On the pursuit of finding fun and unusual power sources to run the electronics with the help of the power management board I have looked into using the power from the air similarly how a crystal radio works without a power source. 

Although I have made a small alternation to the crystal radio concept. Namely, instead of a long antenna and a matching circuit to tune to a station I have used a large piece of aluminum foil. 

Ultimately the setup was consisting of an aluminium foil connected to one input of a voltage doubler circuit, that acts as a rectifier, and the other input to the voltage double was connected to the central heating system acting as ground. The output of the voltage doubler was connected to the input of the power management. On the output of the power management circuit was a Bluetooth low energy node set to measure the temperature. 

This setup was left over night to charge as the amount of current available was expected to be very small. In the morning I have measured 2.6V. This voltage is just at the border of triggering leading me to believe that there just wasn't sufficient current to make the circuit push over the threshold. 

Although this didn't work out so far increasing the antenna and maybe tweaking the circuit a bit more would allow powering a system from a very simple power source. Stay Tuned