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ADDITIONAL POSTER SESSION

Monday, May 12- 5:15-6:15 pm

BIOMASS (POSTER SESSION)

Biodiesel Production from Waste Oils using Non Catalytic Supercritical Alcohols -Zachary Cerniga, Dr. Aydin Sunol, Dr. George Philippidis, University of South Florida

 

A novel sustainable biodiesel manufacturing process has been developed. The continuous process produces biodiesel from waste oils and waste alcohols collected from the local community. It aims at powering the University bus system using a portable plant with a capacity of several hundred thousand gallons a year. The process is intensified by utilizing supercritical alcohols in transesterification reactions with residence times of a few minutes and minimal separation requirements compared to conventional biodiesel production methods. Moreover, the process is very tolerant to water in the waste oil, unlike the conventional alternatives, and incorporates heat integration to minimize utility requirements. Although alcohol cost is minimal, efforts to utilize alcohol waste from University hospitals and laboratories is expected to further reduce the cost of raw materials and boost the sustainability of the technology. With this intensified process wastewater generation is virtually eliminated compared to conventional production methods, which generate 30 gallons of wastewater for every 100 gallons of biodiesel produced. The glycerol by-product is significantly purer than that from conventional methods and can serve as precursor in high-value pharmaceuticals production or soap production for local use. An orthogonal experimental design has been implemented to identify the effects of important process variables, including reaction temperature, residence time, and molar ratio of alcohol to oil. The temperature of operation ranges from 250 C to 350 C and the pressure from 1,500 to 2,000 psia, while the excess alcohol is about 2-8 times the stoichiometric amount and is recycled. Moreover, optimal conditions have been identified by means of response surface methodology. The biodiesel yield is determined by ester content, which is measured via gas chromatography. The presentation will report on the pilot plant operation, process scale up, transportation system powering implications, and life cycle considerations.

Supercritical Gasification of Wet Biomass – Aydin K. Sunol, University of South Florida

 

The biomass resources can be organized into four groups, as forest residues, agricultural residues, municipal solid waste, and residual industrial waste. Citrus is the leading crop cultivated in Florida, over 800,000 acres and about 100 million citrus trees. Ninety percent of the citrus is processed into juice and the remainder is sold as fresh fruit. The pelletized peel is primarily used as cattle feed and the cost is 60-155 $/ton per Florida Citrus Association. The only possible large scale utility of biomass is its utility as energy source, possibly by producing hydrogen which is the clean energy future of the world. The only waste generated from citrus crops that is large enough for hydrogen production is citrus peel. One million tons/yr citrus waste residue is generated in Florida. The moisture content is 60-80% while hydrogen content is about 6-8%.

The hydrogen produced will find immediate and sustainable use in NASA space programs as well as providing renewable and clean fuel for other applications. Evaluation of hydrogen conversion potential of citrus peel is well overdue. Various biomass conversion technologies have matured over the last three decades and there is a very intense work in Europe, Japan, as well as USA on this technology. The most promising technology for high moisture content biomass is supercritical water gasification. This technology is also compatible with recovery and fractionation of oils from orange peel. The typical commercial facility may be 30 metric ton/day for which there will be more than sufficient citrus peel. The typical hydrogen production is expected to be 10 grams hydrogen for 100 gram feed.

The presentation will focus on several comparisons of biomass energy conversion technologies in terms of efficiency and carbon dioxide emissions. The objective is to evaluate the position of supercritical water gasification in biomass technologies from the viewpoint of life-cycle evaluation.
As for electricity generation, efficient processes are thermal gasification combined cycle, supercritical water gasification combined cycle, and direct combustion in order of efficiency for low moisture content biomass.

However, Supercritical water gasification combined cycle is the most efficient for high moisture content biomass which is the case for citrus peel. The tradeoff between carbon dioxide emissions and total cost of technologies is analyzed so that the most cost-effective technology can be determined for different CO2 emissions constraints. Computed results show that biomass is mainly consumed for electricity and heat generation so as to utilize finite biomass resources efficiently. Transportation fuels are generally made from fossil fuels. Cost-effective processes for CO2 reduction are thermal gasification and reforming when the present efficiency and prices are assumed. Supercritical water gasification is also one of the optimal processes when the relative cost to fuel cell decreases. Improving heat exchange efficiency also contributes toward enhancing the position of supercritical water gasification in biomass technologies

 

Intragenic Precision Breeding Supports Targeted Modification of Lignin Biosynthesis in Sugarcane – Jung JH, Dermawan H, Altpeter F, University of Florida:IFAS

 

Sugarcane (Saccharum sp. hybrids) is a highly productive C4 grass used as the main source of sugar and more recently to produce bioethanol. Biofuel production from the abundant lignocellulosic sugarcane residues is expected to not only improve the production rate per unit land area, but also promote green cane harvesting and minimize the open air burning of sugarcane leaf litter. However, bioconversion of lignocellulosic biomass to biofuel is highly limited due to the presence of lignin in plant cell walls. Down-regulation of lignin biosynthetic enzymes has been proven to be a promising strategy to increase the efficiency of bioconversion from lignocellulosic biomass. In the lignin biosynthetic pathway, 4-coumarate-CoA ligase (4CL) is one of the key enzymes, which catalyzes the formation of CoA thiol esters of 4-coumarate. In this study, 4CL gene was isolated and suppressed to reduce lignin content in sugarcane. In order to facilitate regulatory approval, an intragenic approach was used to suppress 4CL. The entire DNA expression cassettes that were used for the generation of the lignin reduced sugarcane were derived from sugarcane and/or sexually compatible sorghum. A total of 60 intragenic sugarcane lines was generated suppressing the 4CL gene up to 97%. Intragenic sugarcane lines with high level of 4CL suppression exhibited brown coloration in the basal internodes and vascular bundle cells. Data describing the total lignin content in the stem biomass will be described.

 

 

 

Breeding Elephantgrass for Elevated Biomass Yield and Biosafety – Baskaran Kannan, Marco Sinche, Carlos Corsato, Fredy Altpeter, University of Florida-IFAS

 

Elephantgrass (Pennisetum purpureum) also known as napiergrass is one of the best adapted warm season perennial grasses for production of large amounts of high quality forage biomass. The biofuels industry has identified elephantgrass as one of the most productive feedstocks for lignocellulosic biofuel production in the southern US. However, the currently available cultivars and naturalized populations can produce large amounts of wind dispersed seeds, which contribute to their potential for invasiveness. Elephantgrass can be propagated through stem cuttings for new plantings. Hence, seed production is not required for establishment and its suppression will significantly reduce its potential for invasiveness.

In order to enhance the biosafety of elephantgrass, interspecific hybridizations were made between elephantgrass (2n=4x=28) and pearl millet (2n=2x=14), which results in genotypes that display male and/or female sterility due to their triploid (2n=3x=21) nature. We produced more than 3000 triploid, interspecific hybrids between elephantgrass and pearl millet. Phenotypic variability present in these hybrids allowed selecting lines which produced similar or higher biomass amounts than the seed producing elephantgrass cultivar Merkeron. We will present data describing the biomass yield and the sterility of interspecific hybrids evaluated in replicated field trials.

Flowering in elephantgrass is induced by shortening day length. Genotypic differences were observed in different elephantgrass accessions regarding the the beginning and duration of their flowering period. This offers the opportunity for the enhancement of biosafety by genetic hybridization and selection of late-flowering, non-lodging accessions with high biomass yield. Therefore, five genetically distant accessions were crossed to produce around 1600 F1 hybrids. The 50 highest yielding hybrids and 183 hybrids from the two most contrasting parents were vegetatively propagated in replicated row plots for evaluation during two years and four harvest cycles with a commonly used elephantgrass cultivar Merkeron as a control. Phenotypic data were recorded to correlate different traits with biomass yield. Late-flowering, non-lodging F1 hybrids were identified with significantly higher biomass yield than Merkeron. Multi-location testing in larger plots is being carried out to confirm the superior accessions for the development of high-yielding, late-flowering cultivars.

