I would like to second the motion that closed bioreactors are far too expensive to be practical. Square miles of plastic is expensive and gets fouled after a few years, needing replacement. Perhaps someone can figure out how to make a bacteria that will prevent algal build up on the walls. Perhaps the better configuration would be closed bioreactors to scale up density, followed by injection into large open ponds. That solution has been used in Hawaii to reach 18g biomass/m2, which would mean 2000 gal/acre/year. California would need about 5m acres of ponds to run the transportation system.
I will have lipid yield data for a good variety of Amphora and a second wild strain from a waste water treatment plant next month. We are growing them in the lab and are plannig lipid extraction soon. Let me know if you are interested in seeing the data. I'm not very optimistic however.