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Aims and Scope
Editorial Board

1. A CFD analysis of transport phenomena and electrochemical reactions in a tubular-shaped PEM fuel cell

Maher A.R. Sadiq Al-Baghdadi

Fuel Cell Research Center, International Energy & Environment Foundation, Al-Najaf, P.O.Box 39, Iraq.

Abstract: A fuel cell is most interesting new power source because it solves not only the environment problem but also natural resource exhaustion problem. CFD modeling and simulation for heat and mass transport in PEM fuel cells are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize fuel cell designs before building a prototype for engineering application. In this research, full three-dimensional, non-isothermal computational fluid dynamics model of a tubular-shaped proton exchange membrane (PEM) fuel cell has been developed. This comprehensive model accounts for the major transport phenomena such as convective and diffusive heat and mass transfer, electrode kinetics, transport and phase-change mechanism of water, and potential fields in a tubular-shaped PEM fuel cell. The model explains many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally. Three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented and analysed, with the focus on the physical insight and fundamental understanding.

Volume 4, Issue 1, 2013, pp.1-26.

2. Power generation from wind turbines in a solar chimney

Tudor Foote¹, Ramesh K. Agarwal²

1 Graduate Student, Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, Jolley Hall, Campus Box 1185, One Brookings Drive, St. Louis, Missouri, 63130, USA.

2 William Palm Professor, Department of Mechanical Engineering & Materials Science, Washington University in St. Louis, Jolley Hall, Campus Box 1185, One Brookings Drive, St. Louis, Missouri, 63130, USA.

Abstract: Recent studies have shown that shrouded wind turbines can generate greater power compared to bare turbines. A solar chimney generates an upward draft of wind inside a tower and a shroud around the wind turbine. There are numerous empty silos on farms in the U.S. that can be converted to solar chimneys with minor modifications at modest cost. The objective of this study is to determine the potential of these silos/chimneys for generating wind power. The study is conducted through analytical/computational approach by employing the commercial Computational Fluid Dynamics (CFD) software. Computations are performed for five different geometric configurations consisting of a turbine, a cylindrical silo, and/or a venturi and/or a diffuser using the dimensions of typical silos and assuming Class 3 wind velocity. The incompressible Navier-Stokes equations with the Boussinesq approximation and a two equation realizable k – ε model are employed in the calculations, and the turbine is modeled as an actuator disk. The power coefficient (Cp) and generated power are calculated for the five cases. Consistent with recent literature, it was found that the silos with diffusers increase the Cp beyond Betz’s limit significantly and thus the generated power. It should be noted that Cp is calculated by normalizing it by the turbine area swept by the wind. This study shows the potential of using abandoned silos in the mid-west and other parts of the country for localized wind power generation.

3. Optimized CO₂-flue gas separation model for a coal fired power plant

Udara S. P. R. Arachchige¹, Muhammad Mohsin¹, Morten C. Melaaen^1,2

1 Telemark University College, Porsgrunn, Norway.

2 Tel-Tek, Porsgrunn, Norway.

Abstract: The detailed description of the CO₂ removal process using mono-ethylamine (MEA) as a solvent for coal-fired power plant is present in this paper. The rate based Electrolyte NRTL activity coefficient model was used in the Aspen Plus. The complete removal process with re-circulating solvent back to the absorber was implemented with the sequential modular method in Aspen Plus. The most significant cost related to CO₂ capture is the energy requirement for re-generating solvent, i.e. re-boiler duty. Parameters’ effects on re-boiler duty were studied, resulting decreased re-boiler duty with the packing height and absorber packing diameter, absorber pressure, solvent temperature, stripper packing height and diameter. On the other hand, with the flue gas temperature, re-boiler duty is increased. The temperature profiles and CO₂ loading profiles were used to check the model behavior.

4. Diffusion of photovoltaic systems for rural electrification in Thailand

Pranpreya Sriwannawit, Staffan Laestadius

Department of Industrial Economics and Management, Royal Institute of Technology (KTH), Lindstedtsvägen 30, Stockholm 10044, Sweden.

