TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Missall, Siegmund A1 - Degembaeva, Nadira A1 - Akmatov, Kuban A1 - Zörner, Wilfried T1 - Energy Profiling of a High-Altitude Kyrgyz Community: Challenges and Motivations to Preserve Floodplain Ecosystems Based on Household Survey JF - Sustainability N2 - The floodplain areas along the Naryn River in Kyrgyzstan are essential as they hold the riparian (local) ecosystems because they provide firewood, pastureland, and areas for recreation and protection against erosion. Due to limited access to adequate, reliable, and sustainable energy services, the rural population usually derived their energy needs from multiple natural energy resources (i.e., firewood, charcoal, agricultural residues, animal dung, and wood branches). This is considered a common and predominant practice in rural Kyrgyzstan. This situation leads to a negative impact on local ecosystem services. In addition to that, the reliance on solid fuels contributes to indoor and outdoor air pollution, which is partially threatening the local ecosystem services. By contrast, the employment of renewable-based energy supply systems would substantially reduce the burden on the environment, which is mainly untapped. To integrate renewable energies, it is important to understand the energy behavior of floodplain communities. In that response, the presented article is the first attempt to capture the energy identity of the floodplain community of Kyrgyzstan based on a quantitative energy-based (on-site) household survey. Furthermore, the present research article synthesizes the driving factors that have a (direct or indirect) impact on the energy and local ecosystem services. In addition, the present article proposes a brief pathway for the sustainable energy transition. The article records the recommendation to integrate renewable energies to preserve the local ecosystems of Kyrgyzstan. UR - https://doi.org/10.3390/su132313086 KW - Central Asia KW - ecosystem services KW - energy pattern KW - energy profiling KW - floodplain community KW - high-altitude KW - household survey KW - Kyrgyzstan KW - renewable energies KW - sustainability Y1 - 2021 UR - https://doi.org/10.3390/su132313086 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-10895 SN - 2071-1050 N1 - This article belongs to the Special Issue "Floodplain Ecology and Sustainable Restoration with Regard to Ecosystem Services" VL - 13 IS - 23 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Greenough, Richard T1 - The energy situation in Central Asia BT - a comprehensive energy review focusing on rural areas JF - Energies N2 - The northern part of the globe is dominated by industrialisation and is well-developed. For many years, the southern part of the world (South Asia, Africa etc.) has been a target of research concentrating on access to energy (mainly electricity) in rural regions. However, the Central Asian region has not been a focus of energy research compared to South East Asia and Africa. Despite plentiful domestically available energy resources, the energy supply in Central Asia is very unevenly distributed between urban and rural areas. Almost half of the total population of Central Asia lives in rural areas and there is a lack of access to modern energy services to meet primary needs. To analyse the energy situation (i.e., electricity, heating, hot water consumption, cooking, etc.) in rural Central Asia, this paper reviews residential energy consumption trends in rural Central Asian regions as compared to urban areas. Furthermore, the paper illustrates the potential of renewable energies in Central Asia. To perform the study, a qualitative comparative analysis was conducted based on a literature review, data, and statistical information. In summary, the presented article discusses the rural energy situation analytically and provides in-depth insights of Central Asian energy infrastructure. UR - https://doi.org/10.3390/en14102805 KW - Central Asia KW - energy resources KW - rural energy supply KW - energy services KW - renewable energy Y1 - 2021 UR - https://doi.org/10.3390/en14102805 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-10908 SN - 1996-1073 VL - 14 IS - 10 PB - MDPI CY - Basel ER - TY - JOUR A1 - Vannahme, Anna A1 - Ehrenwirth, Mathias A1 - Schrag, Tobias T1 - Enhancement of a district heating substation as part of a low-investment optimization strategy for district heating systems JF - Resources N2 - In an ongoing project, low-investment measures for the optimization of district heating systems are analyzed. The optimization strategies are collected in a catalog, which is the core of a guideline. The application of this guideline is demonstrated using two concrete district heating networks as examples. In this study, the improvement of an analog controlled district heating substation by an electronic