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U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x Contents Sary Awad, I-A. Basa, M. Paraschiv, S. Kumar, M. Tazerout Characterisation and optimisation of biodiesel’s production from waste cooking oil 3 Andrei Damian, Andrei-Mugur Georgescu Modelling of the wind effect on a double-tracking PV platform 13 Cosmin Mărculescu, Adrian Badea, Tiberiu Apostol Two-stage gasification process of solid organic compounds 21 Cora Bulmău (Gheorghe), Cosmin Mărculescu, Adrian Badea, Tiberiu Apostol Pyrolysis parameters influencing the bio-char generation from wooden biomass 29 Michel Feidt Energy efficiency and environment 39 Petre Blaga, Horia Necula, Constantin Ionescu The increase of energy efficiency through the conversion of a thermal power plant into a cogeneration plant 53 André Lallemand, Lingai Luo, Renaud Gicquel Comparative study of heat production by cogeneration or heat pump 65 Roxana Patraşcu, George Darie, Eduard Minciuc, Cristian Răducanu, Adina Stanculea Comparative analysis of production and processing of glassware and technical glass 73 Gheorghe Cârţină, Gheorghe Grigoraş, Elena-Crenguţa Bobric Opportunities to conserve energy right from distribution installations 81 Florin Ionescu, Constantin Bulac, Ioana Pisică, Ion Tristiu, Lucian Toma An evolutionary programming application to optimal reactive power dispatch 91 Alberto Borghetti, Mauro Bosetti, Carlo Alberto Nucci, Mario Paolone Parameters identification of a power plant model for the simulation of islanding transients 101 Cristian Dincă, Adrian Badea, Tiberiu Apostol Life cycle impact assessment of fossil fuels 115 Ion Melinte, Mihaela Bălănescu, George Darie, Carmencita Constantin New methods for the assessment and the reduction of the co2 emissions in iron and steel processes and thermo-electric power stations, based on an integrated approach 127 U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x Elena David, I. Ştefanescu, A. Armeanu Economical CO2 capture from fossil flue utilization 135 Iosif Prodea, Cristina Alice Mărgeanu, Andrei Rizoiu, Ilie Prisecaru, Nicolae Dănilă Void reactivity reduction in CANDU reactors using burnable absorbers and advanced fuel designs 145 Ilie Prisecaru, Iulian Pavel Niţă, Daniel Dupleac Influence of preheater loss in regeneration efficiency on the secondary circuit 153 Viorel Şerban, Ilie Prisecaru Analysis of some critical points that may influence Cernavoda NPP nuclear safety during an earthquake and solutions to increase the safety margin 163 Florin Munteanu, Ciprian Nemeş Real efficiency of intelligent switching of high voltage circuit-breakers 173 Marian Costea, Bogdan Nicoară Influence factors on the transmitted overvoltages from high voltage to low voltage networks 183 Cristian Lăzăroiu, Dario Zaninelli DC arc furnace modelling for power quality analysis 191 Florin Ciauşiu, Mircea Eremia Steady-state stability limit identification for large power systems 201 Ioana Pisică, Petru Postolache Rough set theory and its applications in electrical power engineering. A survey 211 U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x CHARACTERISATION AND OPTIMISATION OF BIODIESEL’S PRODUCTION FROM WASTE COOKING OIL Sary AWAD, I-A. BASA, M. PARASCHIV, S. KUMAR, M. TAZEROUT We studied the transesterification of two types of waste cooking oil (WCO), with methanol and ethanol using NaOH. Also the physical characteristics of produced biodiesel were studied and compared to the European standard EN 14214. The WCO used in this study was collected from the École des Mines de Nantes university’s restaurant. We used to search the optimum conversion ratio, combining four variables: temperature of reaction, catalyst amount, time of reaction and alcohol to oil molar ratio, the effect of free fatty acid content in the oil and the type of alcohol used in the reaction were also studied. Keywords: biodiesel, waste cooking oil, transesterification, biodiesel characterization MODELLING OF THE WIND EFFECT ON A DOUBLETRACKING PV PLATFORM Andrei DAMIAN, Andrei-Mugur GEORGESCU The objective of the paper is the assessment of the wind load applied to a real photovoltaic (PV) platform installed on a site situated in Brasov, Romania. The platform has a double-tracking axis mechanism, which allows the rotation of the platform depending on the sun position, in order to gather the