The Scientific Journal of Riga Technical University
Not a member yet
2177 research outputs found
Sort by
A Preliminary Evaluation of Alternative Raw Materials for Pellet Production
No full textThe study focuses on alternative raw materials available in Latvia and their possible use in pellet production. Laboratory testing to determine the main quality parameters – the moisture content, the ash content, the calorific value and ash melting temperature – was carried out for 13 alternative biomass sources: pine mix pellets (PMP); pellets of wood shavings, synthetic and textile waste mix (SSK); hogweed (Heracleum sosnowsky, HW); the full plant of Solidago canadensis L. (SC); the full plant of Solidago canadensis L. outgrown (SCO); mowed grass from the municipality (MGM); mowed grass from the garden (MGG); chamomile full plant without stems (CF); hemp without roots (Cannabis sativa L., HWR); hemp stems (Cannabis sativa L., HS); hemp leaves with seeds (Cannabis sativa L., HLS); spent grain (SG); damaged spent grain (DSG). The testing and determination of results were carried out according to the methodology set out in ISO standards regarding solid biofuels. The obtained results were compared to the quality parameters defined in ENplus certification for B-class wood pellets in requirements for producers. Additional analysis of chemical composition was carried out using XRD (X-ray diffraction) and SEM-EDX (scanning electron microscopy - energy dispersive X-ray spectroscopy) for the ash of two selected materials - SC and HLS - to gain an insight into possible combustion issues that can occur during the use of these materials. The main issue highlighted by the results is the ash content of alternative materials, which ranges from 1.34% to 11.27%. The other significant issue is the necessity to improve the ash deformation temperature, which was below 1100°C for 5 of the studied materials. Considering this, an algorithm was developed to determine the optimal proportion of alternative material and wood in pellets to achieve a quality comparable to at least B-class wood pellets. The study offers a direction for further research to successfully develop new pellets that could be later used in existing boiler systems, reducing the dependence on wood in pellet production. A discussion on the use, quality and development of alternative material pellets is offered to promote the significance of the topic
Electric Vehicle Charging Infrastructure Study for Apartment Buildings
No full textChanges in the engine type of cars aimed at climate goals also have an impact on the habit of electricity consumption at home. Charging electric cars from the residential grid also increases the total electricity consumption of the residential building. If all apartment owners in an apartment building want to charge their electric car at the same time, this may create a situation where the main protection of the apartment building is activated. The purpose of this research is to identify possible options to avoid this problem, based on different real-life data. For example: adding an energy storage to the electrical system of an apartment building is seen as one solution. Also supplement of an energy management software to the electrical and battery bank system to enables residents to schedule and prioritize their electric car charging times to avoid simultaneous high-demand periods. This system can also be used to optimize electricity distribution and consumption in apartment buildings under volatile electricity price conditions
Attracting Customers to District Heat Supply: The Case of Riga
No full textDistrict heating will be important in achieving future climate goals. Possibilities of using waste heat from different sources, e.g. subways, hospitals, shops, data centers, rivers are often discussed. Many district heating companies face the challenge of sufficient coverage of connected consumers in a city or region. To expand the operating area, companies should initially attract objects which are close to heat networks to lower the connection costs. The research question is how to attract existing buildings under construction to the district heating system. The present work uses system dynamics modeling for studying the possibilities of the Riga district heat supply company to increase consumer network. Modeling is based on historical data of residential buildings. The results show that old buildings choose to connect to the district heat supply when these are being renovated, or the individual heat supply equipment is out of order. The older the buildings, the more likely these will be connected to the district heating, however this decision may take at least 70 years. Renovation increases the probability of connection to the district heating, so the impact of subsidies for renovation is important. Regulation that requires connection to the district heating as a priority choice in case of renovation is also important
Analysis and Assessment of H2S Sorption Capacity of the Selected Biofiltration Materials
No full textHydrogen sulfide known as one of the highly toxic chemical compounds existed in the raw biogas and needs to be eliminated before implementation at any industrial sector. Biofilter (a typical bioreactor) is a tool used to separate sulfide/sulfate from hydrogen by biofiltration method, which is known as the green technology. Packing material is the main component inside a laboratory-scale biofilter to undertake the desulfurization process of H2S. This study is dedicated to evaluating number of selected recyclable/waste organic, inorganic, and synthetic packing material’s rate of impact on amplifying purification progress of hydrogen sulfide from biogas, known as biofilters “removal efficiency (RE)”. Variable effective factors such as environmental and equipment conditions, consumed time (day), and inlet H2S concentration will be controlled throughout the measurements for all chosen packing materials. In the end, the best performed environment-friendly biofiltration material in terms of sorption capacity of H2S from the biogas will be announced
Life Cycle Analysis of a Battery Energy Storage System
