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Papers by Mikelis Dzikevics

2021 IEEE 62nd International Scientific Conference on Power and Electrical Engineering of Riga Technical University (RTUCON)

Solar thermal heating system relies on efficient use of available solar radiation. Traditional sy... more Solar thermal heating system relies on efficient use of available solar radiation. Traditional systems use temperature sensors to directly measure actual parameters and controls are used that react accordingly. In this article use of model predictive control is analyzed to use the temperature of the water leaving the top of the tank (load temperature), which increases with an increase in solar radiation, as a control signal for lowering setpoint for auxiliary heater placed inside the storage tank. Results show that the use of prediction horizon 24–72 h increase solar fraction and reduce necessary auxiliary energy of the system. Monthly analysis shows that a longer prediction horizon performs better in most cases.

Energy Procedia, 2015

Mathematical model has been developed to assess the effects of using phase change materials (PCM)... more Mathematical model has been developed to assess the effects of using phase change materials (PCM) in a fully mixed water accumulation tank. Packed bed system of spheres with a diameter of 40 mm have been considered as an option to increase energy storage density. A continuous phase model has been applied to analyse the influence of phase change during a charging and discharging processes. The methodology for calculating energy mass flow, density of water, heat transfer between layers, temperature for each time step and energy transferred to PCM is given. Single type of PCM with melting temperature of 55 °C and multiple type PCM system (65, 55, 45 and 35 °C) are compared. It is found that multiple type PCM system compared to only water and single type PCM systems, provide lower return temperatures and higher energy density.

Environmental and Climate Technologies

With the increase of renewable energy sources, the control methods of the energy systems are an i... more With the increase of renewable energy sources, the control methods of the energy systems are an increasingly important topic. Control methods have evolved from simple on/off controllers to methods that utilize artificial intelligence and can have a predictive nature. This paper investigates the control methods that are particular for solar thermal systems. A bibliometric method is applied to analyse scientific literature related to the specific application from the Web of Science database. Results show that recent developments in control methods focus on solar thermal to power and hybrid systems while district heating is a potential research gap. Annual publication trends, country, journal and keyword analysis is presented.

The use of biofuels for heating purposes is beneficial from a greenhouse gas emission point of vi... more The use of biofuels for heating purposes is beneficial from a greenhouse gas emission point of view. But combustion of solid biofuels typically is related with high emission rates of CO, NOx, PAHs, VOCs and particle matter. The most important factor that is affecting the formation of harmful emissions is the way the combustion process is organised. The amount of air injected and approach for the air supply system, are the most important factors affecting combustion process. Air staging is one of the most effective technical solutions for achieving complete combustion and low emissions. The main idea of air staging is to inject air into different zones of a combustion process. The main goal of this study is to optimise pellet combustion process in a 500 kW boiler with staged air supply. The research is based on on-site experiments and application of scientific instrumentation. Fly- away unburned fuel particles were discovered during the on-site experiments. Reduction of the amount of...

The research on solar heating systems often is faced with choice of carrying out experiments in r... more The research on solar heating systems often is faced with choice of carrying out experiments in real systems with changing parameters or to use modelling software with constant parameters but many undefined parameters or assumptions. The design of experimental system for simulating solar heat accumulation is proposed in this paper. The proposed design allows testing of phase change materials which provide higher thermal density compared to water. Results from computational fluid dynamic simulations carried out by other studies have been analysed for implementation into designing of the tank. All of these factors have been taken into account to create a system that resembles real case and can simulate for a long periods of time.

Energy Procedia, Sep 1, 2017

Abstract Biomass takes an important place in the Latvian primary energy source balance. In the co... more Abstract Biomass takes an important place in the Latvian primary energy source balance. In the coming years steeper increase of the use of biomass for the production of heat can be predicted, in order to ensure the proportion of energy produced from renewable energy resources to 40 % in 2020. However, the use of biomass has increased the risk of environmental pollution, mainly with solid particles. In order to prevent an increase in quantity of particulate matter in the atmosphere, flue gas treatment is important, with special attention to small capacity boiler equipment. The research provides insight into innovative technologies for the flue gas treatment – fog unit. Technology comparison with another widely used flue gas purification methods are given in the article.

