Problem Overview
As the nation has developed its urban communities, many Americans have found it difficult to grow and purchase fresh produce. As shown in Video 1, there are 23.5 million Americans, including 6.5 million children living in food deserts [1]. With limited availability of fresh produce, Americans' nutritional requirements are not fully being satisfied. In an effort to increase the nutritional well-being of Americans (particularly those in urban areas), a vertical planter will be developed for the purpose of growing produce. The planter will be inexpensive in order to enable all people to have access to fresh produce. The final product will be not only affordable but also simple for the consumer to assemble.
Video 1. Eliminating Food Deserts in America [1]
Design Constraints
There are three major design constrains. The first constraint is space limit. In urban area, there is not much room for farming, so the design should use the limited space to grow the most food possible. The second constraint is materials constraint. The materials for the design should be environmental-friendly while having good performance. The third constraint is the cost. The product should be very affordable and efficient, so it can be helpful to reduce food deserts and be widely adopted.
Pre-Existing Solutions
Gardens and farming have always been hard to accomplish in urban areas. There is generally a lack of green space to grow anything because of all the streets and buildings. The lack of plants in these urban areas causes a lot of problems. There is generally a lack of oxygen in the air and an abundance of carbon dioxide and when you talk about farming there is a lack of fresh produce. People have looked into these problems and come up with a lot of different ideas. Vertical growing has been one of the most popular new revolutionary styles. Many companies have come up with ways for people who live in urban areas to grow their own vertical farms.
A company called Urban Gardens has come up with their own design to allow urban livers to grow plants and vegetables. As shown in Figure 1, their design uses a flap like pocket for the plants to sit in and grow. Figure 2 shows their model on a balcony. This utilizes the small space that urban families have and allows them to grow their own vegetables, fruits, or flowers [2].
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| Figure 1. Urban Gardens's plants growing pockets [2] |
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| Figure 2. Pocketed plants on the balcony [2] |
This same company has designed hanging plants as well, as shown in Figure 3, which gives even more ways to grow in an urban area [3].
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| Figure 3. Hanging plants [3] |
This company’s design has few flaws because it is relatively cheap and the materials used are even environmentally friendly. They use a product called polypropylene plastic that is environmentally friendly in a few ways. The plastic doesn’t release chemicals into the environment and it also uses recycled plastics. The one downside to this product would have to be how hard the plants are to water. The owner must water each plant individually and depending on where the plants are located this can be an issue for many people. If the garden is hanging off of a balcony people don’t want to have to lean over their balcony to water them and if they are high up the owner must climb in order to water them.
The Gardener’s Supply Company has designed a product that makes it easier for people to grow plants upside down, as shown in Figure 4. This product can be placed anywhere that has a roof and simply needs to be screwed into the ceiling. Many different plants actually grow better upside down and this once again gives urban livers an easy way to grow their own. The soil is simply put in the green bag and a hole is cut into the problem that allows the plant to grow through the bottom but it doesn’t allow soil to fall through. The bag also is a waterproof so the water that you put in will not come out [4].
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| Figure 4. Upside down model from Gardner's Supply Company [4] |
The problem with this product is that the material used in the bag is not necessarily environmentally friendly. Also many people who have bought the product and then posted reviews about it have complaints about the quality of the plants that grow in the bag and they say that the plants don’t grow right. It turns out barely over half of the people who bought this product would recommend it to someone else. For a product that is $25, this might not be the best product to buy when trying to grow in an urban area.
Most criticisms on small-scale vertical farming is efficiency [5-6], and large-scale vertical farming always requires significant amount of energy use [7]. In Ankri's thesis, he suggests that combining agriculture with architecture and builds horizontal and vertical farming on the same building [8]. This design is very efficient and does not require much power usage, but it is not very feasible in cities such as Philadelphia because it needs new designs of the buildings.
Project Goal
The goal of this project is to create a compact, inexpensive, sustainable, easy-to-use farming module that allows urban dwellers the opportunity to maximize their available space for the growth of fresh fruits and vegetables in their homes. It not only reduces food deserts, but also increase the air quality of the urban area. The product will be unique because it will use the space more efficiently and provide a more variety of fresh fruits and vegetables, and the materials used are more sustainable.
