@article{MehtaEhrenwirthMissalletal.2021, author = {Mehta, Kedar and Ehrenwirth, Mathias and Missall, Siegmund and Degembaeva, Nadira and Akmatov, Kuban and Z{\"o}rner, Wilfried}, title = {Energy Profiling of a High-Altitude Kyrgyz Community: Challenges and Motivations to Preserve Floodplain Ecosystems Based on Household Survey}, volume = {13}, pages = {13086}, journal = {Sustainability}, number = {23}, publisher = {MDPI}, address = {Basel}, issn = {2071-1050}, doi = {https://doi.org/10.3390/su132313086}, year = {2021}, abstract = {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.}, language = {en} } @article{MehtaEhrenwirthTrinkletal.2021, author = {Mehta, Kedar and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {The energy situation in Central Asia}, volume = {14}, pages = {2805}, journal = {Energies}, subtitle = {a comprehensive energy review focusing on rural areas}, number = {10}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en14102805}, year = {2021}, abstract = {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.}, language = {en} } @article{VannahmeEhrenwirthSchrag2021, author = {Vannahme, Anna and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Enhancement of a district heating substation as part of a low-investment optimization strategy for district heating systems}, volume = {10}, pages = {53}, journal = {Resources}, number = {5}, publisher = {MDPI}, address = {Basel}, issn = {2079-9276}, doi = {https://doi.org/10.3390/resources10050053}, year = {2021}, abstract = {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}, language = {en} } @article{BugajeEhrenwirthTrinkletal.2021, author = {Bugaje, Aminu and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {Electric two-wheeler vehicle integration into rural off-grid photovoltaic system in Kenya}, volume = {14}, pages = {7956}, journal = {Energies}, number = {23}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en14237956}, year = {2021}, abstract = {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.}, language = {en} } @article{ContiSaidiGoldbrunner2020, author = {Conti, Fosca and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Evaluation Criteria and Benefit Analysis of Mixing Process in Anaerobic Digesters of Biogas Plants}, volume = {24}, journal = {Environmental and Climate Technologies}, number = {3}, publisher = {De Gruyter Poland}, address = {Warsaw}, issn = {2255-8837}, doi = {https://doi.org/10.2478/rtuect-2020-0105}, pages = {305 -- 317}, year = {2020}, abstract = {A valid method to evaluate decisions of a project proposal is the so-called cost-benefit analysis. Criteria are selected and properly weighted to determine if the project is effective and feasible. The present research study is focused on methodical selection of design parameters to install two propeller mixers inside anaerobic digesters of biogas plants. A cylindrical tank of 1400 m3 was considered. For the model-based optimisation, the substrate was considered as a non-Newtonian fluid with a density of 1090 kg/m3. The Oswald-de Waele power-law model was selected to account for the rheological behaviour of the fluid. Installation parameters of the mixers were rotational angles and heights of the shafts of the two propellers. A computational model was developed to simulate the fluid dynamics depending on the mixing process inside the tank. Several configurations were analysed according to evaluating criteria such as the value of the fluid velocity, its distribution along the three spatial dimensions, and the power consumption to rotate the mixers. The maximum fluid velocity and minimum power consumption were observed when the propellers are located at intermediate height inside the tank and with the shafts perpendicular to the tank radius. With this configuration, the fluid reaches a maximum velocity of 0.28 m/s. According to the investigation, it is evident that mixing systems with propeller shafts deep-seated and parallel to the tank radius should be avoided, both in term of efficiency of the fluid mixing distribution and in term of power consumption.}, language = {en} } @article{ContiSaidiGoldbrunner2020, author = {Conti, Fosca and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Numeric Simulation-Based Analysis of the Mixing Process in Anaerobic Digesters of Biogas Plants}, volume = {43}, journal = {Chemical Engineering \& Technology}, number = {8}, publisher = {Wiley}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.201900650}, pages = {1522 -- 1529}, year = {2020}, abstract = {Stirring systems with two rotational three-bladed propellers were analyzed using computational fluid dynamics. The propellers are located at three heights and seven angles in a tank with 9 m radius. The fluid was characterized by non-Newtonian rheology and simulated by applying the k-ε turbulence model and the standard k-ω model. Reynolds numbers were estimated. High fluid speeds were obtained with the propellers located at a height of 2 m and oriented at 90° with respect to the tank radius. In the top regions of the tank, the fluid velocity was generally less intense and less affected by the angle setting. The configurations identified as good mixing systems showed power consumptions broadly distributed around 30 kW.}, language = {en} } @article{BaerWagenederSolkaetal.2020, author = {B{\"a}r, Katharina and Wageneder, Stefanie and Solka, Felix and Saidi, Abdessamad and Z{\"o}rner, Wilfried}, title = {Flexibility Potential of Photovoltaic Power Plant and Biogas Plant Hybrid Systems in the Distribution Grid}, volume = {43}, journal = {Chemical Engineering \& Technology}, number = {8}, publisher = {Wiley}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.202000025}, pages = {1571 -- 1577}, year = {2020}, abstract = {The potential of combining biogas and photovoltaic (PV) power plants in hybrid systems in the German distribution grid is analyzed. The focus of the present research is on balancing the intermittent power supply from PV power plants with the controllable power production of combined heat and power (CHP) units of biogas plants within a period of seconds. To achieve an increase of the total energy feed-in of biogas and PV power plants to the electricity grid, a biogas plant energy management system is described. System parameters, such as the variable feed-in of PV power plants or power ramps of the start-up process of controllable biogas plant CHP unit, are described and adapted to the global installed capacity of PV power plant and biogas plants in the German distribution grid.}, language = {en} } @article{DotzauerPfeifferLaueretal.2018, author = {Dotzauer, Martin and Pfeiffer, Diana and Lauer, Markus and Pohl, Marcel and Mauky, Eric and B{\"a}r, Katharina and Sonnleitner, Matthias and Z{\"o}rner, Wilfried and Hudde, Jessica and Schwarz, Bj{\"o}rn and Faßauer, Burkhardt and Dahmen, Markus and Rieke, Christian and Herbert, Johannes and Thr{\"a}n, Daniela}, title = {How to measure flexibility - Performance indicators for demand driven power generation from biogas plants}, volume = {2019}, journal = {Renewable Energy}, number = {134}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1879-0682}, doi = {https://doi.org/10.1016/j.renene.2018.10.021}, pages = {135 -- 146}, year = {2018}, abstract = {Flexible power provision from biogas can significantly contribute to energy systems with high shares of renewables. However, the characteristics and demands for this flexibility are not clearly defined or measured. In this paper eight indicators are defined to shape "flexibility" and perform a downstream investigation of eight research projects focusing on flexible energy provision of biogas plants. The indicators are structured in three dimensions (1) velocity (ramps) by which the system can be modulated, (2) power range (bandwidth) and (3) duration for specific load conditions. Based on these indicators bottlenecks for the flexibility potential were identified. One crucial result shows that short-term flexibility of biogas plants is mainly driven by properties of the combined heat and power unit (velocity and bandwidth). The long-term flexibility depends mainly on gas storage, mode of operation and ability for modulation of the target gas production.}, language = {en} } @inproceedings{SchmittReumSummetal.2024, author = {Schmitt, David and Reum, Tobias and Summ, Thorsten and Trinkl, Christoph and Schrag, Tobias}, title = {Investigation of the Flexibility Potential by Decoupling Building Mass and Room Temperature}, booktitle = {International Sustainable Energy Conference - Proceedings}, editor = {Fink, Christian and Brunner, Christoph}, publisher = {TIB Open Publishing}, address = {Hannover}, issn = {2976-2030}, doi = {https://doi.org/10.52825/isec.v1i.1165}, year = {2024}, abstract = {Using the thermal building mass as a thermal storage received increasing attention in research during recent years. Due to the large mass of concrete, it offers a large storage capacity and thus a high potential for flexibility. However, passive heat losses during cool down of a thermally activated building influence room temperature and thus limit its flexibility potential. In this contribution a multi-layer activation concept was investigated which thermally decouples the building mass and room air. The study aims to analyse the cool down of a thermally activated building in terms of different charging parameters while considering other heat sources such as solar gains. A dynamic building simulation of a demonstration building was set-up and compared to simulative studies from literature to proof the validity of its dynamic behaviour. In the simulation model the room temperature could be kept above 19 °C between 100 - 190 h. However, when charging the building structure quickly, room temperatures above 24 °C are reached easily. Considering other heat sources such as solar gains, advanced control algorithms are required for efficient operation of the heating system.}, language = {en} } @article{ReumSchmittSummetal.2024, author = {Reum, Tobias and Schmitt, David and Summ, Thorsten and Trinkl, Christoph and Ochs, Fabian and Schrag, Tobias}, title = {Experimental analysis of parallel operation of two heat sources in a dual-source heat pump incorporating two compressors}, volume = {2025}, journal = {International Journal of Refrigeration}, number = {171}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1879-2081}, doi = {https://doi.org/10.1016/j.ijrefrig.2024.12.013}, pages = {124 -- 138}, year = {2024}, abstract = {Dual-source heat pumps have the potential to improve heating efficiency and / or the space required for heat sources. Parallel operation of two heat sources using two compressors can increase these benefits but poses technological challenges - specifically in the increased refrigerant cycle interconnection complexity, refrigerant and compressor oil management. These benefits and challenges have yet to be thoroughly investigated which is the primary objective of this research paper. An experimental analysis was conducted on a dual-source heat pump that utilized both an air heat source and a ground heat source. It included both individual and parallel operation modes of the heat sources. A prototype with a novel two-compressor interconnection was designed, manufactured, and tested in laboratory conditions. Analysis of the energetic benefit included efficiency evaluation at different ambient conditions and the corresponding loads on the ground source heat exchanger. Energetically, the single source operation showed comparable results in the coefficient of performance to conventional heat pumps despite the increased interconnection complexity. Parallel operation could efficiently cover heating loads at reduced load on the individual heat sources (at -7 °C, a reduction to 41 \% on the ground-source and 58 \% on the air-source heat exchanger). Technological challenges were highlighted in refrigerant and compressor oil shifts. While a control-based solution for the refrigerant shift was demonstrated, the oil shift requires further analysis of oil conditions in failing compressors.