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A significant problem of biofuel combustion is the emerging emissions of particulate matter. This paper deals with the experimental determination of the particulate matter emission characteristics of 27 different types of conventional and less traditional solid biofuels. Thermogravimetric analysis is used for the controlled heating of all tested samples from 25 °C to 650 °C with a 10 °C·min−1 heating rate. The analysis is performed for two atmosphere compositions, namely 21 % O2 and 0 % O2. The resulting flue gas is fed to an instrument allowing fine particles' detection ranging from 18 to 545 nm in diameter. The relation between the temperature of fuel samples and the number and mass of the generated particles is investigated. The percentage of the original sample mass converted to particles is determined. Subsequently, particulate matter emission is expressed as a relation to sample ash content and sample volatile matter content. The specific particulate matter emissions range of all tested samples are expressed per megajoule of higher heating value (HHV): 1.02–2.67·1015 #·MJ−1 and 694–2844 mg MJ−1 in the atmosphere with 21 % of O2 and 1.11–3.29·1015 #·MJ−1 and 898–6823 mg MJ−1 in the atmosphere without oxygen (pyrolysis).
Tomáš Sitek; Jiří Pospíšil; Ján Poláčik; Radomír Chýlek. Thermogravimetric analysis of solid biomass fuels and corresponding emission of fine particles. Energy 2021, 237, 121609 .
AMA StyleTomáš Sitek, Jiří Pospíšil, Ján Poláčik, Radomír Chýlek. Thermogravimetric analysis of solid biomass fuels and corresponding emission of fine particles. Energy. 2021; 237 ():121609.
Chicago/Turabian StyleTomáš Sitek; Jiří Pospíšil; Ján Poláčik; Radomír Chýlek. 2021. "Thermogravimetric analysis of solid biomass fuels and corresponding emission of fine particles." Energy 237, no. : 121609.
Modern control strategies for district-level heating and cooling supply systems pose a difficult challenge. In order to integrate a wide range of hot and cold sources, these new systems will rely heavily on accumulation and much lower operating temperatures. This means that predictive models advising the control strategy must take into account long-lasting thermal effects but must not be computationally too expensive, because the control would not be possible in practice. This paper presents a simple but powerful systematic approach to reducing the complexity of individual components of such models. It makes it possible to combine human engineering intuition with machine learning and arrive at comprehensive and accurate models. As an example, a simple steady-state heat loss of buried pipes is extended with dynamics observed in a much more complex model. The results show that the process converges quickly toward reasonable solutions. The new auto-generated model performs 5 × 104 times faster than its complex equivalent while preserving essentially the same accuracy. This approach has great potential to enhance the development of fast predictive models not just for district heating. Only open-source software was used, while OpenModelica, Python, and FEniCS were predominantly used.
Libor Kudela; Radomír Chýlek; Jiří Pospíšil. Efficient Integration of Machine Learning into District Heating Predictive Models. Energies 2020, 13, 6381 .
AMA StyleLibor Kudela, Radomír Chýlek, Jiří Pospíšil. Efficient Integration of Machine Learning into District Heating Predictive Models. Energies. 2020; 13 (23):6381.
Chicago/Turabian StyleLibor Kudela; Radomír Chýlek; Jiří Pospíšil. 2020. "Efficient Integration of Machine Learning into District Heating Predictive Models." Energies 13, no. 23: 6381.
The emission of fine particles (FP) generated by biomass combustion poses a substantial health risk. The immediate emissions from biomass boilers are mainly influenced by the operating parameters. The authors of this article present the results of an experimental identification of the real FP emissions from small biomass boilers and residential stoves in Central Europe. A single method was used in the study to measure the FP emissions from an automatic boiler burning spruce pellets and from a manual stove burning beech logs. The measurement is extended by a thermo-gravimetric analysis of samples of the fuels used, supplemented with an analysis of the emitted particles. The boilers were tested in an operating cycle that included the phases of fuel ignition, steady combustion, and afterburning. The paper presents the concentrations and size distributions observed of the emitted FP ranging from 17 to 544 nm in size. Operating cycles including a “cold start” and “warm start” are compared. The results achieved are summarized by the expression of the nominal FP emission presenting the number and mass emission corresponding to burning 1 kg of fuel. The tested automatic boiler fed by spruce pellets produced a nominal FP emission of 173 mg kg−1 in the size range of 17–544 nm during the testing operation cycle. The tested manual stove, fed by beech logs, produced a nominal emission of 1043 mg kg−1 in the same size range of particles during the similar testing cycle.
