Journal of Energy http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Briquetting of Charcoal from Sesame Stalk Tue, 25 Aug 2015 09:07:00 +0000 http://www.hindawi.com/journals/jen/2015/757284/ Due to the easy availability of wood in Ethiopia, wood charcoal has been the main source fuel for cooking. This study has been started on sesame stalk biomass briquetting which can potentially solve the health problems and shortage of energy, which consequently can solve deforestation. The result of the data collection shows that, using 30% conversion efficiency of carbonizer, it was found that more than 150,000 tonnes of charcoal can be produced from the available sesame stalk in Humera, a place in north Ethiopia. The clay binders that are mixed with carbonized sesame stalk were found to have 69 liquid limits; thus, the optimum amount of clay that should be added as a binder is 15%, which results in better burning and heat holding capacity and better heating time. The developed briquetting machine has a capacity of producing 60 Kg/hr but the carbonization kiln can only carbonize 3.1 Kg in 2 : 40 hours; hence, it is a bottle neck for the briquette production. The hydrocarbon laboratory analysis showed that the calorific value of the charcoal produced with 15% clay content is 4647.75 Cal/gm and decreases as clay ratio increases and is found to be sufficient energy content for cooking. Alula Gebresas, Haftom Asmelash, Hadush Berhe, and Tsegay Tesfay Copyright © 2015 Alula Gebresas et al. All rights reserved. The Effects of Air Preheating and Fuel/Air Inlet Diameter on the Characteristics of Vortex Flame Thu, 14 May 2015 16:25:08 +0000 http://www.hindawi.com/journals/jen/2015/397219/ The effects of fuel/air inlet diameter as well as air preheating on the flame stability, temperature distribution, pollutant formation, and combustion characteristics of a lab-scaled asymmetric vortex flame have been investigated. A three-dimensional steady-state finite volume solver has been used to solve the governing and energy equations. The solver uses a first-order upwind scheme to discretize the governing equations in the space. The semi-implicit method for pressure linked equations has been applied to couple the pressure to the velocity terms. Several turbulence models were applied to predict the flame temperature and it was found that RNG has given the best results in accordance with the experimental results. The results reveal that the inlet air diameter can enhance the thermal properties and reduce the emission while the inlet fuel diameter has less significant impact. Increasing diameters are accompanied with a pressure drop. It was found that preheating the air and fuel would significantly affect the flame temperature and emission with constant mass flow rate. Mostafa Khaleghi, S. E. Hosseini, M. A. Wahid, and H. A. Mohammed Copyright © 2015 Mostafa Khaleghi et al. All rights reserved. A Subspace Identification Method for Detecting Abnormal Behavior in HVAC Systems Wed, 11 Mar 2015 16:39:02 +0000 http://www.hindawi.com/journals/jen/2015/693749/ A method for the detection of abnormal behavior in HVAC systems is presented. The method combines deterministic subspace identification for each zone independently to create a system model that produces the anticipated zone’s temperature and the sequential test CUSUM algorithm to detect drifts of the rate of change of the difference between the real and the anticipated measurements. Simulation results regarding the detection of infiltration heat losses and the detection of exogenous heat gains such as fire demonstrate the effectiveness of the proposed method. Dimitris Sklavounos, Evangelos Zervas, Odysseas Tsakiridis, and John Stonham Copyright © 2015 Dimitris Sklavounos et al. All rights reserved. Flexible Mode Control of Grid Connected Wind Energy Conversion System Using Wavelet Sat, 28 Feb 2015 07:12:34 +0000 http://www.hindawi.com/journals/jen/2015/152898/ Small wind turbine systems offer services to critical loads during grid faults and also connected back to grid in normal condition. The connection of a wind energy conversion system to the grid requires a robust phase locked loop (PLL) and continuous monitoring of the grid conditions such as overvoltage, undervoltage, overfrequency, underfrequency, and grid outages. This paper describes a flexible control operation to operate a small wind turbine in both stand-alone mode via planned islanding and grid connected mode as well. In particular, a proper monitoring and control algorithm is required for transition between the modes. A wavelet based energy function is used for detection of grid disturbances as well as recovery of grid so that transition between the modes is made. To obtain good power quality LCL filter is used to reduce ripples. PLL is used for synchronization whenever mode changes from stand-alone