The Scientific Journal of Riga Technical University
Not a member yet
2177 research outputs found
Sort by
Supplementing the Build Activity in Design Science Research with Soft Systems Methodology: A Technique of Creating Frameworks for Guiding Interventions Against Unstructured Problems
No full textSeveral efforts have been undertaken to define generic guidelines that address specific gaps in the ‘build’ activity of Design Science Research (DSR) artifacts, i.e., constructs, models, methods and frameworks, and instantiations. Unfortunately, explicit guidance is still lacking on how to coherently operationalize such guidelines when building a DSR artifact, particularly a framework. In addition, there is no an elaborate procedure or logical thinking pattern that can be followed when building a DSR artifact, particularly a framework for solving an unstructured problem. Consequently, structural compositions of some artifacts insufficiently subscribe to several general design guidelines, which often hinders the artifacts from fulfilling their intended purposes. To address this gap, Soft Systems Methodology can be leveraged during the design cycle of a DSR initiative, to elaborate the ‘build’ activity and simultaneously support the coherent operationalization of existing general design guidelines. This is demonstrated herein by presenting a Technique of Building Frameworks for guiding Interventions against unstructured problems (TBUFI). From 2011 to 2023, TBUFI has undergone 11 evaluation iterations, which involved: (a) using it to support the building of frameworks for guiding digital interventions in ten research studies; and (b) engaging information systems specialists in a group walkthrough meeting to deliberate its structural composition. Evaluation iterations since 2011 (including feedback from information systems specialists) confirm TBUFI’s ability to successfully guide the design of frameworks that can direct interventions against complex and unstructured problems, by making their ‘build’ activity more elaborate, coherent, and aligned with existing general design guidelines. Thus, TBUFI can be perceived as a supplement for the ‘build’ activity in DSR
A New RMF Stirrer Using AISI4140 Mild Steel: Energy Optimization Application
No full textThis study examines the development of a novel FPGA-based RMF stirrer system. The system has been designed as a 3-phase system, with each phase being fed by PWM voltage with a phase difference of 120°. In case the system is driven at a 100 % duty cycle, the force acting on the magnetic fish remains continuous and constant until the subsequent phase changes. In such a case, at speeds under 400 rpm, the speed of the magnetic fish fails to be synchronized with the phase change speed. The magnetic fish, therefore, rotates more than 120° and the force is observed to cause a braking effect. Both fluid logic control (FLC) and virtual model control (VMC) were utilised to enable the system to be driven at a different duty cycle. The energy efficiency of the system for fluids with different viscosities has been attempted to be thereby improved with a lower current and shorter excitation time. With FLC and VMC control, the energy consumed by the system is reduced and the efficiency is increased, and approximately 95 % energy gain is obtained for liquids with viscosity up to 1.03 Pa·s. It has been experimentally proven that a lower limit value of the duty cycle of the PWM signal applied to the drive circuit of the system depends on the viscosity of the mixed liquid and a lower limit value increases with increasing viscosity. It has also been found that controlling the system with FLC and VMC does not have a great effect on the energy gain
Understanding Municipal Green Initiatives and Citizen Habits in Four Baltic Sea Region Countries: Survey Results
No full textThe need to reach climate neutrality is addressed in this study by highlighting activities including boosting renewable energy sources, improving energy efficiency, and putting laws and incentives in place for the adoption of low-emission technology. Importantly, it is recognized that there is another important key factor in determining the success of sustainability projects which is an individual's willingness to change their behavior and accept new guidelines. This cross-cultural research examines the everyday routines of people from Sweden, Estonia, Latvia, and Poland and how these residents evaluate their municipalities. The research investigates the connections between citizens' behaviors in waste management, energy conservation, and transportation by considering the inhabitants' age, location of residence, and personal views. This study aims to collect the necessary data for creating focused, culturally appropriate sustainability projects. The study promotes international cooperation on environmental issues, supports sustainable practices adapted to various cultural settings, and gives policymakers useful information. Using a survey, this study takes a thorough approach to comprehending and resolving sustainability issues. The findings demonstrate that interventions need to be tailored to specific characteristics and cultural contexts to effectively encourage durable behaviors. All things considered, this study adds to the current conversation on sustainability by providing information and suggestions for encouraging environmentally friendly behavior in a variety of cultural contexts
Geospatial Analysis of Energy Poverty and Accessibility to District Heating Systems
No full textThis research paper undertakes a comprehensive geospatial analysis to investigate the relationship between energy poverty and district heating accessibility in Estonia. Utilizing ArcGIS Pro and statistical software, the study maps district heating systems, evaluates the energy efficiency of apartment buildings, and examines socioeconomic factors influencing energy poverty. By integrating GIS data with socioeconomic and building energy performance indicators, the research identifies areas where district heating is either absent or inefficient and correlates these findings with instances of energy poverty. Preliminary data may indicate a significant correlation between the lack of accessible district heating and increased energy expenses among lower-income households. The study also evaluates the impact of building energy efficiency on heating needs, revealing that older, less efficient buildings contribute disproportionately to energy poverty. Recommendations include policy interventions to expand and optimize district heating networks, alongside building renovation programs to enhance energy efficiency. This research contributes to the broader understanding of sustainable urban heating solutions and their role in mitigating energy poverty