Ján Poláčik; Tomáš Sitek; Jiří Pospíšil; Ladislav Šnajdárek; Martin Lisý. Emission of fine particles from residential combustion of wood: Comparison of automatic boiler, manual log feed stove and thermo-gravimetric analysis. Journal of Cleaner Production 2020, 279, 123664 .
AMA StyleJán Poláčik, Tomáš Sitek, Jiří Pospíšil, Ladislav Šnajdárek, Martin Lisý. Emission of fine particles from residential combustion of wood: Comparison of automatic boiler, manual log feed stove and thermo-gravimetric analysis. Journal of Cleaner Production. 2020; 279 ():123664.
Chicago/Turabian StyleJán Poláčik; Tomáš Sitek; Jiří Pospíšil; Ladislav Šnajdárek; Martin Lisý. 2020. "Emission of fine particles from residential combustion of wood: Comparison of automatic boiler, manual log feed stove and thermo-gravimetric analysis." Journal of Cleaner Production 279, no. : 123664.
The dispersion of particulate matter emitted by road transport to the vicinity of roads is predominantly influenced by the character of the air velocity field. The air flow depends on factors such as the speed and direction of the blowing wind, the movement of cars, and the geometries of the buildings around a road. Numerical modeling based on the control volume method was used in this study to describe the relevant processes closely. Detailed air velocity fields were identified in the vicinity of a straight road surrounded by various patterns of built-up urban land. The evaluation of the results was generalized to exponential expressions, affecting the decrease of the mass concentration of fine particles with the increasing distance from the road. The obtained characteristics of the mass concentration fields express the impact of the building geometries and configurations on the dispersion of particulate matter into the environment. These characteristics are presented for two wind speeds, namely, 2 m·s−1 and 4 m·s−1. Furthermore, the characteristics are introduced in relation to three wind directions: perpendicularly, obliquely, and in parallel to the road. The results of the numerical simulations are compared with those obtained via the in-situ measurements, for verification of the validity of the linear emission source calculation.
Jiri Pospisil; Jiri Huzlik; Roman Licbinsky; Michal Spilacek. Dispersion Characteristics of PM10 Particles Identified by Numerical Simulation in the Vicinity of Roads Passing through Various Types of Urban Areas. Atmosphere 2020, 11, 454 .
AMA StyleJiri Pospisil, Jiri Huzlik, Roman Licbinsky, Michal Spilacek. Dispersion Characteristics of PM10 Particles Identified by Numerical Simulation in the Vicinity of Roads Passing through Various Types of Urban Areas. Atmosphere. 2020; 11 (5):454.
Chicago/Turabian StyleJiri Pospisil; Jiri Huzlik; Roman Licbinsky; Michal Spilacek. 2020. "Dispersion Characteristics of PM10 Particles Identified by Numerical Simulation in the Vicinity of Roads Passing through Various Types of Urban Areas." Atmosphere 11, no. 5: 454.
Lubomír Klimeš; Jiří Pospíšil; Josef Štětina; Petr Kracík. Semi-empirical balance-based computational model of air-cooled condensers with the A-frame layout. Energy 2019, 182, 1013 -1027.
AMA StyleLubomír Klimeš, Jiří Pospíšil, Josef Štětina, Petr Kracík. Semi-empirical balance-based computational model of air-cooled condensers with the A-frame layout. Energy. 2019; 182 ():1013-1027.
Chicago/Turabian StyleLubomír Klimeš; Jiří Pospíšil; Josef Štětina; Petr Kracík. 2019. "Semi-empirical balance-based computational model of air-cooled condensers with the A-frame layout." Energy 182, no. : 1013-1027.