to grid connected. Simulation results from a 10 kW wind energy conversion system are included to show the usefulness of the proposed methods. The control method is tested by generated gate pulses for single phase bridge inverter using field programmable gate array (FPGA). Bhavna Jain, Sameer Singh, Shailendra Jain, and R. K. Nema Copyright © 2015 Bhavna Jain et al. All rights reserved. Midterm Electricity Market Clearing Price Forecasting Using Two-Stage Multiple Support Vector Machine Thu, 29 Jan 2015 15:29:04 +0000 http://www.hindawi.com/journals/jen/2015/384528/ Currently, there are many techniques available for short-term forecasting of the electricity market clearing price (MCP), but very little work has been done in the area of midterm forecasting of the electricity MCP. The midterm forecasting of the electricity MCP is essential for maintenance scheduling, planning, bilateral contracting, resources reallocation, and budgeting. A two-stage multiple support vector machine (SVM) based midterm forecasting model of the electricity MCP is proposed in this paper. The first stage is utilized to separate the input data into corresponding price zones by using a single SVM. Then, the second stage is applied utilizing four parallel designed SVMs to forecast the electricity price in four different price zones. Compared to the forecasting model using a single SVM, the proposed model showed improved forecasting accuracy in both peak prices and overall system. PJM interconnection data are used to test the proposed model. Xing Yan and Nurul A. Chowdhury Copyright © 2015 Xing Yan and Nurul A. Chowdhury. All rights reserved. Heat Transfer Enhancement and Hydrodynamic Characteristics of Nanofluid in Turbulent Flow Regime Thu, 29 Jan 2015 12:31:36 +0000 http://www.hindawi.com/journals/jen/2015/814717/ Turbulent forced convection of γ-Al2O3/water nanofluid in a concentric double tube heat exchanger has been investigated numerically using mixture two-phase model. Nanofluids are used as coolants flowing in the inner tube while hot pure water flows in outer tube. The studies are conducted for Reynolds numbers ranging from 20,000 to 50,000 and nanoparticle volume fractions of 2, 3, 4, and 6 percent. Results showed that nanofluid has no effects on fully developed length and average heat transfer coefficient enhances with lower slope than wall shear stress. Comparisons with experimental correlation in literature are conducted and good agreement with present numerical study is achieved. Mohammad Nasiri-lohesara Copyright © 2015 Mohammad Nasiri-lohesara. All rights reserved. Recovery of Exhaust Waste Heat for ICE Using the Beta Type Stirling Engine Sun, 18 Jan 2015 08:35:47 +0000 http://www.hindawi.com/journals/jen/2015/495418/ This paper investigates the potential of utilizing the exhaust waste heat using an integrated mechanical device with internal combustion engine for the automobiles to increase the fuel economy, the useful power, and the environment safety. One of the ways of utilizing waste heat is to use a Stirling engine. A Stirling engine requires only an external heat source as wasted heat for its operation. Because the exhaust gas temperature may reach 200 to 700°C, Stirling engine will work effectively. The indication work, real shaft power and specific fuel consumption for Stirling engine, and the exhaust power losses for IC engine are calculated. The study shows the availability and possibility of recovery of the waste heat from internal combustion engine using Stirling engine. Wail Aladayleh and Ali Alahmer Copyright © 2015 Wail Aladayleh and Ali Alahmer. All rights reserved. The Links between Energy Consumption, Financial Development, and Economic Growth in Lebanon: Evidence from Cointegration with Unknown Structural Breaks Sun, 18 Jan 2015 07:31:41 +0000 http://www.hindawi.com/journals/jen/2015/965825/ We investigate the relation between financial development, energy consumption, and economic growth in the economy of Lebanon over the period 2000M2–2010M12. Our findings confirm the existence of cointegration among the variables. The results indicate that financial development and energy consumption contribute to economic growth in Lebanon. The impact of energy consumption on economic growth is positive showing the significance of energy as a main stimulant of economic growth. Financial development is also found to play a vital role in enhancing economic growth. Financial development and economic growth also result in further increase in energy consumption. We offer some policy implications specific to Lebanon considering the recent discovery of large oil and gas reserves in the country and the historical importance of its banking sector which remains a center of Lebanon’s service-oriented economy. Salah Abosedra, Muhammad Shahbaz, and Rashid Sbia Copyright © 2015 Salah Abosedra et al. All