maximum solar yield to produce electricity. The 3D numerical investigations were performed by using the COMSOL Multiphysics software. The results were represented graphically, in terms of pressure fields along the PV platform disk, depending on the seasonal and daily angle of inclination relatively to the two rotation axes of the platform. Keywords: photovoltaic platform, PV, wind load, COMSOL Multiphysics U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x TWO-STAGE GASIFICATION PROCESS OF SOLID ORGANIC COMPOUNDS Cosmin MĂRCULESCU, Adrian BADEA, Tiberiu APOSTOL The research focused on two-stage high temperature gasification under steam atmosphere, at atmospheric pressure conducted organic solid compounds for maximum energy potential recovery with respect to product transformation during the process and its influence on final results. The work aimed to establish the dependence of second gasification stage on the first devolatilization one together with the connection: process parameters – reactions kinetics. The approach was justified by the products different physical-chemical structures and carbonization parameters: pressure, temperature and residence time influence on the char formation and its physical characteristics. Furthermore the second reason for this approach was the advantages of two-stage pyro-gasification process, compared to direct gasification one. Keywords: pyrolysis, gasification, kinetics, solid fuel PYROLYSIS PARAMETERS INFLUENCING THE BIO-CHAR GENERATION FROM WOODEN BIOMASS Cora Bulmău (GHEORGHE), Cosmin MĂRCULESCU, Adrian BADEA, Tiberiu APOSTOL Recently much research has been investigated on identifying suitable biomass species, which can provide high-energy outputs, to replace conventional fossil fuels. This paper reports an approach for increasing the yield of bio-char production from pyrolysis with respect to process conditions. The analyzed material was cherry sawdust. The experiments were conducted for pyrolysis temperature between 450ºC and 800ºC. The experimental study focused on the influence of pyrolysis temperature, residence time or heating rate on the bio-char yield and on determination of the HHV of the pyrolysis char. Keywords: biomass, bio-char, pyrolysis, temperature, heating rate U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x ENERGY EFFICIENCY AND ENVIRONMENT Michel FEIDT In this paper, we intent to review and reconsider the concept of efficiency applied to energy systems and processes. It is shown that due to increasing use of energy, we must refine the criterions that serve as objective functions to characterize and optimize systems and processes. Moreover coupling between energy uses and environment appears more and more important. This question starts to be explored : present state of the art is summarized ; some suggestions and perspectives are evoked, particularly the relation to economy, even if the main aspects developed remain centered on the scientific part and technical consequences. Keywords: energy, environment, economy, efficiency THE INCREASE OF ENERGY EFFICIENCY THROUGH THE CONVERSION OF A THERMAL POWER PLANT INTO A COGENERATION PLANT Petre BLAGA, Horia NECULA, Constantin IONESCU Re-engineering obsolete industrial plants is an increasingly important issue for small and medium enterprises. This paper describes the transformation of a thermal power plant with simultaneous production of low-temperature saturated steam and hot water into a central cogeneration plant, at a company from the drug industry field. Taking into account the economic advantage, reduced operating problems, environmental protection etc., the cogeneration solution with heat engines was appealed. By using this solution for cogeneration, the company recorded a 5-12% reduction in the monthly bills, lower than buying all electricity from the system. Keywords: energy efficiency, cogeneration, heat engine, technical analysis U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x COMPARATIVE STUDY OF HEAT PRODUCTION BY COGENERATION OR HEAT PUMP André LALLEMAND, Lingai LUO, Renaud GICQUEL Considering Carnot cycles, it is shown that reducing the power of a thermal power plant to produce cogeneration or using this difference in power to run heat pumps is equivalent in terms of overall performance. Practically, this is however not the same. This conclusion is put in evidence when considering