Design of a Commercial Scale Algae Pond Cover System

Photo of Mario Bueno, Gary Richardson, Brent Waggener Students: Mario Bueno, Gary Richardson, Brent Waggener

Sponsor: UT Center for Electromechanics

Date: Spring 2010

Requirements:
The algae pond cover should withstand category 1 hurricane winds, recapture 75% of the current evaporation losses (1.3 in/week), cost less that $1/ft², and should be easy to remove with localized access to the pond every 15 feet. The pond cover design should be adaptable for both small and large scale operations.

Problem:
Currently, The University of Texas at Austin Center for Electromechanics (CEM) is developing an electromechanical method for extracting oil from algae to be used for biofuel. In order to fully develop this technology, CEM requires a steady supply of algae to be used for testing purposes. The most practical solution is to grow the algae onsite in closed loop ponds where the algae growth can be studied and regulated. However, due to susceptibility to contamination from bacteria and pond water evaporation, the algae pond needs a proper cover to protect it.

Solution:
The cover design uses individual frames spaced five feet apart. Each frame has an arc supported by a vertical post on either end using Schedule 40 PVC for the frame material. PVC with a nominal diameter of ½” comprises the arcs, while 1½” PVC comprises the vertical posts supporting the smaller diameter arc. The posts are joined to the arc with 45° elbows, with a 1½” to ½” bushing to mate the PVC pipes of different diameters. The PVC frame is secured to the ground using steel stakes welded into a “t”-shape to provide increased stability for the frame. Pebbles fill the gap between the PVC inner diameter and the stake outer diameter to reduce unwanted movement. A transparent polyethylene cover is then draped over the frame and secured using VELCRO applied on the inside of the cover and on the horizontal portion of the stakes. Every 15 feet the cover is cut and secured with VELCRO to the PVC arcs, allowing localized access to the pond without needing to remove the entire cover of what could be a very long pond. On the inside of the cover, one inch flaps are created on the tarp by folding it over and heat sealing the fold to itself. The purpose of the flaps is to collect the condensation that accumulates on the inside of the cover and redirect the water back into the pond. This design is adaptable for ponds with widths of up to 10.6 ft and unlimited lengths.

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