controller is investigated. High supply temperatures and heat losses are often a challenge in district heating networks. The district heating substations have a major influence on the network return temperatures. The comparison of the two substation setups with analog and electronic controllers is carried out by laboratory measurement. It can be shown that the return temperatures can be reduced by an average of 20 K in winter and transition, as well as 16 K in summer. The district heating network losses are calculated for one of both specific district heating networks. They are calculated from the ratio of network losses to generated energy. The generated energy is the sum of network losses and consumer demand. The thermal losses of the network can be reduced by 3%. The volume flow in the heating network can be reduced to a quarter. Therefore, the pumping energy requirement drops sharply since these changes cubically affect the volume flow UR - https://doi.org/10.3390/resources10050053 KW - district heating substation KW - control KW - optimization KW - local district heating networks KW - non-retrofitted single-family houses KW - thermal test rig Y1 - 2021 UR - https://doi.org/10.3390/resources10050053 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-10951 SN - 2079-9276 VL - 10 IS - 5 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bugaje, Aminu A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried T1 - Electric two-wheeler vehicle integration into rural off-grid photovoltaic system in Kenya JF - Energies N2 - In both rural and urban areas, two-wheeler vehicles are the most common means of transportation, contributing to local air pollution and greenhouse gas emissions (GHG). Transitioning to electric two-wheeler vehicles can help reduce GHG emissions while also increasing the socioeconomic status of people in rural Kenya. Renewable energy systems can play a significant role in charging electric two-wheeled vehicles, resulting in lower carbon emissions and increased renewable energy penetration in rural Kenya. As a result, using the Conventional and Renewable Energy Optimization (CARNOT) Toolbox in the MATLAB/Simulink environment, this paper focuses on integrating and modeling electric two-wheeled vehicles (e-bikes) into an off-grid photovoltaic Water-Energy Hub located in the Lake Victoria Region of Western Kenya. Electricity demand data obtained from the Water-Energy Hub was investigated and analyzed. Potential solar energy surplus was identified and the surplus was used to incorporate the electric two-wheeler vehicles. The energy consumption of the electric two-wheeler vehicles was also measured in the field based on the rider’s driving behavior. The modeling results revealed an annual power consumption of 27,267 kWh, a photovoltaic (PV) electricity production of 37,785 kWh, and an electricity deficit of 370 kWh. The annual results show that PV generation exceeds power consumption, implying that there should be no electricity deficit. The results, however, do not represent the results in hourly resolution, ignoring the impact of weather fluctuation on PV production. As a result, in order to comprehend the electricity deficit, hourly resolution results are shown. A load optimization method was designed to efficiently integrate the electric 2-wheeler vehicle into the Water-Energy Hub in order to alleviate the electricity deficit. The yearly electricity deficit was decreased to 1 kWh and the annual electricity consumption was raised by 11% (i.e., 30,767 kWh), which is enough to charge four more electric two-wheeler batteries daily using the load optimization technique. UR - https://doi.org/10.3390/en14237956 KW - Lake Victoria KW - photovoltaic KW - off-grid KW - model KW - electric two-wheeled vehicle KW - Water-Energy Hub KW - CARNOT Y1 - 2021 UR - https://doi.org/10.3390/en14237956 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-11070 SN - 1996-1073 VL - 14 IS - 23 PB - MDPI CY - Basel ER - TY - CHAP A1 - Beringer, Jakob A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Zörner, Wilfried ED - Söllner, Matthias ED - Pirkl, Gerald T1 - Sustainable materials for insulating high-altitude rural Kyrgyz residential houses: A parametric economic study T2 - Applied Research Conference 2021, Conference Proceedings Y1 - 2021 UR - https://www.oth-aw.de/files/oth-aw/Aktuelles/Veroeffentlichungen/Applied_Research_Conference_ARC2021_Proceedings.pdf SP - 183 EP - 188 PB - Ostbayerische Technische Hochschule Amberg-Weiden CY - Amberg ER - TY - CHAP A1 - Knepper, Karoline A1 - Ehrenwirth, Mathias A1 - Zörner, Wilfried ED - Söllner, Matthias ED - Pirkl, Gerald T1 - Potential of e- mobility in rural areas – Evaluation of opportunities and barriers based on literature review T2 - Applied Research Conference 2021, Conference Proceedings Y1 - 2021 UR - https://www.oth-aw.de/files/oth-aw/Aktuelles/Veroeffentlichungen/Applied_Research_Conference_ARC2021_Proceedings.pdf SP - 216 EP - 220 PB - Ostbayerische Technische Hochschule Amberg-Weiden CY - Amberg ER - TY - CHAP A1 - Bugaje, Aminu A1 - Yadav, Akhilesh A1 - Mehta, Kedar A1 - Ojinji, Felicia A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried ED - Schulz, Detlef T1 - Influence of input parameters on artificial neural networks for off-grid solar photovoltaic power forecasting T2 - NEIS 2021 KW - solar power forecast KW - off-grid solar system KW - artificial neural networks KW - mean squared error KW - correlation coefficient KW - mean absolute error Y1 - 2021 UR - https://www.vde-verlag.de/proceedings-en/565651017.html SN - 978-3-8007-5651-3 SN - 978-3-8007-5652-0 N1 - Auch veröffentlicht auf IEEE: https://ieeexplore.ieee.org/document/9698257 SP - 135 EP - 141 PB - VDE Verlag CY - Berlin ER - TY - CHAP A1 - Bugaje, Aminu A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Bär, Katharina A1 - Zörner, Wilfried ED - Schulz, Detlef T1 - Development of a load management algorithm using nonlinear programming (NLP) for optimum integration of electric-mobility solutions into rural off-grid PV systems T2 - NEIS 2020 KW - load management KW - NLP KW - CARNOT KW - electric mobility KW - off-grid KW - PV systems KW - objective function Y1 - 2020 UR - https://www.vde-verlag.de/proceedings-en/565359022.html SN - 978-3-8007-5359-8 SN - 978-3-8007-5360-4 N1 - Auch veröffentlicht auf IEEE: https://ieeexplore.ieee.org/document/9273412 SP - 167 EP - 172 PB - VDE Verlag CY - Berlin ER - TY - CHAP A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Greenough, Richard T1 - A parametric study on the feasibility of solar-thermal space heating and hot water preparation under cold climates in Central Asian rural areas T2 - EuroSun 2020 Proceedings UR - https://dx.doi.org/10.18086/eurosun.2020.04.03 KW - cold climate KW - building KW - solar-thermal energy KW - space heating KW - domestic hot water Y1 - 2020 UR - https://dx.doi.org/10.18086/eurosun.2020.04.03 PB - International Solar Energy Society CY - Freiburg ER - TY - CHAP A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Greenough, Richard T1 - Impact of locally available thermal insulation structures on space heating demand of high-altitude rural buildings BT - a case study of Kyrgyzstan T2 - EuroSun 2020 Proceedings UR - https://dx.doi.org/10.18086/eurosun.2020.04.04 KW - domestic space heating KW - energy efficiency KW - cold climate KW - high-altitude KW - thermal insulation Y1 - 2020 UR - https://dx.doi.org/10.18086/eurosun.2020.04.04 PB - International Solar Energy Society CY - Freiburg ER - TY - JOUR A1 - Werner, Melanie A1 - Ehrenwirth, Mathias A1 - Muschik, Sebastian A1 - Trinkl, Christoph A1 - Schrag, Tobias T1 - Operational experiences with a temperature-variable district heating network for a rural community JF - Chemical Engineering & Technology N2 - The potential of utilizing temperature-variable district heating systems in rural areas was investigated. A local district heating system in Germany and the related project NATAR are briefly described; measurement data is evaluated. Operational experiences with a seasonal temperature reduction and consequent advantages for different heat generation systems and heat storages are discussed. The analysis of measurement data reveals a high optimization potential for solar thermal systems in case of an integration both into a low- and a high-temperature storage. Furthermore, a combined heat-and-power plant in combination with a CO2 heat pump promises sector-coupling potential and high electricity self-consumption. UR - https://doi.org/10.1002/ceat.202100114 KW - district heating network KW - low temperature KW - sector coupling Y1 - 2021 UR - https://doi.org/10.1002/ceat.202100114 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-20824 SN - 0930-7516 VL - 46 IS - 3 SP - 482 EP - 490 PB - Wiley-VCH CY - Weinheim ER - TY - CHAP A1 - Lauermann, Magdalena A1 - Betz, Florian A1 - Mehta, Kedar A1 - Thevs, Niels A1 - Ehrenwirth, Mathias A1 - Zörner, Wilfried A1 - Cyffka, Bernd T1 - Preservation of Selected Ecosystem Services in the Floodplains of the Naryn River (Kyrgyzstan): Introducing the ÖkoFlussPlan Project T2 - Beiträge zum 50. und 51. Jahrestreffen des Arbeitskreises Hydrologie 2018 in Koblenz und 2019 in Heidelberg Y1 - 2020 UR - https://www.uni-augsburg.de/de/fakultaet/fai/geo/forschung/geographicaaugustana/ SP - 47 EP - 53 PB - Institut für Geographie, Universität Augsburg CY - Augsburg ER - TY - CHAP A1 - Ramm, Tobias A1 - Ehrenwirth, Mathias A1 - Schrag, Tobias ED - Haumer, Anton T1 - Modelling of the central heating station within a district heating system with variable temperatures T2 - Proceedings of the 13th International Modelica Conference UR - http://dx.doi.org/10.3384/ecp19157567 KW - district heating system