The Scientific Journal of Riga Technical University
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Profitability Assessment of Windfarm Overplanting in Spain
Full text linkThe efforts made by European institutions to decarbonise the electricity system over the last decade have led Spain to become the fifth country in the world in terms of wind power plant capacity in 2021. This major achievement is still far from being able to contain and limit CO2 emissions. By 2030, it is expected that, together with photovoltaic energy, Spain will reach 74 % of renewable generation in its electricity system. Wind technology is currently very mature in onshore wind farms and its relatively low cost makes this technology attractive to investors. However, the best wind sites were the first places to be occupied by the first turbine generations. On the other hand, newer wind farms occupy sites with less wind resource but have more efficient turbines. To improve the profitability of the wind farm and increase its production, the feasibility of other alternatives such as overplanting or storage is beginning to be investigated. Overplanting aims to optimise the use of the transmission system by increasing wind capacity above the transmission capacity limit. In this work, we measure the profitability of an overplanting strategy by quantifying the parameters that make profitable the investment. The developed model optimised the production of energy taking into account technical and financial parameters in order to cover a wide range of situations. We analysed the case of a specific site with 25 2 MW turbines with the Python tool PyWake. The results obtained show that for each new turbine the annual energy produced (AEP) grows by around 3.87 GWh per turbine added (a cut of 1.69 GWh due to congestion of the transmission system). The study shows improvements in profitability when the electricity price exceeds 70 €/MWh
From Incineration to Sterilisation of Solid Hospital Waste in Low-income Contexts: a Gradual Sustainable Transition.
Full text linkOpen burning and incineration are the two most common treatments for hospital solid waste in low-income countries. Due to the absence of limits on emissions and the lack of technical capacity or funding, obsolete incinerators do not guarantee neither a low environmental and economic impact nor people health. The SIRSU Project, co-financed by the Italian Agency for Sustainable Development and Newster Group, aims to substitute the incinerator in Beira Central Hospital (Mozambique) with an electric sterilizer, an environmentally friendly machine that is also safe for workers. However, it is not sufficient to import this new technology and train the staff. First, an assessment of the quantities and types of biomedical waste produced in the different hospitals is necessary, as well as a careful analysis of the waste management system of all hospitals in the city. If the technology is suitable for the context, then, after the training of technicians for maintenance and operation, a period of accompaniment and monitoring is necessary to optimise performances. The transition cannot be immediate, and a period of coexistence of the two plants (steriliser and incinerator) is necessary. To facilitate the gradual transition, the SIRSU project foresees the foundation of a local start-up to manage the steriliser and offer a waste full transport service for smaller hospitals to the Central Hospital where the machine is installed. This experience could be an opportunity to set guidelines comprehensive of the concepts of safety and security during all the steps of the transition. This aspect can be an important element for defining 1) the most appropriate technical solutions, evaluating the implementations on the control and regulation systems in order to minimize the risks associated with the process, 2) management and above all operational methods in order to guarantee not only compliance with the most precautionary technical legislations, but also modern and advanced operating standards
Challenges and Barriers for Aquaculture Sector: Review Article on Freshwater Aquaculture
Full text linkThe EU aquaculture sector, like other sectors of the EU economy, must participate in the ‘green transition’ set out in the European Green Deal. The sector has a particular role to play in contributing to the transition towards sustainable food systems and the development of the bioeconomy and circular economy. Aquatic organisms and fish cultivated in aquacultures are important sources of food and feed, the importance of developing which has been highlighted in several EU policy planning documents. Due to high nutritive value, fish and aquatic organisms are a valuable food source. Despite the rapid growth of aquaculture in Europe and other parts of the world, the promotion of sustainable or organic aquaculture is crucial for the provision of high-quality, locally accessible food. Aquacultures produce relatively low greenhouse gas emissions compared to sources of protein grown on land. However, there is still room for growth, therefore, to further reduce greenhouse gas emissions from aquacultures and foster more sustainable practices and greater resource and energy efficiency are required. This review article includes an analysis of policy planning documents adopted in Latvia and the EU, outlining opportunities and risks for creating a sustainable aquaculture industry. The purpose of this review article is to identify the most significant problems and obstacles to achieving a sustainable aquaculture system at both the local and European levels. In addition, the review investigates and contrasts recent advancements in aquaculture technological processes and socioeconomic impact factors. Whether aquaculture’s path to sustainability is jeopardized by inefficient consumption of resources and wastes (feed, energy, emissions) at the beginning or end of the organisms’ life cycle
