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Improvement of Photosynthetic Efficiency Through Reduction of Chlorophyll Antenna Size

Description: We have previously presented a graphical illustration of a strategy to improve photosynthetic conversion efficiencies by a reduction of the antenna size in photosynthetic reaction centers. During the current reporting period, we have made progress in demonstrating the conceptual correctness of this idea. Light-saturation studies for CO, in air were performed with an antenna-deficient mutant of Chlamydomonas (DS521) and the wild type (DES15). The light-saturated rate for CO(2), assimilation in mutant DS521 was about two times higher (187 Mu-mol.h(-1).mg chl(-1)) than that of the wild type, DES15 (95 Mu-mol.h(-1).mg chl(-1). Significantly, a partial linearization of the light-saturation curve was also observed. The light intensities that give half-saturation of the photosynthetic rate were 276 and 152 Mu-E.m(-2).s(-1) in DS521 and DES15, respectively. These results confirmed that DS521 has a smaller chlorophyll antenna size and demonstrated that the reduction of antenna size can indeed improve the overall efficiency of photon utilization. Corresponding experiments were also performed with CO(2), in helium. Under this anaerobic condition, no photoinhibition was observed, even at elevated light intensities. Photoinhibition occurs under aerobic conditions. The antenna-deficient mutant DS521 can also provide significant resistance to photoinhibition, in addition to the improvement in the overall efficiency in CO(2), fixation.
Date: May 3, 1999
Creator: Blankinship, S.L.; Greenbaum, E.; Lee, J.W. & Mets, L.
Partner: UNT Libraries Government Documents Department

Photosynthetic Hydrogen and Oxygen Production by Green Algae

Description: Photosynthesis research at Oak Ridge National Laboratory is focused on hydrogen and oxygen production by green algae in the context of its potential as a renewable fuel and chemical feed stock. Beginning with its discovery by Gaffron and Rubin in 1942, motivated by curiosity-driven laboratory research, studies were initiated in the early 1970s that focused on photosynthetic hydrogen production from an applied perspective. From a scientific and technical point of view, current research is focused on optimizing net thermodynamic conversion efficiencies represented by the Gibbs Free Energy of molecular hydrogen. The key research questions of maximizing hydrogen and oxygen production by light-activated water splitting in green algae are: (1) removing the oxygen sensitivity of algal hydrogenases; (2) linearizing the light saturation curves of hotosynthesis throughout the entire range of terrestrial solar irradiance-including the role of bicarbonate and carbon dioxide in optimization of photosynthetic electron transpor;t and (3) constructing real-world bioreactors, including the generation of hydrogen and oxygen against workable back pressures of the photoproduced gases.
Date: August 22, 1999
Creator: Greenbaum, E. & Lee, J.W.
Partner: UNT Libraries Government Documents Department

Hydrogen transport and storage in engineered glass microspheres

Description: New, high strength glass microspheres filled with pressurized hydrogen exhibit densities which make them attractive for bulk hydrogen storage and transport. The membrane tensile stress at failure for our engineered glass microspheres is about 150,000 psi, permitting a threefold increase in pressure limit and storage capacity above commercial microspheres, which have been studied a decade ago and have been shown to fail at membrane stresses of 50,000 psi. Our analysis relating glass microspheres for hydrogen transport with infrastructure and economics, indicate that pressurized microspheres can be economically competitive with other forms of bulk rail and truck transport such as pressurized tube transports and liquid hydrogen trailers.
Date: April 18, 1995
Creator: Rambach, G.D.
Partner: UNT Libraries Government Documents Department

