Documents published in Scipedia

• The great solar boom: a global perspective into the far reaching impact of an unexpected energy revolution

  F. Meneguzzo, R. Ciriminna, L. Albanese, M. Pagliaro

  Energy Science & Engineering (2017).

  
  

  Abstract

  This study offers a unified perspective into the unexpected solar energy photovoltaic revolution, and its far reaching impact onto both energy generation and electricity markets. Practically relevant aspects, such as those related to the value of solar PV electricity, land consumption, energy return on energy invested, reliability of the technology, the structure of the global PV industry, the cost of Li ion batteries and related market trends are clarified. We identify the main barriers to overcome for solar PV to expand beyond a niche market (say,

  Abstract
  This study offers a unified perspective into the unexpected solar energy photovoltaic revolution, and its far reaching impact onto both energy generation and electricity markets. [...]

  • 0
  •  read

• Biodiesel from grease interceptor to gas tank

  A. Ragauskas, Y. Pu, A. Ragauskas

  Energy Science & Engineering (2017).

  
  

  Abstract

  The need for sustainable biofuels has initiated a global search for innovative technologies that can sustainably convert nonfood bioresources to liquid transportation fuels. While 2nd generation cellulosic ethanol has begun to address this challenge, other resources including yellow and brown grease are rapidly evolving commercial opportunities that are addressing regional biodiesel needs. This review examines the technical and environmental factors driving the collection of trap FOG (Fats, Oils, and Greases), its chemical composition and technologies currently available and future developments that facilitate the conversion of FOG into biodiesel.

  Abstract
  The need for sustainable biofuels has initiated a global search for innovative technologies that can sustainably convert nonfood bioresources to liquid transportation fuels. [...]

  • 0
  •  read

• Design, operation, and performance evaluation of a cable-drawn dual-axis solar tracker compared to a fixed-tilted system

  S. Lo, F. Cheng, V. Chang, W. Liu, L. Chang, O. Adurodija, E. Chou, C. Lung, J. Liu, T. Lu, J. Su, E. Cheng

  Energy Science & Engineering (2017).

  
  

  Abstract

  This article discusses the design, operation, and performance evaluation of a unique cable-operated 6.24 kWp commercial-size solar tracking system called iPV dual-axis tracker or iPV DAT with a position detector to gain the maximum power from the sunlight. Compared with other solar tracking systems, low cost, simplified hardware structure, and controlling algorithm are the advantages of this system. The operating method of the 6.24 kWp iPV DAT follow a simple pull and release of the steel cables connecting the corners of the PV module frame to the electric motors and directed by an electronic control system. The steel cables attached to the corners of the module frame also provide an extra stability in the event of high wind of up to 220 km/h. The accuracy of the tracking effect is managed by an astronomical algorithm that enables a full 360° azimuth rotation and altitude tilt of −40° to 40° (0 = horizontal). The controller algorithm also includes backtracking capability that allows optimization of ground cover ratio. Performance evaluation of the iPV DAT installed and operated in Taiwan for 12 months is compared with a fixed-tilt PV system. An average electricity gain of 30.1% and performance ratio of 93% are realized using iPV DAT.

  Abstract
  This article discusses the design, operation, and performance evaluation of a unique cable-operated 6.24 kWp commercial-size solar tracking system called iPV dual-axis tracker [...]

  • 0
  •  read

• Systematic study of aqueous monoethanolamine-based CO2 capture process: model development and process improvement

  K. Li, A. Cousins, H. Yu, P. Feron, M. Tade, W. Luo, J. Chen

  Energy Science & Engineering (2017).

  
  

  Abstract

  In this paper, we present improvements to postcombustion capture (PCC) processes based on aqueous monoethanolamine (MEA). First, a rigorous, rate-based model of the carbon dioxide (CO2) capture process from flue gas by aqueous MEA was developed using Aspen Plus, and validated against results from the PCC pilot plant trials located at the coal-fired Tarong power station in Queensland, Australia. The model satisfactorily predicted the comprehensive experimental results from CO2 absorption and CO2 stripping process. The model was then employed to guide the systematic study of the MEA-based CO2 capture process for the reduction in regeneration energy penalty through parameter optimization and process modification. Important process parameters such as MEA concentration, lean CO2 loading, lean temperature, and stripper pressure were optimized. The process modifications were investigated, which included the absorber intercooling, rich-split, and stripper interheating processes. The minimum regeneration energy obtained from the combined parameter optimization and process modification was 3.1 MJ/kg CO2. This study suggests that the combination of a validated rate-based model and process simulation can be used as an effective tool to guide sophisticated process plant, equipment design and process improvement.

  Abstract
  In this paper, we present improvements to postcombustion capture (PCC) processes based on aqueous monoethanolamine (MEA). First, a rigorous, rate-based model of the carbon [...]

  • 0
  •  read

• Models and experiments for energy consumption and quality of green tea drying

  N. Langat, T. Thoruwa, J. Wanyoko, J. Kiplagat, B. Plourde, J. Abraham

  Energy Science & Engineering (2017).

