Introduction
The sun is an enormous source of cheap and environmentally friendly energy, which is unfortunately only used to a limited extend. Unicellular algae (phototrophic micro-organisms) can use solar energy for the production of biomass with higher photosynthetic efficiencies, compared to plants.

Aim
This project focused on designing a reactor and process for the efficient conversion of sunlight into biomass.

Research
The project was split-up in 2 parts.
1. Reactor design and preparations for outdoor experiments.
2. Process design.
The first part deals with the “hardware”, the Green Solar Collector, which can be seen in the photograph. Lenses focus sunlight into a plastic sheet, placed in an algal culture. Due to a surface treatment, light will leave the sheet in the culture. A reactor has been built, consisting of one sheet and one lens. This reactor will be used for testing and fine-tuning, for example: the tracking of the sun and positioning of the lenses, the shape and surface treatment of the plastic sheets, amongst others. Modeling and trail and error play an important role in this part of the research.

The second part deals with the “software” of the system, circumstances that need to be applied to the algae in order to achieve maximum efficiency for the conversion of sunlight into biomass. The amount of sunlight available for algae varies due to solar movement across the sky and possible interferences like clouds. Effect of varying light intensity of the conversion of light into biomass needs to be determined in order to design an efficient process for cultivation of algae on sunlight.

The efficiency of the conversion will be determined in a flat-panel photo-bioreactor, in which a light-path and light intensity resembling the Green Solar Collector will be applied. Decreasing the light intensity will simulate night and day interferences.

Acknowledgements
This research was initially funded by Senter-Novem and a Biopartner first stage grand. It was a part of the Dutch BioHydrogen research project (BWPII) and is currently a part of the European Solar-H program.