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The paper presents a new methodology for the energy security assessment and comparison of various energy development scenarios. Energy security is understood not only as the ability of the energy system to supply energy to consumers under normal conditions and at reasonable prices but also as the system's ability to resist to various potential disturbances arising from both technical and economic as well as from socio-political and geopolitical threats. The paper presents a probabilistic model of disturbance formation and an economic-optimization model of disturbance effects. Energy security is evaluated quantitatively taking into account changes in energy prices and unsupplied energy to consumers caused by the disturbances. The developed methodology was applied for energy security assessment of Lithuanian energy system development scenarios. The first scenario is characterized by the implementation of the liquefied natural gas terminal, electricity connections with Sweden and Poland as well as planned renewable energy development projects in the Lithuanian energy system. However, the majority of electricity is imported, especially after the shutdown of the old units at the Lithuanian power plant. Closed units at the Lithuanian power plant are replaced with new combined cycle units in the second scenario. A new nuclear power plant is placed in the third scenario. The combination of the second and third scenarios is done in the fourth scenario: a single gas combined cycle unit is installed and the nuclear power plant is placed afterward. Despite considerable investments in the nuclear power plant and the combined cycle unit, energy security is highest in the fourth scenario. [ABSTRACT FROM AUTHOR]

A comprehensive analysis of the final energy consumption trends, preparation of energy demand forecasts and application of modern energy planning methods and mathematical models are very important stages of energy research directed to the preparation of studies on future development and operation of the energy sector and strategic energy policy documents as well as for the justification of rational energy development provisions. The aim of this paper is to summarise experience of the Laboratory of Energy Systems Research on energy planning, to present some findings from the major studies on long-term development and operation of the energy sector and separate energy systems and to discuss the role of mathematical modelling tools focused on the creation of the strategic energy planning system taking into consideration a necessity to meet ambitious goals of the EU on the deployment of renewable energy sources and requirements of climate mitigation policy, to react to global challenges. [ABSTRACT FROM AUTHOR]

The paper deals with the issue of the small business in the renewable energy field. The experience of the renewable energy leaders shows that the exploitation of the potential of renewable energy sources allows to overcome the dependence on the energy import, stimulates economic growth, and enables the creation of new workplaces as well as opening the prospects for the scientific and technological progress. A very healthy solution would be a promotion of "green and small" business. Therefore there is given an analysis of the main political, economic, social, and technological assumptions of "green and small" business development and its evaluation in the paper. [ABSTRACT FROM AUTHOR]

The aim of the paper is to present probabilistic energy security methodology that allows to analyse the impact of various risk (technical, economic, socio-political) consequences on energy security. The methodology is presented in two parts: the formation of disturbance from the threat model and the disrupted energy system development model. The calculations are made on the basis of the probabilistic safety analysis. The paper presents a general energy system model, describes elements of its concept (threat realization, disturbance, barrier, consequence) and introduces assessment indicators of energy system consequences after threat realization. The company Kaunas Energy is chosen for the demonstration of the method. A few hypothetical system development scenarios for one disturbance -- full gas supply disruption -- are researched. The scenarios cover a wide range of investments into the supply of heat -- both in the reconstruction of Kaunas CHP plant and construction of biomass boilers. According to the created technology, different heating supply development scenarios are compared among each other and advantages of free heat production market are shown. [ABSTRACT FROM AUTHOR]

The paper deals with climate change mitigation policies aiming at household energy savings via behavioral changes. Currently, the Lithuanian climate change mitigation policy is focused on large and expensive supply-side projects such as construction of a new nuclear power plant or carbon capture and storage. At the same time, there is a huge energy saving and GHG emission reduction potential in the household sector, which can be realized at no costs. The aim of the paper is to analyze the behavioral theories and models and their application to energy saving behavior, and to select the best climate change mitigation measures targeting at behavioral changes of Lithuanian households, with the aim to reduce GHG emissions in this sector. [ABSTRACT FROM AUTHOR]

The Jurbarkas regional municipality (Jurbarkas region till 1995) lies in the south-west of Lithuania, in Tauragė County, on the right bank of the Nemunas river. The area of the municipality is 1507 sq. km (or 2.3% of the total Lithuania's area), population appr. 360,000 (1.1% of the total Lithuania's population).Various plans regarding the industrialization of the Jurbarkas region existed during the period 1958-1970: a location was selected for the construction of the Mituva nuclear power plant, the project on the construction of a new hydro-power station (Coвeтскaя ΓЭC) on the Nemunas river with the capacity 205 MW, terms of reference were elaborated for construction of an oil refinery with a CHP plant in Jurbarkas. Neither of these projects were implemented; thus, cultivation and processing of agricultural production traditionally dominates in the Jurbarkas region. Only 0.1% of the Lithuanian industrial production was produced in Jurbarkas regional municipality in 2003. Small scale boiler-houses prevail in the heat sector, with only several larger ones. The paper provides an expert analysis data on the functioning of a part of small-scale boiler-houses during 1993-2007. It discusses the development of boilers' stock, fuel types, heat tariffs, firewood prices. The paper also presents the moisture content in wood fuel and the cost of heat, fuel accountancy and other problems in the low-capacity boilers. [ABSTRACT FROM AUTHOR]

