Documents published in Scipedia

• Dynamic modeling of a small open Joule cycle reciprocating Ericsson engine: simulation results

  F. Lontsi, O. Hamandjoda, K. Djanna, P. Stouffs, J. Nganhou

  Energy Science & Engineering (2017).

  
  

  Abstract

  Externally heated Joule cycle reciprocating engines, also known as Ericsson engines, are particularly suitable for small-scale solar energy conversion and microcogeneration using biomass or gas effluents at high temperatures. These types of engine have been developed in the context of the current issue of climate change, combined with a progressive depletion of fossil fuels. A dynamic model of a 1.67 kW small open Joule cycle engine has been developed in order to study operational stability and behavioral control, especially during transient phases. Models are implemented on a Matlab/Simulink platform where simulations of the dynamics of engine start-up and steady conditions are carried out. The optimal settings of valves and the key engine parameters have also been determined. Simulation results reveal a rapid transient phase. Hot starting is achieved in about 5.3 sec and the system is stabilized, with a thermal efficiency of approximately 29%. The system responds well when subjected to selected perturbations.

  Abstract
  Externally heated Joule cycle reciprocating engines, also known as Ericsson engines, are particularly suitable for small-scale solar energy conversion and microcogeneration [...]

  • 0
  •  read

• An A-CAES pilot installation in the distribution system: A technical study for RES integration

  P. Lombardi, C. Röhrig, K. Rudion, R. Marquardt, M. Müller-Mienack, A. Estermann, Z. Styczynski, N. Voropai

  Energy Science & Engineering (2017).

  
  

  Abstract

  In the last decade in Europe, the power generated by Renewable Energy Sources (RES) has significantly increased. For the electric power system, the integration of a high amount of power generated by RES represents a big challenge. Energy Storage Systems (ESS) may help to solve problems related to the grid integration of RES. In this study, an analysis of the benefits that a planned and dedicated Adiabatic Compressed Air Energy Storage (A-CAES) system may provide to a distribution network with a high penetration of RES will be carried out. The A-CAES system, taken into account in this investigation, is based on the proposed German study so-called “ADELE project”. The technical benefits as well as the corresponding costs that A-CAES brings to the system which were analyzed using the load and RES generation time series for 2010 and 2020, and were based on technical data from a selected part of a German distribution power network, were evaluated and results of those broad investigations are presented in this study. The result of the investigations shows that the direct technical benefits are quite limited for the A-CAES technology as it exists today.

  Abstract
  In the last decade in Europe, the power generated by Renewable Energy Sources (RES) has significantly increased. For the electric power system, the integration of a high amount [...]

  • 0
  •  read

• Steady-state and transient voltage stability analysis of a weak distribution system with a remote doubly fed induction generator-based wind farm

  A. Kunwar, R. Bansal, O. Krause

  Energy Science & Engineering (2017).

  
  

  Abstract

  In modern, stressed distribution system, voltage stability is a major concern from planning and operation perspectives. Remote wind farm connected to a weak distribution system through a long line could adversely affect the voltage stability of the respective distribution network. This paper investigates the transient and steady-state voltage issues of a distribution network with a distant doubly fed induction generator (DFIG)-based wind farm. Results show that a distant DFIG-based wind farm could improve the voltage stability of a distribution network with a large motor load in steady-state operating condition as well as following disturbances, like three-phase faults, sudden load tripping, and motor starting.

  Abstract
  In modern, stressed distribution system, voltage stability is a major concern from planning and operation perspectives. Remote wind farm connected to a weak distribution system [...]

  • 0
  •  read

• Engineering evaluation of direct methane to methanol conversion

  A. Klerk

  Energy Science & Engineering (2017).

