Algae can be grown in a photobioreactor (PBR). A PBR is a bioreactor which incorporates some type of light source. Virtually any translucent container could be called a PBR; however the term is more commonly used to define a closed system, as opposed to an open tank or pond.

It allows more species to be grown, it allows the species that are being grown to stay dominant, and it extends the growing season, only slightly if unheated and if heated it can produce year round. Because PBR systems are closed, all essential nutrients must be introduced into the system to allow algae to grow and be cultivated. A PBR can be operated in "batch mode", but it is also possible to introduce a continuous stream of sterilized water containing nutrients, air, and carbon dioxide.

Algal culture systems can be illuminated by artificial light, Solar light or by both. Naturally illuminated Algal Culture systems with large illumination surface areas include flat-plate, horizontal/serpentine tubular airlift, and inclined tubular photobioreactors .Generally, laboratory-scale photobioreactors are artificially illuminated (either internally or externally) using fluorescent lamps or other light distributors.

Working of a photobioreactor:

Flow description:

1. From the feeding vessel, the flow progresses to the diaphragm pump which moderates the flow of the algae into the actual tube. Built into the pump is the CO₂ inlet valve.

2. The photo-bioreactor itself is used to promote biological growth by controlling environmental parameters including light. The tubes are acrylic and are designed to have light and dark intervals to enhance the growth rate.

3. The photobioreactor has a built-in cleaning system that will be internally clean the tubes without stopping the production.

4. After the algae have completed the flow through the photobioreactor, it passes back to the feeding vessel. As it progresses through the hoses, the oxygen sensors determine how much oxygen has built up in the plant and it is released in the feeding vessel itself. It is also at this stage that the optical Cell Density sensor determines the harvesting rate.

5. When the algae are ready for harvesting, the algae passes through the connected filtering system. This filter collects the algae that are ready for processing, where the remaining algae passes back to the feeding vessel.

6. And the flow continues.

Advantages of using a photobioreactor:

• High Biomass Productivity and cell density
• Less contamination, water use, & CO₂ losses
• Better light utilization & mixing
• Controlled culture conditions

Disadvantages of using a photobioreactor:

• High capital cost associated with construction costs, circulation pumps, and nutrient-loading systems
• Absence of evaporative cooling, which can lead to very high temperatures
• Accumulation of high concentration of photosynthetically generated O₂ leading to photooxidative damage
• Biofouling of interior surfaces and difficulty of cleaning them
• Cell damage by shear stress
• Deterioration of materials

Requirements to develop a high-performance Photobioreactor for algal cultivation:

1. In order to attain high productivity, the volume of the non-illuminated parts of the reactor should be minimized.
2. In order to ensure a high efficiency of light use by the culture, the design must provide for the uniform illumination of the culture surface and the fast mass transfer of CO₂ and O₂.
3. To prevent rapid fouling of light-transmitting surfaces of reactors, photobioreactors must be frequently shut down for their mechanical cleaning and sterilization
4. High rates of mass transfer must be attained by means that neither damage cultured cells nor suppress their growth.
5. For the industrial-scale production of biomass, the energy consumption required for mass transfer and the arrangement of the light-receiving surface of the algal suspension must be reduced to its minimum possible.