Final Report - Novel Approach to Non-Precious Metal Catalysts

Description: This project was directed at reducing the dependence of PEM fuel cells catalysts on precious metals. The primary motivation was to reduce the cost of the fuel cell stack as well as the overall system cost without loss of performance or durability. Platinum is currently the catalyst of choice for both the anode & the cathode. However, the oxygen reduction reaction (ORR) which takes place on the cathode is an inherently slower reaction compared to the hydrogen oxidation reaction (HOR) which takes place on the anode. Therefore, more platinum is needed on the cathode than on the anode to achieve suitable fuel cell performance. As a result, developing a replacement for platinum on the cathode side will have a larger impact on overall stack cost. Thus, the specific objectives of the project, as stated in the solicitation, were to produce non-precious metal (NPM) cathode catalysts which reduce dependence on precious metals (especially Pt), perform as well as conventional precious metal catalysts currently in use in MEAs, cost 50% less compared to a target of 0.2 g Pt/peak kW, & demonstrate durability of greater than 2000 hours with less than 10% power degradation. During the term of the project, DOE refined its targets for NPM catalyst activity to encompass volumetric current density. The DOE Multi-Year RD&D Plan (2005) volumetric current density targets for 2010 & 2015 are greater than 130 A/cm3 & 300 A/cm3 at 800 mV (IR-free) respectively. The initial approach to achieve these targets was to use vacuum deposition techniques to deposit transition metal, carbon and nitrogen moieties onto 3M’s nanostructured thin film (NSTF) catalyst support. While this approach yielded compounds with similar physicochemical characteristics as catalysts reported by others as active for ORR, the activity of these vacuum deposited catalysts was not satisfactory. In order to enhance catalytic ...
Date: November 17, 2007
Creator: Atanasoski, Radoslav
Partner: UNT Libraries Government Documents Department

New MEA Materials for Improved DMFC Performance, Durability and Cost

Description: Abstract Project Title: New MEA Materials for Improved DMFC Performance, Durability and Cost The University of North Florida (UNF)--with project partners the University of Florida, Northeastern University, and Johnson Matthey--has recently completed the Department of Energy (DOE) project entitled “New MEA Materials for Improved DMFC Performance, Durability and Cost”. The primary objective of the project was to advance portable fuel cell MEA technology towards the commercial targets as laid out in the DOE R&D roadmap by developing a passive water recovery MEA (membrane electrode assembly). Developers at the University of North Florida identified water management components as an insurmountable barrier to achieving the required system size and weight necessary to achieve the energy density requirements of small portable power applications. UNF developed an innovative “passive water recovery” MEA for direct methanol fuel cells (DMFC) which provides a path to system simplification and optimization. The passive water recovery MEA incorporates a hydrophobic, porous, barrier layer within the cathode electrode, so that capillary pressure forces the water produced at the cathode through holes in the membrane and back to the anode. By directly transferring the water from the cathode to the anode, the balance of plant is very much simplified and the need for heavy, bulky water recovery components is eliminated. At the heart of the passive water recovery MEA is the UNF DM-1 membrane that utilizes a hydrocarbon structure to optimize performance in a DMFC system. The membrane has inherent performance advantages, such as a low methanol crossover (high overall efficiency), while maintaining a high proton conductivity (good electrochemical efficiency) when compared to perfluorinated sulfonic acid membranes such as Nafion. Critically, the membrane provides an extremely low electro-osmotic drag coefficient of approximately one water molecule per proton (versus the 2-3 for Nafion) that minimizes flooding issues at the cathode, which often ...
Date: September 16, 2013
Creator: Fletcher, James H.; Campbell, Joseph L.; Cox, Philip & Harrington, William J.
Partner: UNT Libraries Government Documents Department

