rss_2.0Latvian Journal of Physics and Technical Sciences FeedSciendo RSS Feed for Latvian Journal of Physics and Technical Sciences Journal of Physics and Technical Sciences 's Cover Study of Marine Diesel Engine Connecting Rod Stud Bolt Crack<abstract> <title style='display:none'>Abstract</title> <p>Failures of marine diesel engine components can lead to serious consequences for a vessel, cargo and the people on board a ship. These consequences can be financial losses, delay in delivery time or a threat to safety of the people on board. This is why it is necessary to learn about connecting rod bolt failures in order to prevent worst-case scenarios.</p> <p>This paper aims at determining the origin, velocity and the duration of fatigue crack development of a diesel alternator engine which suffered a significant failure of one of its mains, not long after a major overhaul had been completed and with less than 1000 running hours having elapsed.</p> <p>It was verified with fatigue rupture of one of the four connecting rod stud bolts. Tensile tests were performed in the remaining connecting rod bolts. During this procedure, another fatigue crack in an adjacent bolt was identified. The probable root case of damage, and at the end some final remarks are presented.</p> </abstract>ARTICLE2021-08-10T00:00:00.000+00:00Gas-Neutralizing and Dust-Suppressing Stemming of Borehole Charges for Increasing the Environmental Safety of Explosion<abstract> <title style='display:none'>Abstract</title> <p>The problem of environmental pollution during the explosive destruction of rocks in order to extract minerals is solved in the article. Two types of borehole charge stemming design have been developed, which, in addition to the function of locking the products of the explosion, allow completely neutralizing harmful gases. The first type is the stemming design, which includes the two-stage purification of harmful gases, formed during the explosive destruction of rocks, and is based on chemisorption of gases by quicklime or production waste and physicochemical sorption (adsorption) by zeolites. Such stemming can provide complete chemical neutralization of NO<sub>2</sub> and CO2, as well as neutralization of CO by zeolites, during the explosion. The second type is stemming design, which includes chemisorption of gases by slaked lime. This type of stemming has a number of advantages over the previous one. It can not only provide complete chemical neutralization of NO<sub>2</sub>, CO<sub>2</sub> and CO, but also allows abandoning zeolites, which significantly reduces the cost of its formation to obtain the effect of “irrigation” of the dust and gas cloud, which reduces the concentration of dust in the air after the explosion to provide a higher degree of conversion. The paper determines quantitative and qualitative characteristics of the adsorbent composition of the two types of stemming depending on the type of explosive, the amount and type of harmful gases formed during explosion, and the parameters of the borehole.</p> </abstract>ARTICLE2021-08-10T00:00:00.000+00:00Methods of Fuzzy Set in Simulation for Predicting Unobserved States of the Ecological and Geoengineering Systems<abstract> <title style='display:none'>Abstract</title> <p>The present paper provides the ways of implementing methods of fuzzy set approach, which contributes to an increase in the accuracy, efficiency and functional flexibility of the complex control and recognition monitoring systems for the environmental and geoengineering system simulation. They are based on data mining methods and may be implemented with the help of intellectual technologies, including the combination of model pluralism, membership functions, methods of nearest neighbour, results of fractal and chaos theories, methods of ensuring robustness and retrospective analysis of the decision tree for success in decision making in similar situations.</p> <p>It is proposed to use the model pluralism to explain a particular information process, which uses a number of adequate models, describing the behavior of objects in the case where each of the model reflects its behavior objectively, but under different circumstances, which are difficult to consider a priori in real time when choosing an adequate model. It is shown that the method of the nearest neighbour should be used if it necessary to identify causal relationships and predict further development of the environmental safety events.</p> </abstract>ARTICLE2021-08-10T00:00:00.000+00:00Power Module Temperature in Simulation of Robotic Manufacturing Application<abstract> <title style='display:none'>Abstract</title> <p>The paper presents a lifetime consumption estimation model of 6 degrees of freedom industrial robot arm. The primary goal of the research is to provide estimated lifetime data of semiconductor power modules of robot axis power supply circuit, providing new opportunities for cost-saving, predictive maintenance, with highly customized input for different manufacturing applications. Evaluation of thermal stress and estimation of isolated gate bipolar transistor current are completed, based on MATLAB model translating KUKA robot program code to electrical energy consumption, which is a novel approach. Energy losses are considered in the model to provide accuracy of the inverter load current. The simulation results prove that lifetime consumption depends on a robot application type, for more agile movement programs with large power amplitudes, such as handling, the degradation in power modules is significant compared to slower applications, such as gluing or welding. Various options for future development are suggested and considered in the paper.