Documents published in Scipedia

• MoS2 as a co-catalyst for photocatalytic hydrogen production from water

  B. Han, Y. Hu

  Energy Science & Engineering (2017).

  
  

  Abstract

  Solar-to-hydrogen conversion based on photocatalytic water splitting is a promising pathway for sustainable hydrogen production. The photocatalytic process requires highly active, inexpensive, and earth-abundant materials as photocatalysts. As a presentative layer-structured transition metal dichalcogenides, molybdenum disulfide (MoS2) is attracting intensive attention due to its unique electro and photo properties. In this article, we comprehensively review the recent research efforts of exploring MoS2 as a co-catalyst for photocatalytic hydrogen production from water, with emphasis on its combination with CdS, CdSe, graphene, carbon nitride, TiO2, and others. It is shown that MoS2–semiconductor composites are promising photocatalysts for hydrogen evolution from water under visible light irradiation.

  Abstract
  Solar-to-hydrogen conversion based on photocatalytic water splitting is a promising pathway for sustainable hydrogen production. The photocatalytic process requires highly [...]

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• Fe-Cu metastable material as a mesoporous layer for dye-sensitized solar cells

  A. Alami, J. Abed, M. Almheiri, A. Alketbi, C. Aokal

  Energy Science & Engineering (2017).

  
  

  Abstract

  This study investigates the performance of dye-sensitized solar cells constructed with a Fe-Cu metastable material as the mesoporous layer on which a natural organic dye is applied. The synthesis of the Fe-Cu material is done via a high throughput process that produces nanosized particles from elemental metallic powders. Xanthophyll is singled out as the organic natural dye of choice among other dyes that were extracted, as it exhibited wider spectral absorptivity in terms of wavelength range and magnitude. Two compact solar cells were constructed and tested, one is a reference cell with a TiO2 working electrode and the other with a Fe-Cu working electrode. The results show a better power conversion efficiency for the Fe-Cu-based solar cell 0.943% compared to 0.638% for the TiO2, and the number of carriers in the former is found to be orders of magnitude higher than the latter (1019 vs. 1032, respectively). A thorough optical, electrical, and thermal analysis of the Fe-Cu material is conducted and used to explain the obtained results.

  Abstract
  This study investigates the performance of dye-sensitized solar cells constructed with a Fe-Cu metastable material as the mesoporous layer on which a natural organic dye is [...]

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• Review of passive heating/cooling systems of buildings

  N. Gupta, G. Tiwari

  Energy Science & Engineering (2017).

  
  

  Abstract

  In this review, an attempt has been made to analyze passive solar heating and cooling concepts along with their effects on performance of a buildings thermal management. The concepts of Trombe wall, solarium, evaporative cooling, ventilation, radiative cooling, wind tower, earth air heat exchanger, roof pond, solar shading for buildings, and building-integrated photovoltaic thermal (BiPVT) systems are extensively covered in this review. Comparison of results by various heating and cooling concepts has been made. It has been observed that direct heating through double-glazed window saves maximum conventional fuel for thermal heating during winter months. Further, an evaporative cooling is one of the best cooling concepts which is economical too in summer period.

  Abstract
  In this review, an attempt has been made to analyze passive solar heating and cooling concepts along with their effects on performance of a buildings thermal management. The [...]

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• Offshore wind energy potential estimation using UPSCALE climate data

  M. Gross, V. Magar

  Energy Science & Engineering (2017).

  
  

  Abstract

  Offshore and near-shore wind energy is one of the major renewable energy resources, which already make a substantial contribution to the energy supply in Europe. Nevertheless, development is still in the start-up phase, with new projects being planned and implemented continuously. This development needs to be informed, to enable deployment at the most suitable/ideal locations. However, in order to predict the potential energy yield, forecasts have to be made. In this paper the authors present a scoping study. This study uses high-resolution climate data to predict wind speeds at various heights, and various locations along the coast of Mexico. Several techniques for wind extrapolation are explored, alongside a new method based on data analysis. The results show clearly a strong sensitivity to the method chosen, and results have to be interpreted accordingly. Also, the impact of water vapor is shown, using a method that predicts the moist air density at the hub height. The paper indicates that valuable information can be gained from the analyses undertaken, prior to embarking on detailed, targeted studies. The paper concludes with recommendations for further work.

