These facilities produce dedicated photon shells as well as store them for later use by the Klingon Empire. Once in operation, these structures provide the necessary armaments to the Koloth-class photon artillery and the Yo'Cha-class photon turret. The structures production allows the colony to defend itself adequately.
These buildings are very vulnerable to enemy attacks, but are even more dangerous because antimatter is required to construct the photon shells. This makes it a target for enemy forces and should the structure be compromised then the entire building may very well explode. (TOS video game: New Worlds)