Solar energy is a form of renewable energy, namely energy that cannot be depleted. Other forms of energy like carbon based sources of energy cannot be renewed in a reasonable span after being used (forests take time to grow and oil is created in geological timescales). Joe is trying to deal with the phenomenon of resource depletion. The way he goes about it is making a renewable source of energy more efficient and usable.
It can't because the leaves are barriers.
Chlorophyll, which gives plants their green color, enables plants to turn sunlight, CO2, water, and a few minerals into new plant tissue through a process called photosynthesis<span>.</span>
The answer is cells
because cells are living as well