  Abstract
  Offshore and near-shore wind energy is one of the major renewable energy resources, which already make a substantial contribution to the energy supply in Europe. Nevertheless, [...]

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• Influence of different SSF conditions on ethanol production from corn stover at high solids loadings

  A. Gladis, P. Bondesson, M. Galbe, G. Zacchi

  Energy Science & Engineering (2017).

  
  

  Abstract

  In this study, three different kinds of simultaneous saccharification and fermentation (SSF) of washed pretreated corn stover with water-insoluble solids (WIS) content of 20% were investigated to find which one resulted in highest ethanol yield at high-solids loadings. The different methods were batch SSF, prehydrolysis followed by batch SSF and fed-batch SSF. Batch-SSF resulted in an ethanol yield of 75–76% and an ethanol concentration of 53 g/L. Prehydrolysis prior to batch SSF did not improve the ethanol yield compared with batch SSF. Fed-batch SSF, on the other hand, increased the yield, independent of the feeding conditions used (79–81%, 57–60 g/L). If the initial amount of solids during fed-batch SSF was lowered, the yield could be improved to some extent. When decreasing the enzyme dosage, the greatest decrease in yield was seen in the fed-batch mode (75%), while lower or the same yield was seen in batch mode with and without prehydrolysis (73%). This resulted in similar ethanol yields in all methods. However, the residence time to achieve the final ethanol yield was shorter using fed-batch. This shows that fed-batch can be a better alternative also at a lower enzyme loading.

  Abstract
  In this study, three different kinds of simultaneous saccharification and fermentation (SSF) of washed pretreated corn stover with water-insoluble solids (WIS) content of [...]

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• High efficiency thin-film amorphous silicon solar cells

  A. Ghahremani, A. Fathy

  Energy Science & Engineering (2017).

  
  

  Abstract

  Enhancing light absorption within thin film amorphous silicon (a-Si) solar cells should lead to higher efficiency. This improvement is typically done using various light trapping techniques such as utilizing textured back reflectors for pronounced light scattering within the cell thus achieving higher absorption. It is believed that embedding metallic nanoparticles (MNPs) inside the structure could increase light scattering. However, embedding MNPs can also cause significant structure defects and pronounced efficiency drop as well – it has been indicated by many experiments that disproved this belief. In search of ways to improve efficiency, we have investigated the impact of MNPs size, and location within the solar cell, in addition to the effect of defects, and doping levels on the overall efficiency. On the basis of our 3D multiphysics (optical-electric) modeling, we developed a design guideline for embedding these MNPs and reducing the impact of defects created in the embedding process. The results of simulations were compared to relevant measured data, and it showed a good agreement. Subsequently, models were used to predict performance, and over 30% improvement in solar cell efficiency (~13% is predicted), which is beyond the state of the art. This was predicted by optimizing the size and location of the MNPs and tailoring the doping levels to have better forward light trapping and absorption.

  Abstract
  Enhancing light absorption within thin film amorphous silicon (a-Si) solar cells should lead to higher efficiency. This improvement is typically done using various light trapping [...]

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• A three-dimensional multiphysics modeling of thin-film amorphous silicon solar cells

  A. Ghahremani, A. Fathy

  Energy Science & Engineering (2017).

  
  

  Abstract

  A 3D multiphysics simulation toolbox for thin-film amorphous silicon solar cells has been developed. The simulation is rigorous and is based on developing three modules: first to analyze light propagation using electromagnetic techniques, second to account for charge generation and transportation based on the physics of the semiconductor device, and third including electrode modeling by applying electrostatic techniques. Published results of a P-I-N thin-film amorphous silicon solar cell fabricated on a thick glass and experimentally evaluated was used as a vehicle to validate our 3D multiphysics toolbox and demonstrate its capabilities. The toolbox utilizes COMSOL for solving the partial differential equations describing the three modules, and MATLAB to input data, control the solver, and provides the coupling between the three modules. The developed toolbox was used to investigate both the effect of embedding Metallic Nanoparticles (MNPs) and the impact of defects on the external quantum efficiency. The simulator, besides being rigorous, is suitable to model various types of solar cells (organic, inorganic, thick film, thin film, heterojunction, or plasmonic) as well.

