Renewable Energy Global Innovations features: Polydopamine as a promising candidate for the design of high performance and corrosion-tolerant polymer electrolyte fuel cell electrodes

Significance Statement

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are considered to have potential as clean energy converters for future applications. There are huge cost considerations due to the usage of noble metal Pt which hinders its commercialization. To reduce the amount of Pt loading, Carbon with Pt nanoparticles is used but under harsh conditions in the PEMFC electrode, carbon materials and nanotubes degrade.

Researchers led by Dr. Marc Michel at Luxembourg Institute of Science and Technology used electrode structure made up of polydopamine (PDA) and carbon nanotubes in PEMFCs to enable the electrode to withstand the operating conditions arising in the fuel cell. The study is now published in Journal of Power Sources.

Polydopamine, among other advantages, is quite beneficial due to the presence of catechol and amino groups which leads to strong binding between PDA and Pt precursor. It promotes the conductivity of protons. Carbon nanotubes enhance the contact between the catalyst and the electrolyte as they form interconnected conducting networks. Thus, a structure having carbon nanotubes with Pt nanoparticles and coated with polydopamine was chosen for the research. This structure would save the carbon material from oxidation which occurs under the extreme operating conditions of the system.

The scientists prepared a new electrocatalytic active (Pt/MWNTs-PDA)₅₀ multi layered nanocomposite film with spray deposition which is much faster (100 times) than the conventional layer by layer (LBL) assembly. Two catalysts supports were prepared, one having multiwalled carbon nanotubes with Pt nanoparticles but without polydopamine as a reference, and the other wrapped with PDA. Physical characterisations were carried out using various methods (XPS, SEM, etc.) to realize the specifications for the experiment. The results yielded by the characterization showed the PDA covering of 19 %.

In their adsorption/desorption study of the catalyst in hydrogen and oxygen it was observed that the coating of PDA to the catalyst doesn’t affect the catalytic reactions. By Cyclic Voltammetry, the Electrochemical Charged Surface Area (ECSA) for Pt/MWNTs-PDA was found to be 15.2 m²/g(Pt) and for Pt/MWNTs was 10.3m²/g(Pt) for the first cycle. In subsequent cycles, the ECSA for the former was stable and degraded for the latter.

The polarization curves obtained show that the Pt/MWNTs-PDA has a lower open circuit voltage (OCV) than Pt/MWNTs. It is believed by the scientist that OCV will further decrease if PDA content is increased but it is yet to be experimentally confirmed. The concentration losses, on the other hand, shown by Pt/MWNTs-PDA are at higher current densities than that of Pt/MWNTs where the concentration losses start at an earlier current density of 1200 mA/cm². The concentration loss zones of the former are observed to be unstable at high current densities. The scientists infer that the instability might be due to some change in cathode structure.

The stability of the two catalyst supports were compared by continued cyclic voltammogram test. The conductivity of PDA-MWNTs was shown to be stable even after many cycles of operation as the surface resistance did not change. Also, the integral area of cyclic voltammograms for PDA-MWNTs did not change implying a good electrochemical stability. It was also observed, with the normalized plots, that the MWNTs would tend to corrode, and in comparison, PDA-MWNTs do not tend to corrode easily as they have the ability to decrease the overpotential of oxidation.

The research team was able to show that PDA-MWNTs are resistant to oxidation, and show a higher Pt Utilization of 6051 mW/mg which is three times as high as utilization obtained by MWNTs of the same Pt loading. PDA-MWNTs also show better performance based on the power densities observed. For the first time, they showed that polydopamine protects the electrode from corrosion of carbon.

To learn more about the research (EnergyCell)

 

About The Author

Dr. Marc Michel has a PhD in physical chemistry and physics from the University of Strasbourg (University Louis Pasteur, 2005). After his PhD work, Marc won the prestigious Fulbright fellowship in 2005 allowing him to work as visiting researcher at the University of Michigan in the group of Prof. Nick Kotov (Department of Chemical Engineering, Ann Arbor, USA). Between 2007-2008 he worked as researcher at the Technical University of Darmstadt in Germany (Department of Renewable Energies). Since 2008, Dr Michel works as senior scientist in the Materials Research and Technology Department of Advanced in The Luxembourg Institute of Science and Technology (LIST).

Dr. Michel’s research is focused on nanotechnologies, surface science, physical chemistry and in particular on the design of new architectures for renewable energies (EnergyCell Project funded by the Fond National de la Recherche Luxembourg). Dr. Michel has published more than 35 papers in his field of research.

About The Author

Joffrey Didierjean received his master’s degree in materials science from the École Européenne d’Ingénieurs en Génie des Matériaux (Nancy – France) in 2008. He firstly worked as an expert in surface and interface science at the Centre de Recherche Public Gabriel Lippmann in Luxembourg, where he was in charge of studies and analytical methods development on advanced characterization techniques. Since 2015, Joffrey Didierjean has been working in Dr. Michel’s team as research and technology engineer in the Material Science and Technology Department at the Luxembourg Institute of Science and Technology (LIST).

His field of competence covers surface science, nanomaterials and nanotechnologies and supramolecular assembly for the design of controlled architecture in the frame of renewable energy.

About The Author

Hongtao Long completed his Bachelor’s studies at University of Sciences and technologies of Taiyuan (China) in 2010, then he graduated from University of Lorraine (France) in 2013, and he is doing his Ph.D now at the Luxembourg Institute of Science and Technology (List), He started research on “Design of new generation of high performance electrodes for polymer exchange membrane fuel cells made of polyelectrolytes and nanoparticles complexes” with Professor Marc Michel in 2014.

He is interested in carbon materials, conducting polymer and their energy applications. He published “Polydopamine as a promising candidate for the design of high performance and corrosion-tolerant polymer electrolyte fuel cell electrodes” on Journal of power source in 2015.

About The Author

Doriane Del Frari joined the LIST (ex-CRP Henri Tudor) in 2007. From 2002 to 2005, she prepared her PhD in chemistry in the Laboratoire d’Electrochimie des Matériaux (Metz, France). Her PhD deals with the realization of thermoelectric materials by electrodeposition, for applications related to their properties, which lie mainly in the field of the heat transfer.

From 2006 to 2007, she worked at the Commissariat à l’Energie Atomique (Saclay, France) on an in situ AFM study of localized corrosion of stainless steel. Since 2007, she was in charge of the corrosion characterization of aluzinc samples (TRASU project) and electrochemical characterization domain of the materials unit.

She is currently in charge of electrical and electrochemical characterization at the Central Lab of the MRT department (Luxembourg Institut of Science and Technology).

 

Journal Reference

Hongtao Long³, Doriane Del Frari³, Arnaud Martin³, Joffrey Didierjean³, Vincent Ball^1,2, Marc Michel³, Hicham Ibn El Ahrach³. Polydopamine as a promising candidate for the design of high performance and corrosion-tolerant polymer electrolyte fuel cell electrodes. Journal of Power Sources, pp. 569-577, 2016.

Show Affiliations

¹ Unité INSERM 1121, Faculté de médecine, 11 rue Humann, 67085 Strasbourg Cedex, France

² Université de Strasbourg, Faculté de Chirurgie Dentaire, 8 rue Sainte Elisabeth, 67000 Strasbourg, France

³ Luxembourg Institute of Science and Technology (LIST), Materials and Research Technology (MRT), 5 Avenue des Hauts-Fourneaux, L-4362 Esch/Alzette, Luxembourg

 

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Renewable Energy Global Innovations features: Regional fluid pressure field: key to understanding of renewability and planning of injection in geothermal systems – workflow for its involvement

Significance Statement

Dr. Judit Mádl-Szőnyi and Dr. Szilvia Simon from Department of Physical and Applied Geology at Eötvös Loránd University in Hungary demonstrated hydrodynamic approach based on regional pore pressure evaluation considering Duna-Tisza Interfluve part of the Pannonian Basin, Hungary characterized by overpressured and superimposed gravity-driven flow regimes. The work published in journal, Geothermics, compared the results of evaluation with experiences of thermal water utilization of the region.

