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food:refrigeration:power [2024/05/09 17:37]
frater_secessus [charging from solar] 		food:refrigeration:power [2024/05/09 17:55]
frater_secessus [power and duty cycle]
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 ===== TL;DR ===== ===== TL;DR =====
  
-  * compressor fridges are a part-time load;  as a rule of thumb we can assume the compressor will be running 1/3rd of the time.+  * [[food:refrigeration#compressor_refrigeration|compressor fridges]] are a part-time load;  as a rule of thumb we can assume the compressor will be running 1/3rd of the time.
   * they will consume a given number of Wh (Watt-hours) over a 24-hour period   * they will consume a given number of Wh (Watt-hours) over a 24-hour period
   * you must have at least enough charging capacity to replace at least that amount of Wh   * you must have at least enough charging capacity to replace at least that amount of Wh
-  * and have enough bank to make it through periods where charging is absent+  * and have enough battery bank capacity to make it through periods where charging is absent
  
  
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 60w x 0.33 duty cycle x 24 hours = **480Wh** required each day to run the fridge.  We will use the 480Wh example from here on, and assume this is the only load.  In real life the fridge will be only one part of your [[electrical:12v:dailypowerrequirements|daily power requirements]].  We also assume the fridge will be run off 12vdc.  If you are running it off an inverter then add ~20% to the Wh requirements to make up for inversion losses.   60w x 0.33 duty cycle x 24 hours = **480Wh** required each day to run the fridge.  We will use the 480Wh example from here on, and assume this is the only load.  In real life the fridge will be only one part of your [[electrical:12v:dailypowerrequirements|daily power requirements]].  We also assume the fridge will be run off 12vdc.  If you are running it off an inverter then add ~20% to the Wh requirements to make up for inversion losses.  
  
 +==== why think about it 24hr terms? ====
  
 +
 +* offgrid power consumption is often considered in terms of daily cycles
 +* solar power occurs in daily cycles
 +* overlanders and others who travel often (and for whom alternator charging is practical) think of driving in hours per day
 ===== battery bank capacity ===== ===== battery bank capacity =====
  
-The battery bank capacity is dependent on a few factors:+The battery bank capacity requirement is dependent on a few factors:
  
-  * how deeply the chemistry can be discharged (~50% for lead, ~80% for LiFePO4)+  * how deeply the chemistry can be discharged (~50% for [[electrical:12v:deep_cycle_battery|lead]], ~80% for [[electrical:12v:drop-in_lifepo4|LiFePO4]])
   * nominal voltage (12.0v for lead, 12.8v for LiFePO4)   * nominal voltage (12.0v for lead, 12.8v for LiFePO4)
   * days of "autonomy" (discussed separately)   * days of "autonomy" (discussed separately)
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 Charging from [[electrical:solar:gentle_intro|solar]] is predictable //on average// if one knows where/when one will be camping.  Because December has the lowest insolation in the Northern hemisphere we base our panel requirements on that month.  If you are not full-timing then use the month closest to winter solstice.   Charging from [[electrical:solar:gentle_intro|solar]] is predictable //on average// if one knows where/when one will be camping.  Because December has the lowest insolation in the Northern hemisphere we base our panel requirements on that month.  If you are not full-timing then use the month closest to winter solstice.  
  
-You will need to [[electrical:solar:pvwatts|calculate how much sun]] (hours of Full Sun Equivalent, aka "kWh/day") is available in your actual wintering spot, but we will use Belle Fourche, South Dakota since it is the geographical center of CONUS.  +You will need to [[electrical:solar:pvwatts|use PVwatts or similar]] to calculate how much sun (hours of Full Sun Equivalent, aka "kWh/day") is available in your actual wintering spot, but we will use Belle Fourche, South Dakota since it is the geographical center of CONUS.  
  
 December in Belle Fourche has only 1.52 hours of FSE.  It would take ~375w of panel((flat-mounted, MPPT controller, LFP bank)) to replace 480Wh year-around. (480Wh / 1.52 hours of FSE / 0.85 overall efficiency) December in Belle Fourche has only 1.52 hours of FSE.  It would take ~375w of panel((flat-mounted, MPPT controller, LFP bank)) to replace 480Wh year-around. (480Wh / 1.52 hours of FSE / 0.85 overall efficiency)
food/refrigeration/power.txt ยท Last modified: 2024/05/09 17:57 by frater_secessus

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