an actual 280 MW power cycle and R134a, R600 and R717 heat pumps. It is shown that depending on the operating temperatures of the heat pumps and the heating network transmission losses, the overall cogeneration performance can be higher than the use of heat pumps in many configurations. Keywords: rational use of energy, waste heat, power plants, heat pumps, cogeneration COMPARATIVE ANALYSIS OF PRODUCTION AND PROCESSING OF GLASSWARE AND TECHNICAL GLASS Roxana PATRAŞCU, George DARIE, Eduard MINCIUC, Cristian RĂDUCANU, Adina STANCULEA The article is an integrated approach of energetic efficiency and environmental impact in the field of glass industry. The article is also targeting at improving of energetic and economic efficiency, a reduction of the environment impact and new equipment implementation in the field of glass manufacturing industry in Romania. The model aims at increasing energy and economic efficiencies and decreasing environmental impact, as well as finding new clean technologies for the Romanian glass manufacturing industry. New methodologies techniques and technologies and also the new developed evaluation models might have a replication potential for other industrial sectors. Keywords: glass, analysis, energy, economic, environment U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x OPPORTUNITIES TO CONSERVE ENERGY RIGHT FROM DISTRIBUTION INSTALLATIONS Gheorghe CÂRŢINĂ, Gheorghe GRIGORAŞ, Elena-Crenguţa BOBRIC The paper presents a methodology of the evaluation of the energy saving potential in distribution network, by replacement of the old transformers with efficient transformers. The modeling of the transformers load was performed by fuzzy techniques. Finally, a study case for a urban distribution network is presented. Keywords: smart grids, energy saving, efficient transformers, fuzzy techniques AN EVOLUTIONARY PROGRAMMING APPLICATION TO OPTIMAL REACTIVE POWER DISPATCH Florin IONESCU, Constantin BULAC, Ioana PISICĂ, Ion TRISTIU, Lucian TOMA This paper presents an application of evolutionary programming (EP) to optimal reactive power dispatch (ORDP). The objective of ORDP is to minimize the real power losses and keep the voltages and reactive power generations in their operating limits. In this matter the control variables are generator bus voltages and transformer taps. The proposed EP approach was evaluated on the modified IEEE-30 bus system. Keywords: Evolutionary Programming, Optimal Reactive Power Dispatch, Minimizing the Real Power Losses U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x PARAMETERS IDENTIFICATION OF A POWER PLANT MODEL FOR THE SIMULATION OF ISLANDING TRANSIENTS Alberto BORGHETTI, Mauro BOSETTI, Carlo ALBERTO NUCCI, Mario PAOLONE The paper presents a procedure for parameter identification along with its application to the model of a combined cycle power plant that includes the surrounding electrical network, built for the analysis of islanding maneuvers transients. The paper illustrates both the power system computer model, implemented within the EMTP-RV simulation environment, and the developed identification procedure based on the interface between the developed model and Matlab. The parameter identification procedure is applied to experimental transient recordings that make reference to a similar power plant. Keywords: power plant, parameter identification, islanding, electromechanical transients LIFE CYCLE IMPACT ASSESSMENT OF FOSSIL FUELS Cristian DINCĂ, Adrian BADEA, Tiberiu APOSTOL The main objective of this study is to compare the life cycle of fossil fuel (coal, natural gas and oil) in order to assess the overall environmental impact. In this respect it was analyzed the fossil fuels energy production based on the best available energy technologies for each fuel. The methodology used in order to evaluate the total environmental impact was Life Cycle Analysis. The method allowed on one side the identification of the pollutants generated in each stage: extraction, treatment, transportation and combustion, and on the other side identification of the main classes of impact according the pollutants inventory. Keywords: LCA, fossil fuels, multi-criteria analysis U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x NEW METHODS FOR THE ASSESSMENT AND THE REDUCTION OF THE CO2 EMISSIONS IN IRON AND STEEL PROCESSES AND THERMO-ELECTRIC POWER STATIONS, BASED