High Temperatures. High Pressures, 1994

ABSTRACT The values of the coefficients of thermal expansion and compressibility, isobaric heat c... more ABSTRACT The values of the coefficients of thermal expansion and compressibility, isobaric heat capacity and thermal diffusivity of three brominated saturated hydrocarbons of butyl bromide, hexyl bromide and heptyl bromide are measured in a heat-conducting calorimeter at a temperature of 298–363 K in the pressure range of 0.098–147 MPa. The experimental data on the isobaric heat capacity are compared to the calculation results. Generalized dependences are suggested to determine the heat capacity and thermal diffusivity.

Environmental and Climate Technologies

This work is a continuation of the article “Methods for Determining the Performance and Efficienc... more This work is a continuation of the article “Methods for Determining the Performance and Efficiency Parameters of the Flue-gas Condenser Sedimentation Tank”. During the experimental determination of Particulate Matter (PM) physical parameters, a described methodology was used. The results obtained affected the choice of water purification technology. Sedimentation technology was selected but provided that a filter element should be present in the installation. The article describes the types of industrial sedimentation tanks used more often. In condition that the system should be compact, while at the same time the purification efficiency rate should be high, the new suitable design of the water treatment system was developed.

Environmental and Climate Technologies

One of the main pollution types is air pollution, which has a significant impact on the surroundi... more One of the main pollution types is air pollution, which has a significant impact on the surrounding environment and on living beings. Major source of air pollution is combustion processes. There are many flue gas treatment technologies around the world. In this paper a new, innovative flue gas treatment technology – fog unit – is introduced. The goal of the fog unit is to treat flue gases that are emitted from households. In the European Union, including Latvia, at the beginning of 2020, a directive will come into effect that will set limits for emissions and the effectiveness for incinerators in households. The main focus of this study was to determine the most optimal operating mode for the fog unit by changing different operating parameters: sprayed water temperature, sprayed water flowrate and types of nozzles (drop diameters). Results show that the most optimal operating mode in terms of flue gas treatment efficiency and recovered energy is at water temperature: 20 °C, sprayed ...

Environmental and Climate Technologies

Increase in solar fraction has been noted as one of the main goals for wider application of domes... more Increase in solar fraction has been noted as one of the main goals for wider application of domestic solar thermal systems. To increase solar fraction, higher energy density thermal storage availability is a key point. In this paper phase change materials have been analysed as part of a domestic solar thermal system. Sensitivity analysis of annual simulation in TRNSYS with climate data of Riga, Latvia is used. The paper also explores better methods for evaluating phase change material (PCM) performance based on temperature measurements in PCM. The results showed that the melting point of PCM and temperature set point of an auxiliary heater have the highest sensitivity of aspects analysed in the paper. It also reports that the coefficient of variation of energy in PCM correlates well with solar fraction and can be used as a parameter to evaluate PCM’s suitability for certain applications.

Sensitivity Analysis of Packed Bed Phase Change Material Thermal Storage for Domestic Solar Thermal System, 2020

Increase in solar fraction has been noted as one of the main goals for wider application of domes... more Increase in solar fraction has been noted as one of the main goals for wider application of domestic solar thermal systems. To increase solar fraction, higher energy density thermal storage availability is a key point. In this paper phase change materials have been analysed as part of a domestic solar thermal system. Sensitivity analysis of annual simulation in TRNSYS with climate data of Riga, Latvia is used. The paper also explores better methods for evaluating phase change material (PCM) performance based on temperature measurements in PCM. The results showed that the melting point of PCM and temperature set point of an auxiliary heater have the highest sensitivity of aspects analysed in the paper. It also reports that the coefficient of variation of energy in PCM correlates well with solar fraction and can be used as a parameter to evaluate PCM's suitability for certain applications.