 

Emulsion of Lignin-co-butyl Acrylate as a Biobased Polymer System – Suguna Jairam, Zhaohui Tong, Fei Wang, University of Florida: IFAS

 

Stable waterborne latex polymers are gaining a lot of importance due to their various advantages in environment-friendly production, ease in manipulation and a variety of application areas including packaging, paints and coatings, polymer foams and films. For instance, latexes involved in packaging and coating applications tend to focus on the use of styrene and acrylic based copolymers in emulsion and miniemulsion polymer systems. This blend is used to provide strength and flexibility in polymer films hence formed. However, these systems are entirely based on materials sourced from petroleum products. Due to their large-scale use and the vastly diminishing petroleum resources available, sustainability in the synthesis of polymers has become an essential aspect of material synthesis and research. With this issue in mind, the current research is focused on using lignin as a co-monomer in the synthesis of a sustainable emulsion polymer system. Lignin is a bio-based poly-phenolic material that forms 15% of all plant material providing support to the plant structure. It is also known to possess anti-UV and anti-microbial properties apart from high mechanical strength and thermal properties. In the bio-ethanol process, lignin is extracted from the biomass as waste and is discarded. This makes lignin a highly useful and abundant waste resource. The objective of the current research was to modify lignin as a monomer to replace styrene in the styrene-co-butyl acrylate system and to assess the properties of the polymer formed. Organosolv lignin was modified to its acrylic hydrophobic form resulting in a lignin based monomer. This monomer was then copolymerized with butyl acrylate via emulsion polymerization resulting in a novel lignin based latex. The latex was cast and air-dired to form films used for characterization. Characterization of the modified monomer and polymer included H1NMR, SEM imaging, thermo gravimetric analysis, tensile testing and molecular weight estimation via GPC. H1NMR profile indicated the successful grafting of polymerizable acrylic group on lignin structure. SEM images of the polymer indicate growth of the polybutyl acrylate particles along lignin cores as templates. Analysis of the results indicated that increase in modified lignin monomer (even in low concentrations) in the emulsion system improved the mechanical and thermal properties of films formed. Based on current results, lignin can be a feasible candidate for sustainable and green polymer synthesis in a variety of application areas.

 

Development and Management of Brassica carinata (Ethiopian Mustard) as a “Drop-in” Biofuel – Ramdeo Seepaul, Sheeja George, Ed Coppola, David L. Wright, Jim J. Marois, University of Florida – IFAS

 

Producing biofuel crops while preserving land committed to growing food/feed/fiber crops is crucial in the light of the urgent need for U.S. independence from first generation fuels while meeting agriculture’s mandate to feed an increasing world population. Florida in particular, being one of the highest consumers of petroleum fuels in the region, could benefit tremendously by using its underutilized (12 million acres of warm season perennial grass pastures) and 500,000 acres of winter fallowed row crop acreage for renewable biofuel production. We propose to use Brassica carinata, an oilseed crop, as a feedstock for biofuels. B. carinata is superior to other Brassica species and oilseed crops in terms of seed size, drought and heat tolerance, and low rates of seed shattering. B. carinata is also better adapted under low input systems and tolerant to weather extremes (low rainfall, high temperature) especially during the grain filling period. B. carinata has considerably higher yields (2500-3000 kg/ha) and higher oil content (above 40%) than other members of the Brassicaceae or other oilseed crops. Because B. carinata is not a food crop, can potentially be grown on marginal land with minimal input, does not compete with traditional row crops, can be used as a feedstock for biofuel production, and can tolerate warm climates, production of this species in Florida may provide an additional economic means to agricultural producers, especially those with small and medium-sized farms that may not be on prime agricultural land. Moreover since only the seed is being harvested and crop residues are being returned to the soil it is a more sustainable option to conventional biomass based feedstock development.

At the UF-IFAS North Florida Research and Education Center, we have been evaluating B. carinata germplasms to identify regionally adapted varieties for cultivation in the Southern United States. In our current project we are looking at optimum planting dates, row spacing, seeding rates, nitrogen fertilizer rates, fungicide and herbicide effect etc. We are also evaluating the potential of B.carinata to be used in a crop rotation system and also examining soil physico-chemical characteristics under the influence of this crop. Data from these trials will be presented at this workshop.

 

Sunflower Genotype Evaluation for Bio-oil Production in Florida -Fedenko, JR, Wilke, AC, Erickson, JE, University of Florida: IFAS

 

Sunflower is widely cultivated in the United States and globally as an oil crop, with 1.3 million
US acres harvested in 2013 for oil. Sunflower is commercially cultivated primarily in North and
South Dakota, and has recently received renewed interest as a rotational cash crop for the
Southeastern US. Research has indicated that optimal yields of sunflowers in the Southeast can
be produced with early spring planting, potentially allowing production of a second summer
crop, such as sweet sorghum, depending on sunflower days to maturity. While yields of hybrid
oil sunflowers have recently been documented in Mississippi, most cultivars have been
optimized for production in Northern regions, and several studies have examined seed and oil
characteristics of native, wild sunflowers in the Southeast. The current research quantified the
growth habit and oil content of 10 sunflower genotypes with potential as oilseed crops in
Florida. Oil content varied between cultivars from 184 to 381 g oil seed, and total seed yields
were heavily affected by cultivar. Seed oil content was not correlated with stem biomass, and
cultivars varied significantly in morphology, number of heads produced, total height, and
resistance to disease. As a component of the research, a group of undergraduate interns were
involved in the planting, management and harvest of the experiment, and throughout the
process were provided practical and theoretical knowledge about biofuels and renewable
energy. The research suggests that sunflower production may produce comparable oil seed
concentrations in the Southeast compared with current production regions if intensively
managed.

 

Bioenergy Plant: Efficient Method for Disposing Biodegradable Materials – Jose Sifontes, Sigarca

 

The Bioenergy Plant is a unique system that provides an economic and sustainable solution to the management of biodegradable waste, renewable energy and agri-business to rural and urban communities. It handles a wide variety of wastes such as municipal solid waste (MSW), waste activated sludge (WAS), animal waste, agricultural waste, food waste, industrial waste, energy crops, etc. The system provides communities the option to more cost effectively manage waste and save on energy costs through the production of distributed power and production of valuable organic soil conditioners.The Plant is compact, modular and flexible to locate, mobilize, and expand; safe, state of the art and passive with no production of runoff, noise, noxious odors, scum, and silt common to most digesters. Waste generated is loaded in specially-designed containers which are then placed inside bioreactors where it is digested in a heated and moist environment. Byproducts from processing include biogas and organic soil conditioners. Additional benefits include: lowering the greenhouse effect, complying with laws and regulations, improving the hygiene and aesthetics, generating employment and political stability and reducing the threat of waste to communities and the environment. The Bioenergy Plant was a winner on the 2008 Farm to Fuel Program and it is endorsed by University of Florida, TRDA, Florida Department of Agriculture and Marion County. The technology has been tested, verified and demonstrated to the equine community for several years at the Southeastern Livestock Pavilion in Marion County.

 

 

Anaerobic Digestion of Food Waste from Alachua County Schools – Ryan E. Graunke, Ann C. Wilkie, University of Florida-IFAS

 

As society quickly realizes that fossil fuel is a finite resource and recognizes the many problems associated with procuring and combusting fossil fuels, it is inevitable that humans must find alternative energy solutions. In this effort, every potential resource must be tapped. One such potential resource is food waste. Food waste can become usable energy through the process of anaerobic digestion. In anaerobic digestion, naturally-occurring microorganisms consume organic matter and produce biogas through a series of metabolic processes. In its natural state, biogas is approximately 60% to 80% methane and can be used in much the same way as natural gas (e.g. as a direct-combustion fuel or to produce electricity using modified generators). Also, biogas can be refined into biomethane, which is 100% methane and is identical to natural gas; it can even be injected into the existing natural gas infrastructure to offset fossil natural gas. While many types of organic matter can be converted into methane, food waste is an increasingly growing problem, especially in Florida’s urban and suburban areas. By tapping into food waste as a resource, many of the problems associated with the current landfill disposal of approximately 2.3 million tons of food waste each year in Florida can be alleviated. There are many sources of food waste including grocery stores, restaurants, schools, prisons, food manufacturers, farms, and residential areas. Because anaerobic digestion is a scalable technology, a centralized digester can be constructed to collect food waste from a community or, alternatively, individual digesters can be set up at food-waste-generating locations to digest food waste and utilize the resulting biogas on-site. This study examined the potential of food waste digestion at schools. Schools are not only a major source of food waste in Florida, but by spearheading food waste digestion at schools, students can also learn important lessons on the roles of waste and renewable energy in the larger context of sustainability. For this study, waste audits were conducted at 3 local schools in Alachua County during which all waste was collected, categorized, and sorted from the schools’ cafeterias over 1 to 2 weeks. Daily-collected food waste from each school was homogenized and representative samples were obtained to measure the physicochemical parameters of the food waste and estimate the daily methane potential from each school. The data were normalized on a per student basis in order to extrapolate the potential energy production from all of Alachua County’s schools.