KW - model KW - Modelica KW - variable temperature KW - validation Y1 - 2019 UR - http://dx.doi.org/10.3384/ecp19157567 SN - 978-91-7685-122-7 SN - 1650-3686 SN - 1650-3740 SP - 567 EP - 576 PB - Modelica Association and Linköping University Electronic Press CY - Linköping ER - TY - CHAP A1 - Schrag, Tobias A1 - Ehrenwirth, Mathias A1 - Ramm, Tobias A1 - Vannahme, Anna A1 - Trinkl, Christoph ED - Belasri, Ahmed ED - Beldjilali, Sid Ahmed T1 - Solar energy use in district heating networks T2 - ICREEC 2019: Proceedings of the 1st International Conference on Renewable Energy and Energy Conversion UR - https://doi.org/10.1007/978-981-15-5444-5_1 KW - district heating systems KW - solar energy KW - heat pumps Y1 - 2020 UR - https://doi.org/10.1007/978-981-15-5444-5_1 SN - 978-981-15-5443-8 SN - 978-981-15-5446-9 SN - 978-981-15-5444-5 SN - 2352-2534 SN - 2352-2542 N1 - Access provided by Nationallizenz Ebooks Medicine SP - 3 EP - 10 PB - Springer CY - Singapur ER - TY - CHAP A1 - Vannahme, Anna A1 - Ramm, Tobias A1 - Ehrenwirth, Mathias A1 - Schrag, Tobias ED - Haumer, Anton T1 - Comparison of a usual heat-transfer-station with a hydraulic modified version under the aspect of exergy saving T2 - Proceedings of the 13th International Modelica Conference UR - http://dx.doi.org/10.3384/ecp19157647 KW - heat-transfer-station KW - hydraulic system KW - control design KW - district heating KW - single-family house Y1 - 2019 UR - http://dx.doi.org/10.3384/ecp19157647 SN - 978-91-7685-122-7 SN - 1650-3686 SN - 1650-3740 SP - 647 EP - 654 PB - Linköping University Electronic Press CY - Linköping ER - TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried T1 - Mapping Potential for Improving Rural Energy Services in Kyrgyzstan: Factors for Achieving Sustainable Development Goals in the Community Context JF - World N2 - Energy is a pivotal element for overall development. Therefore, affordable and clean energy for all (Sustainable Development Goal 7) is one of the important elements. Despite a suitable approach, Kyrgyzstan lags behind to achieve its Sustainable Development Goals by 2030. Improving access to energy can significantly impact the progress of many other sustainable development targets. However, access to reliable, sustainable, and adequate energy is a crucial task in rural Kyrgyzstan. Taking into consideration the energy situation and the importance of the availability of energy services, the overarching aim of the presented article is to map the potential of improving rural energy services to foster overall sustainable development goals. The article presents the most relevant information about rural energy usage behaviour based on three primary pillars: energy demand, energy carrier, and energy sources. In addition, the presented research article synthesises the key driving factors which have a direct or indirect impact on the energy services in rural areas. The summarised data displays a deep insight into a variety of complex and dynamic household energy consumption patterns. The article provides a potential solution nexus to foster improved energy services in rural Kyrgyzstan and therefore to foster the overall sustainable development in Kyrgyzstan. The findings of the article help to formulate a strategy to design rural energy services for policy makers and stockholders. UR - https://doi.org/10.3390/world3030032 KW - energy need KW - rural livelihood KW - energy poverty KW - energy services KW - sustainable energy transition KW - sustainable development goals KW - Kyrgyzstan KW - Central Asia Y1 - 2022 UR - https://doi.org/10.3390/world3030032 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-29518 SN - 2673-4060 VL - 3 IS - 3 SP - 586 EP - 606 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried T1 - Towards Sustainable Community Development through Renewable Energies in Kyrgyzstan: A Detailed Assessment and Outlook JF - World N2 - In rural Kyrgyzstan, the energy need is usually derived from multiple natural energy resources such as firewood, charcoal, agricultural residues, animal dung, and wood branches, which are considered common and predominant practices. Because of the non-sustainable resources and heavy reliance on the environment, Kyrgyzstan is one of the most vulnerable countries to climate change in Central Asia. On the contrary, the great renewable energy potential in Kyrgyzstan is untapped, which could be the most promising solution to ensuring sustainable energy supply in the country. However, because of the lack of scientific knowledge, current energy policies, and the lack of infrastructure, renewable resources are mainly untapped. To exploit the country’s renewable energy potential, there is a need for a systematic diagnosis to develop a strategy to explore renewables in Kyrgyzstan, which is currently missing in the existing literature. In that regard, the presented