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Aims and Scope
Editorial Board

1. Heat rate curve approximation for power plants without data measuring devices

Andreas Poullikkas

Electricity Authority of Cyprus, P.O. Box 24506, 1399 Nicosia, Cyprus.

Abstract: In this work, a numerical method, based on the one-dimensional finite difference technique, is proposed for the approximation of the heat rate curve, which can be applied for power plants in which no data acquisition is available. Unlike other methods in which three or more data points are required for the approximation of the heat rate curve, the proposed method can be applied when the heat rate curve data is available only at the maximum and minimum operating capacities of the power plant. The method is applied on a given power system, in which we calculate the electricity cost using the CAPSE (computer aided power economics) algorithm. Comparisons are made when the least squares method is used. The results indicate that the proposed method give accurate results.

Volume 3, Issue 5, 2012, pp.651-658.

2. Estimation of clear sky hourly global solar radiation in Iraq

Kais J. Al-Jumaily, Munya F. Al-Zuhairi, Zahraa S. Mahdi

Department of Atmospheric Sciences, College of Science, Al-Mustansiriyah University, Baghdad, Iraq.

Abstract: The availability of hourly solar radiation data is very important for applications utilizing solar energy and for climate and environmental aspects. The aim of this work is to use a simple model for estimating hourly global solar radiation under clear sky condition in Iraq. Calculations were compared with measurements obtained from local station in Baghdad city and from Meteosat satellite data for different locations in Iraq. The statistical test methods of the mean bias error (MBE), root mean square error (RMSE) and t-test were used to evaluate the performance of the model. Results indicated that a fairly good agreement exists between calculated and measured values for all locations in Iraq. Since the model is independent of any meteorological variable, it would be of a practical use for rural areas where no meteorological data are available.

3. Increasing energy efficiency of HVAC systems of buildings using phase change material

Lee Chusak, Jared Daiber, Ramesh Agarwal

Department of Mechanical Engineering and Materials Science, Washington University in St. Louis, St. Louis, MO 63130, USA.

Abstract: Using Computational Fluid Dynamics (CFD), four different cooling systems used in contemporary office environments are modeled to compare energy consumption and thermal comfort levels. Incorporating convection and radiation technologies, full-scale models of an office room compare energy efficiency of (a) an all-air overhead system, (b) a combined all-air overhead and hydronic radiant system (chilled ceiling), (c) an all-air raised floor system (displacement ventilation), and (d) a combined displacement ventilation with a chilled ceiling. The computational domain for each model consists of one temperature varying wall (simulating the temperature of the exterior wall of the building during a 24-hour period) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations are conducted. The first set considers a glass window and plastic shade configuration for the exterior wall. The second set of computations includes a phase change material layer between the glass window and the plastic shade. Results show substantial energy savings can be accrued using the displacement ventilation and especially the displacement ventilation with a chilled ceiling over the conventional overhead mixing ventilation system. The results also show that the addition of a PCM layer to the exterior wall can significantly decrease the cooling energy requirements.

4. Evaluation of solar radiation abundance and electricity production capacity for application and development of solar energy

Mustamin Rahim^1,2, Jun Yoshino², Takashi Yasuda²

1 Department of Architecture, Khairun University, Ternate, Indonesia.

2 Environmental and Renewable Energy Systems Division, Graduate School of Engineering, Gifu University, Japan.

Abstract: This study was undertaken to analyze solar radiation abundance to ascertain the potential of solar energy as an electrical energy resource. Local weather forecasting for predicting solar radiation is performed using a meteorological model MM5. The prediction results are compared with observed results obtained from the Japan Meteorological Agency for verification of the data accuracy. Results show that local weather forecasting has high accuracy. Prediction of solar radiation is similar with observation results. Monthly average values of solar radiation are sufficiently good during March–September. Electrical energy generated by photovoltaic cells is almost proportional to the solar radiation amount. Effects of clouds on solar radiation can be removed by monthly averaging. The balance between supply and demand of electricity can be estimated using a standard curve obtained from the temporal average. When the amount of solar radiation every hour with average of more than 100 km radius area does not yield the standard curve, we can estimate the system of storage and auxiliary power necessary based on the evaluated results of imbalance between supply and demand.

5. Parametric analysis of geothermal residential heating and cooling application

Zoi N. Sagia, Athina B. Stegou, Constantinos D. Rakopoulos

National Technical University of Athens, School of Mechanical Engineering, Department of Thermal Engineering, Heroon Polytechniou 9, 15780, Zografou, Attiki, Greece.