 

Renewable Energy Production through Organic Waste Recycling at Christianville, Haiti – Reginald Toussaint, Ann C. Wilkie, University of Florida-IFAS

 

Recovery of renewable energy and valuable nutrients from recycling of agricultural waste has become very critical in the transition from a fossil-based to a bio-based farming system. With the increase of agricultural activities as a response to unprecedented population growth, the amount of organic wastes generated from agricultural production, livestock, and food processing is continuously increasing and their disposal poses serious environmental, economic and logistical challenges. Christianville is a non-profit organization that has been involved in providing long-term sustainable solutions for more than a decade in Haiti. Christianville has an orphanage with 300 children and are feeding more than 1000 other students every day. As a result, Christianville is a net food and energy consumer in a country where food and energy production is very scarce. Sustainable farming systems, fish farms, livestock, and food processing are among the diverse ongoing activities being operated to feed the Christianville community, with plans in place for expansion. With the anticipated increase of agricultural activities at the beginning of the coming year, organic waste production is consequently expected to increase significantly and therefore provides justification for the implementation of a farm-scale biodigester for environmentally sustainable waste handling as well as energy and plant-nutrient recovery. This project aims at implementing biodigestion at Christianville as a sustainable technology for handling organic wastes generated from diverse ongoing activities while providing a clean-burning renewable energy in the form of biogas, as well as an enriched-fertilizer source to enhance food production and food security for this Haitian community.

 

Methane Productivity of Organic Waste Treatment by Two-Phase Anaerobic DigestionVictoria Cortés, Ann C. Wilkie, Zamorano Agricultural University and university of Florida-IFAS

 

Two-phase anaerobic digestion methodology has a positive impact on the conditions required for the groups of microorganisms involved in the process. Using this methodology, we can obtain a reduction of the hydraulic retention time (HRT) and higher efficiency of organic matter removal. The efficiency of anaerobic digestion was evaluated by comparing the methane production in 250 mL one and two-phase anaerobic batch reactors using the organic wastes of coffee pulp and boreal waste, as substrates with seasonal availability, and the separated fiber from swine waste as a substrate with continuous availability. Organic loads of 1.00, 2.00, 3.00, 4.00, 6.00 and 8.00 kg VS/m3 were applied to one-phase reactors and to the methanogenic phase of the two-phase reactors, using biol as inoculum for these reactors and a mixture of facultative bacteria from waste stabilization pond effluent as inoculum for the acidogenic phase of the two-phase reactors. The biol used as inoculum was the effluent from active anaerobic biodigesters operated with dairy manure. The tests were performed at mesophilic range of 33–35 °C. The setup of the hydrolytic-acidogenic phase reactors required a HRT of two days, run within an organic loading range of 14–20 kg VS/m3. The effluent from this reactor was analyzed to calculate the organic load needed for the methanogenic reactor setup. One-phase reactors were also set up at the same organic loads to obtain the HRT required for the degradation of the substrate and the organic load which causes failure in the process. The one-phase reactors operated at loading rates between 1-3 kgVS/m3 were also used to obtain the maximum yield of methane for each substrate through a methane index production assay (MIP). The MIP values obtained were 0.67, 0.35 and 0.49 m3 CH4/kg VS for coffee pulp, boreal waste and fiber from swine manure, respectively. The maximum operating loads in methanogenic phase reactors were 2.50, 7 and 8 kg VS/m3 for coffee pulp, boreal waste and fiber from swine manure, respectively. Values higher than this were followed by a system failure. The optimal operational load for the methanogenic phase reactor was found to be 2.00 kg VS/m3 when the coffee pulp substrate was fed at pH values lower than 4, without adding alkali reagents. The HRTs required for the degradation of the substrates in one-phase reactors were 28, 35, and 40 days for coffee pulp, boreal waste and fiber from swine manure, respectively. In addition, the HRT required by the two-phase anaerobic reactors in all assays to obtain the same amount of methane produced in one-phase reactors was reduced by at least 30%. The ultimate yield of methane obtained with the two-phase anaerobic reactors was comparable to the results obtained with the one-phase reactors, but at lower HRTs.

 

Co-production of Astaxanthin and Biofuels – Alec. S. Shoelson, Ann C. Wilkie, University of Florida-IFAS

 

Cultivation of algae can yield a diversity of high-value bioresources, which mitigate the cost of biofuel production. Microalgae are currently cultivated for such high-value compounds as astaxanthin, beta-carotene, lutein, etc. Haematococcus pluvialis is a freshwater species of Chlorophyta from the Haematococcaceae family. When stressed, the cells encyst into immobile aplanospores and accumulate astaxanthin, a carotenoid pigment. Astaxanthin has strong antioxidant properties and offers a wide range of health benefits. It is therefore highly sought after and is used heavily in the aquaculture and pharmaceutical industries. However, because it can be difficult to obtain from natural sources, synthetic substitutes are often used that lack many of the benefits natural astaxanthin provides. The objective of this study was to optimize the growing conditions of Haematococcus along with stressing the cells to produce astaxanthin and determine a way to extract it. Haematococcus pluvialis was cultivated using a variety of techniques and conditions. An orbital shaker with volvox media proved to have the most optimal conditions of those tested. Haemoatococcus cells were stressed into producing astaxanthin by being put under high light and low nutrient conditions. Due to astaxathin’s popularity and high price, Haematococcus could be grown and sold to supplement algal biofuel production. If Haematococcus is grown at a biofuel facility, the profits from the sale of astaxanthin could be used to offset other costs. The residual biomass after astaxanthin extraction could be anaerobically digested to produce methane-rich biogas, an alternative to natural gas, which could be used to produce electricity for algal production or processing facilities. Burning methane produces carbon dioxide, which can be recycled back into growing more algae. Also, carbon dioxide produced from bioethanol fermentation processes can be directed towards algal cultivation. If able to be grown and harvested in an efficient and affordable way, Haematococcus and astaxanthin may have wide-reaching implications for integrated biofuel refineries.

 

Characterization of Cellulosic Ethanol Stillage and Use as an Algal Growth Medium – Tommie B. Lovato, Ann C. Wilkie, University of Florida-IFAS

 

Cellulosic ethanol is a potential alternative to petroleum-based fuels and, because it is created from lignocellulose found in woody plant materials, it does not compete directly with food production, unlike corn-based ethanol. One obstacle in cellulosic ethanol production is dealing with the stillage by-product that is typically high in nutrients and chemical oxygen demand. Growing algae for biofuels and high-value pigments like β-carotene or astaxanthin requires high nitrogen inputs to sustain growth and produce more biomass, providing a possible bioremediation option for stillage. Various treatment options exist for stillage including anaerobic digestion that has been shown to substantially reduce chemical oxygen demand. In addition, algae can serve as a potential feedstock for anaerobic digestion and the subsequent creation of biogas introducing a conceivable link between multiple bioenergy prospects. The objective of this study was to cultivate algae using stillage as a nutrient source. Sugarcane bagasse stillage from the UF-IFAS Stan Mayfield Biorefinery Pilot Plant was characterized, measuring pH, electrical conductivity, light transmission, total nitrogen, total ammoniacal nitrogen, total and soluble phosphorus, and total and soluble chemical oxygen demand. A strain of the microfilamentous cyanobacterial algae Spirulina sp. was isolated using a modified Spirulina standard culture medium replacing nitrate ion with ammonium as the nitrogen source. This culture was then inoculated into flasks with 2% dilutions of stillage supplemented with Spirulina nutrients using Spirulina’s preferred sodium bicarbonate as a carbon source. The experimental group using the 2% stillage dilutions produced more biomass than the control under the same conditions, as measured by optical density absorbance readings. Lipid analysis using nuclear magnetic resonance based against a triolein standard showed that the algae biomass had low neutral oil content and was not ideal for algal biodiesel production. However, the biomass growth under experimental conditions points towards a potential use of stillage as a nutrient source in algae production. The algal biomass can be utilized as feedstock for biogas production via anaerobic digestion.