The paper investigates cases of separate and combined heat and power generation, providing data for comparison of their energy efficiency. It was shown that the official translation of the Directive of the European Parliament and of the Council 2004/8/EC from February 11, 2004 into the Lithuanian language has used the incorrect concept of "thermofication" instead of "cogeneration". The paper shows various possibilities for the use of cogeneration technologies presented in Annex I of the Directive, on the "power capacity vs. electric efficiency" axes. The paper provides data on companies producing microturbines and discusses possibilities to use microturbines in various fields of economic activity. [ABSTRACT FROM AUTHOR]

Lithuania plans to construct a near-surface repository for disposal of short-lived low- and intermediate-level waste. The reference design of the repository has already been prepared. Based on the geological investigations, three preliminary sites were selected. In order to assess the impact of the repository on man and environment and to determine whether the planned activity is safe in the selected site, environmental impact assessment has been performed. Assessment of potential releases of radionuclides by the water pathway and human exposure is part of the environmental impact assessment. Radionuclide releases for the Galilauke site was evaluated in the first paper from the series "Assessment of Radionuclide Migration from the Near-surface Repository Planned in Lithuania" [1].This paper presents the modelling of potential radionuclide release from the repository and uncertainty analysis of the results for the Apvardai site. Two radionuclide migration scenarios were analysed: radionuclide discharge to a well and to Lake Apvardai. It has been demonstrated that the conservatively estimated impact of potential radionuclide migration from the planned repository is below the dose constrain established by the Lithuanian regulations. The biggest impact arises from the radionuclide 14C. [ABSTRACT FROM AUTHOR]

The paper deals with the problems of small cogeneration at the consumer side as the development of distributed generation as one of the rational directions. The differences between CHPs in the district heating sector and small CHPs constructed by consumers are described. Different support schemes are prepared for promotion of CHPs in the district heating sector. Unfortunately, cogeneration effect in the district heating utilities is not shared with consumers in an appropriate way. Distributed CHPs constructed by consumers are a more attractive alternative for electricity and heat generation. However, numerous barriers for the development of such CHPs is a common issue not only in Lithuania, but in other European countries as well. The major problems are originated, as outlined in this paper, by the conflict of business interests between network utilities and consumers. Based on the existing legal basis, network utilities can impose unfavourable conditions on the development of such CHPs and their integration into a power system. Differences between the Lithuanian legal basis and the cogeneration directive are discussed in the paper. Recommendations to mitigate the technical, business and regulatory barriers for integration of distributed generation are presented. [ABSTRACT FROM AUTHOR]

The paper describes the simulation of MASP-n experiments were performed in the MISTRA test facility using the COCOSYS lumped-parameter code. The work is performed within the program for investigation of spray interaction with the atmosphere of containments of nuclear power plants, which is organized in the network of the SARNET competence. The paper presents the developed model of a MISTRA test facility for the COCOSYS code and the results of the analysis. The parametric calculations helped to determine the most important parameters influencing the calculated depressurization rate in the MISTRA test facility during MASP-n experiments. [ABSTRACT FROM AUTHOR]

Processes occurring during the reactor operation and accidents change the thermal, chemical and other properties in nuclear fuel elements. This paper describes the processes in the nuclear fuel elements and tools for simulation at these processes. Fuel elements used at the Ignalina NPP were simulated with the FEMAXI-V (Japan) and TESPA-ROD (Germany) codes. The developed models were employed to analyse the processes in fuel elements in case of the large LOCA BDBA. The models and the results of the analysis are presented in the paper. [ABSTRACT FROM AUTHOR]

Energy efficiency in buildings is one of the most important issues in energetics. The energy loads of building service systems consisting of different forms have to be reduced and the methods used should allow identifying quantitative as well as qualitative energy parameters. As the primary stage of building service system optimization, this paper presents energy flow analysis of building service systems. Unlike other researchers, building service systems in this paper are analysed not only under the static situation (designing conditions), but also by examining operational data. This enables a more explicit view on a system's quantitative and qualitative energy requirements. [ABSTRACT FROM AUTHOR]

A uniform load over time is important for an economic and secure operation of the power system infrastructure. An appropriate pricing may stimulate consumers to modify their pattern of electricity usage. Such stimuli can be based on the gain received by operators by reducing the peak load. The paper presents the principles that allow sharing this benefit with consumers by differentiating the average price into different prices according to time intervals. A mathematical model presented in this paper demonstrates how the average price could be differentiated into peak, shoulder and off-peak prices without exceeding the upper limit of the average price. [ABSTRACT FROM AUTHOR]

Construction of small distributed generators close to consumers is one of important features of the power systems development in many countries. This paper describes the current status of distributed generation generation in the EU countries, the advantages and disadvantages of small generators as well as the problems of their connection to a distribution network. The most important factors stimulating the development of distributed generation in many European countries are the following: the growing contribution into electricity production balance of power plants using renewable energy sources which are originally decentralised; development of small (with capacity less than 50 MW) combined heat and power production (cogeneration) power plants; implementation of energy policy directed to promotion of renewable energy sources and cogeneration. The paper focuses on a comparative analysis of distributed generation in the EU countries and its role in the balance of electricity generation. An analysis of the legal and economic environment, as well as principles of regulation of distributed generation and barriers for its penetration is presented. The analysis is based on the methodology of the European research project SOLID-DER financed by the 6th Framework Programme; 17 research institutions, universities and companies are involved into the preparation of this project. [ABSTRACT FROM AUTHOR]

