New Page 1

Solar Lighting for Growth of Algae in a Photobioreactor

Oak Ridge National Laboratory and Ohio University

This ORNL/Ohio University project is demonstrating the feasibility of using remote solar lighting systems to enhance sunlight utilization and biomass production in photobioreactors.

Large solar collectors on the roof track the sun, collect sunlight, and distribute it through large optical fibers to the bioreactor's growth chamber. The fibers function as distributed light sources to illuminate cyanobacteria (algae).
	Each growth chamber consists of a series of illumination sheets containing the optical fibers and moist cloth-like membranes on which the algae grow. By stacking the membranes vertically and better distributing the light, more algae can be produced via photosynthesis in a smaller area.

Ohio University photobioreactors use sunlight to sequestor carbon from coal-fired power plans as they produce biomass. The Ohio University reactor will ultimately remove the carbon generated by the production of about 125 MW of electricity in a coal fired plan.

This system is expected to sequester carbon at a cost of $5-8 per ton surpassing the U.S. Department of Energy's goal of $10 per ton. It will also reduce the space required by a factor of 10 or more, when compared to raceway cultivators.

Light delivery and distribution is the principle obstacle to using commercial-scale photobioreactors for algae production. In horizontal cultivator systems, light penetrates the suspension only to 5 cm, leaving most of the algae in darkness. The top layer of algae requires only about 1/10th the intensity of full sunlight to maximize growth, so the remaining sunlight is wasted.

The biomass has a variety of potential uses: hydrogen production, feedstocks, agriculture, pharmaceuticals.