electrical:depth_of_discharge|50% DoD]] nightly and [[electrical:12v:charging|fully charged]] the next day.  Charging efficiency 90%.
+  * MPPT controller is 95% efficient
+  * PWM yields, overall, 85% of MPPT yield.  PWM yields will be quite close to MPPT yields when other forms of charging is present, as PWM will no longer be [[electrical:solar:pwm_tweaking|hamstrung by low Vbatt]].
+  * [[electrical:12v:alternator|isolator charging]] is done in early morning, //every// morning, at ~[[electrical:12v:battery_capacity|C]]/3((~33A, AGM max charging current)), and discontinued when alternator no longer raises voltage.((~14.4v?))  The chart assumes at that point [[opinion:frater_secessus:charging_faster|~50% of charging will be done]].
+  * [[electrical:12v:b2b|DC-DC]] (or [[electrical:generator|generator]]) charging is is done in early morning //every// morning, at C/3,((~33A, AGM max charging current)) and discontinued when Vabs is achieved((!4.7v)).  We assume at this point 63.3%% of charging will be done.  The practical difference between alternator charging and DC-DC or generator charging is the latter will charge all the way to Absorption voltage.
+  * [[electrical:solar:output#panel_temperature|temperature-related derating]] baked in based on monthly average high temperatures
+  * due to lower internal resistance **lithium will accept more charge from alternator/generator** than AGM by the time it reaches the charging source's voltage setpoint, thereby requiring somewhat less panel wattage. Likewise, flooded batteries will accept //less// than AGM and then require more panel.
+  * solar-only charging the same number of amps into lithium would require about 10% less panel than AGM due to better charging efficiency.  Lithium can be charged successfully off alternator/generator only so [[electrical:12v:mandatory_solar|no panel would be required]].
+===== further reading =====
+  * factors affecting [[electrical:solar:output|solar harvest]]

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