US Patent 11661572 Photobioreactors, gas concentrators, and periodic surfaces

A system for growing algae includes a photobioreactor comprising a tubular structure having inner and outer surfaces, an annular space defined between the inner and outer surfaces, an inlet to allow an algae slurry to enter the annular space, and a mechanism configured to produce radially-directed contractions and expansions in the tubular structure. At least one of the inner and outer surfaces is transparent to at least some wavelengths of light useful for growing algae within the algae slurry.