}, language = {en} } @article{MehtaZoerner2025, author = {Mehta, Kedar and Z{\"o}rner, Wilfried}, title = {Optimizing Agri-PV System: Systematic Methodology to Assess Key Design Parameters}, volume = {18}, pages = {3877}, journal = {Energies}, number = {14}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en18143877}, year = {2025}, abstract = {Agrivoltaic (Agri-PV) systems face the critical challenge of balancing photovoltaic energy generation with crop productivity, yet systematic approaches to quantifying the trade-offs between these objectives remain scarce. In this study, we identify nine essential design indicators: panel tilt angle, elevation, photovoltaic coverage ratio, shading factor, land equivalent ratio, photosynthetically active radiation (PAR) utilization, crop yield stability index, water use efficiency, and return on investment. We introduce a novel dual matrix Analytic Hierarchy Process (AHP) to evaluate their relative significance. An international panel of eighteen Agri-PV experts, encompassing academia, industry, and policy, provided pairwise comparisons of these indicators under two objectives: maximizing annual energy yield and sustaining crop output. The high consistency observed in expert responses allowed for the derivation of normalized weight vectors, which form the basis of two Weighted Influence Matrices. Analysis of Total Weighted Influence scores from these matrices reveal distinct priority sets: panel tilt, coverage ratio, and elevation are most influential for energy optimization, while PAR utilization, yield stability, and elevation are prioritized for crop productivity. This methodology translates qualitative expert knowledge into quantitative, actionable guidance, clearly delineating both synergies, such as the mutual benefit of increased elevation for energy and crop outcomes, and trade-offs, exemplified by the negative impact of high photovoltaic coverage on crop yield despite gains in energy output. By offering a transparent, expert-driven decision-support tool, this framework enables practitioners to customize Agri-PV system configurations according to local climatic, agronomic, and economic contexts. Ultimately, this approach advances the optimization of the food energy nexus and supports integrated sustainability outcomes in Agri-PV deployment.}, language = {en} } @article{MehtaWrightBrownetal.2025, author = {Mehta, Kedar and Wright, Andrew and Brown, Neil and Z{\"o}rner, Wilfried}, title = {Transitioning to Low-Carbon Heating: Decision-Making Approach for Cold Communities}, volume = {9}, pages = {zkaf010}, journal = {Clean Energy}, number = {4}, publisher = {Oxford University Press}, address = {Oxford}, issn = {2515-396X}, doi = {https://doi.org/10.1093/ce/zkaf010}, year = {2025}, abstract = {Selecting a sustainable heat energy supply system for high-altitude, cold-climatic communities in developing countries is essential for both decision-makers and the scientific community. However, no comprehensive guide or framework exists to address this issue and decarbonize cold communities sustainably. This research aims to fill that gap by identifying and developing a methodology for selecting a suitable heat energy supply system, using Kyrgyzstan as a case study. The approach takes into account renewable energy sources, local conditions, and specific criteria necessary for designing a sustainable energy supply. The paper introduces a decision-making framework based on 17 criteria, covering geographical, environmental, economic, technical, and social aspects, derived from the opinions of over 20 experts. This framework serves as a guide for selecting and designing an appropriate heat energy supply system. Five heat supply options are analyzed in Kyrgyzstan's high-altitude, cold rural setting to demonstrate the framework's potential. The analysis reveals that centralized district heating is the most suitable solution, scoring 79\% for system selection. This methodology is partially or fully transferable to regions or countries with similar climates and local circumstances, offering a valuable resource for the development of sustainable heat energy solutions in cold, high-altitude communities.}, language = {en} } @inproceedings{BlasiFernandesNavarroGeversetal.2019, author = {Blasi, Tha{\´i}s M. and Fernandes, Thelma S. P. and Navarro Gevers, Daniel and Aoki, Alexandre Rasi and Impinnisi, Patricio and da S. Pinto, Cleverson L. and da V. Damasceno, Patricia M. R.}, title = {Evaluation of the impacts of renewables sources and battery systems in distribution feeders with different penetration levels}, booktitle = {2019 IEEE PES Innovative Smart Grid Technologies Conference - Latin America (ISGT Latin America)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-5386-8218-0}, doi = {https://doi.org/10.1109/ISGT-LA.2019.8895349}, year = {2019}, language = {en} } @inproceedings{BeringerMehtaEhrenwirthetal.2021, author = {Beringer, Jakob and Mehta, Kedar and Ehrenwirth, Mathias and Z{\"o}rner, Wilfried}, title = {Sustainable materials for insulating high-altitude rural Kyrgyz residential houses: A parametric economic study}, booktitle = {Applied Research Conference 2021, Conference Proceedings}, editor = {S{\"o}llner, Matthias and Pirkl, Gerald}, publisher = {Ostbayerische Technische Hochschule Amberg-Weiden}, address = {Amberg}, url = {https://www.oth-aw.de/files/oth-aw/Aktuelles/Veroeffentlichungen/Applied_Research_Conference_ARC2021_Proceedings.pdf}, pages = {183 -- 188}, year = {2021}, language = {en} } @inproceedings{KnepperEhrenwirthZoerner2021, author = {Knepper, Karoline and Ehrenwirth, Mathias and Z{\"o}rner, Wilfried}, title = {Potential of e- mobility in rural areas - Evaluation of opportunities and barriers based on literature review}, booktitle = {Applied Research Conference 2021, Conference Proceedings}, editor = {S{\"o}llner, Matthias and Pirkl, Gerald}, publisher = {Ostbayerische Technische Hochschule Amberg-Weiden}, address = {Amberg}, url = {https://www.oth-aw.de/files/oth-aw/Aktuelles/Veroeffentlichungen/Applied_Research_Conference_ARC2021_Proceedings.pdf}, pages = {216 -- 220}, year = {2021}, language = {en} } @inproceedings{RiedmaierBaerZoerner2021, author = {Riedmaier, Thomas and B{\"a}r, Katharina and Z{\"o}rner, Wilfried}, title = {Comparison of different calculation methods for the outflow from pressurized vessels}, booktitle = {Applied Research Conference 2021, Conference Proceedings}, editor = {S{\"o}llner, Matthias and Pirkl, Gerald}, publisher = {Ostbayerische Technische Hochschule Amberg-Weiden}, address = {Amberg}, url = {https://www.oth-aw.de/files/oth-aw/Aktuelles/Veroeffentlichungen/Applied_Research_Conference_ARC2021_Proceedings.pdf}, pages = {258 -- 263}, year = {2021}, language = {en} } @inproceedings{BugajeYadavMehtaetal.2021, author = {Bugaje, Aminu and Yadav, Akhilesh and Mehta, Kedar and Ojinji, Felicia and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {Influence of input parameters on artificial neural networks for off-grid solar photovoltaic power forecasting}, booktitle = {NEIS 2021}, editor = {Schulz, Detlef}, publisher = {VDE Verlag}, address = {Berlin}, isbn = {978-3-8007-5651-3}, url = {https://www.vde-verlag.de/proceedings-en/565651017.html}, pages = {135 -- 141}, year = {2021}, language = {en} } @inproceedings{BugajeEhrenwirthTrinkletal.2020, author = {Bugaje, Aminu and Ehrenwirth, Mathias and Trinkl, Christoph and B{\"a}r, Katharina and Z{\"o}rner, Wilfried}, title = {Development of a load management algorithm using nonlinear programming (NLP) for optimum integration of electric-mobility solutions into rural off-grid PV systems}, booktitle = {NEIS 2020}, editor = {Schulz, Detlef}, publisher = {VDE Verlag}, address = {Berlin}, isbn = {978-3-8007-5359-8}, url = {https://www.vde-verlag.de/proceedings-en/565359022.html}, pages = {167 -- 172}, year = {2020}, language = {en} } @inproceedings{GroeschVogtSaidietal.2020, author = {Gr{\"o}sch, Norbert and Vogt, Regine and Saidi, Abdessamad and Z{\"o}rner, Wilfried}, title = {Repoweringmaßnahmen hinsichtlich zuk{\"u}nftiger Aufgaben von Biogasanlagen}, booktitle = {Schriftenreihe Umweltingenieurwesen Agrar- und Umweltwissenschaftliche Fakult{\"a}t, Band 95, Tagungsband 14. Rostocker Bioenergieforum / 19. DIALOG Abfallwirtschaft MV}, subtitle = {Ergebnisse aus dem Projekt REzAB}, publisher = {Universit{\"a}t Rostock, Agrar- und Umweltwissenschaftliche Fakult{\"a}t}, address = {Rostock}, isbn = {978-3-86009-507-2}, doi = {https://doi.org/10.18453/rosdok_id00002650}, pages = {133 -- 142}, year = {2020}, language = {de} } @inproceedings{StarkSaidiZoerner2020, author = {Stark, Matthias and Saidi, Abdessamad and Z{\"o}rner, Wilfried}, title = {KomBio-Speicher: Entwicklung eines neuartigen Dampfspeichersystems f{\"u}r ein flexibles Biomasse-Heizkraftwerk zur Erh{\"o}hung der Systemstabilit{\"a}t}, booktitle = {Schriftenreihe Umweltingenieurwesen Agrar- und Umweltwissenschaftliche Fakult{\"a}t, Band 95, Tagungsband 14. Rostocker Bioenergieforum / 19. DIALOG Abfallwirtschaft MV}, publisher = {Universit{\"a}t Rostock}, address = {Rostock}, isbn = {978-3-86009-507-2}, doi = {https://doi.org/10.18453/rosdok_id00002650}, pages = {345 -- 354}, year = {2020}, language = {de} } @inproceedings{WagenederGroeschSaidietal.2020, author = {Wageneder, Stefanie and Gr{\"o}sch, Norbert and Saidi, Abdessamad and Wagner, Robert and Gl{\"o}tzl, Melanie and Gleich, Jasmin and Hermann, Christiane and Mielke, Sophie and Freydank, Christian and Z{\"o}rner, Wilfried}, title = {L{\"o}sungsans{\"a}tze zur technischen Anpassung bestehender Biogasanlagen f{\"u}r die Nutzung faseriger Reststoffe}, booktitle = {Schriftenreihe Umweltingenieurwesen Agrar- und Umweltwissenschaftliche Fakult{\"a}t, Band 95, Tagungsband 14. Rostocker Bioenergieforum / 19. DIALOG Abfallwirtschaft MV}, subtitle = {Auswahl der zu untersuchenden Anlagen im Rahmen des Projekts „LaRA"}, publisher = {Universit{\"a}t Rostock, Agrar- und Umweltwissenschaftliche Fakult{\"a}t}, address = {Rostock}, isbn = {978-3-86009-507-2}, doi = {https://doi.org/10.18453/rosdok_id00002650}, pages = {409 -- 414}, year = {2020}, language = {de} } @inproceedings{MehtaEhrenwirthTrinkletal.2020, author = {Mehta, Kedar and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {A parametric study on the feasibility of solar-thermal space heating and hot water preparation under cold climates in Central Asian rural areas}, booktitle = {EuroSun 2020 Proceedings}, publisher = {International Solar Energy Society}, address = {Freiburg}, doi = {https://dx.doi.org/10.18086/eurosun.2020.04.03}, year = {2020}, language = {en} } @inproceedings{MehtaEhrenwirthTrinkletal.2020, author = {Mehta, Kedar and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {Impact of locally available thermal insulation structures on space heating demand of high-altitude rural buildings}, booktitle = {EuroSun 2020 Proceedings}, subtitle = {a case study of Kyrgyzstan}, publisher = {International Solar Energy Society}, address = {Freiburg}, doi = {https://dx.doi.org/10.18086/eurosun.2020.04.04}, year = {2020}, language = {en} } @inproceedings{YadavSinhaSaidietal.2020, author = {Yadav, Akhilesh and Sinha, Anuj and Saidi, Abdessamad and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {NILM based energy disaggregation algorithm for dairy farms}, booktitle = {NILM'20: Proceedings of the 5th International Workshop on Non-Intrusive Load Monitoring}, publisher = {ACM}, address = {New York}, isbn = {978-1-4503-8191-8}, doi = {https://doi.org/10.1145/3427771.3427846}, pages = {16 -- 19}, year = {2020}, language = {en} } @article{BaerSaidiHackletal.2019, author = {B{\"a}r, Katharina and Saidi, Abdessamad and Hackl, Christoph and Z{\"o}rner, Wilfried}, title = {Combined operation of photovoltaic and biogas plants for optimal transformer loading}, volume = {2019}, journal = {Chemical Engineering Transactions}, number = {76}, publisher = {AIDIC The Italian Association of Chemical Engineering}, address = {Milano}, issn = {2283-9216}, doi = {https://doi.org/10.3303/CET1976101}, pages = {601 -- 606}, year = {2019}, language = {en} } @article{StarkContiSaidietal.2019, author = {Stark, Matthias and Conti, Fosca and Saidi, Abdessamad and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {Steam storage systems for flexible biomass CHP plants}, volume = {2019}, pages = {105321}, journal = {Biomass and Bioenergy}, subtitle = {evaluation and initial model based calculation}, number = {128}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0961-9534}, doi = {https://doi.org/10.1016/j.biombioe.2019.105321}, year = {2019}, language = {en} } @article{StarkPhilippSaidietal.2019, author = {Stark, Matthias and Philipp, Matthias and Saidi, Abdessamad and Trinkl, Christoph and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {Design parameters of steam accumulators for the utilization in industrial solid biomass-fuelled CHP plants}, volume = {2019}, journal = {Chemical Engineering Transactions}, number = {76}, publisher = {AIDIC The Italian Association of Chemical Engineering}, address = {Milano}, issn = {2283-9216}, doi = {https://doi.org/10.3303/CET1976137}, pages = {817 -- 822}, year = {2019}, language = {en} } @article{WernerEhrenwirthMuschiketal.2021, author = {Werner, Melanie and Ehrenwirth, Mathias and Muschik, Sebastian and Trinkl, Christoph and Schrag, Tobias}, title = {Operational experiences with a temperature-variable district heating network for a rural community}, volume = {46}, journal = {Chemical Engineering \& Technology}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0930-7516}, doi = {https://doi.org/10.1002/ceat.202100114}, pages = {482 -- 490}, year = {2021}, abstract = {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.