conferences by Mikelis Dzikevics

2021 IEEE 62nd International Scientific Conference on Power and Electrical Engineering of Riga Technical University (RTUCON)

Solar thermal heating system relies on efficient use of available solar radiation. Traditional sy... more Solar thermal heating system relies on efficient use of available solar radiation. Traditional systems use temperature sensors to directly measure actual parameters and controls are used that react accordingly. In this article use of model predictive control is analyzed to use the temperature of the water leaving the top of the tank (load temperature), which increases with an increase in solar radiation, as a control signal for lowering setpoint for auxiliary heater placed inside the storage tank. Results show that the use of prediction horizon 24–72 h increase solar fraction and reduce necessary auxiliary energy of the system. Monthly analysis shows that a longer prediction horizon performs better in most cases.

Energy Procedia, 2015

Mathematical model has been developed to assess the effects of using phase change materials (PCM)... more Mathematical model has been developed to assess the effects of using phase change materials (PCM) in a fully mixed water accumulation tank. Packed bed system of spheres with a diameter of 40 mm have been considered as an option to increase energy storage density. A continuous phase model has been applied to analyse the influence of phase change during a charging and discharging processes. The methodology for calculating energy mass flow, density of water, heat transfer between layers, temperature for each time step and energy transferred to PCM is given. Single type of PCM with melting temperature of 55 °C and multiple type PCM system (65, 55, 45 and 35 °C) are compared. It is found that multiple type PCM system compared to only water and single type PCM systems, provide lower return temperatures and higher energy density.

Environmental and Climate Technologies

With the increase of renewable energy sources, the control methods of the energy systems are an i... more With the increase of renewable energy sources, the control methods of the energy systems are an increasingly important topic. Control methods have evolved from simple on/off controllers to methods that utilize artificial intelligence and can have a predictive nature. This paper investigates the control methods that are particular for solar thermal systems. A bibliometric method is applied to analyse scientific literature related to the specific application from the Web of Science database. Results show that recent developments in control methods focus on solar thermal to power and hybrid systems while district heating is a potential research gap. Annual publication trends, country, journal and keyword analysis is presented.

The use of biofuels for heating purposes is beneficial from a greenhouse gas emission point of vi... more The use of biofuels for heating purposes is beneficial from a greenhouse gas emission point of view. But combustion of solid biofuels typically is related with high emission rates of CO, NOx, PAHs, VOCs and particle matter. The most important factor that is affecting the formation of harmful emissions is the way the combustion process is organised. The amount of air injected and approach for the air supply system, are the most important factors affecting combustion process. Air staging is one of the most effective technical solutions for achieving complete combustion and low emissions. The main idea of air staging is to inject air into different zones of a combustion process. The main goal of this study is to optimise pellet combustion process in a 500 kW boiler with staged air supply. The research is based on on-site experiments and application of scientific instrumentation. Fly- away unburned fuel particles were discovered during the on-site experiments. Reduction of the amount of...

The research on solar heating systems often is faced with choice of carrying out experiments in r... more The research on solar heating systems often is faced with choice of carrying out experiments in real systems with changing parameters or to use modelling software with constant parameters but many undefined parameters or assumptions. The design of experimental system for simulating solar heat accumulation is proposed in this paper. The proposed design allows testing of phase change materials which provide higher thermal density compared to water. Results from computational fluid dynamic simulations carried out by other studies have been analysed for implementation into designing of the tank. All of these factors have been taken into account to create a system that resembles real case and can simulate for a long periods of time.

Energy Procedia, Sep 1, 2017

Abstract Biomass takes an important place in the Latvian primary energy source balance. In the co... more Abstract Biomass takes an important place in the Latvian primary energy source balance. In the coming years steeper increase of the use of biomass for the production of heat can be predicted, in order to ensure the proportion of energy produced from renewable energy resources to 40 % in 2020. However, the use of biomass has increased the risk of environmental pollution, mainly with solid particles. In order to prevent an increase in quantity of particulate matter in the atmosphere, flue gas treatment is important, with special attention to small capacity boiler equipment. The research provides insight into innovative technologies for the flue gas treatment – fog unit. Technology comparison with another widely used flue gas purification methods are given in the article.

