STUDENT POSTER AWARDS
1st Place: #16 Fischer Tropsch Synthesis Via Biomass Derived Synthesis Gas
Syed Gardezi, Babu Joseph, John Wolan and Yogi Goswami, USF
2nd Place: #100 Tri-reforming of Methane and CO2: A Novel concept for Catalytic Production of Solid Waste Syngas with Desired H2/CO Ratios for Liquid Biofuels
Philip Saraneeyavongse, Devin Walker, John Wolan and John Kuhn, USF
3rd Place: #37 Enzymatic Hydrolysis of Pulp dissolved in N methyl Morpholine Oxide (NMMO) and Ionic Liquids: A Comparative Study
Subramanian Ramakrishnan, Elizabeth Yau, Gary Brodeur, John Telotte and John Collier, FSU & FAMU
Honorable Mention: #25 Green Poly (lactic acid) Composites Reinforced with Sugarcane Bagasse Residues
Letian Wang and Zhaohui Tong, UF
Honorable Mention: #69 Modification of Lignin Content and Composition to Improve the Efficiency of Bioethanol Production from Sugarcane
Je Hyeong Jung, Fredy Altpeter, Yuan Xiong, Jae Yoon Kim, Walid Fouad, Wilfred Vermerris and Maria Gallo, UF
#16 Fischer Tropsch Synthesis Via Biomass Derived Synthesis Gas
Syed Gardezi, Babu Joseph, John Wolan and Yogi Goswami, USF
Due to the recent surge in energy costs and uncertainties in fuel prices, there is significant interest in seeking alternative sources of energy particularly from renewable such as biomass. Indirect liquefaction of biomass (via the thermo-chemical conversion to syngas followed by liquefaction via Fischer-Tropsch Synthesis or FTS) offers a commercially viable route for meeting the challenge of producing renewable fungible liquid fuels. Apart from biomass, FTS is also the critical step for converting natural gas and coal to liquid fuels.
A FTS technology has been developed for producing middle distillates (diesel and aviation fuel) by using pine chips as the main feedstock. In this “two step” process, pine chips were subjected to an entrained flow gasification process developed by Pearson et al. . The resulting tar free gas is comprised mainly of carbon monoxide, hydrogen, carbon dioxide, methane and some organic contaminants such as benzene, toluene, and naphthalene along with substantial amount of water. For further liquefaction this gas was cleansed using multiple adsorbents. An inline “Shaw Moisture Meter” was used to continuously monitor the moisture content of the feed to the liquefaction process.
For the production of liquid fuels, eggshell cobalt catalysts were used. Cobalt catalysts have several advantages e.g. they produce linear paraffinic hydrocarbons and minimize undesirable water gas shift reaction. This eggshell design is a well-known strategy for producing a narrow hydrocarbon distribution. In this regard previous research work conducted by Iglesia et al. was also consulted . A bench scale fixed bed reactor was used for the conversion of syngas. Modeling of the reactor startup and of adjustment of the reactor packing ensured successful operation resulting in a high conversion and narrow distribution of hydrocarbons in the range of diesel and aviation fuel.
#69 Modification of Lignin Content and Composition to Improve the Efficiency of Bioethanol Production from Sugarcane
Je Hyeong Jung, Fredy Altpeter, Yuan Xiong, Jae Yoon Kim, Walid Fouad, Wilfred Vermerris and Maria Gallo, UF
A large amount of lignocellulosic biomass such as leaf litter residues and bagasse are generated during the sugarcane harvest or after the sugar refining process, respectively. Therefore, lignocellulosic biomass from leaf and processing residues will likely become a valuable feedstock for future biofuel production. However, lignin is recognized as the major limitation to efficient conversion of lignocellulosic biomass to biofuel. Therefore, altering lignin composition or reducing lignin content via RNAi suppression of lignin biosynthetic genes is a promising strategy to increase the efficiency of biofuel production from lignocellulosic sugarcane residues. In the lignin pathway, 4-coumarate-CoA ligase (4CL) and caffeic acid 3-O-methyltransferase (COMT) are key enzymes that catalyze the formation of CoA thiol esters of 4-coumarate and other hydroxycinnamates or the methylation of 5-hydroxyconiferaldehyde to sinapaldehyde, respectively. In this study, COMT and 4CL genes were isolated from the commercially important sugarcane cultivar CP 88-1762 by a combination of cDNA library screening and PCR based approaches. More than 100 transgenic lines harboring COMTi or 4CLi or both COMTi and 4CLi constructs were generated via biolistic gene transfer. Quantitative real-time PCR identified transgenic lines ranging from no suppression to almost complete suppression of the target genes. Accumulation of siRNAs was confirmed in 23 transgenic lines by Northern blot analysis of low molecular weight RNA. These transgenic lines were vegetatively propagated and are currently grown to maturity in a replicated and randomized design. The analysis of lignin content will be carried out in the spring of 2011 and presented at the conference. These results demonstrate that RNAi is effective in suppression of individual or co-suppression of multiple endogenous genes of the complex sugarcane genome. Further these results allow a determination of the relative importance of the targeted alleles or gene families for lignin biosynthesis and biofuel applications in sugarcane.
#91 Florida Algae for Biofuel Production and Landfill Leachate Remediation
Scott J. Edmundson and Ann C. Wilkie, UF
This study explored the indigenous algae of a municipal solid waste landfill for organisms capable of growing on landfill leachate and simultaneously producing a lipid biofuel feedstock. Utilizing landfill leachate as a growth medium for algae greatly reduces the fertilizer inputs required for the production of algal-based biofuels, especially if this technology is to be implemented on an industrial scale. A closed municipal solid waste landfill in Alachua County, Florida, was bio-prospected for indigenous algae with inherent lipid storage capacities that may provide novel algal strains for biofuel production. Algae were screened via microscopic staining and cultured under laboratory and outdoor conditions. Many algae were found to store oils as an energy reserve, especially under low nitrogen conditions. Algae were further tested for their ability to tolerate landfill leachate as a culture medium. Indigenous algae tolerated all tested dilutions (2.5-100%) of landfill leachate. Certain species of algae (Chlorella cf. ellipsoidea, Ankistrodesmus sp.) grew robustly and produced large cellular oil deposits. For the promising species Chlorella cf. ellipsoidea, a 10% leachate solution provides growth equivalent to that obtained using 10% Bold’s Basal Medium. Coupling algal cultivation with the simultaneous remediation of landfill leachate may provide a sustainable method for algal biomass and biofuel production.
#92 Diverting Food Waste for Local Bioenergy Production through Anaerobic Digestion
Ryan E. Graunke and Ann C. Wilkie, UF
Humans are currently facing many global challenges in achieving sustainability. Among these challenges are unsustainable waste production and fossil fuel consumption. Society produces a myriad of different wastes, many of which have potential to be recovered or recycled as energy or material resources. While a variety of different technologies exist to recover energy from some of these wastes, anaerobic digestion offers the opportunity to recover energy from a largely untapped resource: food waste. Food waste is a major problem for Florida, with 1.7 million tons generated annually in the state which is currently buried in landfills. Anaerobic digestion can not only divert this waste from landfills, but can recover usable bioenergy as well. Anaerobic digestion is a microbial process by which organic matter is degraded under anaerobic conditions. The resulting methane-rich (60-80%) biogas can be utilized as a bioenergy replacement for natural gas. These uses include electricity generation, water and space heating, cooking, or as a vehicle fuel in compressed natural gas vehicles. In addition, the effluent from anaerobic digesters can be utilized as an organic fertilizer because the nutrients within the feedstock are conserved and solubilized into plant-available forms (i.e. ammonium). Food waste makes an ideal feedstock for anaerobic digestion due to its rapid degradability and high organic matter content, which corresponds to a high methane production potential. Because anaerobic digestion is a scalable technology, food waste digestion allows for distributed energy generation throughout the community. Food waste is currently produced from many locations including food processors, grocery stores, restaurants, schools, prisons, and households. While a centralized food waste digestion system could handle the food waste from an entire municipality, there are many obstacles to overcome for a large-scale digester. These obstacles include logistics, transportation, and high capital costs. Small-scale food waste digestion may be a more feasible option than large-scale digestion for initial adoption of the technology. This study assessed the potential for small-scale food waste digestion at local food waste generators. Food waste audits were conducted at schools and restaurants to determine the quantity of food waste generated. Food waste samples were analyzed for moisture/organic content, pH, and chemical oxygen demand. Based on this analysis, annual methane production potentials were estimated for each location. These estimates were extrapolated to determine the statewide methane production potential of Florida’s food waste.
#93 Anaerobic Digestion of Biowastes – an Alternative Energy Source for Haiti
Reginald Toussaint and Ann C. Wilkie, UF
Haiti is facing serious environmental degradation problems, making its populace very vulnerable to natural disasters. Energy consumption patterns of the country are the most important drivers of this situation. Even today, firewood and charcoal fuel about 70% of the energy consumption on a national scale. This situation is translated into major deforestation, reducing the forest cover of the country to less than 2%. This study analyzed the current energy situation of Haiti and estimated its biogas production potential in order to evaluate the possible contribution of anaerobic digestion technology. Anaerobic digestion is a microbial process by which organic matter is degraded under anaerobic conditions to produce methane-rich (60-80%) biogas, which can be used as an alternative energy source. The amounts of biowaste generated from different activities were used to estimate the biogas potential of the country. Wood, charcoal, and bagasse represent 55%, 11%, and 4% of the total energy supply of the country, respectively. Hydro-energy contributes 5%, while the remainder is provided by imported oil and its derivatives. However, anaerobic digestion of different kinds of agricultural residues, human and animal wastes generated in the country can produce enough biogas to meet around 20% of the total energy demand of the country. About 5,462,600 m3 and 543,429 m3 of methane can be obtained from human/animal wastes and major crop residues, respectively. A typical Haitian farmer can produce enough gas to meet their energy needs for cooking purposes if all organic wastes generated on the farm are converted into biogas. Implementation of anaerobic digestion technology in Haitian rural sectors can provide sufficient energy to displace firewood use, thus reducing deforestation and improving air quality. Also, in the market places of big cities where large amounts of organic wastes are produced every day, substantial quantities of methane can be produced through anaerobic digestion. Furthermore, this technology offers a sanitary solution for the management of human and animal wastes, while producing a mineralized fertilizer for sustainable crop production.
#97 FAMU BioEnergy Initiative
Clifford Louime and Tanaga Boozer, FAMU
The current clarion call in the United States of America is for environmental sustainability and the creation of innovative new businesses and the accompanying jobs to that end. Government incentives associated with this movement have resulted in the involvement of a significant number of US university scientists and researchers. Early review of funded projects indicates that many of these projects are focused specifically on sustaining the environment within the continental United States. This is a mistake.
Food sources, land re-use, increased weather catastrophes and fuel alternatives are issues that extend far beyond America’s borders. Thus, bioenergy projects at Florida A&M University (FAMU) seek long-term far-reaching solutions that reach across the globe and include meaningful relationships not only domestically but with entities in other countries.
Florida A&M University (FAMU) is a historically black university and an 1890 land-grant institution located in Tallahassee, Florida. The university has a rich history of forging partnerships with other schools across the globe that have resulted in the implementation of important initiatives involving researchers, professors, students, and administrators around the world. So with President Obama’s present focus on environmental sustainability and the creation of innovative businesses and job creation, FAMU is prepared to explore opportunities for new international collaborations.
A team of new agricultural scientists/researchers/engineers, technology transfer administrators, small business development specialists and students (undergraduate and graduate) at Florida A&M University have been working with their counterparts in Botswana (Dr. Neba Alphonsus, Associate Director of Technology Transfer, University of Botswana), Sao Paulo, Brazil (Dr. Goncalo, University of Sao Paulo), China and India (Indus Foundation) to identify best practices and best solutions for the development of alternative fuel sources as well as the transfer of this technology into licensing agreements, and the creation of new small businesses and jobs in relevant industries.
