High Pressure Sodium Lamp Lighting Analysis and Design for the BIO-Plex Plant Growth Chambers
Shaun C. Gartenberg

The purpose of this project was to propose and evaluate a design for the high-pressure sodium lighting to be used in the BIO-Plex plant growth chamber at Johnson Space Center, Houston, TX. A standard 400-watt HPS lamp was used. The water-jacketed lamp initially suggested for this design could not be incorporated into this project due to manufacturing problems. Photopia, a 3D luminaire analysis and design program created by Lighting Technologies, Inc. was utilized to analyze the designs. A target mean illuminance value of 1500 mmol/m2s was desired while maintaining as much uniformity in the output as possible across a plane situated beneath the light box. Lamp placement and reflector design was considered.

After 29 simulations, an acceptable design was determined for a single light box. Several important issues were brought up over the course of the project. First, a total of 5 lamps per light box satisfied the lighting requirement, instead of the initial 8 that were used. Second, a decrease in 400 mmol/m2s was observed across a 10-cm distance beneath the light box. Third, exclusion of the outer edges of the illuminance plane gave more realistic interpretations of the majority of the data. Finally, it became apparent that at least some loss in uniformity should be accepted due to the difficulty in reflecting light to certain areas of the lamp bank. Suggestions for future analysis are also considered, expanding upon this project's designs.

Figure 4. Light box simulation with four lamps at the corners and one in the center.