I have created a species that is basically a sort of land coral covered in a thick carapace made of rock.
They live on an Earth-like planet (Class M as they say in Star Trek) and behave like coral does on Earth, except for not living underwater. They feed on tiny particulate of matter in suspension in the air, mostly pollens from plants (don't come there if you're allergic) and some sort of flying plankton.
Their carapace isn't one thick sheet of rock, but made of many small sections that fit together. From the outside, it would look like a very rugged rock. On the inside, the coral lives around a core of crystal which grows as the coral grows. It sends tendrils into the ground to get minerals, much like the roots of a tree.
They're mostly active at night, opening the carapace to send some sort of tendrils out to catch the food in suspension in the air; there's much more food at night because the local flowers send their pollens out at night en masse, and spend the day hidden under their shell, keeping the biological parts protected from the UVs coming from the local star and soaking up it's energy. The flowers grow year round thanks to a quasi absence of axial tilt.
My question is how could it transmit solar energy through it's shell to feed the coral and store it in the crystals, and what kind of crystals would be most efficient to store the energy?
I'm looking for biological processes here, or ways to adapt technological means into biological if it's believable. I was thinking of storing the energy in chemical form inside the crystals, to be released when needed by some chemical process.
I'd like a science-based answer, though not hard-science and some handwavium is allowed since this will be used in a sci-fi setting. Thus not everything has to be exactly as it is here on our Earth.