rights reserved. Studies on Pyrolysis Kinetic of Newspaper Wastes in a Packed Bed Reactor: Experiments, Modeling, and Product Characterization Thu, 15 Jan 2015 07:06:20 +0000 http://www.hindawi.com/journals/jen/2015/618940/ Newspaper waste was pyrolysed in a 50 mm diameter and 640 mm long reactor placed in a packed bed pyrolyser from 573 K to 1173 K in nitrogen atmosphere to obtain char and pyro-oil. The newspaper sample was also pyrolysed in a thermogravimetric analyser (TGA) under the same experimental conditions. The pyrolysis rate of newspaper was observed to decelerate above 673 K. A deactivation model has been attempted to explain this behaviour. The parameters of kinetic model of the reactions have been determined in the temperature range under study. The kinetic rate constants of volatile and char have been determined in the temperature range under study. The activation energies 25.69 KJ/mol, 27.73 KJ/mol, 20.73 KJ/mol and preexponential factors 7.69 min−1, 8.09 min−1, 0.853 min−1 of all products (solid reactant, volatile, and char) have been determined, respectively. A deactivation model for pyrolysis of newspaper has been developed under the present study. The char and pyro-oil obtained at different pyrolysis temperatures have been characterized. The FT-IR analyses of pyro-oil have been done. The higher heating values of both pyro-products have been determined. Aparna Sarkar, Sudip De Sarkar, Michael Langanki, and Ranjana Chowdhury Copyright © 2015 Aparna Sarkar et al. All rights reserved. Feasibility Analysis and Simulation of Integrated Renewable Energy System for Power Generation: A Hypothetical Study of Rural Health Clinic Thu, 01 Jan 2015 14:21:50 +0000 http://www.hindawi.com/journals/jen/2015/802036/ This paper presents the feasibility analysis and study of integrated renewable energy (IRE) using solar photovoltaic (PV) and wind turbine (WT) system in a hypothetical study of rural health clinic in Borno State, Nigeria. Electrical power consumption and metrology data (such as solar radiation and wind speed) were used for designing and analyzing the integrated renewable energy system. The health clinic facility energy consumption is 19 kWh/day with a 3.4 kW peak demand load. The metrological data was collected from National Aeronautics and Space Administration (NASA) website and used to analyze the performance of electrical generation system using HOMER program. The simulation and optimization results show that the optimal integrated renewable energy system configuration consists of 5 kW PV array, BWC Excel-R 7.5 kW DC wind turbine, 24 unit Surrette 6CS25P battery cycle charging, and a 19 kW AC/DC converter and that the PV power can generate electricity at 9,138 kWh/year while the wind turbine system can generate electricity at 7,490 kWh/year, giving the total electrical generation of the system as 16,628 kWh/year. This would be suitable for deployment of 100% clean energy for uninterruptable power performance in the health clinic. The economics analysis result found that the integrated renewable system has total NPC of 137,139 US Dollar. The results of this research show that, with a low energy health facility, it is possible to meet the entire annual energy demand of a health clinic solely through a stand-alone integrated renewable PV/wind energy supply. Vincent Anayochukwu Ani and Bahijjahtu Abubakar Copyright © 2015 Vincent Anayochukwu Ani and Bahijjahtu Abubakar. All rights reserved. Structural and Thermal Analysis of Asphalt Solar Collector Using Finite Element Method Mon, 15 Dec 2014 08:11:37 +0000 http://www.hindawi.com/journals/jen/2014/602087/ The collection of solar energy using asphalt pavements has got a wide importance in the present energy scenario. Asphalt pavements subjected to solar radiation can reach temperature up to 70°C because of their excellent heat absorbing property. Many working parameters, such as pipe diameter, pipe spacing, pipe depth, pipe arrangement, and flow rate, influence the performance of asphalt solar collector. Existing literature on thermal energy extraction from asphalt pavements is based on the small scale laboratory samples and numerical simulations. In order to design an efficient asphalt solar collector there should be a payoff between the thermal and structural stability of the pavement, so that maximum heat can be absorbed without structural damage due to external load condition. This paper presents a combined thermal and structural analysis of asphalt solar collector using finite element method. Analysis is carried out in different models so as to obtain optimum pipe spacing, pipe diameter, depth, and pipe arrangement under the specified condition. Jinshah Basheer Sheeba and Ajith Krishnan Rohini Copyright © 2014 Jinshah Basheer Sheeba and Ajith Krishnan Rohini. All rights reserved. Does Climate Change Mitigation Activity