Why Spirals Wouldn't be Viable

We decided that a spiral was too inefficient regarding the surface area of algae exposed. According to our calculations (seen below), the pipe would need to be around 25 meters long to attain prime surface area (80,000 cm2). An Archimedian spiral would still need a massive radius to achieve the proper surface area. The pipe in question was to have a diameter of 10 cm, with an unknown thickness. The sheer length of pipe needed was enough to deter us from pursuing this kind of shape.

Instead of a spiral, we decided to create sheets to attain the optimal surface area of 80,000 cm2. Many thin sheets of algae will be placed consecutively next to each other. We inserted a picture below for convenience.

Calculations:

Pipe with radius r = 5 cm;

Surface area of cylinder = 2πrh+2πr2

Height = 2560.32 cm, or about 25 m

Archimedian spiral would need to be about 25 m long, which is too big.

CAD drawings

CAD Drawings - 

illustrations by Fenton Billings

Week 1

This week, we formed a group and discussed a few topics, and eventually settled on the idea of algae air purification through photosynthesis. We discussed various subtopics of this idea which included green rooftops, photosynthetic paint, and mass purification with tubes of algae. We researched tubes of algae that were used to purify the air around highways, which were all several miles long. However, we wanted to scale the pipe system down to fit in a house or apartment and allow it to be easily maintained by the user. By installing modules in several homes in a neighborhood, it is possible to greatly reduce the amount of carbon dioxide in the air. With limited discussion time, this was about all we could accomplish.

Week 4

This week, we realized that we wanted to get rid of the pump in the system. The pump wouldn't have been strong enough to move algae, so the pipe would have been constantly clogged. It would have required a lot of work to keep the pump primed during cleaning. A model without a pump would decrease the number of parts in the system, therefore reducing the cost of production and maintenance. We came up with the idea of using a mechanical motor in the center of the module that would rotate a spiral pipe system. The algae would continuously fall through the spiral, thus allowing the algae to circulate without the need of a pump. The moving part is much easier to access for maintenance, and it isn't subjected to the maintenance procedures that the pump would need to undergo.
The spiral pipe system would also drastically increase surface area while keeping the same wall area.

Week 5

This week, our group redesigned the whole structure of the air purification system. Instead of making the system a winding tube or a spiral, the system would be made of thin algae-filled sheets which were to be square with 50-centimeter sides, and with a 2-centimeter thickness. The design would contain fifteen or thirty plates, which would be separated by half inch gaps. We completely changed the design because if we were to use a 2-inch diameter tube to hold the membrane and algae, it would need to be 84 feet long to account for the surface area needed to purify the air for just one person. A winding or spiral tube would take up too much space in a house, and it would not be practical. We came up with the idea of sheets to maximize surface area. The structure is partially based on how bees kept by beekeepers build honeycombs on sheets; the sheets would be in a trough to hold them in place. We also began working on the CAD model of our new structure in Autodesk Fusion 360.