Recovery Act: Advanced Direct Methanol Fuel Cell for Mobile Computing

Description: ABSTRACT Project Title: Recovery Act: Advanced Direct Methanol Fuel Cell for Mobile Computing PROJECT OBJECTIVE The objective of the project was to advance portable fuel cell system technology towards the commercial targets of power density, energy density and lifetime. These targets were laid out in the DOE’s R&D roadmap to develop an advanced direct methanol fuel cell power supply that meets commercial entry requirements. Such a power supply will enable mobile computers to operate non-stop, unplugged from the wall power outlet, by using the high energy density of methanol fuel contained in a replaceable fuel cartridge. Specifically this project focused on balance-of-plant component integration and miniaturization, as well as extensive component, subassembly and integrated system durability and validation testing. This design has resulted in a pre-production power supply design and a prototype that meet the rigorous demands of consumer electronic applications. PROJECT TASKS The proposed work plan was designed to meet the project objectives, which corresponded directly with the objectives outlined in the Funding Opportunity Announcement: To engineer the fuel cell balance-of-plant and packaging to meet the needs of consumer electronic systems, specifically at power levels required for mobile computing. UNF used existing balance-of-plant component technologies developed under its current US Army CERDEC project, as well as a previous DOE project completed by PolyFuel, to further refine them to both miniaturize and integrate their functionality to increase the system power density and energy density. Benefits of UNF’s novel passive water recycling MEA (membrane electrode assembly) and the simplified system architecture it enabled formed the foundation of the design approach. The package design was hardened to address orientation independence, shock, vibration, and environmental requirements. Fuel cartridge and fuel subsystems were improved to ensure effective fuel containment. PROJECT OVERVIEW The University of North Florida (UNF), with project partner the University of Florida, ...
Date: September 3, 2013
Creator: Fletcher, James H.; Cox, Philip; Harrington, William J & Campbell, Joseph L
Partner: UNT Libraries Government Documents Department

Thermal management technology for hydrogen storage: Fullerene option

Description: Fullerenes were picked as first option for H storage because of potentially high volumetric and gravimetric densities. Results indicate that about 6 wt% H (corresponding to C{sub 60}H{sub 48}) can be added to and taken out of fullerenes. A model with thermally activated hydrogenation/dehydrogenation was developed. Activation energies were estimated to be 100 and 160 kJ/mole (1.0 and 1.6 eV/H{sub 2}) for hydrogenation and dehydrogenation, respectively; difference is interpreted as heat release during hydrogenation. The activation energies and hydrogenation heat may be modifiable by catalysts. Preliminary H storage simulations for a conceptually simple device were performed (a 1-m long hollow metal cylinder with inner dia 0.02 m filled with fullerene powders). Results indicate that the thermal diffusivity of the fullerenes controls the hydrogenation and dehydrogenation rates. Rates can be significantly modified by changing the thermal diffusivity, eg, by incorporating a metal mesh. The simulation suggest that thermal management is essential for efficient H storage devices using fullerenes. More controlled experiments, model development, and physical property determinations are needed; catalyst use also needs to be pursued. Future ORNL/MER cooperative work is planned.
Date: May 28, 1996
Creator: Wang, J.C.; Chen, F.C. & Murphy, R.W.
Partner: UNT Libraries Government Documents Department

Final Report for the H2Fuel Bus

Description: The H2Fuel Bus is the world's first hydrogen-fueled electric hybrid transit bus. It was a project developed through a public/private partnership involving several leading technological and industrial organizations, with primary funding by the Department of Energy (DOE). The primary goals of the project are to gain valuable information on the technical readiness and economic viability of hydrogen fueled buses and to enhance the public awareness and acceptance of emerging hydrogen technologies.
Date: November 25, 1998
Creator: Jacobs, W.D.
Partner: UNT Libraries Government Documents Department

Hydrogen from renewable resources monthly progress report

Description: During February, we achieved two significant results in our hydrogen storage activates. Reversible hydrogen uptake and release was measured at room temperature, near ambient pressure on the (IrClH{sub 2}(H{sub 2})Pr{sup i}{sub 3}) complex. Dr. Jensen also observed that certain polyhydzide complexes catalyze the low temperature, reversible dehydrogenation of cycloalkanes to aromatic hydrocarbons at temperatures as low as 130{degrees}C. This discovery may represent a breakthrough in chemical storage of hydrogen as all other cycloalkane dehydrogenation systems require temperatures in excess of 300{degrees}C.
Date: February 1, 1995
Creator: Rocheleau, R.E.
Partner: UNT Libraries Government Documents Department

Wet processing of palladium for use in the tritium facility at Westinghouse, Savannah River, SC. Preparation of palladium using the Mound Muddy Water process

