Why is a photobioreactor made from high end glass even better today than it was five years ago

[Global] Photobioreactors with higher productivity are combined with more affordable pricing. In the last five years photobioreactors (PBRs) made of glass have seen significant improvements due to a variety of innovations. For instance, through improved algae production processes combined with lower costs.

Reduced wall thickness leads to higher output

Various PBR field tests have shown that the thickness of glass walls has influence on the PBR‘s productivity. In recent years, improved glass manufacturing processes have made it possible to further reduce the wall thickness.

For a long time, common wall thicknesses lay between 2.5 – 3.3 mm for a 5.5 meter long tube to ensure mechanical stability of the glass tube. Depending on the supplier‘s ability to produce tubes with tight wall thickness tolerances, glass tubes used in PBRs can have thinner wall thickness. It seams logical that for typically used tube dimensions tubes with equal outer diameters but smaller wall thickness are more productive – because the larger inner diameter would offer more overall volume and a larger illuminated culture cross section.

SCHOTT Tubing and a partner in Israel tested the output of a 16 kilometer long tubular PBR with a reduced wall thickness of 1.8 mm for one year and compared these results with a PBR tubing with 2.5 mm wall thickness. The result: tubing with the same outer diameter and the reduced wall thickness of 1.8 mm led to 10% more output (Heamatococcus Pluvialis was cultivated during the test).

A certain share of the productivity increase can be attributed to the larger cross sectional area of the algae culture within the tubing. This larger area leads to increased light absorption. Simultaneously the temperature fluctuates less in such tubing which also promotes productivity.

Of course, thin walled tubing raises the question if it is more susceptible to breakage. The test in Israel showed: Not a single case of breakage was recorded during the transport, installation, start-up and full operation of the reactor. The prerequisite for this was glass with tight wall thickness tolerances and high quality end forming.

Longer tubing segments lead to less biofouling

The longer the tubing that are installed in a PBR, the less tubes are required to reach the desired total volume. This also means that less tubes have to be connected to one another, reducing the probability of leakage. Furthermore, it reduces the risk of biofilm forming because every additional connection with the corresponding couplings offer minute gaps, i.e. spaces that are more susceptible to fouling.

Due to improvements in the glass tubing manufacturing and handling processes, it is now possible to produce high quality glass tubing in very long lengths. Using such tubing can help operators to reduce the number of required couplings and therefore reduce the risk of biofouling.

One aspect that should be considered: longer tube length makes transport and handling a bit more demanding, as they require more space. Choosing the right length for glass tubes is always a choice between practicality and productivity. 5.5 meter long tubing, as a standard length, has emerged as a has emerged as a good choice because packaged tubes fit into a standard 20 foot container and can be handled with a forklift truck.

Download the pdf file here: Why is a photobioreactor made from high end glass even better today than it was five years ago to learn more about:

  1. High quality tube couplings for safe operation
  2. Fully automated production of U-bends and manifolds ensures higher precision
  3. Vertically aligned PBRs for higher efficiency and productivity

For more information, please visit: Why is a photobioreactor made from high end glass even better today than it was five years ago


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