The fact that Chlorella grows so slowly isn’t a problem for me personally, I don’t have time to attend to this stuff every day so it kind of works out nicely. BUT, if I want to come up with projects that are student friendly, they have to fit into a semester and also into their lives. I had hoped that somewhere out there, there might be a paper showing that you can increase its growth rate in light by adding glucose or some other carbon source. But no, as shown in this paper (PDF), glucose or galactose CAN support growth of Chlorella in the dark, but its slower than, and does not increase, the light saturated growth rate.
I still need to look up what is known about growth on plates versus liquid cultures.
H. Samejima and J. Meyers. (1958) On the heterotrophic growth of Chlorella pyrenoidosa J. Gen. Microbiol 18 108-117. (PDF)