#100 Tri-reforming of Methane and CO2: A Novel Concept for Catalytic Production of Solid Waste Syngas with Desired H2/CO Ratios for Liquid Biofuels
Philip Saraneeyavongse, Devin Walker, John Wolan and John Kuhn, USF
This study focuses on upgrading the Municipal Solid Waste (MSW) syngas for the synthesis of liquid fuels by Fischer-Tropsch Synthesis (FTS). Typical biomass or MSW derived syngas H2:CO is 1:1. This innovation allows for cost-effective one-step production of syngas in the required H2:CO of 2:1 for use in the FTS. A novel gasification of MSW via a tri-reforming process involves a synergetic combination of CO2 reforming, steam reforming, and partial oxidation of methane. To maximize the performance of the tri-reforming catalyst, an attempt to control oxygen mobility, thermal stability, dispersion of metal, resistance to coke formation, and strength of metal interaction with support is investigated by varying catalyst composition and synthesis parameters. These synthesis variables include Ce and Zr mixed oxide support ratios, amount of Mg and Ni loading, metal crystal size, and metal loading method. Catalytic performance testing to assess the activity, selectivity, and stability was performed using a home-built micro-reactor with a residual gas analyzing mass spectometer for gas analysis. Catalyst characterization techniques of Scanning Electron Microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDS), BET surface area measurements, X-ray Powder Diffraction (XRD), Temperature Programed Reduction (TPR), and Temperature-programmed Oxidation (TPO) were conducted to explain the effect of the synthesis parameters. This works highlights the performance of the tri-reforming catalyst and attempts to explain results through catalyst characterization.
#54 Comparison of Culture Media for Regeneration of Elephantgrass (Pennisetum purpureum Schum.) Plants from Mature Seed Derived Callus
Fabio Faleiro, Sobanski Manfredo, Gabriela Luciani and Fredy Altpeter, UF
Elephantgrass (Pennisetum purpureum Schum.) is a highly productive forage grass in tropical and subtropical regions and is also considered as one of the best adapted perennial feedstocks for biofuel production in the southern US. Biotechnology will significantly contribute to the genetic improvement of forage grasses and bioenergy feedstocks. However, a genetic transformation protocol is currently lacking for elephant grass. The first step to enable biotechnological approaches is the development of an efficient plant regeneration protocol from tissue culture. Among the most important factors influencing tissue culture response are genotype, explant and media composition. Using seeds as starting material for the establishment of tissue cultures has not been described for elephant grass. In contrast to immature tissues like immature leaves or inflorescences the use of seeds for initiation of regenerable tissue cultures has the benefit of providing explants throughout the year without the need of maintaining donor plants. In this study, the effect of media composition on tissue culture response of mature seeds derived from elephant grass N-74 was evaluated in a factorial design with 2 auxin sources, 3 auxin concentrations and 2 cytokinin concentrations. Additional media evaluating alternative cytokinin to auxin ratios and the supplementation with L-proline as well as light regimes during callus induction were also compared. This experiment was carried out in a completely randomized design with 5 replications. Each replication was represented by one petridish with 10 longitudinally cut mature seeds resulting in a total of 1,000 explants. The tissue culture response was evaluated for unintended germination, callus initiation, callus growth, necrosis, embryogenesis, plant regeneration rate and regeneration frequency. The means were compared using the Tukey test at 1% level of probability and using linear and non-linear regression analysis. The best media composition supported induction of callus from 100% of the cultured seed explants and embryogenic callus that regenerated plants from 37% of the cultured seed explants.
#57 Genetic Transformation of Elephantgrass (Pennisetum purpureum Schum.) by Biolistic Gene Transfer
Fabio Faleiro, Jae Yoon Kim and Fredy Altpeter, UF
Elephantgrass is one of the prime feedstock candidates for lignocellulosic biofuel production. Biomass yield and low input characteristics like nutrient uptake efficiency and abiotic and biotic stress tolerance are the main targets for genetic improvement of elephantgrass. For example, resistance to Fall Armyworm (Spodoptera frugiperda) is a desirable trait for highly digestible elephantgrass accessions and can be introduced through transgenes encoding specific Bacillus thuringiensis insecticidal Î´-endotoxins (called crystal proteins or Cry proteins). However, a genetic transformation protocol is currently lacking for elephant grass (Pennisetum purpureum Schum.). In this study, embryogenic callus of elephantgrass was used as target for biolistic co-transfer of unlinked constitutive selectable marker (nptII or hptII) expression cassette and the constitutive cry1Fa expression cassette. Different selection agents (paromomycin, geneticin and hygromycin) and bombardment parameters were compared. Following selection and regeneration of plants a total of 24 putative lines were confirmed as PCR positive for both nptII and cry1Fa. 18 of these lines displayed a detectable level of Cry1Fa protein in the Cry1Fa ELISA. We are currently producing vegetative progenies of these transgenic elephantgrass plants for insect resistance testing. This is the first report of genetic transformation and transgene expression in elephantgrass.
#58 Evaluation of Genetic Variability between Elephantgrass (Pennisetum purpureum Schum.) Accessions and Confirmation of Their Crosses Using Microsatellite Markers
Fabio Faleiro, Baskaran Kannan and Fredy Altpeter, UF
Elephantgrass (Pennisetum purpureum Schum.), also known as napiergrass, is a warm-season peren¬nial grass, which is used as forage in tropical and subtropical regions of the world. Elephantgrass produces large amounts of lignocellulosic biomass which makes it a promising bioenergy feedstock. Biomass yield and low input characteristics are the main targets for genetic improvement of elephantgrass. Breeding programs recombine desirable genetic variability from different accessions into new breeding lines for the development of advanced cultivars. This study aimed to characterize the genetic variability in selected accessions of elephantgrass using microsatellites markers. Genetic analysis was done for accessions PP 19, N 39-2, N 74, N 122, N 157 and N 190. Genomic DNA samples were amplified by PCR using previously developed primers to detect microsatellites molecular markers. The markers of each accession were converted into a numeric matrix, from which the genetic distances between the accessions were estimated. Agronomic traits from initial development and biomass production were also used to estimate genetic distances between each pair of accessions. Clustering analysis based on genetic distances allowed to detect a wide range of genetic variability among the evaluated accessions of elephant grass. The N 122 accession presented the highest genetic distance to the other accessions, while the genetic distance between N 157 and N 190 was the lowest using both molecular markers and agronomic traits. Genetic distances using molecular markers and agronomic traits had a significant positive correlation of 0.534. Microsatellites markers were also useful to confirm crosses between the accessions. The verified genetic variability indicates good potential for elephantgrass improvement by traditional breeding using these accessions.
#60 Genetically Improved, Interspecific Hybrids between Elephantgrass and Pearl Millet as Feedstock for Biofuel Production
Baskaran Kannan, Lynn E Sollenberger and Fredy Altpeter, UF
Biofuels produced from lignocellulosic feedstocks are likely to displace substantial amounts of petroleum. Elephantgrass (Pennisetum purpureum Schum.) is one of the most productive candidates for lignocellulosic biomass production in the southern US. Elephantgrass has been introduced to all tropical and subtropical areas of the world because of its ability to produce large amounts of high quality forage biomass. However, elephantgrass is listed as invasive in Southern Florida by the Florida Exotic Pest Plant Council. Plant propagation and establishment of new elephantgrass plantings occurs through vegetative plant parts. Therefore, unlike most seeded crops, seed production is not necessary for elephantgrass biomass production and its suppression will significantly reduce its potential for invasiveness. Pearl millet (Pennisetum glaucum L.) is one of the most drought tolerant C4 grass. Interspecific hybridization between elephantgrass (tetraploid) and pearl millet (diploid) is expected to result in triploid hybrids with male and female sterility which will eliminate production of wind dispersed seeds. Tall, stress tolerant parents were chosen with the goal to generate interspecific hybrids with good productivity and persistence as well as male and female sterility. Pearl millet (AA genome) multiline population with A4 CMS represented the female parent and was open pollinated in the greenhouse with allopolyploid napiergrass (A’A’BB) genotypes Merkeron and N51. We produced more than 3000 triploid, interspecific hybrids between elephantgrass and pearl millet. Phenotypic variability present in these hybrids allowed selecting lines with excellent vigor and sterility. We will present data describing the biomass yield and related traits of interspecific hybrids during Fall 2010 and Summer 2011 in comparison of irrigated and non-irrigated conditions.
#10 Influence of Pt Promoter on CO Activation Pathway
Nianthrini Balakrishnan, Babu Joseph, Venkat Bhethanabotla and Yogi Goswami, USF
Determining the chain-growth pathway is very important to understand the Fischer Tropsch Synthesis (FTS) mechanism. FTS consists of the following steps: CO activation, hydrogenation and O removal, chain growth and termination. Three different mechanisms have been proposed depending on how the C-C coupling is achieved. The carbene mechanism involves polymerization of CH2 intermediates to achieve C-C coupling, the hydroxy carbene mechanism proceeds via dimerization reaction between the adsorbed hydroxyl methylene intermediates and the CO insertion mechanism occurs through insertion of CO into adsorbed alkyl intermediates. However, the carbene mechanism is being supported by many experimental and theoretical works. Catalysts influence the activation pathways and different metals follow different pathways. Promoters are known to influence the catalytic pathways, and hence, it is important to determine the CO activation pathway in the presence of a promoter. There are two types of CO dissociation, namely, unassisted CO dissociation and H-assisted CO dissociation. Unassisted CO dissociation involves the dissociation of CO into C and O while H-assisted dissociation does not involve the direct dissociation of CO.
In this study, the preferred CO activation pathway in the presence of Pt promoter is determined. Assisted and unassisted CO dissociation pathways are explored to determine if the presence of Pt alters the preferential pathway for CO activation. A surface alloy model, where the promoter metal is dispersed on the top surface of the catalyst, is studied. In this work, VASP (Vienna Ab Initio Simulation package) code with Perdew-Burke-Ernzerhof (PBE) form of the generalized gradient approximation (GGA) functional is utilized for the exchange and correlation functional. The electron-ion interactions are modeled by the projector-augmented wave (PAW) method. The activation barrier and the transition states are determined using the Climbing Image Nudged Elastic Band (CI-NEB) method.
#24 Comparison of Pyrolysis Mass Spectrometry and Near Infrared Spectroscopy for Genetic Analysis of Lignocellulose Composition in Populus
Jianxing Zhang, Evandro Novaes, Matias Kirst and Gary Peter, UF
Genetic analysis of wood chemical composition is limited by the cost and throughput of direct analytical methods. Indirect methods such as Fourier transform near infrared (FT-NIR) offer an alternative for rapid, low cost method. In FT-NIR, calibration models and their predictions are typically developed and validated from small sample sets. These models are subsequently used to estimate wood chemical composition from larger sets of new samples. However, no direct comparison of direct and indirect estimates of wood chemical composition and the genetic parameter estimates have been reported for the same population. Here we compare for a single poplar family genetic parameter estimates obtained for wood chemical composition with data from pyrolysis molecular beam mass spectrometry (pyMBMS) and FT-NIR.
Over two thousand young greenhouse grown wood samples were analyzed for chemical composition with pyMBMS (Novaes et al. 2009. New Phytologist, 182, 878-890). We used 1505 samples to build a Fourier transform near infrared (FT-NIR) calibration and validate a model based on partial least square for lignin percent, corrected lignin, G-lignin, S-lignin, and sugars (C5 and C6). A FT-NIR spectrometer, equipped with an X-Y stage auto-sampler was used to improve the scanning efficiency. The sample set was randomly divided into calibration (500) and prediction (1005) sets. The coefficient of determination (R2) for the calibrations ranged from 0.56 to 0.87, and the prediction model R2 ranged from 0.37-0.81. Stronger calibration and prediction statistics were obtained with lignin compared with carbohydrates. For lignin the best prediction (R2 = 0.88) was obtained for lignin percent. For carbohydrates, the strongest prediction statistics (R2 = 0.71) were obtained for the m/z 144 ion which comes from cellulose. Genetic analysis of pyMBMS data and FT-NIR predictions were compared to evaluate the utility of the indirect FT-NIR method relative to the direct pyMBMS method for parameter estimates. QTL analysis was used to compare the results between pyMBMS and FT-NIR.
