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مرکز اطلاعات علمی SID1
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
Writer: 

LI PEIWEN | TAO GEGE | LIU HONG

Issue Info: 
  • Year: 

    2011
  • Volume: 

    2
  • Issue: 

    3
  • Start Page: 

    1
  • End Page: 

    11
Measures: 
  • Citations: 

    352
  • Views: 

    18758
  • Downloads: 

    7814
Keywords: 
Abstract: 

An analytical model is proposed and an analysis is conducted for solid oxide fuel cells with goals of higher power densities. The analytical model is designed to help optimize the size, spacing, and geome-trical shapes of current collectors. The model fully considers the ohmic, species concentration, and activa-tion polarizations. From the analysis of several cases, it is recommended that 3D pillars be used for the current collectors in SOFCs while incorporating appropriate measures to ensure a uniform flow distribu-tion. It is also clear that unless limited by the fabrication technologies for the bipolar plates, smaller con-trol areas and current collectors are preferable for SOFCs to have higher power densities.

Yearly Impact:  

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Writer: 

OLAYINKA SUNDAY

Issue Info: 
  • Year: 

    2011
  • Volume: 

    2
  • Issue: 

    3
  • Start Page: 

    13
  • End Page: 

    33
Measures: 
  • Citations: 

    0
  • Views: 

    17669
  • Downloads: 

    14736
Keywords: 
Abstract: 

In this study, estimation of global and diffuse solar radiations of selected cities in Nigeria was carried out to assess the feasibility of solar energy utilization. The results of this work show the variation of direct and diffuse component of solar radiation in summer and winter months. The contribution of diffuse solar radiation is high during the monsoon months whereas sky conditions are clear during winter months. From the estimated values it was found that solar energy can be utilized very efficiently throughout the year in Sokoto and Ilorin. The clearness index which is availability of global solar radiation varies with geographical location and period of the year. Clearness index in the cities studied varies from 0.303 to 0.683. The least clearness index is in Port- Harcourt (0.303) in the month of July and the highest value is 0.683 in Sokoto in the month of March. The values of the global solar radiation estimated in the selected cities vary from 12.67 - 20.72 MJm-2day-1 in Abeokuta, 15.17 - 22.90 MJm-2day-1 in Ilorin, 10.75 - 19.03 MJm-2day-1 in Port Harcourt and 19.08 - 25.71 MJm-2day-1 in Sokoto. The data reveal that there is an evi-dent increase of the value of the global solar radiation from south to north. This was expected as the rad-iation should increase as one move to the equatorial line. This study shows that the availability of solar energy in the selected cities varies and generation of electric power from solar energy in Nigeria is viable.

Yearly Impact:  

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    2
  • Issue: 

    3
  • Start Page: 

    35
  • End Page: 

    47
Measures: 
  • Citations: 

    352
  • Views: 

    17914
  • Downloads: 

    11615
Keywords: 
Abstract: 

Carbon Capture and Storage (CCS) systems have relevant energy consumption associated with the CO2 capture process. It causes an energy efficiency reduction that diminishes the economic interests and increases the technical uncertainty of these systems. With the objective of improving the system perform-ance and reducing thermodynamic inefficiencies, the exergy analysis has been traditionally applied as a guide for design process. This work presents and compares energy and exergy analysis of two CCS sys-tems based on pressurized oxyfuel combustion, a pressurized fluidized bed combustion working under oxyfiring conditions and a chemical looping combustion using coal as fuel. The aim is to calculate CCS energy and exergy penalties, detecting irreversibilities and proposing items for optimization. It is demon-strated that opposed to energy penalty, the exergy losses do extend neither in the same quantity nor in the same equipment, leading to outstanding conclusions for system improvements. As it will be demon-strated, the exergy penalty of additional equipment for CO2 capture does not cause relevant losses and these irreversibilities are concentrated in several systems that should be redesigned or analysed in detail to reduce the losses.

