Ultra-High Efficiency Photovoltaic Cells for Large Scale Solar Power Generation

The primary targets of our project are to drastically improve the photovoltaic conversion efficiency and to develop new energy storage and delivery technologies. Our approach to obtain an efficiency over 40% starts from the improvement of III–V multi-junction solar cells by introducing a novel material for each cell realizing an ideal combination of bandgaps and lattice-matching. Further improvement incorporates quantum structures such as stacked quantum wells and quantum dots, which allow higher degree of freedom in the design of the bandgap and the lattice strain. Highly controlled arrangement of either quantum dots or quantum wells permits the coupling of the wavefunctions, and thus forms intermediate bands in the bandgap of a host material, which allows multiple photon absorption theoretically leading to a conversion efficiency exceeding 50%. In addition to such improvements, microfabrication technology for the integrated high-efficiency cells and the development of novel material systems that realizes high efficiency and low cost at the same time are investigated.     

Experimental study of cross-flow wet electrostatic precipitator

This paper reports development and testing of a novel cross-flow wet electrostatic precipitator (WESP), recently patented at Ohio University, that utilizes vertical columns of permeable material in the form of polypropylene ropes placed in a cross-flow configuration within a flue gas stream. The cross-flow design has large surface area, which provides scrubbing action; therefore, it has the potential for removing multiple pollutants, including particulates, gases, vapors, and mists. In this new method, the ropes are kept wet by the liquid (water) introduced from the top of the cells running downward on the ropes by capillary action, making the permeable materials act as the ground electrode for capturing particles from the flue gas. Preliminary testing has shown an efficiency of well above 80% using two cells and three sets of discharge electrodes. Since the material of construction is primarily corrosion-resistant polymeric material, both weight and cost reductions are expected from this new design.

Implications: The newly invented cross-flow WESP exhibit particulate collection efficiency of well above 80% when introduced in particulate-laden exhaust flow. This value was obtained using a two cells and three discharge electrodes configuration. The electric field strength has a substantial effect on the collection efficiency. Also, the pressure drop test results indicate that there is a potential to increase the collection area, which, in turn, will increase the collection efficiency further.     

Technological efficiency improvements: beyond the prospects of first-law efficiencies

Efficiency improvements of technology are said to be one of the most important possibilities to satisfy the energy requirements of a growing global population and to mitigate adverse energy-related environmental impacts, such as climate change, at the same time. On the basis of the classical concept of first-law efficiency, however, conventional energy analyses lead to the impression that efficiency improvement potentials are almost exhausted. This paper explains why prevailing energy conversion efficiencies are grossly overestimated when measured in terms of first-law efficiencies. Using a stylised example, we compare the concepts of first-law and second-law efficiency. Our comparison indicates that estimates of current efficiency improvement potentials depend heavily upon the efficiency concept employed. In fact, there still seems to be much scope for efficiency improvements.     

Stability of core/shell quantum dots—role of pH and small organic ligands

The improvement of knowledge about the toxicity and even processability, and stability of quantum dots (QD) requires the understanding of the relationship between the QD binding head group, surface structure, and interligand interaction. The scanned stripping chronopotentiometry and absence of gradients and Nernstian equilibrium stripping techniques were used to determine the concentration of Cd dissolved from a polyacrylate-stabilized CdTe/CdS QD. The effects of various concentrations of small organic ligands such as citric acid, glycine, and histidine and the roles of pH (4.5–8.5) and exposure time (0–48 h) were evaluated. The highest QD dissolution was obtained at the more acidic pH in absence of the ligands (52 %) a result of the CdS shell solubility. At pH 8.5 the largest PAA ability to complex the dissolved Cd leads to a further QD solubility until the equilibrium is reached (24 % of dissolved Cd vs. 4 % at pH 6.0). The citric acid presence resulted in greater QD dissolution, whereas glycine, an amino acid, acts against QD dissolution. Surprisingly, the presence of histidine, an amino acid with an imidazole functional group, leads to the formation of much strong Cd complexes over time, which may be non-labile, inducing variations in the local environment of the QD surface.     