Abstract: This paper studies a pilot project in which photovoltaic systems were installed in thirty-six places in the remote areas of Thailand with no access to electricity. One sub-project out of thirty-six was chosen for in-depth investigation. We discuss the appropriateness of solar energy for Thailand context. The diffusion process of PV systems is analyzed on four elements: innovation, communication channel, time and social system. This project is an extreme case as the PV systems and services were provided for free of charge. Even so, there are still some challenges to get acceptance for this sustainable form of energy.

5. Changes of temperature data for energy studies over time and their impact on energy consumption and CO₂ emissions. The case of Athens and Thessaloniki – Greece

K. T. Papakostas¹, A. Michopoulos¹, T. Mavromatis², N. Kyriakis¹

1 Process Equipment Design Laboratory, Mechanical Engineering Department, Energy Division, Aristotle University of Thessaloniki - 54124 Thessaloniki - Greece.

2 Department of Meteorology-Climatology, School of Geology, Faculty of Sciences, Aristotle University of Thessaloniki - 54124 Thessaloniki - Greece.

Abstract: In steady-state methods for estimating energy consumption of buildings, the commonly used data include the monthly average dry bulb temperatures, the heating and cooling degree-days and the dry bulb temperature bin data. This work presents average values of these data for the 1983-1992 and 1993-2002 decades, calculated for Athens and Thessaloniki, determined from hourly dry bulb temperature records of meteorological stations (National Observatory of Athens and Aristotle University of Thessaloniki). The results show that the monthly average dry bulb temperatures and the annual average cooling degree-days of the 1993-2002 decade are increased, compared to those of the 1983-1992 decade, while the corresponding annual average heating degree-days are reduced. Also, the low temperature bins frequency results decreased in the 1993-2002 decade while the high temperature ones increased, compared to the 1983-1992 decade. The effect of temperature data variations on the energy consumption and on CO₂ emissions of buildings was examined by calculating the energy demands for heating and cooling and the CO₂ emissions from diesel-oil and electricity use of a typical residential building-model. From the study it is concluded that the heating energy requirements during the decade 1993-2002 were decreased, as compared to the energy demands of the decade 1983-1992, while the cooling energy requirements were increased. The variations of CO₂ emissions from diesel oil and electricity use were analog to the energy requirements alterations. The results indicate a warming trend, at least for the two regions examined, which affect the estimation of heating and cooling demands of buildings. It, therefore, seems obvious that periodic adaptation of the temperature data used for building energy studies is required.

6. Design and development of major balance of plant components in solid oxide fuel cell system

Wen-Tang Hong¹, Tzu-Hsiang Yen², Cheng-Nan Huang¹, Hsueh-I Tan¹, Yu Chao¹

1 Institute of Nuclear Energy Research Atomic Energy Council, Taoyuan County 32546, Taiwan, ROC.

2 Green Technology Research Institute, CPC Corporation, Chia-Yi City 60036, Taiwan, ROC.

Abstract: The balance of plant (BOP) of a Solid Oxide Fuel Cell (SOFC) system with a 2 kW stack and an electric efficiency of 40% is optimized using commercial GCTool software. The simulation results provide a detailed understanding of the optimal operating temperature, pressure and mass flow rate in all of the major BOP components, i.e., the gas distributor, the afterburner, the reformer and the heat exchanger. A series of experimental trials are performed to validate the simulation results. Overall, the results presented in this study not only indicate an appropriate set of operating conditions for the SOFC power system, but also suggest potential design improvements for several of the BOP components.

7. Estimation of emissions of nonmethane organic compounds from a closed landfill site using a landfill gas emission model

A. N. Nwachukwu¹, A. W. Diya²

1 Williamson Research Centre for Molecular Environmental Sciences, School of Earth, Atmospheric and Environmental Science, University of Manchester M13 9PL, UK.

