(co2 + algae + tec) = $$, page-25

I've wondered about that too. The sunlight is harvested and brought inside somehow. I don't know what the method is, but as a hypothetical, if it was optical fibres on top of the container feeding it inside, stacking them two high would mean only half as much light. 10 high only 10% as much light, etc.

Maybe it's so intensive that only a small area is used to house algae, and wherever there is a CO2 source there's a building with a roof which will always be larger than the area needed for sunlight harvesting.

It does sound strange, but presumably they have that side of things figured out.