Pending final approval and system feedback. Additional work and explanation can be found from parent page of Product Design Studio 5, http://pdi-studio5.wp.rpi.edu/2013-2/edu-ponics/
Edu-Ponics: An alternative growing solution
Our project consists of five important elements, each inherent to the design of a hydroponic system; a water/nutrient-solution delivery system, a plant/container storage array, the actual nutrients themselves, the growing medium, and of course the plants. What is a hydroponic system, you say? The basis of hydroponics — from English “hydro,” or “water,” and Greek “ponein,” “to labor or toil” — is to form a system of growing plants — usually herbs, or small vegetables, though most systems can be expanded past the small-scale — without conventional soil or growing medium. Most hydroponic systems involve the above components — the plants themselves, a container within which to hold the plants, a growing medium (usually with common growing mediums such as perlite, vermiculite, clay pebbles, or coconut husks), and a nutrient solution / pumping system to deliver the nutrients to the plants. Conventional soil acts as merely a buffer for the plants, protecting them from pH changes, water saturation, and other environmental changes — by removing the soil it is possible to deliver nutrients directly to the plants without having to enrich the soil first (e.g. with fertilizer), where the new growing medium merely contains the roots of the plants without absorbing the nutrients themselves. This is why most hydroponic systems, such as ours, are self-sustaining and automated; without the soil-buffer, every environment variable must be more carefully controlled to allow for the plants to still grow within their desired ranges.
How it Works
The actual design of our system is very simple; most hydroponic systems are built in either one of two fashions — vertically, or in a flat flood-bed. The vertical systems allow for a single stream of water to flow along the plant-line, from container to container, rather than trying to feed each plant individually at a time — thus conserving pump-power and flow. The advantage to the flood-bed is the ability to feed all the desired plants at once, by flooding the entire plant-bed at once, then allowing the system to drain fully before filling again; however, this does require more open space to implement, and is more prone to issues of mold and requires more power (and a stronger pump to implement), which is why we chose to go with out current design of a vertical-drip system: if we start at the bottom where the nutrient solution is pumped from the reservoir up to the top of the structure (through the sides of the structure to save space and reduce clutter), where it flows through the first plant-container into the second via ropes — a drip-system, to avoid the solution spraying out of the bottom and onto the tops of the plants, as with this method the solution can be assured to flow directly from the soil of one pot to another. At the bottom of the vertical stack we have a funnel that leads back to our reservoir, to allow for a fully closed-loop system. It should be noted here that our project uses a kelp-based nutrient solution that is non-toxic to humans, so if skin contact occurs no health-issues should arise. Combined with the sensor-array included in our system (more on that below) to monitor and control the flow cycle and conditions of the system, we are secure that our system will deliver efficient produce with minimal input from the student users, thus easing the burden of growing from the Community Gardens.
Why we did what we did
The sensor on our system collects data on the environment of the plants — temperature/humidity, the amount of light received, as well as soil dampness — to allow not only for the students at the Community Gardens to spot-test the beds, but also to know if the plants experienced any radical changes during low-attention hours — such as over a weekend or overnight — that might inhibit further growth (e.g. not enough sunlight, or perhaps too much growing solution, or freezing temperatures). The hope is that this freedom to collect data will enable the students to learn more about what it takes to grow plants, and to figure out what ideal conditions are needed to add new plants; a hands-on experiment that will engage the users and encourage future projects as well.
Our system is still pending final user-feedback, though every step of the design process we have facilitates user-interaction and feedback on the design process and desired results of this project. As of the last user presentation, it has been decided that our system will be implemented mainly for the summer trimester-projects that the students of the Community Gardens hold; the system will most likely be drained and inactive during the winter months, when the system would otherwise freeze. This is not to say that all usage will be halted; it is possible that some degree of use will occur over the winter months, possibly just to hold plants which require a reduced water-cycle.
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