Affect Crude Oil Prices? Evidence from Dynamic Panel Model Thu, 11 Dec 2014 00:10:16 +0000 http://www.hindawi.com/journals/jen/2014/514029/ This paper empirically investigates how climate change mitigation affects crude oil prices while using carbon intensity as the indicator for climate change mitigation. The relationship between crude oil prices and carbon intensity is estimated using an Arellano and Bond GMM dynamic panel model. This study undertakes a regional-level analysis because of the geographical similarities among the countries in a region. Regions considered for the study are Africa, Asia and Oceania, Central and South America, the EU, the Middle East, and North America. Results show that there is a positive relationship between crude oil prices and carbon intensity, and a 1% change in carbon intensity is expected to cause about 1.6% change in crude oil prices in the short run and 8.4% change in crude oil prices in the long run while the speed of adjustment is 19%. Jude C. Dike Copyright © 2014 Jude C. Dike. All rights reserved. Experimental Investigation of Thermal Characteristics of Kiwira Coal Waste with Rice Husk Blends for Gasification Wed, 19 Nov 2014 11:25:22 +0000 http://www.hindawi.com/journals/jen/2014/562382/ Eminent depletion of fossil fuels and environmental pollution are the key forces driving the implementation cofiring of fossil fuels and biomass. Cogasification as a technology is known to have advantages of low cost, high energy recovery, and environmental friendliness. The performance/efficiency of this energy recovery process substantially depends on thermal properties of the fuel. This paper presents experimental study of thermal behavior of Kiwira coal waste/rice husks blends. Compositions of 0, 20, 40, 60, 80, and 100% weight percentage rice husk were studied using thermogravimetric analyzer at the heating rate of 10 K/min to 1273 K. Specifically, degradation rate, conversion rate, and kinetic parameters have been studied. Thermal stability of coal waste was found to be higher than that of rice husks. In addition, thermal stability of coal waste/rice husk blend was found to decrease with an increase of rice husks. In contrast, both the degradation and devolatilization rates increased with the amount of rice husk. On the other hand, the activation energy dramatically reduced from 131 kJ/mol at 0% rice husks to 75 kJ/mol at 100% rice husks. The reduction of activation energy is advantageous as it can be used to design efficient performance and cost effective cogasification process. Deodatus Kazawadi, Geoffrey R. John, and Cecil K. King’ondu Copyright © 2014 Deodatus Kazawadi et al. All rights reserved. Effect of Flyash Addition on Mechanical and Gamma Radiation Shielding Properties of Concrete Sun, 16 Nov 2014 00:00:00 +0000 http://www.hindawi.com/journals/jen/2014/486093/ Six concrete mixtures were prepared with 0%, 20%, 30%, 40%, 50%, and 60% of flyash replacing the cement content and having constant water to cement ratio. The testing specimens were casted and their mechanical parameters were tested experimentally in accordance with the Indian standards. Results of mechanical parameters show their improvement with age of the specimens and results of radiation parameters show no significant effect of flyash substitution on mass attenuation coefficient. Kanwaldeep Singh, Sukhpal Singh, and Gurmel Singh Copyright © 2014 Kanwaldeep Singh et al. All rights reserved. Electricity Generation and Energy Cost Estimation of Large-Scale Wind Turbines in Jarandagh, Iran Thu, 13 Nov 2014 12:53:26 +0000 http://www.hindawi.com/journals/jen/2014/613681/ Currently, wind energy utilization is being continuously growing so that it is regarded as a large contender of conventional fossil fuels. This study aimed at evaluating the feasibility of electricity generation using wind energy in Jarandagh situated in Qazvin Province in north-west part of Iran. The potential of wind energy in Jarandagh was investigated by analyzing the measured wind speed data between 2008 and 2009 at 40 m height. The electricity production and economic evaluation of four large-scale wind turbine models for operation at 70 m height were examined. The results showed that Jarandagh enjoys excellent potential for wind energy exploitation in 8 months of the year. The monthly wind power at 70 m height was in the range of 450.28–1661.62 W/m2, and also the annual wind power was 754.40 W/m2. The highest capacity factor was obtained using Suzlon S66/1.25 MW turbine model, while, in terms of electricity generation, Repower MM82/2.05 MW model showed the best performance with total annual energy output of 5705 MWh. The energy cost estimation results convincingly demonstrated that investing on wind farm construction using all nominated turbines is economically feasible and, among all turbines, Suzlon S66/1.25 