Chlorophyll is an alternative energy source for the human body. And actually, all animals have this ability.
Because it goes into the mitochondria as a metabolite. It enables the mitochondria to capture sunlight energy, which photo-energizes the Krebs cycle in such a way that it produces significantly more ATP, which is sort of the energy currency of the body, without increasing oxidative stress.
This is a new study that came out last year, which completely undermines our classical understanding of our bodies as able to live only by eating other things. Basically, we can, if we have adequate chlorophyll in our diet - wheatgrass being one of the best sources - directly capture the sunlight. Not only does it increase the production and efficiency of ATP in our body, but it also increases longevity, at least in the earthworm model, which is what they use it for.
We will see animal studies and probably human studies soon. Basically, this reclassifies us from heterotrophs, which depend on other things, to photo-heterotrophs, which means we can actually take sunlight directly into our bodies.
Keep in mind, it doesn't just mean the wavelengths that are, like you know, obviously the sunlight we see. Red, for example, is a wavelength that goes deep into our tissue as well. It can even penetrate the skull and enter our brain, energizing it.