</p> </abstract>ARTICLE2021-08-10T00:00:00.000+00:00Development of Methodology for Characterization of Surface Roughness of Solid Metallic Surfaces Using Oil Slippage Method<abstract> <title style='display:none'>Abstract</title> <p>The study employed the phenomenon of friction between liquid droplets and solid metallic surfaces in surface roughness analysis of engineering materials. Five samples of mild steel plate were prepared to different degrees of surface roughness by facing operation. The sample surfaces were analysed to determine the roughness parameters (mean roughness, root mean square roughness, roughness skewness, and roughness kurtosis) and friction coefficient of the surfaces. Oil droplet sliding velocity was determined using the oil slippage test. The friction coefficient of the surfaces increased with increasing roughness parameter which varied from 26.334 µm at friction coefficient = 0.63 to 13.153 µm at friction coefficient = 0.46. The results from oil slippage test showed that the sliding velocity of the oil drop decreased as the friction coefficient of samples increased. At an inclination angle of 30°, sliding velocity varied from 0.51 cm/s at friction coefficient = 0.63 to 0.92 cm/s at friction coefficient = 0.46. Some of the samples exhibited a deviation in the trend of relationship between friction coefficient and sliding velocity which resulted from the variation in peak height of roughness between the sample surfaces. Oil slippage method predicts the surface behaviours of materials based on their surface parameters.</p> </abstract>ARTICLE2021-08-10T00:00:00.000+00:00Experimental Study of the Chaotic Jerk Circuit Application for Chaos Shift Keying<abstract> <title style='display:none'>Abstract</title> <p>The paper presents a study of the chaotic jerk circuit (CJC) employment capabilities for digital communications. The concept of coherent chaos shift keying (CSK) communication system with controlled error feedback chaotic synchronization is proposed for a specific CJC in two modifications. The stability of chaotic synchronization between the two CJCs was evaluated in terms of voltage drop at the input of the slave circuit and the impact of channel noise using simulations and experimental studies.</p> </abstract>ARTICLE2021-08-10T00:00:00.000+00:00CHPP Operation Mode Optimization under Electricity and Gas Market Conditions using a Genetic Algorithm<abstract> <title style='display:none'>Abstract</title> <p>The article presents an operation planning optimisation approach using a genetic algorithm for CHPPs in an urban heat supply zone. Changes in market environment will result in a significant change in energy system planning and operation. For efficient production planning in the liberalized power markets, it is paramount to determine the optimal strategies over a time horizon. Solution of an optimization task of such complexity requires a well-crafted set of tailored modelling, simulation, optimization, and forecasting tools. A well-designed solution is unthinkable without a great number of production units, such as gas turbines, steam turbines, heat-only boilers, and thermal storages, reflected by the optimization model.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00Power Plant Cooperation In District Heating Considering Open Electricity Market<abstract> <title style='display:none'>Abstract</title> <p>The paper analyses the possibilities to form a coalition of several heat energy providers in order to participate in the district heating market considering the open electricity market. Cooperation would allow the participants to better dispatch the existing energy sources and would ensure higher total profit for the participants. The objective function for such a cooperation is provided. To optimise the operation of the coalition, mixed integer linear programming is used, considering constraints of different heating energy market participants and the need to fulfil heating energy balance. If any additional profit is made, it is shared between coalition participants according to the Shapley value, which grants interest for market participants to form the coalition. Case study based on historical hourly data is provided and numerical results are presented in the paper.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00Modelling the Future of the Baltic Energy Systems: A Green Scenario<abstract> <title style='display:none'>Abstract</title> <p>The electricity sector in Europe and in the world is undergoing rapid and profound changes. There is a sharp increase in the capacity of renewable energy sources, coal and nuclear power plants are being closed and new technologies are being introduced. Especially rapid changes are taking place in the energy systems of the Baltic States. Under these conditions, there is an emerging need for new planning tools particularly for the analysis of the power system properties in a long-term perspective. The main contribution of this article lies in the formulation and solution of optimization problems that arise when planning the development of power systems in the Baltic States. To solve this problem, it is necessary to use models of various power plants