Reinjection has been known to be a key factor in course of preliminary phase of thermal water exploration because of sustainability and economic reasons. Its previous understanding on influence of subsurface pore pressure regime is known to be a factor in preliminary resource evaluation and planning. This research emphasized on regional pore pressure regimes as an essential factor in planning, in addition to provide a workflow for its evaluation.

The approach gave the first priori estimation of pressure conditions which does not substitute the detailed evaluation of recharge conditions which later, during the planning phase of geothermal investment.

Fluid pressure conditions of the sedimentary basins described the nature of the preliminary hydrodynamic regions of different parts of the basin. Unconfined basins were characterized by close to hydrostatic pressure conditions representing hydraulic pressure communication flow systems where continuous meteoric water exchange can be supposed while confined sedimentary basins can be characterized hydrodynamically by underpressure or overpressure due to many geological processes such as erosion, deposition, tectonic compression.

When analyzing the potential geothermal reservoirs of the Duna-Tisza Interfluve, its Pre-Neogene basement comprised of brittle flysch, carbonate and metamorphic rocks. Relief variability of the basement is in excess of 3000m as relatively shallow (-500) to (-800)m asl in the west while deep (-2000) or even (-3500)m asl in the east. Algyő and Endrőd aquitards were unproductive ones as they are dissected by faults and structures which disturb their integrity. The Pre-Pannonian and Szolnok aquifers were characterized by limited vertical and horizontal extent. Neogene part of the Great Plain AF is handled as thermal water reservoir for this research and noted by Great Plain AF (N).

Average geothermal gradient of the study area was found to be 4.77⁰C/100m higher than the average Hungarian gradient of 4.5⁰C/100m. Pre-Neogene Aquifer (basement reservoir) and Great Plain Aquifer (N) had 4.83⁰C/100m and 4.24⁰C/100m respectively. However, the Quaternary part of the Great Plain Aquifer displayed elevated value of 6.6⁰C/100m. Geothermal gradients increased from Algyő aquitard to Szolnok aquifer and Endrőd aquitard with 6.41⁰C/100m, 8.31⁰C/100m and 11.1⁰C/100m respectively. The best reservoirs of the Pre-Neogene basement and Great Plain Aquifer (N) were characterized by relatively lower temperature gradients values in study area.

The pressure-elevation profile compiled for the whole study area displayed overpressure below (-1500)m asl. Algyő aquitard and Szolnok aquifer were characterized by normal hydrostatic pressure to slightly overpressure for the former and severely overpressure for the latter with (-2500)m asl respectively. Endrőd aquitard showed hydrostatic pressure at (-2400)m asl as severely overpressure value existed at an elevation of (-2100)m asl. Pre-Pannonian aquifer became overpressure between the range of (-1000)m asl to (-1600)m asl and highest overpressure occurred at (2500)m asl. Pre-Neogene basement aquifer at (-3400)m asl can be characterized by normal to slightly overpressured values at (-2200, -2800, -3500)m asl.

When interpreting flow regimes for an area pressure increment, pressure increment in the Great Plain aquifer varied in range of +/- 0.5MPa for the study area. Great Plain aquifer (N) of the study area is characterized by less than 0.5MPa positive pressure increments independent of the depth, except from some overpressured values in the East.

Evaluation of the local study areas showed negative pressure increments in Great Plain aquifer (N) and the Pre-Neogene basement. Pressure-elevation profile also showed that vertical pressure gradient is less than hydrostatic (ϒ=9.74MPa/Km) between Great Plain AF (Q-N) and basement carbonate reservoirs. The pressure-elevation profiles of local study area 2 (Fülöpjakab at 107m asl) and study area 3 (Kistelek at 88m asl) gave near hydrostatic pressure conditional of 9.55MPa/Km and 9.81MPa/Km. The hydraulic situation in local study area 1 and 2 (Kecskemét and Fülöpjakab) implies such type of favorable reinjection possibilities into the Great Plain Aquifer (N) without energy investment. Field experiences could prove these proposed conditions.

Mádl-Szőnyi and Simon (2016) analysis when applied could also be helpful in aligned planning of drinking water, thermal water and hydrocarbon utilization in a sedimentary basin.

 

About The Author

Szilvia Simon is a geologist, specialized in hydrogeology. She received an MSc in geology from Eötvös Loránd University (ELTE), Hungary and a PhD degree in hydrogeology (Geosciences) from the same university.

She has been working at ELTE since 2007. She is now a senior lecturer and researcher. She works in the framework of József and Erzsébet Tóth Endowed Hydrogeology Chair. She has experiences in teaching and research, too. During her P.hD studies she spent seven months in Mexico City, at the UNAM. She also worked seven months at Flinders University, Adelaide as an invited research fellow.

Her main research interest is in basin hydraulics and the related practical problems (geothermics), groundwater-surface water interaction, investigation of groundwater dependent ecosystems. Her dissertation was focusing on the understanding of the origin of salinization in a deep basin, where the results showed that deep overpressured flow system provides salt for the surface saline phenomena.

In her research activity she works based on the flow system concept. She is a member of the Regional Groudwater Flow Commition of the IAH. 

About The Author

Judit Mádl-Szőnyi is an associate professor of hydrogeology and she is the head of József and Erzsébet Tóth Hydrogeology Chair at Eötvös Loránd University (ELTE), Hungary. She received her Ph.D. in hydrogeology in Budapest. Her research focuses on the evaluation of regional groundwater flow and pressure pattern in drainage basins (siliciclastic and carbonate environments). Besides vulnerability matters, geothermal energy and hydrocarbon migration, manifestations of groundwater flow are her favorite topics.

She has published 24 scientific papers in international journals. Judit Mádl-Szőnyi is the chair of the Regional Groundwater Flow Commission of International Association of Hydrogeologists. 

 Journal Reference

Mádl-Szőnyi, J. Simon, S. Involvement of Preliminary Regional Fluid Pressure Evaluation into the Reconnaissance Geothermal Exploration—Example of an Overpressured and Gravity-Driven Basin. Geothermics, 2016, Volume 60, pp 156-174.

Department of Physical and Applied Geology, Eötvös Loránd University, Budapest, Hungary 1/C Pázmány P. stny., Budapest 1117, Hungary.

 

 

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Renewable Energy Global Innovations features: Stepwise charging and calcination atmosphere effects for iron and nickel substituted lithium manganese oxide positive electrode material

Significance Statement

Tabuchi et al. (2016) optimized cation ratio and calcination atmosphere of iron Fe and nickel Ni substituted lithium manganese oxide (Li₂MnO₃) based on electrochemical properties obtained under application of stepwise charging. The study is published in Journal of Power Sources,

The Fe- and Ni-substituted Li₂MnO₃ (Li_1+x(Fe_yNi_yMn_1-2y)_1-xO₂, 0<x<1/3, y= 0.1, 0.15, 0.2) was prepared using coprecipitation-calcination (0.25mol/batch). The dried precursor after calcination was then calcined at 850⁰C for 3h in air or nitrogen atmosphere after pulverization. To obtain homogeneous precursor, coprecipitation under cooling at -10deg. C and air bubbling processes must be needed. Cell tests started from galvanostatic charging, up to 4.8V under a fixed current density per mass of active material of 40mAg^-1 and afterwards, cells were kept at 4.8V till low current density of 10mAg^-1 (constant current-constant voltage mode) before being discharged at 40mAg^-1 down to 2.0V.

Cell test was conducted at 30⁰C for stepwise charging as it increased gradually from 80mAhg^-1 at 40mAhg^-1 and discharge characteristics under high current densities to 2.0V evaluated from 40 to 2400mAg^-1 after charging up to 4.8V at 40mAg^-1. Discharge behavior at 0 and -20⁰C was collected to 2.0V at a fixed current density of 40mAg^-1 after charging to 4.8V at 30⁰C.

Results showing the effects of charging mode and calcination in electrochemical properties examined at y value=0.15 in the chemical formula showed a brown color when calcined in nitrogen atmosphere and dark brown color when calcined in air. X-ray diffraction patterns show the formulation of Li₂MnO₃-type phase independence of calcination temperature but lattice parameter and transition metal occupancy of both samples were mutually similar. There was also a successful control average oxidation achieved as chemical analysis data revealed that a nominal cation ratio was maintained.

