ISSN: 1998-4316



Year 2011

All papers of the journal were peer reviewed by two independent reviewers. Acceptance was granted when both reviewers' recommendations were positive.

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    Paper Title, Authors, Abstract (Issue 1, Volume 5, 2011)


Bioenergy for District Heating and Cooling Systems
Ioana Ionel, Francisc Popescu, Luisa Izabel Dungan

Abstract: The present paper refers to District Heating (DH) and District Cooling (DC) technology, approached from a different angle, when bio energy is encouraged to replace energy that originates form fossil resources. The article reflects on the standard features of the district heating and district cooling and on the way the system is going n terms of evolution throughout their subsequent development stages. It is highlighted why this novel approach in offering heat and cold to the inhabitants represents a key infrastructure as a European efficient resource energy system for today and for the future, under the circumstances of controlling the CO2 emission. The paper concludes with conclusions regarding the district heating and district cooling flexible infrastructure that can support a wide rage of renewable energy sources on large scale.


Analysis of the Disturbances in Distribution Networks using Matlab and ATP
S. Boutora, H. Bentarzi, A. Ouadi

Abstract: The capacitance bank is generally used for compensation in a distributed power grid, if the latter is connected to the utility. An islanded power grid is a distribution grid disconnected from the utility. It can undergo a disturbance namely the ferroresonance phenomenon if the capacitance bank has a non adequate value. In this paper, a study of an islanded power grid is attempted to show the effect of the reconfiguration of the capacitance bank on the ferroresonance. A simulation of the circuit is conducted using Simulink/ MATLAB. In another part of this work, an example of overvoltage study in a distribution medium network using ATP is also presented.


    Paper Title, Authors, Abstract (Issue 2, Volume 5, 2011)


Probabilistic Wind Power Generation Model: Derivation and Applications
Henry Cheng, Yunhe Hou, Felix Wu

Abstract: Wind power output is always uncertain but, in a sufficiently long time interval, the output exhibits statistical behavior that is meaningful enough to be characterized by probability distribution. The aim of this paper is to develop a model for probabilistic wind power generation. In particular, we successfully derive the analytical expression and statistics up to the fourth order of the wind power density function. The work also extends the modeling of wind power output up to a regional scale by Gram-Charlier series. Model results are checked by empirical power data and Monte Carlo simulation. This paper discusses some applications of the wind power statistics such as probabilistic production costing and reliability evaluation in power system literature.


H-Infinity Fuzzy Controller Design for HIV/AIDS Infection System with Dual Drug Dosages via an LMI Approach
Wudhichai Assawinchaichote, Sasiluk Junhom

Abstract: This paper presents a design of H-Infinity fuzzy controller for HIV/AIDS infection system with dual drug dosages. The Tagaki-Sugeno (TS) fuzzy model is applied for fuzzy modeling of the HIV infection dynamic system. A sufficient condition of the controller for this system is given in term of Linear Matrix Inequalities (LMIs). The effectiveness of the proposed controller design methodology is finally demonstrated through simulation results. It has been shown that the anti-HIV vaccines are critically important in reducing the infected cells.


Applications of Solar Energy for Domestic Hot–water and Buildings Heating/cooling
Ioan Sarbu, Marius Adam

Abstract: Increasing awareness of global warming forces policy makers and industries to face two challenges: reducing greenhouse gas emissions and securing stable energy supply against ever– increasing world energy consumption, which is projected to increase by 71% from 2003 to 2030. In addressing these two issues simultaneously, renewable energies prove themselve attractive, as they are independent from the fossil fuel supply and do not contribute to greenhouse gas emissions. Along with the global warming impacts and climate changes, the demands for air conditioning and refrigeration have increased. Therefore, providing heating and cooling by utilizing renewable energy such as solar energy is a key solution to the energy and environmental issues. Romania has an important solar energy potential because of its geographic position and of its favourable climatic conditions. This paper makes references to the solar generation of thermal energy and its use for buildings and domestic water heating, describing both different types of solar equipment and system, and developing a mathematical model for energetical analysis of the solar heating systems. Also, this paper provides a review of the available cooling technologies assisted by solar energy and their recent advances. Solar systems used within building services represent an economic nonpoluting source of energy with high energy performances, leading to considerable reduction in fuel consumption.


Thermal Rehabilitation of Buildings
Ioan Sarbu, Calin Sebarchievici

Abstract: One of main research direction on the construction field is the reduction of the energy consumption, which supposes materials, technology and conception of buildings with lower specific energy need on one hand and equipment with high performances on the other hand. Proper thermal rehabilitation of a building will lead to a significant reduction of heating energy demand offering a higher degree of comfort, and better condition for hygiene. At the same time the environment is less poluted. The energy saving depends on the initial building characteristics and the thermal rehabilitation level on one hand, and on the proper adjustment and control of the heating system on the other hand. In this paper is analyzed the main effects of building thermal rehabilitation, with implications upon heating energy consumption and upon comfort of the occupants.Thus, it is developed a computational model of optimum additional insulation thickness, taking into account the investment cost to improve thermal resistance of building envelope and operational costs as heating energy consumption.


    Paper Title, Authors, Abstract (Issue 3, Volume 5, 2011)


Security Assessment of the Results of the Day-Ahead Electricity Market, Using a Monte Carlo Power System Simulator
Davide Poli, Paolo Pelacchi

Abstract: Many variables are involved in the power system’s reliability assessment, often affected by random events, such as load levels, wind speed and accidental failures of generating units or transmission lines. Furthermore, the presence of a competitive market, which schedules the hourly working point of the electric system, has to be considered and an effective calculation of the reliability level associated to the dispatching schedule defined by the market must be operated by the System Operator (SO) before the actual energy delivery. For this kind of problems, a probabilistic approach, based on sequential Monte Carlo techniques, can be more powerful than analytical methods. In the present paper, a simulation tool for calibrating the amount of generation reserve for the following day is described and analyzed, also discussing the results of a case study based on the IEEE RTS-96 test grid.