#27 Activity and Transcriptional Regulation of Bacterial Protein-Like Glycerol-3-Phosphate Dehydrogenase of the Haloarchaea in Haloferax volcanii
Katherine Rawls, Jonathan Martin and Julie Maupin, UF
Glycerol is a primary energy source for heterotrophic haloarchaea and a major component of â€œsaltyâ€ biodiesel waste. Glycerol is catabolized solely by glycerol kinase (encoded by glpK) to glycerol-3-phosphate (G3P) in Haloferax volcanii. Here we characterized the next critical step of this metabolic pathway: the conversion of G3P to dihydroxyacetone phosphate by G3P dehydrogenase (G3PDH). H. volcanii harbors two putative G3PDH operons: (i) glpA1B1C1, located on the chromosome within the neighborhood of glpK, and (ii) glpA2B2C2, on megaplasmid pHV4. Analysis of knockout strains revealed that glpA1 (and not glpA2) is required for growth on glycerol. However, both glpA1 and glpA2 could complement a glpA1 knockout strain (when expressed from a strong promoter in trans) and were required for the total G3PDH activity of cell lysates. The glpA1B1C1, glpK, glpF (encoding a putative glycerol facilitator), and ptsH2 (encoding a homolog of the bacterial phosphotransferase system protein Hpr) genes were transcriptionally linked and appeared to be under the control of a strong, G3P-inducible promoter upstream of glpA1. Overall, this study provides fundamental insights into glycerol metabolism in H. volcanii and enhances our understanding of central metabolic pathways of haloarchaea.
#37 Enzymatic Hydrolysis of Pulp dissolved in N methyl Morpholine Oxide (NMMO) and Ionic Liquids: A Comparative Study
Subramanian Ramakrishnan, Elizabeth Yau, Gary Brodeur, John Telotte and John Collier, FSU & FAMU
The first step in the conversion process of biomass to biofuels or hydrogen lies in picking an environmentally friendly solvent which is capable of breaking up the crystalline microstructure of cellulose. Once the cellulose is in suspension, enzymes (cellulases) are added to the reactor to hydrolyze the cellulose to simple sugars that are then fermented by bacteria to biofuels. Till date, a number of solvents have been used for dissolving cellulose and for reprecipitating it by the addition of an anti-solvent thus making it a multi-stage process. In this work, it is shown that the number of processing steps can be reduced by directly carrying out the enzymatic hydrolysis in NMMO and Ionic liquids (Emim Ac and Emim DEP) which are excellent solvents for dissolving crystalline cellulose. Dissolving pulp of degree of polymerization 1160 is used as the substrate and Accellerase 1000 purchased from Genentech is the cellulase used. The rates of enzymatic hydrolysis and total sugars released are studied as a function of solution conditions – solution pH and enzyme loading. These studies reveal that the enzymes are active in NMMO and Ionic Liquids with the yields of sugars higher in NMMO than the other two solvents. The decreased yield can be attributed to two factors: solvent inhibition and differences in microstructure of the regenerating cellulose. The rates and yields of hydrolysis of cellulose dissolved in NMMO are also comparable to the rates of hydrolysis of regenerated cellulose suspended in aqueous buffer solutions. These studies will form the basis of the design of a twin screw reactor for continuous processing of biomass to biofuels.
#49 Comparative Life Cycle Assessment (LCA) of Biofuels and Electricity Production from Algal Biomass
Maria Pinilla, Qiong Zhang and Babu Joseph, USF
Due to increasing concerns about energy security, climate change and environmental degradation associated with excess nutrient releases to the environment, algal bioenergy production has attracted a great deal of attention because algae are productive utilizers of CO2 and can use waste-stream nutrients from municipal and agricultural wastewaters, while producing a wide range of fuels.
To understand the environmental impacts associated with algae energy systems, life cycle assessment (LCA) has been conducted. The overall goal of this research is to evaluate the environmental impacts associated with different energy products via different routes across the whole life of algal bioenergy. The bioenergy production system under investigation uses wastewater centrate as a feed stream to provide water and nutrients required for algae growth in photo-bioreactor and flue gas as the CO2 source, assuming the production process is co-located with a power plant. Algal biomass is harvested and dewatered through flocculation and centrifugation. Two conversion routes are considered in this research: 1) algal biomass converted to liquid biofuels via a gasification process; and 2) algal biomass converted to electricity via anaerobic digestion and combined heat and power process. Environmental impacts associated with these two conversion routes were evaluated under four different scenarios. The base case scenario consists of providing the required nutrients and CO2 for algae growth through wastewater and flue gas. In the second scenario, fertilizers are used as a source of nutrients, and flue gas is used as a source of CO2. In the third scenario, wastewater is used as a source of nutrients, and chemical CO2 is used as the carbon source. And, in the fourth scenario, fertilizers are used as a source of nutrients, and chemical CO2 is used as the carbon source.
This LCA study used the experimental data, simulation results from process modeling and data from several LCA databases and literature. The environmental impacts were identified and analyzed using a LCA Software (GABI 4); and the impact assessment was performed based on the Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) methodology.
It was found that neither of the processes has a positive energy balance. The largest energy requirement was algae cultivation, which accounts for approximately 50% and 80% of the total energy requirement for gasification conversion route and anaerobic digestion route, respectively.
In addition, the results reaffirmed that the only way to make the algae bioenergy production sustainable and feasible is using wastewater and flue gas as nutrient and carbon sources for algae cultivation. This study has also identified opportunities for improvement, such as recycling the wastewater produced by the anaerobic digestion process to the algae cultivation stage.
#52 Management of Municipal Biosolids as an Alternative Nutrient Source for Biomass Production
Miguel Castillo, Lynn Sollenberger, Joao Vendramini, Kenneth Woodard, Yoana Newman and George O’Connor. UF
High-yielding biomass crops remove significant quantities of soil nutrients, and nutrient replacement using inorganic fertilizers may not be sustainable. Municipal biosolids (MBS) represent an alternative source of nutrients for the production of bioenergy crops like elephantgrass (Pennisetum purpureum Schum.); thus understanding the effect of management practices on MBS nutrient release patterns is important. Two experiments were conducted in Florida to evaluate the effect of soil incorporation vs. surface application of MBS on: (i) elephantgrass dry matter (DM) yield, and tissue N and P concentration and removal, (Exp. 1); and (ii) organic N mineralization and DM decomposition rates of MBS measured in the field using a litter bag incubation technique (Exp. 2). In Exp. 1, three treatments supplied 350 kg total N ha’1 yr’1 from surface-applied municipal biosolids (MBS-SA), soil-incorporated municipal biosolids (MBS-INC), and surface-applied ammonium nitrate (NH4NO3). In Exp. 2, MBS was field incubated in litter bags placed on the soil surface or at a 5-cm soil depth. Elephantgrass DM yield, and N and P removal were greater for MBS-INC than MBS-SA. Dry matter yield for MBS-INC was not different than for NH4NO3 fertilizer (22.5 vs. 24.3 Mg ha’1). Removal of N and P increased 39 and 10 kg ha’1 yr’1, respectively, for MBS-INC vs. MBS-SA. Total organic N mineralized was greater for MBS-INC (386 g kg’1) than MBS-SA (308 g kg’1). Incorporation of MBS increases elephantgrass DM yield and nutrient removal compared to surface application and allows MBS to replace a greater proportion of inorganic N fertilizer.
#56 In vitro Chromosome Doubling of Superior Interspecific Hybrids between Elephantgrass and Pearl Millet Using Different Antimitotic Chemicals
Fabio Faleiro, Baskaran Kannan and Fredy Altpeter, UF
Elephantgrass (Pennisetum purpureum 2n = 4x = 28) produces large amounts of biomass in tropical and subtropical regions and is considered a prime candidate for production of lignocellulosic biofuel. Interspecific hybridization between elephantgrass and pearl millet (Pennisetum glaucum 2n = 2x = 14) may allow to improve important traits (e.g. drought tolerance, biomass quality and production). In contrast to elephantgrass and pearl millet, which produce large amounts of seeds, interspecific hybrids are male and female sterile due to triploidy (2n = 3x = 21) and do not produce seeds. Chromosome doubling of the triploid hybrids may restore seed production and fertility, allowing backcrosses with elephantgrass to further enhance biomass production and persistence. In this study, chromosome doubling was performed in vitro from the most persistent and productive interspecific hybrids. Callus was induced in vitro from cross-sections of the immature leaf whorl of five superior interspecific hybrids (MN 12, MN 18, MN 51, MN 54 and MN 55). Embryogenic calli were incubated for 48h with two alternative concentrations of the antimitotic agents Oryzalin or Trifluralin. Stomata size measurements and flow cytometry were performed following plant regeneration from embryogenic callus and transfer to soil. A total of 328 regenerated plants were obtained and 74 presented altered ploidy according to flow cytometer analysis. Stomata longitudinal diameter was a good indicator of altered ploidy. The treatment with 5 µM Oryzalin produced the highest number (55) of plants with altered ploidy. Chromosome doubling was obtained for all five superior interspecific hybrids. The highest numbers of plants with altered ploidy was obtained from MN 18 and MN 51 genotypes with of 29 and 27 plants, respectively. The plants with altered ploidy have been transferred to the field to evaluate agronomic performance and fertility. The best performing plants with recovered fertility will be used in further elephant grass breeding cycles.
#72 Accumulation of Recombinant Hyperthermostable GH10 Xylanase Xyl10B in Transgenic Sugarcane Enables Efficient Hydrolysis of Sugarcane Xylan to Fermentable Sugars for Bioethanol Production
Jae Yoon Kim, Walid Fouad, Guang Nong, Maria Gallo, James Preston and Fredy Altpeter, UF & American University in Cairo
Sugarcane (Saccharum sp. hybrids) is the highest yielding biomass producer and globally one of the most important feedstock for bioethanol production. The sugarcane plant consists of about 75 % stalks from which the juice for sugar crystallization is extracted. The other 25% of the plant consists of leafy material accounting for 10 to 25 tons per hectare which is typically reduced by open air burning. Sugarcane bagasse, a fibrous residue of cane stalks left over after the crushing and extraction of the juice from sugarcane is one of the largest cellulosic agro-industrial byproducts. Both, bagasse and sugarcane leaves represent an inexpensive and abundant cellulosic feedstock for fuel ethanol production. Biofuel production from lignocellulosic biomass depends on technology that efficiently and economically releases fermentable sugars from multi-polymeric cell wall components. Xylan is after cellulose, the most abundant polysaccharide in grass and wood biomass and must be hydrolyzed to its component sugars (xylose or xylobiose) before fermentation to ethanol. Endoxylanases are the main enzymes involved in xylan hydrolysis. In planta production of cell wall degrading enzymes will reduce costs of enzyme production. Constitutive, apoplast or chloroplast targeted expression cassettes of the codon optimized, hypothermostable GH10 xylanase from Thermotoga maritima (xyl10B) were generated for in planta expression. Transgene integration, expression and enzymatic activity were evaluated following biolistic co-transfer of the xyl10B and the selectable nptII expression cassettes by Southern blot analysis, PCR, RT-PCR, ELISA, Western blot analysis, flourometric xylanase activity analysis, Congo red assay and sugar release assay. 17 transgenic sugarcane lines showed clearly detectable xylanase activity. Highest expression was detected in mature leaves. The in planta produced enzyme was purified and sugarcane xylan was used as a substrate. TLC analysis confirmed the superior catalytic activity and stability of the in planta produced enzyme with directly fermentable xylobiose as the main degradation product.