When examining the effect of mode of initial charging, sample of y=0.15 calcined in air and selected as a positive electrode material showed poor electrochemical performance when galvanostatic mode was selected. Initial efficiency and cyclability up to the 20th cycle were only 53% and 79% respectively. Selecting stepwise charging resulted to high initial discharge capacity and energy density with a better cyclability of 97% which showed that stepwise charging mode must be selected for iron and nickel substituted Li₂MnO₃.

Discharge capacity values for the 5th to 24th cycle when selecting stepwise charging mode showed a higher value for sample calcined in nitrogen atmosphere compared to those calcined in air atmosphere when y=0.15. This shows that reduction in average oxidation states of transitional metal ions favors improvement of electrochemical performance of sample calcined in nitrogen atmosphere.

Fifth discharge capacity after the stepwise charging was greater than initial capacity after galvanostatic charging for sample where y value was equal to 0.1 or 0.15 but was almost equal to initial capacity after galvanostatic charging for which y equals 0.2. This result show that degree of improvement of discharge capacity depends on initial charge capacity at Li₂O extraction part above 4.5V.

Sample for which y value equals 0.15 was seen to have a better high-rate performance when compared to others but better low-temperature performance was obtained for sample where y value equals 0.1 which is also attractive as a positive electrode material if change of the discharge curve shape with increasing number of cycles were suppressed.

According to the authors, Li_1+x(Fe_yNi_yMn_1-2y)_1-xO₂ samples (0<x<1/3) for  y equals 0.1 and 0.15 has optimal cation ratios for use as positive electrode materials which differ from previous reports with sample y values of 0.2 or 0.25.

Reference

Tabuchi, M., Kageyama, H., Shibuya, H., Doumae, K., Yuge, R., Tamura, N. Stepwise charging and calcination atmosphere effects for iron and nickel substituted lithium manganese oxide positive electrode material, Journal of Power Sources 313 (2016) 120-127.

Journal Reference

Journal of Power Sources, Volume 313, 1 May 2016, Pages 120–127.

Mitsuharu Tabuchi¹ , Hiroyuki Kageyama¹, Hideka Shibuya², Kyosuke Doumae², Ryota Yuge³, Noriyuki Tamura³

Show Affiliations

1. National Institute of Advanced Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka, 563-8577 Japan
2. Tanaka Chemical Corp., 45-5-10 Shirakata, Fukui, Fukui, 910-3131, Japan
3. NEC Corp., 34 Miyukigaoka, Tsukuba, Ibaraki, 305-8501, Japan

 

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Renewable Energy Global Innovations features: Mild hydrotreatment of the light fraction of fast-pyrolysis oil produced from straw over nickel-based catalysts

Significance Statement

In the last decade hydrotreatment of pyrolysis oils has attracted an increasing attention for the production of fuels and chemicals as alternative to crude oil. One big challenge of this process is to find a catalyst that is active and stable with pyrolysis oils. For this target, alternative catalysts based on nickel were tested in this study, exploring different supports, loadings and eventual promoters: Ni/Al₂O₃, NiCu/Al₂O₃, Ni/SiO₂, Ni/ZrO₂, NiW/AC and Ni/TiO₂. A light phase of a pyrolysis oil, containing mainly water (56.7%), sugar derivatives and low molecular weight compounds was hydrotreated in mild condition (at 250 °C, 8.0 MPa hydrogen at room temperature) in a batch reactor.

Similar activity was recorded for all nickel catalysts, with a slightly higher hydrogen consumption of NiCu/Al₂O₃, promoted probably by spillover effect enhanced by the presence of copper. The main products consisted of an upgraded oil (7-15% yield, water content around 9% ) and an aqueous phase (75-83% yield, water content around 70%).   Ru/C was used as benchmark (wide tested in literature) and it showed higher hydrogen consumption compared to nickel resulting in an upgraded oil with similar oxygen content, but more hydrogenated.  For all experiments the oxygen content decrease from  40% of the feed to 20-26%  of the upgraded,  as a result of hydrodeoxygenation and partitioning of the components into two phases. The majority of the organic components   were recovered in the upgraded oil (carbon recovery around 50%), providing therefore an energy densification in this phase (31±1 MJ/kg). GC-MS and ¹H-NMR were powerful methods to monitor the reactivity of specific molecules and of their functional groups. Generally at 250 °C production of ketones was observed mainly over nickel-based catalysts, while alcohols over Ru/C.

The valorisation of the light phase of the pyrolysis oil was demonstrated possible, obtaining an upgraded oil with lower oxygen content from a non-valuable fraction containing mainly sugar derivatives.  While mild conditions are usually tested to reduce partially the oxygen content in order to produce with a lower hydrogen consumption a substrate that can be compatible and used as co-feed in an existing refinery, further studies should be addressed to hydrodeoxygenation at higher temperature to obtain higher deoxygenation degree.

Journal Reference

Chiara Boscagli¹, Klaus Raffelt¹, Thomas A. Zevaco¹, Wolfgang Olbrich¹,Thomas N. Otto¹, Jörg Sauer¹, Jan-Dierk Grunwaldt^1,2. Mild hydrotreatment of the light fraction of fast-pyrolysis oil produced from straw over nickel-based catalysts. Biomass and Bioenergy, Volume 83, December 2015, Pages 525–538.

Show Affiliations

1. Karlsruhe Institute of Technology, Institute of Catalysis Research and Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
2. Karlsruhe Institute of Technology, Institute for Chemical Technology and Polymer Chemistry, Engesserstr. 20, 76131 Karlsruhe, Germany

 

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Renewable Energy Global Innovations features: Deconstruction of lignin linked p-coumarates, ferulates and xylan by NaOH enhances the enzymatic conversion of glucan

Significance Statement

Sugarcane bagasse serves as source of renewable energy for production of biofuels and chemicals. The conversion process involves combinations of physical pretreatment and thermo-assisted chemical pretreatment, which disrupts the structure of the lignocellulosic complex architecture.

Two most common thermo-assisted chemical pretreatment used are the dilute acid catalyzed and dilute alkali catalyzed treatments. As the former leads to fermentation inhibitors, such as furans and organic acids, which require an additional detoxification step, dilute alkali catalyzed pretreatments, such as thermo-assisted sodium hydroxide pretreatments, dissolve lignin and hemicellulose, leaving only small amounts of inhibitors in hemi-cellulosic residues.

However, little is known on how sodium hydroxide interacts with lignin and to which extent remaining lignin or hemicellulose obtained after pretreatments affects enzymatic hydrolysis of cellulose-rich residues.

Researchers from Wageningen University in The Netherlands studied the effect of sodium hydroxide pretreatments of sugarcane bagasse (SCB) on insoluble remaining lignin structures. SCB pretreatments at different dosages of sodium hydroxide were compared at different temperatures and residence times. The study is published in Bioresource Technology.

Lignin is composed of 4-phenylpropanoid units based on degree of methoxylation of the benzene ring as p-coumaryl alcohol (H-units), coniferyl alcohol (G-units) and sinapyl alcohol (S-units) in which their proportion varies with plant type biomass. A lignin-carbohydrate complex is formed when lignin is interlinked with xylan. The most common linkages found within lignin are β-O-4, β-5, β-β, 5-5 and 5-O-4.

The authors hypothesized that ester linkages between H-units and xylan are cleaved at 4% of NaOH (pH > 8.6), provoking removal of xylan but not lignin and 9% NaOH pretreatments (pH > 10) are hypothesized to cleave β-O-4 linkages resulting in release of non-core lignin phenolics such as ferulates and coumarates.

Hence, alkaline pretreatment was performed on sugarcane bagasse, with varying amount of sodium hydroxide added, temperature and residence time. The samples were neutralized after pretreatment using acetic acid, later centrifuged and separated into a wet residue and supernatant before being analyzed for carbohydrate content and composition and for lignin by pyrolysis GC/MS.

The wet neutralized residues were subjected to enzymatic hydrolysis and the enzyme digests were analyzed for glucose and xylose contents using high-performance anion-exchange chromatography with pulsed amperometric detection.