Advanced Features of a Small-Scale Biomass Boiler Control for Emission Reduction
Jan Hrdlicka, Bohumil Sulc

Abstract: Small scale biomass combustion is a specific field of control issues where one of the most important features is cost effectiveness. It means that any kind of control system improvement should be done with the lowest possible additional costs. Generally, the basic control of such kind of boiler regulates temperature of outlet heating water. This control can be also performed by a PLC. In such a case, there is possibility to enhance this control by additional algorithms that are responsible for extended optimization functions. Main focus of such optimization should be mainly economic viewpoint of the boiler’s operation regarding particularly decrease of fuel consumption and therefore cost saving. Other strong interest is reduction of several unwanted gaseous emissions, mainly carbon monoxide and unburned hydrocarbons. In the interest can be also nitrogen oxides emissions that are much more complicated to control in such a small boiler. This previously minor problem has become significant with the large expansion of the small-size biomass-fired boilers. The combustion process consists of phenomena that we have little information about for an exact mathematical description. The equations of the chemical reactions are known, but in reality the combustion of biomass is much more complicated and more variable than a mathematical model can express. Therefore, techniques searching extreme are more suitable than controllers requiring a mathematical model in design or tuning. In such a way it is possible to design a controller that is able to control the combustion process effectively over the whole operation range.


Clearing Procedures for Day-Ahead Italian Electricity Market: Are Complex Bids Really Required?
Davide Poli, Mirko Marracci

Abstract: Many technical debates discussed in the last years the market structure that can be considered as optimal for electricity in a deregulated environment. Simplicity and market transparency do not always comply with the intrinsic complexity of the electrical system, due to technical constraints and security requirements. The mechanism for bid selection in the day-ahead market is one of the most discussed topics, because it strongly influences both the economical revenues of operators and the physical feasibility of the dispatching schedules set by the market. Usual production bids, only detailing hourly prices and quantities (“simple bids”), do not transfer to the clearing mechanism important technical-economical integral constraints, like the minimum daily revenue required by the operator or the power ramp limitation of generating units; in this case, adjustment sessions follow the primary energy market, to correct undesired or unfeasible outcomes. In some markets, such additional constraints are already expressed in the so-called “complex bids”, thus avoiding or minimizing the need for adjustment sessions. Nevertheless, the clearing mechanism of the day-ahead market results strongly complicated and the system transparency decreases; the effectiveness of this solution must be then carefully assessed. In this paper, we present an analysis of the possible quantitative impact of complex bids in the Italian electricity day-ahead market, in order to evaluate possible benefits and drawbacks.


    Paper Title, Authors, Abstract (Issue 4, Volume 5, 2011)


Thermal Analysis of a High Power LED Multi-Chip Package Module
Bor-Jang Tsai, Sheam-Chyun Lin, Wei-Kuo Han

Abstract: Some difficulties occur by using multiple high-power LEDs in products to predict the temperature distribution because of the interaction of heat generated by each single-chip LED in the same module. To determine the heat dissipation of a multi-chip LED module, solid physical models for both single-chip and multi-chip LEDs with cooling fins were constructed. Simulation of the temperature distribution under natural convection was conducted using numerical analysis and by introducing formulas to estimate change in heat resistance. In addition to elucidating the heat dissipation of multi-chip LED modules, this study attempts to identify the major factors affecting the temperature distributions of LEDs. Simulation results from the finite element program indicate that expressing the temperature distribution of a single LED chip using a spherical coordinate system is appropriate. The temperature curve of a copper plate away from the chip is nonlinear since the distribution curve declines dramatically and is no longer linear. The temperature of a multi-chip LED module is slightly less than that of linear superposition. A comparison of the estimated value for a multi-chip LED with the simulation result confirms the practicability and accuracy of the proposed thermal resistance formula in this work. This study provides reference data for estimating of thermal resistance in a multi-chip module.


The Future of Europe's Energy Policy: The Legislative Framework and the Soft Law Instruments
V. Pozeb, D. Goricanec, T. Krope

Abstract: Energy is essential for Europe to function. The goal of the EU policy is to ensure the security of supply; additionally, Europe deals with the challenges of climate change and the need to establish a coherent external energy policy. The aim of the energy policy is to complete the internal energy market, to ensure supply security and solidarity between EU countries, to achieve a more sustainable, efficient and diverse energy mix, to tackle climate change, to enhance research and innovation at the service of Europe's energy policy, and to aim towards a coherent external energy policy.


Clean Energy from Gasification of Biomass for Sterilization of Mushroom Growing Substrates
Nakorn Tippayawong, Chutchawan Chaichana, Anucha Promwungkwa, Presert Rerkkriangkrai

Abstract: Sterilization of mushroom growing substrates is energy intensive process for mushroom cultivation. Fuelwood may be replaced by spent substrates for hot steam generation. However, combustion of spent substrates directly in an open furnace is troublesome due to low efficiency and excessive smoke emission. Alternative conversion of the by-product to provide clean energy should be studied. In this work, recycling of spent mushroom substrates through gasification to provide heat for sterilization of substrate bags has been investigated. The findings showed that spent substrate was successfully used as biorenewable fuel in a gasifier. Satisfactory operation was obtained. Gasification of spent substrate could provide required thermal input, with clean energy to the local mushroom farm. Thermal efficiency of about 20% was achieved, compared to 5% from existing furnace. Preliminary economic analysis showed that the farm can save around $300 a month, with simple payback period to positive cash flow of less than 12 months.


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