study aims to assess the current status of renewable energy sources by considering the local energy context from a potential point of view. Further to this, it provides a comparative overview through a matrix of strengths, weaknesses, opportunities, and threats. Such novel analysis would be the fundamental base for formulating policy advice and a national plan to enhance the utilization of renewable energy in Kyrgyzstan. The presented analysis was carried out based on the extensive literature review, the country’s national plan, and the existing energy policies of Kyrgyzstan. The article found out that there is huge potential available for the renewable energy market. As compared to other renewable energy sources, solar energy has great potential and can be considered one of the pioneer sustainable sources for integration into the country’s power generation framework. UR - https://doi.org/10.3390/world3020018 KW - Central Asia KW - energy services KW - high-altitude KW - Kyrgyzstan KW - renewable energy resources KW - sustainable energy Y1 - 2022 UR - https://doi.org/10.3390/world3020018 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-28086 SN - 2673-4060 VL - 3 IS - 2 SP - 327 EP - 343 PB - MDPI CY - Basel ER - TY - JOUR A1 - Werner, Melanie A1 - Muschik, Sebastian A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Schrag, Tobias T1 - Sector Coupling Potential of a District Heating Network by Consideration of Residual Load and CO2 Emissions JF - Energies N2 - The growing share of fluctuating renewable electricity production within the German energy system causes the increasing necessity for flexible consumers, producers, and storage technologies to balance supply and demand. District heating networks with combined heat and power units, Power-to-Heat applications, and thermal energy storage capacities can serve as one of these flexible options. In this context, a simulation model of the district heating network of the rural community Dollnstein, Germany, was built. With the residual load of different regional areas (Germany, Bavaria, Eichstätt, Dollnstein) it is investigated, how the heat generators can operate in an electricity market beneficial way. Two different control algorithms were evaluated: Due to a correlation between the residual loads and the CO2 emissions of the electricity mix, the CO2 savings achieved by this control algorithm are determined. Another way to operate electricity market beneficial is to consider the current CO2 emissions of each region. The main outcomes of this paper are, that there is a high potential for sector coupling by shifting the operation times of a CHP and a heat pump according to the residual load. The electricity demand of the heat pump can be met in terms of low CO2 emissions of the electricity mix, while the CHP can replace electricity with high CO2 emissions. These results can be improved, by considering not the residual load but the current CO2 emissions in the control algorithm. UR - https://doi.org/10.3390/en15176281 KW - district heating networks KW - sector coupling KW - residual load KW - CO2 emissions Y1 - 2022 UR - https://doi.org/10.3390/en15176281 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-27820 SN - 1996-1073 VL - 15 IS - 17 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bott, Christoph A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Bayer, Peter T1 - Component-based modeling of ground-coupled seasonal thermal energy storages JF - Applied Thermal Engineering N2 - Seasonal thermal energy storages are considered a central element of modern, innovative energy systems and help to harmonize fluctuating energy sources. Furthermore, they allow for an improved coupling between the electricity and heating sectors. Despite recent improvements of planning processes and enhanced models, significant discrepancies between projected and measured heat losses were revealed. Additional shortcomings of available tools relate to limitations in specifying geometry, internal design, or physical processes. Addressing these drawbacks, this study employs a revised, alternative approach by using a flexible, component-based, model (“STORE”). It allows variable flexible parameterizations to study diverse design scenarios. After introducing relevant seasonal thermal energy storage components, processes and mechanisms, datasets, and evaluation techniques, a plausibility test is presented that applies a common thermal energy storage model for benchmarking. In a test study, the re-use of a circa 1,000 m3 large swimming pool is simulated. STORE is used to investigate performance trends caused by different designs (e.g., insulation thicknesses, materials at individual interfaces). For the plausibility test, the results show a high degree of coverage and good applicability. Further, the results of the test study show a storage efficiency of 