MW model with energy cost of 0.0357 $/kWh is a better option. Kasra Mohammadi, Ali Mostafaeipour, Yagob Dinpashoh, and Nima Pouya Copyright © 2014 Kasra Mohammadi et al. All rights reserved. A Novel Method for Detecting Abnormal Energy Data in Building Energy Monitoring System Thu, 16 Oct 2014 07:24:26 +0000 http://www.hindawi.com/journals/jen/2014/231571/ This paper presents a novel abnormal data detecting algorithm based on the first order difference method, which could be used to find out outlier in building energy consumption platform real time. The principle and criterion of methodology are discussed in detail. The results show that outlier in cumulative power consumption could be detected by our method. Liang Zhao Copyright © 2014 Liang Zhao. All rights reserved. Study on Calculation Models of Earth-Air Heat Exchanger Systems Thu, 04 Sep 2014 00:00:00 +0000 http://www.hindawi.com/journals/jen/2014/859286/ Modeling is very useful tool in order to predict the effect of the operating parameters like pipe length, radius, depth of burial and air flow rate on the thermal performance and heating/cooling capacity of earth-air heat exchanger (EAHE) systems. Till date many researchers have carried out a number of studies on calculation models for earth-air heat exchanger systems. The analysis of EAHE systems started with the development of one-dimensional models. The two-dimensional models came into practice during the 1990s and were replaced by three-dimensional models in recent years. Latest models are dynamic and technically more advanced which can provide room for all types of grid geometry to produce detailed thermal analysis of EAHE systems. This paper reviews on calculation models of EAHE systems as of the end of March, 2014. Trilok Singh Bisoniya, Anil Kumar, and Prashant Baredar Copyright © 2014 Trilok Singh Bisoniya et al. All rights reserved. Study of Light Harvesting Properties of Different Classes of Metal-Free Organic Dyes in TiO2 Based Dye-Sensitized Solar Cells Mon, 18 Aug 2014 07:07:11 +0000 http://www.hindawi.com/journals/jen/2014/517574/ In dye-sensitized solar cells, the photosensitization of TiO2 thin film semiconductor was accomplished by using different classes of metal-free (fluorone, triarymethane, azo and thiazine based) organic dyes as photosensitizer. The broad electronic absorption spectra of these dyes have been obtained in the visible region due to the presence of chromophoric groups in these dyes. The contribution of these dyes as light harvesting species is seen from the photocurrent action spectrum of the cell. Here, we report the sensitization activity of these dyes in terms of current-potential curve, open-circuit potential, fill factor, IPCE, and overall solar energy conversion efficiency which have been evaluated under 100 mW/cm2 light intensity. The results suggest that dyes based on fluorone and azo groups are promising candidates for high performance, dye-sensitized solar cells because of better anchoring groups (–COOH, –OH, and –) present in these dyes. Better anchorage of dyes to the surface of TiO2 semiconductor helps in charge transfer phenomenon. Ratna Chauhan, Reena Kushwaha, and Lal Bahadur Copyright © 2014 Ratna Chauhan et al. All rights reserved. Analysis of Si/SiGe Heterostructure Solar Cell Wed, 23 Jul 2014 06:38:39 +0000 http://www.hindawi.com/journals/jen/2014/946406/ Sunlight is the largest source of carbon-neutral energy. Large amount of energy, about 4.3 × 1020 J/hr (Lewis, 2005), is radiated because of nuclear fusion reaction by sun, but it is unfortunate that it is not exploited to its maximum level. Various photovoltaic researches are ongoing to find low cost, and highly efficient solar cell to fulfil looming energy crisis around the globe. Thin film solar cell along with enhanced absorption property will be the best, so combination of SiGe alloy is considered. The paper presented here consists of a numerical model of heterostructure solar cell. The research has investigated characteristics such as short circuit current density (), generation rate (), absorption coefficient (α), and open circuit voltage () with optimal Ge concentration. The addition of Ge content to Si layer will affect the property of material and can be calculated with the use of Vegard’s law. Due to this, short circuit current density increases. Ashish Kumar Singh, Jahnvi Tiwari, Ashish Yadav, and Rakesh Kumar Jha Copyright © 2014 Ashish Kumar Singh et al. All rights reserved. Hydropower Production Profiles: Impacts on Capacity Structure, Emissions, and Windfall Profits Mon, 14 Apr 2014 12:30:15 +0000 http://www.hindawi.com/journals/jen/2014/710414/ Production structure in markets with a significant role of hydropower is sensitive to the production profile of hydropower. In this paper we utilize a long-run oriented real-time price based simulation model to