TRNSYS Simulation of the Use of Solar Collector-based Domestic Hot Water System in Central and Eastern European Countries (CEEC)
Full text linkWith the prevailing energy crisis and the public’s growing environmental awareness, renewable energy sources (sun, wind, water) are playing an increasingly important role in Europe and around the world. Due to its easy availability and relatively high efficiency, it is the solar energy that is attributed with great potential in decarbonizing the energy sector. Among the most popular devices that enable the use of solar radiation are solar collectors. They are used in heating and domestic hot water preparation systems, as well as for heating swimming pool water. However, their efficiency depends on many factors, of which the main one being the climatic conditions. This paper presents the results of energy simulations of a solar collector-based domestic hot water system for the capitals of five selected Central and Eastern European Countries (CEEC) – Riga (Latvia), Warsaw (Poland), Prague (the Czech Republic), Bratislava (Slovakia), and Zagreb (Croatia). The system model was developed using the TRNSYS software, in which dynamic simulations were also performed for an entire year (8760 h). For each location, the efficiency of the flat-plate solar collectors, the amount of useful energy generated by them, as well as the amount of energy needed to meet the load and auxiliary energy requirements were analyzed and compared. The extent to which increasing or decreasing the area of solar collectors affects the operation and efficiency of the system for different locations was also estimated. The results showed that in terms of efficiency, the use of solar collectors is most favorable in Slovakia and placed southernmost-located Croatia, where it also achieved the lowest annual auxiliary energy demand. The least favorable location, on the other hand, turned out to be the capital of Latvia. It is also worth noting that regardless of location, the area of solar collectors has a significant impact on the efficiency of the entire system
Predicting the Fertility of Long-term Honey Bee Drone Sperm Storage through Correlation of In vitro and In vivo Data
Full text linkThe article describes a study on the long-term storage of honey bee drone sperm and the evaluation of its quality. The current method of evaluating sperm quality, which involves inseminating queens and waiting for progeny. It is time-consuming and limited by the seasonal nature of beekeeping. The study aims to find correlations between queen fertility rates and sperm quality indicators in the queen spermatheca versus sperm quality indicators after storage in a thawed sperm sample. The study also examines the correlation between number of sperm cells, sperm motility, sperm viability, proportion of worker bee broods, sperm quality indicators in the spermatheca of queen bees, and duration of queen laying. The goal of this study is to validate in vitro-in vivo data and to facilitate future research on sperm storage issues
Circular Economy Options for Medical Textile Waste
Full text linkTo support circular economy and sustainability, all European Union Member states are obliged by 2025 to collect textiles separately. Textile waste has become a part of the Sustainable Development Goals that aims to innovation in the textile sector including textile collection, reuse, sorting and recycling. Along this, the healthcare industry has a significant impact on the environment: it releases annually around 26 Gt of CO2 greenhouse gas emissions and generates on an average 3 kg of medical waste per bed per day in healthcare facilities in Europe. The main focus of the research paper is to quantify the material flow of textile waste generated/likely to be generated in the health care sector as well as to calculate its potential for material recovery. Since medical textile recovery has limitations in sorting and recycling activities due to prevalence of infections, a systematic approach in textile waste management needs to be applied both at collection phase and treatment phase. Within the present research, a database with health care products categories (42 units) are developed, and the categories are characterized by textile type, application in health care sector, fibre, contamination level after use, potential product for substitution. To measure the recovery potential of the textile waste, the indicator analysis considering technological, environmental, infection control, and economic aspects is performed
Advancing Sustainable Acoustic Solution: Exploring the Sound Absorption Characteristics of Biodegradable Agricultural Wastes, Coconut Fiber, Groundnut Shell, and Sugarcane Fiber
No full textAmong the world's greatest threats is noise pollution particularly in megacities that affect the quality of life. This problem can cause negative effects on human health, disturbing emotion as well as human behavior. Natural fiber sound insulation materials have been demonstrated to be a potential substitute for the synthetic products currently employed in the sound insulation industry. Coconut fiber and sugarcane fiber happen to be biodegradable, earth-friendly, and present lower risks to the environment and human health. The research examines the sound absorption characteristics of natural biodegradable waste fibers (coconut fiber & sugarcane fiber) to evaluate their suitability as sound absorbers. The paper seeks to discover the internal workings of the sound absorption mechanisms of these materials and also to help design environmentally friendly acoustic solutions