Abstract: A study is carried out to evaluate the efficiency of a Ground Source Heat Pump (GSHP) system with vertical heat exchangers applied to a three-storey terraced building, with total heated area 271.56 m2, standing on Hellinikon, Athens. The estimation of building loads is made with TRNSYS 16.1 using climatic data calculated by Meteonorm 6.1. The GSHP system is modeled with two other packages GLD 2009 and GLHEPRO 4.0. A comparison of the mean fluid temperature (fluid temperature in the borehole calculated as the average of exiting and entering fluid temperature), computed by above software, shows how close the results are. In addition, a parametric analysis is done to examine the influence of undisturbed ground temperature, ground heat exchanger (GHE) length and borehole separation distance to system’s operational characteristics so as to cover building loads. Finally, a 2D transient simulation is performed by means of COMSOL Multiphysics 4.0a. The carrier fluid in the borehole is modeled as a solid with extremely high thermal conductivity, extracting from and injecting to the ground the hourly load profile calculated by TRNSYS. The mean fluid temperature and the borehole wall temperature are computed for an entire year and compared with the values calculated by GLD.

6. Exergy analysis for combined regenerative Brayton and inverse Brayton cycles

Zelong Zhang, Lingen Chen, Fengrui Sun

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

Abstract: This paper presents the study of exergy analysis of combined regenerative Brayton and inverse Brayton cycles. The analytical formulae of exergy loss and exergy efficiency are derived. The largest exergy loss location is determined. By taking the maximum exergy efficiency as the objective, the choice of bottom cycle pressure ratio is optimized by detailed numerical examples, and the corresponding optimal exergy efficiency is obtained. The influences of various parameters on the exergy efficiency and other performances are analyzed by numerical calculations.

7. Production of hydrogen using composite membrane in PEM water electrolysis

E.L.Santhi priya¹, C.Mahender¹, Naga Mahesh¹, V.Himabindu¹, Y.Anjaneyulu²

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: Electrolysis of water is the best known technology till today to produce hydrogen. The only practical way to produce hydrogen using renewable energy sources is by proton exchange membrane (PEM) water electrolysis. The most commonly used PEM membrane is Nafion. Composite membrane of TiO₂ is synthesized by casting method using Nafion 5wt% solution. RuO₂ is used as anode and 10 wt% Pd on activated carbon is used as cathode in the water electrolyser system. The performance of this Composite membrane is studied by varying voltage range 1.8 to 2.6V with respect to hydrogen yield and at current density 0.1, 0.2, 0.3, 0.4, and 0.5(A cm^-2). This Composite membrane has been tested using in-house fabricated single cell PEM water electrolysis cell with 10cm² active area at temperatures ranging from 30,45,65 850c and at 1 atmosphere pressure.

8. Experimental study of passive cooling of building facade using phase change materials to increase thermal comfort in buildings in hot humid areas

A. A. Madhumathi¹, B. M.C. Sundarraja²

1 Department of Architecture, Thiagarajar College of Engineering, Madurai-15, Tamilnadu, India.

2 Department of Civil Engineering, Thiagarajar College of Engineering, Madurai-15, Tamilnadu, India.

Abstract: Storage of cooler night temperatures using Phase Change Material (PCM) energy storage technique, for cooling of ambient air during hot day times can be an alternate of current cooling techniques in building sector. This work presents the results of an experimental set-up to test energy saving potential of phase change materials with typical construction materials in building facade in Hot-Humid Climatic Regions in real conditions. The main objective of this research is to demonstrate experimentally that it is possible to improve the thermal comfort and reduce the energy consumption of a building without substantial increase in the weight of the construction materials with the inclusion of PCM. This research was conducted to study and evaluate the performance of the existing materials integrated with Organic PCM Polyethylene glycol (PEG) E600. This research suggested that the heat gain is significantly reduced when the PCM is incorporated into the brick (conventional building material).

9. A new technology proposed to recycle waste plastics into hydrocarbon fuel in USA

Moinuddin Sarker, Mohammad Mamunor Rashid, Mohammed Molla, Muhammad Sadikur Rahman

Department of Research and Development, Natural State Research Inc, 37 Brown House Road (2^nd Floor), Stamford, CT-06902, USA.