Alternative immunofluorescent labeling of Cryptosporidium parvum in water samples using semiconductor quantum dots

The application of immunofluorescent labeling using quantum dots for detection of inactivated Cryptosporidium parvum oocysts in spiked water samples (reservoir water, treated wastewater effluent, permeate of a membrane bioreactor, and tap water) provided more consistent results compared with the organic fluorophores label. The varying degree of particles present in the different water samples (with turbidity ranging from 0.2 to 6.1 NTU) in nonconcentrated water samples had insignificant interference on the labeled counts (2-sample t-tests, p > 0.236) using the quantum dot label, while the quantum dot label provided an advantage of approximately 50% lower interference in concentrated water samples compared with the organic fluorophores label.     

Synthesis of highly fluorescent and water soluble graphene quantum dots for detection of heavy metal ions in aqueous media

Environmental Science and Pollution Research - Fluorescent graphene quantum dots (GQDs) are nanomaterials which possess unique properties that show great potential in different applications. In...     

Review on fabrication methodologies and its impacts on performance of dye-sensitized solar cells

This review highlights and summarizes the impact of different fabrication processes on the efficiency of dye-sensitized solar cells (DSSCs). Energy conversion efficiency of cell depends upon semiconductor, sensitizer, electrolyte, and counter electrode. Efficiency of DSSCs can be enhanced by properly selecting the optimum significance of various parameters of fabrications process. Major challenges of these solar cells are non-vegetal, noxious, extreme sensitizers. Application of natural dyes in this field plays a significant role. An optimized CdSe-TiO₂ photoanode showed a power conversion efficiency (PCE) of 13.29% and short circuit current density of 15.30 mA cm^?2 for the DSSC. Power conversion efficiency of 3.26% was achieved by using TTO electrode for DSSC device that is ascribed to the improved electrical and optical properties due to doping with Ta element. Absorbance of betalain was shown in the visible range of 530–535 nm for betanin while 450–559 nm for anthocyanin pigment. The natural dyes are economical, readily available, and environmentally friendly. This compilation would be beneficial for researchers working on dye solar cell.

     

Fe (III) supported on resin as effective catalyst for the heterogeneous oxidation of phenol in aqueous solution

FeIII supported on resin as an effective catalyst for oxidation was prepared and applied for the degradation of aqueous phenol. Phenol was selected as a model pollutant and the catalytic oxidation was carried out in a batch reactor using hydrogen peroxide as the oxidant. The influent factors on oxidation, such as catalyst dosage, H2O2 concentration, pH, and phenol concentration were examined by considering both phenol conversion and chemical oxygen demand (COD) removal. The FeIII-resin catalyst possesses a high oxidation activity for phenol degradation in aqueous solution. The experimental results of this study show that almost 100% phenol conversion and over 80% COD removal can be achieved with the FeIII-resin catalyst catalytic oxidation system. A series of prepared resin were investigated for improving the oxidation efficiency. It was found that the reaction temperature and initial pH in solution significantly affected both of phenol conversion and COD removal efficiency. The activity of the catalyst significantly decreased at high pH, which was similar to the Fenton-like reaction mechanism. Results in this study indicate that the FeIII-resin catalytic oxidation process is an efficient method for the treatment of phenolic wastewater.     