In this paper, are presented the experimental results concerning a model of cellular foam flow heat exchanger. This model of in-line tube bundle consists of five vertical tube lines with six horizontal tubes in each. A statically stable cellular foam flow as a heat transfer carrier was used. Heat transfer from the in-line tube bundle middle line tubes to the vertical downward statically stable cellular foam flow was investigated experimentally. Experimental results of the investigation and the influence of tube position in the middle line of the in-line tube bundle are discussed in this paper. The experimental results were treated analysing relationships between Nusselt (Nu) and Reynolds (Re) numbers with respect to statically stable cellular foam flow volumetric void fraction (β). Experimental heat transfer results of in-line tube bundle middle line tubes in a vertical downward statically stable cellular foam flow were summarized by a criterion equation which enables determination of the average heat transfer intensity rate of the middle line tubes and of all tubes in the tube bundle for different values of volumetric void fractions and parameters of a statically stable cellular foam flow. [ABSTRACT FROM AUTHOR]

The importance of further improvements in differentiation principles in the network pricing was shown in previous papers of the authors. One of such improvements is based on setting a method for calculating the capacity and energy charges. The role of capacity charge in the pricing of network services is discussed taking into consideration the goal -- to create incentives for customers. As is shown in the paper, these price components may be derived from the average price not exceeding the price cap. The relation between capacity charge and other price components is mainly defined by the structure of the cost. The presented model, in addition to the average price level and cost structure, includes other practical aspects important when seeking to calculate capacity and energy charges in the most optimal way. [ABSTRACT FROM AUTHOR]

Various indicators such as heat transporting cost, heat demand density, linear loading of supply pipelines are applied for efficiency evaluation of the DH supply network. The last indicator is informative enough and easy to calculate, however, it isn't universal because depends on the consumer's structure and network configuration. The same indicator value can be found for a big number of small consumers connected to heat sources with short pipelines and for one big distant consumer. Typically, big and small consumers are connected to a single network in real DH systems. The analysis of heat transporting costs presented in the paper was made by exploring the possibilities of the hydraulic-thermal network simulation model. The main idea of the analysis was to define heat supply cost depending on linear load in the two marginal cases -- for a big number of small consumers and for only one big consumer. The paper also presents a correlation between the real heat supply cost of several heat networks in Lithuanian towns and that determined for marginal heat supply cases. [ABSTRACT FROM AUTHOR]

The paper presents an overview of programmable safety systems' software reliability analysis methods of nuclear reactors. As software is an important component ensuring a successful operation of the whole system, software reliability becomes an issue of increased importance. The paper presents several software reliability assessment methodologies used by famous European research institutes. At the moment, there are no widely accepted methods of assessing software reliability. Quantitative software reliability assessment is an even more controversial issue, however, it is necessary when performing probabilistic safety assessment. The paper presents the Bayesian network as a tool for estimating software failure probability. [ABSTRACT FROM AUTHOR]

The work presented in the paper is a sequel of an earlier investigation. The subject of the paper is condensation implosion in a two-phase system due to hydrodynamic instability, which occurs because of the interaction of steam and sub-cooled water flows in a horizontal cylinder (pulser). Here, for the design purposes a modified Jacobs number criterion Ja* is proposed. This criterion defines the divergence of steam-water mixture from the thermal equilibrium. Ja* ≈ 5 is defined as the minimum condition for initiating a condensation implosion event. [ABSTRACT FROM AUTHOR]

The aim of this paper is to set out findings from analysis of the Lithuanian economy and energy sector development and to discuss the main provisions of the draft of the updated National Energy Strategy. The paper presents a short description of tendencies in the Lithuanian economy and energy sector during transition to a free market economy. A significant reduction of final and primary energy intensity in Lithuania is confirmed by analysis based on data published in the recent national and international publications. Positive changes in the energy sector, favourable for implementation of market economy, are discussed. The methodology applied for analysis of the energy sector development and for preparation of the National Energy Strategy is presented. Strategic objectives of the Lithuanian energy sector, the measures to provide for a higher energy security and guidelines for the energy sector development are presented as well. The main provisions in the draft of the updated National Energy Strategy are established taking into consideration the obligations of Lithuania presented in the Treaty of Accession to the EU, the EU directives and other international documents. [ABSTRACT FROM AUTHOR]

Dealing with information systems of wind farms, promoters and designers encounter a problem of choosing the most appropriate communication variant. The information systems of CORBA and COM types still in use do not respond to the new challenges. The paper deals with the distinctive characteristics of communication variants of information systems developed in accordance with the concept of the standard IEC 61400-25 Wind Turbine Generator Systems -- Part 25: Communications for monitoring and control of wind power plants. Three communication variants are subjected to comparison: centralised topology, mixed topology and seamless topology. To evaluate an information system, the relevant criteria have been proposed (such as design cost, investment cost, outage timescale, etc). The evaluation of utility of communication variants is formulated as a multi-criteria problem. The problem is solved by the deterministic method. Seeking to specify the deterministic estimates received, a new probabilistic-statistical multi-criteria method based on normal distribution is proposed. It allows for the "measurement" of uncertainty of expert's input estimates. The application of the method is demonstrated for the problem in question. The results of solution -- the estimates of multi-criteria utility of each communication variants -- are discussed. The paper concludes that the method proposed might be a good instrument for comparison of competing projects, strategies or alternatives. [ABSTRACT FROM AUTHOR]