  
  

  Abstract

  Investigations into direct methane to methanol conversion are justified based on the avoidance of synthesis gas generation, which accounts for around 60% of the capital cost of synthesis gas to methanol conversion. A significant body of information already exists on the process chemistry, but little has been reported on the engineering of such a process. An engineering evaluation of the process was performed and the potential of this process as a platform technology for small-scale gas-to-liquids (GTL) applications was evaluated. It was found that direct methane to methanol conversion had 35% carbon efficiency and 28% thermal efficiency, which were about half of the process efficiencies of indirect methanol synthesis using synthesis gas. The poor process efficiency was mainly a consequence of the irreversible loss of carbon to CO x during conversion. The direct methane to methanol process also required an air separation unit, which eroded the stated benefit of avoiding a synthesis gas generation step in the process. The utility footprint was typical of GTL processes, with large gas compression duties and cooling duties. Overall, the engineering evaluation indicated there was no benefit to employ direct methane to methanol conversion instead of indirect methanol synthesis (the industry standard), and there was no specific benefit of direct methane to methanol conversion, irrespective of scale, for GTL applications.

  Abstract
  Investigations into direct methane to methanol conversion are justified based on the avoidance of synthesis gas generation, which accounts for around 60% of the capital cost [...]

  • 0
  •  read

• Esterification of hydrolyzed sea mango (Cerbera odollam) oil using various cationic ion exchange resins

  J. Kansedo, K. Lee

  Energy Science & Engineering (2017).

  
  

  Abstract

  This study investigates the esterification of hydrolyzed sea mango (Cerbera odollam) oil using several cationic ion exchange resins. The best resins were selected based on their performance in a preliminary esterification process. The best resins were then subsequently used in the optimization of the process parameters. The esterification parameters studied were reaction temperature (40–160°C), reaction time (0–5 h), molar ratio of oil to methanol (0.5:1 to 1:14), and catalyst loading (1–14 wt%). Among the resins studied, Amberlyst 15 was found to be the most promising catalyst in the esterification of the hydrolyzed sea mango oil. Moderate reaction temperatures, 60–100°C, were found to be adequate in converting the hydrolyzed sea mango oil into esters. Further investigation revealed that the esterification reaction using the cationic ion exchange resins proceeds at a fast rate, whereby fatty acid methyl esters (FAME) yield of over 80% at moderate reaction temperature was achievable in less than 1 h of reaction time. Small amount of catalyst, which is less than 5 wt%, was also found to be sufficient in catalyzing the esterification process to an acceptable yield.

  Abstract
  This study investigates the esterification of hydrolyzed sea mango (Cerbera odollam) oil using several cationic ion exchange resins. The best resins were selected based on [...]

  • 0
  •  read

• Discovering new energy solutions

  T. Kåberger

  Energy Science & Engineering (2017).

  
  

  • 0
  •  read

• Numerical investigation of the effects of dwell time duration in a two-stage injection scheme on exergy terms in an IDI diesel engine by three-dimensional modeling

  S. Jafarmadar, A. Zehni

  Energy Science & Engineering (2017).

  
  

  Abstract

  Dwell duration of multiple-injection scheme is an important parameter, which makes it possible to shift the tradeoff curve between soot and NOx closer to the origin. In this investigation, therefore, energy and exergy analyses are carried out for various two-step injection schemes in which 25% of the total fuel is injected during the second pulse and the dwell time is increased from 5°CA (crank angle) to 30°CA by 5°CA increments. The calculations are performed for a Lister 8.1 indirect injection (IDI) diesel engine at full load operation. The energy analysis for these schemes is performed during a closed cycle by using a three-dimensional CFD code. The cylinder pressure results for the baseline engine are compared with the corresponding experimental data and they show good agreement. For the exergy analysis, an in-house computational code has been developed, which uses the results of energy analysis in various cases. With crank angle positions and dwell durations set for different injection schemes, various rates of exergy are calculated and the cumulative exergy components are identified separately. The results show that the values of work exergy and exergy efficiency decrease when the dwell duration is changed from 5°CA to 30°CA. Also, there is a sharp change in the exergy parameters when the dwell time reaches 25°CA.