Validating ANSYS Heat Transfer Models Using Experimental Data Analysis of Two Phase Change Materials with Differing Melting Temperatures
No full textPhase change materials are becoming more and more popular as viable options for improving the thermal performance and energy efficiency of a variety of applications, especially in innovative building envelope designs. In this paper, experimental data from two different phase change materials with differing melting temperatures (21°C and 28°C) are used to validate numerical system heat transfer models. The experimental setup included a heat flux apparatus, which was utilized to ascertain average temperature and heat flow changes over time during both heating and cooling phases for both phase change materials. The data obtained from the experiments were utilized to generate ANSYS Fluent simulation models replicating the experimental setup. The parameters and boundary conditions for the models can be assigned in several ways within ANSYS Fluent software. Consequently, two simulation models were created: one integrated the thermal and physical properties of the experimental setup's system components, while the other utilized the measured heat-flux values over time from the experiments as an input source for calculating average temperatures within the phase change material. The average temperature data from both simulation and experimental results were compared to validate both ANSYS models. By aligning the simulated results with the experimental data, the accuracy and reliability of the numerical models have been established in predicting the thermal behaviour of the two phase change materials. The two numerical system heat transfer models developed in this study serve as valuable tools for conducting further analysis and optimization of systems based on phase change materials. This research highlights the significance of phase change materials in enhancing the thermal performance of building envelopes, particularly in solar energy applications
Climate Conscious Communities: Navigating Transformation through Simulation Games and Creative Engagement
No full textIn the context of the European Green Deal and rapid climate change, significant changes in people's habits are necessary, transforming their behavior from resource consumers to climate-responsible individuals. Addressing challenges such as biodiversity loss, engagement in the development of a circular economy, responsible energy consumption, and resource sharing requires changes in individuals' attitudes and behaviors. However, individuals often lack understanding of the climate system, its link to quality of life, and the impact of actions based on individual interests on societal transformation processes as a whole. Governments and international organizations implement various complex measures, but the dynamics of climate change far exceed society's ability to adapt.To address these challenges, the authors of this paper propose using simulation games as an effective learning method. These games provide individuals with an opportunity to gain a new, community-oriented decision-making experience without creating negative effects on real systems due to inappropriate decisions. Simulation games help to better understand cause-and-effect relationships, factors influencing individual attitudes and behaviors, evaluate the consequences of decisions made, and motivate practical involvement in mitigating climate change. In order to improve the attractiveness of using the simulation game, cultural and creative industry competences are integrated, which contribute to the improvement of content, visualization and interaction.The paper examines an organizational model for simulation games that assists municipalities and other stakeholders in developing customized simulation games to promote the development of climate-responsible communities. Considering the necessity to engage diverse social groups with varying levels of digital skills, an analog format has been chosen for the simulation game, without excluding the possibility of transforming it into a digital one.The proposed model includes setting objectives, integrating elements into a holistic simulation game, and piloting the framework using examples from municipal practice. To optimize the applicability of simulation games, they need to be adapted to the geographic area and community due to individual processes and structures
Efficient Low-Temperature Nutrient Removal from Agricultural Digestate Using Microalgae
No full textHumanity is facing an energy crisis triggered by the depletion of fossil fuels, rapid industrialization, and the growthof the global population. These trendsput an emphasis on searching for alternative energy sources. Additionally, the rising concentration of carbon dioxide in the atmosphere is driving climate change, which poses serious threats. In this scenario, microalgae emerge as a promising solution for both sustainable energy production and CO2 sequestration. Digestate, a nutrient-rich by-product of anaerobic digestion, is considered a cost-effective nutrient source for microalgae cultivation. Utilizing digestate not only enhances the sustainability and economic feasibility of microalgal biofuels but also offers a method for wastewater treatment. Nevertheless, the application of digestate is limited by its high optical density and substantialamount of total solids.In this study, several pretreatment methods were tested to increase the feasibility of digestate application for microalgae cultivation. Our findings show that various centrifugation methods and vacuum filtration decrease the content of total solids but are not effective in reducing optical density. Although the use of microalgae in treating various wastewaters has shown promising outcomes, the effectiveness of nutrient removal at low temperatures remainslargely unexplored.To fill this gap, green microalga Chlorella sorokiniana was cultivated in pretreated diluted liquid digestate in dynamic springtime weather conditions in a covered open race-way pond integrated into a biogas plant.During the cultivation, high solar irradiance and low temperatures were recorded resulting in suboptimal conditions for C. sorokinianagrowth. Although low productivity of C. sorokiniana was detected, the nutrient removal efficiency was high. C. sorokiniana could efficiently remove 83% of nitrogen and 85% of phosphorus showing very promising results of the use of microalgae for wastewater treatment in high latitude regions.