and make a number of assumptions, the justification of which requires the following actions: to briefly review the current situation of the production and demand of energy in the Baltic power systems; to conduct an overview of the Baltic interconnections and their development; to make forecasts of energy prices, water inflow, energy production and demand; to set and solve the problems of optimization of power plant operation modes; to demonstrate the possibility and limitations of the developed tools on the basis of real-life and forecast data. In this paper, a case study is performed using the main components of the overall modelling framework being developed. It focuses on the Baltic power systems in 2050 under the conditions of significant expansion in the installed capacity of renewable energy sources (RESs) and diminished fossil fuel power plant activity. The resulting electricity generation mix and trade balance with neighbouring countries is assessed, showing that even with significant RES expansion, the Baltic countries remain net importers and because of the intermittency of RESs, there are hours within the year when the demand cannot be met.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00Heat Load Numerical Prediction for District Heating System Operational Control<abstract> <title style='display:none'>Abstract</title> <p>To develop an advanced control of thermal energy supply for domestic heating, a number of new challenges need to be solved, such as the emerging need to plan operation in accordance with an energy market-based environment. However, to move towards this goal, it is necessary to develop forecasting tools for short- and long-term planning, taking into account data about the operation of existing heating systems. The paper considers the real operational parameters of five different heating networks in Latvia over a period of five years. The application of regression analysis for heating load dependency on ambient temperature results in the formulation of normalized slope for the regression curves of the studied systems. The value of this parameter, the normalized slope, allows describing the performance of particular heating systems. Moreover, a heat load forecasting approach is presented by an application of multiple regression methods. This short-term (day-ahead) forecasting tool is tested on data from a relatively small district heating system with an average load of 20 MW at ambient temperature of 0 °C. The deviations of the actual heat load demand from the one forecasted with various training data set sizes and polynomial orders are evaluated for two testing periods in January of 2018. Forecast accuracy is assessed by two parameters – mean absolute percentage error and normalized mean bias error.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00The Natural Gas as a Sustainable Fuel Atlernative in Latvia<abstract> <title style='display:none'>Abstract</title> <p>Despite various benefits that the natural gas mobility can provide, CNG (hereinafter – compressed natural gas) and LNG (hereinafter – liquified natural gas) filling infrastructure both in Latvia and the Baltic States as a whole is still at the stage of active development. As a result, the natural gas fuelled vehicle fleet comprises less than 1 % of all registered road vehicles in the Baltics, but, with regards to transport and climate policies of the European Union (hereinafter – the EU), it has a significant potential for further growth.</p> <p>In order to estimate the perspectives of mobility of natural gas, including bioCNG and liquified biomethane (hereinafter – LBM), CNG has been chosen and analysed as a possible alternative fuel in Latvia with its environmental and economic benefits and payback distance for CNG vehicles compared to petrol and diesel cars. The review of various types of CNG filling stations is also presented, along with information on operating tax rates and currently registered vehicles divided by types of fuel in Latvia.</p> <p>It was established that with the Latvian fuel price reference of the late 2020, exploitation of CNG-powered vehicle was by 24 % cheaper per kilometre in comparison with diesel and by 66 % cheaper in comparison with petrol vehicles. CNG vehicles have smaller operational taxes, since they are based on carbon dioxide (hereinafter – CO) emissions, which are lower for CNG-powered vehicles. Calculation results also indicate that CNG vehicle payback time may fall within the warrant period, if at least 57650 kilometres as an alternative to a petrol vehicle or 71 531 kilometres as an alternative to a diesel vehicle are driven by it.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00Heat Pump Optimization Strategies for Participation in Price-Controlled Demand Response in the Latvian Electricity Market<abstract> <title style='display:none'>Abstract</title> <p>Improved end-user engagement is considered to be a key factor in decarbonization efforts towards climate neutral energy systems. While first adopters are already actively seeking ways how to optimize their energy consumption, a true shift in consumer behaviour can only be achieved if the financial benefits are well established and presented.</p> <p>The study aims at estimating the economic performance of end-user engagement in provision of demand response services using air-to-air heat pumps as the underlying technology. The results of the paper help evaluate in a real data setting whether the existing market framework provides sufficient incentives to facilitate end-user participation in the demand response service.