I have an experiment to transfer solar energy to mechanical energy.
First of all is a cone inspired by an axis.
On the cone are two tiny cups of water.
The whole system is put close to the glass in the room to get sunlight and avoid affection of wind
Then, there will be interaction between sunlight and water molecules, which makes the cone rotate
It is better to implement this idea in tropical countries, where there is plenty of sunlight and temperature is so high, which can heat the water cups
See my clip for more detail
https://www.youtube.com/watch?v=Jsw0rjCYT-s