The paper presents a parametric study evaluating the effects of various predictive controls on the operating parameters of heat pumps. The heat pump represents a significant power appliance in the residential sector. Its connection to the heat accumulator creates a system with considerable potential to control electricity consumption according to the needs of the electricity grid. The air-water heat pump is considered in this study. A predictive control is used for priority operation of the heat pump at periods of peak power production from renewable sources. The following were tested as the parameters of predictive control: outdoor air temperature, photovoltaic power production and wind power production. The combination of photovoltaic and wind power production was also tested. A parametric analysis considering different sizes for the thermal accumulator and the heating capacity of the heat pump were proposed. The benefits of predictive control are evaluated based on historical records of meteorological data from 2015 to 2018 in the city of Brno, Czech Republic. The data on the historical development of the real electrical energy production from renewable sources in the Czech Republic are used for regulation control in a monitored period. The main comparison parameter is the heat pump seasonal coefficient of performance (SCOP). From the carried out study results, an increase in SCOP by 14% was identified for priority operation of heat pump (HP) at periods with highest outdoor air temperature. Priority operation of HP at periods with peak photovoltaic (PV) production increased SCOP by 10.25%. A decrease in SCOP only occurred in case with priority operation of HP at peak production of wind power plants. Increasing the size of the accumulator contributes to an increase in SCOP in all assessed modifications of predictive control.
Jiří Pospíšil; Michal Špiláček; Pavel Charvát. Seasonal COP of an Air-to-Water Heat Pump when Using Predictive Control Preferring Power Production from Renewable Sources in the Czech Republic. Energies 2019, 12, 3236 .
AMA StyleJiří Pospíšil, Michal Špiláček, Pavel Charvát. Seasonal COP of an Air-to-Water Heat Pump when Using Predictive Control Preferring Power Production from Renewable Sources in the Czech Republic. Energies. 2019; 12 (17):3236.
Chicago/Turabian StyleJiří Pospíšil; Michal Špiláček; Pavel Charvát. 2019. "Seasonal COP of an Air-to-Water Heat Pump when Using Predictive Control Preferring Power Production from Renewable Sources in the Czech Republic." Energies 12, no. 17: 3236.
The combustion of biomass is associated with the production of a significant amount of combustion particles. These particles are entrained by the flue gas from the combustion plant. To assess the type of fuel and the influence of the operating parameters on the fine particle emission, it is useful to know the mass of the fine particles produced at combustion per unit amount of fuel. For this purpose, the authors carried out laboratory combustion tests using thermogravimetric analysis and identification of the fine particle size distribution in the flue gas. Different samples of beechwood were used for experimental measurements. The atmosphere of the combustion process was tested in the range of 0 to 21% of oxygen in a mixture with nitrogen. The measured mass ratios of the fine particles produced and the original fuel sample were compared with the experimental studies of other authors. The resulting mass emissions of fine particles were quantified between 2% and 9% of the initial fuel sample weight.
Tomáš Sitek; Jiří Pospíšil; Ján Poláčik; Michal Špiláček; Petar Varbanov. Fine combustion particles released during combustion of unit mass of beechwood. Renewable Energy 2019, 140, 390 -396.
AMA StyleTomáš Sitek, Jiří Pospíšil, Ján Poláčik, Michal Špiláček, Petar Varbanov. Fine combustion particles released during combustion of unit mass of beechwood. Renewable Energy. 2019; 140 ():390-396.
Chicago/Turabian StyleTomáš Sitek; Jiří Pospíšil; Ján Poláčik; Michal Špiláček; Petar Varbanov. 2019. "Fine combustion particles released during combustion of unit mass of beechwood." Renewable Energy 140, no. : 390-396.
This paper compares approaches for accurate numerical modeling of transients in the pipe element of district heating systems. The distribution grid itself affects the heat flow dynamics of a district heating network, which subsequently governs the heat delays and entire efficiency of the distribution. For an efficient control of the network, a control system must be able to predict how “temperature waves” move through the network. This prediction must be sufficiently accurate for real-time computations of operational parameters. Future control systems may also benefit from the accumulation capabilities of pipes. In this article, the key physical phenomena affecting the transients in pipes were identified, and an efficient numerical model of aboveground district heating pipe with heat accumulation was developed. The model used analytical methods for the evaluation of source terms. Physics of heat transfer in the pipe shells was captured by one-dimensional finite element method that is based on the steady-state solution. Simple advection scheme was used for discretization of the fluid region. Method of lines and time integration was used for marching. The complexity of simulated physical phenomena was highly flexible and allowed to trade accuracy for computational time. In comparison with the very finely discretized model, highly comparable transients were obtained even for the thick accumulation wall.