In Lithuania, the use of biofuel is currently increasing not only for centralized heat generation, but it is also a popular type of fuel for small-scale household furnaces. The main disadvantage of this type of fuel in comparison to combustion of gaseous or liquid fuels is rather high emissions of coarse, fine, and ultrafine solid particles. Long-term exposure to such types of particulate matters causes health problems. Electrostatic precipitation is a very reliable method to decrease particulate emissions from boilers, incinerators, and other industrial processes. This paper presents the results of investigation of the electrostatic precipitator efficiency for a 50 kW boiler when burning biofuel. It was shown that the minimum voltage of the corona discharge is equal to 6 kV. At that voltage, a total collection efficiency of 77% was achieved. At the highest tested voltage (12 kV), the total collection efficiency was about 99%. [ABSTRACT FROM AUTHOR]

In order to understand the processes taking place in a nuclear reactor core during the emergency cooling, for many years world's scientists have been performing experiments and trying to simulate them using various computer codes. This paper presents the modelling results of the QUENCH-3 experiment, their comparison with the experimental data and the influence of modelling parameters on the calculation results. Modelling has been performed using the ASTEC code ICARE module by varying additional contact resistance of heating elements, specific heat and thermal conductivity of zirconium dioxide and the flow rate of cooling water. Two parameters were analyzed during the modelling: temperature at different points of the experimental facility and the overall amount of hydrogen gas generated during the experiment. The analysis showed good correspondence between the modelling and experimental temperatures of the fuel assembly imitator. However, the amount of hydrogen generated in the experiment exceeds twice the mass of hydrogen, which was calculated during the modelling. This indicates that the available computer code version is not designed to simulate the oxidation of zirconium when the fuel assembly is severely damaged. A variation of the additional contact resistance has the greatest influence on the modelling results. Comparison of the modelling results with the experimental data enabled us to assess the created model and to prepare for the modelling of other experiments, performed at the same experimental facility. [ABSTRACT FROM AUTHOR]

Condensation is a phenomenon widely studied for many years. However, the experimental data fragmentation and wide application of simplified theoretical models prevent the consolidation and development of the condensation phenomenon model corresponding to the known reality in all aspects. Both the experimental data and the models are obtained and developed in order to meet the practical needs of the industry first and foremost -- only the most widely used regimes have attracted researchers' attention. However, because fundamental research is very difficult the objectives were usually limited to the optimization of the processes, and other practical tasks. One of not adequately understood and analysed regime is stratified two-phase flow with surface instability induced by direct phase interaction in the interface. This paper presents water temperature profiles measured in stratified co-current two-phase flow (steam--water) inside a short and narrow rectangular channel. Measurements were made at x/h = 9.4; 14.8; 20.4; 39.2 (166, 312, 458, 932 mm) from the beginning of the channel, using a nonintrusive thermography method. The thermography method allows with high resolution and low data uncertainty (±2 °C) measuring the water temperature right at the channel sidewall. The different flow conditions were created in the channel by changing velocities of flowing phases (water 0.014, 0.028 and 0.056, and steam 6, 8, 10 and 12 m/s) and supply water temperature (25 °C). It was found that between different regimes the vertical temperature profiles measured from the interface to the bottom of the channel changed not equally and smoothly. In the tested case the water layer can be virtually divided into 4 zones by height where water temperature changes differently. It was also found that because of the 'condensation-turbulence self-induction' the steam flow momentum transfer to water turbulence occurred not only at the interface (depth of ~1 mm) but reached much deeper. By increasing the velocity of steam and at a constant rate of water flow the starting points of 'condensation-turbulence self-induction' move closer to the beginning of direct vapour--water contact. [ABSTRACT FROM AUTHOR]

There are many forms of support for renewable energy in Lithuania, but all of them focus on the manufacturing sector, while the world focuses on the demand sector and there are many papers dealing with the social assessment of new technologies and the social acceptability of technologies by consumers. Since 1st of January 2013 Lithuanian residents are free to choose their electricity supplier and also support the use of renewable energy resources, that is why it is important to investigate the consumers' willingness to pay for electricity from renewable energy sources in Lithuania and to identify the key factors that determine the preparation of the population to pay for electricity from renewable energy sources. The purpose of this article is to carry out the assessment of Lithuanian population willingness to pay for renewable energy resources and to compare achieved results with studies performed in other countries. [ABSTRACT FROM AUTHOR]

Analysis of the Lithuanian energy sector development over medium and long-term periods and preparation of strategic documents is a complex problem. Comprehensive analysis of energy consumption trends and application of appropriate energy planning tools is required. Forecast of final energy demand should be prepared taking into consideration that favourable preconditions for economic development of the national economy are required. The aim of this paper is to set out findings from the analysis of primary and final energy consumption in lithuania over the period 2000-2012, to discuss the methodology of such analysis, to assess relationships between energy consumption and economic activities, as well as to perform a comparative analysis of energy intensity and indicators of energy consumption in the Baltic States and EU countries. [ABSTRACT FROM AUTHOR]