#28 Towards Efficient Co/SiO2 FTS Catalysts: Study of Cobalt Nanoparticle Size Effects on Reaction Kinetics
Bijith Mankidy, Babu Joseph, John Wolan and Vinay Gupta, USF
Growing concerns of pollution, in addition to the rapidly depleting oil reserves, motivate research towards production of clean synthetic hydrocarbon fuels using catalytic technologies such as Fischer Tropsch Synthesis (FTS). We have synthesized cobalt (Co) nanoparticles with precise size control (1-14nm). FTS catalysts were prepared by immobilizing these cobalt nanoparticles on sub-micron sized SiO2 by surface functionalization technique. We have focused on utilizing an in situ AABSPEC reactor to study the dependency of Co nanoparticle size on catalytic activity. Chemical interaction of carbon monoxide (CO) gas on catalyst nanoparticle surface is one of the primary steps in Fischer Tropsch Synthesis. To understand the CO reaction kinetics occurring on FTS catalyst surfaces, we investigated the elementary CO oxidation reaction on Co-oxide nanoparticle surface to study the dynamics of different intermediate steps involved in CO2 formation by using infrared spectroscopy. Activation energies for the steps and their dependence on nanoparticle size were estimated. Various characterization techniques used for the characterization of the nanocomposites such as dynamic light scattering, TEM, and XRD will be discussed.
#108 Covalent Immobilization of Glucose Oxidase on Pyrolyzed photoresisit electrode surface for biofuel cells
Yin Song and Chunlei Wang, FIU
Enzymatic biofuel cells (EFBCs) involving oxidizing biological fuels by enzyme-modified electrodes attracted considerable attention. This study firstly describes and evaluates a computational model for the miniaturized EBFCs. Meanwhile, the grafting of diazonium salts on pyrolyzed photoresist electrode surface without externally applied electrochemical induction for EBFCs is studied. The resulting surfaces were characterized using cyclic voltammogram (CV), X-ray photoelectron spectroscopy (XPS), FT-IR. Influence of concentration and immersion time of diazonium salts was investigated. Using this functionalization method, immobilized glucose oxidase exhibits better functional properties than noncovalent physical absorbed enzymes. By using CV and XPS, the coverage of functional groups and enzyme immobilization efficiency of the electrode surface was characterized. The effort on developing reliable covalent bonding, increasing the enzyme loading to furthermore improve the power density of biofuel cell will be discussed in this talk.
#122 Bacterial Biocatalysts for Consolidated Bioprocessing of Hemicelluloses to Fuels and Chemicals
Mun Su Rhee, Virginia Chow and James Preston, UF
Different forms of lignocellulosic biomass represent major renewable resources derived from solar energy via photosynthesis. Several of these are abundant in the southeastern United States and amenable to development as major sources of fuels and chemicals. Energy crops, poplar and energy cane, and agricultural residues, sugarcane bagasse and sorghum, are candidates for bioconversion to targeted products. The hemicellulose fraction, representing 20 to 30% of these resources, may be efficiently converted, via secreted xylanolytic enzymes, to sugars for intracellular metabolism and conversion to biofuels and chemicals by fermentative bacterial biocatalysts. We have identified and characterized xylan-utilization systems from bacteria at the gene and enzyme level, and applied the appropriate enzymes for efficient conversion of xylans to fermentable pentoses, xylose and arabinose. This has led to the identification of bacteria for the secretion of xylanolytic enzymes, assimilation of the products of extracellular depolymerization of xylans, followed by efficient intracellular metabolism. Xylanolytic bacteria, e.g. Paenibacillus spp., are candidates for downstream engineering to produce lactate or ethanol. Other bacteria capable of fermentation, e.g. Bacillus subtilis, have been engineered for secretion of xylanolytic enzymes for optimal conversion of hemicelluloses to lactate and ethanol. These developments may provide new biocatalysts for consolidated bioprocessing of hemicelluloses for cost-effective conversion of lignocellulosic resources to alternative fuels and chemicals.
#25 Green Poly (lactic acid) Composites Reinforced with Sugarcane Bagasse Residues
Letian Wang and Zhaohui Tong, UF
Poly (lactic acid) (PLA) composites reinforced by sugarcane bagasse residues were prepared using twin-extrusion. By using near zero-value bio-based residues, these composites are not only 100% renewable and biodegradable, but also have the competitive cost in comparison with petroleum-based composites. The sugarcane bagasse residues (10-30 wt.%), containing different content of fibers and all the remaining lignin, were used to prepare lignocelluloses reinforced PLA composite with desirable physical and chemical properties. In this study, the sugarcane bagasse residues include the residues originally from the sugar extraction process, after pretreatment, and after fermentation of biorefinery processes. The varieties of different bagasse residues include the composition, particle size and its surface reactivity during the chemical and biological (enzymes, microbes) treatments that the biomass is subjected to. The effect of these varieties on the morphologies, thermal properties, mechanical properties and the molecular weight of PLA composites was studied. Furthermore, a coupling agent (Desmodur® VKS 20) was used to increase the interfacial bonding of PLA with lignocelluloses. Desmodur® VKS 20 is a mixture of diphenylmethane-4, 4′-diisocyanate (MDI) with isomers and higher functional homologues (PMDI). The microstructure and the properties of the composites in the presence of couple agents were also investigated in this study. It was found that this coupling agent could extend the polymer chain and therefore improved the mechanical properties of the composites.
#38 Seasonal Changes in Physiological and Morphological Characteristics of Perennial Bioenergy Grasses in Florida
Chae-In Na, Lynn E. Sollenberger, John E. Erickson and Kenneth R. Woodard, UF
Quantifying plant morphological and physiological changes throughout the growing season is critical to indentifying best management practices for bioenergy crops. An experiment was conducted at the University of Florida Plant Science Research and Education Unit during 2010 to investigate monthly changes in characteristics that influence biomass quantity and composition of ‘Merkeron’ elephantgrass (Pennisetum purpureum Schum.), a breeder’s line of elephantgrass called Schank and ‘L79-1002’ energycane (Saccharum spp.). Canopy height, dry tiller mass, tiller density, leaf/stem ratio, leaf area index (LAI), dry matter concentration, and shoot neutral detergent fiber (NDF) were quantified beginning in early June and every 28 d thereafter until November. Canopy height of Merkeron (3.6 m) and Schank (4.3 m) increased until November, but energycane height changed little after September (3.7 m). Energycane and Merkeron tiller mass reached a maximum in September, but Schank tillers continued to accumulate mass until October. In October, dry tiller mass was greatest for Schank (279 g), intermediate for Merkeron (197 g), and least for energycane (158 g). Tiller density was greatest in June and decreased for all grasses until September after which it remained relatively constant at 24, 19, and 16 tillers m-1 of row for energycane, Merkeron, and Schank, respectively. Leaf/stem ratio decreased from June through November for all grasses, and Schank had the lowest ratio throughout most of the season, reaching 0.23 in November. Elephantgrasses reached maximum LAI in late June (Schank, 6.2; Merkeron, 6.1), but energycane reached a maximum of 5.1 in July. The LAI of all grasses decreased nearly linearly from September through the end of the growing season. All grasses increased dry matter concentration from June (avg. 13.9%) through October (avg. 32.5%), but there was little variation among genotypes. Energycane had greater NDF (664 g kg-1) concentration in June than either Schank or Merkeron (614 and 612 g kg-1, respectively). However, in November, energycane NDF (667 g kg-1) was lower than for the elephantgrasses (avg. of 702 g kg-1). Based on the characteristics observed, the breeder’s line Schank elephantgrass has excellent growth potential and is capable of utilizing the full growing season to accumulate biomass in this environment.
#71 Genetic Variation and Control of Anatomical, Chemical, and Mechanical Wood Properties of Juvenile Wood in Loblolly Pine
Alejandro Riveros Walker, Xiaobo Li, Patricio Munoz, Dudley Huber and Gary Peter, UF
Wood cores were collected from 3800 4-year old loblolly pine (Pinus taeda) trees from 2 sites in the CCLONES trail (Baltunis et al. 2007). Core wood density and latewood percentages were determined with x-ray densitometry, C6 and C5 carbohydrate as well as lignin contents of rings 3 + 4 were determined with pyrolysis molecular beam mass spectrometry, and wood velocity stiffness was measured both in isolated cores and in-trees in the field. Interestingly, substantial phenotypic variation was observed for wood properties. Wood lignin content in rings 3 + 4, varied from 21.3 to 35.6%. Wood carbohydrate peak height varied about two-fold for 5 and 6 carbon sugars and 5 plus 6 carbon sugars combined. Velocity stiffness ranged from 2.2 to 12.1(km2/s2) measured in standing trees in the field and 1.8 to 21.4 (km2/s2) measured in the lab with dried 5 mm increment cores. Specific gravity (SG) varied from 0.184 to 0.518 for whole cores, 0.337 to 0.498 for year 3 and 0.229 to 0.554 for year 4. Latewood and earlywood SG ranged from 0.352 to 0.677 and 0.165 to 0.444 for year 3 and from 0.289 to 0.748 for latewood and 0.130 to 0.454 for earlywood in year 4. Latewood percentage varied from 1.68 to 53.32 in year 3 and 1.44 to 66.82 in year 4. Genetic parameters – clonal repeatability, narrow sense heritability, additive, dominance and epistatic components: and pairwise genetic correlations were computed and will be reported for all wood properties.
#85 Understanding Lipid Metabolism in the Green Algae Chlorella Protothecoides: From a Biological Question to a New Source of Biofuel
Elton Goncalves and Bala Rathinasabapathi, UF
The potential of algae as a source of clean and high quality biofuels has attracted the attention of researches in the most diverse areas, with much of the efforts been focused on scaling-up the production as well as harvesting techniques. However, several fundamental questions on algal lipid synthesis and accumulation are yet to be resolved. The most interesting aspect is the regulation and accumulation of triacylglycerol (TAG) upon stress. Our main focus is on TAG accumulation in the green algae Chlorella protothecoides, which has been reported to accumulate lipids up to 80% of cell dry weight. We use radiolabeling experiments with 14C-acetate to track lipid synthesis, membrane remodeling and TAG synthesis under nitrogen starvation and other stress treatments. Our results show that membrane remodeling is an important factor in TAG accumulation under nitrogen starvation.
#106 Elephantgrass Biomass Production under Hydroponic Conditions
Hermes Gerardo-Cuervo, Scott J. Edmundson and Ann C. Wilkie, UF
Elephantgrass (Pennisetum purpureum Schum.) is a perennial herbaceous grass with potential as a dedicated cellulosic biomass crop due to high biomass productivity, when the correct fertilizer rate is applied. The production of landfill leachate in Florida landfills is approximately 770 gal/acre/day and leachate is typically characterized by having high concentrations of ammonia-nitrogen. This fixed nitrogen may provide a replacement for synthetic fertilizers and thus reduce the cost of biomass production. In this study, it is hypothesized that leachate could be used as an alternative nutrient source to supply ammonia-nitrogen for elephantgrass biomass production. However, due the high toxicity of ammonia and heavy metals in this liquid, leachate cannot be applied directly to soil. Since hydroponic cultivation is a method of growing plants without soils (grown in water), this may be an option to produce elephantgrass on landfill leachate. The present study evaluated the tolerance of elephantgrass to survive and grow under hydroponic conditions using landfill leachate as the sole source of nutrients. Leachate was obtained from the Alachua County Southwest Landfill (Archer, FL). Elephantgrass was hydroponically cultured in four concentrations of leachate diluted with tap water: 1) 50%L – 50% leachate, 2) 30%L – 30% leachate, 3) 20%L -“ 20% leachate, 4) 10%L- 10% leachate. Elephantgrass biomass was harvested when the concentration of ammonia-nitrogen decreased below detectable limits (0.1 mg/L). Plants in all treatment groups grew and accumulated biomass. Biomass of leaves, tillers and roots as well as number of tillers per plant were not statistically different (p < 0.05) among treatments, showing that P. purpureum has a high tolerance to landfill leachate. Results indicate that elephantgrass can tolerate and produce new tillers and roots at all tested concentrations of leachate under hydroponic conditions. Although these results are preliminary, landfill leachate may be a promising source of nutrients for biomass production from elephantgrass cultivated under hydroponic conditions.