}, language = {en} } @inproceedings{LauermannBetzMehtaetal.2020, author = {Lauermann, Magdalena and Betz, Florian and Mehta, Kedar and Thevs, Niels and Ehrenwirth, Mathias and Z{\"o}rner, Wilfried and Cyffka, Bernd}, title = {Preservation of Selected Ecosystem Services in the Floodplains of the Naryn River (Kyrgyzstan): Introducing the {\"O}koFlussPlan Project}, booktitle = {Beitr{\"a}ge zum 50. und 51. Jahrestreffen des Arbeitskreises Hydrologie 2018 in Koblenz und 2019 in Heidelberg}, publisher = {Institut f{\"u}r Geographie, Universit{\"a}t Augsburg}, address = {Augsburg}, url = {https://www.uni-augsburg.de/de/fakultaet/fai/geo/forschung/geographicaaugustana/}, pages = {47 -- 53}, year = {2020}, language = {en} } @inproceedings{RammEhrenwirthSchrag2019, author = {Ramm, Tobias and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Modelling of the central heating station within a district heating system with variable temperatures}, booktitle = {Proceedings of the 13th International Modelica Conference}, editor = {Haumer, Anton}, publisher = {Modelica Association and Link{\"o}ping University Electronic Press}, address = {Link{\"o}ping}, isbn = {978-91-7685-122-7}, issn = {1650-3686}, doi = {http://dx.doi.org/10.3384/ecp19157567}, pages = {567 -- 576}, year = {2019}, language = {en} } @inproceedings{SchragEhrenwirthRammetal.2020, author = {Schrag, Tobias and Ehrenwirth, Mathias and Ramm, Tobias and Vannahme, Anna and Trinkl, Christoph}, title = {Solar energy use in district heating networks}, booktitle = {ICREEC 2019: Proceedings of the 1st International Conference on Renewable Energy and Energy Conversion}, editor = {Belasri, Ahmed and Beldjilali, Sid Ahmed}, publisher = {Springer}, address = {Singapur}, isbn = {978-981-15-5443-8}, issn = {2352-2534}, doi = {https://doi.org/10.1007/978-981-15-5444-5_1}, pages = {3 -- 10}, year = {2020}, language = {en} } @article{SlonskiSchrag2019, author = {Slonski, Matthias and Schrag, Tobias}, title = {Linear optimisation of a settlement towards the energy-plus house standard}, volume = {12}, pages = {210}, journal = {Energies}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en12020210}, year = {2019}, abstract = {Future buildings will use technologies that are either well-known, innovative, or a combination thereof in order to be environmentally friendly and feasible at the same time. To evaluate and compare such systems through simulation, adaptive tools need to be available. This paper describes a conceived method for planning quarters and settlements. The novelty of this work emerges from the combination of a building simulation with a linear economic optimisation of the energy system, to achieve the energy-plus house standard for a settlement. Furthermore, the tools applied are adaptive or open source. In this article, a hypothetical basic example is given for a predefined idealised settlement, which consists of 132 single-family houses of one building type. The hourly demand for electrical energy and heat is established for three energy-efficiency classes for the building type with a dynamic simulation in MATLAB/SIMULINK using the CARNOT toolbox. This toolbox is also used to calculate the specific electrical energy production by photovoltaics. The components for the energy system of the settlement are implemented in the open source linear optimisation tool URBS. An economic optimum for the energy system of the settlement is found for each of the energy efficiency classes for an accumulated energy demand of the buildings. In this way, a lossless energy hub between the buildings is assumed. The results of the conducted simulations indicate that the optimal ratio of air/water to ground/water heat pumps shifts towards air/water heat pumps with more energy efficient houses. This is due to the lower specific investment costs, which outweigh the operational costs when less energy is required. The lowest costs for the entire energy system are for the one with the most energy efficient settlement. This is the case, as the costs for the higher energy standard of the buildings are not considered in the calculations. The behaviour of the optimisation is tested and discussed through a sensitivity analysis for one efficiency class. By presenting this simple, comprehensible example, an impression of the possible applications for this methodology is conveyed.}, language = {en} } @inproceedings{VannahmeRammEhrenwirthetal.2019, author = {Vannahme, Anna and Ramm, Tobias and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Comparison of a usual heat-transfer-station with a hydraulic modified version under the aspect of exergy saving}, booktitle = {Proceedings of the 13th International Modelica Conference}, editor = {Haumer, Anton}, publisher = {Link{\"o}ping University Electronic Press}, address = {Link{\"o}ping}, isbn = {978-91-7685-122-7}, issn = {1650-3686}, doi = {http://dx.doi.org/10.3384/ecp19157647}, pages = {647 -- 654}, year = {2019}, language = {en} } @article{MehtaMingalevaZoerneretal.2022, author = {Mehta, Kedar and Mingaleva, Ekaterina and Z{\"o}rner, Wilfried and Degembaeva, Nadira and Baibagyshov, Ermek}, title = {Comprehensive analysis of the energy legislative framework of Kyrgyzstan}, volume = {2022}, pages = {100013}, journal = {Cleaner Energy Systems}, subtitle = {Investigation to develop a roadmap of Kyrgyz renewable energy sector}, number = {2}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2772-7831}, doi = {https://doi.org/10.1016/j.cles.2022.100013}, year = {2022}, abstract = {Kyrgyzstan - a Central Asian country - faces a high degree of energy insecurity. Especially the Kyrgyz power sector suffers from outdated infrastructure and is not capable of fulfilling the growing and fluctuating inter-seasonal energy demand. On the contrary, the country is endowed with an abundant amount of renewable energies, which can significantly contribute to bringing stability to the energy sector. The current energy policy is considered as one of the key barriers to the developing the renewable energy sector in Kyrgyzstan. Hence, there is an immediate need to evaluate the formulated energy policy to investigate gaps and uncertainties. In response to that, the presented study is the first attempt that provides an in-depth assessment of Kyrgyzstan's current energy legislative framework. It determines the primary mechanisms for the operation and conduction of renewable energy sources in terms of legal and economic aspects. Furthermore, it provides detailed insight into the current Feed-in tariff calculation methodology and scrutinizes the special provisions for private investors. Based on the in-depth assessment, the article recapitulates the shortfall in the existing energy policies. The article found that there is huge potential available for the renewable energy market. To unlock that, the presented article emahsised on synergestic policy making approach to overcome barriers and expand the Kyrgyz renewable energy sector. The article further showcased how the improvements in the regulatory framework would raise the interest of the private investors / local energy players to promote the installation of renewable energy technologies over the county.}, language = {en} } @article{MehtaEhrenwirthTrinkletal.2022, author = {Mehta, Kedar and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {Mapping Potential for Improving Rural Energy Services in Kyrgyzstan: Factors for Achieving Sustainable Development Goals in the Community Context}, volume = {3}, journal = {World}, number = {3}, publisher = {MDPI}, address = {Basel}, issn = {2673-4060}, doi = {https://doi.org/10.3390/world3030032}, pages = {586 -- 606}, year = {2022}, abstract = {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.}, language = {en} } @article{MehtaZoernerGreenough2022, author = {Mehta, Kedar and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {Residential Building Construction Techniques and the Potential for Energy Efficiency in Central Asia: Example from High-Altitude Rural Settlement in Kyrgyzstan}, volume = {15}, pages = {8869}, journal = {Energies}, number = {23}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en15238869}, year = {2022}, abstract = {Building construction in rural Kyrgyzstan is heavily dominated by earthen buildings. Old and inappropriate residential building structures contribute significantly to high domestic space heating energy consumption. Therefore, it is necessary to understand the relevant building construction techniques. However, the scant information on Kyrgyz building techniques, especially for high-altitude rural settlements, was the prime motivation to perform the presented study. The key objective of the study is to investigate residential building construction techniques in high-altitude rural Kyrgyzstan, and this was to be achieved by house visits during field trips, literature review, and pilot interviews with local people. The analysis enabled the detailed identification of individual building envelopes as well as predominant building materials to be recorded. Based on the assessment, a housing profile was created that represents the typical characteristics of traditional rural Kyrgyz houses. Furthermore, the study demonstrates the potential for energy savings in rural Kyrgyz houses of 50-70\%. However, local conditions prevent people from making improvements to all domestic energy efficiency parameters simultaneously. Therefore, the study developed a 'sequential roadmap' to reduce domestic space heating demand in different phases based on simulation studies. Existing low-income rural Kyrgyz habitations can use the presented roadmap to reduce domestic space heating demand sequentially to overcome financial barriers and, therefore, contribute to establishing sustainable buildings in Kyrgyzstan. These results may be partially replicated in other Central Asian rural communities depending on their location and building characteristics.}, language = {en} } @article{StarkTrinklZoerneretal.2018, author = {Stark, Matthias and Trinkl, Christoph and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {Methodological Evaluation of Storage Systems for Flexible Power Generation from Solid Biomass}, volume = {41}, journal = {Chemical Engineering \& Technology}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.201800099}, pages = {2168 -- 2176}, year = {2018}, language = {en} } @article{SelleneitStoecklHolzhammer2020, author = {Selleneit, Volker and St{\"o}ckl, Martin and Holzhammer, Uwe}, title = {System efficiency: methodology for rating of industrial utilities in electricity grids with a high share of variable renewable energies}, volume = {2020}, pages = {109969}, journal = {Renewable and Sustainable Energy Reviews}, subtitle = {a first approach}, number = {130}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1364-0321}, doi = {https://doi.org/10.1016/j.rser.2020.109969}, year = {2020}, language = {en} } @article{SelleneitStoecklPhilippetal.2019, author = {Selleneit, Volker and St{\"o}ckl, Martin and Philipp, Matthias and Mast, Tanja and Holzhammer, Uwe and Schlosser, Florian}, title = {System efficiency rating of industrial utilities in electricity grids with a high share of variable renewable energies}, volume = {2019}, journal = {Chemical Engineering Transactions}, number = {76}, publisher = {AIDIC}, address = {Mailand}, issn = {2283-9216}, doi = {https://doi.org/10.3303/CET1976163}, pages = {973 -- 978}, year = {2019}, language = {en} } @article{StoecklSelleneitPhilippetal.2019, author = {St{\"o}ckl, Martin and Selleneit, Volker and Philipp, Matthias and Holzhammer, Uwe}, title = {An approach to calculate electricity costs for the german industry for a system efficient design by combining energy efficiency and demand response}, volume = {2019}, journal = {Chemical Engineering Transactions}, number = {76}, publisher = {AIDIC}, address = {Mailand}, issn = {2283-9216}, doi = {https://doi.org/10.3303/CET1976191}, pages = {1141 -- 1146}, year = {2019}, language = {en} } @inproceedings{HuemmerMastKolleretal.2020, author = {H{\"u}mmer, Benedikt and Mast, Tanja and Koller, Maria and Holzhammer, Uwe}, title = {Smart Markets in Southern Germany: Key factors for profits of biogas plants}, booktitle = {2020 17th International Conference on the European Energy Market (EEM)}, publisher = {IEEE}, address = {Piscataway}, isbn = {978-1-7281-6919-4}, doi = {https://doi.org/10.1109/EEM49802.2020.9221988}, year = {2020}, language = {en} } @techreport{EltropNagelHolzhammeretal.2020, author = {Eltrop, Ludger and Nagel, Sylvio and Holzhammer, Uwe and Mast, Tanja and Wachinger, Gisela}, title = {Schlussbericht zu Nr. 3.2 Verbundvorhaben „OptiSys"}, doi = {https://doi.org/10.2314/KXP:1738015386}, pages = {126}, year = {2020}, language = {de} } @inproceedings{MastHuemmerHolzhammer2021, author = {Mast, Tanja and H{\"u}mmer, Benedikt and Holzhammer, Uwe}, title = {Erl{\"o}spotential f{\"u}r Biogasanlagen an Smart Markets}, booktitle = {Tagungsunterlagen Zuk{\"u}nftige Stromnetze}, publisher = {Conexio GmbH}, address = {Pforzheim}, isbn = {978-3-948176-12-9}, doi = {https://www.zukunftsnetz.net/konferenz/tagungsbaende}, pages = {224 -- 245}, year = {2021}, language = {de} } @inproceedings{HuemmerMastHolzhammer2021, author = {H{\"u}mmer, Benedikt and Mast, Tanja and Holzhammer, Uwe}, title = {Einflussfaktoren auf das Erl{\"o}spotential von Biogasanlagen in Smart Markets}, booktitle = {Tagungsband 15. Rostocker Bioenergieforum}, editor = {Nelles, Michael}, publisher = {Universit{\"a}t Rostock}, address = {Rostock}, isbn = {978-3-86009-524-9}, doi = {https://doi.org/10.18453/rosdok_id00003024}, pages = {109 -- 118}, year = {2021}, language = {de} } @article{PhilippSchummSchlosseretal.2017, author = {Philipp, Matthias and Schumm, Gregor and Schlosser, Florian and Peesel, Ron-Hendrick and Holzhammer, Uwe}, title = {Grundsatzfragen der Abw{\"a}rmenutzung}, volume = {69}, journal = {BWK - Das Energie-Fachmagazin}, number = {4}, publisher = {VDI Fachmedien}, address = {D{\"u}sseldorf}, issn = {1618-193X}, url = {https://www.ingenieur.de/fachmedien/bwk/energieversorgung/grundsatzfragen-der-abwaermenutzung/}, pages = {36 -- 39}, year = {2017}, language = {de} } @article{BaderBrandmayrTrinkletal.2014, author = {Bader, Tobias and Brandmayr, Sebastian and Trinkl, Christoph and Z{\"o}rner, Wilfried and Hanby, Victor Ian}, title = {Climate Specific Design and Effectiveness of Solar DEC-systems}, volume = {2014}, journal = {Energy Procedia}, subtitle = {a Methodological Zoning Approach}, number = {48}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1876-6102}, doi = {https://doi.org/10.1016/j.egypro.2014.02.090}, pages = {778 -- 789}, year = {2014}, abstract = {The climate specific effectiveness of solar DEC-systems and relevant preferable adaptions of the system design have been so far predominantly analysed based on individual simulation for selected sites. In order to systematically deduce design-specific outline data for the application of the solar DEC-technology at climatically different sites a methodological zoning approach was further developed. A subsequent meteorological analysis for 17 sites mapping the world climate creates a transparent understanding on the activity of the specific system components. This results in a comprehension on the site-specific effectiveness of solar DEC-systems and provides insights on principally relevant and efficient system configurations.}, language = {en} } @article{ReiterBrandmayrTrinkletal.2014, author = {Reiter, Christoph and Brandmayr, Sebastian and Trinkl, Christoph and Z{\"o}rner, Wilfried and Hanby, Victor Ian}, title = {Performance Optimisation of Polymeric Collectors by Means of Dynamic Simulation and Sensitivity Analysis}, volume = {2014}, journal = {Energy Procedia}, number = {48}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1876-6102}, doi = {https://doi.org/10.1016/j.egypro.2014.02.023}, pages = {181 -- 191}, year = {2014}, abstract = {A dynamic flat-plate collector model for parametric sensitivity studies on polymer-based collector designs was developed. Validation using experimental results of conventional flat-plate collectors showed satisfying results especially regarding the calculation of individual part temperatures of a collector. The model was used to predict system efficiency as well as individual part temperatures in order to analyse a polymeric collector approach in comparison to a conventional collector. The simulation results showed that the fractional energy savings of systems with conventional flat-plate collectors cannot be reached with the analysed polymeric collector approach. Also the stagnation temperatures of more efficient approaches are too high for low-cost polymeric materials. The exemplary analysis of annual temperature loads of the backside insulation for different approaches proved the necessity of careful collector design aiming at temperature reduction for all individual collector parts.}, language = {en} } @article{RiessBrandmayrZoerneretal.2014, author = {Riess, Hermann and Brandmayr, Sebastian and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {Analysis of the mechanical behaviour of an all-round fully adhesive supported absorber}, volume = {2014}, journal = {Energy Procedia}, number = {48}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1876-6102}, doi = {https://doi.org/10.1016/j.egypro.2014.02.025}, pages = {201 -- 211}, year = {2014}, abstract = {This paper discusses the mechanical behaviour of an all-round fully adhesive supported absorber. Previous research is discussed and compared to the author's own results collected using both laboratory tests and simulation. The influence of the finite-element approach (i.e. geometrically linear or non-linear) was compared. The thermal deformation of a hyperstatic absorber was investigated. The relationship between thermal expansion and pressure change in a gas-filled collector is discussed.}, language = {en} } @article{MuellerBrandmayrZoerner2014, author = {M{\"u}ller, Holger and Brandmayr, Sebastian and Z{\"o}rner, Wilfried}, title = {Development of an evaluation methodology for the potential of solar-thermal energy use in the food industry}, volume = {214}, journal = {Energy Procedia}, number = {48}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1876-6102}, doi = {https://doi.org/10.1016/j.egypro.2014.02.135}, pages = {1194 -- 1201}, year = {2014}, abstract = {The research project 'Solar Heat in the Liquid Food Industry' (part of the FORETA Research Network) focused on the development and optimisation of low-temperature heating systems for the liquid food industry. Its main objectives are in energy efficiency, waste heat recovery and the feasibility of a solar-thermal process heating system. Based on the particular simulation results the overall solar-thermal potentials for German breweries and dairies were determined. In this connection a literature review indicated that most of the potential studies on solar-thermal energy use in the industry or related to specific industrial sectors are based on the total use of low-temperature heat. In opposition to these results, the available and mainly limited roof area was found to be a more important aspect for the solar-thermal potential. Hence, the development of a methodology for a site- specific analysis was necessary. The interconnection of only a few defined evaluation criteria resulted in a more realistic estimation of the potential for a solar-thermal heat supply.}, language = {en} } @article{HaslerHuberLeindeckeretal.2013, author = {Hasler, Ewald and Huber, Christian and Leindecker, Herbert C. and Schrag, Tobias and Stocker, Emanuel and Wartha, Christian}, title = {Bewertung unterschiedlicher Fassadenkonstruktionen unter Lebenszyklusaspekten mit einer Fallstudie B{\"u}rogeb{\"a}ude}, volume = {35}, journal = {Bauphysik}, number = {4}, publisher = {Ernst \& Sohn}, address = {Berlin}, issn = {1437-0980}, doi = {https://doi.org/10.1002/bapi.201310072}, pages = {250 -- 256}, year = {2013}, language = {de} } @inproceedings{SaidiContiKarletal.2019, author = {Saidi, Abdessamad and Conti, Fosca and Karl, J{\"u}rgen and Goldbrunner, Markus}, title = {Biogastankstelle f{\"u}r die Landwirtschaft - Gegen{\"u}berstellende {\"o}konomische Bewertung unterschiedlicher Verfahren f{\"u}r die dezentrale partielle Biogasaufbereitung}, booktitle = {8. Statuskonferenz Bioenergie Reader}, editor = {Thr{\"a}n, Daniela and Pfeiffer, Diana}, publisher = {DBFZ Deutsches Biomasseforschungszentrum gemeinn{\"u}tzige GmbH}, address = {Leipzig}, isbn = {978-3-946629-27-6}, issn = {2698-6809}, url = {https://www.energetische-biomassenutzung.de/veranstaltungen/statuskonferenzen/8-statuskonferenz/programm}, pages = {78 -- 79}, year = {2019}, language = {de} } @inproceedings{ContiSaidiGoldbrunner2019, author = {Conti, Fosca and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Verbesserung der Durchmischung in Biogasfermentern}, booktitle = {8. Statuskonferenz Bioenergie Reader}, editor = {Thr{\"a}n, Daniela and Pfeiffer, Diana}, publisher = {DBFZ Deutsches Biomasseforschungszentrum gemeinn{\"u}tzige GmbH}, address = {Leipzig}, isbn = {978-3-946629-27-6}, issn = {2698-6809}, url = {https://www.energetische-biomassenutzung.de/veranstaltungen/statuskonferenzen/8-statuskonferenz/programm}, pages = {105}, year = {2019}, language = {de} } @article{WiedemannContiSaidietal.2018, author = {Wiedemann, Leonhard and Conti, Fosca and Saidi, Abdessamad and Sonnleitner, Matthias and Goldbrunner, Markus}, title = {Modeling Mixing in Anaerobic Digesters with Computational Fluid Dynamics Validated by Experiments}, volume = {41}, journal = {Chemical Engineering \& Technology}, number = {11}, publisher = {Wiley}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.201800083}, pages = {2101 -- 2110}, year = {2018}, language = {en} } @inproceedings{ContiWiedemannSaidietal.2018, author = {Conti, Fosca and Wiedemann, Leonhard and Saidi, Abdessamad and Sonnleitner, Matthias and Goldbrunner, Markus}, title = {Mixing of a Model Substrate in a Scale-down Laboratory Digester and Processing with a Computational Fluid Dynamics Model}, booktitle = {EUBCE 2018 Online Conference Proceedings}, publisher = {ETA s.r.l.}, address = {Florenz}, isbn = {978-88-89407-18-9}, issn = {2282-5819}, doi = {https://doi.org/10.5071/26thEUBCE2018-2CV.5.34}, pages = {811 -- 815}, year = {2018}, language = {en} } @article{ContiWiedemannSonnleitneretal.2018, author = {Conti, Fosca and Wiedemann, Leonhard and Sonnleitner, Matthias and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Monitoring the mixing of an artificial model substrate in a scale-down laboratory digester}, volume = {2019}, journal = {Renewable Energy}, number = {132}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0960-1481}, doi = {https://doi.org/10.1016/j.renene.2018.08.013}, pages = {351 -- 362}, year = {2018}, language = {en} } @article{SaidiTrinklContietal.2018, author = {Saidi, Abdessamad and Trinkl, Christoph and Conti, Fosca and Goldbrunner, Markus and Karl, J{\"u}rgen}, title = {Partially Upgraded Biogas: Potential forDecentralized Utilization in AgriculturalMachinery}, volume = {41}, journal = {Chemical Engineering \& Technology}, number = {11}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.201800100}, pages = {2111 -- 2119}, year = {2018}, language = {en} } @article{MehtaEhrenwirthTrinkletal.2022, author = {Mehta, Kedar and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {Towards Sustainable Community Development through Renewable Energies in Kyrgyzstan: A Detailed Assessment and Outlook}, volume = {3}, journal = {World}, number = {2}, publisher = {MDPI}, address = {Basel}, issn = {2673-4060}, doi = {https://doi.org/10.3390/world3020018}, pages = {327 -- 343}, year = {2022}, abstract = {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.}, language = {en} } @article{WernerMuschikEhrenwirthetal.2022, author = {Werner, Melanie and Muschik, Sebastian and Ehrenwirth, Mathias and Trinkl, Christoph and Schrag, Tobias}, title = {Sector Coupling Potential of a District Heating Network by Consideration of Residual Load and CO2 Emissions}, volume = {15}, pages = {6281}, journal = {Energies}, number = {17}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en15176281}, year = {2022}, abstract = {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, Eichst{\"a}tt, 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.}, language = {en} } @article{ContiWiedemannSonnleitneretal.2017, author = {Conti, Fosca and Wiedemann, Leonhard and Sonnleitner, Matthias and Goldbrunner, Markus}, title = {Thermal behaviour of viscosity of aqueous cellulose solutions to emulate biomass in anaerobic digesters}, volume = {42}, journal = {New Journal of Chemistry}, number = {2}, publisher = {RSC}, address = {London}, issn = {1369-9261}, doi = {https://doi.org/10.1039/C7NJ03199H}, pages = {1099 -- 1104}, year = {2017}, language = {en} } @article{SaidiContiSonnleitneretal.2018, author = {Saidi, Abdessamad and Conti, Fosca and Sonnleitner, Matthias and Goldbrunner, Markus}, title = {Membrane separation process for small scaled partial biogas upgrading}, volume = {2018}, pages = {012012}, journal = {IOP Conference Series: Materials Science and Engineering}, number = {446}, publisher = {IOP Publishing}, address = {London}, issn = {1757-899X}, doi = {https://doi.org/10.1088/1757-899X/446/1/012012}, year = {2018}, abstract = {Biogas upgrading is actually limited to the production of biomethane as natural gas substitute. To realize the according gas quality a cost intensive methane enrichment is required, wherefore biogas upgrading is actually merely cost-efficient in case of high production rates. Since the energy and cost effort disproportionately increases with the required product gas purity partial biogas upgrading for decentralized utilization represents a promising utilization approach for farm based applications. Among the available technologies for CO2-separation the gas permeable membrane has high potential for small scaled biogas upgrading. Within the present study a model based analysis to determine the savings potential of a membrane based upgrading system is performed.