No full textFor Latvian government and transmission system operator energy security and independence has been an issue for a period of time, even more when political situation changed, motivating to act faster in order to swich off from BREL system completely. Therefore, three Baltic states have made an agreement on building more stable electricity transmission system within Baltic region and to connect with European transmission systems, building new stations with synchronous compensators and energy storage systems. In order to build a system, that allows to include more energy from renewable resources and secure possible disbalances in system, Latvian TSO operator is building a new battery energy storage system. This paper is aimed to look at what are the costs of this battery energy storage system from climate perspective to Latvia and its society in order to gain energy security and possibility to include more energy from renewable resources
Moving Waste Sector Towards Climate Neutrality. Scenario Analysis
No full textThe upward economic growth, the development of the industrial, transport and agricultural sectors, and technological innovations contribute to the constant stimulation of the demand and supply of new products and services, inevitably contributing to the increase in the amount of waste. Mitigation of climate change is not a short-term goal; therefore, sustainable and reasonable practices in the waste management sector could contribute to positive changes in mitigating GHG emissions and climate change in general. However, it is not clear whether by implementing the current domestic waste management policy of Latvia and the action measures contained in it, it is objectively possible to achieve the strategic goals and desired results set at the European Union as well as at the national level, what is the impact of the set goals and the success of their implementation so far, and whether these political settings will not remain only at the level of ideas and wishes. In the scientific literature, several proposals developed as a result of research have been put forward for reducing the climate neutrality of the waste sector with the help of various technologies and technological innovations. At the same time, it is difficult to evaluate the proposals and solutions put forward in the research results in relation to an individual situation; for example, if a municipality in Latvia would like to implement it in order to evaluate their effectiveness, benefits and applicability. Difficulties are caused by the research results presented in the scientific literature, which are not expressed as indicators that would help to apply this solution to each individual case and its characteristic values. The purpose of the study is to evaluate the political goals set by Latvia in the household waste management sector in the context of the political goals set by the European Union for achieving climate neutrality and to provide an objective assessment of the achievement of the goals set by Latvia. In order to achieve the goals, an analysis of the scenarios of the household waste management sector established by Latvia's policy will be carried out, an evaluation of the actions implemented as a result of the policy and still planned will be carried out. Also, in order to achieve the goals of the study, indicators will be developed, with the help of which the effectiveness and applicability of the implementation of various technological innovations could be assessed. The development of indicators will be based on the information reflected in the scientific literature about the results of the implementation of technological innovations in the household waste management sector. As a result of the literature analysis, the absolute values of the selection of criteria for the implementation of technological innovations will be determined, as well as key performance indicators will be determined in such categories as technological solution, economic factor, impact (mitigation) on the environment, social factor. The scientific novelty of the research is based on the creation of a value database of the criteria for the implementation of technological innovations, and the development of an evaluation matrix based on it, based on the collected indicators, which would help to assess the applicability and availability of the technological innovations introduced in the waste management sector in order to promote the goals set in the political documents for achieving climate neutrality. As a result of the research, an assessment of the compliance of the climate neutrality goals set in the political planning documents will be carried out based on the indicators included in the developed matrix, in order to achieve the best waste management solutions.
Biodegradable Waste Management in Georgia: Problems of the Composting System Introduction
No full textBiodegradable waste management and, in particular, the introduction and implementation of composting systems are among the major problems for Georgia. An increase in the volume of municipal waste has been recorded in the country; therefore, the volume of generated biodegradable waste is also increasing. In accordance with the National Waste Management Strategy 2016-2030 of Georgia, the municipal waste generated in 2021 amounted to 1,104,952 tons. It is worth noting that the largest part of municipal waste is organic waste - 54.7%, while plastic waste is 13.8%, paper and cardboard - 10.6%, textiles - 4.1%, and other wastes. According to various studies, by 2030, waste generation is expected to increase from 0.6% to 1.2% annually, which should be the cause of significant challenges for national and local authorities, especially local municipalities, whose duties include municipal waste collection and transportation as well as the implementation of separate waste collection systems. Biodegradable waste management, including various composting systems, is of particular importance.The study shows that composting, as one of the best approaches for recycling biodegradable waste, is still not properly developed in Georgia. It is possible to name only a few successful experiences. Noteworthy among them is the Kutaisi Composting Center, which was established within the framework of the EU JOP “Black Sea Basin” in Kutaisi, Georgia. The Composting Center is designed for windrow composting of green waste (tree branches, leaves, grass). Its productivity is 2000 tons of compost annually. This Composting Center is one of the first in Georgia. It can bring very tangible benefits. In particular, the amount of municipal