After alkaline pretreatments of sugarcane bagasse, results show that as pretreatment conditions become more severe, less xylan remained in the residue. During pretreatment the pH became lower for most samples with reasons being that xylan became converted to small organic acids.

The residual xylan recovery correlated well with the enzymatic conversion of glucan to glucose after sodium hydroxide pretreatments. Higher normalized yield of lignin resulted to lower enzymatic conversion of glucan to glucose in the residues, but not as pronounced as the former.

Results from characterization of alkaline treated sugarcane bagasse residues confirmed the authors’ hypothesis. At 4% sodium hydroxide, xylan yields were lower than 70% and ester linkages are known to be cleaved at pH>8.6 correlating to decreased p-coumarate levels while ferulate levels remained constant in residual lignin. At 9% sodium hydroxide pretreatments, both p-coumarates and ferulates levels were lower in the remaining residues than at 0 or 4% sodium hydroxide, from which can be deduced that β-0-4 linkages are cleaved resulting in a release of non-core lignin phenolics such as ferulates and couramates.

This study showed that pretreatments at 4% and 9% of added sodium hydroxide resulted in residues with decreased levels of ester linked p-coumarates and ferulates, respectively.

 

About The Author

The corresponding author, Dr.ir. Mirjam A. Kabel (H-index 21), is having her own group on ‘Lignocellulosic Biochemistry’. This group is part of the Laboratory of Food Chemistry of Wageningen University (The Netherlands), chaired by Prof.dr.ir. Harry Gruppen (H-index 40). The first author, Patricia Murciano Martínez, obtained her PhD-degree of the Laboratory of Food Chemistry in April 2016 with a PhD-thesis entitled ‘Alkaline pretreatments of lignin-rich by-products and their implications for enzymatic degradation.’ Given that plant cell walls are the largest resource for sustainable biomass, it is imperative that we have to deal with the challenge of efficient and economically viable utilization of lignocellulosic plant biomass for a circular economy. In this perspective, Dr. Mirjam Kabels’ research aims at understanding recalcitrance at a molecular level in biological or green plant biomass refining. Dr. Mirjam Kabel has worked in this field since her PhD (2002) and can be seen as a prominent researcher in the exiting field of characterization of plant biomass structures, in particular of xylan and lignin, to study their fate during processes and enzymatic degradation.

Researcher unique identifiers: ORCID ID: http://ift.tt/2i5Er2k 

 

Journal Reference

 

Murciano Martínez, P., Punt, A.M., Kabel, M.A., Gruppen, A.H. Deconstruction of lignin linked p-coumarates, ferulates and xylan by NaOH enhances the enzymatic conversion of glucan, Bioresource Technology 216 (2016) 44-51.

 

Wageningen University, Laboratory of Food Chemistry, Bornse Weilanden 9, 6708 WG Wageningen, The Netherlands.

 

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Renewable Energy Global Innovations features: Optimum Solar Humidification–Dehumidification Desalination for Microgrids and Remote Area Communities

Significance Statement

Solar desalination technology is favorable due to its positive impact on environment but their cost effectiveness remains a major challenge. The two commonly used solar desalination technologies are the photovoltaic reverse osmosis (PV-RO) and solar humidification-dehumidification desalination system. While the latter requires less expertise in installation and maintenance which makes them more suitable for remote regions, unit cost of produced fresh water using PV-RO is currently lower than humidification-dehumidification desalination system.

Abd El-Aziz et al. (2016) presented an optimization of a solar-powered humidification-dehumidification HDH desalination system for remote areas where assumptions were only made on minimal external electric power. The work published in Journal of Solar Energy Engineering provided modifications on previous work, seeking to improve system performance in terms of unit cost of fresh water production. The authors modified model done on previous work by Abd El-Aziz et al. ASME, 2013 addresses problems such as negative effect of condensation performance, limitation of saline  water temperature to 60°C leading to air capacity for water vapor less than 0.153Kg vapor/Kg air and expensive solar tank in solar water heater (SWH).

The modified model addressed the problems discussed above by firstly disconnecting the condenser from inlet water stream to operate on an independent coolant supply with a constant flow rate, solar air heater (SAH) added before the humidifier allows higher outlet air temperatures and higher humidity ratios and lastly, removal of the solar tank.

The authors considered a small-scale desalination plant operating near city of Hurghada in Egypt. Cost factor was assumed to be 55% while plant lifetime was assumed to be 30 years which is a typical value for the type of equipment considered.

Optimization and simulation results for a system with both large and small solar water heater area A_C,W=1000m² and A_C,W=100m² showed that unit cost of produced fresh water relative to previous work was reduced by about 75% for new cost function and by 56% for original cost function which is due to improved humidification and condensation performances. Specific energy consumption E_sp was found to be in the range of 400-550 KWh/m³ depending of the system size which is still within the range reported in the literature (120-550 KWh/m³).

Disconnecting the condenser to utilize a high constant coolant flow rate increased the quantity of distilled water obtained from installed condenser which relates to a reduction in unit cost of production. The smallest system with 7.8m³/day had a unit cost of $1.7/m³ while most energy-efficient system had a unit cost of $5.7/m³ for capacity of 5m³/day. The minimum unit cost of $1.3/m³ was obtained which is 57% lower than reported range of previous systems of $3-7/m³.

For optimum 500m² system, there was enough provision of potable water for a small town of 1000 to 3000 inhabitants and from economic point of view, it could be inferred that the system would have a payback period of 10 years in Hurghada.

Finally, Heuristic gradient projection optimization was much more efficient and required only about 10% of function evaluations required by unconstrained genetic algorithms optimization to converge.

The optimization and improved humidification and condensation performance achieved in this study have shown major cost reduction in production.

  

 

About The Author

Khalid M. Abdelaziz is a young researcher who is currently working on his PhD degree. He works as an assistant lecturer at the department of Mechanical Design and Production, Cairo University. Design Optimization is the main theme of his work, while application to various types of systems/models is his main interest. His current publications are concerned with cost optimization of solar water desalination system models, where a low cost configuration was studied for remote locations. These publications were part of USA/Egypt joint research project.

Currently he is working on the optimization of truss/frame structures using a novel optimization technique which reduces the amount of computational work required. In addition, he is also considering possible improvements to the latest solar desalination system model developed to further reduce the cost of water production and/or realize different implementation market segments. 

About The Author

Karim Hamza got his B.Sc. (1998) in Mechanical Design and Production and M.Sc. (2001) in Mechanical Engineering from Cairo University (Egypt), while also working at a family-owned business (1995-2001) designing steel structures, water tanks and conveyer lines. He then joined the Ph.D. program at the University of Michigan, Ann Arbor, and soon thereafter became an active member in the research community of the ASME Design Automation Conference. His Ph.D. (2008) focused on optimal design of vehicle structures for crashworthiness, but maintained a broader interest in the co-development of process models and optimization approaches. As a post-doc (2009-2012, University of Michigan), he worked on a number of energy sustainability projects including solar hydrogen production and water desalination. In 2012, he became a consultant to Future of Mobility Research Division (FRD) at Toyota Research Institute, North America (TRINA), and later joined their team (2015) as an in-house contractor research scientist. Karim’s research at TRINA-FRD focuses on the societal impacts of next-generation transportation systems including electrified powertrains and automated vehicles. 

About The Author

Mohamed El-Morsi is an associate professor in the Department of Mechanical Engineering at the American University in Cairo, Cairo-Egypt. Dr El-Morsi received his B.Sc. and M.Sc. degrees in Mechanical Engineering from Ain Shams University, Cairo-Egypt. In 2002, he received his Ph.D. from the University of Wisconsin-Madison. In 2007, he was awarded the Chevening Fellowship from the Foreign & Commonwealth Office, UK to study energy efficiency for three months at the Institute of Energy and Sustainable Development, De Montfort University, Leicester, UK. Dr El-Morsi is one of the co-founders of the Solar Energy Development Association in Egypt.  

