Volume 3, No. 11 (2005)
Articles
ELECTRICAL AND THERMAL ENERGY PRODUCTION USING COGENERATION TECHNOLOGIES AT THE WASTE WATER TREATMENT STATIONS
BOLOGA ALEXANDU, BERZOI SIMION
Biogas is one of the most common renewable energy resources. It can be produced by the anaerobic fermentation of wood or agricultural waste, on landfills or in sewage plants. These last two ways of producing biogas are the most interesting for cities in their policies of promoting renewable energies. The use of biogas is also interesting economically as it is in 1999, already one of the cheapest renewable energy sources. It often is burned in combined heat and power plants. J.S.C. Energy Investment Group has constructed first in Moldova Republic and first in post Soviet Union Cogeneration Station which will operate on biogas. Now Station is started on natural gas, but in 3 years will be transferred on biogas.
CHOOSING A SOLUTION TO GENERATE THE SINUSOIDAL SIGNAL FOR A DINAMIC IDENTIFICATION OF PELTON TURBINES
CATANASE ADRIANA, HORA CRISTINA
During the function of Pelton turbines, due to the periodical changes of the temporary position betwen the water spurt and the palette having the form of a cup, the flow is unstatic and has a free surface. So, due to this specific features, a precise theoretical analise of the Pelton turbines becomes more difficult and the validation of the proposed model can be made only with the help of the dinamic identification. In the case of this type of turbine I chosed in purpose to determinate the dinamic specific features to use the periodical signals for tests and more specific the sinusoidal signal. The obtained results must be verified by experiments in purpose to validate the proposed theoretical model.Before this experiment we must take into consideration the praparation phases which means – to choose the machinery needed and to establish its characteristic and a preliminary study of the precess. Within the preliminary study must be established the orientative values of the frequency, its character and the intensity of the sources of perturbation, the aproximate structure of the transfer function, etc. Achieving the preparing phases will allow the passing way to planification and complete the experiment.Taking into consideration the details mentioned above, based on the measurments for a static treatment, I have determined the approximate shape for the transfer function.For a dinamic identification, the entrance value, which means the move of the injector needle of the turbine, must have a sinusoidal variation. This means to create an instalation that allows this variations to be obtained.This paper analises for a given case of a Pelton turbine, several solutions to obtain a sinusoidal variation of the entrance value of the process and also looks to find an optimal solution from thr point of view of the experimental spa used.
AN APPROACH FOR AUTOMATION THE OPERATINGOF THE ROTARY LJUNGSTROM TYPE PRE-HEATER (I)
CIUCESCU EDUARD
One of problems for all rotary Ljungstrom type pre-heaters is to optimize the number of rotation of the heat wheel. Due to the many sources of boiler inefficiency, the temperature of flue gas changes, it is necessary to change the number of rotation of heat wheel. This paper presents a logical scheme of operating the rotary Ljungstrom type pre-heaters, taken into consideration only the exit temperature of flue-gas changing the flow of natural gas.
AN APPROACH FOR AUTOMATION THE OPERATINGOF THE ROTARY LJUNGSTROM TYPE PRE-HEATER (II)
CIUCESCU EDUARD
All rotary Ljungstrom type pre-heaters have the problem is to optimize the number of rotation of the heat wheel. Due to the many sources of boiler inefficiency, the temperature of flue gas changes, it is necessary to change the number of rotation of heat wheel. This paper presents a logical scheme of operating the rotary Ljungstrom type pre-heaters, taken into consideration only the exit temperature of flue-gas changing the flow of natural gas, but also the number of rotation of the heat wheel.
THERMOECONOMIC OPTIMIZATION OF THE ENERGETIC PLANTWITH INTERNAL COMBUSTION ENGINES BY USING LINEARPROGRAMMING METHODS
DUMITRU GHEORGHE, CARAGHIULEA MARIANA
In the paper there are presented a linear mathematical model of the thermoeconomic optimization of the energetic plants with internal combustion engines and solving coresponding linear programming methods.