Carbon Capture and Storage:
#77 Synthesis Tools for Carbon Assessment in Ecosystems
Brandon Hoover, N.M. Knox, Sabine Grunwald, T.A. Martin, X. Xiong, P. Chaikaew, J. Kim and B. Cao, UF
The size of the terrestrial carbon pool is only surpassed by ocean and fossil fuels. Due to unique climatic and landscape condition, Florida’s natural and agro-forest ecosystems have a great potential to sequester carbon in plant-biomass and soils. There are a large number of research projects concerning carbon and related environmental properties. These projects are scattered across multiple disciplines and spatial and temporal scales. The obstacle is to synthesize knowledge on carbon dynamics and cycling and to accurately assess carbon pools and fluxes at coarse scales, ranging from county to the regional and larger scales. The objective of this project is to address these obstacles by creating a database infrastructure for the carbon science community. This infrastructure is focused on ecosystems in Florida and the southeastern United States. The Terrestrial Carbon (TerraC) Information System is dedicated to advancing terrestrial carbon science through fusion of carbon and environmental data to accurately assess the potential to capture carbon in plant- biomass and below-ground. TerraC offers tools to upload, store, manage, query, analyze, and download data characterizing terrestrial carbon dynamics from various sources, including soils, plants/biomass, atmosphere, and whole ecosystems. The purpose of TerraC is three-fold: (i) advance terrestrial carbon science through sharing of carbon and environmental data; (ii) facilitate environmental synthesis; and (iii) enhance collaboration among researchers, scientists, and extension specialists through shared resources. All data in TerraC will conform to quality standards and can be shared privately among selected users or publicly with any user.
#22 Investigation of Li2CO3 and Na2CO3 eutectic as a high temperature phase change material for CSP plants
Jamie Trahan, Michele Bustamante, Sarada Kuravi, D.Y. Goswami, M.M. Rahman and E.K. Stefanakos, USF
The availability of storage capacity plays an important role for the economic success of solar thermal power plants. Thermal energy storage forms a key component of the power plants for improving their dispatchability. Latent heat storage is viewed as one of the promising thermal energy storage techniques for concentrating solar power (CSP) plants due to the high energy density associated with melting/solidification of a phase change material (PCM). This increase in storage capacity per unit volume of the material reduces the system costs thereby reducing the Levelized Cost of Electricity for large scale CSP plants. Though salt eutectics seem to be appropriate phase change materials depending on the melting point and heat storage capacity, most of their published latent heat values are theoretical. In this study, a binary carbonate eutectic of Li2CO3 and Na2CO3 was evaluated for its latent heat, melting point, and potential for use as a latent heat storage material. Preparation methods for the material include the use of a ball mill and hand grinding. The results were compared and obstacles and issues associated with the material are discussed.
Energy Policy, Workforce Development, and Outreach:
#14 PEEP! A Community Energy Program
Ramona Madhosingh-Hector, UF
PEEP is the Pinellas Energy Efficiency Project, a cooperative education outreach project focusing on energy conversation and greenhouse gas reduction across Pinellas County, FL. This community-based program funded by the American Recovery and Reinvestment Act offers training to contractors and the general public. Methods: Delivery of training and materials (CFLs) is achieved with a targeted marketing strategy that leverages partnerships with existing community and civic organizations. PEEP uses a combination “low tech”/”high tech” approach that include the creation of a PEEP website; utilizing blogs, and social media like Facebook and Twitter; flyers; outreach events; and, television and radio segments. PEEP also launched a Youth Energy Contest to educate younger audiences. Results: To date, this 2 year grant funded project has reached 16,000 residents and distributed 60,000 CFLs. PEEP surveys indicate that 74% of participants turned off lights in unoccupied spaces, 57% unplugged “energy vampires”, and 17% performed home efficiency improvements including insulaton and duct checks. Conclusion: Product distributed results in a savings of 31 million kWh, the prevention of 22,000 tons of CO2 emissions and a savings of $4.5 million by consumers. Follow-up surveys of class participants indicate that participants implemented behavior changes with regard to their energy use at home and made modifications to their home to achieve energy efficiency.
#21 Sustainable Floridians: A Statewide Volunteer Pilot Program
John Linhoss and Ramona Madhosingh-Hector, UF
The Sustainable Floridians Volunteer Program is a statewide education/community development program that teaches Floridians how to use energy and water wisely in the attempt to improve the economic, environmental, and social sustainability of Florida communities. This program was developed in the University of Florida Department of Family, Youth, and Community Sciences, with technical assistance from the UF/IFAS Program for Resource Efficient Communities, the UF Office of Sustainability, and Extension faculty in seven counties. The program objectives are 1) to motivate participants to implement energy and water conservation and efficiency actions, 2) to promote sustainability leadership within the community, and 3) to develop volunteers. Participants meet with the program facilitator for seven sessions. Each session includes PowerPoint presentations, supplemental readings, homework exercises, and group discussions. Participants also complete a personal sustainability action plan and a group project. 63 volunteers have been trained through the Sustainable Floridians program – 27 in Leon County, 11 in Marion County, and 26 in Pinellas County. Since November 2010, this program has recorded 234 hours of direct contact teaching hours, and over 1,000 volunteer hours. Sustainable Floridian Volunteers have worked with neighborhood associations to promote extension, organized outreach efforts, attended sustainability related county meetings, and provided educational materials at community events. The Sustainable Floridians Volunteer program has proven successful at creating motivated volunteers that are interested in promoting sustainability education in Florida.
#32 Can Alternative Rate Payment Schematics Alter Individual Energy Consumption?
Cali Curley, FSU
Increasing energy consumption has been considered a problem for many reason, due to this, attempts to alter consumption has become a policy goal. Stern (1999) presents three domains in which decision making takes place. His framework presents that not only does the equipment matter, but the environment or context of the consumption changes how individuals make decisions about their consumptions. This paper sets up a research design to examine how the structure of the rate payments, regarding energy consumption, alters an individual’s consumption patter. This expands on the recycling literature in order to develop a rate payment schematic that entices individuals to change their consumption behavior. Energy efficient equipment can only eliminate half of the problem, individual usage and behavioral decisions must be altered in order to approach the other half of the problem. This paper sets up an empirical test which can be used to determine how individuals respond to changes in rate payment schematics.
#5 Building the Technician Workforce for Florida’s Energy Future
Marilyn Barger, Richard Gilbert and Jorge Monreal, USF & HCC
The Florida Energy Systems Consortium, FESC, was charged by the Florida Legislature in 2008 to deal with the support of new energy technologies and the preparation of the technical workforce for those technologies. The Florida Advanced Technological Education Center is FESC’s National Science Foundation partner to prepare and execute the technician workforce plan that will put this alternative energy workforce in place on time.
Since the inception of the FLATE_FESC partnership, Florida has steadily made headway toward preparing a technologically advanced workforce to meet the needs of new types of energy production technologies. Starting from a ground base of no colleges offering structured programs in alternative energy technology education in 2009, opportunities for workforce education have steadily grown into 2011. A survey of the 28 State and Community Colleges in Florida, with a 50% response rate, revealed the following. In the 2010-2011 academic year, a total of 45 continuing education courses were offered at various colleges throughout Florida. In addition, a total of six separate FL Dept of Education approved College Credit Certificates in alternative energy specializations were offered. This led to a total of 22 college credit courses offered statewide at various state/community college institutions.
A collaborative effort among Brevard Community College, Tallahassee Community College, Florida State College at Jacksonville, and FLATE has been making inroads into understanding the needs of industry. An industry focus group pointed the team to the need of a new Industrial Building Efficiency curriculum. Implementation efforts are ongoing with the added collaboration of the University of Florida’s Industrial Assessment Center. Additionally, the team made advances this summer toward education of a future potential workforce through coordination of three summer energy camps for middle school students at each regional area. So far, a total of 34 students have been given the opportunity to learn about advanced technologies in Alternative Energy. Approximately 98% of students represented underserved populations.
Advances in educational opportunities to prepare a new energy workforce have taken place at a rapid pace. This pace is likely to continue as new energy technologies continue to reach the market. Especially given the emphasis the federal government is placing on both funding new energy production options as well as education at the community college level.
This poster outlines progress of the FESC/FLATE energy workforce education plan. It indicates the skill sets needed for these alternative energy sector pathways. Finally, it reports on Florida’s current status in its timetable to produce the workforce needed as new alternative energy system manufacturing and generation systems come on line.
#2 Analysis of the Nâˆ’k Contingency in Power Systems
Hongsheng Xu, Neng Fan and Panos Pardalos, UF
Contingency analysis has important function in providing information about the vulnerability of power grids. Many methods have been used in studying the topological structures of power grids for analyzing contingency states. In this paper, we present several graph algorithms for selecting contingencies consisting of failures on buses and lines. Additionally, the interdiction model is also formulated for worst case contingency selection. Our measurement for contingency evaluation is to maximize the social welfare, or to minimize the generating and load shedding cost. Comparing with other measurements for contingency selection, our model is based on economic analysis and is reasonable for real applications.
#13 A Comparison of Soft and Hard-switching Losses in Three Phase Micro-inverters
Dehua Zhang, Qian Zhang, Anna Grishina, Ahmadreza Amirahmadi, Haibing Hu, John Shen and Issa Batarseh, UCF
Micro-inverters are small grid-tie inverters of 150-300W that convert the output of a single PV panel to AC. It is advantageous to extend the micro-inverter concept to large size PV installations such as MW-class solar farms where three phase AC connection is used. By adopting the three-phase distributed AC micro inverter architecture, the following advantages can be gained: (1) maximum power harvesting from each panel; (2) eliminating any mismatch losses between panels; (3) easy and flexible installation; (4) less dc distribution losses. However, the three-phase micro inverter has many challenges such as low cost, high efficiency, high power density, long life expectancy and so on.
Small magnetic components are required to increase the power density of micro-inverters. A high switching frequency is required for compatibility with the small magnetic parts. Soft switching techniques help to increase the switching frequency to more than 100 kHz. Auxiliary Resonant Commutation Pole Inverter (ARCPI) is representative topology of three phase high-efficiency inverter. Actively Clamped Resonant Dc-link Inverter (ACRDCLI) has remarkable features of simple structure with only one auxiliary switch. In addition, Hard Switching Inverter (HSI) is able to gain both high efficiency and superiority control performance if operates on several kilohertz. Based on 350W micro-inverter systems, an efficiency comparison of those three topologies is given in this paper.
In ARCPI, the auxiliary circuits work for a short time about tenth of one switching period only when a commutation required. So ARCPI has little effect to the inverter control scheme. It is able to achieve as high output performance as hard switching inverters. Its auxiliary switches are zero current turn off, but have the reverse recovery issue. In ACRDCLI, dc-link voltage periodically resonates down to zero. Since inverter only commutates at those zero voltage intervals, DPM scheme is adopted to the inverter control. The dc-link voltage of ACRDCLI is always oscillation, therefore, there are predictable high conduction losses on auxiliary switch and ESR inductor. Two-amplitude resonant scheme should be used to control the dc-link for reducing the auxiliary losses.