About The Author

Ashraf Nassef got his B.Sc. (1987) in Mechanical Engineering and M.Sc. (1990) in Mechanical Engineering from Cairo University (Egypt). He then obtained his PhD. from McMaster University, Canada (1996). Between 1995 and 1998 he worked in the University of Windsor (Canada) and later as an assistant professor in Cairo Univ. In 2002 he joined the American University in Cairo where he is currently a professor in the Mechanical Engineering Department. He served also as an adjunct professor in the University of Western Ontario, Canada. He has been active with the community of the ASME Design Automation Conference and acted as the liaison professor for Africa. His research lies in the area of tolerancing, heuristic optimization techniques and structural optimization. 

About The Author

Sayed Metwalli is currently Professor Emeritus of Machine Design and past Chair of Mechanical Design and Production Department at Cairo University, Egypt.  He received his BS (Mech. Eng.) from Cairo University, Egypt (1965).  He earned his MS and PhD (Mech. Eng.) from State University of New York at Buffalo, USA, (1970) and (1973) respectively.  He conducted research and taught at North Carolina State University and at the University of Central Florida, USA and holds a US patent.

His research interest is in design optimization theory, developing algorithms, and CAD/CAM software, with particular emphasis on optimum synthesis of mechanical components and systems including dynamics and controls for multitude of applications.  He has conducted sponsored research with DOD/NRL, UNESCO, IBM-UK, NSF, EPA and the USAID.  His work with various manufacturers successfully implemented CAD and design optimization in their product design and development.  He is an ASME life fellow, fellow ESME, registered consultant, and has been registered PE in Florida.  

About The Author

Kazuhiro Saitou is a Professor with the Department of Mechanical Engineering at the University of Michigan, Ann Arbor, MI, USA. He received the B.Eng. degree in mechanical engineering from the University of Tokyo, Tokyo, Japan, in 1990, and the M.S. and Ph.D. degrees in mechanical engineering from the Massachusetts Institute of Technology, Cambridge, MA, USA, in 1992 and 1996, respectively.

His research interest is computational optimal synthesis of products and systems with applications ranging from automotive and transportation systems to manufacturing and biomedical systems. 

Journal Reference

Khalid M. Abd El-Aziz ¹, Karim Hamza², Mohamed El-Morsi³, Ashraf O. Nassef⁴, Sayed M. Metwalli ¹, Kazuhiro Saitou². Optimum Solar Humidification–Dehumidification Desalination For Microgrids and Remote Area Communities,  Sol. Energy Eng 138(2), 021005 (Feb 01, 2016) (8 pages)

Show Affiliations

1. Department of Mechanical, Design and Production, Cairo University, Cairo 12316, Egypt .
2. Mem. ASME , Department of Mechanical Engineering, University of Michigan, Ann Arbor,  .
3. Mem. ASME, Department of Mechanical Engineering, American University in Cairo, New Cairo 11835, Egypt;Department of Mechanical Engineering, Ain Shams University, Cairo 11566, Egypt .
4. Mem. ASME , Department of Mechanical Engineering, American University in Cairo, New Cairo 11835, Egypt .

 

 

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Renewable Energy Global Innovations features: Energy potential from residual biomass towards meeting the EU renewable energy and climate targets. The Italian case

Significance statement

The paper deals with assessment of the available residual lignocellulosic biomass in the Italian territory for evaluation of the potential of bioenergy for the generation of heat and electricity. The need for this work has been due to Italian energy supply which has always been heavily affected by the imports and other things. Among the total energy utilized, 76 % was imported at a cost of 55.8 billion euros. This has given a clear need for alternate source of energy through biomass by which the overall import or dependency from outside can be reduced. The use of lignocellulosic biomass in this work is due to plenty of availability of it within the country.

Hence in this work, the authors University of Bari Aldo Moro (Drs. Annarita Paiano and Giovanni Lagioia) has devised crop residues. These residues are specified and are subjected to quantitative estimate. This estimate was done by a linear correlation. Then come the production of the crop per year. The authors have also evaluated the reproducibility factor of the resides via production of the crop every year, the harvesting technique. Then the residues assessed are grouped and evaluated to three categories: A main residue, a secondary residue and agro industrial residue. From the standard equations, the mass of main reside, secondary residue and mass of agro industrial residue are identified. Thus the overall mass of the residual lignocellulosic biomass is identified.

From the guidelines of the Italian NREAP, a mandatory target says that 60 % of the total residual biomass to converted for electricity and the remaining 40 % to heat. Thus this calculates to a final energy of 4.57 Mtoe which is only 2.7 % of the gross Italian energy consumption in 2013 (171 Mtoe). Thus it is identified that it could save 2 billion euros per year to the government of Italy.

In addition to the above, the greenhouse gases from the biomass residue will help to share fossil fuels and enhance environmental performance. From the standard techniques from research papers, we calculated from the analysis in this paper upon the emissions of Co2. It was identified that the estimations of the total savings of CHG emissions produced by energy generation (heat + electricity) from the residual biomass is 52 Mt Co2 eq for the entire Italian territory per year.

Thus we can see that residual biomass usage for energy production has reduced the import required by the Italian government from others. In addition it has also reduced the Co2 emissions from the country – thus allowing decarburization of the energy supplied. The challenges towards achieving this are also practically brought out and how it will be helpful in the future of 2020 and 2030 are also illustrated with estimations. The conclusions underline that an appropriate bioenergy policy can help decarbonize the economy, enhance the reliability of the energy supply and additionally it can revitalize rural areas.

     

 

 

Figure 2:  Trends of electricity and cogeneration of bionergy in Italy in the period 2006- 2013 (GWh).

About The Author

Annarita Paiano, a PhD in Commodity Science, technology, innovation and sustainable production, is an Assistant Professor at Department of Economics, Management and Law studies, University of Bari Aldo Moro, Italy.

She is author of approximately 60 scientific papers. The research of Paiano mainly concerns two sectors of the European Research Council: SH3_1 Environment, resources and sustainability and SH3_4 Social and Industrial Ecology. In particular the research topics concern the material and energy flows analysis, the end of life management and the circular economy strategy.

She is an Editorial Board Member of following journal: Low Carbon Economy, International Journal of Managerial Studies and Research, Advances in Energy Research (ERI). An International Journal. Paiano is a Reviewer for many prestigious international journals (Elsevier and Wiley online Library Publisher). 

About The Author

Giovanni Lagioia is a Full Professor in the Department of Economics, Management and Business Law, Commodity Science Section at the University of Bari Aldo Moro, Italy. He teaches commodity science and technology of the production chain. His main interests of research refer to the following topics: studies on circular economy focusing on the relationships between resources, commodity and environmental studies on the material flow analysis and environmental impact of production processes and consumption. Lagioia is an Editorial Board Member of Journal of Management & Enterprise Development (IJMED), International Journal of Sustainable Economy (IJSE).

He is the Director of PhD course on Economics and Management, vice Director of the Department of Economics, Management and Business Law and Dean of Faculty of Economics at Catholic University Our Lady of Good Counsel of Tirana (Albania).

He is a member of the Italian Commodity Science Academy (AISME) of the International Society of Industrial Ecology (ISIE) and International Academy of Commodity Science and Technology (IGWT).  

Journal Reference

Annarita Paiano^,, Giovanni Lagioia. Energy potential from residual biomass towards meeting the EU renewable energy and climate targets. The Italian case. Energy Policy,Volume 91, 2016, Pages 161–173.

Department of Business and Law Studies, University of Bari Aldo Moro, Largo Abbazia Santa Scolastica, 53-70124 Bari Italy

 

 

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Renewable Energy Global Innovations features: Accounting for combustion mode switch dynamics and fuel penalties in drive cycle fuel economy

Significance Statement

In recent article of Nüesch et al. 2016, published in International Journal of Engine Research focused on an engine equipped with the recompression method and establish a methodology that predicts the drive cycle fuel economy that can be achieved whether fuel penalties during mode switches are taken into account.

Reduction of fuel consumption and emissions has been the major concern of gasoline engines which has led to development of advanced combustion engines such as Homogenous charge Compression Ignition (HCCI). This technology offers advantage in increased thermal efficiency and specific ratio, unthrottling at running engine due to lean operation and less emission of NO_x due to low peak cylinder temperatures.