NONLINEAR MODEL FOR NATURAL CARBON CYCLE PROCESS
ENESCU ALEXANDRU, COSTACHE GABRIEL
It was in 1896 when S. Arrhenius first noticed the potential effect of humanactivities on the carbon cycle and the implications for climate change. He put forward thetheory that CO2 in the atmosphere was an important greenhouse gas and that it was a byproductof burning fossil fuels. In 1958, Charles Keeling began the observations at MaunaLoa Observatory, 3650 m up a mountain in Hawaii, regarded as far enough away from anycarbon dioxide source to be a reliable measuring point. Measurements of CO2 in theatmosphere have been continuous for almost 50 years. In recent decades, CO2 increased onaverage by 1.4 parts per million (ppm) a year because of the amount of fossil fuels burnt.
THERMOPOWER OPTIMISATIONS METHODS IN THE THERMOSUN PLANTS WORKING
ENESCU DIANA, HUSSU ADELA, POPA MIRCEA
This paper presents the operational factors optimisation of the thermosun plant have placed within Electrical Engineering Faculty from ”Valahia” University of Târgoviºte. The thermosun plant is an automatic plant by means of a German equipment (its name is Sun-Go); this equipment is necessary for the thermosun applications. The measurements were performed during one week and were computed by a computer, which is necessary for the data hold, and the data processing have calculated in C++. By means of these diagrams, it was obtained the optimisation of the operational factors. Regarding the continuous increase of the equivalent fuels price, the arguments for rigging of a building with a thermosun plant are evidently:• This equipment permits the simplest and most efficient exploitation of the sun power, the saving of the beneficiary costs begining in the same time with bringing into service of the equipment;• Generally, the sun power utilisation assures protection to the increase of the power price;• The sun power is ecological and is necessary for the preservation of the power conventional resources and to the firm decrease of the emissions of the pollutant substances.
THE INFLUENCE OF A LADDLE FURNACE OVER THE GENERATORS FROM THE GRID AT WHICH IT IS CONNECTED
GAVRIŞ TEODOR, RUJA ION
The paper presents the influence of a laddle furnace over the generators from the grid at which it is connected.
KINEMATIC STIRLING MOTOR-DRIVEN COMPRESSORS
HOMUŢESCU VLAD MARIO
The paper analyzes the possibility of building monoblock kinematic Stirling motor-driven compressors. Such an engine is a combination between a compressor and a kinematic Stirling engine. In the equivalent schematic diagram the power piston of the Stirling engine also performs the function of the compressor piston.The advantages and the disadvantages of these machines are analyzed.
RECOVERED EQUIPMENT COGENERATION:CLEANER AND CHEAPER ENERGY
MILER MIHAI CRISTIAN, ZUBCU VICTOR, ZUBCU DORINA SILVIA, HOMUŢESCU VLAD MARIO
The increase in efficiency and decrease of pollution are the main objectives in electricity and heat generation. The cogeneration perfectly answers to these issues. The cogeneration installations based on recovered components (RCCI) could be an interesting solution for developing countries having low financial resources. Are RCCI feasible? Are they really efficient? Are they really environmental friendly? The answers to these questions are given in this work. The answers are based on three years operating experience of the first Romanian RCCI, based on GTE 2000 generating set and CAF 6 hot water boiler.