 

Reuse of Cellulosic Bioethanol Residuals – Jianru Shi, George O’Connor, Ann C. Wilkie, University of Florida-IFAS

 

Increasing demand for fossil fuels, coupled with diminishing fossil fuel reserves, create an urgent need to develop renewable energy sources as a replacement for fossil fuels. Biofuel systems have emerged as one such alternative to fossil fuels. First-generation biofuels are made from sugary or starchy plants and have generated food security concerns. The development of second-generation biofuels emphasizes the use of non-edible (cellulosic) feedstocks and green chemical technologies. However, the commercialization of second-generation biofuel is held up by technical as well as economic issues. Many studies focus on enhancing technology to improve ethanol productivity, while very few studies recognize the importance of the byproducts associated with cellulosic ethanol production. Beneficial reuse of these residues could provide cost savings as well as lessen the negative environmental impacts imposed by chemical fertilizers. An estimated 20 liters of stillage byproduct is generated for every liter of ethanol produced, so an effective solution for byproduct treatment is necessary when considering large-scale production of cellulosic ethanol in the future.

This study critically evaluates the possible treatments for residues from cellulosic ethanol production and discusses the potential environmental and economic impacts of byproduct land application. The first step is to characterize and compare the stillage from different types of feedstocks. Treatments applied to first-generation bioethanol residues may or may not work on cellulosic ethanol residuals. Different initial chemical components of cellulosic feedstock, combined with the various pretreatment processes, may also result in byproducts that require different types of treatment prior to reuse management.

Land application has been considered as one of the possible approaches for final disposal of cellulosic ethanol byproduct. Several studies have reported positive effects of land application such as improving soil structure, reducing soil erosion, increasing soil organic matter content, and reducing nutrient leaching. These potential benefits as well as the effects of these residuals on crop yields, especially biofuel feedstocks, are being evaluated as part of this research.

 

Evaluation of Energy Recovery Potential from Sweet Potato Stillage – Wendy Mussoline, Ann C. Wilkie, University of Florida-IFAS

 

Sweet potatoes, or eTubers, have recently emerged as a potential non-grain feedstock for bioethanol production. More than 80% of the global sweet potato production occurs in China where it is mainly used for processed food, animal feed or alcohol. In Florida, however, marginal land from former citrus groves is being utilized by CAREnergy to grow high-starch eTubers for bioethanol production. The crop tolerates heat, requires little irrigation, and has been shown to produce 4 to 5 times as much starch per acre as corn.

The waste residues from the conversion process remain a concern, however, as approximately 20 liters of stillage can be generated for every liter of ethanol produced. The sweet potato stillage contains relatively high concentrations of organic compounds (25,000 to 60,000 mg COD/L), total nitrogen (1000 to 6000 mg/L) and total phosphorus (500 to 1000 mg/L). Anaerobic digestion is an effective means of reducing the chemical oxygen demand (COD) in the stillage and converting it to biogas, while still conserving the nutrients for soil enrichment.

The focus of this research is to evaluate the biogas potential of sweet potato stillage by conducting baseline biogas index tests under mesophilic conditions. The tests will be conducted using both stillage and culled sweet potatoes. Characterization of the feedstock will include parameters such as total solids, volatile solids, COD, total nitrogen, ammonia nitrogen and total phosphorus. Biomass reduction, biogas yields and retention times will be measured to assess the feasibility of this approach and to quantify the overall improvement of process efficiency by using biogas rather than fossil fuels for steam generation. Higher COD reduction (89% versus 78%) has been previously documented for potato stillage under mesophilic as opposed to thermophilic conditions.

Waste characterization of the digestate will also be evaluated to ensure that sufficient macro- and micro- nutrients are available to return to the eTuber crops as fertilizer. A recent life cycle analysis that evaluated bioethanol production from sweet potatoes concluded that replacing coal with a cleaner fuel and eliminating chemical fertilizers could effectively increase net energy gain by nearly 50% and decrease the environmental impact from eutrophication by nearly 40%. Though the eTuberâ„¢ ethanol industry has the potential to benefit local communities and agriculture in Florida, the market potential and environmental sustainability of the industry are clearly dependent upon energy recovery from the stillage and recycling of the digestate.

 

Anaerobic Co-Digestion of Swine Manure and Microalgae for Biogas Production – Meng Wang, Eunyoung Lee, Qiong Zhang and Sarina Ergas, University of South Florida

 

Anaerobic digestion has been widely used to stabilize livestock wastes and produce energy. However, centrate produced after anaerobic digestion contains large amounts of nitrogen (N) and phosphorous (P), and additional nutrient removal processes are required before discharge. Microalgae have gained a lot of attention as an alternative biofuel source, due to their high growth rates, independence from arable land usage and ability to remove nutrients from various wastewaters. This study investigates the integration of nutrient recovery and on-site energy production into farms by applying algae cultivation and anaerobic digestion technology. In this system, nutrients are removed from the anaerobic digester centrate by algae growth and the harvested algae biomass is co-digested with swine manure for on-site energy generation. Previous studies have found that centrate from digested swine manure is a good medium for algae cultivation. However, there is limited research on anaerobic co-digestion of swine manure and microalgae.

In this study, six treatments with different proportions of indigenous Chlorella sp. grown on synthetic swine waste (A) and swine manure (SM) were performed in batch anaerobic digesters. The combinations of wastes based on volatile solids content in the six treatments were: T1 (100% SM), T2 (6% A+94% SM), T3 (16% A+84% SM), T4 (43% A+57%SM), T5 (75% A+25% SM), T6 (100% A). Biogas production from the algae only treatment (250 mL CH4/g VSfed) was the lowest compared with all other treatments. The cellulose or hemicellulose structure of the algal cell wall, which is hard to degrade under anaerobic conditions, mostly likely inhibited biogas production. Co-digestion of algae with swine manure improved biogas production. Treatments with up to 16% algae addition resulted in similar biogas yields as swine manure alone (317 mL CH4/g VSfed). Moreover, the addition of 6% algae significantly improved the biogas yield of the swine manure (348 mL CH4/g VS). A case study will be presented for a medium sized confined animal feeding operation (CAFO) showing the potential to increase biogas production and treat wastewater as well as the economic benefits of using this strategy.

 

Bioprospecting for Oleaginous Microalgae and/or Cyanobacteria From Wastewater Holding Tanks – Devin Alvarez, Lowell Collins, Ashvini Chauhan, Florida A&M University

 

Biofuel generation coupled with wastewater remediation has been proposed as a viable, environmentally sustainable technology. We used Fluorescent Automatic Cell Sorting (FACS) as a high throughput method to isolate native algal cells from secondary treated wastewater holding tanks. Two sample preparation methods were employed to concentrate the native algal biomass; a) centrifugation (sample 1) and enrichment in Chu10 or BG11 media (sample 2). Prior to FACS, both sample 1 and sample 2 were stained with 1µM of BODIPY 505/515, a microalgal cell lipid fluorescence enhancement method. FACS was run on a BD FACSAria machine using all possible combinations of excitation lasers and filters, and those that showed the highest resolution between bands were chosen for sorting. We isolated approximately 83 fluorescent strains from 768 wells sorted from sample 1. Most of the isolates were characteristic of the green pigmentation shown by microalgae but we also found some with brown and golden pigmentation. From the enriched sample, 82 cultures were isolated from 4800 wells sorted possessing brown, yellow, gold or red pigmentation but no green colored cells were found; this likely occurred because the enrichments permitted for the green algae to be outcompeted by brown algae. The isolates produced from samples 1 and 2 are being analyzed by Automated Ribosomal Intergenic Spacer Analysis (ARISA) and/or Restriction Fragment Length Polymorphism (RFLP) using the 18S gene and/or the internal transcribed spacer region (ITS1-5.8S-ITS2) genes to determine purity and diversity of the isolated strains. In addition, we are also comparing the lipid production abilities of the isolated strains and correlate their ability to sequester wastewater nutrient

 

Wastewater Nutrient Sequestration and Production of Lipid-biofuels from a Newly Isolated Cyanothece sp. strain SGAC1 – Lowell Collins, Devin Alvarez, Ashvini Chauhan, Florida A&M University

 

The production of value added products from microalgae on the commercial scale is generally successful, but large scale outdoor production is restricted mainly because of fluctuating temperature. Larger scale systems have yet to become economically feasible and the obstacle of seasonal or diurnal temperature fluctuation is an industry barrier. Growth of an isolate throughout the annual cycle is a prerequisite of commercial biomass production. In investigating this, a local Cyanobacteria sp. was isolated from wastewater holding ponds in Tallahassee, FL. Cyanobacteria represent a widespread group of photosynthetic prokaryotes serving not only as primary producers in aquatic environments but also contributing significantly to carbon sequestration, O2 production and nitrogen cycle. Efficient photosynthetic capability, faster growth rates, and ease in genetic modifications are some of the major advantages of cyanobacteria relative to microalgae for the production of next-generation biofuels. Using 16S rRNA gene taxonomy, strain SGAC1 was found to be 85% similar to Cyanothece sp. strain PCC8802, which was isolated from rice fields in Taiwan. Our ongoing studies are demonstrating seasonal durability of the newly isolated Cyanothece strain SGAC1 in a range of temperatures that are being correlated to the production of lipids and nutrient sequestration efficiency for obtaining environmentally sustainable algal technologies specifically customized for growth at North-Florida facilities.