analyze through scenarios the impact of different hydropower production profiles on the total annual energy consumed, prices, and capacity structure. We also show the relation between different hydropower production profiles and emissions, costs, and windfall profits. There seems to be no superior scenario under which all socially desirable goals are achieved as there is a clear tradeoff between allowing high windfall profits with highest cost efficiency and achieving the target for lower emissions. Maria Kopsakangas-Savolainen and Rauli Svento Copyright © 2014 Maria Kopsakangas-Savolainen and Rauli Svento. All rights reserved. Microwave Assisted Alkali Pretreatment of Rice Straw for Enhancing Enzymatic Digestibility Tue, 25 Mar 2014 12:09:41 +0000 http://www.hindawi.com/journals/jen/2014/483813/ Rapid industrialization, increasing energy demand, and climate change are the conditions that forced the researchers to develop a clean, efficient, renewable, and sustainable source of energy which has a potential to replace fossil fuels. Ethanol is one of the attractive and suitable renewable energy resources. In present study, effectiveness of microwave pretreatment in combination with sodium hydroxide (NaOH) for increasing enzymatic hydrolysis of rice straw has been investigated and under optimum conditions obtained a maximum reducing sugar (1334.79 µg/mL) through microwave assisted NaOH pretreatment. Chemical composition analysis and scanning electron microscope (SEM) images showed that the removal of lignin, hemicellulose, and silicon content is more in microwave assisted NaOH pretreatment than the blank sample. X-ray diffraction (XRD) analysis revealed that the crystallinity index of rice straw treated with microwave assisted alkali (54.55%) is significantly high as compared to the blank (49.07%). Hence, the present study proves that microwave assisted alkali pretreatment can effectively enhance enzymatic digestibility of rice straw and it is feasible to convert rice straw for bioethanol production. Renu Singh, Sapna Tiwari, Monika Srivastava, and Ashish Shukla Copyright © 2014 Renu Singh et al. All rights reserved. Computer Simulation of the Mass and Energy Balance during Gasification of Sugarcane Bagasse Sun, 16 Mar 2014 11:53:17 +0000 http://www.hindawi.com/journals/jen/2014/713054/ This paper investigated the mass and energy balance of the gasification of sugarcane bagasse using computer simulation. The key parameters and gasifier operating conditions were investigated in order to establish their impact on gas volume and conversion efficiency of the gasification process. The heating value of sugarcane bagasse was measured and found to be 17.8 MJ/kg which was used during calculation of the conversion efficiency of the gasification process. Fuel properties and gasifier design parameters were found to have an impact on conversion efficiency of the gasification process of sugarcane bagasse. The moisture content of sugarcane bagasse was varied by 1.14%, 15%, and 25%, respectively. Optimum conversion efficiency was achieved at low moisture content (1.14%) after computer simulation of the gasification process. The volume of carbon monoxide increased at low moisture content. It was also found that maximum conversion efficiency was achieved at reduced particle diameter (6 cm) and at reduced throat diameter (10 cm) and throat angle (25°), respectively, after these parameters were varied. Temperature of input air was also found to have an impact on the conversion efficiency of the gasification process as conversion efficiency increased slightly with increasing temperature of input air. Anthony Anukam, Sampson Mamphweli, Edson Meyer, and Omobola Okoh Copyright © 2014 Anthony Anukam et al. All rights reserved. Effect of Glass Thickness on Performance of Flat Plate Solar Collectors for Fruits Drying Wed, 12 Mar 2014 06:50:19 +0000 http://www.hindawi.com/journals/jen/2014/247287/ This study aimed at investigating the effect of thickness of glazing material on the performance of flat plate solar collectors. Performance of solar collector is affected by glaze transmittance, absorptance, and reflectance which results into major heat losses in the system. Four solar collector models with different glass thicknesses were designed, constructed, and experimentally tested for their performances. Collectors were both oriented to northsouth direction and tilted to an angle of 10° with the ground toward north direction. The area of each collector model was 0.72 m2 with a depth of 0.15 m. Low iron (extra clear) glass of thicknesses 3 mm, 4 mm, 5 mm, and 6 mm was used as glazing materials. As a control, all collector performances were analysed and compared using a glass of 5 mm thickness and then with glass of different thickness. The results showed that change in glass thickness results into variation in collector