Closed photobioreactors (PBRs) facilitate the cultivation of specific strains of algae and allow optimal growth conditions to be maintained.  To date, however, the high capital and operating costs of photobioreactors have prohibited their use for "low-valued" products such as biofuels. Since it's founding in 2006, Solix Biofuels has maintained a sustained effort to develop low-cost, high-productivity photobioreactors.  Three generations of PBRs have been developed, each with successively higher productivity, lower capital cost, lower operating cost, and lower energy utilization. Key design details and a performance summary of generation is presented.  Extensive process modeling and economic projections have been performed. Increasing efforts are now being devoted to reducing the costs of downstream processing: harvesting, dewatering, oil extraction, and co-product processing.  The driving biological factors, design rationale, modeling results, and projected product costs will be discussed.  Solix has now begun construction of a large-scale production facility in southwest Colorado, on the Southern Ute Indian Reservation; relevant technology details of this expansion facility will be presented.