Photobioreactor Sunlight Dilution Technology and its benefits

1. Active Spatial Sunlight DilutionTM
Increases Areal Productivity of Microalgae
- A Presentation at ISAP Conference 2014, Sydney
Weixing Tan, PhD
Grande Prairie Regional College,
Canada

2. Key Limitation for Microalgae Industrial
Application
• Low areal productivity (Benemann 2003)
• Directly impacts economic bottom line
• Under 20 g/m2/day for open ponds
• Recently reported from Algenol in (Photobioreactor) PBR:
10,000 gal (ethanol)/acre/yr (equivalent to 32.5 g/m2/day)
(Spall et al. 2011)
• Up to 50-70 g/m2/day as reported in PBRs (Spall et al.
2011; Sudhakar & Premalatha 2012)
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3. Key Limitation for Microalgae Industrial
Application
• Inefficient sunlight utilization by microalgae
• Major contribution to low productivity
• 50-90% of the energy losses (Zemke et al. 2008; Sudhakar &
Premalatha 2012)
• Maximum efficiency ≈ 12% of the total solar input after
reductions of PAR portion (47%), transmission (95%) &
photoconversion (27%)
• Equivalent to approximately 150-200 g/m2/day
• Reported productivities were only 10-30% of this
maximum. 3

4. Analysis of Sunlight Utilization by Microalgae
# Item
Relative
Reduction
Reduction in %
Solar Energy
% of Solar Energy
after Reduction Comments
(1) Maximum 12.0%
(2)
Efficiency of Photon
Utilization due to
Saturation - Bush Equation
35% of the (1)
(50% sunny
days)
-4.2% 7.8%
Saturation PAR =
200 µmol/m
2
/s
(3)
Sub-optimal
Environments, Including
Photoinhibition
70-0% of the (2) -5.5-0% 2.3-7.8%
(4)
Respiration &
Maintenance
40% of the (3) -0.9-3.3% 1.4-4.5%
Equivalent to
~10-50 g/m
2
/day
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5. What are holding us up from the maximum?
• The culprits - photosaturation and suboptimal environments
(difficult to reduce respiration/maintenance)
• Inefficient sunlight utilization is the key limiting factor,
representing 60-100% of the recoverable opportunities – a
conclusion recognized for over 50 years (e.g. Vonshak & Torzillo 2003).
1. Photosaturation: 4.2 % of the solar input or equivalent 50 g/m2/day
2. Photoinhibition (at 30% of the suboptimal environments) : 0-1.7% or 0-20
g/m2/day
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6. Vonshak & Torzillo (2003)
Energy Loss during Photosynthesis
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Photosaturation Quenching Photoinhibition

7. What we can do
Three solutions suggested by Vonshak & Torzillo (2003)
1. ↑ algae density & mixing rate – logistics, energy intensive,
sheering stress, scalability
2. Improve light distribution in the culture – cumbersome,
expensive, scalability
3. Algal strains with small antenna – to be proved yet, trade-off?
We suggest the 4th:
4. Active Spatial Sunlight DilutionTM – simple, inexpensive,
scalable & works (patented PCT/CA2014/050450)
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8. What is Active Spatial Sunlight DilutionTM?
• Orienting 2 opposing surfaces ACTIVELY in parallel to the sunray:
1. Reduces or ‘DILUTES’ sunlight exposure
2. Allows uniform sunlight on both surfaces, diminishing shading
in Parallelin Perpendicular
vs
When
facing the
sun…

9. Spatial Sunlight Dilution in Microalgae/Plant Systems
9

10. Moving the System and Tracking the Sun through a Day
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11. (We are
developing a
simpler,
inexpensive
& automated
system.)
System Diagram for This Study
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12. (PAR
sensor)
Photobioreactor (PBR) System
(Florescence
light for
hybrid 24/7
operation)
(Computer
Control System)
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13. Sunlight Dilution on E-W PBR Surfaces
with Uniform Exposure
East West
When we align the
panel in parallel to
the sun…
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14. Description of the PBR System
• One panel with 24x2=48 round glass tubes (244x2.7 cm), 61 L
• Glasses staggered at 1 cm spacing on both surfaces, facing E-W
• 2 curtains (12 cm spacing) on each side to simulate the scale-up
• Moving at 1⁰ increment in ~10:30-17:30 each day by computer
• PAR sensors on E-W sides and in perpendicular to Sun
• One air bubbler in each tube (~500-1000 µm)
• Culture circulation by air-lifting
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15. Microalgae Culture
• Chlorella vulgaris (UTEX 2714) grown auto-trophically
• 2 cycles of 3 mostly sunny days in September 2012
• Culture conditions:
• 3% CO2 flue gas (mixed with air) from natural gas generator
• Temperature inside solarium: 22-25/22⁰C (day/night)
• Balanced chemical nutrient solution with initial 413 ppm N
at pH 6.5
• Starting algae density of ~1.26 g/L and then measured each
day
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16. Preliminary Results – Sunlight Dilution (1st example)
(Some troughs were
from structural beams)
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17. Preliminary Results – Sunlight Dilution (2nd example)
(Some troughs were
from structural beams)
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18. Preliminary Results – Microalgae Productivity
• Average volumetric productivity =
0.634+0.207 g/L/day
• Equivalent to 106 g/m2/day when
calculated on a scaled industrial
configuration
(Chlorella vulgaris)
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19. Current and Future Research and Development
• Construction of 5-panel system with a
simpler, inexpensive & automated design
(300 L) for further testing of scalability
• Nutrient and water recycling
• Microbe control
• Development and construction of a pilot
scale system beside a emission source
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20. Conclusion
• Overcoming photosaturation and photoinhibition is the
most promising strategy to significantly increase
microalgae productivity.
• The ‘Active Spatial Sunlight DilutionTM’ concept is a simple
and scalable solution.
• It increases areal productivity by:
1. Distributing a diluted and desirable fraction of sunlight to more
compacted PBR surface areas
2. Diminishing mutual shading on opposite PBR surfaces
3. Significantly reducing photosaturation and photoinhibition
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21. Acknowledgements
• Major Sponsors/Partners
• Natural Science and Engineering Research Council
(NSERC), Canada
• ConocoPhillips Canada Ltd., Canada
• EnEco Systems Inc, Canada, Europe, South America
• Woodmere Nursery Ltd., Canada
• Rheaume Engineering Inc., Canada
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22. Acknowledgements
• Research Team
• Weixing Tan, PhD, Principal Investigator (plant
ecophysiology)
• Abigail Adebusuyi, PhD (microbiology and biotechnology)
• Melissa Day, PhD (microbiology, 2011-13)
• Ali Al-Asadi, PhD (astronomy and physics)
• Bruce Rutley, PhD PAg (agricultural production systems)
• Laurie Lin (mechanical engineering)
• Jordan Pickup (computing)
• Aurele Lemay (electrical)
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23. Thanks!
Comments & Questions
Weixing Tan
wtan@gprc.ab.ca
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