At high loads, autoignition causes very high causes very high pressure rise rates which limits the range of recompression HCCI engines to low and medium loads. In addition to this, regime for HCCI combustion is influenced by fuel efficiency gains over Spark/ignition (SI) operation and constraints imposed by emission requirement which induce further reductions in brake specific fuel consumption (BSFC).

Due to delay in mode switches from SI to recompression HCCI, resulting gas together with dilution leads to a change in mixture composition, autoignition, higher combustion efficiency and reduction of exhaust gas temperature compared to standard SI. Hence net benefit in fuel economy can only be realized in HCCI if additional fuel needs are invested during mode switches and duration of HCCI is long enough.

The authors previously studied the interaction between SI/HCCI multimode engine which showed that catalyst oxygen storage fills up and requires depletion and hence rich operation but its resulting lean-rich mixture showed substantial penalties in fuel economy with barely satisfying tailpipe NO_x emission constraints. Hence, further study on the research is needed in order to achieve fuel economy whether fuel penalties during mode switches are taken into account.

In order to achieve this, SI/HCCI mode switch was applied to a vehicle simulation and measured engine maps to show analysis of combustion mode switches and results for FTP-75, Highway Fuel Economy Test (HWFET) and US06 driving cycles were taken into consideration. The following notations were taken at every step; time step k, engine torque T_e and engine angular velocity ω_e lies inside the feasible boundaries of HCCI combustion and the instance is called Visitation of HCCI operating regime.

In order to ascertain the benefits of advanced combustion mode on instantaneous mode switches, the engine regimes on vehicle simulation shows that frequently visited area during the FTP-75 engine operates at lower loads for a significance amount of time of 21%, fuel 19% and distance of 28% where the low temperature doesn’t allow a mode switch to HCCI operating in the SI mode, HWFET time decreases to 19% while fuel decreased to 12%. For US06 cycle, value drops further for time and fuel at 7% and 3% respectively.

From fuel economy results and assuming instantaneous switches, the improvement in miles per gallon (MPG) due to HCCI lies at 3.4% for FTP-75, 1.3% for HWFET and 0.4% for US06 cycles. Hence, FT-75 and HWFET were only considered since improvement in US06 cycle is marginal. Despite 20% of fuel time spent in HCCI during FTP-75, durations of individual visitation of HCCI regime is very short hence, instantaneous mode switches cannot be assumed and mode switch dynamics need to be considered.

From two mode switch developed i.e. SI-HCCI and HCCI-SI, the dynamics of SI-HCCI direction poses a more difficult combustion control while HCCI-SI is challenged by air path control. HCCI-SI is more preferable due to higher fuel penalties than SI-HCCI direction.

Incorporating the assured fuel penalty of mode switches reduces the gain inefficiency due to HCCI combustion significantly for FTP-75 from 3.4% to 2.7% while HWFET reduced from 1.3% to 1%. From the result it was seen that substantial fraction of mode cycles is harmful and penalty ratio (r_h) is relatively small since harmful mode switch cycles are short. 6.4% and 3.3% of FTP-75 and HWFET respectively was the difference between instantaneous and penalized cases originate from this harmful switches.

Parametric study on the effect of fuel economy improvement showed that at higher penalties, the penalty contribution of harmful switches are responsible for more than 40% of the reduction in fuel economy when compared to cases where instantaneous mode switches are assumed.

This study the researchers were able to show improvement of up to 3.4% which is significantly below other results.

 

Journal Reference

Sandro Nuesch¹ , Patrick Gorzelic¹ , Li Jiang² , Jeff Sterniak² , Anna G Stefanopoulou¹  . Accounting for Combustion Mode switch Dynamics and Fuel Penalties in Drive Cycle Fuel Economy. International Journal of Engine Research, 2016, Volume 17, Issue 4, pp 436-450. 

Show Affiliations

1. Walter E. Lay Automotive Laboratory, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
2. Robert Bosch LLC, Farmington Hills, Ann Arbor, MI, USA

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Renewable Energy Global Innovations features: The identification of structurally sensitive zones subject to failure in a wind turbine blade using nodal displacement based finite element sub-modeling

Significance Statement

To deal with the structural complexity, the wind turbine blades are modeled using finite elements. Vibrations at natural frequencies is an important part of blade designing. Therefore, for the validation of the structural design and the dynamic or modal response of the blades, finite elemental analysis technique was used. The analysis was done with varying degrees of complexity. Hence, the approach used by  Professor Mostapha Tarfaoui and Dr. Owaisur Rahman Shah from ENSTA Bretagne & Institut de Recherche Dupuy de Lôme (France) in their studies, was to model the blade and to define the material. Furthermore, to validate the proposed design they applied a static bending test on the full scale blade. The results from these static tests, using strain gauges, were then used to validate the sub-modeling regime in terms of strains measured at the blade surface.

The researchers considered the sub-models as sections or portions of the larger model. The larger complete model; the parent (as it can be a sub-model of a higher and larger, more complex model) and the child as sub-model. They compared the global model with the experimental results to validate the approach of sub-modeling and then later all the sub-models were validated successively.

Sub-modeling technique reduces the domain size of a finite element model to a more manageable size. From the different methods of sub dividing the problem domain into simpler smaller domains, they used the method of transfer of nodal displacement from one parent model to its child model. The method of nodal displacement was used to predict failure in large structures and to identify the sensitive zones.

Only ‘delamination’ was studied as the criteria for the failure instead of different criteria of failure of plies. They used the criteria of combination of failure as it would be necessary to simulate accurately and appropriately the failure of these structures.

In their experiments, the wind turbine blade was subjected to buckling at its compression side and that too, at its critically loaded section at 7.55m from the root which has produced waviness in the blade’s structure due to which the plies have inter-ply transverse tensile stresses in the stacking direction. So this caused the delamination type failure.

Sub-modeling results corresponded well from the parent level to its child level or sub-level. Therefore, the researchers concluded that the nodal displacement based sub-modeling can be used to locate weak points in a structure under extreme loading conditions. They further validated the global model in strain calculations when compared to full scale physical tests.

Due to the consistent results of sub-models, Shah and Tarfaoui concluded that the finest sub-models are an accurate representation of the failure that would take place eventually.

About The Author

 

Mostapha TARFAOUI is professor specialized in structural mechanics. His main expertise is focused on the composite and Nanocomposite materials behaviour. This includes the experimental and numerical investigation of the static and dynamic responses involved in the shipbuilding structures. He has expertise in Dialogue test/calculation in the heterogeneous structures relationships and numerical modelling. He obtained his Ph.D. of Engineering Science (Faculty of Science, University Haute Alsace, France) in 1999 (dissertation: “Finite element analysis of mechanical behaviour of plain and twill fabrics”) and M.S. Physics and Applications (Faculty of Science, University Haute Alsace, France) in 1993. He has more than 60 papers. He participated in many congresses (CanCOM, HIPER, ICCM, CFM, IMAC, ESMC, CST, JNC…). He is member of Organization committee and Scientific committee of the international Congress. He was chairman and co-chairman of different congress sessions.

Professor TARFAOUI is memberships of AFM (French Association of Mechanics), AMAC (Association for Composite Materials) and AF3M (Association Franco-Maghrebian of Mechanics and Materials). He is reviewer of international scientific journals:  Journal of Composite Materials, Advanced Materials Research, Computational Materials Science, Applied Mechanics and Materials, Journal of Reinforced Plastics and Composites, Mechanics of Advanced Materials and Structures, Mécanique & Industries, Matériaux et Techniques… 

 

Journal Reference

Owaisur Rahman Shah, Mostapha Tarfaoui. The identification of structurally sensitive zones subject to failure in a wind turbine blade using nodal displacement based finite element sub modeling. Renewable Energy, 2016, Volume87, pp 168-181. 

ENSTA Bretagne, MSN/LBMS/DFMS, 2 Rue François Verny, 29806, Brest, CEDEX 9, France

 

 

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Renewable Energy Global Innovations features: Increased short-circuit current density and external quantum efficiency of silicon and dye sensitised solar cells through plasmonic luminescent down-shifting layers

Significance Statement

Luminescent down-shifting is an optical approach to increase photovoltaic device efficiency and it consists of luminescent species such as quantum dots, organic dies and rare-earth complexes doped in a transport polymer sheet and deposited on top of photovoltaic cells.

