Integrated photovoltaic-photobioreator systems to improve captured solar energy exploitation

Tetraselmis suecica is a microalga widely used in aquaculture and is a good candidate for bioenergy production, although, especially for this latter application, the biomass production cost is still high. One of the most important costs is that for purchase electrical energy necessary to run electromechanical components of the cultivation plant. In our work, Tetraselmis suecica F&M-M33 was grown outdoors in raceway- ponds and in Green Wall Panel (GWP ® ) photobioreactors where the direct illuminated surface was shaded (from 20 to 80% of PAR) with different mimicking or real photovoltaic materials, that reduce/modify the light reaching the cultures, with the aim of evaluating the production of electrical energy and/or the reduction of cooling needs. In each trial, conducted in fed-batch and/or in semicontinuous, one culture, without shading, acted as control. Interestingly, in most of the cases, productivity of shaded cultures was similar to that of the control and in some cases even higher (up to 16%). Gross biomass composition was slightly affected. According to our measurements, the use of shading devices allows to reduce energy need for cooling up to 55% in GWP ® -III photobioreactors. The calculated electrical energy produced by the hypothetical photovoltaic devices was enough to fully cover the energy needs for microalgae cultivation and harvesting.