 

 

A Kinetic Model for Microalgae Growth in Wastewater – Eunyoung Lee & Qiong Zhang, University of South Florida

 

Microalgae have received much attention as a potential energy resource because they contain 250 times more oil per pound of biomass compared to other energy crops, such as soybeans (Hossain et al., 2008). In addition, microalgae do not compete for arable land since they are cultivated in ponds or photobioreactors (Rosch et al., 2012). Despite these benefits, life cycle assessment studies have shown that microalgae biofuel has higher environmental impacts than first generation biofuels due to the nutrient requirements for microalgae cultivation (Clarens et al., 2010). Thus, sustainable microalgae biofuel production system will need to integrate with wastewater as nutrient resources (Guest et al, 2013). A key obstacle of this integration is a lack of understanding of microalgae growth in wastewater which is necessary to improve microalgae productivity. Therefore, the goal of the overall study is to develop a new kinetic model of microalgae growth using wastewater as nutrient resources. The framework of the model was based on the combination of threshold and multiplicative theories. In the model, nitrogen, dissolved carbon dioxide concentrations, and light intensity were selected as major growth factors. The current study and results presented focused on the determination of a rate expression for nitrogen based on existing models.

 

In this study, Chlorella sp., collected from Howard F. Curren Advanced Wastewater Treatment Plant in Tampa, Florida was used and performed in batch photobioreactors (1L) for 7 days. Synthetic wastewater with a similar composition to centrate from anaerobically digested swine manure was used for the cultivation. The experiment was conducted at a controlled temperature (22±1°C). During the experiment, 5% CO2-air mixture was injected through a fine bubble diffuser in the reactors (with the flow rate 400ml/min). The reactors were illuminated by 13W and 20W fluorescent lamps (24:0 h light-dark cycles) to provide the desired light intensity (5000lux).

Microalgal biomass concentrations were measured with time for different initial concentrations of nitrogen (0-308ml/L) with/without organic carbon in synthetic wastewater. The Haldane–Andrews model was found to fit best to the experimental data. Kinetic parameters of the Haldane–Andrews models were determined by fitting the experimental data to the relationship between specific growth rate (μ) and initial nitrogen concentration obtained from the growth curves. The parameters for microalgae growing in the wastewater (without organic carbon) were μmax = 2.32 d-1, Ks=140 mg/L as N, and Ki= 25 mg/L as N (R2=0.8014), while the parameters in the wastewater containing organic carbon were μmax = 17.12 d-1, Ks=229 mg/L as N, and Ki= 12.9 mg/L as N (R2=0.7694). The results showed that the μmax and Ks values in wastewater containing organic carbon were high because the organic carbon is readily bioavailable so that it stimulates the microalgae growth (Liang et al., 2009; Ogawa & Aiba, 1981). It indicated that the Haldane-Andrews model can describe the growth kinetic in terms of N with inhibition of NH3. Thus, the Haldane-Andrew model is an appropriate rate expression for nitrogen in the new model.

 

Indigenous Algal Growth on Municipal Sludge Centrate and a Simple Irradiance-based Model for Predicting Biomass Production in the System – Trina Halfhide, Kofi Dalrymple, Ann Wilkie, Sarina Ergas, University of South Florida

 

An indigenous algal consortium was cultivated on municipal sludge centrate in a semi-continuous photobioreactor, operated with a mean cell residence time of seven days under natural light conditions. Centrate from dewatering anaerobically digested municipal sludge is of particular concern in wastewater treatment, as it contains high ammonia concentrations, and is often recycled to the head of the plant, reducing efficiency. The research goals included: (1) to enrich an algal consortium capable of growth on sludge centrate, (2) observe and measure biomass productivity, including lipid production, and nutrient removal efficiencies, and (3) apply a simple irradiance-based model to predict biomass production in the photobioreactor. The model was developed from the fundamental Michaelis-Menten photosynthesis-irradiance (PI) response for photosynthetic organisms. A good fit to the experimental data was obtained with the irradiance-based model (R2=0.96), indicating that the system was light. Chlorella sp. was the dominant species (95%) in the consortium. The mean biomass productivity was 5.2 g m-2 d-1. Observed mean removal efficiencies for total nitrogen, total phosphorus, ammonia and chemical oxygen demand were 65, 71.5, 77.5 and 8%, respectively. Lipid production was low, comprising only 10% of total biomass and could be used as a feedstock for anaerobic digestion for methane production.

 

Alternative Sources of Nutrients for Production of Microalgae Biomass – Kassiana Ribeiro dos Santos, Juan C. Ordonez, Florida State University

 

The high cost of production in the cultivation of microalgae in photobioreactors is a barrier to be overcome, therefore is necessary to search to reduce the cost of cultivation. The objective of this work is to compare the growth of the microalge Scenedesmus sp. being cultivated in CHU medium and in an alternative medium composed mainly of fertilizer. The research approach consisted on growing the microalgae in Erlenmeyer type photobioreactors and producing the growth curves for both media. The comparisons between the two were made based upon three parameters: dry biomass, absorbance, and total lipid quantity. The experiments were made in triplicates in order to quantify the uncertainty in the measurements. The comparison of the cultivation in both media suggests that the modification of the chemical nutrients by fertilizer did not produce significant changes in the number of cells, dry biomass and lipids. In spite of that, the modification resulted in 20% reduction in the growth medium. In this way, the substitution of conventional nutrients by fertilizers, constitute an interesting alternative for the production of biomass from microalgae leading to a cost reduction.

 

Searching for the Lipid Trigger in Biofuel Green Algae – Elton Carvalho Goncalves, Jin Kho, Sixue Chen, Bala Rathinasabapathi, University of Florida

 

Algal lipids as a source of biofuels represent superior alternatives to cellulosic and corn-based ethanol for energy use. Algal storage lipid triacylglycerol (TAG) can readily be converted to high quality fuel via transesterification of TAG, yielding biofuel and glycerol. In our recently published study, we used the green algae Chlorella sp. as a model to investigate storage lipid synthesis and accumulation in response to nitrogen starvation using radiotracer labeling, lipid analyses using mass spectrometry, and ultrastructure. Two of the most striking findings were that Chlorella cells start accumulating TAG as early as 3 hours of nitrogen starvation and that acyl groups from membrane lipids are remodeled into oil bodies during this stress. A special proteomic method called the isobaric tagging for relative and absolute quantitation of proteins (ITRAQ) was used to identify soluble and membrane proteins modulated in the early stages of nitrogen starvation. Out of 1736 soluble proteins identified, 208 were differentially expressed under nitrogen starvation. Several transcription factors were found among the top up-regulated proteins, suggesting possible transcriptional mechanisms controlling this metabolic shift in green algae. Validation of the proteomics data is currently in progress. The mechanism of oil accumulation in response to this stress is still poorly understood and not easily applicable in large-scale production systems. Moreover, such stress condition is not conducive to high growth rates and biomass productivities. Our goal is to reveal the main regulatory steps involved this stress response in order to develop an alternative approach that mimics N starvation, maintaining oil production without compromising culture growth. Therefore, the outcome of this project can be expected to have a direct impact in speeding up the process of making algal biofuels a competitive product in the market.

 

Development of a Production System for Natural Renewable Gas Using Synechococcus sp. BG0011, a Unique Cyanobacterium, as a Feedstock – Bailey E. Trump, Cesar M. Moreira, Edward J. Phlips, Pratap Pullammanappallil, Spyros A. Svoronos, University of Florida

 

Three University of Florida labs are collaborating to develop an innovative new technology for the production of renewable natural gas, by combining a unique strain of cyanobacteria (i.e. blue-green algae) with an anaerobic digester technology. The overall system is designed to address two critical challenges facing the successful application of algal feeds for biofuels production: 1) The availability of species capable of sustained biomass production over a wide range of environmental conditions, and 2) A pathway for converting algal feedstocks to biofuels which avoids costly harvesting and processing procedures. Synechococcus sp. BG0011, the feedstock species, is unique because it is capable of excreting viscous polysaccharides, surviving in hypersaline conditions, and fixing nitrogen. The algal and carbohydrate solution will be fed directly (with or without co-feedstock like manure) into anaerobic digesters for the generation of methane gas. The methane gas will then be converted to electrical power, and some of the byproducts utilized for other value-adding purposes. In order to develop this production system, the ecophysiology of BG0011 will be evaluated, its genome sequenced, its extra-cellular material characterized, and its biochemical potential of digestion will be investigated. The convertibility of BG0011 biomass and polymers to methane has been demonstrated in preliminary experiments at the University of Florida. The proposed system is unique because it diverges from most existing technologies in bypassing one of the most costly aspects of existing approaches; the separation, concentration and conversion of algal biomass into liquid fuels.