The measured efficiencies show that ARCPI has the highest value among the three topologies. But the complicated control and topology of ARCPI preclude its use in micro-power applications. The resonant dc-link creates a ZVS condition to the inverter, but the dc-link itself brings losses to the inverter, which make it impractical for the micro-inverters. The hard switching topology can compete with ARCPI at a 20kHz switching frequency. But it is hard to increase the switching frequency with PWM control and it cannot match the high power density requirement of the micro-inverters. Thus developing a simpler control scheme for the hard switching topology, which can increase the switching frequency higher than 100 kHz, could be a promising solution for the micro-inverters.
#35 100W Midrange Wireless Power Transmission System
Jaime Garnica and Jenshan Lin, UF
Non-contact energy transfer is useful in situations where physical contact may be limiting or even dangerous. A midrange (~1m transmission distance) wireless power system using inductive coupling is proposed. The system is simulated using a commercial full wave EM solver as well as custom modeling software. A prototype system consisting of 2 1-m square transmit and receive coils is demonstrated with peak transmission efficiency of 80% and peak system efficiency of 60% at a transmission distance of 1 meter. A more physically and electrically robust coil pair is used to demonstrate power transmission at the level of hundreds of watts over a 1 meter gap. Various switching amplifier topologies are investigated for use on the transmit side as a high efficiency inverter at frequencies from several hundred kilohertz to several megahertz.
#70 Design of Power Management Model for a Solar/Fuel Cell Hybrid System
Rosana Melendez, Ali Zilouchian and Amir Abtahi, FAU
In general, technical and scientific challenges to provide reliable and renewable sources of energy for the current and future generation are enormous, especially so when combined with economic current concerns. The optimization of different power sources for hybrid energy systems may provide the necessary tool to deal with the energy demanding challenges of the future. This work intents to present an intelligent approach to investigate such challenges and provide the possible solutions.
In this research, a Power Management Model (PMM) scheme for optimization of several green power generation systems is investigated. The integration of a Photovoltaic/Fuel cell Hybrid Energy System (PFHES) consisting of solar cells, electrolyzer and fuel cell stack sub-sections is utilized to meet specific DC load bank requirement. The Photovoltaic system is considered as the primary power source to take advantage of renewable energy applications. On the other hand, the integration of electrolyzer-fuel cell sub-sections are utilized as a backup system through a DC link bus with addition of an auxiliary hydrogen storage. As a consequence, an overall power management strategy is designed for the optimization of the power flows among the different energy sources. Thereafter, several cost-effective approaches have been proposed to design the hybrid systems using a suitable Power Management Model (PMM).
Extensive simulation experiments have been carried out to verify the system performance under Power Management Model (PMM) governing strategy. The simulation results indeed demonstrate the effectiveness of the proposed approach.
#116 Thin Film Based Clipper Circuits
Rudraskandan Ratnadurai, Shankar Koiry and Subramanian Krishnan, USF
Metal/Insulator/Metal (MIM) based tunnel diodes have been investigated by various research groups to be used as high frequency rectifiers. However, the rectification behavior of the MIM diode under an applied AC signal has not been understood completely. In an effort to understand the rectification mechanism, a novel technique is presented, wherein the metal oxide layer is deposited with an O2 gradient. This enables the charge carriers to have a unidirectional path for conduction.
In this research, Ni was deposited on Si substrate by DC sputtering. Over Ni layer, a stack of three layers of NiO was deposited with different O2 concentration (10%, 33% and 100%) by reactive sputtering. In between each oxide layer, a thin film of Ni was deposited to form an interface. The surface morphology was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM), composition of films was studied by energy dispersive X-ray analysis (EDX), and thickness of the film was characterized by X-ray reflectivity (XRR). The DC characteristic of the fabricated stack (Ni/NiO (10%)/ Ni/NiO (33%) /Ni/NiO (100%)/W tip) shows an asymmetric DC behaviour with a rectification ratio 1: 1.5 at 1 V. The resistance of the film was in the range 200-300 Î© at 1 V. For AC measurement, input signal from 100 Hz to 5 MHz at a peak voltage of 1V was used. It was observed that after 100 kHz, the output voltage starts getting clipped and a prominent symmetrical clipping occurs at 1 MHz. To our knowledge, no report exists for any material or its film, which can act as clipper. Furthermore, by tuning the O2 concentration in the film, the operational frequency could also be changed.
To understand the mechanism of the clipping, impedance analyses and frequency response analyses were carried out. These analyses reveal that self-induction (L) generated by charge flow in the film induces the clipping and further analyses are underway. A control experiment was also done with Ni/NiO film without gradient and such clipping behaviour was not observed. Thus the MIM stack could be used for AC to DC rectification for high frequency detectors as well as a voltage limiter in various signal-processing devices. This work promises to open up a new area of research to miniaturize electronic circuits used for high frequency applications.
#23 Analysis of Supercritical Fluids for Geothermal Power Conversion
Rachana Vidhi, Sarada Kuravi, D. Yogi Goswami, Elias Stefanakos and Adrian Sabau, USF
This study presents an analysis of a supercritical organic Rankine cycle (SORC) with various refrigerants as working fluids for producing power from a geothermal source. For the present study, a number of pure fluids (R23, R32, R125, R143a, R134a, R218 and R170) and their mixtures are analyzed to obtain the most suitable fluids for different operating conditions. The fluids selected for this study have been shown to have zero Ozone Depletion Potential (ODP) and so are more environment friendly than the other industrial refrigerants. The source temperature is varied between 100 degC – 200 degC, to study its effect on the efficiency of the cycle. The thermal efficiencies at different heat source temperatures have been obtained for a pressure ratio of five. The analysis shows that the condensation pressure, which is determined by the heat sink temperature, affects the overall efficiency significantly. The critical temperatures of the fluids should be much higher than the cooling temperature to ensure complete and easier condensation, but not too high as that would lower the condensation pressure to less than atmospheric pressure. The mass flow rate of the heat source has been obtained at every temperature to get the highest thermal and exergy efficiency. The optimum cycle high pressures have been obtained at different heat source temperatures, while ensuring that the vapor fraction at the turbine outlet does not fall below 0.9. It is found that the thermal efficiencies as high as 20% can be obtained with the highest source temperature and the lowest cooling temperature considered in this study. Even for medium source temperatures, thermal efficiencies higher than 12% are obtained. Some fluids, like R32 could not be used at lower heat source temperatures because of the limitation on the vapor quality at the turbine outlet, but extrapolation of their graph suggests that the efficiency could be high. Mixtures of such pure fluids with some other fluid, that would keep the vapor quality high, have been found more useful at lower temperatures. Exergy analysis has been done for the fluids giving the best thermal efficiencies.
#53 Nanoparticle Catalysts with Applications to the Thermochemical Water-Splitting Reaction
Justin Dodson, UF
Thermochemical water splitting is an environmentally friendly and renewable energy alternative to fossil fuels. Separation of the product gas, hydrogen and oxygen, and extremely high temperatures are necessary for water thermolysis to be viable. Metal oxides such as non-volatile, oxygen-deficient iron oxides can split water through a two-step reaction; where the oxygen-deficient metal oxide is regenerated in the second step. A two-step process allows lower temperatures than direct thermolysis of water by evolving oxygen in a highly endothermic oxide stripping step and hydrogen in a slightly exothermic hydrolysis step. A variety of iron oxide and ferrite based catalysts deposited onto nanoparticle oxide supports will be synthesized, tested for activity at high temperatures, and characterized to determine the effect of high temperature on the activity and catalytic properties. A reactor system, which includes a high temperature furnace capable of attaining 1600°C, has been designed. Preliminary x-ray diffraction (XRD) and overall surface area data has been collected on powder catalysts. As expected, a dramatic decrease is observed in the overall surface area after heating to 1500ºC along with a phase change to a reduced oxide. However, preliminary results indicate that iron oxide supported on nanoparticle zirconia has promise as a catalyst in this reaction. Future work includes completing the construction of the reactor system, determining the hydrogen production levels, and continuing catalyst characterizations in order to limit sintering on the catalyst’s surface, reduce the operating temperature, and increase the hydrogen production in an attempt to make the two-step water splitting reaction economically feasible.
#102 Rectenna Arrays For Sensing and Waste Heat Energy Harvesting
Michael Celestin, Subramanian Krishnan, Shekhar Bhansali, Lee Stefanakos and D. Yogi Goswami, USF & FIU
In this study, the antenna coupled rectifier (rectenna) is studied for potential use as an energy harvesting device. A review of current conversion technologies employing nanowire, piezoelectric materials, graphene, photonics, and photovoltaic principles in addition to rectennas is covered. Emphasis is given on rectenna technology because of the versatility of the platform and additional applications where it may be used. Technological maturity of the various harvesting techniques is presented along with the current applications for each. Future trends in energy harvesting are discussed as well. In addition to comparison of the state-of-the-art harvesting systems currently deployed, current advances in antenna and diode performance are presented and compared to existing work. Existing non-regenerative technologies, such as batteries and micro-fuel cells, are touched on to portray a clear view of the current state of power technologies.
The rectenna can function as a broad spectrum electromagnetic sensor-detecting well into the IR region. There is a strong need in both military and domestic security applications for high speed sensors which provide spectroscopic information about the target in question. Current sensing approaches using microbolometer technology are mature but fail to provide the band selectivity, noise reduction, and response rate desired for next generation sensors. Multispectral target imaging unlocks instant material identification which can be used for narcotics and explosives detection.
Motivation for energy harvesting comes from improvements in the energy efficiency of microelectronic and sensor systems. There are numerous applications where low power devices can be run from local waste energy sources. Often, these sensors or devices have a duty cycle, accessibility, or location which makes running wires or powering by batteries inefficient. Sources of energy most commonly include: mechanical energy and vibration, thermal, electromagnetic (including light), fluid flow, and pressure gradients. The incorporation of micro/nanotechnology energy harvesting, power conditioning, and energy storage solutions monolithically with a sensor permits integrated devices where extremely small packages contain all required functionality for autonomous operation. Dubbed “Smartdust,” this fully deployed platform would represent a major advance in materials science and nanotechnology. Exciting applications for these systems will lead to smart composites which incorporate sensors that can continuously monitor and transmit conditions and predict failure.
#20 Simulation of Alternating Wastewater/CO2 Injection into a Deep Saline Aquifer
Roland Okwen, Mark Thomas, Arlin Briley, Mark Stewart, Maya Trotz and Jeffrey Cunningham, USF & UIUC
Physicochemical modeling of alternating wastewater/CO2 injection into a deep saline aquifer is performed using TOUGHREACT reactive-transport modeling software. The model simulates a proposed wastewater/CO2 injection project located in Polk County, Florida. The model is based on well-log data for an existing deep disposal well in the Cedar Keys-Lawson formation, located 10 miles away from the proposed project site. The model consists of a highly permeable dolomitic-limestone formation interbedded with layers of low-permeability gypsum and anhydrite. The simulation begins with wastewater injection at a rate of 2.7 million tons/year for one year (year 0-1), followed by one year (year 1-2) of supercritical CO2 injection at a rate of 300,000 tons/year. Finally, the injected CO2 is chased with wastewater at an injection rate of 1.4 million tons/year for an additional 48 years (year 2-50). Simulation results suggest that upward (buoyant) migration of CO2 is restricted due to vertical baffling by interbedded low-permeability layers. Vertical baffling also limits radial spreading of the CO2 plume by segregating the CO2 into small “pools” trapped under the low permeability layers. The simulation indicates that injected CO2 completely dissolves into injected wastewater within one year of wastewater injection following the CO2 injection period. Injection of wastewater results in a moderate increase of down-hole pressure that does not exceed a safe limit. Significant in-situ precipitation of non-native minerals is observed due to the composition of the injected wastewater. Simulation results indicate that a realistic vertical permeability distribution may enhance CO2 structural trapping. Finally, the simulation indicates that solubility trapping of CO2 can be increased by chasing the CO2 with wastewater following the CO2 injection period.