12.4% for an uninsulated base case, which can be improved to 69.5% in case of the most complex, highly insulated configuration. Critical trends are revealed, covering reduced peak capacity levels (26.5 to 23.5 MWh) and raised average filling temperatures (39.1 to 45.2 °C). Improved long-term behavior involves reduced environmental impacts due to reduced heating of the ambient soil (+7.9 K compared to +14.1 K after 2 years). General conclusions reveal that an optimal design should initially focus on an external cover of soil and top insulation. However, evaluations should base on multiple parameters depending on the target criteria. This is where the present model is highly useful. The capability of STORE to rapidly analyze a plethora of scenarios proves its high applicability for optimizing the planning processes of seasonal thermal energy storage projects. UR - https://doi.org/10.1016/j.applthermaleng.2022.118810 KW - Seasonal Storage KW - Thermal Energy Storage KW - Component-based Modeling KW - Matlab / Simulink KW - Large-scale TES KW - Planning and Design Y1 - 2022 UR - https://doi.org/10.1016/j.applthermaleng.2022.118810 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-34926 SN - 1873-5606 VL - 2022 IS - 214 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Vannahme, Anna A1 - Busch, Jonas A1 - Ehrenwirth, Mathias A1 - Schrag, Tobias T1 - Experimental Study of District Heating Substations in a Hardware-in-the-Loop Test Rig JF - Resources N2 - This study compares two district heating substation systems for implementation in rural district heating networks with non-retrofitted single- and two-family houses. The aim is to determine which system has the potential to provide lower return temperatures and/or lower power peak demand. A hardware-in-the-loop-test rig was utilized to measure the two district heating substations under real operation conditions. This experimental study demonstrates that load balancing of the district heating network is attainable with the district heating substation with storage. This is especially advantageous when there is a high demand for domestic hot water. Overall, both systems yield comparable return temperatures. UR - https://doi.org/10.3390/resources12040043 KW - district heating substation KW - local district heating network KW - non-retrofitted single- and two-family-houses KW - thermal hardware-in-the-loop test rig Y1 - 2023 UR - https://doi.org/10.3390/resources12040043 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-33382 SN - 2079-9276 VL - 12 IS - 4 PB - MDPI CY - Basel ER - TY - JOUR A1 - Igiligi, Anthony A1 - Vielhauer, Armin A1 - Ehrenwirth, Mathias A1 - Hurm, Christian A1 - Summ, Thorsten A1 - Trinkl, Christoph A1 - Navarro Gevers, Daniel T1 - Assessment of Conservation Voltage Reduction in Distribution Networks with Voltage Regulating Distribution Transformers JF - Energies N2 - The application of voltage reduction in medium and low voltage grids to reduce peak power demand or energy consumption has been implemented since the 1980s using several approaches. Conservation Voltage Reduction (CVR), as one such approach, uses a voltage control device to reduce or increase the voltage setpoint on a busbar, thereby reducing or increasing the amount of active and reactive power supply in the network. Voltage regulation for CVR is always implemented according to established network planning standards in each country. Research in this field has proven that a CVR factor (CVRf) of 0.7–1.5 for peak demand reduction can be achieved. This is an evaluation metric of CVR. The aim of this research is to determine and validate CVRf for peak demand reduction by comparing actual results obtained during regular tap changes with other randomly distributed periods outside tap change operations, using a set of measurement data. It is important to understand CVR deployment capability by evaluating CVR potentials from historical random tap operations before a robust network-wide deployment is introduced. This research provides such guidance. It also provides a novel approach to determining tap changes from voltage measurements using a time-based algorithm. A CVRf ranging from 0.95 to 1.61 was estimated using a measurement dataset from a test field. The result of the entire evaluation shows that the CVRf are smaller during peak PV production and greater during peak demand periods. Further evaluation using statistical hypotheses testing and a control chart was used to validate the evaluation. UR - https://doi.org/10.3390/en16073155 KW - conservation voltage reduction KW - peak power KW - tap change KW - voltage regulating distribution transformers Y1 - 2023 UR - https://doi.org/10.3390/en16073155 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-33449 SN - 1996-1073 VL - 16 IS - 7 PB - MDPI CY - Basel ER - TY - JOUR A1 - Summ, Thorsten