Effects of skin and hydraulic fractures on SVE wells

Soil vapor extraction (SVE) systems are intended to cause substantial volumes of air to flow through the subsurface with the purpose of removing volatile contaminants. The effectiveness of SVE can be influenced by any effect that changes the specific gas capacity (discharge as a function of vacuum) of a well. Skins of low permeability material enveloping a well bore are widely recognized to affect the performance of wells used to recover water, natural gas, or petroleum, and skin can also significantly diminish the performance of an SVE well. Skins a few mm thick consisting of material whose gas phase permeability is 0.01 of the formation can reduce the specific gas capacity of an SVE well by factors of 2 to 10 or more. Hydraulic fractures created in the vicinities of shallow wells commonly resemble sand-filled layers shaped like flat-lying disks or gently dipping saucers. The contrast between the gas-phase permeability of the sand in the fracture and that of the formation is particularly important, with significant effects requiring the ratio to be greater than approximately 50. Shallow hydraulic fractures filled with several tenths of m3 of sand in formations that are several orders of magnitude less permeable than that of the enveloping formation should increase specific gas capacity by factors of 10 or more. Field tests of the effects of hydraulic fractures on the performance of SVE were conducted by creating four wells intersecting fractures and a suite of control wells created using conventional methods in silty saprolite. Specific gas capacities ranged over more than an order of magnitude for 10 wells completed within a small area (2 m2) and at the same depth. Specific capacities correlate to the drilling method that was used to create the bore for the well: lowest values occurred in wells drilled with a machine auger, slightly better results were obtained using a Shelby tube, and the best results were obtained from conventional wells bored with a hand auger. Skin factors determined for wells created with a machine auger could be explained by a layer 1 cm thick that has 0.007 times the permeability of the enveloping material, which could readily have been created during the drilling procedure. Specific capacities of wells intersecting hydraulic fractures were 5 to 100 times more than those of conventional wells. The large difference in performance appears to be due in part to the beneficial effects of the fracture, and in part to the detrimental effects of well skin.     

N,P-codoped carbon quantum dots-decorated TiO2 nanowires as nanosized heterojunction photocatalyst with improved photocatalytic performance for methyl blue degradation

Environmental Science and Pollution Research - N,P-doped carbon quantum dots (N,P-CQDs) are deemed as a promising candidate to environmentally friendly materials owing to the inexpensive,...     

Growth and properties of hydrothermally derived crystalline ZnSe quantum dots

Environmental Science and Pollution Research - Chalcogenide nanostructures are the materials with diverse applications. Here, we report rapid hydrothermal synthesis of crystalline ZnSe quantum dots...     

Efficacy of forming biofilms by <Emphasis Type="Italic">Pseudomonas migulae</Emphasis> AN-1 toward in situ bioremediation of aniline-contaminated aquifer by groundwater circulation wells

The formation and activity of aniline-degrading biofilms developed by the psychrotrophic Pseudomonas migulae AN-1 were studied for the in situ remediation of contaminated aquifer using in-well bioreactor of groundwater circulating wells (GCWs). Biofilms grown in mineral salt medium with aniline exhibited tolerance to high concentrations of aniline. In aniline degradation rate, AN-1 biofilms exhibited slight differences compared with planktonic cells. The effectiveness and bio-implication of AN-1 biofilms in GCWs were investigated to treat aniline-contaminated aquifer. The results demonstrate that AN-1 biofilms survived the GCWs treatment process with high aniline-degrading efficiency. This system provides a novel environmentally friendly technology for the in situ bioremediation of low-volatile contaminants.     

三效催化转化器催化剂硫中毒机理

在一种详细的表面反应机理中加入了包含贵金属催化剂与助催化剂的硫中毒基元反应,建立了新的三效催化转化器催化反应机理。利用该机理进行了稳态工况数值模拟,得到了各排气污染物起燃温度与转化效率随尾气中SO2浓度的变化情况。采用灰色关联分析了SO2浓度与各排气组分转化效率的关联度,结果表明,SO2浓度对C3H6与NOx转化效率影响最大。对三效催化转化器的催化剂活性设计具有重要的参考价值,并对其工况设计及优化提供了指导。     

Refinement of the density-modified displacement method for efficient treatment of tetrachloroethene source zones