MODELLING OF ELECTRICAL FIELD DISTRIBUTION OF CHARGED PARTICLES-FILLED PLANE CAPACITOR IN DEPENDENCE OF ITS CONCENTRATION
SAJIN TUDOR, PUIU-BERIZINŢIU MIHAI, CRĂCIUN ALEXANDRU, BUZDUGĂ ŞTEFANIA ROXANA
Equations are presented for calculation of the field strength distribution across the interelectrode space of a capacitor as a function of the concentration and size of the charged particles. The distribution of particle concentration is conducted in the steady-state flow of a fluid electroaerosol formed on the free surface of a bubbling layer and inoving along the electrical field lines of force. Computation formulas are derived for the mean concentration of particles as a function of their size, the field strength, and the flow of the bubbling gas
CONTROL LAW DESIGN FOR FIRING RATE SYSTEM OF STEAM DRUM BOILER FOR THE PURPOSE OF FUEL SAVING.
SIT MIHAIL, JURAVLEOV ANATOLII, POPONOVA OLGA
The control law of firing rate system of steam drum boiler is examined. Main features of the proposed cascade control system are the presence in the external control loop of the modified PI-control law which includes the functional component of the error signal and the availability at the input of the external control loop of the sum of signal of derivative from the difference between steam flow rate and prescribed value of steam flow rate and the signal of the difference between prescribed value of pressure in header and the current pressure in header.
OPTIMIZATION OF BLOWDOWN CONTROL SYSTEM OFSTEAM DRUM BOILER
SIT MIHAIL, JURAVLEOV ANATOLII, POPONOVA OLGA, SIT BORIS
The evaluation of necessary value of boiler blowdown ensures energy, water andchemicals cost savings. This paper describes a new blowdown control strategy forblowdown system of a steam drum boiler. Control system uses data about the pollution inboiler’s input and output, blowdown and steam flow rates. Mathematic modeling results ofcontrol system show significant improvement of overall performance, comparing withtraditional control systems.
ENERGY SUPPLIES FOR ISOLATED HOUSES USING WIND TURBINES
ŢÂRULESCU RADU, ŢÂRULESCU STELIAN
Wind energy is one of the most economical sources of new electricity available today. Wind turbines can be set up quickly and cheaply compared with building new coal-fired generating stations or hydroelectric facilities. Modern wind generating equipment is efficient, highly reliable, and becoming cheaper to purchase. Because of these factors, wind energy is recognized as the world’s fastest-growing new energy source [1].Small, highly efficient wind turbines are becoming popular as a source of electricity for rural homes. The cost of installing one comes close to that of putting up poles, overhead power lines and other equipment necessary to connect to the electrical grid. The advantage is that the homeowner owns the generating equipment and is freed from paying the electricity. A modern wind turbine produces electricity 70-85% of the time, but it generates different outputs dependent on wind speed. Over the course of a year, it will generate about 30% of the theoretical maximum output. The wind energy can be transformed into other forms of energy: electrical, mechanical and thermal. The mechanical energy can be used for pumping water.
RESEARCH REGARDING THE IMPROVEMENT OF THE PERFORMANCESOF THE POWER GENERATION BY POWDERED COAL COMBUSTION
VASIU IOAN
The work presents some conclusions of the author`s research carried out with the aim of increasing the energetic efficiency of the steam generators with natural circulation, running on coal in powdered state in thermal power plants.The exergetic analysis of the thermodynamic processes, which take place in these thermal installations, made possible the identification of an optimal operating range, characterised by an increased overall efficiency and lower fuel consumption. An optimal range of the delivered steam flow and of the consumed fuel was established, while maximum values of exergetic efficiency are registered.
AUTOCHTHONOUS PRIMARY ENERGY RESOURCES – EVOLUTION AND PROSPECTS
VODA IRINA, TURBATU ADRIAN, RUGINA VASILE
In the first half of the last century Romania was one of the main European primary energy producers and exporters (of oil derivatives, especially). Unfortunately, this is no longer the case.For about 30 years Romania has become a net energy resource importer, and the expectations are not optimistic.The paper presents quantitative information (data) on the primary energy resources production at the international level and by geographical zones, as well as at the national level.The conclusion that can be drawn is that traditional autochthonous primary energy resources may run-off at the life horizon of the present generation. That is why it is necessary to use energy as efficiently as possible.