The current use of solid biomass for heating in Lithuania and further development opportunities as well as environmental impact are analyzed in this paper. The solid biomass potential in 2011 made 1 442 ktoe, and 50.8% of this potential was used in the heating sector. he solid biomass potential should increase 14.6% by 2020 and 67% of this potential should be used in order to achieve the national renewable energy targets (60% for district heating and 80% for heating of individual houses). Achievement of national targets would allow to reduce total greenhouse gas emissions by 6%. he changes in the emissions of the main pollutants would be different. SO2, NOx, solid particles emissions would decrease by 13.1, 3.2% and 28.4%, respectively, however, VOC and CO emissions would increase by 1.3 and 8.2%. [ABSTRACT FROM AUTHOR]

Investigations of mixed convection in channels in a transition region are rather limited therefore in this paper we present the numerical study of mixed convection in the horizontal flat channel in the transition region. Numerical 2D steady state simulations in air flow have been performed by Ansys Fluent code using transition kkl-ω, SST and Re stress-ω models. The performed analysis shows that there are no vortexes in the horizontal flat channel in the analyzed Re and Grq region. The results of numerical modelling have been compared with the results of experiments performed at the same conditions. It was revealed that under significant effect of buoyancy the best correlation with experimental data was obtained when the kkl-ω transition model is used. [ABSTRACT FROM AUTHOR]

This paper analyzes the external costs of electricity generation technologies, which are highly important in order to create an effective policy to reduce the negative effects of energy supply and consumption. The described ExternE methodology allows us to accurately calculate the external energy cycle costs, considering the location of the power station and meteorological conditions. Based on this methodology and using the EcoSense model, the analysis of Lithuania and EU-27 external costs of pollutants emissions into the atmosphere is presented, as well as the external electrical power generation technology cost analysis in Lithuania. The conclusion was made that renewable energy-producing power plants have the lowest external costs, also the external cost comparison of the impact area and the technology life-cycle rate was made. [ABSTRACT FROM AUTHOR]

Liquid and gas two-phase flows are widely applied in energy and industrial sectors. Improvement and sustainable development of the thermal technologies, based on liquid evaporation, require a thorough cognition and ability to control heat and mass transfer processes, occurring in the thermal technologies. For that it is necessary to understand thoroughly the essence of the interaction of transfer processes, which mostly often occurs in changing boundary conditions and which decides the intensity of the transfer processes. The interaction of transfer processes in sprayed water systems is influenced by many factors. To evaluate them, a systematic approach to the whole of combined transfer processes and revealing of the main factors that decide transfer processes are necessary. Thorough cognition of the regularities of the transfer processes that occur in the simplest boundary conditions and consequent evaluation of the influence of more complicated boundary conditions using comparative methods can solve the above mentioned problems. This paper presents the method, which evaluates the intensity of unsteady transfer process interaction in a comparative way. An example of its practical application in the case of water droplet evaporation is given. The influence of one of the most complicated factors - absorption of spectral radiation in semitransparent droplets - on the thermal state and heat transfer of droplets during unsteady evaporation mode is highlighted. [ABSTRACT FROM AUTHOR]

Pricing process is the process of tariffs formation, rates and ratio defining. Pricing order is defined by the Government of the Republic of Lithuania and implemented by institutions, empowered by the state in independent Lithuania. Heat tariffs are estimated using heat tariffs defining methodologies. District heating tariffs are regulated by the Government, however, recently, when heat tariffs were growing considerably due to growing prices for various types of fuel, payments for district heating became the main concern of residents. The paper provides a historical-expert overview of the pricing process and legislation regulating the formation of heat tariffs during the period 1970-2012. [ABSTRACT FROM AUTHOR]

This article examines energy efficiency improvement policy, the main attention being paid to energy efficiency improvements in buildings of households and services sectors as well. The paper analyses the main EU energy policy documents dealing with energy efficiency policy and their targets. The Lithuanian energy policy documents targeting energy efficiency improvement are analyzed and progress in achieving the energy efficiency targets set for Lithuania is assessed. Based on the results and findings of energy saving and the GHG emission reduction potential and costs analyses performed in EU, the costs and GHG emission reduction potential in buildings are generalized. The recommendations for energy efficiency policy improvement in Lithuania are developed based on the Lithuanian energy policy analysis and the findings of energy saving and the GHG emission reduction potential and costs analyses. [ABSTRACT FROM AUTHOR]

It may be argued that society is becoming increasingly demanding for the quality from any activity. Even if it is true it is not easy to assess the quality of various processes as popular economic criteria hardly comply with the concept of sustainable development. Exergy, as an objective indicator of used and transformed energy quality, is used for the evaluation of energy transformation processes in different areas, such as: biology, technology etc. It is not affected by inflation, devaluation, and crisis. The compromise of combination of exergy and economic criteria is defined by exergoeconomics. This paper presents theoretical basics of exergy and exergoeconomic analyses. The exergy and exergoeconomic analyses were performed for 20 MW thermal capacity combined-cycle cogeneration plant. The exergy analysis allowed the identification of elements where the largest exergy losses are formed. The exergoeconomic analysis was conducted to determine costs of such system imperfection economically. Additionally, costs of final products (e. g. heat and electricity) were calculated. [ABSTRACT FROM AUTHOR]