A novel method to remediate dense nonaqueous phase liquid (DNAPL) source zones that incorporates in situ density conversion of DNAPL via alcohol partitioning followed by displacement with a low interfacial tension (IFT) surfactant flood has been developed. Previous studies demonstrated the ability of the density-modified displacement (DMD) method to recover chlorobenzene (CB) and trichloroethene (TCE) from heterogeneous porous media without downward migration of the dissolved plume or free product. However, the extent of alcohol (n-butanol) partitioning required for in situ density conversion of high-density NAPLs, such as tetrachloroethene (PCE), could limit the utility of the DMD method. Hence, the objective of this study was to compare the efficacy of two n-butanol delivery approaches: an aqueous solution of 6% (wt) n-butanol and a surfactant-stabilized macroemulsion containing 15% (vol) n-butanol in water, to achieve density reduction of PCE-NAPL in two-dimensional (2-D) aquifer cells. Results of liquid-liquid equilibrium studies indicated that density conversion of PCE relative to water occurred at an n-butanol mole fraction of 0.56, equivalent to approximately 5 ml n-butanol per 1 ml of PCE when in equilibrium with an aqueous solution. In 2-D aquifer cell studies, density conversion of PCE was realized using both n-butanol preflood solutions, with effluent NAPL samples exhibiting density reductions ranging from 0.51 to 0.70 g/ml. Although the overall PCE mass recoveries were similar (91% and 93%) regardless of the n-butanol delivery method, the surfactant-stabilized macroemulsion preflood removed approximately 50% of the PCE mass. In addition, only 1.2 pore volumes of the macroemulsion solution were required to achieve in situ density conversion of PCE, compared to 6.4 pore volumes of the 6% (wt) n-butanol solution. These findings demonstrate that use of the DMD method with a surfactant-stabilized macroemulsion containing n-butanol holds promise as an effective source zone remediation technology, allowing for efficient recovery of PCE-DNAPL while mitigating downward migration of the dissolved plume and free product.     

Conditioning of aluminium-based water treatment sludge with Fenton's reagent: effectiveness and optimising study to improve dewaterability

Alternative conditioning of aluminium-based drinking water treatment sludge using Fenton reagent (Fe2+/H2O2) was examined in this study. Focuses were placed on effectiveness and factors to affect such novel application of Fenton process. Experiments have demonstrated that considerable improvement of alum sludge dewaterability evaluated by capillary suction time (CST) can be obtained at the relative low concentrations of Fenton reagent. A Box-Behnken experimental design based on the response surface methodology was applied to evaluate the optimum of the influencing variables, i.e. iron concentration, hydrogen peroxide concentration and pH. The optimal values for Fe2+, H2O2, and pH are 21 mg g(-1)DS(-1)(dry solids), 105 mg g(-1)DS(-1) and 6, respectively, at which the CST reduction efficiency of 48+/-3% can be achieved, this agreed with that predicted by an established polynomial model in this study.     

聚苯乙烯基离子交换纤维去除铅离子的应用研究

聚苯乙烯其离子交换纤维是一种理想的离子交换材料。它的特殊的物理形态决定它对一些有害气体如铅烟、颗粒铅等具有很好的净化作用，铅烟净化效率可达８０％；对水溶液中毒性铅离子去除率可达８６％。该纤维可做为治理毒性铅离子的材料。     

Measurements show that marginal wells are a disproportionate source of methane relative to production