ON AN INTEGRATED APPROACH Ion MELINTE, Mihaela BĂLĂNESCU, George DARIE, Carmencita CONSTANTIN This paper presents new methods for the assessment and the reduction of the CO2 emissions in iron and steel processes and in thermo-electric power stations, based on a conceptual model for an integrated, technological and energetic system, using the calculus programs and patterns and simulations of the process input parameters (quantities of raw materials, fuel feeds, carbon content in the raw materials and in the fuels). There are approached primary methods for reducing the CO2 emissions, namely the modification of the process input parameters or the modification of the actual process (technological or combustion), for improving its technologic or energetic efficiency. Keywords: new methods, CO2 emissions reduction, integrated approach, iron and steel ECONOMICAL CO2 CAPTURE FROM FOSSIL FLUE UTILIZATION Elena DAVID, I. ŞTEFANESCU, A. ARMEANU This paper presented an experimental study for CO2 capture from flue gas by pressure swing adsorption process (PSA). Capture of carbon dioxide from a binary mixture (N2/CO2) simulating flue gas was performed by PSA, using selective adsorbents (zeolite-X, carbon molecular sieve, activated carbons). One PSA process consists of three adsorption beds. The process was tested by varying the operation parameters: pressures of adsorption and vacuum evacuation steps. As a typical result, a high purity CO2 (≈99%) can be produced with recoveries of 50% and 65% from feed gases containing 15-25 vol. % CO2 respectively. By the other process of two stage PSA, CO2 can be concentrated from feed gas to product of 99% with much higher capture (>80%).The obtained results prove that the capture of CO2 from the fossil fuel industry by PSA process is to find cost-effective solutions that will reduce the release of CO2 into the atmosphere and can contribute to cleaning of environment. Keywords: CO2, PSA, Adsorption, Pollution, Environment U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x VOID REACTIVITY REDUCTION IN CANDU REACTORS USING BURNABLE ABSORBERS AND ADVANCED FUEL DESIGNS Iosif PRODEA, Cristina Alice MĂRGEANU, Andrei RIZOIU, Ilie PRISECARU, Nicolae DĂNILĂ It is very well known that the CANDU® reactor has positive Coolant Void Reactivity (CVR), which is an important criticisms about CANDU. Recent innovations based on using of a thin absorbent Hafnium shell in the central bundle element were successfully been applied to the Advanced CANDU Reactor (ACR™) project. The paper's objective is to analyze elementary lattice cell effects in applying of such methods to reduce CVR. Three basic fuel designs in their corresponding geometries were chosen to be compared: the ACR-1000TM, the RU-43 (developed in INR Pitesti) and the standard CANDU fuel. The Graphite absorber influence on void effect was also evaluated. The WIMS calculations proved the Hafnium absorber suitability (in the latest "shell design") to achieve the negative CVR target with a great accuracy for the ACR-1000 fuel bundle design than the other two projects. Keywords: ACR, CANDU, CVR, burnable absorber INFLUENCE OF PREHEATER LOSS IN REGENERATION EFFICIENCY ON THE SECONDARY CIRCUIT Ilie PRISECARU, Iulian Pavel NIŢĂ, Daniel DUPLEAC This paper presents the results of operating analyses in secondary circuit of Cernavoda NPP - Unit 2, in abnormal regimes, due to the failure of a feedwater preheater from the regenerative chain. Based on these analyses, operating solutions are proposed in order to minimize power losses from the normal regime. In this paper we developed a simplified method for calculating the operating parameters of the heat exchangers in abnormal regimes. Also this method allows quick detection of the abnormally operating heat exchanger. Keywords: NPP operation, abnormal regimes, minimized losses, heat exchangers, plant efficiency U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x ANALYSIS OF SOME CRITICAL POINTS THAT MAY INFLUENCE CERNAVODA NPP NUCLEAR SAFETY DURING AN EARTHQUAKE AND SOLUTIONS TO INCREASE THE SAFETY MARGIN Viorel ŞERBAN, Ilie PRISECARU The paper is a general presentation of the main critical points in CERNAVODA NPP- Unit 1 and 2 in respect of seismic behavior, which from the authors’ viewpoint are: - Fuelling Machine coupled to a fuel channel; - The pipe leg of the Emergency Core Cooling System (ECCS) having