In a closed ecological life support system, comprising a photobioreactor, the improvement being said photobioreactor comprises a hollow, cylindrical irradiation chamber, wherein said chamber comprises a top sealed to a cylindrical side wall;
- a bottom sealed to said cylindrical side wall;
- said top, bottom and cylindrical side wall together enclosing a cylindrical space;
- a first cylindrical light irradiator disposed in said cylindrical space and attached only to said top;
- and a second cylindrical light irradiator disposed in said cylindrical space and attached only to said bottom;
- wherein all cylindrical light irradiators and said cylindrical side wall are coaxial;
- the distance between said cylindrical side wall and cylindrical light irradiator closest to said side wall is within 1 mm to 20 cm, and the distance between each adjacent cylindrical light irradiator is within 1 mm to 20 cm.