GPU turn off

For a soloar-powered Nvidia Jetson Nano board, what are the techniques to consume less power? For example, is there any way to turn off the GPU module?

Don‘t know if it will work, but maybe you can try setting the GPU frequency to zero?
Here is some more info how to set CPU and GPU clocks: https://docs.nvidia.com/jetson/archives/l4t-archived/l4t-321/index.html#page/Tegra%20Linux%20Driver%20Package%20Development%20Guide%2Fpower_management_nano.html%23wwpID0E0RC0HA