Autonomous computer connected via GSM


#1

:red_circle: :construction_worker_man: work in progress :construction_worker_woman: :red_circle:

Bonjour,

The goal is to setup a solar powered computer connected to the net with a SIM card and run a web server behind tor. The machine should be up at all times but it’s not catastrophic if it is down for a day or two, as long as it’s not a recurring pattern and only happens in exceptional circumstances.

I know nothing on that topic: all valuable information comes from @obinou and all mistakes are mine :wink:

Cheers

Raspberrypi 3A+

Hardware

Estimations

  • Raspberrypi 3B+ needs 2.5W (and powers the SIII via its USB port) and operates at 5v therefore 0.5A (2.5W = 5v * 0.5A)
  • We assume the worst case scenario with amorphous solar panel is 24h at 0%
  • In the worst case scenario the battery will be drained 12Ah ( 0.5A * 24h )
  • The battery must therefore be 2 x 12Ah = 24Ah (because a battery advertised for XAh must not be discharged less than 50%)
  • The solar panels are sized according to the worst day of the year, 21 december with 5h of light and 19h with no light
    • 5h x 2.5Wh = 12.5Wh provided by the solar panels
    • 19h x 2.5Wh = 47.5Wh provided by the battery
    • The battery needs to be charged during the 5h, so the solar panels are actually required to produce a total of 12.5Wh + 47.5Wh = 60Wh during this day, that is 60Wh / 5h = 12W
    • Assuming amorphous solar panels only yields 20% when the weather is very cloudy, 12W in the worst case scenario requires 5 x 12W = 60W

Mounting

  • SIII connected to the computer Raspberry USB port for charge and network
  • Raspberry connected to the power bank
  • Power bank connected to the MPPT
  • MPPT connected to the solar panels

NUC

Hardware

Estimations

  • NUC needs 15W (and powers the SIII via its USB port) and operates at 12v therefore 1.25A (15W = 12v * 1.25A)
  • We assume the worst case scenario with amorphous solar panel is 24h at 0%
  • In the worst case scenario the battery will be drained 30Ah ( 1.25A * 24h )
  • The battery must therefore be 2 x 30Ah = 60Ah (because a battery advertised for XAh must not be discharged less than 50%)
  • The solar panels are sized according to the worst day of the year, 21 december with 5h of light and 19h with no light
    • 5h x 15Wh = 75Wh provided by the solar panels
    • 19h x 15Wh = 285Wh provided by the battery
    • The battery needs to be charged during the 5h, so the solar panels are actually required to produce a total of 75Wh + 285Wh = 360Wh during this day, that is 360Wh / 5h = 72W
    • Assuming amorphous solar panels only yields 20% when the weather is very cloudy, 72W in the worst case scenario requires 5 x 72W = 360W

Mounting

  • SIII connected to the computer USB port for charge and network
  • computer connected to the MPPT (? cable ?)
  • Battery connected to the MPPT
  • MPPT connected to the solar panels

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References