Abstract: Energy crisis and environmental degradation by polymer wastes have been imperative to find and propose technologies for recovery of raw materials and energy from non-conventional sources like plastic wastes. A variety of methods and processes connected with global or national policies have been proposed worldwide. A new type of steel reactor is proposed for conversion of waste plastics to fuel like mixture of hydrocarbons. The results of the thermal degradation of waste plastics in the laboratory scale set-up based on this process in the paper. The melting and thermal cracking processes were carried out in a single batch process at the temperature range is 200–420 ºC. The final product consisted of light gas 6.3 % and liquid product 90%. 3.7% solid black products were produced. The light, ‘‘gas” fraction of the hydrocarbons mixture (C₁–C₄) and rest of liquid fuel made over 90% of the liquid product. It may be used for fuel production refinery or electricity generation.

10. The potential of macroalgae as a source of carbohydrates for use in bioethanol fermentation

Nwachukwu A. N¹, Chukwu M. A.²

¹ School of Earth, Atmospheric and Environmental Sciences, University of Manchester, UK.

² Department of Sustainable Chemical Engineering, University of Newcastle Upon Tyne, UK.

Abstract: Fossil fuel which is the global energy source gives rise to land contamination, air pollution, climate change, fuel crises, hike of price of petroleum products, crises in oil producing nations, dependency on oil producing countries and high risk associated with oil exploitation has led to a search for sustainable and efficient energy sources. Several types and sources of biofuels have been recently studied as potential source of energy to replace the environmentally unfriendly fossil fuels. Bioethanol produced from terrestrial plants have attracted the attention of the global society, though numerous controversies and debates were associated with the technology; such as the issue of food versus fuel competition, which further encouraged more research work on a sustainable renewable bioethanol source. This study aims at determining total carbohydrates from macroalgal specie (Laminaria digitata) for use in bioethanol fermentation, also using wet and analytical chemistry to extract and spectrophotometrically analyse the sample in respect to glucose and sucrose standards. The samples were lyophilized and the resulting powder extracted in a water bath at 100oC in 15minutes. The analysis was performed using anthrone (colorimetric) method and the analyte read in a UV-visible spectrophotometer at 620nm. The result showed that carbohydrates were present in the samples, indicated by green and yellow, colourless pigments. Glucose and sucrose were the main identified sugars from the standards analysed. The concentration of sugars varied with time; months and seasons of the year. Result of the samples showed highest level of sugar concentration in May 2010 and lowest sugar concentration in November 2010. It was observed that the mass of sugars (glucose and sucrose) deposited as a result of photosynthesis, significantly contributed to the weight of biomass. The implication of the result indicated that: the smaller the biomass, the most likely it is to have lower mass of sugars and hence the less likely the potentials of synthesizing bioethanol from the sample. Conversely, a larger biomass signified the presence of more sugars, hence the greater the potentials for synthesis of bioethanol from the sample with larger biomass.

11. A method based on neural networks for generating solar radiation map

Z. Ramedani, M. Omid, A. Keyhani

Department of Agricultural Machinery Engineering, Faculty of Agricultural Engineering and Technology, University of Tehran, Karaj, Iran.

Abstract: Estimation of global solar radiation (GSR) is important in most solar energy applications, particularly in design methods, in system characterization and in decision making for energy management. In this paper, a new methodology based on artificial neural networks (ANN) for generating daily GSR data is presented. By modeling GSR in regions where historical records are available, solar potential map for other sites that GSR have not been recorded was generated. In order to examine the ANN models, meteorological data throughout the year 2008 belonging to Karaj city in Alborz province of Iran were used to develop GSR predictors. Input parameters were maximum temperature, relative sunshine duration and extraterrestrial solar radiation while the output parameter was the solar radiation. Various networks were designed and tested and the most accurate model was selected. The best network was found as one hidden layer network with 3-4-1 topology, i.e., a network having four neurons in its hidden layer. To estimate the differences between the measured and predicted values, root mean square error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE) and coefficient of determination (R2) were computed as0.66, 0.52, 4.46% and 0.978, respectively. The optimum ANN model was then used to predict GSR in other cities in the province. Data from three stations located in Hashtgerd, Taleghan and Chitgar cities were used as production set. The GSR values for production sites of Hashtgerd, Taleghan and Chigrar were calculated as 4.93, 4.35 and 5.08 kWh m-2 day-1, respectively. Finally, the predicted solar potential values in all stations were integrated and represented in the form of a map. While results are site-specific, the methodology introduced here is general and provides an inexpensive means for GSR prediction based on readily available data.

