I combined the simple solar controller code gist with the PingInt code from the stm8ef-nRF24L01 repository into a solar-nrf24 gist. This is experimental but for now it works.

The output from Pong looks like this:

Solar   710     556        0     96
Solar   710     556        0     96
Solar   710     556        0     96
Solar   710     556        0     96
Solar   710     556        0     96
Solar   710     556        0     96
Solar   710     556        0     96
Solar   709     556        0     96 

The text "Solar" and temperature from the collector and the storage sensors (by 10) are transferred as plain text.

This is what I use as a nRF24L01 receiver:

All relevant links are in the Gist comment.