Hydrogen Metabolism H 2 S 2H + S H 2 O H + OH H 2 2 H + 2e - In photosynthesis (simplified): H 2 0 H + OH + 2e - 2H + CO 2 CH 2 O OH + OH H 2 O + O 2O + 2e - O 2
Life on Earth Timeline for development of the major life forms. From a course site by Robert Huskey, U. Virginiacourse site
Hydrogenase Biological cleavage of H 2 is a common metabolic process in prokaryotes and lower eukaryotes and is catalyzed by two major classes of enzymes the [NiFe]- and the [Fe]- hydrogenases. Three distinct [NiFe]-hydrogenases of Ralstonia eutropha (formerly Alcaligenes eutrophus) are in the center of this project, the regulatory (RH), the NAD-linked (SH) and the membrane-bound (MBH) hydrogenase
Fossilized Blue Green Algae These filaments are believed to be the fossilized imprints of blue- green algae, one of the earliest life forms. They occur in the Bitter Springs Formation in Australia and are about 850 million years old.
Green Algae at Work Making H 2 Algal cell suspension / cells Thylakoid membrane
In Vitro Photo-Production of H 2 Yellow arrow marks insertion of hydrogenase promoter. Right side exp. optimized for continuous H 2 production.
Production of H 2 From Algae http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/iic2_lee.pdf
H 2 Energy Calculations Assumptions were made that 10 micro mole of H 2 can be produced per hour (roughly 50% of peak maximum but extended for an hour) per mg of chlorophyll. Additionally, a density of 10% of the top 1 cm (or 100% of top mm) of the system would be populated by chlorophyll, for a density of 1 mg chlorophyll per square cm of collector. This leads to 10,000 cm multiplied by 10 mg chlorophyll per centimeter for a total of 100,000 mg chlorophyll. Multiplying 100,000 mg chlorophyll by 10 micromole H 2 generated per hour per mg chlorophyll yield 1 mole of hydrogen gas per square meter per hour. Combusting one mole of H 2 with one half mole of oxygen (H 2 + ½ O 2 H 2 O) yields 286 KJoules or 68 Kcal. Using any of the following conversions yields KWatt hours or watts from this reaction: 1 calorie = 4.184 Joules 1 calorie = 0.0011622 KwHr 1 Joule = 0.0002778 Watt hours 1 K Joule = 0.2778 watts 286 KJoules X 0.2778 Watts / KJoules = 79 Watts 68,355 calories X 0.0011622 KwHr per calories = 79 KwHr On first pass, it appears that 1 square meter of hydrogen producing algae (modified for continuous hydrogen production) yields about 79 watts, or enough to run a 75 watt light bulb at full power.
ORNL Project Road Map Year 1- Design and construction of DNA sequence coding for polypeptide proton channel Year 2 - Genetic transfer of hydrogenase promoter-linked polypeptide proton-channel DNA into algal strain DS521 Year 3 - Characterization and optimization of the polypeptide proton-channel gene expression Year 4 - Demonstration of efficient and robust production of H 2 in designer alga (ready for next phase - scale-up and commercialization)
Genetic / Biochemical Engineered H 2 Bacterium Sequence coding for polypeptide proton channel – create gene for proton pump Genetic transfer of hydrogenase promoter- linked polypeptide proton-channel DNA into algal genome – express pump with H 2 Characterization and optimization of the polypeptide proton-channel gene expression
Proposed Engineered H 2 Bacterium http://gcep.stanford.edu/pdfs/tr_hydrogen_prod_utilization.pdf
Polypeptide Proton Channel Protons that build up from cleavage of H 2 O into H atoms repress hydrogenase reaction Need to pump hydrogen atoms away from the photosynthetic reaction core, and into storage Hydrogen storage in a carbon nanotube can be the first stage in a nano-structure fuel cell –Platinum doped carbon nanotubes might be an integrated device: storage, fuel cell, and battery
Membrane Bound Protein Pumps Proton and ion pumps consume a lot of cellular energy Nano-channels could be useful
Nanotubes / Nanohorns The electrical properties of nanotubes / nanohorns can change, depending on their molecular structure. The "armchair" type has the characteristics of a metal; the "zigzag" type has properties that change depending on the tube diameter—a third have the characteristics of a metal and the rest those of a semiconductor; the "spiral" type has the characteristics of a semiconductor.
Hydrogen Fuel Cell Diagrams Schematic representation of a composite electrode for low temperature fuel cells Schematic representation of the membrane electrode assembly http://www1.physik.tu-muenchen.de/lehrstuehle/E19/research/pefc.html
Electrochemical Probes with Nanometer Dimensions
Summary Hydrogen metabolism is ancient, and highly conserved in hydrogenase / photosynthesis With genetic / biochemical engineering, algae can make H 2 in significant amounts Capturing and wicking of H 2 into a carbon nanotube fuel cell / battery is very feasible A 1 sq. meter collector could power a 500 watt household with ~ 10X technology gain
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