#31 Practical Heuristic for Selection of Geochemical Model Basis of Supersaturated Water and Mineral Precipitation
Arlin Briley, Mark Thomas, Maya Trotz, Jeffrey Cunningham and Mark Stewart, USF
Societal energy demand is a major driver of water consumption, forming a nexus of energy and water conservation research. Power plants can aid the effort to stretch our freshwater resources by shifting to non-potable water sources, but alternative water sources are likely laden with solutes which interfere with plant processes. Reverse osmosis recovery of high quality water is viable, but the solutes are concentrated in the byproduct reject water which then has elevated potential for pipe scaling and other problems, and may preclude disposal to open waters. Geochemistry software can be used to model water streams and assess feasibility of alternative water strategies, but computational intensity rapidly increases with the basis (i.e., number of solute types and possible minerals), especially when trying to predict mineral precipitation from supersaturated conditions. Omitting unimportant solute species and considering only precipitate minerals likely to form is necessary to make computer simulations more practical, but there is little guidance on which solutes and minerals are relevant. A four-stage heuristic is offered to identify the subset of solute species and minerals to include in the model for reduced computational load yet minimal effect on validity of results. Stage One: Model water stream of interest based on laboratory analysis of the types and concentrations of solutes and parameters such as temperature, pH, alkalinity, and total dissolved solids. Run geochemistry software with precipitation inhibited to obtain a list of the minerals with respect to which the water is supersaturated. Stage Two: Run software allowing precipitation of minerals such that equilibrium is reached; record minerals formed in this lowest-energy configuration along with predicted water properties such as pH and total solid mass formed. Stage Three: Construct small basis model which omits solute species whose concentrations are very low (suggested threshold: 0.001 molality). Compare predicted water properties to that of the full model as an estimate of error in using the small basis; reinstate solutes if error is unacceptable (suggested threshold: 1%). Stage Four: Recognizing that many of the supersaturated minerals are unimportant because unfavorable kinetics of formation prevent direct formation from an aqueous solution, keep or delete minerals from the geochemical software data based on five considerations. 1) delete all minerals which were not supersaturated in the precipitation-inhibited simulation; 2) keep minerals predicted to form in significant amounts per equilibrium modeling; 3) include minerals that are familiar to industry as scale-forming (such as calcium carbonate, quartz, amorphous silica); 4) delete minerals which are known to form only at high temperature and/or pressure or other geological process; 5) Generally exclude minerals for which reaction rate data is unavailable. The small basis representation (with concurrent reduction in computational intensity) can then be used in kinetic precipitation calculations which account for rate of formation of minerals to estimate type, amount, and distribution of precipitation, including in simulations of interaction between underground rock and water stream if injected for disposal or as part of an operation to safely sequester carbon dioxide in brine aquifers.
#110 Effect of Surface Roughness in Air Photocatalytic Reactors
Yangyang Zhang, Yogi Goswami and Elias Stefanakos, USF
Indoor air quality has become a great concern due to the increased amount of personal time spent in indoor environments. Photocatalysis is a promising technique for remediation of air pollution. Artificial roughness elements on the catalytic coated surface could enhance the turbulence intensity close to the catalytic surface. The enhanced turbulence intensity would translate to an increase in the mass transfer of airborne contaminants to the catalyst surface, improving the efficiency of photocatalysis.
Air flow properties in a photoreactor channel with transverse rib roughness on its walls were investigated by the realizable k-epsilon (k-Ïµ) model. Different shapes, sizes, and arrangements of the roughness elements were modeled to determine which had the maximum enhancement of turbulence intensity in the photoreactor channel. The optimum roughness was determined to be the triangle shape with 30o in zenith angle, the relative height (e/h) equal to 0.05, and the pitch ratio (p/e) equal to 10. The enhancement of turbulence intensity in optimum configuration was 21.29% compared to a similar reactor channel without roughness. The enhanced turbulence intensity may increase more than 100% in mass transfer of airborne contaminants to the catalyst surface.
Cell R & D
#84 Studies of ZnTe as an interlayer for CdS/CdTe thin film solar cells on flexible substrates
Xianjin Feng, Kartikay Singh and Chris Ferekides, USF
The CdS/CdTe heterojunction solar cell on flexible subsrate is a very promising candidate for low cost photovoltaic production process with reasonable energy collection efficiency. A good Ohmic contact to the CdTe absorber layer without electrical losses is needed for the cell to function efficiently. ZnTe is a potential interlayer to form such low resistance back contacts due to the small valance band discontinuity with CdTe and the possibility to be doped degenerately with Cu. In this study, ZnTe thin films have been prepared on the Mo-coated stainless steel substrates by the close spaced sublimation (CSS) technique. Cu-doped ZnTe films are prepared by immersion the as-deposited samples in CuCl-H2O solution. Structural and morphological properties of the ZnTe films as a function of substrate temperature are investigated by using XRD and SEM. CdS/CdTe solar cells with ZnTe and ZnTe:Cu interlayers are prepared and characterized with I-V and spectral response measurements.
#87 CBD CdS Films and TiO2 Buffers for CdTe Solar Cells
Kartikay Singh, Xianjin Feng and Chris Ferekides, USF
CdS is the most commonly used window layer in CdTe based thin film solar cells. It can be deposited by a variety of deposition techniques including Chemical Bath Deposition (CBD). This poster will present the effect of CBD deposited CdS films on the performance of CdTe solar cells. The effect of the film thickness and concentration of thiourea will be discussed. Additionally, the effect of a thin layer of TiO2 deposited by reactive sputtering and used as a “buffer” will also be presented. Solar cells were characterized by J-V and Spectral response measurements.
#95 Graphene Transparent Electrode for Light Harvesting Solar Cells
Wei Zhou, Amare Belay, Nicoleta Hickman and Rodica Khugler, UCF-FSEC
Graphene has focused a great deal of attention due to its unique electrical properties. The exfoliation of graphite oxide is efficient and results in high yields of single-layered graphene oxide (GO). GO is electrically insulating and must be reduced to make it electrically active. In this study, we employed spray coating to deposit the GO films and attempted an inexpensive and environment friendly method, ultraviolet (UV) treatment and thermal annealing under high purity Argon, and widely used hydrazine vapor treatment method for comparison, to reduce the GO films. Optical properties of as sprayed GO coatings were studied. The GO coatings showed very high light transmittance. After reduction, the transmittance of graphene could show a small decrease, and a slight decrease was also observed after the following thermal reduction. For example, a 92% transmittance was observed on the 4 runs spray coating GO sample at 550 nm. However, after UV reduction, the transmittance at 550 nm dropped to 65%, resulting into a 63% transmittance after the following thermal reduction, indicating a very strong reduction effect by UV radiation. At the same time, the electric properties were characterized by four-point probe measurement. The surface resistance of the reduced GO (rGO) film sprayed 2, 4, 6, and 8 runs was measured to be 49, 15, 13, 13 kÎ©/â–¡, respectively, after UV and thermal reduction. It seems the surface resistance almost does not increase after 6 runs spray coating, while the 4 runs spray coating sample already shows both an excellent surface resistance (15 kÎ©/â–¡) and a high transmittance (63% at 550 nm). Surface resistance of hydrazine treated rGO film smaples was also measured to compare with that of UV treated rGO film samples. The suface resistance of UV treated rGO film was too high to meature, while Hydrazine treated rGO film provided 200 MÎ©/â–¡ suface resistance. However, after additional thermal treatment under Ar, the results are comparable. The SEM images indicate a homogeneous morphology of rGO coatings. No obvious aggregation of Graphene has been observed even in the magnified SEM images. Hydrazine and thermal treated rGO film exhibits typical wrinkled structure with corrugation and scrolling due to van der Waals forces during drying and maintaining high surface area. However wrinkled structure was not obvious on UV and thermal treated rGO film sample, instead, some pieces of graphene sheets were observed. It might be explained that the rGO film was soaked by hydrazine vapor and generated more wrinkle structures. In addition, hydrazine vapor removed the small graphene pieces attached on the rGO film. On the other hand, UV radiation was a solid state treatment and kept the rGO film structure unchaged.
#96 Polymerization of PCBM for Organic Solar Cell Application
Amare Benor Belay, Wei Zhou, Rodica Khugler and Nicoleta Sorloaica-Hickman, UCF-FSEC
Phenyl-C61-buryric acid methyl ester (PC60BM) is a material of interest for emerging new-generation organic photovoltics (OPV). The small molecule based PCBM, a modification of fullerene (C-60), is used as electron acceptor material mainly with P3HT electron donor material for use in organic solar cell. While the material has dominant application in OPVs, little efforts are made in preferred processing of the material, PCBM, using polymerization. The polymerization of the material, without degrading the optical property, is required for improved charge transport and carrier collection of the material that is required for improved efficiency in OPVs. In this study, the use of ultraviolet light (UV)-ozone exposure of PCBM is studied using solid state modification of the material. In the study, solution processed PCBM films, deposited and dried over glass, were exposed to UV-ozone at ambient temperature and pressure form 0 to 120 minutes. Using the exposure, an oxygen-linked binding of PCBMs was observed from 5 min to 60 min, but further exposure, typically beyond 120 min, was found to degrade polymerization, i.e., results in depolymerization. For optimized UV-ozone exposure, core-level and valence-band photoelectron spectroscopy studies indicate that the UV-ozone induced oxidation results in polymer like C-O-C binding of PCBMs of the material and a change in the HOMO level, respectively. Solubility of the material in different organic solvents was also studied after the exposure. The study showed a change in solubility of the material, in solvents like toluene and acetone, where it indicates the change in the chemistry of the material that can be related to the C-O-C binding of the material by the exposure. The oxidation process results from the change in the solubility chemistry of the material in relation to the increase in the polarity of the material by the oxidation. Besides, the separate effects of UV-ozone vs. ozone gas alone on the oxidation and/or oxygen-linked binding of the PCBMs are considered individually. Our study indicated that the polymerization can also be processed using only ozone without the UV-light exposure over the surface of the material. Time of exposure dependent oxidation of PCBM, both UV-ozone and ozone, will be discussed based on x-ray spectroscopy (XPS) studies. Furthermore, effect of the method on the optical property of the material will be seen in detail. The method, which is an easily implementable approach for polymerization of PCBM using either UV-ozone or ozone, will also be discussed in relation to its implications on the processing and stability of the material.
#112 A Study of Hot Carrier Effects in the Photocurrent of CIGS Solar Cells
Yige Hu, Gijs Bosman and Tim Anderson, UF
Hot carrier solar cells allow hot carriers to be collected before energy is lost to the lattice. This is accomplished by slowing carrier cooling in the absorber and collecting the carriers using energy selective contacts. This ultimately leads to a higher open circuited voltage since the average energy of the collected electrons is greater than the band gap energy. It also leads to higher short circuited current, leading to an overall greatly improved efficiency. Phonon engineering in the absorber helps to increase the hot carrier lifetime. If phonon engineering successfully applies in the absorber layer, the hot carrier lifetime will be increased significantly. Photocurrent measurements as a function of applied bias are proposed on fabricated CIGS solar cell structures to characterize hot carrier effects. The incident photon energy will define the initial hot carrier energy. The bias dependent electric field in the space charge region affects high-energy carriers differently than low energy carriers. For a given field strength, low energy, thermally generated carriers will be directed to their collecting contacts by the local field, but the hot carriers with initially randomly directed velocities may overcome the field effect and scatter into opposing contacts reducing the photocurrent in this way. Hence via a simple device physical model, a relationship between initial hot carrier energy, electric field in the space charge absorber region, and photocurrent has been established from which the relative density of hot electrons can be determined from measured current voltage data.
