Hemispherical Photobioreactor Algae Farming (HEASH Project)





Introduction: Hemispherical Photobioreactor Algae Farming (HEASH Project)

This project is designed to provide steps that can guide you to making your own hemispherical photobioreactor, or algae farm dome for those who like smaller words. The bioreactor is made from two acrylic domes glues together.

Most of the parts needed:

Item - Source

  • 4" of 6" diameter acrylic tube - usplastics.com
  • 30" diameter acrylic dome with bottom lip 1/8" thick - www.cleardome.com
  • 32" diameter acrylic dome with bottom lip 1/8" thick - same as above
  • Pipe Tap - 1 inch x 11.5 NPT
  • 1 inch npt male to 1 inch barbed fitting
  • Barbed x NPT Male
  • Weld-On 4 Acrylic Adhesive
  • 3" x 3" 3/4" thick acrylic square
  • 1/8" thick 3" wide 6 foot length plexiglass (not acrylic)
  • 1 inch valve threaded
  • 1 inch threaded nipple
  • premium aquarium hose (translucent kind not clear, must be soft)
  • 1/2" barbed tee
  • 3' of 1/2" drip line
  • pond pump
  • various hoses and fittings...make sure you live near a home depot and irrigation supply house...
  • dusk to dawn switch
  • algae
  • bleach
  • Alga-Gro Freshwater Medium

Step 1: Glue Together Domes

Glue together the two domes. One dome is 2 inches less diameter so it is set in the larger one. The connecting surfaces are glued together and force is applied to remove any bubbles and thus a chance for leaking. We used 30 and 32 inch domes with a 3 inch flange. Use many clamps to keep pieces together. There should now be a water proof chamber formed between the domes. In the next step we will build the drain for this vessel.

Step 2: Attach Drain

Take the 3" square plexiglass peice and glue it to the middle of the bottom of the dome chamber. This is done so that a hole can be drilled through both domes and the square and have plenty of room for the threading bit. Once glue is dry drill a 1-5/32 hole for the 1 inch x 11.5 NPT pipe tap right in the center between the two dome walls. Use the pipe tap to thread the holes. Once threaded you can attach the nipple and threaded 1 inch valve. This now serves as a dome chamber drain. You can optionally place one of these near the top of the dome for a fill fitting if you wish to have continuous loop algae production.

Step 3: Cut Top Hole and Glue on Ring

Cut a hole in the top of the upper dome that is 6" diameter. Use the inside of the 6 inch diameter 4" acrylic piece as a form. Drill pilot hole then finish cut with a router. Spiral o flute bits work best for routing plastic. Once its been cut glue the 6" tube section onto the opening with acrylic glue. If you need it to be sealed you can build a cap for the top (do not glue cap)

Step 4: Build Bubble Walker and Air Supply

Bubble walker- is a device used for agitation of the water and allows photosynthesis to occur more efficiently for the algae. The walker is made form acrylic plexi glass and metal washers. The main body is one piece of plexiglass beveled with a heat gunned into a U shaped body and drilled through for washer mounting and air. There are multiple washers on the two bolts allowing a balance of weight to lift from bubble flow ratio allowing for a gentling forward propel around the dome. Experimentation is required for optimal results. The device has a air line attached to feed air supply and works with adjustable hose clamps to control air pressure for optimum results.

Air Supply - The air supply is fixed rate piston driven pump and allows for adequate air pressure, as determined by successful forward movement of the walker..

Air Return - If you need to return build a cap for the air inlet and air outlet capture and return to wherever its needed. In our case we vented it back to our earthship to provide fresh air.

Step 5: Water Cooling System

The water cooling system keeps the algae cool during the daytime. Cut a peice of 1/2" drip line in a 2-3 foot section and poke holes all over in it facing towards the top of the dome. Try to make the flow laminar and not spray in the air. Connect the ends with a 1/2" barbed T and connect to a submersible pump. Place the pump in a full kiddie pool or equivalent water volume for cooling.

Glue 3" plexiglass around the outside rim of the flange to create a channel for water to flow back into the pond.

Step 6: Install LED Light Bank

Place led light arrays face up into the bottom of the dome. Place the arrays onto blocks or some other platform to prevent flood water damage. The dome will protect it from rain. Use a dusk to dawn plug for the led array.