  Abstract
  Dwell duration of multiple-injection scheme is an important parameter, which makes it possible to shift the tradeoff curve between soot and NOx closer to the origin. In this [...]

  • 0
  •  read

• A bridge to nowhere: methane emissions and the greenhouse gas footprint of natural gas

  R. Howarth

  Energy Science & Engineering (2017).

  
  

  Abstract

  In April 2011, we published the first peer-reviewed analysis of the greenhouse gas footprint (GHG) of shale gas, concluding that the climate impact of shale gas may be worse than that of other fossil fuels such as coal and oil because of methane emissions. We noted the poor quality of publicly available data to support our analysis and called for further research. Our paper spurred a large increase in research and analysis, including several new studies that have better measured methane emissions from natural gas systems. Here, I review this new research in the context of our 2011 paper and the fifth assessment from the Intergovernmental Panel on Climate Change released in 2013. The best data available now indicate that our estimates of methane emission from both shale gas and conventional natural gas were relatively robust. Using these new, best available data and a 20-year time period for comparing the warming potential of methane to carbon dioxide, the conclusion stands that both shale gas and conventional natural gas have a larger GHG than do coal or oil, for any possible use of natural gas and particularly for the primary uses of residential and commercial heating. The 20-year time period is appropriate because of the urgent need to reduce methane emissions over the coming 15–35 years.

  Abstract
  In April 2011, we published the first peer-reviewed analysis of the greenhouse gas footprint (GHG) of shale gas, concluding that the climate impact of shale gas may be worse [...]

  • 0
  •  read

• Turbine design and field development concepts for tidal, ocean, and river applications

  D. Zeiner-Gundersen

  Energy Science & Engineering (2017).

  
  

  Abstract

  This paper discusses tidal, ocean, and river free turbine functional design parameters and general considerations associated with tidal field developments. A particular focus is on the importance of considering mechanical fatigue and the associated calculation method when designing a turbine for the challenging hydrodynamic environment. The balance between high-fatigue resistances, costs associated with designing components, and potential for reduced turbine efficiency is discussed in regards to the potential energy extracted from a field site. A novel flexible foil vertical turbine concept with high-fatigue resistance, and simple installation and retrieval methods is shown to have a low kWh cost per production output compared to other hydrodynamic turbine concepts. Three possible field development concepts for the flexible foil turbine are described herein for river, ocean current, and tidal applications.

  Abstract
  This paper discusses tidal, ocean, and river free turbine functional design parameters and general considerations associated with tidal field developments. A particular focus [...]

  • 0
  •  read

• Effect of oxomolybdate species dispersion on direct methanol oxidation to dimethoxymethane over MoO x /TiO2 catalysts

  J. Faye, M. Capron, A. Takahashi, S. Paul, B. Katryniok, T. Fujitani, F. Dumeignil

  Energy Science & Engineering (2017).

  
  

  Abstract

  The one-step selective oxidation of methanol to dimethoxymethane (DMM) was demonstrated over titania-supported molybdenum oxide catalysts, containing different amounts of molybdenum and prepared using two different impregnation techniques, namely wet impregnation and incipient wetness impregnation. The corresponding catalysts exhibited both acidic and redox properties, which are necessary for the oxidation of methanol to formaldehyde with subsequent condensation of the latter with excess methanol to finally yield DMM. The formation of well-dispersed polyoxomolybdate species on the catalyst surface was evidenced using IR-Raman, X-ray diffraction, and nitrogen physisorption. Varying the amount of these polyoxomolydate species was associated with a modulation of the acidic and redox properties, as shown by NH3-TPD and H2-TPR. With respect to the catalytic performances, the best balance between acid and redox properties was observed over the samples containing 8 wt.% Mo, which corresponds to a theoretical MoO x species coverage close to a monolayer.

  Abstract
  The one-step selective oxidation of methanol to dimethoxymethane (DMM) was demonstrated over titania-supported molybdenum oxide catalysts, containing different amounts of [...]

  • 0
  •  read