High Temperatures. High Pressures, 1994

ABSTRACT The values of the coefficients of thermal expansion and compressibility, isobaric heat c... more ABSTRACT The values of the coefficients of thermal expansion and compressibility, isobaric heat capacity and thermal diffusivity of three brominated saturated hydrocarbons of butyl bromide, hexyl bromide and heptyl bromide are measured in a heat-conducting calorimeter at a temperature of 298–363 K in the pressure range of 0.098–147 MPa. The experimental data on the isobaric heat capacity are compared to the calculation results. Generalized dependences are suggested to determine the heat capacity and thermal diffusivity.

Environmental and Climate Technologies

This work is a continuation of the article “Methods for Determining the Performance and Efficienc... more This work is a continuation of the article “Methods for Determining the Performance and Efficiency Parameters of the Flue-gas Condenser Sedimentation Tank”. During the experimental determination of Particulate Matter (PM) physical parameters, a described methodology was used. The results obtained affected the choice of water purification technology. Sedimentation technology was selected but provided that a filter element should be present in the installation. The article describes the types of industrial sedimentation tanks used more often. In condition that the system should be compact, while at the same time the purification efficiency rate should be high, the new suitable design of the water treatment system was developed.

Environmental and Climate Technologies

One of the main pollution types is air pollution, which has a significant impact on the surroundi... more One of the main pollution types is air pollution, which has a significant impact on the surrounding environment and on living beings. Major source of air pollution is combustion processes. There are many flue gas treatment technologies around the world. In this paper a new, innovative flue gas treatment technology – fog unit – is introduced. The goal of the fog unit is to treat flue gases that are emitted from households. In the European Union, including Latvia, at the beginning of 2020, a directive will come into effect that will set limits for emissions and the effectiveness for incinerators in households. The main focus of this study was to determine the most optimal operating mode for the fog unit by changing different operating parameters: sprayed water temperature, sprayed water flowrate and types of nozzles (drop diameters). Results show that the most optimal operating mode in terms of flue gas treatment efficiency and recovered energy is at water temperature: 20 °C, sprayed ...

Environmental and Climate Technologies

Increase in solar fraction has been noted as one of the main goals for wider application of domes... more Increase in solar fraction has been noted as one of the main goals for wider application of domestic solar thermal systems. To increase solar fraction, higher energy density thermal storage availability is a key point. In this paper phase change materials have been analysed as part of a domestic solar thermal system. Sensitivity analysis of annual simulation in TRNSYS with climate data of Riga, Latvia is used. The paper also explores better methods for evaluating phase change material (PCM) performance based on temperature measurements in PCM. The results showed that the melting point of PCM and temperature set point of an auxiliary heater have the highest sensitivity of aspects analysed in the paper. It also reports that the coefficient of variation of energy in PCM correlates well with solar fraction and can be used as a parameter to evaluate PCM’s suitability for certain applications.

Sensitivity Analysis of Packed Bed Phase Change Material Thermal Storage for Domestic Solar Thermal System, 2020

Increase in solar fraction has been noted as one of the main goals for wider application of domes... more Increase in solar fraction has been noted as one of the main goals for wider application of domestic solar thermal systems. To increase solar fraction, higher energy density thermal storage availability is a key point. In this paper phase change materials have been analysed as part of a domestic solar thermal system. Sensitivity analysis of annual simulation in TRNSYS with climate data of Riga, Latvia is used. The paper also explores better methods for evaluating phase change material (PCM) performance based on temperature measurements in PCM. The results showed that the melting point of PCM and temperature set point of an auxiliary heater have the highest sensitivity of aspects analysed in the paper. It also reports that the coefficient of variation of energy in PCM correlates well with solar fraction and can be used as a parameter to evaluate PCM's suitability for certain applications.