Step 7: Bleach, Fertilize, and Innoculate

Bleach everything with dilution. clean throughly with clean water after and fill. Fertilize with Alga-Gro Freshwater Medium, and add algae culture. Adjust the aeration to as little as possible while maintaining forward movement. 

This instructable is part of the HAESH Hackerspace Earthship Project. Check it out. www.haesh.com on the web or on instructibles.



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    I'm curious: why are deep red LEDs not as space or energy efficient, if the point is to maximize the algae's utilization of the light for a certain amount of electricity? And aren't they essentially the same size?

    Separate question: wouldn't it be better to do any drilling and tapping of holes BEFORE gluing the two domes together, to avoid getting chips inside the gap where they'd be difficult to remove?

    4 replies

    Red leds come in different spectrum and have different watt to lumens ratios. Plants absorb cloraphyl a and b cycles disfferently.

    I understand, but lumens are meaningless to a plant. It's a measure of apparent brightness to the human eye (across all its color receptors), which has a very different absorption curve than chlorophyll.
    So even though LEDs are almost always rated for efficiency by their lumens/Watts ratio, that number isn't useful to measure the efficiency of algae growth/Watt. The deep red may appear dimmer to the eye, but it's the most efficient kind for exciting chlorophyll a to produce energy. While the more orange-red LEDs are better at exciting chlorophyll b. So the best spectrum would be to have some of both reds, as well as blue.

    The hole goes through all 3 pieces. Tapping cannot be done to each piece individually. Plus you flush the whole thing with water so any stray scrap will drain out the hole.

    In general theres lots of uses. Food, nutritional supplements, possibly fuel in the future. For us it was simple we needed to sequester co2 and generate 02 for the habitant of our earth ship concept. See our other instructables for more info or www.haesh.com

    Dry it out into chips and eat. Or miz it in smothies.

    surely entertaining read, i have read somewhere else algae will be used to produce energy in the future..

    Some people eat a type of algae and others stick to soylent green

    We hope to use human wastes to grow the aglea, so maybe we could call it soylent algae.

    De-water it, homogenize it(break the cell wall), and use powder in smothies is most common method. Pills work too.

    How fast does the algae grow if you can saturate with CO2 and light. If you fill one dome, how long before you must flush and fill again?

    3 replies

    Each species of algae has a specific range of CO2 it likes. Some thermophile species can live in 100% but not many. Light is tricky. LEDs have interesting effects on algae. Blue makes them more numerous and red makes them fatter. But there are many different spectrum of red led available in 3w. Deep red is more efficient in the plant but a lighter red led is more efficient power/space wise. I am using chlorella right now in batch production and its a week or so. This design was origianally used for haematococcus pluvialis. You can do continuous production if you can filter it in situ and control nutrients via sensors. I have some ideas for future instructables for this...

    It's a very interesting design. Obviously optimized for efficient light distribution. So with the haematococcus pluvialis, were you cycling the light from rapid growth to increased astaxanthin production?

    It would be interesting to know what other species could be used in your domes, beyond the supplements, like for bioremediation.

    As far as biomass goes, I think a system that optimized for water and nutrient efficiency would be required instead. Like layers of ultra thin film.

    You are limited by bubble in thin plates. But yes the thinner it gets the denser it gets. We looked into doing flat plate reactors as well as disposable plastic bag reactors. Well see what we do next. haematococcus was grown by fuji, we are not growing haematococcus anymore because its subject to contamination. We built a few and fixed a few of the old ones. We are also working on other algae tech.

    My apologies if I give too many comments in a row, it's an interesting concept, but how much water does the evaporation cooler setup use? Wouldn't it be using less water if you use a heat exchanger where you connect the dome to a pump and then pump the algae solution to a heat exchanger, burried underground (always 14 degrees) and then send the cooled algae broth back towards the dome?

    1 reply

    The water seems to keep the domes from ageing in the sun. Evaporation is low. Your heat exchanger may foul. Its worth testing.

    creative instructable! I like the concept and ideas put forward here. The walker is also a different take on a rotating stutter. But have you taught about material fatigue? If the walker keeps turning the plastic tubing that connects the walker to the air supply could break off. Maybe you could use a rotational coupling?

    1 reply

    Material on old ones are 10 plus years. Just make sure to use the soft piping that translucent not the clear vinyl stuff.