Description: Palladium used at Savannah River for tritium storage is currently obtained from a commercial source. In order to better understand the processes involved in preparing this material, Savannah River is supporting investigations into the chemical reactions used to synthesize this material and into the conditions necessary to produce palladium powder that meets their specifications. This better understanding may help to guarantee a continued reliable source for this material in the future. As part of this evaluation, a work-for-others contract between Westinghouse Savannah River Company and the Ames Laboratory Metallurgy and Ceramics Program was initiated. During FY98, the process for producing palladium powder developed in 1986 by Dan Grove of Mound Applied Technologies (USDOE) was studied to understand the processing conditions that lead to changes in morphology in the final product. This report details the results of this study of the Mound Muddy Water process, along with the results of a round-robin analysis of well-characterized palladium samples that was performed by Savannah River and Ames Laboratory. The Mound Muddy Water process is comprised of three basic wet chemical processes, palladium dissolution, neutralization, and precipitation, with a number of filtration steps to remove unwanted impurity precipitates.
Date: November 10, 1998
Creator: Baldwin, D.P. & Zamzow, D.S.
Partner: UNT Libraries Government Documents Department

Novel selective surface flow (SSF{trademark}) membranes for the recovery of hydrogen from waste gas streams. Phase 2: Technology development, final report

Description: The objective of Phase II of the Selective Surface Flow Membrane program was Technology Development. Issues addressed were: (i) to develop detailed performance characteristics on a 1 ft{sup 2} multi- tube module and develop design data, (ii) to build a field test rig and complete field evaluation with the 1 ft{sup 2} area membrane system, (iii) to implement membrane preparation technology and demonstrate membrane performance in 3.5 ft long tube, (iv) to complete detailed process design and economic analysis.
Date: April 1, 1996
Creator: Anand, M. & Ludwig, K.A.
Partner: UNT Libraries Government Documents Department

The importance of safety in achieving the widespread use of hydrogen as a fuel

Description: The advantages of hydrogen fuel have been adequately demonstrated on numerous occasions. However, two major disadvantages have prevented any significant amount of corresponding development. These disadvantages have been in the economics of producing sufficient quantities of hydrogen and in the safety (both real and perceived) of its use. To date work has mostly been properly centered on solving the economic problems. However, a greater effort on the safety of new hydrogen systems now being proposed also deserves consideration. To achieve the greatest safety in the expansion of the use of hydrogen into its wide-spread use as a fuel, attention must be given to four considerations. These are, obtaining knowledge of all the physical principles involved in the new uses, having in place the regulations that allow the safe interfacing of the new systems, designing and constructing the new systems with safety in mind, and the training of the large number of people that will become the handlers of the hydrogen. Existing organizations that produce, transport, or use hydrogen on a large scale have an excellent safety record. This safety record comes as a consequence of dedicated attention to the above-mentioned principles. However, where these principles were not closely followed, accidents have resulted. Some examples can be cited. As the use of hydrogen becomes more widespread, there must be a mechanism for assuring the universal application of these principles. Larger and more numerous fleet operations with hydrogen fuel may be the best way to begin the indoctrination of the general public to the more general use of hydrogen fuel. Demonstrated safe operation with hydrogen is vital to its final acceptance as the fuel of choice.
Date: September 1, 1997
Creator: Edeskuty, F.J.
Partner: UNT Libraries Government Documents Department

Absolute equation of state measurements of shocked liquid deuterium up to 200 GPa (2 Mbar)

Description: We present results of the first measurements of density, shock speed and particle speed in compressed liquid deuterium at pressures in excess in 1 Mbar. We have performed equation of state (EOS) measurements on the principal Hugoniot of liquid deuterium from 0.2 to 2 Mbar. We employ high-resolution radiography to simultaneously measure the compression of the sample. We are also attempting to measure the color temperature of the shocked D2. Key to this effort is the development and implementation of interferometric methods in order to carefully characterized the profile and steadiness of the shock and the level of preheat in the samples. These experiments allow us to differentiate between the accepted EOS model for D2 and a new model which included the effects of molecular dissociation on the EOS.
Date: June 10, 1997
Creator: Budil, K.S.; Da Silva, L.B. & Celliers, P
Partner: UNT Libraries Government Documents Department