 

Comparison of pretreatment methods to enhance methane production from microalgae Nannochloropsis oculata – Pratap Pullammanappallil, Samriddhi Buxy, Robert Diltz, Tushar K. Goswami, Weihua Yang, University of Florida

 

Microalga is an ideal feedstock for biofuel production as it is rich in lipids and carbohydrates. Nannochloropsis oculata (N.oculata), is a spherical autotrophic unicellular microorganism with thick cell wall. Anaerobic digestion eliminates the need of dewatering, extraction or economical separation, which is required in other biofuel production from algae. N.oculata is not rich in lipids but contain predominantly cellulose and other carbohydrates, which makes it a good feedstock for anaerobic digestion. Anaerobic digestion of microalgae faces numerous challenges due to complex structure and thick cell wall of algae cells. One of the main challenges is to breakdown the cell wall. Pretreatment helps in overcoming this obstacle. Different pretreatment studies like acid hydrolysis, sonication, freezing, microwave irradiation etc. done on algae are indicative of resulting cell wall disruption which in turn would improve anaerobic digestibility of algal biomass and enhance the rate and extent of methane production. Biomethane potential of marine microalgae N.oculata was determined in a 5-L batch digestion setup. N.oculata was grown in an open raceway pond at 25ºC, with 1% CO2 and 99% air supplied. N.oculata was grown for 2-3 weeks to final concentration of 600-800 mg/L, and then harvested in a 30-gallon batch by adding base and concentrating algae to 3.15% volatile solids.

 

In the present study, different pretreatment techniques such as, thermal, acid catalyzed thermal, ultrasonication and enzyme hydrolysis were investigated to improve anaerobic digestibility of N.oculata. Biogasification of N.oculata was optimized in terms of duration and intensity of pretreatment. Thermal hydrolysis (at 160ºC for 90 minutes) was done prior to enzyme hydrolysis with and without acid catalyst (2% phosphoric acid). Commercial enzyme (Cellic CTec2, Novozymes)

developed for hydrolysis of lignocellulosic biomass was used in present experiments. The average biomethane potential of untreated N.oculata was 0.225 LCH₄ STP/g VS. The highest methane yield was achieved by thermal treatment without acid addition + enzymatic saccharification (0.5 L CH₄ STP/g VS). Simple thermal treatment of N.oculata (at 160ºC for 90 minutes) followed by anaerobic digestion without an enzymatic saccharification step (0.26 L CH4 STP/g VS) did not show any considerable improvement in methane yield from control. Thermal treatment with addition of acid as catalyst (at 160ºC for 90 minutes) produced 0.39 LCH₄ STP/g VS and ultrasonication pretreatment produced 0.286 LCH₄ STP/g VS. These were 1.7 times and 1.2 times higher methane yield than methane yield from untreated microalgae.

 

N.oculata harvesting rate was 9.64 g VS/m²/d from pilot scale experiments conducted as part of this project. Using this information and the highest methane yield value obtained in this study (0.5 L CH4 STP/g VS), preliminary calculations show that potentially 166 BTU/ m²/d of energy could be

produced from biogasification of N.oculata which is 1.4 times higher than that produced from biogasification of high sugar content terrestrial energy crop like sugarbeet (114 BTU/m²/d).

 

 

SMART-GRID & STORAGE (POSTER SESSION)

Renewable Energy Investment and Operational Decision Model – Alireza Ghalebani, Tapas K Das, University of South Florida

 

Higher level of distributed renewable energy generation and storage (microgrids) will lead to a significant reduction in carbon emission and also reduced cost of electricity in the grid, especially during peak times. Since the renewable green energy generation is still relatively expensive, there are federal, state and utility incentives to increase penetration of distributed renewable energy generation and storage for different regions in the country. In this research, we develop a decision support tool for the consumers to find an optimal level of investment in microgrids and an optimal operational strategy for microgrids participating in a smartgrid. Based on existing incentives, consumer characteristics, price of technologies and the weather forecast, a new Mixed Integer Programming (MIP) model is solved in order to find optimal level of investment in renewable energy generators and storages and their operational strategies to yield a minimum annual cost of energy.

We consider five main categories of incentives such as performance based incentives (PBIs), sales tax incentives, federal tax credit, rebates, and loan programs. PBIs and sales tax incentives are production based compensation. Rebate programs, federal tax credit and loan programs are incentives for installation. The two-level system model for investment and operation that we have developed will also serve as a tool for examining the impact of different incentive and rebate policies and thus serve as a policy design aid at the local, state, and federal government levels. Our “integrated decision support system of design and operation” can be used by households, business sectors or investors to decide the most profitable portfolio of renewable generators and batteries to invest and operate. This decision support tool aims to optimally benefit from the available incentives and tax credits for green energy, and reducing the share of current power supply from fossil fuels thus reducing carbon dioxide emission and increasing social welfare in the long run.

 

Using Electrochemical Impedance Spectroscopy to Study the Reaction Rates and Diffusion Coefficients in Li Batteries – Mohit Mehta, Petru Andrei, Florida State University

 

Over the last 10 years the progress of renewable energy technologies such as wind power and photovoltaics has been remarkable. The global solar power market has grown consistently by 37%/year on an average and wind energy by 21%/year. It is currently being forecast that by 2050 all our energy requirements could be fulfilled by renewable energy sources. The alternative sources are abundant and readily available but they are often not reliable. These sources are localized and often away from main power distribution centers. The electrical energy storage (EES) devices will become an important component for smoothing the intermittency of renewable energy storage and also to act as centralized base power stations. EES devices will not only be important in the power sector as grid storage units but also in the transport sector as fuel for electrical vehicles in the future. Electrochemical energy storage systems have a number of advantages over other electrical energy storage devices, namely they are cleaner, cheaper, faster to build, more responsive, and require less storage space.

 

Li-air electrochemical systems have received a lot of interest in the past few years mainly because of their high energy densities and specific capacities. Recently, we have developed an analytical model for studying the Electrochemical Impedance Spectroscopy (EIS) of Li-air batteries under d.c. discharge, in which the mass transport inside the cathode is limited by oxygen diffusion. The model takes into consideration the effects of double layer, faradaic processes, and oxygen diffusion in the cathode, but neglects the effects of anode, separator, conductivity of the deposit layer, and Li-ion transport. In this workshop we will demonstrate the use of our model to extract information such as the value of the effective oxygen diffusion coefficient and the reaction rate from the impedance spectra. The analytical model predicts that the effects of faradaic impedance can be hidden by the double layer capacitance. Therefore, we will consider two cases: 1) when the faradaic process and the double layer capacitance are separate and can be distinguished as two different semi-circles on the Nyquist plot and 2) when the faradaic process is shadowed by the double layer capacitance and shows up as only one large semi-circle on the Nyquist plot. The diffusion coefficient can be determined by using the resistances (real impedance intercept on the Nyquist plot) of both the semi-circles for the first case and by using the combined resistance for the second case. Once we find the effective oxygen diffusion coefficient, we can use it to estimate the value of the reaction constant. This method of extracting diffusion coefficient and the reaction constant can serve as a tool to study the material properties of the electrolyte. It can also serve as a noninvasive technique to identify and quantify the use of a catalyst to improve the reaction kinetics in the battery.

Experimental Study of Heat Transfer Improvement in Phase Change Materials for Thermal Energy Storage – Abhinav Bhardwaj, Elias Stefanakos, D.Y. Goswami, Clean Energy Research Center, University of South Florida

 

This paper reports an experimental study to determine improvement in heat transfer rates of optically enhanced high temperature phase change materials (PCMs) for thermal energy storage systems. At high temperatures, radiative heat transfer can be a significant part of the total heat transfer. For thermal energy storage at temperatures above 500 degrees C, salts, such as, Sodium Chloride are used as the PCMs which are transparent to infrared (IR) radiation. In these materials the radiant heat transfer can be improved by incorporation of absorptive additives. For this project, as a proof of concept, an experimental method was developed to study the improvement in heat transfer rates using absorbing additives in the PCMs.