  Abstract
  A 3D multiphysics simulation toolbox for thin-film amorphous silicon solar cells has been developed. The simulation is rigorous and is based on developing three modules: first [...]

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• Reservoir modeling for Wabamun lake sequestration project

  S. Ghaderi, Y. Leonenko

  Energy Science & Engineering (2017).

  
  

  Abstract

  A study, entitled “Wabamun Lake Sequestration Project” or “WASP, ” was performed to evaluate large-scale CO2 storage opportunities in the Wabamun area including potential risks. The project examined the feasibility of storing 20 megatons (Mt) of CO2 per year over 50 years. This scale is one order of magnitude larger than the typical benchmark (1 Mt/year) used in academic research and commercial projects that are currently in place or under review. The study was conducted by a group of researchers from several universities as well as industry consultants. This study presents an overview of the reservoir modeling part of this study, which the authors were responsible for. The main objectives of the reservoir modeling for WASP project were as follows: (1) estimation of storage capacity (traditionally, this value is projected based on the available pore space, but we have an additional practical consideration: the maximum amount one can inject within short period of time [~50 years] and within a localized injection area [~30 km × 90 km]), (2) investigation of CO2 plume movement and pressure distribution during and after injection including the effect of formation dip angle on the plume shape and its migration, (3) investigation of the long-term fate of injection associated with free phase CO2 (risks of leakage) and aquifer pressurization (possible geomechanical changes and related phenomena), (4) investigation of the phase behavior of H2S initially available and dissolved in brine during CO2 sequestration process. The WASP reservoir modeling study mentioned above led to a few important findings. The most important one is that, when CO2 is being injected into a sour aquifer, initially dissolved H2S will release into the expanding CO2 plume and accumulate at the leading edge of the plume. Also, the large-scale injection scheme (20 Mt/year), which requires multi well injectors, provides very different pressure response compared to a one well (1 Mt/year) scenario.

  Abstract
  A study, entitled “Wabamun Lake Sequestration Project” or “WASP, ” was performed to evaluate large-scale CO2 storage opportunities in the Wabamun area including potential [...]

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• Liquinert quartz crucible for the growth of multicrystalline Si ingots

  K. Fujiwara, Y. Horioka, S. Sakuragi

  Energy Science & Engineering (2017).

  
  

  Abstract

  The growth of a multicrystalline silicon (mc-Si) ingot for solar cell applications was attempted using a Liquinert quartz crucible. A mc-Si ingot was also grown in a quartz crucible coated with Si3N4 powder for comparison with that from the Liquinert quartz crucible. The mc-Si ingot grown in the Liquinert quartz crucible had a shinier surface which has few impurity particles and higher minority carrier lifetime than the mc-Si ingot grown in a quartz crucible coated with Si3N4 powder. These results indicate that contamination with impurities was reduced with the Liquinert quartz crucible, therefore, this crucible has the potential to be a powerful tool for the production of high-quality mc-Si ingots for solar cell applications.

  Abstract
  The growth of a multicrystalline silicon (mc-Si) ingot for solar cell applications was attempted using a Liquinert quartz crucible. A mc-Si ingot was also grown in a quartz [...]

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• Cyclical hydrogen storage and retention in polyaniline

  R. Ebrahim, A. Zomorrodian, N. Attia, K. Geckeler, A. Ignatiev

  Energy Science & Engineering (2017).

  
  

  Abstract

  Hydrogen adsorption in porous nanostructured polyaniline (PANI) has been investigated to determine its potential as a hydrogen storage media. Residual gas analysis and thermogravimetric analysis were used to investigate the cyclical hydrogen adsorption in PANI. A hydrogen storage capacity of up to 3 wt % was obtained by charging the polymers at up to 3.0 × 106 Pa hydrogen at elevated temperature. Multiple charge and discharge cycles have been shown, with good retention beyond 106 sec.

  Abstract
  Hydrogen adsorption in porous nanostructured polyaniline (PANI) has been investigated to determine its potential as a hydrogen storage media. Residual gas analysis and thermogravimetric [...]

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