A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Pischow, Kaj A1 - Greenough, Richard A1 - Oyinlola, Muyiwa T1 - Effect of argon concentration on thermal efficiency of gas-filled insulating glass flat-plate collectors JF - Applied Thermal Engineering N2 - Insulating glass flat-plate collectors can save cost by being produced quickly and automatically in insulated glass production facilities, and they can be filled with argon to reduce heat loss. During its lifetime, the collector is likely to lose argon because of gradual material degradation of the sealing. However, information on the influence of the argon concentration on the collector efficiency is limited. Therefore, the objective of this research work was to analyse this effect. A theoretical material property calculation of argon-air mixtures was carried out to determine the convective losses with variable argon concentrations. Thermal collector performance was measured experimentally using an outdoor solar tracker test rig. The results strongly suggest, that the influence of argon concentration on both the convective losses and the thermal efficiency is non-linear. The measurements revealed that an argon concentration of 90 % can increase average thermal performance by 6.7 ± 4.8 percentage points. An increase in argon concentration from 0 % to 50 % has almost twice the effect on average thermal efficiency as an increase from 50 % to 90 %. Concluding from these results, an argon leakage threshold of 2.5 percentage points per year is proposed to avoid disproportionate loss of efficiency over time. UR - https://doi.org/10.1016/j.applthermaleng.2023.120657 KW - Insulating glass KW - Flat-plate collector KW - Argon KW - Gas concentration KW - Efficiency measurement KW - Convective heat transfer Y1 - 2023 UR - https://doi.org/10.1016/j.applthermaleng.2023.120657 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-37875 SN - 1873-5606 SN - 1359-4311 VL - 2023 IS - 230, Part A PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Vannahme, Anna A1 - Ehrenwirth, Mathias A1 - Schrag, Tobias T1 - Development and application of a guideline for assessing optimization potentials for district heating systems JF - Energy N2 - Integrating renewable energies into district heating systems has a large potential to reduce CO2-emissions in the heating sector. As district heating systems offer the possibility of incorporating renewable energies into the heat supply, new systems have to be built and the existing networks must be maintained. This study investigates ways to optimize existing district heating systems in order to ensure economic sustainability in the long-term. Previous case studies have elaborated on a variety of optimization measures. However, to date, these measures have neither been collected nor consistently assessed for a wider application range. Therefore, in the study presented here a system for assessing the ecological and economic benefits of optimization measures was developed and applied. The assessment method utilized showed that optimization of district heating consumer substations and adding of a central buffer storage tank has a high optimization potential in comparison to intermittent operation strategy, which has a significantly lower optimization potential. From this information and the transferability data, a district heating operator can determine which optimization measure should be prioritized, which is shown at the end of the paper on an example case. UR - https://doi.org/10.1016/j.energy.2024.131226 Y1 - 2024 UR - https://doi.org/10.1016/j.energy.2024.131226 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-47196 SN - 1873-6785 SN - 0360-5442 VL - 2024 IS - 297 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Summ, Thorsten A1 - Oyinlola, Muyiwa A1 - Khattak, Sanober A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried T1 - Towards maximum cost-effectiveness: multi-objective design optimisation of insulating glass flat-plate collectors JF - Applied Thermal Engineering N2 - A significant challenge in the advancement of solar thermal heating systems lies in the unexplored techno-economic potential of insulating glass flat-plate collectors. These collectors are constructed in accordance with the specifications of standard insulating glass units and have emerged over the past decade as a promising design concept for enhancing the cost-effectiveness of solar thermal systems. However, substantial findings regarding the techno-economic viability of their production are still pending. The aim of this paper is to optimise insulating glass collector designs for solar district heating applications by identifying key design parameters that maximise cost-effectiveness. This study employed a five-stage methodology. It included thermo-hydraulic collector modelling using MATLAB/Simscape and the CARNOT Toolbox. The model was validated