}, language = {en} } @article{ContiWiedemannSaidietal.2018, author = {Conti, Fosca and Wiedemann, Leonhard and Saidi, Abdessamad and Goldbrunner, Markus}, title = {Effect of mixing of waste biomass in anaerobic digesters for production of biogas}, volume = {2018}, pages = {012011}, journal = {IOP Conference Series: Materials Science and Engineering}, number = {446}, publisher = {IOP Publishing}, address = {London}, issn = {1757-899X}, doi = {https://doi.org/10.1088/1757-899X/446/1/012011}, year = {2018}, abstract = {Biogas technology is an important renewable bioenergy producer. The biogas generating process needs to be optimized to minimise the energy consumption due to the stirring of biomass slurry. Numerical simulations and laboratory experiments are economically and practically preferred over investigations of industrial scale biogas plants. Additionally, a strategic approach to model the reality in scientific laboratories is to use a rheological valid artificial chemical substrate to replace real biomass. The proposes of this study were (i) to investigate the mixing process in a 1:12 scaled-down home-made laboratory digester filled with a 0.3 wt\% water-cellulose solution, (ii) to simulate the mixing process in the laboratory-scale digester using a computational fluid dynamics model, (iii) to validate the model by comparison of the simulation with laboratory experiments results obtained on the laboratory digester. Optical and acoustic measurements on the flow velocity inside the digester during the mixing process of the water-cellulose solutions indicate that the model based on computational fluid dynamics is valid. The data are presented and discussed in the paper.}, language = {en} } @article{MastHuemmerHolzhammeretal.2022, author = {Mast, Tanja and H{\"u}mmer, Benedikt and Holzhammer, Uwe and Grimm, Veronika and Hilpert, Johannes and Egerer, Jonas and Lang, Lukas Maximilian and Nysten, Jana and Pfefferer, Ulrike}, title = {Das Smart Market-Konzept als marktbasiertes Element im deutschen Engpassmanagement}, volume = {72}, journal = {et - Energiewirtschaftliche Tagesfragen}, number = {4}, publisher = {VDE Verlag}, address = {Berlin}, issn = {0013-743X}, pages = {53 -- 56}, year = {2022}, language = {de} } @article{FlachContiBayraktaretal.2022, author = {Flach, Charley and Conti, Fosca and Bayraktar, Ahmet and Goldbrunner, Markus}, title = {Direct Methanation and Storage Concepts for the Flexibilization of Biogas Plants}, volume = {46}, journal = {Chemical Engineering \& Technology}, number = {3}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1521-4125}, doi = {https://doi.org/10.1002/ceat.202200239}, pages = {579 -- 586}, year = {2022}, abstract = {Enrichment of the methane fraction in a biogas mixture is an innovative possibility to make existing biogas plants more flexible by using excess power. In the described concept, the CO2 in the biogas is directly catalytically converted into CH4 with H2. The CH4-enriched biogas is again fed into the digester to save energy for later use in the combined heat-and-power unit. Additionally, the fed heat gas can mix and heat the substrate. A heat pipe injector system was therefore developed for cooling the hot biogas stream after methanation and to prevent damage to the microbial consortia during the biomass mixing. The concept was proven at a laboratory-scale biogas plant.}, language = {en} } @article{BottEhrenwirthTrinkletal.2022, author = {Bott, Christoph and Ehrenwirth, Mathias and Trinkl, Christoph and Bayer, Peter}, title = {Component-based modeling of ground-coupled seasonal thermal energy storages}, volume = {2022}, pages = {118810}, journal = {Applied Thermal Engineering}, number = {214}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-5606}, doi = {https://doi.org/10.1016/j.applthermaleng.2022.118810}, year = {2022}, abstract = {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.}, language = {en} } @article{ZoernerMahomedZuluetal.2020, author = {Z{\"o}rner, Wilfried and Mahomed, Nawaz and Zulu, Ackim and Bader, Tobias and Tenthani, Chifundo and Cuamba, Boaventura and Chingosho, Hilton}, title = {Meta-profile and competencies for harmonisation of higher education in sector-specific technology areas: A case study of Renewable Energy in Southern Africa}, volume = {8}, journal = {Tuning Journal for Higher Education}, number = {1}, publisher = {University of Deusto}, address = {Bilbao}, issn = {2386-3137}, doi = {https://doi.org/10.18543/tjhe-8(1)-2020pp75-97}, pages = {75 -- 97}, year = {2020}, language = {en} } @article{AhmedContiBayeretal.2022, author = {Ahmed, Arslan and Conti, Fosca and Bayer, Peter and Goldbrunner, Markus}, title = {Hydronic Road-Heating Systems}, volume = {26}, journal = {Environmental and Climate Technologies}, subtitle = {Environmental Performance and the Case of Ingolstadt Ramps}, number = {1}, publisher = {De Gruyter Poland}, address = {Warsaw}, issn = {2255-8837}, doi = {https://doi.org/10.2478/rtuect-2022-0078}, pages = {1044 -- 1054}, year = {2022}, abstract = {Snowfall and ice formation on road surface significantly impact the safety of driving conditions. To resolve this, every year salt and de-icing chemicals are sprinkled on roads. However, use of salts and snow ploughing have environmental as well as economical disadvantages. To resolve these problems, hydronic road heating systems are valid alternatives. Heat transfer fluid, i.e. mixture of ethanol and water, is pumped into a tubular circulation system under the asphalt. By this technology, the road and pavements shall stay ice-free even in times of snowfall and temperatures below the freezing point. The system can also be used to cool the asphalt in case of extreme heat, which - besides the heating effect - could also prevent road from damages in extreme summers. This study aims to compare the environmental impact of use of salts and road-heating system in terms of GHG emissions. To assess the environmental impact, an operational road heating system for a ramp in Ingolstadt, Germany, is considered. A cradle-to-grave analysis technique is used to determine the environmental effects based on a life-cycle assessment (LCA) framework. The analysis includes nine components solemnly responsible for hydronic heating of asphalt surface such as local heating pipe, insulation, pumps, and heat meters. Comparison is performed in terms of relative and total impact over 50-year lifetime of three heated ramps having 1989 m2 surface area in total. The results show that the asphalt and heating-circuit causes the major fraction (65 \%) of overall GHG emissions, with total life-time emissions of 28.10 kg CO2 eq./m2 of heated surface. During an operational life of 50 years, road heating systems emit 18 \% less CO2 eq./m2 as compared to the use of salts.}, language = {en} } @article{VannahmeBuschEhrenwirthetal.2023, author = {Vannahme, Anna and Busch, Jonas and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Experimental Study of District Heating Substations in a Hardware-in-the-Loop Test Rig}, volume = {12}, pages = {43}, journal = {Resources}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2079-9276}, doi = {https://doi.org/10.3390/resources12040043}, year = {2023}, abstract = {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.}, language = {en} } @article{IgiligiVielhauerEhrenwirthetal.2023, author = {Igiligi, Anthony and Vielhauer, Armin and Ehrenwirth, Mathias and Hurm, Christian and Summ, Thorsten and Trinkl, Christoph and Navarro Gevers, Daniel}, title = {Assessment of Conservation Voltage Reduction in Distribution Networks with Voltage Regulating Distribution Transformers}, volume = {16}, pages = {3155}, journal = {Energies}, number = {7}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en16073155}, year = {2023}, abstract = {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.}, language = {en} } @article{SummEhrenwirthTrinkletal.2023, author = {Summ, Thorsten and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried and Pischow, Kaj and Greenough, Richard and Oyinlola, Muyiwa}, title = {Effect of argon concentration on thermal efficiency of gas-filled insulating glass flat-plate collectors}, volume = {2023}, pages = {120657}, journal = {Applied Thermal Engineering}, number = {230, Part A}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-5606}, doi = {https://doi.org/10.1016/j.applthermaleng.2023.120657}, year = {2023}, abstract = {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.}, language = {en} } @article{BesnerMehtaZoerner2023, author = {Besner, Rebekka and Mehta, Kedar and Z{\"o}rner, Wilfried}, title = {How to Enhance Energy Services in Informal Settlements?}, volume = {16}, pages = {4687}, journal = {Energies}, subtitle = {Qualitative Comparison of Renewable Energy Solutions}, number = {12}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en16124687}, year = {2023}, abstract = {More than half of the urban population of Sub-Saharan Africa lives in informal housing conditions. While urban areas are, in general, characterized by a high electrification rate, residents of informal settlements are still affected by energy poverty, the use of traditional energy sources and unreliable electricity supply. The aim of the study is to give an overview of different renewable-energybased solutions which are able to improve local energy provision. These are Solar Home Systems, Mini-Grids, and Energy-Hubs. The technologies are compared to another option for improving energy supply, namely Grid Expansion. The analysis is based on 24 Key Performance Indicators, which can be classified into technical, economic, environmental, social, and political dimensions. The selection of indicators is based on the challenges prevalent in informal settlements that impede a comprehensive, sustainable energy supply. The literature-based indices are used to determine which of the four technologies is a suitable solution for minimizing the challenges prevailing in informal settlements. The resulting matrix provides a holistic comparison and serves as a decision aid in selecting the appropriate technology for future projects in informal settlements, depending on local conditions and the needs of the population. The results show that the Energy-Hub is a valid alternative for energy supply improvement in Informal Settlements.}, language = {en} } @article{SelleneitMastHolzhammer2020, author = {Selleneit, Volker and Mast, Tanja and Holzhammer, Uwe}, title = {Method to describe and rate the ability to provide flexibility of residual power providers in electricity grids with a high share of variable renewable energies}, volume = {2020}, journal = {CIRED - Open Access Proceedings Journal}, number = {1}, publisher = {IET}, address = {Stevenage}, issn = {2515-0855}, doi = {https://doi.org/10.1049/oap-cired.2021.0294}, pages = {154 -- 157}, year = {2020}, abstract = {With an increasing ratio of variable renewable energies in Germany, power supply has to be ensured by providing flexibility from controllable supply and demand energy conversion units. For residual electricity supply, utilities in the industrial sector or flexible biogas plants may be suitable flexibility options. To describe and rate different technologies or utilities in terms of their ability to provide flexibility, a definition of flexibility and an innovative method to describe flexibility considering the grid requirements is elaborated. The method is based on a solid definition of flexibility indicators suitable for all technologies. For an increased flexibility, in many cases, it is reasonable to add supporting technologies like a storage to a utility or biogas combined heat and power (CHP). Such utility configurations can also be described with the elaborated method. The method can also make a valuable contribution to all distribution systems or utility system modellers as it can be taken as a basis for the modelling. In this study, the definition of flexibility indicators is described in detail and used on the example of a biogas CHP plant.