Flat panel photobioreactors feature important advantages for mass production of photoauto­trophic microorganisms. The simple flat plate photobioreactor consists of vertically translu­cent flat plates, which are illuminated on both sides and stirred by aeration (Figure 2.3). This simple building methodology for glass flat plate reactors provides the opportunity to easily construct reactors with any desired light path. Light is evenly emitted from a flat transparent surface screen or from lamps above the culture. The plate surface is usually made of glass or optical light film, and the circulation is achieved by the same means of rising air bubbles, as

with the tubular systems. However, flat plate systems may also experience problems with relatively high space requirements, high light energy requirements, difficulties in cleaning, and possible low efficiency in terms of mass production per unit of space (Slegers et al.,

2011) . The productivity of flat-plate photobioreactors is highly dependent on the space requirements between the panels and the areal productivity constraint for outdoor applica­tion. On the other hand, if the flat plate systems are to be operated indoors, then some crucial factors would be involved, including distance of light sources from panels, temperature effects, illumination of one or both panel sides, light path, and so on. Scale-up of the flat plate system is potentially difficult due to the increase of hydrostatic pressure with the increase of volume. In general, the structure of flat plate systems cannot tolerate very high pressure. Moreover, the hydrodynamic stress on microalgae cells may affect the microalgae growth. In addition, the biomass productivity in parallel flat panels is strongly influenced by shading and light penetration between the panels (Posada et al., 2012). To further reduce the equip­ment cost, a novel design of a vertical flat panel photobioreactor, consisting of a transparent bag (i. e., plastic) located on a rigid frame, has been proposed and could greatly enhance the economic feasibility (Tredici and Rodolf, 2004).