Libor Kudela; Radomir Chylek; Jiri Pospisil. Performant and Simple Numerical Modeling of District Heating Pipes with Heat Accumulation. Energies 2019, 12, 633 .
AMA StyleLibor Kudela, Radomir Chylek, Jiri Pospisil. Performant and Simple Numerical Modeling of District Heating Pipes with Heat Accumulation. Energies. 2019; 12 (4):633.
Chicago/Turabian StyleLibor Kudela; Radomir Chylek; Jiri Pospisil. 2019. "Performant and Simple Numerical Modeling of District Heating Pipes with Heat Accumulation." Energies 12, no. 4: 633.
This article extends earlier research by the authors that was devoted to the experimental evaluation of ultra-fine particles produced by the laboratory combustion of beechwood samples. These particles can have severe influence on human health. The current paper presents a parametrical study carried out to assess the influence of the composition of the atmosphere and the temperature on the production of ultra-fine particles during the micro-scale combustion process. The paper presents a laboratory procedure that incorporate the thermogravimetric analysis (TGA) and detailed monitoring of the size distribution of the produced fine particles. The study utilises the laboratory scale identification of the formation and growth of the fine particles during the temperature increase of beech wood samples. It also compares the particle emissions produced by beech heartwood and beech bark. The size of the emitted particles is very strongly influenced by the concentration of light volatiles released from the heated wood sample. From the experimental study, decreasing oxygen content in the atmosphere generally results in higher particulate matter (PM) production.
Jan Poláčik; Ladislav Šnajdárek; Michal Špiláček; Jiří Pospíšil; Tomáš Sitek. Particulate Matter Produced by Micro-Scale Biomass Combustion in an Oxygen-Lean Atmosphere. Energies 2018, 11, 3359 .
AMA StyleJan Poláčik, Ladislav Šnajdárek, Michal Špiláček, Jiří Pospíšil, Tomáš Sitek. Particulate Matter Produced by Micro-Scale Biomass Combustion in an Oxygen-Lean Atmosphere. Energies. 2018; 11 (12):3359.
Chicago/Turabian StyleJan Poláčik; Ladislav Šnajdárek; Michal Špiláček; Jiří Pospíšil; Tomáš Sitek. 2018. "Particulate Matter Produced by Micro-Scale Biomass Combustion in an Oxygen-Lean Atmosphere." Energies 11, no. 12: 3359.
The world trade volume of Liquefied Natural Gas (LNG) is increasing year by year. Unlike gaseous natural gas (NG), which is transported through a fixed network of pipelines, LNG offers more flexibility to both the exporters and the importers as it can be transported between any pair of exporting and receiving LNG terminals. The LNG process, consisting of liquefaction, transportation, storage, and regasification of LNG, is accompanied by certain energy demands. The paper focuses on the evaluation of the chain of energy transformations involved in the LNG process. Based on the review of existing information, the entire process is evaluated from the view of the potential use of LNG for direct storage of cold and indirect storage of power. The analysis of the existing data shows that the overall efficiency of using LNG for operative energy storage depends very much on the technologies involved and on the overall capacity of the particular technology. The combination of energy-efficient liquefaction technologies and regasification technologies with energy recovery makes it possible to employ LNG as an energy storage medium even when transported over large distances.
Jiří Pospíšil; Pavel Charvát; Olga Arsenyeva; Lubomir Klimes; Michal Špiláček; Jiří Jaromír Klemeš. Energy demand of liquefaction and regasification of natural gas and the potential of LNG for operative thermal energy storage. Renewable and Sustainable Energy Reviews 2018, 99, 1 -15.
AMA StyleJiří Pospíšil, Pavel Charvát, Olga Arsenyeva, Lubomir Klimes, Michal Špiláček, Jiří Jaromír Klemeš. Energy demand of liquefaction and regasification of natural gas and the potential of LNG for operative thermal energy storage. Renewable and Sustainable Energy Reviews. 2018; 99 ():1-15.
Chicago/Turabian StyleJiří Pospíšil; Pavel Charvát; Olga Arsenyeva; Lubomir Klimes; Michal Špiláček; Jiří Jaromír Klemeš. 2018. "Energy demand of liquefaction and regasification of natural gas and the potential of LNG for operative thermal energy storage." Renewable and Sustainable Energy Reviews 99, no. : 1-15.