}, language = {en} } @book{EltropNagelHolzhammeretal.2021, author = {Eltrop, Ludger and Nagel, Sylvio and Holzhammer, Uwe and Mast, Tanja and Selleneit, Volker and Tronnier, Annika and Wachinger, Gisela}, title = {Methodenhandbuch "Bioenergie als Flexibilit{\"a}tsoption im Energiesystem"}, series = {Schriftenreihe "Energetische Biomassenutzung", Band 21}, editor = {Eltrop, Ludger and Holzhammer, Uwe}, publisher = {Deutsches Biomasseforschungszentrum gemeinn{\"u}tzige GmbH}, address = {Leipzig}, issn = {2701-2719}, doi = {https://doi.org/10.48480/m6ak-zr53}, pages = {207}, year = {2021}, language = {de} } @inbook{DotzauerBuechnerEltropetal.2021, author = {Dotzauer, Martin and B{\"u}chner, Daniel and Eltrop, Ludger and H{\"a}rdtlein, Marlies and Henning, Christiane and Herrmann, Andr{\´e} and Holzhammer, Uwe and Kornatz, Peter and Mast, Tanja and Nagel, Sylvio and Oehmichen, Katja and Philipp, Matthias and Pohl, Marcel and Selleneit, Volker and Thr{\"a}n, Daniela}, title = {Flexible Bereitstellung von Bioenergie}, booktitle = {Methodenhandbuch: Stoffstromorientierte Bilanzierung der Klimagaseffekte: Methoden zur Bestimmung von Technologiekennwerten, Gestehungskosten und Klimagaseffekten von Vorhaben im Rahmen des BMWi-Forschungsnetzwerkes Bioenergie/ BMWi-F{\"o}rderbereich „Energetische Biomassenutzung"}, editor = {Thr{\"a}n, Daniela and Pfeiffer, Diana}, edition = {Version 5}, publisher = {Deutsches Biomasseforschungszentrum gemeinn{\"u}tzige GmbH}, address = {Leipzig}, isbn = {978-3-946629-58-0}, doi = {https://doi.org/10.48480/ddpt-ys74}, pages = {56 -- 108}, year = {2021}, language = {de} } @inproceedings{MastHolzhammerPhilipp2018, author = {Mast, Tanja and Holzhammer, Uwe and Philipp, Matthias}, title = {SmartBio : Biogasanlagen als Akteur in neuen intelligenten, regionalen M{\"a}rkten}, booktitle = {Tagungsband 12. Rostocker Bioenergieforum 2018}, editor = {Nelles, Michael}, publisher = {Universit{\"a}t Rostock}, address = {Rostock}, isbn = {978-3-86009-473-0}, url = {https://www.openagrar.de/receive/dimport_mods_00001878}, pages = {143 -- 150}, year = {2018}, language = {de} } @inproceedings{MastNagelHolzhammeretal.2020, author = {Mast, Tanja and Nagel, Sylvio and Holzhammer, Uwe and Eltrop, Ludger}, title = {Biogasanlagen neu denken}, booktitle = {Tagungsband 14. Rostocker Bioenergieforum 2020, 19. Dialog Abfallwirtschaft MV}, subtitle = {technisch-{\"o}konomische Charakterisierung f{\"u}r die Einbindung in die modellgest{\"u}tzte Systemanalyse}, publisher = {Universit{\"a}t Rostock}, address = {Rostock}, isbn = {978-3-86009-507-2}, doi = {https://doi.org/10.18453/rosdok_id00002650}, pages = {123 -- 132}, year = {2020}, language = {de} } @inproceedings{NagelMastHolzhammeretal.2020, author = {Nagel, Sylvio and Mast, Tanja and Holzhammer, Uwe and Eltrop, Ludger}, title = {Die Rolle der Bioenergie im Energie- und Mobilit{\"a}tssystem in Deutschland}, booktitle = {Tagungsband 14. Rostocker Bioenergieforum 2020, 19. Dialog Abfallwirtschaft MV}, subtitle = {Ergebnisse einer modellgest{\"u}tzten Systemanalyse}, publisher = {Universit{\"a}t Rostock}, address = {Rostock}, isbn = {978-3-86009- 507-2}, doi = {https://doi.org/10.18453/rosdok_id00002650}, pages = {47 -- 56}, year = {2020}, language = {de} } @inproceedings{MastKollerHolzhammer2020, author = {Mast, Tanja and Koller, Maria and Holzhammer, Uwe}, title = {Verf{\"u}gbarkeit und Erl{\"o}sm{\"o}glichkeiten unterschiedlicher Biogasanlagenkonzepte im Smart-Market-Ansatz}, booktitle = {Tagungsband 14. Rostocker Bioenergieforum 2020, 19. Dialog Abfallwirtschaft MV}, publisher = {Universit{\"a}t Rostock}, address = {Rostock}, isbn = {978-3-86009- 507-2}, doi = {https://doi.org/10.18453/rosdok_id00002650}, pages = {391 -- 397}, year = {2020}, language = {de} } @article{ElMakroumKhallaayounLghouletal.2023, author = {El Makroum, Reda and Khallaayoun, Ahmed and Lghoul, Rachid and Mehta, Kedar and Z{\"o}rner, Wilfried}, title = {Home Energy Management System Based on Genetic Algorithm for Load Scheduling: A Case Study Based on Real Life Consumption Data}, volume = {16}, pages = {2698}, journal = {Energies}, number = {6}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en16062698}, year = {2023}, abstract = {This paper proposes a home energy management system able to achieve optimized load scheduling for the operation of appliances within a given household. The system, based on the genetic algorithm, provides recommendations for the user to improve the way the energy needs of the home are handled. These recommendations not only take into account the dynamic pricing of electricity, but also the optimization for solar energy usage as well as user comfort. Historical data regarding the times at which the appliances have been used is leveraged through a statistical method to integrate the user's preference into the algorithm. Based on real life appliance consumption data collected from a household in Morocco, three scenarios are established to assess the performance of the proposed system with each scenario having different parameters. Running the scenarios on the developed MATLAB script shows a cost saving of up to 63.48\% as compared to a base scenario for a specific day. These results demonstrate that significant cost saving can be achieved while maintaining user comfort. The addition of supplementary shiftable loads (i.e., an electric vehicle) to the household as well as the limitations of such home energy management systems are discussed. The main contribution of this paper is the real data and including the user comfort as a metric in in the home energy management scheme.}, language = {en} } @article{KaminskiKuesterDanielAokietal.2023, author = {Kaminski K{\"u}ster, Kristie and Daniel, Gebbran and Aoki, Alexandre Rasi and Lambert-Torres, Germano and Navarro Gevers, Daniel and Impinnisi, Patricio and da Silva Pinto, Cleverson Luiz}, title = {Adoption of Local Peer-to-Peer Energy Markets: Technical and Economical Perspectives for Utilities}, volume = {16}, pages = {2364}, journal = {Energies}, number = {5}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en16052364}, year = {2023}, abstract = {Peer-to-peer (P2P) energy markets constitute a promising approach for locally coordinating the increasing amount of distributed energy resources (DERs) in the distribution system. Although the benefits of P2P markets for the prosumers are already well understood, their impact on utilities is not well discussed nor well understood. This hinders the development of regulatory frameworks, which are still needed to allow for the widespread adoption of decentralized energy markets in any interested country. So far, research has been conducted in specific isolated aspects, making it difficult to understand the overall implications for utilities. The present study aims to tackle this research gap by comprehensively evaluating P2P markets' effects, considering utilities as primary stakeholders. A qualitative roadmap with the overall benefits and challenges of adopting P2P by utilities is outlined to reach this purpose. Technical and economic criteria are assigned for comparing a P2P market to the current regulatory framework. Each criterion is evaluated in a co-simulation platform connecting a market model to a power flow model. Market performance is assessed by revenue analysis, and grid operation indicators evaluate grid performance. Furthermore, network fees are introduced as compensation mechanisms for the net revenue loss. Comparison scenarios encompass network fees and the number of agents, PV, and storage penetration. Results demonstrate that there is no possible benefit for both utilities and prosumers simultaneously if looking exclusively at the financial balance of the market. An equilibrium in benefits for all stakeholders is achievable if non-financial metrics are considered in an integrated market and fee structure analysis. Moreover, results demonstrate that the design of market structures must be sensitive to network configurations and DER penetration changes. This study contributes toward comprehending how the utilities could embrace P2P markets as a feasible solution for grid coordination challenges, opening a new set of questions for further research.}, language = {en} } @inproceedings{SchmittReumSummetal.2024, author = {Schmitt, David and Reum, Tobias and Summ, Thorsten and Trinkl, Christoph and Schrag, Tobias}, title = {Potential of a Long-Term Predictive Controller for Managing Energy Storages to Reduce the Electric Grid-Load of an Air-Source Heat Pump}, booktitle = {Proceedings of the International Renewable Energy Storage and Systems Conference (IRES 2023)}, editor = {Droege, Peter and Quint, Lelia}, publisher = {Atlantis Press}, address = {Dordrecht}, isbn = {978-94-6463-455-6}, doi = {https://doi.org/10.2991/978-94-6463-455-6_21}, pages = {205 -- 211}, year = {2024}, abstract = {Electrifying the domestic heating sector is mandatory to decarbonize the buildings sector but leads to additional peak loads in the public grid. Air-source heat pumps the mostly used technology in this regard even though, they suffer from lower efficiency during times of high heat demands. The usage of energy storages and predictive controllers enables operation shifting and hence offers potential to decrease the peak loads in the electric grid. This potential can be increased by using a longer prediction horizon as extended operation shifting can be performed. In this contribution, a methodology to derive the theoretical potential on the grid peak load reduction of such a long-term predictive controller is introduced. The electric load profile of an air-source heat pump in a typical German single-family home was generated based on different weather data scenarios for the city of Ingolstadt. Based on the profile the dependency between peak load reduction and required storage capacity was identified. In the case study a reduction of the peak load from 21 - 31\% for an unrenovated building was achieved using a 500 L buffer storage. Further investigation needs to be done to derive a more realistic potential for renovated or new buildings.}, language = {en} } @article{MehtaShahZoerner2024, author = {Mehta, Kedar and Shah, Meeth Jeetendra and Z{\"o}rner, Wilfried}, title = {Agri-PV (Agrivoltaics) in Developing Countries: Advancing Sustainable Farming to Address the Water-Energy-Food Nexus}, volume = {17}, pages = {4440}, journal = {Energies}, number = {17}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en17174440}, year = {2024}, abstract = {The escalating demand for water, energy, and food, coupled with the imperative for sustainable development, necessitates innovative solutions to address the complex interdependencies within the water-energy-food nexus. In this context, agriculture and photovoltaics (Agri-PV or Agri-voltaics) systems have emerged as a promising approach to promoting sustainable agricultural practices while enhancing energy efficiency and food production. However, limited research, especially on the technical aspects of Agri-PV, has resulted in a knowledge gap regarding how to model and determine the suitability of Agri-PV for different crops based on local conditions. This study presents a novel approach to modeling and simulating Agri-PV systems for various major crops in developing countries, using Uzbekistan as a case study. It provides a blueprint for selecting suitable Agri-PV systems. The research investigates the technical feasibility of Agri-PV technology tailored to Uzbekistan's agricultural landscape, with broader implications for Central Asia. Employing a systematic methodology, the study begins by selecting appropriate sites and crops for Agri-PV system testing, ensuring the relevance and applicability of the research findings to the local context. Using advanced software tools such as PVSyst, the study accurately calculates photosynthetically active radiation (PAR) values specific to selected crops, bridging a significant knowledge gap and providing empirical data essential for informed decision making. The methodology further incorporates an in-depth analysis of economic and technical considerations in selecting PV modules and inverters, enhancing the scientific accuracy of the study. By strategically modeling Agri-PV systems based on parameters like row density, module distance, and tilt angle, this research aims to optimize the integration of photovoltaic technology with agricultural practices in Uzbekistan. Moreover, this study helps to understand the impact of Agri-PV systems on the water-energy-food nexus, providing valuable insights into the potential benefits and challenges specific to the region. The study identifies the positive impact of Agri-PV on major crops and provides a suitable design and modeling approach for sustainable farming practices.}, language = {en} } @article{VannahmeEhrenwirthSchrag2024, author = {Vannahme, Anna and Ehrenwirth, Mathias and Schrag, Tobias}, title = {Development and application of a guideline for assessing optimization potentials for district heating systems}, volume = {2024}, pages = {131226}, journal = {Energy}, number = {297}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-6785}, doi = {https://doi.org/10.1016/j.energy.2024.131226}, year = {2024}, abstract = {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.