  
  

  Abstract

  An experimental apparatus has been developed to evaluate the drying process of green tea leaves. Tea drying is an energy-intensive process which results in the removal of leaf moisture, it is essential to the quality of the final product. In order to more efficiently use process energy, a prototype drying system has been built and tested. The prototype incorporates a rotating perforated drum which helps speed the drying process. Experiments were carried out with multiple temperatures, airflow rates, and drum rotation rates, a subset of those results is shown here. In particular, the impact of airflow rate on the process was studied. It was found that as the airflow increased, the drying rate increased, as expected. However, the efficiency of energy use, which was quantified by the Specific Energy Consumption rate, varied considerably with flow. While higher flows led to faster drying, it resulted in a lower energy efficiency. Also, a two parameter predictive model was developed that was able to accurately match the moisture removal rates for a very wide range of flows. This predictive model, which is based on thermal-fluid fundamentals, can be used to extrapolate the presented results to cases which were not considered.

  Abstract
  An experimental apparatus has been developed to evaluate the drying process of green tea leaves. Tea drying is an energy-intensive process which results in the removal of [...]

  • 0
  •  read

• Various operating methods and parameters for SO2 electrolysis

  A. Krüger, H. Krieg, S. Grigoriev, D. Bessarabov

  Energy Science & Engineering (2017).

  
  

  Abstract

  The application of PFSA-based proton exchange membranes was investigated for the production of hydrogen and sulfuric acid using a SO2-depolarized electrolyzer system. Parameters investigated included hot pressing pressure for the membrane electrode assembly (MEA) manufacturing, cell temperature, membrane thickness, catalyst loading, membrane type, and SO2 anode feed concentration. The effect of cell temperature, membrane thickness, and acid concentrations was also investigated when using a second method, where clean sulfuric acid as cathode and SO2 saturated sulfuric acid as anode were used. Electrochemical impedance spectroscopy showed that the pressure exerted in the MEA manufacturing step had a significant influence with 125 kg cm−2 yielding the highest current density. High temperatures (>80°C) and thin membranes (≈120 μm) showed the best performance while thicker membranes produced higher acid concentration when using the first system. The SO2 concentration in the anode had a significant influence with the over potential increasing with decreasing SO2 concentration. When using the second method, it was found that the SO2 solubility in sulfuric acid is important as the mass transport of the SO2 limits the overall reaction rate. From the two systems tested, the first method, that is, dry SO2 anode and liquid water cathode showed the best operational effectiveness reaching a maximum of 0.32 A cm−2 at 80°C using N115 coated with 1 mgPt cm−2 while the second system under the same conditions achieved a current density of 0.18 A cm−2 when using N117.

  Abstract
  The application of PFSA-based proton exchange membranes was investigated for the production of hydrogen and sulfuric acid using a SO2-depolarized electrolyzer system. Parameters [...]

  • 0
  •  read

• Influence of different adsorbates on the efficiency of thermochemical energy storage

  T. Kohler, K. Müller

  Energy Science & Engineering (2017).

  
  

  Abstract

  The main influencing parameter on the efficiency of adsorptive thermochemical energy storage is the efficiency of the desorption process, which is influenced by the process conditions, for example, desorption time and desorption temperature, and the working pair (adsorbent–adsorbate). Due to constrained process requirements, for example, hours of sun shine and low desorption temperatures available from a flat plate solar collector (333–373 K), the only possibility to increase the efficiency is to change the working pair. The reference working pair water–zeolite 13X needs high desorption temperatures of 500 K and high heat inputs per mass adsorbent (1080 kJ kg−1) in the desorption process to reach the maximum efficiency of 79 % and maximum energy density of 844 kJ kg−1. Therefore, the goal is to reach efficiencies in the same range as the maximum efficiency of water–zeolite 13X for desorption temperatures lower than 500 K with the usage of different adsorbates. Four systems of alcohol as adsorbate on activated carbon are compared with the reference working pair. The usage of alcohols on activated carbon allows for highly efficient adsorptive storage even at low desorption temperatures between 360 and 450 K. The maximum efficiency is shifted to higher desorption temperatures with increasing carbon chain length of the alcohol. At low desorption temperatures, the energy density and efficiency of methanol, ethanol, and propanol are higher than the energy density of the reference system. Hence, the alcohol systems on activated carbon are viable alternative approaches for regulating these process parameters.

  Abstract
  The main influencing parameter on the efficiency of adsorptive thermochemical energy storage is the efficiency of the desorption process, which is influenced by the process [...]

  • 0
  •  read

• Multi angle laser light scattering evaluation of field exposed thermoplastic photovoltaic encapsulant materials

  M. Kempe, D. Miller, J. Wohlgemuth, S. Kurtz, J. Moseley, D. Nobles, K. Stika, Y. Brun, S. Samuels, Q. Shah, G. Tamizhmani, K. Sakurai, M. Inoue, T. Doi, A. Masuda, C. Vanderpan

  Energy Science & Engineering (2017).