2 Health Sciences Research Group, School of Medicine, University of Manchester M13 9PL, UK.

Abstract: Nonmethane organic compounds (NMOC) emissions from landfills often constitute significant risks both to human health and the general environment. To date very little work has been done on tracking the emissions of NMOC from landfills. To this end, a concerted effort was made to investigate the total annual mass emission rate of NMOC from a closed landfill site in South Manchester, United Kingdom. This was done by using field estimates of NMOC concentration and the landfill parameters into the Landfill Gas Emission Model embedded in ACTS and RISK software. Two results were obtained: (i) a deterministic outcome of 1.7218 x 10-7 kg/year, which was calculated from mean values of the field estimates of NMOC concentration and the landfill parameters, and (ii) a probabilistic outcome of 1.66 x 10-7 - 1.78 x 10-7 kg/year, which is a range of value obtained after Monte Carlo simulation of the uncertain parameters of the landfill including NMOC concentration. A comparison between these two results suggests that the probabilistic outcome is a more representative and reliable estimate of the total annual mass emission of NMOC especially given the variability of the parameters of the model. Moreover, a comparison of the model result and the safety standard of 5.0 x 10-5 kg/year indicate that the mass emission of NMOC from the studied landfill is significantly less than previously thought. However, given that this can accumulate to a dangerous level over a long period of time (such as the age of this landfill site); it may have started affecting the health of the people living within the vicinity of the landfill. A case is therefore made for more studies to be carried out on the emissions of other gases such as CH₄ and CO₂ from the studied landfill site, as this would help to understand the synergistic effect of the various gases being emitted from the landfill.

8. Exergoeconomic performance optimization for a steady-flow endoreversible refrigeration model including six typical cycles

Lingen Chen, Xuxian Kan, Fengrui Sun, Feng Wu

College of Naval Architecture and Power, Naval University of Engineering, Wuhan 430033, P. R. China.

Abstract: The operation of a universal steady flow endoreversible refrigeration cycle model consisting of a constant thermal-capacity heating branch, two constant thermal-capacity cooling branches and two adiabatic branches is viewed as a production process with exergy as its output. The finite time exergoeconomic performance optimization of the refrigeration cycle is investigated by taking profit rate optimization criterion as the objective. The relations between the profit rate and the temperature ratio of working fluid, between the COP (coefficient of performance) and the temperature ratio of working fluid, as well as the optimal relation between profit rate and the COP of the cycle are derived. The focus of this paper is to search the compromised optimization between economics (profit rate) and the utilization factor (COP) for endoreversible refrigeration cycles, by searching the optimum COP at maximum profit, which is termed as the finite-time exergoeconomic performance bound. Moreover, performance analysis and optimization of the model are carried out in order to investigate the effect of cycle process on the performance of the cycles using numerical example. The results obtained herein include the performance characteristics of endoreversible Carnot, Diesel, Otto, Atkinson, Dual and Brayton refrigeration cycles.

9. An innovative roofing system for tropical building interiors: Separating heat from useful visible light

Al-Obaidi K.M., Ismail M., Abdul Rahman A.M.

School of Housing, Building & Planning, Universiti Sains Malaysia, 11800, Minden, Pulau Pinang, Malaysia.

Abstract: Generally it has been known that energy consumption costs are high in temperate countries. In buildings, room spaces are normally designed so as to consume less energy for thermal comfort especially in winter. Passive strategies such large double-glazing windows are to contain heat indoors and also for maximum daylight to reduce dependence on artificial lighting. Thus roof lights are popular building design elements in cold and temperate countries. Unlike in the tropics where it has high temperatures and humidity throughout the year, achieving indoor comfort is a challenge especially with plenty of sunshine and unpredictable wind conditions. This paper explores the possibility of roof light for indoor comfort to be considered as a tropical design element. Initial simulation was carried out before any attempt to do life-sized model for empirical data. By simulation, the hypothesis has been achieved but several factors have to be considered. The solution is not as simple as those achieved in the temperate countries. Comfort can be achieved but permutations of several design factors such as dimensions of room, glazing, reflective materials, blackbody concept and building materials need adjustment to meet the Malaysian Comfort Temperature. With this finding the Tropical Architecture would then be redefined with the introduction of this Innovative Roofing System (IRS) as named by the author.