ABSTRACT

Oil and natural gas wells are a prominent source of the greenhouse gas methane (CH₄), but most measurements are from newer, high producing wells. There are nearly 700,000 marginal “stripper” wells in the US, which produce less than 15 barrels of oil equivalent (BOE) d^?1. We made direct measurements of CH₄ and volatile organic carbon (VOC) emissions from marginal oil and gas wells in the Appalachian Basin of southeastern Ohio, all producing < 1 BOE d^?1. Methane and VOC emissions followed a skewed distribution, with many wells having zero or low emissions and a few wells responsible for the majority of emissions. The average CH₄ emission rate from marginal wells was 128 g h^?1 (median: 18 g h^?1; range: 0– 907 g h^?1). Follow-up measurements at five wells indicated high emissions were not episodic. Some wells were emitting all or more of the reported gas produced at each well, or venting gas from wells with no reported gas production. Measurements were made from wellheads only, not tanks, so our estimates may be conservative. Stochastic processes such as maintenance may be the main driver of emissions. Marginal wells are a disproportionate source of CH₄ and VOCs relative to oil and gas production. We estimate that oil and gas wells in this lowest production category emit approximately 11% of total annual CH₄ from oil and gas production in the EPA greenhouse gas inventory, although they produce about 0.2% of oil and 0.4% of gas in the US per year.

Implications: Low producing marginal wells are the most abundant type of oil and gas well in the United States, and a surprising number of them are venting all or more of their reported produced gas to the atmosphere. This makes marginal wells a disproportionate greenhouse gas emissions source compared to their energy return, and a good target for environmental mitigation.     

Characterization of photovoltaic performance of the dye-sensitized solar cell with a novel ruthenium complex having a bisdemethoxycurcumin as a ligand

The first example of a ruthenium sensitizer (TUS-22) having a natural dye, bisdemethoxycurcumin, as a ligand has been synthesized. The dye-sensitized solar cell based on this novel dye showed 5.8% conversion efficiency under AM 1.5 (100 mW/cm(2)) irradiation.     

Dynamic purification of coal ash by a gas-solid fluidized bed

Fluidized bed filtration classified as granular bed filtration is a solution for removing particles from flue gas. Fine particles are captured by colliding with bed material. Binary mixtures including fines exist in the fluidized bed; the situation becomes more complex because the fines increases with time as particles enter continuously. Coal ash was put into the inlet gas of a gas-solid fluidized bed with silica sand and the variations in concentration with time was monitored, to elucidate the dynamic purification of fines by bed material and the interaction therewith. Water was injected into the inlet gas also to study the influence of water content on the removal of particles. Experimental results showed that the particle concentration rapidly increased with time until equilibrium was achieved. The outlet concentrations exceeded the inlet concentration (such that the removal efficiency was negative) at operating time between 26 and 30 min, yielding an efficiency as low as -35%. The removal efficiency increased with the relative humidity from 30% to 70%. The maximum cumulative collection ratios of particles (by mass) were 20%, 22% and 27% at humidities of 30%, 50% and 70%, declining to 7%, 13%, and 19% at the end.     

Means to improve the effect of in situ bioremediation of contaminated soil: an overview of novel approaches

Different aspects of bacterial degradation of organic contaminants in soil, and how to improve the efficiency and reproducibility is discussed in this review. Although bioremediation in principle includes the use of any type of organism in improving the condition of a contaminated site, most commonly bacteria are the degraders and other organisms, such as soil animals or plant roots, play a role in dissemination of bacteria and, indirectly, plasmids between bacteria, and in providing nutrients and co-substrates for the bacteria active in the degradation process. There are a number of different procedures that have been tested more-or-less successfully in attempts to improve reliability, cost efficiency and speed of bioremediation. The methods range from minimal intervention, such as mere monitoring of intrinsic bioremediation, through in situ introduction of nutrients and/or bacterial inocula or improvement of physico-chemical conditions, all the way to excavation followed by on site or ex situ composting in its different varieties. In the past the rule has been that more intervention (leading to higher costs) has been more reliable, but novel ideas are continuously tried out, both as a means to come up with new truly functional applications and also as a line of studies in basic soil microbial ecology. Both approaches generate valuable information needed when predicting outcome of remediation activities, evaluating environmental risks, deciding on cleaning-up approaches, etc. The emphasis of this review is to discuss some of the novel methods for which the value has not been clearly shown, but that in our view merit continued studies and efforts to make them work, separately or in combination.