Suitable Software for the Study of Combustion Processes in Boilers
No full textDiversification of energy resources is a current objective that several countries want to achieve, including in northern Europe. Demand for wood fuels is increasing in Latvia, reflected in consumer expenditure. Using low-quality biomass (LQB) to produce fuel pellets for stabilisation and diversification is possible. LQB pellets can theoretically and practically be used in low-capacity solid fuel boilers to provide different types of individual heating systems with an alternative energy source. Before starting mass production of LQB fuel pellets, it is necessary to clarify the properties of the raw materials. Any fuel study shall be divided into two phases: determination of the parameters of the fuel or raw material (calorific values, moisture content, and ash content) and analysis of the combustion process. The combustion process can be studied in two ways: experimentally and by mathematical modelling. Knowing the parameters that would need to be clarified during the study of the LQB fuel pellets combustion process (thermodynamics, gaseous emissions, PM emissions, bottom ash, and slag), the authors have set the goal of clarifying the software applied to mathematical modelling of these parameters. A bibliometric analysis method was chosen to identify the software. The bibliometric analysis was carried out in the Scopus database. As a result, two software were identified: ANSYS Fluent software is suitable for modelling thermodynamic processes and gaseous emission streams. At the same time, XDEM software is ideal for modelling particle streams and ash/slag generation. This software will be used in future studies
Carbon Footprint of a Nearly Zero Energy Building in Accra (Ghana): an LCA-based Model
No full textThis study presents a comprehensive Life Cycle Assessment (LCA) of a Nearly Zero Energy Building (NZEB) in Accra, Ghana, comparing its environmental impact with a conventional Business-As-Usual (BAU) building over a 50-year lifespan. Adhering to ISO 14040 and ISO 14044 standards, the research evaluates the carbon footprint and operational efficiencies essential to sustainable building designs. Utilizing SimaPro 9.5 software and the IPCC 2021 GWP100 method, the total carbon footprint was quantified at 1727 tons of CO2-equivalent for the NZEB, significantly lower than the BAU comparison. The analysis highlights the operational phase, including waste generation as the most substantial contributor to the NZEB's environmental impact, accounting for 725 tons of CO2-equivalent emissions. Conversely, the strategic inclusion of solar panels and enhanced material selection for the NZEB markedly reduced energy demands, contributing to a net positive environmental outcome with an avoided carbon footprint of approximately -859.72 tons CO2-eq. This reduction underpins the NZEB's effectiveness in leveraging eco-friendly materials and renewable technologies, setting a benchmark for future sustainable construction practices. The study ultimately advocates for an integrated approach, harmonizing technological innovation with environmental stewardship, to mitigate the carbon footprint of the built environment, steering the construction industry towards sustainability
Vertical Haloponics: Sustainable and Resilient Productions Using Brackish Water
No full textWhile the rapidly growing global population will require a significant increase in food production in the next years, the current climate, sanitary and geopolitical crises highlight the weaknesses of the actual food production systems, excessively dependent on external inputs and involving extremely complex nested scales and non-linear processes. Thus, appears clearly the need of accelerating the transition toward agricultural solutions and food systems based on the principles of the “Green Deal”, encompassing ecological resilience, environmental sustainability, local production, and universal access to healthy foods. Aquaponics (AP) can provide short and eco-friendly food supply chains with increased resource-use efficiency, high environmental sustainability, and food resilience. The sustainability of AP systems could be further increased by exploiting water resources that are not suitable for other purposes (brackish and salt water - haloponics), applying the vertical farming technology for both aquatic and vegetable species, reducing the use of fish meal in aquafeeds, valorizing the system residues (sludge) for agronomic purposes.The VERTICHALPONICS project aims to develop an innovative food production system by implementing an interdisciplinary approach. Since aquaponics combines recirculation aquaculture and hydroponics, within a close loop, it is considered environment friendly. However, given the different technical approaches, it is necessary to evaluate the differences in impacts and specially to assess whether the vertical system is really resource-efficient and economically viable for farmers, in comparison to the business-as-usual. The environmental and economic sustainability of the system is measured by the mean of a combined LCA and the LCC analysis (EN ISO 14040-44 and ISO 15686-5:2017 standards). The system expansion will be used to evaluate the beneficial effect of reducing the overall environmental burden from by-product recovery and utilization of side wastes, specifically the sludge produced. The method applied are Recipe and IPCC 2013 Global Warming Potential 100a. Environmental impact indicators will be provided using both mid-point and end-point categories thank to the Recipe Method, while the IPCC 2013 Global Warming Potential 100a will be applied to calculate the direct global warming potential of the system. Moreover, the inclusion of the agronomic valorization of the sludge will be analyzed to understand the potential in terms of avoided impacts.