10. An investigation of standby energy losses in residential sector: Solutions and policies

Parmal Singh Solanki¹, Venkateswara Sarma Mallela², Chengke Zhou³

1 Caledonian (University) College of Engineering, Muscat, Oman.

2 G. Narayanamma Institute of Technology and Science (for Women), Hyderabad, India.

3 Glasgow Caledonian University, Glasgow, Scotland, UK.

Abstract: This paper investigates the standby power losses of household appliances and determines these losses by field measurements and bottom-up approaches. It is revealed that average standby power losses of e-appliances at household in Oman is 103.4 Watts and could further increase if other miscellaneous appliances are also taken into account. Calculations show that TV sets alone are responsible to consume 1.89 MW standby powers across the country. The paper considers various technological and socio-economic options to diminish the standby power consumption and signify that 42.72% of energy consumed by appliances can be saved by end-users implementing suitable measures. Energy management programmes like energy efficiency standards, labelling and policy instruments to tackle the standby power losses are also discussed. Finally, paper looks into the barriers and their way-outs to implement the energy efficiency standards and labelling.

11. A study on metal organic framework (MOF-177) synthesis, characterization and hydrogen adsorption -desorption cycles

V.Viditha¹, M.Venkateswer Rao¹, K.Srilatha1¹, V.Himabindu¹_, Anjaneyulu Yerramilli²

1 Centre for Environment, Institute of Science and Technology, Jawaharlal Nehru Technological University Hyderabad, Kukatpally, Hyderabad-500 085, A.P, India.

2 Director, TLGVRC, JSU Box 18739, JSU, Jackson, MS32917-0939, USA.

Abstract: Hydrogen has long been considered to be an ideal alternative to fossil-fuel systems and much work has now been done on its storage. There are four main methods of hydrogen storage: as a liquid; as compressed hydrogen; in the form of metal hydrides; and by physisorption. Among all the materials metal organic frameworks (MOFs) are considered to have desirable properties like high porosity, pore volume and high thermal stability. MOF-177 is considered to be an ideal storage material. In this paper we study about its synthesis and hydrogen storage capacities of MOF-177 at different pressures ranging from 25, 50, 75 and 100 bar respectively. The obtained samples are characterized by XRD, BET and SEM. The recorded results show that the obtained hydrogen capacity is 1.1, 2.20, 2.4 and 2.80 wt%. The desorption capacity is 0.9, 2.1, 2.37 and 2.7 wt% at certain temperatures like 373 K.

12. Convective heat transfer from a heated elliptic cylinder at uniform wall temperature

Kaprawi S., Dyos Santoso

Mechanical Department of Sriwijaya University, Jl. Raya Palembang-Prabumulih Km. 32 Inderalaya 50062 Ogan Ilir, Indonesia.

Abstract: This study is carried out to analyse the convective heat transfer from a circular and an elliptic cylinders to air. Both circular and elliptic cylinders have the same cross section. The aspect ratio of cylinders range 0-1 are studied. The implicit scheme of the finite difference is applied to obtain the discretized equations of hydrodynamic and thermal problem. The Choleski method is used to solve the discretized hydrodynamic equation and the iteration method is applied to solve the discretized thermal equation. The circular cylinder has the aspect ratio equal to unity while the elliptical cylinder has the aspect ratio less than unity by reducing the minor axis and increasing the major axis to obtain the same cross section as circular cylinder. The results of the calculations show that the skin friction change significantly, but in contrast with the elliptical cylinders have greater convection heat transfer than that of circular cylinder. Some results of calculations are compared to the analytical solutions given by the previous authors.

13. Flood moderation by large reservoirs in the humid tropics of Western ghat region of Kerala, India

George Abe¹, E. J. James²

1 Centre for Water Resources Development and Management, Sub Centre, Kottayam South P.O, Kottayam-686 039, Kerala, India.

