if you only transmit when you have sufficient charge it will keep on transmitting on a sunny day… and never transmit on a rainy day.
So you must have another form of interval timing,let’s say , check charge every hour during day, if sufficient transmit if not wait till next cycle, preferable use an RTC+lightsensor for interval timing.
At night you have another problem, the charge will be less and less (no Sun 
… So you need enough energy to transmit at night too.
The chip/module you found is ok I think… 2x 10F should probably work, but your tracker uses to much power (80 mA 
)
see the 5205 for example