waste going to landfill sites was reduced by approximately 10%; the expenditures of the municipalities connected to the maintenance of green facilities (received compost is used) and so on have been reduced.Among the biodegradable waste composting approaches, it is recommended to use systems such as:Centralized composting,Community composting,Home (individual) composting.A centralized composting method can be used in municipalities where a large amount of biodegradable waste is generated. It is especially favorable in regions where the agricultural sector is developed and large amounts of green waste are generated. The Kutaisi Composting Center is a good example of the centralized composting system. As experience shows, such large-scale composting is particularly effective for green waste composting.It is promising for Georgia to introduce community composting approaches that offer an optimal scheme for communities to get the maximum benefits of their potential.Composting is an approach used in the field of biodegradable waste management that has the greatest potential in Georgia and can make a significant contribution to both economic development and the protection of the social and natural environment
PH-Optimized Biomethane Production: Evaluating Carrier Materials for Ex-situ Biomethanation
No full textChoosing the appropriate carrier material for ex-situ biomethanation is a critical factor to consider when developing biogas upgrading technologies. The chosen material for biomethanation in a biotrickling filter reactor functions as a substrate that immobilises microorganisms, which act as catalysts in the reaction for producing biomethane. This study conducted experiments on waste-derived materials, including glass foam and vulcanised wood ash material, in addition to polyurethane foam and expanded clay pellets. Pretreratment of wood ash was done to lower the pH of material. The manometric test measured the rate of CH4 generation by quantifying pressure fluctuations. The validity of these results was confirmed by analysing product gas samples using a Shimadzu Nexis GC-2030 gas chromatograph, which was equipped with two parallel lines, a flame ionisation detector (FID) and a thermal conductivity detector (TCD). In order to enhance the biomethane concentration in the end product, two strains of Methanobacterium alcaliphilum were evaluated alongside biogas sludge as the inoculum. These strains of microorganisms are methanogens that utilise hydrogen and can thrive in a high pH environment. Thus, they have the potential to demonstrate improved biomethane production outcomes when a vulcanised wood ash filter is used as the carrier material
Rīgas Tehniskās universitātes un Drēzdenes Tehniskās universitātes starptautiskā partnerība trijos gadsimtos (1862–2024)
No full textRīgas Tehniskās universitātes (RTU) un Drēzdenes Tehniskās universitātes (DTU) sadarbība ir viena no senākajām starptautiskajām partnerībām abu augstskolu vēsturē. Tā sākās pirms vairāk nekā pusotra gadsimta un turpinās joprojām. Abu augstskolu sadarbība izpaudusies dažādos veidos – gan pārņemot augstskolas kā institūcijas pieredzi un daloties tajā, gan studentu un docētāju apmaiņas braucienos. Daži inženieri un docētāji ir strādājuši tehniskajā augstskolā Rīgā, savukārt Drēzdenē ir studējuši un strādājuši kādreizējie rīdzinieki. 20. gadsimta otrajā pusē tika noslēgti abu augstskolu sadarbības līgumi. Atjaunotā Rīgas Politehniskā institūta (RPI) labākie studenti studijas turpināja Drēzdenē, praktizējās vācu uzņēmumos. Pieredzes apmaiņā uz DTU devās gan studenti, gan mācībspēki. Ilggadējā sadarbība turpinās arī mūsdienās, neaizmirstot savstarpējos apsveikumus augstskolu jubilejās un nominējot zinātniekus par augstskolu Goda biedriem
Modelling the Electric Bus Charging Network Requirements for HVAC Purposes
No full textWider use of electric buses is hindered by necessity to provide cabin heating for the passengers during winter months, which in cold climates uses up as much energy as driving, thus significantly reducing bus driving range and requiring larger traction batteries, which are expensive. When the lifetime operational costs are included, unless they are heavily subsidized, the battery electric buses have troubles competing with internal combustion engine (ICE) buses in cold weather conditions. For typical ICE buses, the power capacity for heaters is in the range of 50 kW. It would be possible to increase the driving range by using heat accumulators to provide energy for vehicle thermal requirements. These heat accumulators could be recharged in bus stops using wireless charging to minimize battery size. This article describes the results of a mathematical model developed to determine optimum wireless charging power requirements for heat accumulators. The model is created for public transportation system in Riga city based on weather data in years 2017–2022 to provide passenger thermal comfort. The model simulates energy flows for bus movement and heating purposes using worst-case scenario approach. The model analysed 198 916 bus stop data, which were pertinent for weekday travels in Riga city. The analysis covered 1716 individual bus stops and 448 routes. The results showed that the charging availability during the day varied from 3 % to 55 % and on average the total energy needed for heating would be 75.6 kWh. However, in the worst-case scenario, the number rises to 237 kWh making the system too expensive for practical applications. During the research there is a very limited availability of research regarding bus heating requirements. Most of the research on thermal comfort in busses are done in hot climate and consequently mostly concerns air conditioning. The thermal comfort research about cold weather is predominantly about buildings and indoor comfort and could not directly apply, as clothing should be considered. Also, the research shows that the temperatures for comfort are lower for short haul vehicles than for the long-haul ones. All these factors strongly indicate that current conventions on temperature requirements for buses are outdated and coming from ICE buses where the heat came from the engine and was free. Therefore, the next studies should include field research analysing passenger thermal comfort levels in buses in winter to explore if there are additional opportunities for energy savings in bus HVAC systems