Deep Water culture
This was my first greenhouse construction project I was assigned at Rough Brothers. This combination of A-Frame head house and Poly Arch production range took up a four acre footprint. It employed a vast hydroponic field sectioned into 13 lagoons. The hydroponic method employed at this location is referred to as Deep Water Culture (DWC). The “Deep” in the title may seem counter intuitive since these ponds are merely 12″ in depth; however, these ponds are about 300x deeper than that of another hydroponic technique. Below is a simplified diagram of a DWC application. The plants are suspended from the polystyrene rafts and their roots are allowed to relax in the nutrient solution. Air is dissolved into this fluid to maintain the health of the roots and to supplement the oxygen needs of the plant. If all environmental levels are maintained, then the plant will survive. If all environmental levels are optimized, then the plants will thrive. The parameters to be controlled include: ph & nutrient levels, PAR light, air temperature, water temperature, irrigation timing, humidity, CO2, dissolved oxygen, etc.
Above is a simplified more residential application of what we are trying to accomplish. The regulation of the fluid underneath the rafts can be difficult given that the Ph fluctuates with chemical reactions, plants take in nutrients and oxygen, and the fluid temperature can change seasonally. Additionally, the volume of water to maintain in this project is around 750,000 gallons.
To replace the enormous amount of work that has to be done in this process we designed the plow system below. These plows, with the Rough Bros. text cut out of them, are pneumatic and actuate in parallel to move the field of floating polystyrene towards the harvesting workers. This end is where new transplants would be introduced to their final journey lagoon. Each raft will be pushed by the previously loaded raft which is being forced by the retractable plow that is piloted with a foot valve.
If you are interested in taking a gander around the inside of this project, Green City Growers has made a promotional video that exhibits the operational side of this facility. This video is below and focuses more on the vision for the company.