Hollow glass microspheres for temperature and irradiance control in photobioreactors

• Photobioreactors made of a HGM polymer are cheaper to run.
• The broth temperature can be reduced 7 °C using 0.6 vol.% HGM in the reactor wall.
• HGM composites have mechanical properties suitable for bioreactor manufacture.
• Growth rate is improved by up to 33% using 0.6 vol.% HGM comp. in the reactor wall.

The addition of hollow glass microspheres (HGM) to polymers to change thermal insulation and mechanical properties is widely used. In this study HGM were tested as a new construction material for photobioreactors to control irradiance and broth temperature in microalgae cultivation. The heat isolation properties of HGMs of three different densities were tested in a polymer matrix. The transmittance (5–50%) and the thermal conductivity (182.05–190.73 W/mK) of the HGM composite material were analyzed. The results were tested in a model to predict the broth temperature and the growth rate as a function of temperature and irradiance. The addition of 1.3 and 0.6 vol.% of HGM lead to an increase in the growth rate of up to 37% and a reduction in the broth temperature up to 9 °C. The mechanical resistance of the composites tested is similar to the polymer matrix.