Carbon nanotubes for hydrogen storage as being studied by the National Renewable Energy Laboratory. Technical evaluation report

Description: On June 17--18, the author met with Dr. Mike Heben of the National Renewable Energy Laboratory (NREL) to discuss his research on the development of carbon nanotubes to be used for the storage of hydrogen on-board a vehicle. Dr. Heben has been working for the past several years on a project that will develop single walled nanotubes (SWNTs) composed of carbon for storage of hydrogen. Dr. Heben has spent much time trying to develop a method by which he could produce SWNTs in sufficient quantity, and then demonstrate the adsorption and desorption of hydrogen from these nanotubes at room temperature. While Dr. Heben was able to show hydrogen adsorption levels of up to 10% on a SWNT basis, generation of SWNTs from an arc-discharge was only about 0.05% of the total soot formation. Therefore, increasing SWNT concentration was a key consideration. Findings from the meeting with Dr. Heben are presented.
Date: August 1, 1997
Creator: Skolnik, E.G.
Partner: UNT Libraries Government Documents Department

Metallization of fluid hydrogen

Description: The electrical activity of liquid hydrogen has been measured at the high dynamic pressures, and temperatures that can be achieved with a reverberating shock wave. The resulting data are most naturally interpreted in terms of a continuous transition from a semiconducting to a metallic, largely diatomic fluid, the latter at 140 CPa, (ninefold compression) and 3000 K. While the fluid at these conditions resembles common liquid metals by the scale of its resistivity of 500 micro-ohm-cm, it differs by retaining a strong pairing character, and the precise mechanism by which a metallic state might be attained is still a matter of debate. Some evident possibilities include (i) physics of a largely one-body character, such as a band-overlap transition, (ii) physics of a strong-coupling or many-body character,such as a Mott-Hubbard transition, and (iii) process in which structural changes are paramount.
Date: May 14, 1997
Creator: Nellis, W.J.; Louis, A.A. & Ashcroft, N.W.
Partner: UNT Libraries Government Documents Department

Solar powered hydrogen generating facility and hydrogen powered vehicle fleet. Technical progress report, January 1, 1995--March 31, 1995

Description: The project proceeded generally according to schedule, with most of the work directed at procurement of materials, initiation of equipment fabrication by contractors, and development of educational materials. The first vehicle retrofit was completed in March 1995, and prepared for delivery to DOE`s Energy Technology Engineering Center.
Date: April 1, 1995
Creator: Provenzano, J.J.
Partner: UNT Libraries Government Documents Department

The dual-bed hydrogen production process as being developed by the Florida Solar Energy Center. Process study

Description: Clovis Linkous of the Florida Solar Energy Center is developing a dual-bed hydrogen production process. The idea is to break the water splitting process into two separate chemical reactions, each with roughly {1/2} the electrochemical potential of direct water dissociation. This enables the dual-bed process to utilize a much broader range of sunlight photons than conventional photoelectrochemical (PEC) systems. However, it requires twice as many photons per unit of hydrogen produced. The purpose of this analysis is to evaluate and quantify the trade-offs presented by the dual bed process and determine if it holds economic potential as a hydrogen production technology. The capital cost of a /solar-based water dissociation system is roughly proportional to the solar collection surface area. Thus, the economics rely on how much hydrogen can be produced per unit of solar insolation.
Date: June 1, 1997
Creator: DiPietro, J.P. & Skolnik, E.G.
Partner: UNT Libraries Government Documents Department