}, language = {en} } @article{BazziElHafdaouiKhallaayounetal.2023, author = {Bazzi, Ahmed and El Hafdaoui, Hamza and Khallaayoun, Ahmed and Mehta, Kedar and Ouazzani, Kamar and Z{\"o}rner, Wilfried}, title = {Optimization Model of Hybrid Renewable Energy Generation for Electric Bus Charging Stations}, volume = {17}, pages = {53}, journal = {Energies}, number = {1}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en17010053}, year = {2023}, abstract = {This paper introduces a comprehensive approach for sizing grid-connected hybrid renewable energy systems tailored for electric bus fleet operations. The study involves two main steps. First, a mathematical model that optimizes the configuration of such systems by considering daily electric bus consumption, solar irradiance, wind speed, and biomass potential is formulated. The model utilizes Pareto frontier multi-objective optimization to minimize the net present cost, the cost of energy, and greenhouse gas emissions. Second, the model is rigorously applied and tested in a real-world case study in Fez, Morocco, using HOMER Pro; the case study centers on the daily energy requirements of the buses, estimated at 2.5 megawatt hours per day, with a peak demand of 345 kilowatts. Two scenarios are explored, revealing a discernible trade-off dilemma between the full hybrid renewable energy scenario (Scenario 1) and the grid-connected hybrid renewable energy scenario (Scenario 2). In Scenario 2, the grid-connected hybrid renewable energy system demonstrates a notable 42.8\% reduction in the net present cost, totaling USD 984,624. Similarly, the levelized cost of energy experiences a significant decrease, reaching approximately 0.08 USD/kWh, marking a 38.1\% reduction. However, this apparent economic advantage is juxtaposed with a critical consideration—an increase in greenhouse gas emissions from null to 330,418 kg/year.}, language = {en} } @article{BachseitzSheryarSchmittetal.2024, author = {Bachseitz, Michael and Sheryar, Muhammad and Schmitt, David and Summ, Thorsten and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {PV-Optimized Heat Pump Control in Multi-Family Buildings Using a Reinforcement Learning Approach}, volume = {17}, pages = {1908}, journal = {Energies}, number = {8}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en17081908}, year = {2024}, abstract = {For the energy transition in the residential sector, heat pumps are a core technology for decarbonizing thermal energy production for space heating and domestic hot water. Electricity generation from on-site photovoltaic (PV) systems can also contribute to a carbon-neutral building stock. However, both will increase the stress on the electricity grid. This can be reduced by using appropriate control strategies to match electricity consumption and production. In recent years, artificial intelligence-based approaches such as reinforcement learning (RL) have become increasingly popular for energy-system management. However, the literature shows a lack of investigation of RL-based controllers for multi-family building energy systems, including an air source heat pump, thermal storage, and a PV system, although this is a common system configuration. Therefore, in this study, a model of such an energy system and RL-based controllers were developed and simulated with physical models and compared with conventional rule-based approaches. Four RL algorithms were investigated for two objectives, and finally, the soft actor-critic algorithm was selected for the annual simulations. The first objective, to maintain only the required temperatures in the thermal storage, could be achieved by the developed RL agent. However, the second objective, to additionally improve the PV self-consumption, was better achieved by the rule-based controller. Therefore, further research on the reward function, hyperparameters, and advanced methods, including long short-term memory layers, as well as a training for longer time periods than six days are suggested.}, language = {en} } @article{SummOyinlolaKhattaketal.2024, author = {Summ, Thorsten and Oyinlola, Muyiwa and Khattak, Sanober and Ehrenwirth, Mathias and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {Towards maximum cost-effectiveness: multi-objective design optimisation of insulating glass flat-plate collectors}, volume = {2025}, pages = {124594}, journal = {Applied Thermal Engineering}, number = {258}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1359-4311}, doi = {https://doi.org/10.1016/j.applthermaleng.2024.124594}, year = {2024}, abstract = {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.}, language = {en} } @article{LwakatareVyavahareMehtaetal.2024, author = {Lwakatare, Bertha and Vyavahare, Priyanka and Mehta, Kedar and Z{\"o}rner, Wilfried}, title = {Electrification Planning for Off-Grid Communities in Sub-Saharan Africa: Advancing Energy Access}, volume = {17}, pages = {5994}, journal = {Energies}, number = {23}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en17235994}, year = {2024}, abstract = {Sub-Saharan Africa, especially its rural areas, faces significant challenges in achieving universal electrification despite its abundant renewable energy resources. The region has the highest population without access to electricity, largely due to economic, infrastructural, and geographical barriers. Energy poverty is a critical issue that hinders sustainable development and exacerbates inequalities. Namibia's sustainable energy policy aligns with the global Sustainable Development Goals (SDGs), particularly SDG 7, which aims to provide affordable and reliable modern energy access for all. The policy emphasizes mini-grids and decentralized power systems as key strategies for rural electrification. However, despite increased deployment of mini-grids, these solutions often struggle with long-term sustainability. This research explores cost-effective electrification strategies through scenario-based modeling to reduce energy poverty and expand energy access in Namibia's rural communities, focusing on the existing mini-grids in Tsumkwe and Gam. Using a comprehensive methodology that incorporates HOMER Pro for mini-grid capacity expansion and MS Excel for evaluating main-grid extensions, this study aims to identify the most feasible and economical electrification solutions. The analysis compares electricity supply, total net present cost, and the levelized cost of electricity across these systems. The findings will offer insights into addressing energy poverty in Namibia and provide recommendations for sustainable and scalable rural electrification across Sub-Saharan Africa.}, language = {en} } @article{MehtaZoerner2023, author = {Mehta, Kedar and Z{\"o}rner, Wilfried}, title = {Cracking the code: mapping residential building energy performance in rural Central Asia through building typologies}, volume = {5}, pages = {349}, journal = {SN Applied Sciences}, number = {12}, publisher = {Springer Nature}, address = {Cham}, issn = {2523-3971}, doi = {https://doi.org/10.1007/s42452-023-05607-1}, year = {2023}, abstract = {Buildings in rural Central Asia have unique characteristics as they were built during the Soviet era (during 1950-1960) without any energy efficiency measures. The special and aged building stock pose a crucial challenge on energy security and energy supply. However, accurate scientific data on their energy usage is lacking, highlighting a research gap about robust and validated methodology to determine the energy use of rural Central Asian buildings. In response to this need, this research paper proposes a set of generalised residential building typologies for rural Central Asia, with a focus on Kyrgyzstan. The study combines quantitative and qualitative methods, including household surveys, energy demand modelling, EnergyPlus simulations, and result validation. It derives energy-based building typologies from construction year and building envelope characteristics. Through numerous validated simulations, it was identified that the heat demand for rural Kyrgyz houses is 3-5 times here compared to European houses (250-400 kWh/m2). The study revealed the estimated heat demand for homes in rural Kyrgyzstan, indicating a significant potential for improving building energy efficiency in the region. These results can inform specific approaches, such as building renovation plans, energy certification, and renovation strategies. Furthermore, the validated methodology introduced offers opportunities for researchers in the field of building energy efficiency and can be applied to similar regions in Central Asia with comparable building stocks and climates.}, language = {en} } @article{SummOyinlolaKhattaketal.2023, author = {Summ, Thorsten and Oyinlola, Muyiwa and Khattak, Sanober and Trinkl, Christoph and Z{\"o}rner, Wilfried}, title = {Statistical analysis of solar thermal collectors in the Solar Keymark Database}, volume = {2024}, pages = {103581}, journal = {Sustainable Energy Technologies and Assessments}, number = {61}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2213-1396}, doi = {https://doi.org/10.1016/j.seta.2023.103581}, year = {2023}, abstract = {Experimental, analytical, or numerical investigations are ordinarily conducted to reveal optimisation potential for solar thermal collectors. At the same time, the 'Solar Keymark Database' contains more than 2,000 test reports from certified laboratories featuring properties including thermal efficiency, dimensions, or optical properties. This dataset offers untapped potential for statistical analyses as an alternative optimisation approach. Hence, this paper aims to provide a) the first statistical findings of solar thermal collector properties listed in the Solar Keymark Database and b) insights into statistical relations between these properties. The key correlations observed from the analysis of flat-plate collectors were between efficiency and both gross height (R = 0.30) and gross area (R = 0.27). We concluded that preferable collector designs may be featured with larger area to height ratios. The analyses of evacuated tube collectors revealed a strong correlation between efficiency and transversal incidence angle modifier (R = -0.65) as a result from different tube spacing. It was noticeable that the quasi-dynamic test method reported significantly higher efficiencies (7.14 percentage points) for evacuated tube collectors, which should be carefully considered for future test procedures. Overall, the statistical analysis was in accordance with conventional bottom-up analyses and revealed insightful dependencies for the present collector data.}, language = {en} } @article{MehtaZoerner2025, author = {Mehta, Kedar and Z{\"o}rner, Wilfried}, title = {Crop selection in Agri-PV: international review based strategic decision-making model}, volume = {2025}, pages = {100143}, journal = {Solar Compass}, number = {16}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2772-9400}, doi = {https://doi.org/10.1016/j.solcom.2025.100143}, year = {2025}, abstract = {Agri-Photovoltaics (Agri-PV) is well known for its dual land use, integrating solar energy generation with agricultural production. This not only optimizes land use but also enhances food and energy security. Since Agri-PV is closely linked with crop cultivation, it is not solely about energy generation but also requires careful consideration of crop suitability within Agri-PV installations. Despite its significance, there is limited information available to guide decision-making for crop selection in Agri-PV systems. Selecting suitable crops remains a complex challenge, as factors such as shading tolerance, water requirements, and economic viability vary across different geographical and climatic conditions. This study develops a novel, review-based decision support model for crop selection in Agri-PV systems, synthesizing international research and case studies to provide a structured framework for decision-making. The model is based on 12 main crop typologies and key parameters such as water use, shading adaptability, crop yield/economic potential, and space requirements, derived from 117 research articles and case studies from 25 countries. By leveraging insights from successful international implementations, the model provides a practical framework for policymakers, farmers, and energy planners to enhance the sustainability and efficiency of Agri-PV projects. Findings suggest that crop selection strategies must align with regional climate conditions and PV system design to maximize synergies between energy and food production. High-value crops that require less space and have higher shade tolerance are more suitable for small-scale or decentralized Agri-PV systems. Future research should focus on advanced modeling techniques, AI-driven optimization, and real-world pilot studies to further refine decision-making in Agri-PV deployment. This study contributes to the growing body of knowledge on Agri-PV systems by providing a novel crop suitability matrix for effective decision-making.