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00A Review: The Energy Poverty Issue in the European Union and Latvia<abstract> <title style='display:none'>Abstract</title> <p>Energy poverty is a growing concern in the European Union. Following energy market liberalization, the problem of energy affordability has entered the political discussion, making it necessary to estimate its dimensions, develop and implement a policy and means for its mitigation. To evaluate the situation in Latvia, the paper reviews the way energy poverty is currently defined and measured, investigating the advantages and shortcomings of various definitions and approaches. It then provides a brief analysis of energy poverty in three char-acterising dimensions: low income, high costs of energy services and unsatisfactory housing conditions (primarily related to energy efficiency aspects), using available statistical data. The characterising indicators of energy poverty are compared with the EU average values. Finally, this paper highlights individual policy measures for diminishing energy poverty.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00The Creation of the Integrated Natural Gas Market in the Baltic Region and its Legal Implications<abstract> <title style='display:none'>Abstract</title> <p>A common natural gas market in the Baltic region, which is in operation since 1 January 2020, means a single entry–exit tariff system for the natural gas transmission among Finland, Estonia, Latvia, and a common Latvian–Estonian balancing zone. Finland joined the market with a separate balancing zone, certain rules, contracts, invoices and billing, with a decision for full integration to be taken not earlier than in 2022. Lithuania is not currently the common market participant, because it is not ready to join it with such revenue splitting conditions as Finland, Estonia and Latvia. But still common entry–exit tariff zone countries are actively working to find a viable solution for market expansion. Lithuania and other neighbouring Member States of the European Union (hereinafter – the EU), first and foremost, Poland, are welcome to join.</p> <p>The creation of an integrated regional natural gas market in the Baltics in the long term will stimulate the interest of traders in the region, strengthen security of supply and improve market liquidity. Increased market competition, predictable prices in the long term, transparent tariffs, digital communication and customer-oriented business strategies are just a small part of benefits that will inevitably develop with time.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00Assessment of PV Integration in the Industrial and Residential Sector under Energy Market Conditions<abstract> <title style='display:none'>Abstract</title> <p>The paper assesses the integration of solar photovoltaic technology in the industrial and residential sectors under energy market conditions. The aim is to determine and compare the payback period for the use of solar photovoltaic technology between the industrial and residential sectors, taking into account the application of optimal load scheduling and level of direct consumption. The industrial sector is represented by a glassware company. Installing PV technologies for a larger area and power is cheaper than installing low-power solar photovoltaic technologies. In addition, direct consumption has significant benefit due to high network service tariffs.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00Energy Transition of the Baltic States: Problems and Solutions<abstract> <title style='display:none'>Abstract</title> <p>The importance of the climate change problem is recognised by the governments of the overwhelming majority of the world’s countries. To bring additional attention and enable more concrete action, in a number of countries and municipalities the issue has been declared a climate emergency. The need to solve this problem predetermines the task of replacing fossil energy sources with renewable alternatives. The process of the ongoing transformation is called energy transition. It includes transformation of all the energy-intensive sectors of economic activity: power generation, supply and consumption, heat generation and supply, electrification of transport, agriculture and households.</p> <p>The main goal of the energy transition is obvious – it is necessary to reduce the emissions of carbon dioxide into the atmosphere. The main sources of energy used to achieve this goal in power generation are wind and solar energy. Even though the goal is unambiguously defined and the way to achieve it seems evident, it is already clear that a number of serious problems and obstacles have arisen. They are caused by the emergence of additional objectives that must be achieved and constraints that need to be satisfied in the process of the required transformations. Indeed, the transition should be carried out taking into account power system properties describing techno-economic efficiency, reliability, stability, adequacy, etc. This list can be expanded easily. It should be noted that the additional objectives are not less important than the overarching goal. Along with reducing emissions, it is also necessary to improve energy supply reliability, its availability and affordability for all the segments of the population as well as maintain the security of the energy supply infrastructure and processes.