Project Deliverables
The deliverable of the project includes mechanical design, materials selection, plants selection and construction. Mechanical design involves structure design of the module and mechanical testing. A hydroponic system will be installed and used as water supply for the planter. Mechanical properties, price, and recyclability of the materials and environment effect such as water and UV on the materials will be taken into consideration during materials selection. The process of materials selection will involve brainstorming on the possible materials and selecting the best ones among the possibilities. The goal of the plants selection process is to have a variety of vegetables and fruits growing on the module, and the plants selected should go well together. The plants will be growing separately from the planter and will be installed into the planter's hydroponic system after construction. A model of the farming planter module will be presented at the end of the term.
Project Schedule
A detailed schedule is shown in Table 1. The deadlines of the milestones are:
- Week 3 - Initial Research Completed, Project Proposal Finalized, Plant Selection Finalized
- Week 4 - Mechanical Design Completed
- Week 5 - Plants Preparation Completed
- Week 6 - Materials Selection Completed
- Week 7 - Basic Construction Completed
- Week 8 - Design Revision if necessary
- Week 9 - Construction Completed, Final Analysis and Design Changes, Working Prototype Completed.
- Week 10 - Final Report and Final Presentation
Table 1. Project Schedule
Technical Activities
Planting Style Selection
Different farming approaches were brainstormed, including trellis, flaps, bags, PVC towers, tiers, and upside down growing. Growing factors and potential problems to each of these styles were evaluated, such as sustainability, cost, space use, aesthetics, and so on. A chart was made to list the if the method meets each criteria, as shown in Table 2. According to the statistics, upside-down growing is the best growing methods, so upside-down growing will be the growing style for the planter.
Table 2. Statistics of the Evaluations on Different Growing Styles
Two vertical posts are the support of the whole planter and two parallel horizontal beams will connect the columns. These two horizontal posts have plants growing upside-down. In order to use the space more sufficiently, the two vertical posts will also be used for planting. Plants can grow on pockets installed on the vertical posts. The watering system for the planter is a hydroponic system in the module to reduce the planter's weight and to idealize growing conditions for the plants while making the system cleaner and easier to maintain.
Materials Selection
The main building material or materials must be relatively inexpensive and lightweight, while being strong enough to support the weight of the plants and the running water, as well as survive outdoors conditions. Besides, the budget must be fine-tuned for consumer cost estimates.
Bamboo is a sustainable nature composite material that has relatively good mechanical properties. Using bamboo also adds an aesthetic value to the product that using PVC is lack of, but there are many disadvantages. One problem with bamboo is that bamboo will rot when it is exposed to water for long time. This is exceptionally inconvenient for the design since the hydroponic system design has water running through it constantly. Bamboo is also quite flexible, so when the planter is exposed to strong winds as well as intense weather, a structure made of bamboo poles will not be ideal. Also, bamboo is not grown commercially on the East Coast, so the best place to get it is from California or from overseas, but the cost for getting bamboo poles will be rather high (over $30 per pole plus extra money for removing nodes and high shipping fees). The biggest problem about using bamboo is that big hole cuts are needed on the side bamboo poles to connect the horizontal poles. The cuts need to be about the diameter of the horizontal poles, so these cuts will remove much fiber support which can increase local stress of the joint regions and cause fracture. On the other hand, PVC pipes are much sturdier, so they can withstand the intense weather. PVC can also withstand constant exposure of water and UV. PVC pipes are much cheaper and easier to obtain. Connecting PVC tubes is much easier with the help of T-joint connectors. Using T-joints instead of cutting holes on the vertical pipes not only prevent strength loss of the vertical support, but also increase the tensile strength at the connection region by increasing stress concentration factor, which is the ratio of maximum local stress to overall background stress. Based on the relationships shown in formula (1) and (2), increasing the fillet radius r or the major shaft diameter D can increase SCF. D, r, and d are labeled in Figure 4 [15]. T-joint connectors increase both the fillet radius and the major shaft diameter, so it can increase SCF. With higher SCF, the connection joint can tolerate a higher local stress σ * SCF.
