A critical part of my project was power management.

Here are a few words of "REX" regarding these aspects.

The wind only weather station has now been operated on a daily basis (24/24) for more than 2 months and has performed sensor acquisition and transfer of data over Lora (2.5km range) every two minutes during day and once every 1 hour during night.

All this being operated on a single 18650 Li-ion battery charged with a small 2W 6V solar panel.

Here is the graph of the panel voltage captured during a few days :

We can clearly see the repeating pattern where the panel outputs 0V during night and boosts up to 7V during full sun.

If we zoom here is the detail:

1. during night I automatically perform data sampling once every 1 hour to save power, at sunrize voltage is slowly climbing while at sun set it slowly decreases 
2. during a few hours the solar charger is lacking efficiciency (it's a linear charger...) and the panel falls down to 5V but charges the battery until full charge where the panel recovers and outputs full power (7V)
3. but even during full charge when a cloud hides the sun, voltage may drop a little...

In conclusion, the system seems to be very well "balanced" with good margin to allow operation even during winter time...

In case of (unexpected) battery depletion I could easily change the sampling rate to 4 min instead of 2 min during winter season!  But we will see this after a few months !

Currently the fast 2min acquisition is not a concern, even during very cloudy days the battery was charged enough to power the weather station.