This work aimed to determine filtration performance of polypropylene hollow-fiber membranes in removing submicron particles from air. Experiments were performed in a chamber simulating dust environment with synthetic submicron-size particles (micronized TiO2). Ahollow-fiber membrane with 300 fibers of a filtration area of 0.43 m2 was tested. By measuring number of particles in chamber (upstream) and on the suction side of the membrane (downstream), the filtration efficiency was determined. Two different weights of synthetic dust (50 and 100 mg) and two permeate velocities (15 and 30 cm/s) were used to compare their influence on particle collection efficiency. Particle counting was carried out using a TSI 3075 condensation particle counter connected to a TSI 3080 scanning mobility particle sizer in 32 particle size channels from 17 to 600 nm. Pressure drop evolution with intense particle loading was recorded and fouling of the membrane was observed after 25, 50 and 90 h of filtration using SEM. The results showed high efficiency, mostly higher than 99.9% with higher pressure drops compared to other materials on HEPA level.
Pavel Bulejko; Tomáš Svěrák; Mirko Dohnal; Jiří Pospíšil. Aerosol filtration using hollow-fiber membranes: Effect of permeate velocity and dust amount on separation of submicron TiO2 particles. Powder Technology 2018, 340, 344 -353.
AMA StylePavel Bulejko, Tomáš Svěrák, Mirko Dohnal, Jiří Pospíšil. Aerosol filtration using hollow-fiber membranes: Effect of permeate velocity and dust amount on separation of submicron TiO2 particles. Powder Technology. 2018; 340 ():344-353.
Chicago/Turabian StylePavel Bulejko; Tomáš Svěrák; Mirko Dohnal; Jiří Pospíšil. 2018. "Aerosol filtration using hollow-fiber membranes: Effect of permeate velocity and dust amount on separation of submicron TiO2 particles." Powder Technology 340, no. : 344-353.
This paper deals with a use of CFD modelling for optimization of supply of secondary combustion air in the two-chamber biomass boiler combusting very wet biomass (capacity ca. 200 kW). Objective of the analyse is to observe the impact of diameter of a secondary air supply pipe and air flow velocity on mixing of the secondary air with flue gas in the combustion chamber. The numerical model of the experimental boiler was build up for subsequent utilizing of CFD computation based on finite element method. The commercial code STAR-CD was used for carried out parametrical studies. Series of calculations were carried out for four different diameters of air distribution pipes and for 3 different air velocities in distribution orifice. Quality of air dispersion in flue gas flow was assessed in the vertical cross section lead in the end of the combustion chamber. The results of calculation were verified on the experimental installation of the boiler. Influence of secondary air mixing on emission production was measured and analysed. Emissions of pollutants for recommended air distribution comply with emission limits stipulated in the most stringent class 5 according to ČSN-EN 303-5 as well as with emission limits under Regulation No. 405/2012 Sb.
Martin Lisý; Jiří Pospíšil; Otakar Štelcl; Michal Špilaček. Optimization of Secondary Air Distribution in Biomass Boiler by CFD Analysis. Applied Mechanics and Materials 2016, 832, 231 -237.
AMA StyleMartin Lisý, Jiří Pospíšil, Otakar Štelcl, Michal Špilaček. Optimization of Secondary Air Distribution in Biomass Boiler by CFD Analysis. Applied Mechanics and Materials. 2016; 832 ():231-237.
Chicago/Turabian StyleMartin Lisý; Jiří Pospíšil; Otakar Štelcl; Michal Špilaček. 2016. "Optimization of Secondary Air Distribution in Biomass Boiler by CFD Analysis." Applied Mechanics and Materials 832, no. : 231-237.
J. Pospisil; M. Jicha. Behavior of Particulate Matter Produced by Cars in a Regional Model of Urban Canopy Layer. Transactions on Transport Sciences 2008, 1, 157 -164.
AMA StyleJ. Pospisil, M. Jicha. Behavior of Particulate Matter Produced by Cars in a Regional Model of Urban Canopy Layer. Transactions on Transport Sciences. 2008; 1 (4):157-164.
Chicago/Turabian StyleJ. Pospisil; M. Jicha. 2008. "Behavior of Particulate Matter Produced by Cars in a Regional Model of Urban Canopy Layer." Transactions on Transport Sciences 1, no. 4: 157-164.