Development and Testing of a Cylindrical LED Lighting Unit for a Conveyer-Type Salad Production System

A cylindrical plant growth chamber (PGC) referred to as PHYTOCYCLE-SD was designed and developed as a conveyor-type cultivation system for continuous production of salad crops. The volume of the plant growth chamber is 0.19 m³, and the illuminated crop area is 0.86 m². The PGC is comprised of a convex cylindrical planting surface with a spiral cylindrical light unit (LU) above the planting surface. The LU consists of 15 light-emitting diode (LED) panels distributed on the spiral cylindrical surface with adjustable operating currents between 10 to 35 mA. The average photosynthetic photon flux (PPF, 400–700 nm wavelengths) level at the crop surface (3 cm below the light bar) is 350 μmol m⁻² s⁻¹ and the LU power consumption is approximately 440 W. Leaf area as a function of the radius of the cylindrical growth chamber has been determined experimentally. Light intensity and distribution inside cylindrical growth chamber has been measured and modeled. These models can be used to estimate the productivity of various species crops in a spiral growth chamber compared to a flat surface.