supports on the inner structure, the containment and the staircase structure in B area; - Live Steam pipe legs installed on the reactor containment and service building. Keywords: critical points, safety margin, SERB device, hysteresis diagram REAL EFFICIENCY OF INTELLIGENT SWITCHING OF HIGH VOLTAGE CIRCUIT-BREAKERS Florin MUNTEANU, Ciprian NEMEŞ The concept of intelligent switching means extending the existing controlled switching characteristics to new situations from which the case of faults is the most important. One of the main aspect is related to modern high speed circuit-breakers which are opening before the d.c. component of the short-circuit current is closed to zero. Based on authors’ main research results in implementation of intelligent switching of high voltage circuit-breakers in case of faults, the paper deals with the real advantages and efficiency of this relative new technology in power systems. Between main positive results of this new technology there is a major power quality improvement as much as the overvoltages and overloads are strongly diminished. Keywords: intelligent switching, stress mitigation, circuit-breakers U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x INFLUENCE FACTORS ON THE TRANSMITTED OVERVOLTAGES FROM HIGH VOLTAGE TO LOW VOLTAGE NETWORKS Marian COSTEA, Bogdan NICOARĂ In the high and medium voltage networks a large variety of overvoltages can occur. These are produced by lightnings, switching operations or insulation faults. Normally, the protection against overvoltages, based of surge arresters and relay protection of the equipment, act to eliminate or reduce the insulation stress. The transients occurred in the high or medium voltage networks are then transmitted by different mechanisms to the low voltage networks. The paper analyse the influence factors and their weights to the transmitted overvoltages from a superior voltage networks to the low voltage one considering a proper action of the protection against overvoltages in the first network. The study was performed on a real configuration of network subjected of different shape and amplitude of lightning overvoltages. Keywords: electric power installation, full lightning impulse, chopped lightning impulse, lightning induced overvoltage DC ARC FURNACE MODELLING FOR POWER QUALITY ANALYSIS Cristian LĂZĂROIU, Dario ZANINELLI The dc arc furnaces are highly disturbing loads for transmission and distribution networks. The present paper deals with the study of the dc arc furnace modeling and analysis of the controller structure for the ac-dc converter, highlighting the advantages obtained regarding power quality improvement. In this study both deterministic and random models of the electric arc are considered together with different structures of the ac-dc converter unit. Keywords: voltage flicker, dc arc furnace, power quality U. P. B. Sci. Bull., Series C, Vol. 72, Iss. 1, 2010 ISSN 1454-234x STEADY-STATE STABILITY LIMIT IDENTIFICATION FOR LARGE POWER SYSTEMS Florin CIAUŞIU, Mircea EREMIA This paper is treating the problem of steady-state stability reserve identification in a power system when realizing off-line simulations. Even in off-line simulations the stability reserve of a power system is not a straight forward analysis. The difficulties appear when trying to solve the stability reserve aspect for a large power system. Present paper is illustrating the steady-state stability limit identification by using eigenvalues and eigenvectors computation. In this respect, a software application created by the authors under Matlab software tool is used in combination with PSA/Eurostag in order to compute the eigenvalues of the steadystate matrix. Keywords: steady-state stability, eigenvalues, steady-state matrix analysis. ROUGH SET THEORY AND ITS APPLICATIONS IN ELECTRICAL POWER ENGINEERING. A SURVEY Ioana PISICĂ, Petru POSTOLACHE Rough Set theory represents a promising technique in imperfect data analysis, which has found interesting extensions and various applications. It can be regarded as complementary to other theories that handle imperfect knowledge, such as Bayesian inference or fuzzy sets. The paper presents some Rough Set Theory concepts and applications in several fields, with emphasis on a series of applications in electrical engineering. Kewords: rough set, attribute selection, information system