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00Simplified Model for Evaluation of Hydropower Plant Conversion into Pumped Storage Hydropower Plant<abstract> <title style='display:none'>Abstract</title> <p>Increasing capacity of intermittent generation brings new challenges to balance demand and supply in power systems. With retirement of conventional fossil generation, the role of energy storage is increasing. One of the most competitive storage technologies is pumped storage hydropower plant (PSHP). Usually, such PSHPs are constructed as green field solutions, but in some cases conversion of a hydropower plant into a pump storage hydropower plant by building a pump station is possible. To evaluate the feasibility of such modernisation it is necessary to estimate the benefits of PSHP operation. The simplified model was developed for simulation of charging and discharging cycles of PSHP in Latvian power system and trading electricity in Nord Pool power exchange. The nature of this task is stochastic as the price volatility has a trend to increase with expansion of wind and solar power plant capacity. Results of PSHP operation simulation were then used in the economic model to evaluate the feasibility of the proposed conversion.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00A Linearized Numerical Solution for Steady-State Simulations of Gas Networks<abstract> <title style='display:none'>Abstract</title> <p>Considering the changes of gas transmission system (hereinafter – GTS) brought about by diversification of gas suppliers, new interconnections with European GTS and implementation of an open electricity market and then an open gas market, a steady-state GTS modelling tool has been developed for future implementation in the risk and resilience analysis and potentially operational planning for different GTS or other purposes. The developed method combines the linearized hydraulic conductivity approach with a technique, derived from a linear electrical circuit analysis and an additional pressure change term for modelling of active non-pipeline elements of GTS. This method also takes into consideration operational limits of compressors and pressure regulators and changes in compressibility factor and gas viscosity based on the gas composition, temperature and pressure. The paper includes part of the results obtained from a validation case study performed for the presented method.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00The Natural Gas Supply of the Latvian Municipality during the Local Energy Crisis<abstract> <title style='display:none'>Abstract</title> <p>Natural gas is an essential element of the Latvian and the Baltic energy portfolio, so its supply disruption can seriously affect the national economy and energy security of our country.</p> <p>The article focuses on a basic case study of the natural gas supply to one of the Latvian municipalities, when the energy crisis is announced. It also marks potential vulnerabilities factors that may cause the natural gas supply shortages or disruption periods of different length for a wide spectrum of the Latvian natural gas consumers – starting with households and finishing with large industrial consumers and energy producers.</p> <p>A legal framework analysis along with an emergency natural gas supply review has been proposed as well, taking into account the actual distribution of the natural gas consumption among the urban energy users, which can be compared with references included into the Cabinet of Ministers Regulation No. 312 “Procedures for the Supply of Energy Users and Sale of Heating Fuel during Declared Energy Crisis and in Case of Endangerment to the State” (hereinafter – Regulation 312).</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00Estimating the Benefit from Independent Aggregation in the Day-Ahead Market<abstract> <title style='display:none'>Abstract</title> <p>As the EU countries are working on adapting the Electricity Directive to allow independent aggregation (IA) of demand response (DR) in all the electricity markets, this paper provides an assessment of potential benefits from DR in the day-ahead market, which has proven particularly challenging for the IA regulatory framework development. The model devised in this study uses data of the public wholesale market price curve from the Nord Pool power exchange to simulate market clearing results with introduction of certain amounts of DR that, via independent aggregation, competes alongside generation and is able to shift the supply curve. The simulated new market equilibrium point allows estimating price reduction capability of demand response, the total system-wide benefits, as well as analysing the potential remuneration mechanisms for independent aggregators and implications on their business models. While the results demonstrated a high value from DR during the peak hours, the overall benefits during average price periods were rather low, thus exposing the unpredictability of the revenue stream and questioning the business case for IA in the day-ahead market. The proposed approach can be used for further analysis of different IA compensation mechanisms, considering the system-wide benefits it brings to the wholesale market.</p> </abstract>ARTICLE2021-06-24T00:00:00.000+00:00en-us-1