Ecological energy exploitation

Today I propose a new experiment. It is a futuristic vision of how we can live in harmony with what nature has to offer us, understanding by this that we can exploit the energy of nature in such a way that we do not destroy it. Such examples of energy sources are for example solar energy, wind energy, kinetic energy of water (hydro power plant) and nuclear energy. These come to my mind for now, there are probably others. Some of these energy sources are safe and clean, but for example the nuclear one can become unstable and has a contaminating effect.
What if we could for example extract the energy of a tree while it is still alive?