2 Water Institute & Dean (Research), Karunya University, Coimbatore-641 114, Tamil Nadu, India.

Abstract: Kerala State located in the humid tropics receives an average rainfall of 2810 mm. On an average 85% of this rainfall is received during the two monsoons spread from June to November. Midland and lowland regions of several of the river basins of Kerala experience severe flood events during the monsoons. Idamalayar hydro-electric project (1987) in Periyar River basin envisages flood control apart from power generation. This paper analyzes the flood moderation by Idamalayar reservoir considering the storage regime (inflow and outflow) which is subjected to a strong inter annual variability. The role of Idamalayar reservoir in controlling the monsoon floods is analyzed using daily data (1987-2010). The results of analysis show that the flood moderation by the reservoir is 92% when water storage is less than 50%. The reduction is 87% when reservoir storage is between 50 to 90% and moderation reduces to 62 % when the reservoir storage is above 90%. Non-parametric trend analysis of fifty years of hydrologic data shows a reducing trend in inflow and storage during south-west monsoon which reduced spill and subsequent flood events during north-east monsoon.

14. Production of bio-gas from maize cobs

Luter Leke^{1, 2}, Anne Ada Ogbanje^{2, 3}, Dekaa Henry Terfa², Tyoalumun Ikyaagba¹

1 College of Physical Sciences, University of Aberdeen, AB24 3UE, Aberdeen - UK.

2 Department of Chemistry, Benue State University, P M B 102119, Makurdi, Nigeria.

3 Department of Renewable Energy, Energy Commission of Nigeria, Garki-Abuja, Nigeria.

Abstract: Anaerobic digestion of energy crop residues and wastes is of increasing interest in order to reduce greenhouse gas emissions and to facilitate a sustainable development of energy supply. Production of biogas provides a versatile carrier of renewable energy, as methane can be used for replacement of fossil fuels in both heat and power generation as vehicle fuel. Biogas fuel production from blends of biological wastes such as Cow rumen liquor (CL), Poultry droppings (PD), and Goat Faeces (GF) with Maize cobs (M) were studied. 20 g of each inoculum was mixed with 100g of degraded maize cobs in the first three digesters while the fourth contained CL 10g, PD 10 g, and M 100 g. 100 g of M alone in the fifth digester served as the control. The blends were subjected to anaerobic digestion for 10 days on the prevailing atmospheric ambient temperature and pressure conditions. Physiochemical properties of the blends such as moisture content, crude protein, ash, fat, crude fibre, carbohydrate content, C/N ratio, and pH were also determined. Results of the daily performances of each system showed that maize cobs (M) alone had cumulative biogas yield of 1.50 cm3 while those of the blends (MCL, MPD, MGF and MCLPD) were 6.11 cm3, 3.05 cm3, 2.50 cm3, and 63.00 cm3 respectively, pH and C/N ratio affected the biogas yield of the systems significantly. These results indicate that the low biogas production from maize cobs can be enhanced significantly by blending with cow rumen liquor and poultry droppings.

15. Thermodynamic analysis of a thermally operated cascade sorption heat pump for continuous cold generation

P. Muthukumar, D.V.N. Lakshmi

Department of Mechanical Engineering, Indian Institute of Technology, Guwahati – 781039, India.

Abstract: In this paper, the thermodynamic analysis of a cascade sorption system consists of a two-stage metal hydride heat pump as topping cycle and a single-stage lithium bromide water system as bottom cycle is presented. The effects of various operating temperatures such as driving heat, heat release and refrigeration temperatures, and design parameters such as ratio of metal hydride mass to reactor mass and sensible heat exchange factor on the combined coefficient of performance (COP) of the cascade cycle, and specific cooling power (SCP) and total cold output of the metal hydride heat pump cycle are presented. It is observed that the combined COP is found to increase with heat release and refrigeration temperatures and however, decreases with driving heat temperature. Increase of sensible heat exchange factor improves the system performances significantly. Reduction in mass ratio from 0.5 to 0.1 improves the combined COP of the cascade system by about 10 %. The maximum predicted combined COP of the system is about 1.66 at the driving heat, heat release and refrigeration temperatures of 270 °C, 125 °C and 12°C, respectively.