  
  

  Abstract

  As creep of polymeric materials is potentially a safety concern for photovoltaic modules, the potential for module creep has become a significant topic of discussion in the development of IEC 61730 and IEC 61215. To investigate the possibility of creep, modules were constructed, using several thermoplastic encapsulant materials, into thin-film mock modules and deployed in Mesa, Arizona. The materials examined included poly(ethylene)-co-vinyl acetate (EVA, including formulations both cross-linked and with no curing agent), polyethylene/polyoctene copolymer (PO), poly(dimethylsiloxane) (PDMS), polyvinyl butyral (PVB), and thermoplastic polyurethane (TPU). The absence of creep in this experiment is attributable to several factors of which the most notable one was the unexpected cross-linking of an EVA formulation without a cross-linking agent. It was also found that some materials experienced both chain scission and cross-linking reactions, sometimes with a significant dependence on location within a module. The TPU and EVA samples were found to degrade with cross-linking reactions dominating over chain scission. In contrast, the PO materials degraded with chain scission dominating over cross-linking reactions. Although we found no significant indications that viscous creep is likely to occur in fielded modules capable of passing the qualification tests, we note that one should consider how a polymer degrades, chain scission or cross-linking, in assessing the suitability of a thermoplastic polymer in terrestrial photovoltaic applications.

  Abstract
  As creep of polymeric materials is potentially a safety concern for photovoltaic modules, the potential for module creep has become a significant topic of discussion in the [...]

  • 0
  •  read

• Field testing of thermoplastic encapsulants in high-temperature installations

  M. Kempe, D. Miller, J. Wohlgemuth, S. Kurtz, J. Moseley, Q. Shah, G. Tamizhmani, K. Sakurai, M. Inoue, T. Doi, A. Masuda, S. Samuels, C. Vanderpan

  Energy Science & Engineering (2017).

  
  

  Abstract

  Recently there has been increased interest in using thermoplastic encapsulant materials in photovoltaic modules, but concerns have been raised about whether these would be mechanically stable at high temperatures in the field. Recently, this has become a significant topic of discussion in the development of IEC 61730 and IEC 61215. We constructed eight pairs of crystalline-silicon modules and eight pairs of glass/encapsulation/glass thin-film mock modules using different encapsulant materials, of which only two were formulated to chemically crosslink. One module set was exposed outdoors with thermal insulation on the back side in Mesa, Arizona, in the summer (hot-dry), and an identical module set was exposed in environmental chambers. High-precision creep measurements (±20 μm) and electrical performance measurements indicate that despite many of these polymeric materials operating in the melt or rubbery state during outdoor deployment, no significant creep was seen because of their high viscosity, lower operating temperature at the edges, and/or the formation of chemical crosslinks in many of the encapsulants with age despite the absence of a crosslinking agent. Only an ethylene-vinyl acetate (EVA) encapsulant formulated without a peroxide crosslinking agent crept significantly. In the case of the crystalline-silicon modules, the physical restraint of the backsheet reduced creep further and was not detectable even for the EVA without peroxide. Because of the propensity of some polymeric materials to crosslink as they age, typical thermoplastic encapsulants would be unlikely to result in creep in the vast majority of installations.

  Abstract
  Recently there has been increased interest in using thermoplastic encapsulant materials in photovoltaic modules, but concerns have been raised about whether these would be [...]

  • 0
  •  read

• Al2O3/TiO2 double layer anti-reflection coating film for crystalline silicon solar cells formed by spray pyrolysis

  H. Kanda, A. Uzum, N. Harano, S. Yoshinaga, Y. Ishikawa, Y. Uraoka, H. Fukui, T. Harada, S. Ito

  Energy Science & Engineering (2017).

  
  

  Abstract

  An Al2O3/TiO2 double layer anti-reflection coating (ARC) film formed by spray pyrolysis was introduced for monocrystalline silicon solar cells as the nonvacuum processing method. The thickness of the Al2O3 layer and TiO2 compact layer was controlled by the volume of deposited precursor solution and confirmed by ellipsometry and scanning electron microscopy. The average photovoltaic properties of photocurrent density (Jsc), open-circuit photovoltage (Voc), fill factor (FF), and photo energy conversion efficiency (η) were 37.0 mA/cm2, 590 mV, 0.712, and 15.5%, respectively. A significant improvement on Jsc and η could be confirmed owing to the Al2O3/TiO2 ARC. The results of Fourier transform infrared (FTIR) spectroscopy and optical simulation with modeling for the reflectance properties confirmed that C-H-based organics remained after the deposition of thin films.

  Abstract
  An Al2O3/TiO2 double layer anti-reflection coating (ARC) film formed by spray pyrolysis was introduced for monocrystalline silicon solar cells as the nonvacuum processing [...]

  • 0
  •  read