efficiency. Collector with 4 mm glass thick gave the best efficiency of 35.4% compared to 27.8% for 6 mm glass thick. However, the use of glass of 4 mm thick needs precautions in handling and during placement to the collector to avoid extra costs due to breakage. Ramadhani Bakari, Rwaichi J. A. Minja, and Karoli N. Njau Copyright © 2014 Ramadhani Bakari et al. All rights reserved. Minimizing Energy Cost in Electric Arc Furnace Steel Making by Optimal Control Designs Thu, 20 Feb 2014 16:28:11 +0000 http://www.hindawi.com/journals/jen/2014/620695/ Production cost in steel industry is a challenge issue and energy optimization is an important part. This paper proposes an optimal control design aiming at minimizing the production cost of the electric arc furnace steel making. In particular, it is shown that with the structure of an electric arc furnace, the production cost which is a linear programming problem can be solved by the tools of linear quadratic regulation control design that not only provides an optimal solution but also is in a feedback form. Modeling and control designs are validated by the actual production data sets. Er-wei Bai Copyright © 2014 Er-wei Bai. All rights reserved. Determining Infiltration Rates and Predicting Building Occupancy Using CO2 Concentration Curves Thu, 06 Feb 2014 13:34:28 +0000 http://www.hindawi.com/journals/jen/2014/670236/ Demand controlled ventilation (DCV) reduces energy loss by reducing the air exchange flow rate to the minimum required to maintain acceptable indoor air quality (IAQ). DCV commonly uses carbon dioxide (CO2) as a proxy for human activity and increases the ventilation rate once a preset CO2 threshold is exceeded. Significant improvements over threshold based ODV strategies are possible if the natural infiltration rate of the building is measured and the occupancy schedule determined by analysing the CO2 concentration continuously. These calculated parameters allow mathematical modeling of the ventilated space and the determination of future CO2 concentrations and allow prediction of future ventilation demands. The natural infiltration rate and the onset and duration of vacancy periods in a residential dwelling were determined by analysing CO2 concentration data. Concentration declines which fit an exponential decay curve with a correlation coefficient >0.90 identified all vacancy periods. The measured natural infiltration rate was found statistically correlated with average wind speed. A dynamic predicted occupancy map was constructed that has the potential to facilitate significant energy savings via deferred ventilation and intelligent cooling and heating strategies. P. Parsons Copyright © 2014 P. Parsons. All rights reserved. Numerical Prediction of Heat Transfer Characteristics of Nanofluids in a Minichannel Flow Tue, 04 Feb 2014 08:29:57 +0000 http://www.hindawi.com/journals/jen/2014/307520/ CFD simulation of the heat transfer and pressure drop characteristics of different nanofluids in a minichannel flow has been explained using FLUENT version 6.3.26. Different nanofluids with nanoparticles of Al2O3, CuO, SiO2, and TiO2 have been used in the simulation process. A comparison of the experimental and computational results has been made for the heat transfer and pressure drop characteristics for the case of Al2O3-water nanofluid for the laminar flow. Also, computations have been made by considering Brownian motion as well as without considering Brownian motion of the nanoparticles. After verification of the computational model with the experimental results for Al2O3-water nanofluid, the simulations were performed for the same experimental readings for different nanofluids in the laminar flow regime to find out the heat transfer and pressure drop characteristics. Arjumand Adil, Sonam Gupta, and Pradyumna Ghosh Copyright © 2014 Arjumand Adil et al. All rights reserved. Chemical Looping Combustion of Methane: A Technology Development View Thu, 28 Nov 2013 17:55:13 +0000 http://www.hindawi.com/journals/jen/2013/949408/ Methane is a reliable and an abundantly available energy source occurring in nature as natural gas, biogas, landfill gas, and so forth. Clean energy generation using methane can be accomplished by using chemical looping combustion. This theoretical study for chemical looping combustion of methane was done to consider some key technology development points to help the process engineer choose the right oxygen carrier and process conditions. Combined maximum product (H2O + CO2) generation, weight of the oxygen carrier, net enthalpy of CLC process, byproduct formation, CO2 emission from the air reactor, and net energy obtainable per unit weight (gram) of oxygen carrier in chemical looping combustion can be important parameters for CLC operation. Carbon formed in the fuel reactor was oxidised in the air reactor and