12. Finite difference approach on magnetohydrodynamic flow and heat transfer in a viscous incompressible fluid between two parallel porous plates

S. S. Das1, M. Mohanty2, R. K. Padhy3, M. Sahu4

1 Department of Physics, KBDAV College, Nirakarpur, Khordha-752 019 (Odisha), India.

2 Department of Physics, Christ College, Mission Road, Cuttack-753 001 (Odisha), India.

3 Department of Physics, DAV Public School, Chandrasekharpur, Bhubaneswar-751 021(Odisha), India.

4 Department of Physics, Jupiter +2 Women’s Sc. College, IRC Village, Bhubaneswar-751 015(Odisha), India.

Abstract: This paper considers the magnetohydrodynamic flow and heat transfer in a viscous incompressible fluid between two parallel porous plates experiencing a discontinuous change in wall temperature. An explicit finite difference scheme has been employed to solve the coupled non-linear equations governing the flow. The flow phenomenon has been characterized by Hartmann number M, suction Reynolds number R, channel Reynolds number R* and Prandtl number Pr. The effects of these parameters on the velocity and temperature distribution have been analyzed and the results are presented with the aid of figures. It is observed that a growing suction parameter R retards the velocity of the flow field both in MHD (M not equal 0) as well as non-MHD (M = 0) flow. The effect of increasing Hartmann number M is to decrease the transverse component of velocity for both suction (R greater than 0) and injection (R grater than 0) and in absence of suction and injection (R = 0), while it decreases the axial component of velocity up to the middle of the channel and beyond this the effect reverses. There is a sharp fluctuation in temperature near the walls and at the middle of the channel which may be attributed to the discontinuous change in wall temperature. For fluids having low Prandtl number such as air (Pr = 0.71), the temperature assumes negative values.

13. Drying of Leaves of Tendu (Diospyros melonoxylon) plants using a solar dryer with mirror booster

S. P. Singh¹, Biplab Paul²

1 School of Energy and Environmental Studies (SEES), Devi Ahilya Vishwavidyalaya (DAVV), Indore, MP, India.

2 Gyan Ganga Institute of Technology and Sciences, Jabalpur, MP, India.

Abstract: A laboratory solar dryer with mirror booster was designed and developed for drying Tendu (Diospyros melonoxylon) under the climatic condition (Composite Climate Zone) of Malwa region, Indore (Latitude-22.44 ^oN, Longitude-75.5 ^oE) of Madhya Pradesh, India. The Mirror booster solar dryer consist of an integrated collector and drying chamber enclosed. The aluminium drying chamber fitted with one fan operated by a photovoltaic module is placed inside the collector with glazed top, east, west and south wall. The bottom and north wall of the dryer was kept insulated. A door is provided to load and unload material in trays from the north side. The experiment result shows that the drying time reduction of Tendu leaves was nearly 75% in comparison to open sun drying. The maximum and minimum time of drying was found be 18 hours and 12 hours for 15 bundles of tendu leaves.

14. Squeal analysis of ventilated disc brake using ansys

Ahmed Abdel-Naser¹, Ibrahim Ahmed², Essam Allam¹, Sabry Allam², Shawki Abouel-seoud¹

1 Automotive and Tractors Engineering Department., Faculty of Engineering, Helwan University, Cairo, Egypt.

2 Automotive and Tractors Technology Department, Faculty of Industrial Education, Helwan University, Cairo, Egypt.

Abstract: It is well-known that automobile brakes can generate several kinds of noises. Among them is squeal, a noise in the 1-15 kHz range. It is commonly accepted that brake squeal is initiated by instability due to the friction forces, leading to self excited vibrations. To predict the onset of brake instability, a modal analysis of the prestressed structure can be performed on an improved dynamic finite element model of ventilated disc brake with friction coupling. An unsymmetric stiffness matrix is a result of the friction coupling between the brake pad and disc; this may lead to complex eigenfrequencies. The complex eigenvalue method (Unsymmetric solver) used to analyse mode shapes associated with the predicted natural frequency. Creating the element of Matrix27 between the ventilated disc and pad was very important in studying the squeal of the coupled ventilated disc brake. The results demonstrated that the FEM for the coupled ventilated rotor and pad showed a good interaction between the non-linear contact and the linear modal analysis. Furthermore, the unsymmetric solver showed that the modes of the coupled disc-pad contained two types of mode. The first type was normal mode, which did not contain an imaginary part while the second type was complex mode that contained real and imaginary parts. Moreover, complex eigenvalue analysis predicted always more unstable modes than the number of squeal frequencies that really occur in the brake system. The maximum squeal index was observed at mode 16 and at frequency of 4083 Hz with instability of 480 sec-1. However; the tendency of instability (TOI) for the system at contact stiffness of 1 GN/m was 59 that gave the lowest instability of the system.