Ignition of hydrogen/air mixing layer in turbulent flows

Description: Autoignition of a scalar hydrogen/air mixing layer in homogeneous turbulence is studied using direct numerical simulation. An initial counterflow of unmixed nitrogen-diluted hydrogen and heated air is perturbed by two-dimensional homogeneous turbulence. The temperature of the heated air stream is chosen to be 1,100 K which is substantially higher than the crossover temperature at which the rates of the chain branching and termination reactions become equal. Three different turbulence intensities are tested in order to assess the effect of the characteristic flow time on the ignition delay. For each condition, a simulation without heat release is also performed. The ignition delay determined with and without heat release is shown to be almost identical up to the point of ignition for all of the turbulence intensities tested, and the predicted ignition delays agree well within a consistent error band. It is also observed that the ignition kernel always occurs where hydrogen is focused, and the peak concentration of HO{sub 2} is aligned well with the scalar dissipation rate. The dependence of the ignition delay on turbulence intensity is found to be nonmonotonic. For weak to moderate turbulence the ignition is facilitated by turbulence via enhanced mixing, while for stronger turbulence, whose timescale is substantially smaller than the ignition delay, the ignition is retarded due to excessive scalar dissipation, and hence diffusive loss, at the ignition location. However, for the wide range of initial turbulence fields studied, the variation in ignition delay due to the corresponding variation in turbulence intensity appears to be quite small.
Date: March 1, 1998
Creator: Im, H.G.; Chen, J.H. & Law, C.K.
Partner: UNT Libraries Government Documents Department

Renewable hydrogen production by photosynthetic water splitting

Description: This mission-oriented research project is focused on the production of renewable hydrogen. The authors have demonstrated that certain unicellular green algae are capable of sustained simultaneous photoproduction of hydrogen and oxygen by light-activated photosynthetic water splitting. It is the goal of this project to develop a practical chemical engineering system for the development of an economic process that can be used to produce renewable hydrogen. There are several fundamental problems that need to be solved before the application of this scientific knowledge can be applied to the development a practical process: (I) maximizing net thermodynamic conversion efficiency of light energy into hydrogen energy, (2) development of oxygen-sensitive hydrogenase-containing mutants, and (3) development of bioreactors that can be used in a real-world chemical engineering process. The authors are addressing each of these problems here at ORNL and in collaboration with their research colleagues at the National Renewable Energy Laboratory, the University of California, Berkeley, and the University of Hawaii. This year the authors have focused on item 1 above. In particular, they have focused on the question of how many light reactions are required to split water to molecular hydrogen and oxygen.
Date: June 1, 1998
Creator: Greenbaum, E. & Lee, J.W.
Partner: UNT Libraries Government Documents Department

Hydrogen storage in fullerenes and in an organic hydride

Description: While the authors have demonstrated the importance and usefulness of thermal management to the hydrogen storage in fullerenes, their recent effort has concentrated on materials improvement and physical model development. In this paper, they report the results of this effort as follows: (1) Liquid phase hydrogenation of fullerenes indicated that more than 6 wt% capacity can be obtained at 180 C, 350--400 psi; (2) Dehydrogenation of fullerenes hydrides below 225 C was demonstrated using an Ir-based P-C-P pincer complex catalyst; (3) Cyclic hydrogenation and dehydrogenation tests of an organic hydride at 7 wt% capacity were conducted at 180--260 C; and (4) Physical models developed for fullerenes were determined to be applicable to this organic hydride (with much smaller activation energies).
Date: May 29, 1998
Creator: Wang, J.C.; Murphy, R.W.; Chen, F.C.; Loutfy, R.O.; Veksler, E. & Li, W.
Partner: UNT Libraries Government Documents Department

Low-cost hydrogen sensors: Technology maturation progress

Description: The authors are developing a low-cost, solid-state hydrogen sensor to support the long-term goals of the Department of Energy (DOE) Hydrogen Program to encourage acceptance and commercialization of renewable energy-based technologies. Development of efficient production, storage, and utilization technologies brings with it the need to detect and pinpoint hydrogen leaks to protect people and equipment. The solid-state hydrogen sensor, developed at Oak Ridge National Laboratory (ORNL), is potentially well-suited to meet cost and performance objectives for many of these applications. Under a cooperative research and development Agreement and license agreement, they are teaming with a private company, DCH Technology, Inc., to develop the sensor for specific market applications related to the use of hydrogen as an energy vector. This report describes the current efforts to optimize materials and sensor performance to reach the goals of low-cost fabrication and suitability for relevant application areas.
Date: April 1998
Creator: Hoffheins, B. S.; Rogers, J. E.; Lauf, R. J.; Egert, C. M. & Haberman, D. P.
Partner: UNT Libraries Government Documents Department