Oxybox

The goal of this project is to create a small self-contained growing chamber for grasses and microgreens, with a fan for circulating air over the crops to provide them with CO2 and the room with oxygen. It will also serve as a small experiment on the effectiveness of essential oils on preventing mold/fungus growth. This article suggests thyme oil and geranium oil (applied as vapor) are most effective at preventing mold and fungal growth on wood. Also cited for effectiveness at killing/preventing mold are clove oil, coriander oil, basil oil, oregano oil, and neem oil, combined with castile soap to serve as a wetting agent. The selected crops are grasses, buckwheat lettuce, and sunflower greens, as suggested by http://www.secrets-of-longevity-in-humans.com/oxygen-producing-plants.html, however other sources confirming sprouts' ability to produce oxygen have not yet been found. As an aside, oxygen producing houseplants were mentioned in a TED talk by Kamal Meattle (used as a source in the previous article), listed here: http://greenspaces.in/blog/ted09/. They are the Areca Palm (Chrysalidocarpus lutescens) and Mother-in-law’s Tongue (Sansevieria trifasciata), the former of which would provide enough oxygen with 4 shoulder high plants per person, and the latter with 6-8 waist high plants per person.

Plan

The microgreens will be grown in a 10x20" grow tray, with 8 5x5" trays, one for each crop. The tray will sit in a Sterilite 60 Qt. Industrial Tote. The lighting will be supplied by 4 Cree XM-L T6 LEDs at 1000 lumens each, driven in a 2 series configuration with 2 drivers (one for each series pair) at 3A fed from a 12V power supply. The LEDs will be passively cooled using an aluminum CPU heatsink. A fan and shroud may be added if the passive heat dissipation is not enough. The interior of the container will be lined with reflective mylar (from a space blanket) to maximize light exposure. A 120mm brushless fan will circulate air through the container, running in a U shape through the first 4 crops and then the second 4 crops, using a plexiglass divider to ensure air flows over all crops. A CO2 sensor will be used at the output to measure the effectiveness of the system at reducing CO2, using the known ~400ppm value as a given for the area, or by baselining with the sensor in the environment before putting it into the container. Likewise, the biomass of the plants will be measured at the end of a harvest to estimate the amount of carbon taken from the environment.

LED Subsystem

Drivers: http://www.ebay.com/itm/272086482559

Specs:

• Synchronous Buck Converter
• 4.5-23V Input
• 0.9-20V Output
• 3A Max Current
• 30W Max Power
• 1V Min Dropout
• 100mV Ripple
• 94% Efficiency
• 56x23x17mm

LEDs: http://www.ebay.com/itm/400641738330

Specs:

• 6000-6500K Color Temperature
• 3.35Vf at 3A
• 3A Max Current
• 1000LM at 3A
• 15mm Diameter

Power Supply Requirements:

• 3.35V x 2 = 6.7V at 3A => Pout = 20.1W
• 12V at 1.97A => Pin = 23.6W at 85% efficiency
• 3.6W Pheat
• 12V at 5A (60W) minimum power supply required