Feasibility analysis of photobiological hydrogen production

Photobiological production of hydrogen from water (biophotolysis) requires efficient biological converters, microalgae, and low cost photobioreactors. Microalgal strains must be developed that exhibit high hydrogen production rates and photosynthetic efficiencies in dense cultures at full solar intensities. The photobioreactor must expose the Hz producing cultures to sunlight, while allowing recovery of the gas. A preliminary analysis is presented of a two stage process in which microalgae are cultivated in large open ponds to produce a high carbohydrate biomass that then produces hydrogen in tubular photobioreactors. Photobioreactors constructed of inexpensive, commercially available, glass tubes are proposed for such applications. Photobiological hydrogen production requires long-term research and development. However it could be of lower cost than systems based on electrolysis of water using photovoltaic electricity-the current system of choice for solar hydrogen production. (C) 1997 International Association for Hydrogen Energy.