Exploring the Efficacy of Random Linear Parameter Models for Forecasting Heating Demand in District Heating Networks
No full textThe heating and cooling sector accounts for approximately half of global energy consumption, making it a pivotal focus for energy transition efforts. District heating and cooling networks have emerged as efficient, innovative, and dominant technologies in various regions. Accurate forecasting of heating demand within these networks is imperative for effective energy transition and responsive demand management. While existing forecasting techniques primarily concentrate on limited parameters such as ambient temperature and time of day, this paper explores the multifaceted impact of various factors, including ambient temperature, energy prices, number of consumers, building types, and solar radiation, on heating demand. Through a comprehensive study of these determinants, a robust and efficient forecasting model is developed in this research. Specifically, a novel Random Linear Parameter Model (RLPM) is introduced for hourly heating demand forecasting within district heating networks. The model's performance is assessed and compared with existing forecasting models, namely Linear Regression, ARIMA, and RLPM. A notable advantage of the Random Parameter Linear Regression model lies in its capability to recognize unobserved parameters influencing demand and account for unobserved heterogeneity, providing a robust framework for incorporating these factors into the forecasting process. This study aims to underscore the proposed approach's advantages in terms of accuracy and its ability to estimate the determinants of heating load, thereby offering reliable future forecasting. The findings have the potential to significantly contribute to optimizing district heating systems by delivering more nuanced and dependable predictions of heating demand
Are BSR Municipalities on Track for Energy Transition?
No full textClimate neutrality targets and the growing decentralization of energy systems have substantially increased the role of municipalities in global energy transition. However, global shifts and national government demands have often left local public authorities unprepared to face numerous challenges related to local space planning, cost-effective integration, and decarbonization of electricity, heating, industry, and mobility. Therefore, there is a need to investigate the current state of municipal energy transition and analyze how municipalities face climate neutrality target achievement. This study conducts an integrated energy sustainability assessment to investigate the progress of the energy transition in six municipalities in the Baltic Sea region. A benchmarking approach is applied to compare the different levels of energy efficiency and decarbonization in the municipalities. The study reveals different energy consumption patterns of municipal buildings, which are influenced by various factors such as the type of building (educational, office, social facilities, etc.), the heat source (district heating or individual local heat source) and the energy efficiency management practices applied. In addition, a different trend in the installation of renewable energy capacity can be observed in municipalities in Latvia, Lithuania, Poland and Sweden. The study analyses the overall gap between the production and consumption of renewable energy to determine the storage potential and the role in the local energy transitions. The findings of this study highlight the key cornerstones in the current state of municipal energy transition, setting a foundation for better and more effective energy policy planning at national and local scales
Techno-Economic Model of District Heating Energy Hub: The Case of Latvia
No full textUp to 60% of Latvia’s energy resources are used as fuel for district heating systems. Heating sector is an important emitter of greenhouse gases – especially carbon dioxide. Therefore, reduction of carbon emissions of district heating systems are crucial in Latvia’s decarbonization efforts. One of the solutions is integration of energy hub in the district heating network. There are many types of energy hubs, and the most suitable solution must be found in each case. A goal of this study is to find the best solution for Latvia’s district heating systems to achieve decarbonization and use of green (renewable) hydrogen. This coincides with European Union’s plans to increase the use of green hydrogen not only in industrial and residential application, but in heat production as well.To facilitate the plans of the European Union and Latvia’s decarbonization needs a mathematical model made in Microsoft Excel is used as a method to explore the techno-economic aspects of the energy hub and its integration in the district heating system. Several alternatives are considered, and green hydrogen is used in all of those. Results show the economically most feasible alternative. Calculations are made on an annual term basis, considering such factors as electricity and district heating price, required capacity of electrolysis apparatus for hydrogen production etc.From the model some results are apparent – the price of electricity has a sizable impact on the economic feasibility of the project, and the best use for green hydrogen economics-wise may differ throughout the year as the price of electricity, hydrogen, district heating and methane gas change.