Based on the long-period data series of the Nemunas River runoff, which were approximated by S. Kolupaila in 1930, this paper examines the relationship between the river runoff and an average air temperature of the winter (December--February) season. An inverse correlation between the river runoff and air temperature was found. According to the air temperature and precipitation of the winter period as well as the river runoff of the autumn period, empirical regression models were created for the winter period runoff of the Nemunas River. It was established that the hydro-meteorological conditions typical for the last two decades, often associated with the global warming caused by anthropogenic impacts, were also observed at the beginning of the last century, when the effect of human activities on climate was likely less significant. [ABSTRACT FROM AUTHOR]

The paper overviews the main characteristics of the development and, unfortunately, partial decay of the Lithuanian energy sector (including heat sector) on the basis of legal acts and expert studies. Much attention is given to the period between 1990-1997 when the Supreme Council (later the Seimas) of the Lithuanian Republic and the Government took steps to reform the Lithuanian energy and heat sectors during complicated conditions such as the economic blockade, devaluation of roubles and later tokens, introduction of the national currency, the fast growth of prices for fuel and tariffs for district heating. The necessary legal acts and secondary legislation were adopted, the Ministry of Energy and other responsible institutions were established, which were solving problems in energy and heat sectors in one or another way. The commercial heat cost price for consumers of the Lithuanian energy system was ~0.68 co./kWhth in 1990 and grew to 8.6 ct/kWhth (excl. VAT), which was adopted by the Government of the Republic of Lithuania in 1995 for the planned thermal energy supplied for consumers of the state company "Lietuvos valstybinė energetinė sistema" (Lithuanian State Power System). The average tariff of large heat suppliers selling over 10 GWh of heat/year reached 20.77 ct/kWhth (excl. VAT) in 2010 and is still growing. The tariff for heat in small boiler houses, especially those burning not dried wood fuel, reaches 30.00 ct/kWhth (excl. VAT) and even more. [ABSTRACT FROM AUTHOR]

The decommissioning process of the Ignalina NPP has started at the end of 2004, after the final shutdown of its First-Unit reactor. The near-surface landfill disposal facility will be constructed in order to dispose of the short-lived very low level waste (VLLW), both existing as well as arising in the course of the decommissioning process. Waste will be accumulated in a buffer storage before its disposal. The buffer storage is intended for waste activity measurements, accumulation and safe intermediate storage between campaigns of waste disposal in the disposal units of the landfill facility. The paper presents an evaluation of prognostic radiation doses for the buffer storage personnel directly involved in the handling of radioactive waste packages. Radiation doses for the personnel are evaluated from direct radiation sources (radioactive waste packages during their handling processes) as well as from the radio nuclides existing in the air of the buffer storage premises. Assessment of radiation doses to the personnel has shown that the total annual radiation dose to a separate worker of the buffer storage does not exceed the limiting values established in normative documents. The highest annual dose was found to fall on the health physicist (~9.79 mSv) due to his work peculiarities, while the minimal dose is received by the health physicist assistant (~0.84 mSv). The annual radiation dose from the radionuclides existing in the air of the buffer storage premises is insignificant (~1.24 x 10-4 mSv) as compared with the direct radiation dose from the radioactive waste packages during their handling processes. [ABSTRACT FROM AUTHOR]

The construction of a spent nuclear fuel (SNF) repository in a geological structure will impact the stable geological environment that has settled over centuries, and the disposed off SNF containers will release a residual amount of heat. These changes in the environment of a geological repository will lead to a simultaneous and coupled heat exchange (T), fluids (moisture and air) transfer (H) and mechanical (M) processes. A comprehensive assessment of the latter processes is important for the general safety of the repository. The numerical assessment of the processes around one canister with the RBMK-1500 SNF, disposed off in a hypothetical repository in crystalline rocks, is presented in the paper. Based on the performed analysis, temperature distribution in the system and the highest temperature have been determined, the dynamics of water saturation within the material of engineering barriers and mechanical displacements in the engineering barriers have been assessed. Results of the heat transfer modelling have revealed the importance of coupled heat and hydrodynamic processes for the maximum value of temperature in the engineering barriers, whereas the impact of mechanical processes was insignificant. Moreover, the highest temperature close to the surface of the canister does not exceed the allowable 100 °C. [ABSTRACT FROM AUTHOR]

Automatic generation control (AGC) is the most actual factor in the primary and secondary control of interconnected systems. Its accounting is an integral part of realizing and developing any form of power system control. Without a concrete AGC accounting methodology it is impossible to calculate the profitability of such system implementation in case the necessary regulation power and fuel consumption or equipment wearout are unknown. In the paper, the methodology of AGC accounting is analysed, with calculating the power amounts needed for regulating the internal system or possibly for selling them to neighbouring power systems. [ABSTRACT FROM AUTHOR]