The experimental temperature measurements were made with oxidation resistant high temperature thermocouple assemblies at different locations in the sample. The samples were held in ceramic containers and were tested at temperatures around the phase change temperature of the material. This data was used to determine the improvements in heat transfer rates on account of the additives. The paper will describe the improvements in the heat transfer rates in the optically enhanced PCMs.

 

Studying Stress Relaxation at Polymer Interfaces Using FTIR-ATR Spectroscopy – Onyekachi Oparaji, Daniel Hallinan, Florida State University

 

Evolution of the structure of heterogeneous battery electrodes contributes significantly to the fade of battery capacity. Both conventional electrodes and polymer-electrolyte-based electrodes rely on polymer binder to maintain intimate mixing of components. Large volume changes inherent in the charge and discharge of a battery can lead to delamination of the components from the polymer binder rendering those components inaccessible. Therefore, our research focuses on studying the dissipation of stress at polymer interfaces. We use a model block copolymer and a selective solvent to preferentially swell one block. Time-resolved Fourier Transform Infrared – Attenuated Total Reflectance (FTIR-ATR) spectroscopy is then used to measure stress relaxation in the unswollen block. Better understanding of polymer stress relaxation as a function of temperature and the rate at which stress is applied will lead to better understanding of battery fade and to design of longer lasting electrode binders.

 

Designing Composite Polymer Electrolyte Interfaces for Stable Electrodes – Guang Yang, Daniel Hallinan, Florida State University

 

Polymer electrolytes are promising materials for high energy density rechargeable batteries. However, typical polymer electrolytes are not electrochemically stable at the charging voltage of advanced positive electrode materials, which is above 4 V. The initial goal of this project is to understand polymer electrolyte oxidation and design advanced composite electrolytes to prevent such oxidation. The polymer electrolyte used in this study comprises poly(ethylene oxide) (PEO) and lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI). We have chosen an inert metal electrode (gold) to measure PEO + LiTFSI electrochemical stability in the absence of reversible electrochemical reactions. Gold nanoparticles (AuNPs) have been used as probes in a heterogeneous electrode for the following reasons: AuNPs have large surface-to-volume ratio to provide sufficient contact area and signal; they are non-reactive with LiTFSI and PEO; surface modification is facile. The AuNP + PEO + LiTFSI composites are characterized using X-ray Diffraction (XRD) and small angle X-ray diffraction (SAXS). The electrochemical properties of AuNP + PEO + LiTFSI are studied using impedance spectroscopy and cyclic voltammetry. The effect of the AuNP/polymer interface composition on electrode stability will be presented.

 

Optimal Dispatch of Energy Storage Systems in Real-time Digital Simulation – Lingling Fan, Zhixin Miao, University of South Florida

 

In this paper, a high-fidelity microgrid model is developed in OPAL-RT’s RT-lab. The microgrid consists of solar, wind, loads and a battery. The objective of this paper is to investigate the feasibility of a two-level system architecture for this microgrid: The upper level is responsible for system level

optimization while the lower level is responsible for local feedback control. The upper level aims to collect measurements (including power from renewable energy sources, energy storage systems, and load demand), predict the next 24-minute solar/wind generation and load demand, and optimize the battery dispatch for the next 24 minutes. The upper-level control sends the dispatch demand to the battery at every minute. The lower level control responds to the dispatch demand through the controls equipped in the interfacing converters of the battery. The24-minute time-domain dynamic performance of the system is presented in this paper. Real-time simulation-based tests validate the feasibility of the two-level control architecture in microgrids.

SOLAR (POSTER SESSION)

Laser Processing for the Formation of Ohmic Contacts to CdTe Solar Cells-Vasilios Palekis, Prasad Banel, Christos Ferekides, University of South Florida

 

For cadmium telluride (CdTe) solar cells one of the most important and difficult step is the formation of low resistance ohmic contact due to the high work function of CdTe. Surface preparation techniques including wet etches are typically used to produce a p+ surface through the formation of a Te-rich layer, followed by the deposition of a metallic contacting material. In this study laser annealing treatment is investigated in order to replace wet treatments for modifying the CdTe surface prior to contact formation. The laser anneals were carried out using a KrF excimer laser at 248nm with a 25ns pulse. X-Ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study morphological changes on CdTe films laser treated under different incident laser fluences. CdTe surface melting point was observed near 80mJ/cm2 energy density. Current–voltage and spectral response measurements were used to analyze CdS/CdTe solar cells treated with laser annealing. Both open circuit voltage (Voc) and field factor (FF) were improved for laser treated samples versus samples with no laser treatment. The best cell fabricated to-date using all dry laser-based processing resulted in efficiency greater than 13%

Investigation of TiO₂ Annealing and TiCl4 Treatment on the Performance of Dye-Sensitized Solar Cells – Shamara Collins, Arash Takshi, Chris Ferekides, University of South Florida

 

Clean and cost effective electricity has been a long-term goal for governments and researchers around the world. Solar cells convert sunlight directly into electricity without any effluents and can provide a substantial fraction of the world’s electricity needs if they can be produced cost effectively. The solar cell of interest for this investigation is the dye-sensitized solar cell (DSSC). In this type of solar cell, the charge generation occurs in a sensitizing dye by absorption of photons, and it has the potential to be fabricated using low cost manufacturing techniques. A wide band gap semiconductor, titanium dioxide (TiO2) and a sensitizing dye are responsible for charge generation while charge transport takes place using a liquid redox electrolyte. The structure and quality of the TiO2 is crucial for achieving high efficiencies in dye-sensitized solar cells. Therefore, this work investigates ways to improve the TiO2 composition. We have studied the effects of: annealing temperature, titanium tetrachloride (TiCl4) concentration and treatment time, and the number of TiO2 layers on the solar cell’s performance. It is found that increasing the annealing temperature along with the treatment time of TiCl4 at a diluted concentration increases the devices efficiency. These modifications along with the inclusion of a bilayer semiconductor led to a 30% performance increase. Also, the diluted TiCl4 concentration decreases the damaging effects of the acidic solution without limiting the band edge improvement. Lastly, the bi-layer consisted of transparent and opaque TiO2 paste. The first comprises of 15-20nm particles and the latter of ~100nm particles. Each contributes to enhancement, as the dye and sunlight have greater absorption and scattering capabilities respectively within the solar cell.

 

A New Solar Radiation Interpolation Technique- Cristian Cardenas-Lailhacar,Universidad de Investigación de Tecnología Experimental YACHAY, Urcuquí, Ecuador

 

The world dependence on energy, particularly on fossil fuels, is an addiction that is having a
tremendous impact all over the globe. How much is being used, how much is left, and the
consequences of its use are every day questions. A healthy economy certainly relies not only on

the abundance of energy resources, but on their kind, quality, and on how efficiently they are
used. It is clear then that the path to follow should be energy efficiency and the use of
nonconventional renewable energy (NCRE) sources. Solar Energy is one these.
In this paper we show a new mathematical interpolation technique which, by using historical and
current solar radiation (SR) data, for a given period and region, provides a pretty accurate SR
forecast for the next period considered. The algorithm is based on a mathematical expansion
around a minimum of SR in the catchment region of the cycle considered. Future solar radiation
profile values depend on some variables and past radiation. The purpose of this research is to
have an insight into the amount of SR available in a given region, area, surface, etc., and new
expressions and variables for the SR. Among them are the associated force constants, the
maximum SR, when it will occur, etc. The algorithm provides new expressions for current SR
techniques. Preliminary results of the interpolation technique are shown, with encouraging
results.

Cost Effectiveness of Energy Generating Solar Plant Using Sea Water – Sarah Rajkumari Jayasekaran, Essy Tari, Hamid Shoraka, Fazil T Najafi, University of Florida

 

The objective of this study is to determine the marketability of the byproducts obtained from the sea water used for generating electricity. This study will show the economic impact of the production of water, hydrogen and oxygen in our existing solar plants. The other objective is to gain sufficient knowledge about the environmental impact because of the present process, particularly when we use sea water and then dump the brines into the sea which causes imbalance in the marine ecosystem.

The application of this study will render a long term beneficial effect on the environment. The biggest hurdle solar energy faces is that the competing energy sources available are cheaper when compared to solar.

The Technique involved is using electrolysis to break the bond of water to obtain hydrogen and oxygen in the available solar plants which is a promising route for the production of clean, carbon-free renewable fuel in the form of hydrogen gas (H2). Solar Electricity generation and electrolysis cell for hydrogen production will emerge as a potential technology for solar energy production.

