Nope, just very interested in the potential. My personal familiarity with algae is trying to kill the stuff in a swimming pool, and while that sounds silly, there are some very interesting trivia surrounding it.
In my city, there are a lot of phosphates in the recycled water, which while harmless to humans is fertilizer to algae(*), meaning that the use of chlorine and algaecide are much greater than typical. But add to that my close proximity to a large, algae-ridden, man made lake, which generates enormous, if invisible clouds of spores, and most swimming pools in the area are green or brown.
To *stop* algae from growing is a full time job. It is the flip side to actually want it to grow.
(*) This was why the use of phosphates in laundry detergent was banned in the 1960s, as its runoff was causing algae blooms in fresh water that would de-oxygenate it and kill fish. Its use continued long after in dishwasher detergent (because it was exempted, dishwashers not being as popular then). Phosphates are also used in PVC pipe sealant, which adds a lot to both fresh water and sewage.
I will add to phosphates, that when you bubble CO2 and NOx gases through warm algae water, you get such tremendous algae growth that you can almost watch it.
I’ve tried to imagine what I would think to be the “ideal” algae farm for the southwestern US, and this is pretty much how I’ve imagined it.
First imagine a plowed farm field, with rows connected together accordion style, making one continuous path. In each row is a continuous shallow tub, just a few inches deep. At the bottom of each tub are “bubble strips” of plastic tube with little holes to bubble CO2 and NOx gases into the water. (The US Olympic swimming team uses such bubble strips to bubble oxygen gas into their pools to kill algae, as oxygen is far less irritating to the eyes and skin than is chlorine.)
The water flowing in a continuous path through the accordion tub is low quality water, whatever is available, likely recycled effluent. The water flows in one end, then out the other to be reused after being filtered.
Along the side of the top of the tub are runners and a conveyor belt trough. A small harvester goes the length of the tub and back, scooping up the algae and dumping it on the conveyor belt for processing.
One bit of high technology used would be that the tubs would be covered with “self-cleaning clear glass”. This is a new product made because of nanotechnology. A coating is sprayed on the glass that prevents grime or even water from sticking to it. The purpose of this low maintenance barrier is to keep foreign algae out of the tanks, yet to let in sunlight.
Otherwise, depending on the outdoor temperature, there might be a holding tank for the water that either slightly heats or cools it, when the temperature outside is either too cool or two warm.
Other than that, electronic monitoring of water temperature and salts, as well as trace amounts of growth enhancing fertilizer, and this should give maximum output with minimum cost.
Here's my imaginary version. In the the raised center a field is a sealed algae production unit. This will need to have a fairly significant surface area to produce a significant quantity of algae, but the production there will only be a small fraction of the total.
Algae from that plant will be continuously harvested live, mixed with water, and piped to the end of some spiraling troughs. Similar to what you suggested, the troughs would have CO2 bubbled through them.
There would be a slow but continuous flow of water through the troughs. The diluted algae would grow in the sun and thus become more concentrated when the reached the outer edges of the troughs were they could be harvested. The water flow would have to be fast enough to keep the algae flowing, and the troughs would probably need periodic cleaning even so, but if the algae were only in the trough for a day, I wouldn't think foreign algae would be too much of a problem; they would just get swept up and processed along with all the other trough algae.