The paper deals with the sustainability assessment of electricity generation technologies in the EU, which was performed by applying the multi-criteria analysis approach. Integrated indicators for sustainability assessment of electricity generation technologies were calculated for specific technologies. These integrated indicators were obtained by summing up the normalized social, economic and environmental indicators for specific electricity generation technologies. The electricity generation technologies were ranked according to their positive impact on sustainable energy development in the EU, based on these integrated indicators. Sustainability assessment indicators for specific technologies were evaluated by applying results of empirical studies conducted in the EU. The sustainability assessment performed in the present study has indicated that the best technologies in terms of sustainability in the energy sector are technologies based on renewables. [ABSTRACT FROM AUTHOR]

Neutron power control is the key to the reactor operation. he reactivity coefficients and effects are the main measures to estimate the reactor control and safety. These characteristics outline the reactor behaviour during its usual exploitation and in accident events. Reactor safety and implements to ensure it are estimated by these parameters. he reactivity coefficients and effects quantify the effect exerted by various parameters (e. g., graphite fuel temperature, amount of steam) on the core neutron activity. Many modifications of the RBMK-1500 reactor core at the Ignalina NPP were made during the last decade. he reactor core modifications such as load of more enriched fuel with a burnable absorber and the new construction of control rods improved the reactivity coefficients. he neutron-physical parameters of various reactor core states under various fuel loads and with new-construction control rods were calculated using QUABOX / CUBBOX-HYCA software. Changes of the reactivity coefficients and their effects are quantified in this paper. [ABSTRACT FROM AUTHOR]

The energy retention problems of heated buildings are treated in the paper. The potential of heat transferred through the building envelope is higher in comparison with the environmental potential at outdoor temperature. Therefore, the idea of endothermic heating with a possibility to avoid heat losses by heat recovery into premises after regeneration in the heat pump is proposed. At present, the ground of outdoor air is used as a source of low potential energy in heat pumps of engineering systems in buildings. Authors have suggested to apply the heat transferred through the building envelope as an energy source in absorbers located in the structure of the building envelope. If all heat losses are recovered, the building will become an adiabatic space. In this case, heat will circulate within the building, generating an endothermic process with some external energy needed for heat pump action. Heat losses in such a building would be almost eliminated at the operation of the proposed heating system. he advantages of the proposed heating system: heat losses of buildings into the environment are eliminated, thermal environmental pollution and greenhouse gas emission are significantly reduced, energy consumption in a building is decreased, especially in comparison with traditional heating systems. An investigation of the experimental model of a building with the endothermic heating system is foreseen at the Institute of Architecture and Construction of the Kaunas University of Technology. [ABSTRACT FROM AUTHOR]

This is the third paper from the series called "Numerical Modelling of Neutron Activation Processes in Reactor RBMK-1500 Structural Elements". In this work, activation processes in reactor RBMK-1500 structural elements, namely in fuel channels, are further analysed using modelled neutron fluxes. For this purpose, the 3D numerical model of the Ignalina NPP reactor RBMK-1500 one-lattice cell segment was developed, enveloping a graphite column with other elements inside it, shield and support plates, top and bottom metal structures with serpentinite, and other structures. Using the proposed model with the MCNP computer code, neutron fluxes in the reactor structures under analysis were estimated. Then, using the estimated neutron fluxes and neutron activation estimation models, the activity levels in fuel channels and their dependence on the concentration of initial impurities and on the cooling time after the final reactor shutdown were estimated using the ORIGEN-S computer code. The revised data on neutron activation in fuel channels employing the modelled neutron fluxes and the real reactor operating history show that the distribution of total activity along the fuel channel corresponds to the distribution of the thermal neutron flux, and their activity values are lower than those of modelling the constant reactor operating history for 20 years at its nominal power. [ABSTRACT FROM AUTHOR]

The Lithuanian power system was connected to the Joint North-West power system on October 12, 1962. The daily loading graph was the most uneven one compared to other power systems in the former USSR. In order to even out the daily loadings of the power system graph in Lithuania a regulatory system was established, which consisted of thermal accumulative electrode 10 kV and 0.4 kV plants. These plants used "night-time" power and produced heat for heating buildings and preparing hot water. The total power capacity of electrode boilers installed in such plants during several years reached nearly 1500 MW. Unfortunately, for various reasons, the group of such "night-time" consumers was destroyed. This paper provides a historical analysis of the design, construction and decline of the mentioned thermal accumulative electrode 10 kV and 0.4 kV plants. [ABSTRACT FROM AUTHOR]

The paper deals with the enhancement of transfer capabilities of a transmission system by adding the FACTS (flexible alternate current transmission system) controller. The IEEE 14 bus test system was chosen for the enhancement analysis purposes. In order to be matched with the FACTS, the original system was modified to an upgraded voltage system with the 230-kV (buses 1-5) and 132-kV grids (buses 6, 9-14). The power flow simulations showed that the transfer capability of the modified system from the swing bus 1 to 132-kV amounts to 307 MW. The introduction of a FACTS controller of UPFC type (unified power flow controller) allowed for the enhancement of transfer capability by 45 MW, i. e. by 15%. The proper choice of the transmission line within the system for the integration of the FACTS controller is of crucial importance for the level of the enhancement. [ABSTRACT FROM AUTHOR]