During the course of the study we will develop an evaluation system which will foreshow the performance in terms of cost involved in a solar plant by incorporating our ideology. The marketability of the byproducts will help in reducing the cost involved in the operation of the solar plant. Finally the added benefit of the paper is to educate the public on issues related to the importance of solar energy and the methods to make it more cost effective.

 

Functional APCVD Oxide Films for c-Si Solar Cells- Kristopher O. Davis, Kaiyun Jiang, and Winston V. Schoenfeld

 

Atmospheric pressure chemical vapor deposition (APCVD) is a versatile process that offers much promise in enabling significant efficiency gains and cost reductions for crystalline silicon (c-Si) solar cells. In this presentation, we will share recent results on the deposition and subsequent processing of functional oxide films (AlOx, TiO2, SiO2 and doped SiO2) using an in-line, high throughput APCVD system. These oxide films and film stacks can be utilized for doping (e.g. emitter and surface field formation), surface passivation and light management on the front and rear side of c-Si solar cells. Experimental data regarding the microstructure, optical properties and electronic properties of the films will be presented, along with the impact of these films on cell efficiency and other relevant cell parameters. Implications of these results for standard and novel c-Si cell architectures will be covered.

 

 

ENERGY EFFICIENCY (POSTER SESSION)

 

Analysis and Optimization of Combined Flash Binary Cycle for Geothermal Power Generation – Mehdi Zeyghami, Yagi D Goswami, University of South Florida

 

Due to limited supply and negative impacts of burning fossil fuels on environment, utilization of renewable energy resources has attracted more attention over the recent decades. Among renewable power generation systems, geothermal power plants can produce electricity with higher capacity factors. Introducing more efficient technologies and improving existing power generation systems would make geothermal power plants more competitive with conventional fossil fired power plants for base load power supply.

In this project the combined flash-binary geothermal power cycle is analyzed. A computer model has been developed to determine working fluid conditions in different parts of the cycle and performance of the system. One of the main design parameters is the flash separator pressure, which affects the power output of the cycle. Higher separator pressure results lower steam flow and lower power generation in steam cycle and at the same time higher brine temperature in binary cycle and higher power output in this part. Lower separator pressure has the opposite effect and results higher power generation in steam cycle and lower power output in binary cycle. Another important design parameter is the selection of binary working fluid which must be done with respect to brine temperature entering the boiler of the binary cycle. For different brine temperatures, optimum separator pressure and most appropriate working fluid will be presented. Organic working fluids R-22 (as a wet fluid), R-134a (as an isentropic fluid) and R-600 (as a dry fluid) will be considered as secondary working fluid options for each case.

 

Cryogenic Thermal Modeling of Helium Gas-Cooled Superconducting Cable System Components – Nick Suttell, Center for Advanced Power Systems

 

High temperature superconducting (HTS) power cables are being considered for a variety of electric power grid, naval, and aviation applications. A superconducting cable system is usually comprised of two terminations and a superconducting cable in a long cryostat. This study focuses on the modeling of the components for a gaseous helium cooled second generation HTS cable system. The termination cryostats are where the room temperature copper lead interfaces with the superconducting cable at cryogenic temperatures. Excessive temperature gradients in the termination cryostat reduce operating margins of the cables and increase the risks of damage. Therefore, the heat leak from the ambient and by Joule heating generated through current leads must be efficiently intercepted to minimize the heat load in the superconducting cable. The termination cryostat also includes a resistive joint that connects the current lead to the copper terminal of the superconducting cable. The cable system that is modeled in this study is for gaseous helium cooled cables. Significantly lower thermal capacity of gaseous helium compared to liquid nitrogen, typically used as the cryogen for HTS cables, necessitates detailed modeling of thermal and electrical behaviors of each component of the cable system. Optimal designs to minimize the size and weight of superconducting cables and the required cryogenic systems require accurate estimations of heat load from the various components.

A helium gas cooled superconducting cable system has been designed, installed, and being tested at The Florida State University Center for Advanced Power Systems. Thermal map of this system under cryogenic helium circulation has been experimentally obtained with and without the load current through the cable system. However, the detailed heat transfer and thermodynamics of the system have not been modeled. In this study, models for the cable system using COMSOL have been developed in 2D and 3D and the temperature profiles from the model are compared with experimental data. This project is supported by the NEEC (Naval Engineering Education Center) and the Office of Naval Research.

 

Flat Plate Fins Shape Optimization – Julian Osorio, Florida State University

 

In this work, the optimum shapes of flat plate fins of constant thickness are studied in terms of the effectiveness and a set of three Biot (B_i) numbers: B_it, B_iw and √(B_iA ), which characterize the ratio between conduction resistances through every direction and convection resistance at the fin surface. Different fin shapes composed by one (trapezoidal shape), two (rhomboidal shape) and three linear sections were analyzed. It was found that fins with higher effectiveness have shapes far from the convectional rectangular shape. Increments up to 6.0% were reached in fins constituted by three linear sections for B_iw=1- √(B_iA )=2. The effectiveness can be improved by relaxing the shape of the fin, i.e. adding more linear sections. It is expected that the optimal shape will resemble that of a leaf.

 

Modeling and Simulation of a Vapor Compression Refrigeration System – T. K. Nunes, J. C. Ordonez, and J. V. C. Vargas, Florida State University – Center for Advance Power Systems

 

This work introduces a simplified mathematical model of a vapor compression heating and refrigeration system, in order to optimize the system dynamic response. The model applies the mass and energy conservation principles to the components of compression vapor system, i.e., condenser, evaporator, compressor and expansion valve. The model assigns thermodynamic control volumes to each component, therefore uniform properties are assumed within them, which yield a system of ordinary differential equations with respect to time that is integrated explicitly and accurately with low computational time. Appropriate dimensionless groups are identified, and the results are presented in the form of normalized charts for general application to similar systems. As a result it is expected that the proposed model becomes a useful tool for simulation, control, design

and optimization of vapor compression refrigeration system and that the model can
be adapted in anyone HVAC-R system.

 

EDUCATION (POSTER SESSION)

The Development of an Interactive Software as a Secondary Learning Tool for Undergraduate Fuel Cell Courses – Amjad Aman, Yunjun Xu, Nina Orlovskaya, Haiyan Bai, University of Central Florida

 

Fuel cells are increasingly being used as sources of energy in power generation, automotive, and mobile applications, and as auxiliary or backup power units. Along with scientific and engineering progresses, it is also important to train our next generation students in this area. Many universities have fuel cell related courses, but they are taught in the mechanical and/or chemical engineering departments, and those courses are more or less isolated. The purpose of the poster is to talk about the development of an interactive learning tool for undergraduate students to learn about fuel cells in the system perspective. The intended outcome is to provide students with an ”outside of the classroom” approach to learning that would be effective, engaging, highly interactive, and non-threatening. The knowledge they can learn are interconnected from different levels of the fuel cells. Students are anticipated to be attracted to fuel cell systems, and have a better understanding of fuel cell concepts. Student retention through these fuel cell modules can be improved. A customized evaluation method is also under development. The software contents will be presented in terms of modules such that the earlier modules cover the system level fundamentals and applications of fuel cells, while the later modules cover the more detailed science and engineering concepts behind fuel cells. Modules will be interconnected so that students can learn and go in depth with a particular topic without having to complete an entire module before moving on to the next one; the interconnections between modules will be both ascending and descending in terms of the depth of the science and/or engineering understanding. For example, the following materials will be included in the Polymer Electrolyte Membrane Fuel Cell (PEMFC) learning modules: (i) the basic knowledge of a PEMFC system will be covered, (ii) applications of PEMFC in unmanned aerial vehicles (UAVs) will be illustrated including the connections between the fuel cell and the hybrid power system, (iii) understanding of the fuel cell at the sub-system level, (iv) understanding of the fuel cell at the cell and stack levels including different losses and efficiency. The course materials will be presented interactively as text and animations with the incorporation of sounds and video. The software will be connected to a database that would store the participation and progress of each student. The hardware and software requirements of the project are kept to a minimum such that computers with internet connection are sufficient. The intention is that once the software is developed and implemented at the University of Central Florida, it can then be made available to other interested universities.

 

POLICY (POSTER SESSION)

 

Key Factors Influencing Energy Intensity in Developed and Emerging Countries – Priscila Delfino, University of Florida -Public Utility Research Center

 

This project evaluates and compares how certain key factors (GDP explanatory variables) influenced and changed the energy intensity of different countries over a 30-year period. This study will

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