Spraying of luminescent species on top of photovoltaic cells either by spray coating or incorporation into a multifunctional coating system based on photo-curable fluoropolymer have shown significant improvement in power conversion efficiency of uncoated dye sensitized solar cells devices thereby improving cell stability and prevention of photochemical and physical degradation.

In a recent article by Ahmed et al. (2016) and published in Solar Energy, investigations were made on plasmonic luminescent down-shifting (pLDS) layers applied to silicon cells (c-Si) and dye sensitized solar cells (DSSC) solar cells.

Quantum dots exhibits broad absorption spectra, high absorption coefficients and emission wavelength which can be tuned according to their size as a result of quantum confinement having advantages over organic dies due to their higher brightness and stability. However, the luminescent down-shifting suffer from self-absorption; a case where downshifted photons are reabsorbed by quantum dots or dye within the downshifting layer. Optical properties of luminescent species according to research were shown to exhibit dramatic emission enhancement in presence of metal nanoparticles on quantum dots ion dye emitters.

For the experiments, core-shell type Cadmium Selenide/Zinc Sulfide (CdSe/ZnS) quantum dots were used as fluorescent material which has a quantum yield of 0.7±0.07 measured in solution. Silver nanoparticles were used in plasmonic luminescent down-shifting composite layer and preparation of fluorescent species with silver nanoparticles composite layers followed.

The performance of c-Si and DSSC solar cells encapsulated with quantum dots luminescent down-shifting layer and plasmonic-quantum dots luminescent down-shifting composite layer was compared.

Absorption and emission measurement of quantum dots with/without silver nanoparticles revealed significant increase in emission for the plasmonic luminescent down-shifting layer when compared to layer with no silver nanoparticles. This result shows enhancement attributed to silver nanoparticles exhibiting strong scattering of incident light which greatly enhances local electric fields at surface plasmon resonance frequency.

Current-voltage curves for c-Si and DSSC solar cells showed electrical characterization increase of 1.92% in current density due to presence of quantum dots when compared to bare c-Si cells. Enhancement of 7.84% was calculated for plasmonic-quantum dots luminescent down shifting composite layer. There was also 5.81% increase in current density for plasmonic-quantum dots luminescent down shifting composite layer when compared with quantum dots luminescent down shifting layer.

Electrical characterization of DSSC solar cells showed a decrease of 8.03% in current density of quantum dots luminescent down shifting when compared to bare DSSC solar cells while enhancement of 3.31% was calculated for plasmonic-quantum dots luminescent down-shifting composite layer. There was also 11.29% increase in current density for plasmonic-quantum dots luminescent down shifting composite layer when compared with quantum dots luminescent down shifting layer.

External quantum efficiency of bare c-Si solar cells was poor reaching only 11% at wavelength below 400nm. Improvement of external quantum efficiency at the same wavelength for quantum dots luminescent down-shifting layer and plasmonic-quantum dots luminescent down-shifting layer were 23% and 52%, respectively. The high improvement in plasmonic-quantum dots luminescent down-shifting layer can be attributed to presence of silver nanoparticles in its composite layer.

The external quantum efficiency of DSSC solar cells had overall decrease between 300-800 nm for quantum dots luminescent downshifting layer. However, plasmonic-quantum dots composite layer show 3.03% increase when compared to DSSC bare solar cell and 11.71% when compared to quantum dots luminescent down-shifting device. Significant increase was calculated between 300 and 500nm where current density J_sc reached 21.64% and 5.16% for plasmonic-quantum dots composite layers compared to bare DSSC solar cell and quantum dots luminescent down-shifting device, respectively.

 CdSe/ZnS quantum dots investigations in Ahmed et al. (2016) studies has the ability to absorb light below 465nm and emits at 500nm flows shifting the optical wavelength of the cell from poor optical response (short wavelengths) to external quantum efficiency (at longer wavelengths).

The research team for the first time demonstrated plasmonic luminescent down-shifting current density J_sc reaching up to 22% increase in region of 300-500nm for c-Si and DSSC solar cells.

About The Author

Dr. Hind Ahmed is a graduate of the prestigious Graduate Studies Program at the Singularity University, NASA AMES, California, USA. She has a strong background in Mathematics, Physics and Engineering with the focus in the area of solar energy research. She holds an Honour’s degree in Physics, a Postgraduate Diploma in Mathematical Sciences, a Master degree in Material Physics, a Professional Master in Micro/Nano Electromechanical System and a PhD in Physics.

She is currently working as post-doctoral researcher in the Solar Energy Applications group in Trinity College Dublin under ERC Starter grant (PEDAL) which involves the design, development, characterization and fabrication of large scale plasmonic luminescent down shifting devices for enhancing the efficiency of solar cells. 

About The Author

Dr. John Doran

Affiliation: School of Physics, Dublin Institute of Technology (DIT), Ireland

Professional Appointments:

Head of School, School of Physics, DIT: 2009-present

Assistant Head of School, School of Physics, DIT: 2003 – 2009

Lecturer, School of Physics, DIT: 1996 – 2003

Postdoctoral Research Fellow, School of Physics, TCD, 1994 – 1996.

Education: BA(Mod) Experimental Physics, 1989, Trinity College Dublin

PhD, 1994, Trinity College Dublin – Thesis Title: Exciton Dynamics in CdZnTe/ZnTe Multiple Quantum Wells.

Research and Professional Experience:

Solar Energy Group within the Dublin Energy Lab. Research involves two aspects: 1. Design, fabrication, optical and electrical characterisation, and modelling of Luminescent Solar Concentrators (LSCs) and Luminescent Downshifting (LDS) devices incorporating plasmonic effects.

Applications of switchable mirror technology to solar energy. Recent research has focused on the novel incorporation of metal nanoparticles into LSC and LDS devices in order to enhance optical emission and overcome losses inherent in these devices. This novel plasmonic approach has been demonstrated experimentally and device performance has been modelled successfully using a ray-tracing approach. 

About The Author

Dr Sarah McCormack is an Associate Professor and lead PI in the Solar Energy Applications group in Trinity College Dublin. She has been working in the area of solar energy research for over 15 years. She has published over 90 publications in the areas of solar energy and energy storage and has over 1000 citations. She has supervised 11 PhD students to completion and is currently supervising a further 6 along with 4 Post doctoral researchers. She has been awarded funding of over 3M in national and EU funded projects. She is the Irish representative on European PV Technology Platform Mirror Group nominated by the Sustainable Energy Authority of Ireland, a member of the Renewable Heating and Cooling Platform, Secretary of the Solar Energy Society of Ireland. Recently she has been awarded a prestigious ERC Starter grant (PEDAL) to continue her work in LS devices for enhancing the efficiency of solar cells. 

Journal Reference

Ahmed H¹, Doran J², McCormack S¹. Increased Short-Circuit Current Density and External Quantum Efficiency of Silicon and Dye-Sensitized Solar Cells through Plasmonic Luminescent Down-Shifting Layers.  Solar Energy, Volume 126, 2016, Pages 146–155.

Show Affiliations

1. School of Engineering, Trinity College Dublin, Dublin, Ireland
2. Dublin Energy Lab, Dublin Institute of Technology, Dublin, Ireland

 

 

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Renewable Energy Global Innovations features: Floating offshore wind turbines: designing against the forces of nature

Significance Statement

Studies done before on a small scale floating horizontal axis wind turbine in surge motion showed thatthere is an increasing amplitude of the cyclic thrust and power generation against tip speed ratio. A numerical study using an Actuator Disk (AD) Navier Strokes model, a Blade Element Momentum (BEM) model and a Generalized Dynamic Wake (GDW) model was performed in order to determine the previous observations on the full-scale NREL 5MW reference rotor in surge motion. The research question was to understand the reason why such high variations in thrust and torque occur at non-optimal tip speed ratios. The research was done to improve the understanding of the fundamental science governing floating offshore machines so as to make them commercially viable in the future.

The test was performed by maintaining the surge amplitude and surge frequency fixed and changing the tip speed ratio. Full details of the AD model can be found in the full paper. Results are then compared with BEM combined with dynamic inflow engineering models as well as the GDW model.