In this paper, we present results on numerical investigation of local opposing mixed convection heat transfer in a vertical flat channel with one-side heating in the laminar and vortex (transitional) regions. The investigations were performed in the steady state airflow of different pressures (0.1, 0.2 and 0.4 MPa) in the Rein range from 1.5 x 10³ to 2.5 x 10³ and Grq from 1.8 x 105 to 2.6 x 107. The value of heat flux on the wall was widely varied in order to achieve different buoyancy effect. Numerical modelling with one-side heating demonstrates that under a small buoyancy effect, as in case of symmetrical heating, there are only small transformations in the velocity profile, but the flow is oriented downward. With an increase of buoyancy forces, the flow separation from the heated wall occurs at some distance from the beginning of the heated channel section. With a further increase of buoyancy, the position of flow separation moves towards the beginning of the heated section. The channel wall temperature noticeably decreases at the flow separation point (due to occurrence of vortices at the wall). Relative heat transfer along the channel was also analysed. In case of laminar mixed convection for the one-side heating case, relative heat transfer along the channel decreased more significantly (in comparison with forced convection) than in case of two-side heating. Correlations for the determination of the position of flow separation from the wall (loss of stability of the flow) and heat transfer in case of one-side heating were also proposed. [ABSTRACT FROM AUTHOR]

Experimental investigations of aiding mixed convection heat transfer in a vertical flat channel in the transition region for different airflow pressures were performed at the Lithuanian Energy Institute to get an exhaustive information on the buoyancy effect. The results of numerical modelling for experimental regimes in case of the airflow pressure p = 0.2 MPa are presented in this paper. Numerical two-dimentional simulations using the FLUENT 6.2 code were performed for three Reynolds numbers - Rein = 2.0 x 10³, 2.6 x 10³, 2.9 x 10³ - with the Grq numbers Grq in = 3.9 x 108, 4.7 x 108, 5 x 108, respectively. Zones with stable and unstable vortex flows were analysed in detail. The results of the numerical modelling of heat transfer were compared with experimental data. When the laminar flow is in the hydrodynamic stabilization region, the results of the numerical modelling of heat transfer in the calorimetric region are in good agreement with experimental data. [ABSTRACT FROM AUTHOR]

The paper presents experiments of steam--water flow in a rectangular channel (1.2 m long, 0.1 m high and 0.02 m wide). The water depth was kept at 0.025 m. The steam velocity profiles were measured when the average velocity of steam flow was 4, 6, and 8 m/s (Re = 6000, 9000, and 12000). The velocity profiles where measured at different steam condensation intensity using a Pitot tube at a distance of 1 m from the beginning of the channel. The condensation intensity was modified by the cooling water flow rate. This work is associated with the research of interfacial shear in steam--water flow. The main purpose was determination of condensation impact on interfacial shear. [ABSTRACT FROM AUTHOR]

Construction of a Landfill type repository is planned at the Ignalina NPP site for disposal of very-low-level radioactive waste generated during the operation and decommissioning of the Ignalina NPP. Two alternative sites, relatively named Šiaurinė and Pietinė, are considered for the repository. The second paper of the series presents an analysis of radionuclide dispersion in the atmosphere as a result of a possible fire in the repository. The radiological impact on two critical groups is analysed. One critical group (firemen brigade) is assumed to be located in the sanitary protection zone (SPZ) of the Ignalina NPP. The other group consists of inhabitants living on the border of the SPZ. The annual effective dose to the members of each critical group was evaluated. It was demonstrated that the exposure dose to a fireman, caused by fire in the repository, would be higher in case of the Šiaurinė site by a factor of 3.2-3.8 (depending on atmospheric stability class). The exposure dose as a result of fire in the Landfill repository to local people living close to the SPZ border would be higher by a factor of 1.6-2.0 in case of the Pietinė site. The influence of the uncertainties of parameters describing the biosphere was analysed by a probabilistic assessment. It was demonstrated that the lowest and the highest effective dose values for a worker can differ from the mean value by about 19%. The lowest and the highest effective dose values for the local people can differ from the mean value by 36% and 59% respectively. [ABSTRACT FROM AUTHOR]

The aim of the work was to explore the prevailing peculiarities of heat transfer and gas dynamics during the exothermic CO oxidation reaction in separate layers of catalytic monolithic reactor (CMR) manufactured from stainless steel sheets deposited by the plasma spray technology as a catalytic coating containing CuO. The paper discusses the factors that were experimentally assessed to affect heat transfer in the catalytic monolithic reactor. Thermal processes in the CMR were found to be directly related to changes in the gas mixture flow parameters, the initial CO concentration and the reaction duration. While comparing the obtained results with results reported by other researchers, contradictory regularities of temperature distribution were noted. [ABSTRACT FROM AUTHOR]

Market restructuring problems, which occur in the countries in transition from centralized planning towards market economics, are specific of every single country. They usually depend on the formed and the inherited structure of economy, the rates and trends of reforms, as well as on the geopolitical situation and many other objective factors. Nevertheless, the reformation of the economy towards market economics in all East and Central European countries has much in common. The general fundamental laws of economics describe the consequences of reforms and can be used for projection of future trends. Even such subjective factors as enterprise and corruption resistance can be wel forecasted in case the required information is available. The paper provides a comparison of municipal district heating sectors in two post-Soviet countries Ukraine and Lithuania with evaluating the consequences and perspectives of these socially significant and at the same time the most problematic energy sectors. [ABSTRACT FROM AUTHOR]