}, language = {en} } @article{VannahmePatelSchmittetal.2024, author = {Vannahme, Anna and Patel, Dharmik and Schmitt, David and Summ, Thorsten and Trinkl, Christoph and Schrag, Tobias}, title = {Technical and economic analysis of digitally controlled substations in local district heating networks}, volume = {2024}, pages = {133585}, journal = {Energy}, number = {312}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0360-5442}, doi = {https://doi.org/10.1016/j.energy.2024.133585}, year = {2024}, abstract = {Since the 1990s, there has been a noticeable increase in the establishment of local district heating networks in Germany, coinciding with the use of thermal energy from biogas and biomass facilities. Historically, the prioritization of economically efficient heat utilization was subdued due to favorable electricity feed-in tariffs. However, with the expiration of Renewable Energy Sources Act subsidies, operators shifted focus to the operational costs of district heating networks. This study aims to examine the effects of optimizing controllers and valves at district heating substations in single-family homes, utilizing two local district heating networks. The emphasis is on evaluating impacts on operating costs and determining whether the economic and energetic benefits justify implementation. Simulation studies in MATLAB/Simulink Simscape depict both consumers and district heating networks individually, without aggregation. In the most favorable scenario, investing in enhancing substation controllers in single-family homes is projected to yield returns after 13 years. Comprehensive optimization of all substation controls in single-family homes can potentially result in up to 9\% savings in thermal energy demand due to reduced heat losses and a corresponding 9\% reduction in electrical power consumption for the main pump.}, language = {en} } @inproceedings{MastHuemmerHolzhammer2022, author = {Mast, Tanja and H{\"u}mmer, Benedikt and Holzhammer, Uwe}, title = {Smart Markets als marktbasierte Erg{\"a}nzung zum deutschen Engpassmanagement}, booktitle = {17. Symposium Energieinnovation}, subtitle = {Konzeptionierung anhand eines Modellbeispiels}, publisher = {Technische Universit{\"a}t Graz}, address = {Graz}, url = {https://www.tugraz.at/events/eninnov2022/nachlese/download-beitraege/stream-a/\#c318498}, year = {2022}, language = {de} } @inproceedings{MastHuemmerHolzhammer2021, author = {Mast, Tanja and H{\"u}mmer, Benedikt and Holzhammer, Uwe}, title = {Potential of Demand Side Management and Biogas Plants in regional market-based Congestion Management}, booktitle = {ENERDAY 15th Conference on Energy Economics and Technology "Creative Destruction? Disruptive innovation in times of Covid and an accelerated energy system transformation": Book of Abstracts}, publisher = {TU Dresden}, address = {Dresden}, url = {https://tu-dresden.de/bu/wirtschaft/bwl/ee2/tagungen/enerday-archives}, pages = {22 -- 23}, year = {2021}, language = {en} } @inproceedings{ReumNataleSchmittetal.2025, author = {Reum, Tobias and Natale, Christian and Schmitt, David and Dongellini, Matteo and Naldi, Claudia and Summ, Thorsten and Morini, Gian Luca and Schrag, Tobias}, title = {Control Strategies for Active Regeneration in a Dual-Source Heat Pump}, booktitle = {Proceedings of the 15th REHVA HVAC World Congress - CLIMA 2025: Volume 1}, editor = {Zilio, Claudio and Busato, Filippo and Mazzarella, Livio and Noro, Marco}, publisher = {Springer}, address = {Cham}, isbn = {978-3-032-06806-4}, doi = {https://doi.org/10.1007/978-3-032-06806-4_55}, pages = {564 -- 574}, year = {2025}, language = {en} } @inproceedings{SchmittReumSummetal.2025, author = {Schmitt, David and Reum, Tobias and Summ, Thorsten and Schrag, Tobias}, title = {Comparison of Heat Pump Modelling Approaches for Predictive Controllers to Optimize the Efficiency of Modulating Air-Source Heat Pumps: A Case Study from South Germany}, booktitle = {Proceedings of the 15th REHVA HVAC World Congress - CLIMA 2025: Volume 1}, editor = {Zilio, Claudio and Busato, Filippo and Mazzarella, Livio and Noro, Marco}, publisher = {Springer}, address = {Cham}, isbn = {978-3-032-06806-4}, doi = {https://doi.org/10.1007/978-3-032-06806-4_59}, pages = {611 -- 620}, year = {2025}, language = {en} } @article{RoueguiBellabairElAslietal.2025, author = {Rouegui, Meryem and Bellabair, Hind and El Asli, Abdelghani and Amar, Amine and Z{\"o}rner, Wilfried and Rachidi, Fouad and Lghoul, Rachid}, title = {Bio-Methanization of Sheep Manure and Beet Waste in the Meknes-F{\`e}s Region, Morocco: Effects of Pretreatment and Machine Learning Applications for Biochemical Methane Potential Prediction}, volume = {10}, pages = {213}, journal = {Recycling}, number = {6}, publisher = {MDPI}, address = {Basel}, issn = {2313-4321}, doi = {https://doi.org/10.3390/recycling10060213}, year = {2025}, abstract = {Sheep manure and beet waste (the uneatable leaf part of the beet) are promising feedstock for biogas production due to their abundance and organic richness. However, their high lignocellulosic content reduces anaerobic digestibility and controls methane yield. This study investigates the effect of various pretreatment strategies, namely physical, thermal, and combined physical-thermal methods, on the Biochemical Methane Potential (BMP) of sheep manure and beet waste. Batch anaerobic digestion experiments were conducted under mesophilic conditions, with BMP values recorded for each treatment. The highest BMP for sheep manure, 125 Nml CH4/g VS, was achieved using combined physical and thermal pretreatment. This approach enhanced methane production by 16\%, 25\%, and 60\% compared to physical pretreatment (PP) alone, thermal pretreatment (TP) alone, and no pretreatment, respectively, while the one BMP for beet waste is 80 Nml CH4/g VS and obtained with thermal pretreatment. To predict BMP outcomes, three machine learning approaches are applied, namely Linear Regression (LM), Random Forest Regression (RFR), and Gradient Boosting Machine (GBM), using digestion time (N days), total solids (Ts), volatile solids (Vs), pretreatment type, and biomass type. The variance analysis confirmed that the interaction between pretreatment and biomass type significantly improved model performance. While diagnostic checks revealed non-linear patterns limiting the linear model, ensemble methods achieved stronger results. The RFR model explained 79.5\% of the variance with a Root Mean Square Error (RMSE) of about 15.7, whereas the GBM model achieved the lowest RMSE of 5.05. GBM captures complex non-linear interactions. In addition, variable importance analyses identified digestion time, solid content, and pretreatment as the most influential factors for methane yield, with the combined chemical and physical pretreatment producing the highest biogas outputs. These findings underscore the potential of advanced machine learning models, particularly GBM (Gradient Boosting Machine), for optimizing anaerobic digestion strategies and maximizing biogas recovery from sheep manure and beet waste.}, language = {en} } @article{MehtaJainZoerner2025, author = {Mehta, Kedar and Jain, Rushabh Bansilal and Z{\"o}rner, Wilfried}, title = {Agrivoltaics Around the World: Potential, Technology, Crops and Policies to Address the Energy-Agriculture Nexus for Sustainable and Climate-Resilient Land Use}, volume = {18}, pages = {6417}, journal = {Energies}, number = {24}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en18246417}, year = {2025}, abstract = {The urgent pursuit of climate-resilient agriculture and clean energy systems, central to the Energy-Agriculture Nexus and the UN Sustainable Development Goals, has accelerated global interest in agrivoltaic (Agri-PV) technologies. This paper presents a global systematic review and meta-analysis of 160 peer-reviewed studies, structured through a five-stage thematic synthesis: (1) mapping global and regional Agri-PV deployment and potential, (2) analyzing system design and modeling methodologies, (3) evaluating crop suitability under partial shading, (4) reviewing enabling policies and regulatory frameworks, and (5) assessing techno-economic feasibility and investment barriers. Results reveal that Europe and Asia lead Agri-PV development, driven by incentive-based policies and national tenders, while limited regulatory clarity and high capital costs constrain wider adoption. Despite technological progress, no integrated model fully captures the coupled energy, water, and crop dynamics essential for holistic assessment. Strengthening economic valuation, policy coherence, and standardized modeling approaches will be critical to scale Agri-PV systems as a cornerstone of sustainable and climate-resilient land use.}, language = {en} } @article{MehtaLwakatareZoerneretal.2025, author = {Mehta, Kedar and Lwakatare, Bertha and Z{\"o}rner, Wilfried and Ehrenwirth, Mathias}, title = {Mini-grid performance in Sub-Saharan Africa: case studies from Tsumkwe and Gam, Namibia}, volume = {12}, pages = {30}, journal = {Sustainable Energy Research}, number = {1}, publisher = {SpringerOpen}, address = {Singapore}, issn = {2731-9237}, doi = {https://doi.org/10.1186/s40807-025-00174-y}, year = {2025}, abstract = {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.}, language = {en} } @article{MehtaEhrenwirthZoerneretal.2023, author = {Mehta, Kedar and Ehrenwirth, Mathias and Z{\"o}rner, Wilfried and Greenough, Richard}, title = {Need of energy transition at roof of the world}, volume = {2023}, pages = {101271}, journal = {Energy for Sustainable Development}, subtitle = {Correlative approach to interpret energy identity of high-altitude Central Asian communities}, number = {76}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2352-4669}, doi = {https://doi.org/10.1016/j.esd.2023.101271}, year = {2023}, language = {en} } @unpublished{MuellerSchmittBottetal.2026, author = {M{\"u}ller, Simon Nikolaus and Schmitt, David and Bott, Christoph and Akbar, Shariq and Bayer, Peter and Schrag, Tobias}, title = {Operating thermal source networks - How supply temperature and ground exchange shape performance}, titleParent = {SSRN}, publisher = {Elsevier}, address = {Amsterdam}, doi = {http://dx.doi.org/10.2139/ssrn.6034530}, year = {2026}, language = {en} } @inproceedings{ReumSchmittSummetal.2024, author = {Reum, Tobias and Schmitt, David and Summ, Thorsten and Schrag, Tobias}, title = {Energetic Potential of Parallel Operation of Two Heat Sources in a Dual-Source Heat Pump}, booktitle = {International Sustainable Energy Conference - Proceedings}, editor = {Fink, Christian and Brunner, Christoph}, publisher = {TIB Open Publishing}, address = {Hannover}, issn = {2976-2030}, doi = {https://doi.org/10.52825/isec.v1i.1158}, year = {2024}, abstract = {Dual-source heat pumps can mitigate disadvantages of single source heat pumps: They have fewer geological requirements compared to ground-source heat pumps while having higher efficiencies compared to air-source heat pumps. Parallel operation of two heat sources can also make electric heaters for peak loads obsolete, leading to economic benefits in the operational costs. Parallel operation has not been analysed thoroughly at different evaporation temperature gradients. To address this gap in research, four possible interconnections of two heat sources were analysed using a refrigerant cycle simulation, two with similar and two with separate evaporation pressures. The energetic potential of each interconnection is evaluated and compared to single source operation with an air-source and a ground-source heat pump. The results showed that only the interconnections with separate evaporation pressure allowed significant reduction in evaporation power from the ground source. As expected, the efficiency - compared to single air-source operation - increased for all parallel interconnections but decreased compared to ground-source operation. Efficient peak load coverage with small ground-source collectors therefore requires a more complex interconnection of completely split evaporator branches at different evaporation pressures. While the efficiency and heating power compared to single ground-source operation decreased slightly (by 4\% and 6\%, respectively), the power load on the GSHX and ASHX reduced to about 54\% and 66\% compared to the corresponding single-source operation, respectively. This allows high efficiency at reduced GSHX size and ASHX noise emission. Additionally, this interconnection also allows increased flexibility for improved heat source management.}, language = {en} }