When the operating tip speed is increased the released vorticity in the wake becomes stronger causing an increase in the amplitude variations of the flow inductions in the axial, radial and swirl directions. The extent of the radial expansion and contraction of the wake was found to increase with increasing tip speed ratio. The study makes us conclude that the dynamic wake model can be adopted for BEM modeling of a surging rotor but only if mean quantities are of interest. The GDW model on the other hand gives quite an acceptable agreement with what the AD model.

Their work give credit to the previous experiments conducted on a small model rotor. They produce similar results that thrust and power amplitudes vary with wave amplitude and frequency. The unsteady variations in thrust and power are clearly observedto increase at higher tip speed ratios related to turbulent wake condition. This affects the structural and electrical design of the commercial turbines to manage fatigue when the turbine is operated in its rated conditions. The power will have to be tapped by suitable electronics that can handle the strength and instability from the turbine. The study recommends that it is ideal to operate at low speed tip ratios to reduce the fatigue loads on the blades, especially where the power demands are not very high. Concludingly, the results from this quantitative study were compared to the FAST code results using both BEM and unsteady GDW models.. Some difference was found at high tip speed ratio towards the onset of the turbulent wake state. The results for low tip speed ratios agreed quite well. The study was however limited due to the fact that the rotor was tested under fixed surge conditions and varying tip speed ratios. 

 

About The Author

Dr. Daniel Micallef is an academic at the University of Malta where he joined the Environmental Design department of the Faculty for the Built Environment in September 2014.

Dr. Micallef graduated in Mechanical Engineering from the University of Malta in 2008 with first class honours. He started his professional career in the public sector with the Malta Resources Authority as an energy analyst. During this time he started pursuing a career in academia. He read for a joint PhD with the Delft University of Technology in the Netherlands (where he formed part of the DUWIND wind energy research group) and the University of Malta.

His research focused on furthering the understanding of wind turbine flow phenomena close to the tip. He was awarded his PhD in 2012. During the final year of his PhD, Dr. Micallef also worked as a project officer at the Mechanical Engineering Department of the University of Malta where he developed analysis tools and contributed in the design of an urban wind turbine being developed by industry. His research career took a twist in 2012 were he continued his research experience as a post-doctoral researcher on the HILDA FP7 project. While continuing to publish his work in wind energy, his post-doc research focused on a different topic – modelling of friction stir welding of steels.

He developed finite element and computational fluid dynamics models for the numerical analysis of the process. During his final months on the project, he was engaged as a lecturer at the Malta College of Arts Science and Technology (MCAST). His experience as a post-doc researcher and MCAST lecturer ended in September 2014.

Dr. Micallef published in high quality peer reviewed journals and conferences worldwide. His current major interests are in the fields of wind energy, wind engineering and building physics. Apart from his research activities, he lectures in undergraduate and Masters courses. Dr. Micallef is currently the secretary general of the Chamber of Engineers (an NGO). He is also the COST (Cooperation in Science and Technology) representative of Malta in two COST actions.  

Journal Reference

Daniel Micallef¹, Tonio Sant². Loading effects on floating offshore horizontal axis wind turbines in surge motion.  Renewable Energy, Volume 83, November 2015, Pages 737–748.

Show Affiliations

1. Department of Environmental Design, Faculty for the Built Environment, University of Malta, Malta
2. Department of Mechanical Engineering, Faculty of Engineering, University of Malta, Malta

 

 

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Renewable Energy Global Innovations features: An assessment model for energy efficiency program planning in electric utilities: Case of Northwest U.S.

Significance Statement

Energy efficiency stands out with its potential to address a number of challenges that today’s electric utilities face, including increasing and changing electricity demand, shrinking operating capacity, and decreasing system reliability and flexibility. Being the least cost and least risky alternative, the share of energy efficiency programs in utilities’ energy portfolios has been on the rise since the 1980s, and their increasing importance is expected to continue in the future. Despite holding great promise, the ability to determine and invest in only the most promising program alternatives plays a key role in the successful use of energy efficiency as a utility-wide resource. This issue becomes even more significant considering the availability of a vast number of potential energy efficiency programs, the rapidly changing business environment, and the existence of multiple stakeholders.

This paper introduces a hierarchical decision modeling framework for energy efficiency program planning in electric utilities. The framework focuses on the assessment of emerging energy efficiency programs and proposes to bridge the gap between technology screening and cost/benefit evaluation practices. This approach is expected to identify emerging technology alternatives which have the highest potential to pass cost/benefit ratio testing procedures and contribute to the effectiveness of decision practices in energy efficiency program planning. The framework also incorporates rank order analysis and sensitivity analysis for testing the robustness of results from different stakeholder perspectives and future uncertainties in an attempt to enable more informed decision-making practices. An assessment framework was applied to the case of 13 high priority emerging energy efficiency program alternatives identified in the Pacific Northwest, U.S.A.

The results of this study reveal that energy savings potential (35.6%) is the most important program management consideration in selecting emerging energy efficiency programs. Market dissemination potential (25.7%) and program development and implementation potential (24.6%) are the second and third most important, whereas ancillary benefits potential (14.1%) is the least important program management consideration. The results imply that program value considerations (49.7%), comprised of energy savings potential and ancillary benefits potential; and program feasibility considerations (51.3%), comprised of program development and implementation potential and market dissemination potential, have almost equal impacts on assessment of emerging energy efficiency programs. Considering the overwhelming number of value-focused studies and the few feasibility-focused studies in the literature, this finding clearly shows that feasibility-focused studies are greatly understudied.

The hierarchical decision model developed in this paper is generalizable. Thus, other utilities or power systems can adopt the research steps employed in this study as guidelines and conduct similar assessment studies on emerging energy efficiency programs of their interest. 

About The Author

Dr. Ibrahim Iskin is a senior software engineer at Zuliliy corporation in Seattle Washington USA. His research focus is on data science specifically machine learning and big data. Prior to that he worked at XPO Logistics and Bonneville Power Administration. He has a BS in Industrial Engineering from Istanbul Technical University, MS in Engineering Management and PhD in Technology Management from Portland State University. 

About The Author

Tugrul Daim is a Professor and PhD Program Director in the Department of Engineering and Technology Management at Portland State University. Prior to joining PSU, he had worked at Intel Corporation for over a decade in varying management roles. At Intel he managed product and technology development. He also has several professional certifications including New Product Development Professional and Project Management Professional.

Professor Daim has been consulting to several organizations in sectors ranging from energy to medical device manufacturing. He has been helping organizations including US Dept of Energy, Energy Trust of Oregon, Biotronik, Biopro, Elsevier and many others to develop technology roadmaps for their future investments. He is also a visiting professor with the Northern Institute of Technology at Technical University of Hamburg, Harburg where he teaches similar short courses.

He has been recently appointed as Extraordinary Professor at the Graduate School of Technology Management at University of Pretoria in South Africa. He is frequently invited to give lectures to many multinational companies including IBM, Xerox and HP as well as universities  around the world including his recent visits to Finland, Japan and Germany. He has published over 200 refereed papers in journals and conference proceedings. His papers appeared in Technological Forecasting and Social Change, Technovation, Technology Analysis and Strategic Management, Computers and Industrial Engineering, Journal of Medical Systems, Energy, Energy Policy and many others. He has coauthored four books of readings and several proceedings.

He is the Editor-in-Chief of International Journal of Innovation and Technology Management and North American Editor of Technological Forecasting and Social Change. He received his BS in Mechanical Engineering from Bogazici University in Turkey, MS in Mechanical Engineering from Lehigh University in Pennsylvania, MS in Engineering Management from Portland State University, and PhD in Systems Science: Engineering Management from Portland State University in Portland Oregon. 

 

Journal Reference

Ibrahim Iskin, Tugrul U. Daim. An assessment model for energy efficiency program planning in electric utilities: Case of Northwest U.S. Sustainable Energy Technologies and Assessments, Volume 15, 2016, Pages 42–59.

Portland State University, Department of Engineering and Technology Management, Portland, OR 97207, United States.

 

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