Above is a rough sketch of what our final reactor is going to look like. We will be using materials like solar panels, polycarbonate tubing, air pumps, and stainless steel in order to form a foundation for our design. The inside of the reactor will be a storage type area for materials as well as a place to keep our air pumps and wiring supplies. BACK of the envelope energy/water calculations for reactor For our Polycarbonate Tubing (ID 2.75 inches, OD 3 inches, L 4 feet):
Total Volume (one tube) = (pi)(radius^2)(height) --> (pi)(1.375 inch)^2*(48 inches) = 285 inches^3 of water volume per tube or 4.67L/tube when filled completely. For two tubes: maximum 9.34 L needed For four tubes: maximum 18.68 L needed For five tubes: maximum 23.35 L needed Water would need to be recycled or resupplied each complete algal growth cycle (about 10 to 14 days). For our Air Pumps (Max Power 5.5 W/pump, 15 L/air/minute for four outlets combined) Total Energy Demand w/Two Pumps on Max Power*: 5.5W/pump * 2 pumps = 11 W If 11 W is running 24 hours a day, then we would need 864000 J/day or 0.24 kWh/day. Using average Berkeley commercial electricity rates (14 cents/kWh), the total cost of our energy demand would be 0.0336 cents/day or $12.26/year if we are hooked up to the Berkeley electricity grid. Total Air Supplied: 15 L/min/pump * 2 pumps = 30 L/min / 8 outlets = 3.75 L air/min/outlet at max power*. *We will not be operating the pumps at max power during our experiments. These calculations are just to show the maximum energy demands for our reactor using two air pumps. Solar Panels: Using the above calculations, if we want to power the air pumps using solar energy completely, we need a solar panel output of greater than 11 W, probably around 15 W just to be safe. We will either have to use a battery system to supply power to the pumps at night or just use the outlet out in the courtyard. **These are not experimental numbers, just rough back of the envelope calculations from measurements made from the supplies already purchased. Updated data will be posted once prototype is tested.
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This past fall, our project group formed and started formulating ideas on what our reactor would look like. Before we could actually get started on building our reactor, however, we needed to familiarize ourselves with algal growth and under what conditions algae grew best. So we set up several experiments in the courtyard of Wurster Hall with varying conditions in different bottles to test how algae growth responded. Our experimental setup in the Wurster Courtyard. Figure 1 shows the growth in the bottles after seven days outside, while Figure 2 shows the growth in the bottles after 10 days of growth. Significant growth was shown after about two weeks in some bottles. Platform 1: Plastic bottle that started out with a high algae concentration. Most significant growth was shown in this bottle with much biomass forming on the sides/top of the bottle. Platform 2: Glass bottles were used for this platform. Each bottle started out with one scoop of algae, but the bottle on the left was given a small pinch of sugar and yeast to produce carbon dioxide. As the second image shows, much more growth was shown in that bottle. Platform 3: A case where too much sugar and yeast was added to a bottle. This bottle grew minimal algae and started to form an orange layer on the top with a foul smell. Platforms 4, 5, 6: More variables test here including fertilizer (far left with red ring on top) and no reflector surface (middle images). Some bottles were capped or left uncapped to see what atmospheric exposure would do for algal growth. The far right images had a reflector wall set up to maximize solar rays hitting the bottles. All images on the top row were taken after seven days and all on the bottom row after ten days.
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SUSTAINABLE ALGAE PHOTOBIOREACTORThe Sustainable Algae Photobioreactor Project is one of the various projects developed through the UC Berkeley division of Engineers for a Sustainable World (ESW). A special thanks to The Green Initiative Fund (TGIF) here at UC Berkeley for providing the grant to make this project possible.
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