SCF ∝ r/d (1)
SCF ∝ D/d (2)
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| Figure 5. Dimensions used for SCF calculation [15] |
Hydroponic System
The design will be having the tubing run up one side of the planter and veer off to the middle and top rungs. The two buckets will serve as the reservoirs on each side, and the side with tubing going up has the pump. The water from that bucket will be pumped up and flow on the roots through the horizontal pipes, and then drip down in the opposite pipe to water its lettuce and will be collected in the other bucket. The water on the pump side will also go up to the top, hit the endcap, then drip down from the wall to water its lettuce. The two buckets will be connected with a tube so the water can cycle back to the pump. Funnels may be used in the pipes to guide the water to flow along the wall. A schematic of the design is shown in Figure 6. The green parts are the PVC pipes, the blue parts are the joints, the purple triangles are the funnels, the cyan lines are the tubing, and the red arrows are directions of the water flow.
The estimate water flow rate for the planter is about 2 gallons of water per minute, so the pump has to support at least 120 gallons of water per hour to the height of 6’. After comparing functioning and prices, a pump which can support a maximum of 221 gallons of water per hour at the height of 6’ was selected. This pump has a flow control, so its rate can be adjusted to about 120 gallons per hour.
Construction
The materials used for construction are two 6’ long 4” diameter PVC pipes, two 4’ long 4” diameter PVC pipes, four connectors (T-joints) and two endcaps for the pipes, two 5-gallon buckets, three funnels, two 1” diameter PVC pipes, four plate caster wheels, 90-degree elbow joints, ¾" diameter tubing, and the plywood boards.
Each 6' PVC pipe was cut into a 2’1” piece and a 3’4” piece. Since each bucket is about 15” deep, the cut divides the remaining pipe into two parts which one part is 15” longer than the other, so when installed, the pipes will appear to be evenly spread above and below the T-joint outside of the bucket. Two 3” pieces were cut with the extra pieces to be used as the top end of the vertical planter.
The horizontal pipes will not be cut in length because the maximized distance between the plants is necessary for the plants to grow well. Three holes were cut on each of the two horizontal planter pipes. The holes were evenly separated along the pipe, and the distance between holes was about 11”. A 1” hole-saw was used to cut the holes, then the holes were ground to fit the small pipe. Six 1¼” long pieces were cut from the small pipe, and the pieces were installed in the holes in the horizontal pipes.
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| Figure 7. Dimensions for the plywood box |
Projected Budget
- MATERIALS
- 5-Gallon Buckets [17]
- $8.23/2 buckets, 2 bucket
- Purchased from Home Depot
- SDR 35 PVC Pipes
- Donation from Joe Bauer & Sons, Inc.
- PP 400 GPH Auquaponics Pump [18]
- $25.99/pump, 1 pump
- Purchased from Amazon.com
- 4" Drain Pipe T-Joints
- $3.13/each, 4 T-joints
- Purchased from Home Depot
- 4" Drain Pipe Caps
- $1.72/each, 2 caps
- Purchased from Home Depot
- 2" Plate Caster Wheels
- $5.97/2 wheels, 4 wheels
- Purchased from Home Depot
- 1" by 2" PVC Pipes
- $1.82/each, 1 pipe
- Purchased from Home Depot
- PVC Cement 16oz.
- $7.63/jar, 1 jar
- Purchased from Home Depot
- Tubing
- $14.35/each, 1 tubing
- Purchased from Home Depot
- Funnels
- $1.00/2 funnels, 2 funnels
- Purchased from Dollar Store
- Plywood board
- Donation from Koste Family
- PLANTS
- Tomato Seedlings
- $5.97/3 seedlings, 3 seedlings
- Purchased from AGWAY
- Cucumbers Seedlings
- $4.47/3 seedlings, 3 seedlings
- Purchased from AGWAY
- Romain Lettuce Seedlings
- $14.80/24 seedlings, 24 seedlings
- Purchased from AGWAY
Current Cost - $112.16
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