against experimental performance tests. A Latin hypercube computational design with 250,000 samples was set up to train supervised machine learning metamodels and perform a multi-objective optimisation using an elitist genetic algorithm. The study identified the argon concentration, collector length, and width as critical parameters influencing efficiency. Larger, thinner collectors demonstrated superior performance due to reduced convective losses and increased aperture-to-surface ratios. The optimisation revealed that the insulating glass collectors could achieve a 7.7 percentage point increase in efficiency, a 19.4 % reduction in material cost, and a 14.5 % decrease in weight compared to market-available flat-plate collectors. However, the direct economic comparison was not considered strong in evidence due to a lack of economic data from technology providers. The most cost-effective designs featured an argon concentration of 99 %, sealing thickness of 31.2 mm, and a glazing thickness of 4.1 mm, and 4.5 mm, while collector length and width varied more significantly. The research findings indicate the techno-economic potential of insulating glass collectors, demonstrating their ability to outperform conventional flat-plate collectors in terms of cost-effectiveness and efficiency. Future studies should focus on producing and testing larger modules and incorporating production costs to fully realise their potential for solar district heating applications. This study provides valuable guidelines for IGU designers and producers aiming to develop cost-effective and efficient solar thermal collectors for district heating systems. UR - https://doi.org/10.1016/j.applthermaleng.2024.124594 Y1 - 2024 UR - https://doi.org/10.1016/j.applthermaleng.2024.124594 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-53618 SN - 1359-4311 VL - 2025 IS - 258 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mehta, Kedar A1 - Lwakatare, Bertha A1 - Zörner, Wilfried A1 - Ehrenwirth, Mathias T1 - Mini-grid performance in Sub-Saharan Africa: case studies from Tsumkwe and Gam, Namibia JF - Sustainable Energy Research N2 - This paper investigates the performance analysis and operational challenges of mini-grids in Sub-Saharan Africa, focusing on the Tsumkwe and Gam mini-grids, the only officially recognized mini-grids in Namibia. The study addresses a critical gap in understanding mini-grid efficiency, technical difficulties, and future potential. The key research questions focus on assessing mini-grid performance, identifying technical and operational challenges, quantifying the relationship between electricity demand and supply, and providing recommendations for enhancing rural electrification through mini-grids. These insights are crucial for evaluating the effectiveness of mini-grids in the African context and understanding their role in advancing rural electrification. By using a mixed-method approach, the research combines quantitative and qualitative data to offer a comprehensive analysis of these two mini-grid systems of Namibia. The data collected from 2017 to 2022 include metrics on energy supply, consumption, photovoltaic generation, community load, and meteorological conditions. Qualitative insights were gathered through field visits, surveys, and interviews with mini-grid operators, allowing for a thorough examination of community perspectives, operational issues, and technical performance. The findings reveal that the Tsumkwe mini-grid has seen a decline in efficiency due to maintenance problems and battery overheating, while the Gam mini-grid, initially oversized, now struggles with increased demand and new connections. This study provides the first detailed technical insights, identifies consumer archetypes, and evaluates the energy dynamics of mini-grids in Namibia. Recommendations include improved maintenance protocols, advanced battery management, and enhanced data monitoring. By analyzing Tsumkwe and Gam, this paper offers valuable lessons for mini-grid development in Sub-Saharan Africa, stressing the need for continuous evaluation and strategic improvements to achieve sustainable rural electrification. UR - https://doi.org/10.1186/s40807-025-00174-y Y1 - 2025 UR - https://doi.org/10.1186/s40807-025-00174-y UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-65316 SN - 2731-9237 VL - 12 IS - 1 PB - SpringerOpen CY - Singapore ER - TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Zörner, Wilfried A1 - Greenough, Richard T1 - Need of energy transition at roof of the world BT - Correlative approach to interpret energy identity of high-altitude Central Asian communities JF - Energy for Sustainable Development UR - https://doi.org/10.1016/j.esd.2023.101271 Y1 - 2023 UR - https://doi.org/10.1016/j.esd.2023.101271 SN - 2352-4669 SN - 0973-0826 VL - 2023 IS - 76 PB - Elsevier CY - Amsterdam ER -