that increased the net energy obtainable from the CLC process but resulted in CO2 emission from the air reactor. Use of CaSO4 as oxygen carrier generated maximum energy (−5.3657 kJ, 800°C) per gram of oxygen carrier used in the CLC process and was found to be the best oxygen carrier for methane CLC. Such a model study can be useful to identify the potential oxygen carriers for different fuel CLC systems. Rutuja Bhoje, Ganesh R. Kale, Nitin Labhsetwar, and Sonali Borkhade Copyright © 2013 Rutuja Bhoje et al. All rights reserved. Empirical Study of Decomposition of Emission Factors in China Thu, 21 Nov 2013 08:04:46 +0000 http://www.hindawi.com/journals/jen/2013/747516/ China’s CO2 emissions increase has attracted world’s attention. It is of great importance to analyze China’s CO2 emission factors to restrain the CO2 rapid growing. The CO2 emissions of industrial and residential consumption sectors in China during 1980–2010 were calculated in this paper. The expanded decomposition model of CO2 emissions was set up by adopting factor-separating method based on the basic principle of the Kaya identities. The results showed that CO2 emissions of industrial and residential consumption sectors increase year after year, and the scale effect of GDP is the most important factor affecting CO2 emissions of industrial sector. Decreasing the specific gravity of secondary industry and energy intensity is more effective than decreasing the primary industry and tertiary industry. The emissions reduction effect of structure factor is better than the efficiency factor. For residential consumption sector, CO2 emissions increase rapidly year after year, and the economy factor (the increase of wealthy degree or income) is the most important factor. In order to slow down the growth of CO2 emissions, it is an important way to change the economic growth mode, and the structure factor will become a crucial factor. Yadong Ning, Yonghong Zhang, Tao Ding, and Yutaka Tonooka Copyright © 2013 Yadong Ning et al. All rights reserved. Review of the Wall Temperature Prediction Capability of Available Correlations for Heat Transfer at Supercritical Conditions of Water Wed, 13 Nov 2013 15:06:41 +0000 http://www.hindawi.com/journals/jen/2013/159098/ The validity of the wall temperature predictions by 18 correlations available in the literature for supercritical heat-transfer regimes of water was verified for 12 experimental datasets consisting of 355 data points available in the literature. The correlations were ranked based on criteria like % data with <5% error, % data with <10°C error and minimum error band in temperature prediction. Details of the best fitting correlations were tabulated. The analysis indicated that for normal heat-transfer conditions, most of the correlations give close predictions. However, at deteriorated heat transfer regimes, only very few prediction points are closer to experimental value. Also, in the ranking process, the first position keeps varying, and no one correlation shall be said as the best for all experiments. Evaluation of the applicability of heat flux to mass-flux-ratio-based prediction of heat-transfer deterioration indicated 75% agreement. The empirical formulae linking mass flux for the prediction of the starting heat flux for heat-transfer deterioration indicated 58.33% of agreement. This review indicated that continued precise experimentation covering wide range of parameter conditions near pseudocritical regime and development of correlations is felt necessary for the accurate prediction of supercritical fluid heat transfer. Dhanuskodi Ramasamy, Arunagiri Appusamy, and Anantharaman Narayanan Copyright © 2013 Dhanuskodi Ramasamy et al. All rights reserved. Natural Pigments from Plants Used as Sensitizers for TiO2 Based Dye-Sensitized Solar Cells Mon, 04 Nov 2013 18:36:42 +0000 http://www.hindawi.com/journals/jen/2013/654953/ Four natural pigments, extracted from the leaves of teak (Tectona grandis), tamarind (Tamarindus indica), eucalyptus (Eucalyptus globulus), and the flower of crimson bottle brush (Callistemon citrinus), were used as sensitizers for TiO2 based dye-sensitized solar cells (DSSCs). The dyes have shown absorption in broad range of the visible region (400–700 nm) of the solar spectrum and appreciable adsorption onto the semiconductor (TiO2) surface. The DSSCs made using the extracted dyes have shown that the open circuit voltages () varied from 0.430 to 0.610 V and the short circuit photocurrent densities () ranged from 0.11 to 0.29 mA cm−2. The incident photon-to-current conversion efficiencies (IPCE) varied from 12–37%. Among the four dyes studied, the extract obtained from teak has shown the best photosensitization effects in terms of the cell output. Reena Kushwaha, Pankaj Srivastava, and Lal Bahadur Copyright © 2013 Reena Kushwaha et al. All rights reserved.