Yearly Impact:  

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    2
  • Issue: 

    3
  • Start Page: 

    49
  • End Page: 

    62
Measures: 
  • Citations: 

    0
  • Views: 

    20013
  • Downloads: 

    9913
Abstract: 

Hydrogen as an ideal energy carrier can play a very important role in future energy systems for hydro-gen production can be used a variety of technologies and sources. One of the most promising methods for large-scale hydrogen production is thermo-chemical water decomposition using heat energy from nuclear, solar and other sources. The water splitting thermo-chemicals cycles are processes where water is decomposed into hydrogen and oxygen via chemical reactions, using intermediate substances which are recycled. Two cycles were retained interesting and chosen for our study: WestingHouse cycle (WH cycle) and Sulphur-Iodine cycle (SI cycle). For both cycles solar energy has been considered as heat source during the endothermic step of the cycle. Detailed simulation models of both cycles were performed using Aspen Plus code and a ther-modynamic analysis was conducted to evaluate the effective plant energetic efficiencies, with respect to their thermodynamic theoretical values. The advantages and disadvantages of both cycles were taken into account. For the WH cycle, an optimization study for SO2/O2 separation process, in order to maximize hydrogen production, was carried out. The obtained results are reported.

Yearly Impact:  

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    2
  • Issue: 

    3
  • Start Page: 

    63
  • End Page: 

    78
Measures: 
  • Citations: 

    0
  • Views: 

    20000
  • Downloads: 

    14200
Abstract: 

The aim of this study is to compare the environmental effects, through Life Cycle Assessment Ap-proach, of three hydrogen production methods: methane steam reforming, water electrolysis fed by photovoltaic electricity, water electrolysis fed by mini-hydroelectric electricity. The assumptions are based on a project proposal of introducing some mini-buses in the city centre of Florence (Italy), equipped with fuel cells fuelled with hydrogen. The inventory of the compared productive cycles has been performed using the literature and direct data obtained from device manufactures. The impact analysis has been carried out using two methods, the Ecoindicator’95 and the Ecoindicator’99 also with the intention of qualitatively comparing the results. Besides the "basic option" an improvement has been proposed focusing on the weak points of the productive cycles. In particular concerning photovoltaic and mini-hydroelectric, the construction phase showed a high contribution to the envi-ronmental load, so some improvements were proposed. The results of the basic option and the im-proved one have been compared. According to the initial assumptions and the proposed changes, the best option for hydrogen production has been highlighted.

Yearly Impact:  

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Writer: 

JAHANIAN O. | JAZAYERI S.A.

Issue Info: 
  • Year: 

    2011
  • Volume: 

    2
  • Issue: 

    3
  • Start Page: 

    79
  • End Page: 

    89
Measures: 
  • Citations: 

    0
  • Views: 

    13486
  • Downloads: 

    7977
Keywords: 
Abstract: 

In this paper, the performance of a natural gas HCCI engine is studied through a thermodynamic model including detailed chemical kinetics. It is shown that as hydroxyl radical has important effects on natural gas combustion, it is possible to quantify SOC with hydroxyl concentration variations. Meanwhile the in-fluence of using formaldehyde as an additive on the engine characteristics has been investigated. Results show that it is possible to change the engine working limits using this additive. Lower autoignition tem-perature of formaldehyde causes advanced combustion in natural gas HCCI engine. In TIVC = 410K case, adding 5% formaldehyde would lead to more than 10 CA advance in SOC. Furthermore, there is an opti-mum additive content for each operating condition, which leads to higher output work and power. It is also shown that the air/fuel mixture will ignite earlier using this additive so it is conceivable to reduce inlet mixture temperature resulting in better performance due to higher volumetric efficiency.

Yearly Impact:  

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    2
  • Issue: 

    3
  • Start Page: 

    91
  • End Page: 

    99
Measures: 
  • Citations: 

    352
  • Views: 

    41789
  • Downloads: 

    14340
Keywords: 
Abstract: 

Although in Mexico the cases and the experiences in bioenergy production are limited, at a worldwide level the knowledge in this area has grown up significantly. For example, unlike Argentina and Brazil, Mexico has only recently begun its bioenergy production from agricultural crops. So this paper will present a review of the actual conditions encountered in Mexico as far as biofuels production is con-cerned, in particular biodiesel. In this regard, the driving forces and barriers (economic, political and technical) to the introduction of biodiesel into the Mexican energy matrix are evaluated. In particular, the study has been directed toward the use of biodiesel as the transport fuel, since this productive sector con-sumes roughly 30 per cent of the Mexican energy resources, hence the use of biodiesel as a possible subs-titute for some fossil fuels is gaining more interest and it is foreseen as a strategy for the future. The study also presents the production processes of biodiesel most utilized in Mexico as well as their advantages and drawbacks. At the conclusion of this review, some well-grounded suggestions needed to make deci-sions with respect to the sustainable introduction of biodiesel in the energy matrix are included, bearing in mind the reality of the country.

Yearly Impact:  

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مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID
مرکز اطلاعات علمی SID