#118 High Rate Chemical Vapor Deposition of Cu(In,Ga)Se2 Photovoltaic Absorber
Christopher Muzzillo and Timothy Anderson, UF
Power that is universally available, renewable, and pollution-free is becoming an increasingly relevant commodity. Photovoltaic devices are promising alternative energy sources, but their relatively high cost has so far deterred consumers. Cu(In,Ga)Se2 (CIGS) is a photovoltaic absorber attractive for commercial development due to its record laboratory efficiency of 20.3%. Production expenses can be reduced by using chemical vapor deposition (CVD) to speed up the synthesis and deposition of CIGS without sacrificing material quality. The thermodynamic feasibility of CIGS CVD has been studied. Based on the equilibrium models, a chloride based CVD process has been proposed that would emulate the 3-stage NREL record efficiency process. A reactor was then designed and constructed to simulate separate stages in the continuous CVD process. Studies have been performed comparing actual thin film growth behavior with equilibrium and kinetic models. The apparently accurate predictions demonstrate the potential of this research, and a requisite plan for future work has been proposed.
#41 Enhanced Solar Testing Equipment, Facilities and Research Laboratories
David Block, John Del Mar and Robert Reedy, UCF
The University of Central Florida’s Florida Solar Energy Center made a decision at the beginning of the Consortium program to use about 50 percent of the program’s funds for upgrading, improvement and enhancement of the Center’s solar testing equipment, its facilities for and research laboratories. This paper presents the results of these facilities and laboratories upgrades and improvements. The new facilities and laboratories are:
- Solar systems testing building – Conversion of roof only facility to enclosed building with air conditioning.
- Solar thermal systems and module testing – New test stands and data acquisition equipment to meet increased testing demand.
- PV module simulator testing – New long pulse simulator for PV module research and commercial testing.
- PV and thermoelectric materials and devices laboratory – New PV lab for characterization techniques and new in-situ diagnostics tailored to PV manufacturing processing steps.
The development of these new facilities and laboratories now makes these laboratories permanent and available to all university faculty, students and other potential users.
#48 Solar Energy Policy for PV Manufacturing and Applications
David Block, James Fenton and Philip Fairey, UCF
The overall goal of this project has been to establish a PV manufacturing and applications data base that would be used to stimulate the development of a photovoltaic (PV) manufacturing industry and technology applications in Florida.
This project is now in its third year and both the international and national PV manufacturing and application trends are established and can be summarized as follows:
- China has emerged as the world leader in both cell and module manufacturing with a production of 10,228 Mw or 43% of the world share. The U.S. is ranked 5th with 1116 Mw or 5% of the world total. The U.S. rank of 5th and its market share of 5-6% has remained the same for the past 4 years.
- Crystalline silicon remains the top world choice at 87% (up from 77% in 2009) and will remain at the top. In the U.S., crystalline silicon production is at 71%.
- There is only one U.S. PV company, First Solar, at #2 in the top 15 of the world production companies. First Solar produced 251 Mw of its 1400 Mw world production in the U.S. The other 1177 Mw were produced in Germany and Malaysia.
- In 2010, California remains as the location with the largest installed capacity at 258.9 Mw or 30% of the U.S. market share. New Jersey is second at 137.1 Mw. Florida ranks 8th at 35.2 Mw following from 3rd last year. In 2010, major gains were made by Nevada, Arizona, Colorado, Pennsylvania and New Mexico with Florida dropping slightly.
- Over the 3 years, Florida has had numerous announcements of proposed PV manufacturing facilities, but no large scale plant has transpired. As reported above applications have slightly dropped with the three FPL solar plants being put in production about two years ago. The FPL plants placed Florida into 3rd place nationally.
The above numbers all have grave consequences from both the national and the state perspective. Let’s now talk about jobs produced. For the energy industries, PV produces 23 jobs/Mw, wind is 8 jobs/Mw, nuclear is 4 jobs/Mw, natural gas is 3 jobs/Hw and coal is 0.5 jobs/Mw. Since Florida can produce no manufacturing in wind, nuclear or coal, the only possible manufacturing for Florida is PV. Note that all 4 of the applications produce both installation and maintenance jobs. Thus, the energy policy needs to be directed to PV manufacturing, Florida’s only option.
The key to manufacturing is to have both a magnet and a demand. How does Florida create both of these? Let’s start with the magnet. Florida is positioned to be a magnet because of it winning the DOE funded PV Manufacturing Consortium (PVMC) program. Florida was teamed with SEMATECH of New York who is the prime and won the DOE program (PVMC is a $50 million effort). For the SEMATECH program, Florida’s task is crystalline silicon R&D which, as mentioned above, is the dominate material at 87% of the world’s PV cells. In the PVMC program, a existing 100,000 ft2 semi conductor facility has been dedicated to PVMC. However, the facility needs to be re-furbished before the crystalline silicon pilot manufacturing assembly line can be installed. Once the pilot facility is established, the probability is very high for national PV manufacturing firms to become pilot facility users and then to follow with plants in a near location. This is the magnet. The state must help in the pilot refurbishment effort.
The second need is demand. Production is almost always close to demand for many reasons with California being the prime example. The policy options for demand are portfolio standards, rate tariffs, purchase incentives and actions that will allow utility companies to install PV as a source for peaking power. By using PV for peaking power, utility companies should have no problem with this option since the cost of PV is close to gas turbine costs and because PV can be installed in less than one year. Clearly utilities will not use PV for base load power.
#67 Important Considerations for MPPT Design for PV Systems
Thomas Bennett and Ali Zilouchian, FAU
Power optimization is extremely important in trying to receive the most energy from any renewable energy source. Photovoltaic cells (solar panels) in particular offer an interesting challenge due to how the weather conditions (irradiation/temperature/shading) constantly change the operating power for a fixed electrical load. In addition, diverse electrical loads will result in different current/voltage outputs for the same weather conditions. In order to optimize the load output, DC-DC converters, using Maximum Power Point Tracking (MPPT) algorithms, are placed between the photovoltaic array and the electrical load.
MPPT algorithms introduce many difficulties both in the modeling and in implementation. The modeling difficulties are due to the nonlinear and implicit nature of the dynamic system that require numerical methods, as well as the switching of the converter that creates discontinuous equations. The control system is also challenging due to the fact that the desired voltage is unknown. This requires more intelligent control methods.
Many MPPT approaches have been developed within the last couple decades. Many of them discuss the MPPT algorithm, and take many other things for granted. The author will present many of these important considerations when implementing a PV MPPT system. These will include things such as the effect of the PV model on modeling behavior, errors related to numerical methods, transient behavior of the system due to things such as the duty cycle, and sampling. A short survey of some of the current MPPT methods, as well as a version implemented by the author will also be shown.
#101 The “Solar Sink” Concentrated-Photovoltaic Power Plant
Sean Barton and David Van Winkle, FSU
The “Solar Sink” 400-kilowatt-peak concentrated-photovoltaic power plant under construction in Tallahassee, Florida is discussed. The Solar Sink plant is scheduled for operation in December of 2011 and implements the recent inflatable parabolic-trough solar concentrator (also known as the “solar sausage”). The inflatable is a transparent horizontal cylinder divided into two half cylinders by a reflective membrane. The reflective membrane is forced into a cylindrical curve by differential pressure. The membranes are made of aluminized and un-aluminized PET polyester film. The two compartment inflatable has significant spherical (cylindrical) aberration, but a four compartment inflatable is shown to be effectively parabolic. Overall system design is discussed with an emphasis on current difficulties including unavailability of medium-concentration PV material, reflective losses, PV cooling, placement of PV material, diurnal reduction of aperture, and mounting and solar tracking of the inflatables.
#119 Organic Light Emitting Diodes with Silica/Polystyrene Diffraction Grating for Improved Out-Coupling Efficiency
Wooram Youn, Won Hoe Koo, Franky So, Xiaohang Li and Nelson Tansu, UF & Lehigh
Through numerous efforts to improve the efficiency of organic light emitting diodes (OLEDs), the internal quantum efficiency was able to achieve the unity. Nevertheless, about 80% of light generated is trapped and wave-guided within the structure due to the total internal reflection by the mismatch of refractive indices between each layer. Many of wavelength-scale diffraction grating studies on organic light emitting diodes have been proved to extract those confined light. The periodicity, depth and directionality of the gratings are important factors to determine the out-coupling efficiency. Here, we demonstrate that the OLED with self-assembled monolayer of silica spheres semi-embedded in polystyrene (PS) layer as the grating structure can be effective and practical for the diffraction grating structures due to the properties of simple process to fabricate, and more directionality to improve the light extraction efficiency. Moreover, periodicity and depth of diffraction grating can be easily tuned using different size of silica and PS spheres. It was confirmed that varying periodicity and depth of silica grating, enhancement of current and power efficiencies was achieved maximum 70% and 120% each, compared to the OLED with the flat structure. Such convenient approach for light extraction is attractive and practical for use in lighting application.
#120 Inverse Method for Identifying Intensity from Multiple Flux Maps in Concentrating Solar Applications
Ben Erickson and Joerg Petrasch, UF
Radiative flux measurements at the focal plane of solar concentrators are typically performed using digital cameras in conjunction with Lambertian targets. To accurately predict flux distributions on arbitrary receiver geometries directional information about the radiation is required. However, the intensity, i.e. the spatial and directional distribution of radiation, cannot be directly measured with sufficient resolution. Currently, ray tracing simulations are used to predict the directional characteristics of solar concentrating systems. These simulations lack the ability to account for certain imperfections in reflector geometries and surfaces. We use multiple flux measurements at varying distances from the focal plane in conjunction with inverse methods for radiative transfer to identify the directional and spatial intensity distribution at a desired solution plane.
Rigorous inverse methods have been developed to convert flux maps perpendicular to the focal axis to an intensity distribution at the desired solution plane. The directional binning feature of the in-house Monte Carlo ray tracing program VeGaS was used to validate the method for a two dimensional case with a simple geometry. The intensity distribution obtained from the inverse method was shown to approach the exact solution provided by the program. In addition, the derivation for the three dimensional case is provided. Currently the inverse method is being implemented for the three dimensional case to obtain intensity distributions in UF’s high flux solar simulator.
#105 LIDAR-Enhanced Pitch Control for Optimized Wind Turbine Performance
Rachit Mathur, Jennifer Rice and Jamie Chapman, UF & Texas Tech
Wind turbine reliability is one of the most challenging issues facing the advancement of the wind energy industry, with component fatigue as one of the primary turbine failure mechanisms. The blade pitch system is a critical turbine control component, enabling efficient operation and reduced system loads to extend operational life. With the increase in size and scale of these machines, their susceptibility to the damaging effects of stochastic wind loads increases. Thus, the implementation of ‘intelligent control’ of each individual rotor blade becomes increasingly important for achieving higher system reliability, durability, and precision. While the advantages of pitch control are undisputed, this research seeks to investigate whether overall turbine control can be enhanced by incorporating the information provided by a remote wind sensor (LIDAR) into the individual pitch controllers to minimize the fatigue damage while optimizing energy output.
A variety of modeling and analytical tools will be utilized in this research to evaluate efficacy of a LIDAR-enhanced individual pitch control strategy for increasing system fatigue life. Using FAST modeling and design code we can generate a probability density of system load amplitudes and the respective fatigue life damage as a function of mean wind speeds and turbulence intensities for a specific period of time. Comparing this reference probability density with the measured LIDAR data enables effective pitch decisions to be made based on whether the predicted damage by incoming wind is above a predetermined level. Using this control technique we will make discrete pitch decisions proportional to the size, structure and magnitude of the incoming gust. The fatigue damage endured by the turbine with enhanced control will be compared with that of a conventional, generator torque-controlled individual pitch system to compute the potential increase in the fatigue life. In addition, the increase in the total energy output will be computed. The economic advantage of increased energy output and fatigue life will also be assessed and compared with that of a conventional system to determine the whether the additional cost of installing a LIDAR is economically justified. The focus of this presentation will be the overall research goals and preliminary fatigue load results.