@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{HechelmannSeeversOtteetal.2020, author = {Hechelmann, Ron-Hendrik and Seevers, Jan-Peter and Otte, Alexander and Sponer, Jan and Stark, Matthias}, title = {Renewable Energy Integration for Steam Supply of Industrial Processes: A Food Processing Case Study}, volume = {13}, pages = {2532}, journal = {Energies}, number = {10}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en13102532}, year = {2020}, abstract = {This study highlights the CO2,e -emission reduction potentials and related economic consequences for changing steam generation from fossil to renewable. Seven different utility concepts are developed, including a steam accumulator for load management. Peculiarities for the integration of biogas boilers, biomass-fuelled boilers, electrode steam boilers, biomethane-fuelled solid oxide fuel cells, micro gas turbine, solar energy systems, heat pumps and steam accumulators into a steam system with fluctuating steam demand are explained and the energy balance based models for the simulation study are described. The characteristics of batch processes, start up times and part load efficiency are considered via an annual dynamic simulation. Based on a detailed process analysis and dimensioning of the utilities and the accumulator a comprehensive simulation study is conducted for a pet food processing company having an average steam demand of 18,000 MWh at around 9 bar and 3 t/h. The results show that the highest CO2,e -emissions reduction of up to 63\% is achieved by the transition to a solid biomass-fuelled boiler system. This leads to an increase of the operating costs by 27.8\%}, 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} } @article{ContiSaidiGoldbrunner2019, author = {Conti, Fosca and Saidi, Abdessamad and Goldbrunner, Markus}, title = {CFD Modelling of Biomass Mixing in Anaerobic Digesters of Biogas Plants}, volume = {23}, journal = {Environmental and Climate Technologies}, number = {3}, publisher = {RTU Press}, address = {Riga}, issn = {2255-8837}, doi = {https://doi.org/10.2478/rtuect-2019-0079}, pages = {57 -- 69}, year = {2019}, abstract = {Cut in greenhouse gas emissions, increment of energy from renewables and improvement in energy efficiency represent the three key targets for future energy systems. Among the available bioenergy technologies, biogas production via biodegradation and anaerobic digestion is a widely applied approach, not only to produce biofuels but also to manage industrial and domestic organic waste. Within the biogas production, a sufficient mixing of the organic mass is a crucial step to ensure high biogas yields by bacteria and enzymes. Measurements of the electric power consumption of biogas plants revealed that the electrical energy demand of the stirrer system has a high share of the total electricity consumption of a biogas plant. Investigations on real biogas digesters to optimize the mixing process are cost and time intensive. Therefore, laboratory prototypes and computational simulations represent promising alternatives to analyse and improve the efficiency of mixing systems. In this paper, a computational fluid dynamics (CFD) model is presented, which is applied to commercial stirring systems. The case of two propeller stirrers, located in diametrically opposite positions in a tank filled with ca. 1400 m3 of substrate is described in detail. For the simulation, the rheology of the fluid is adapted to a biomass with 12 wt \% dry matter content and obeying the non-Newtonian generalized Ostwald-de Waele power law. The developed simulation procedure considers the rotation angle of each propeller and its height. A total of 441 mixing configurations are calculated and evaluated in terms of the technical benefit. The investigation reveals that locations of the rotors far away from the bottom and high rotational angles cause advantageous fluid dynamics.}, language = {en} } @article{ReiterTrinklZoerneretal.2015, author = {Reiter, Christoph and Trinkl, Christoph and Z{\"o}rner, Wilfried and Hanby, Victor Ian}, title = {A Dynamic Multinode Model for Component-Oriented Thermal Analysis of Flat-Plate Solar Collectors}, volume = {2015}, pages = {280694}, journal = {Journal of Solar Energy}, publisher = {Hindawi Publ.}, address = {New York; Cairo}, issn = {2314-6230}, doi = {http://dx.doi.org/10.1155/2015/280694}, year = {2015}, abstract = {A mathematical model of a flat-plate solar collector was developed on the basis of the physical principles of optics and heat transfer in order to determine collector's component temperatures as well as collector efficiency. In contrast to many available models, the targeted use of this dynamic model is the detailed, theoretical investigation of the thermal behaviour of newly developed or adjusted collector designs on component level, for example, absorber, casing, or transparent cover. The defined model is based on a multinode network (absorber, fluid, glazing, and backside insulation) containing the relevant physical equations to transfer the energy. The heat transfer network covers heat conduction, convection, and radiation. Furthermore, the collector optics is defined for the plane glazing and the absorber surface and also considers interactions between them. The model enables the variation of physical properties considering the geometric parameters and materials. Finally, the model was validated using measurement data and existing efficiency curve models. Both comparisons proved high accuracy of the developed model with deviation of up to 3\% in collector efficiency and 1 K in component temperatures.}, language = {en} } @article{GresshakeBoschTutunaruetal.2025, author = {Greßhake, Lukas and Bosch, Stephan and Tutunaru, Robin and Holzhammer, Uwe}, title = {What do you mean by '(un-)suitable'? Analysing the diversity of social acceptance towards the deployment of renewable energies in different landscapes}, volume = {20}, journal = {Journal of Land Use Science}, number = {1}, publisher = {Taylor \& Francis}, address = {London}, issn = {1747-4248}, doi = {https://doi.org/10.1080/1747423X.2025.2499280}, pages = {117 -- 150}, year = {2025}, abstract = {Local energy transitions are shaped by diverse stakeholder perspectives on land use, reflecting competing values, knowledge systems, and political views. This study applies the landscape services framework to systematically assess renewable energy (RE) suitability across different landscapes, capturing both ecological and socio-cultural dimensions. Through stakeholder surveys in two German regions and statistical comparative analysis, we reveal how suitability perceptions vary significantly: (1) between stakeholder groups (e.g. conservationists vs. developers), (2) across regions (industrial vs. ecological-cultural contexts), and (3) even within groups sharing similar objectives. Key findings show strong preference for RE development in industrial and agricultural zones ('acceptance corridors') and opposition in ecologically sensitive areas, though with notable regional exceptions. The landscape services approach proves effective in mapping these conflicts and consensus areas, providing actionable insights for spatially sensitive RE planning. Our results underscore the need to complement technical siting criteria with structured assessments of social landscape values to enable just and locally accepted energy transitions.}, 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} } @unpublished{ChaturvediKumarLambaetal.2024, author = {Chaturvedi, Pushpendra Kr. and Kumar, Nand and Lamba, Ravita and Mehta, Kedar}, title = {Multi-objective optimization of glazing and shading configurations for visual, thermal, and energy performance of cooling dominant climatic regions of India}, titleParent = {Research Square}, publisher = {Research Square}, address = {Durham}, doi = {https://doi.org/10.21203/rs.3.rs-4983831/v1}, year = {2024}, abstract = {Climate adaptive passive design features such as glazing and shading configurations, often exhibit conflicting behaviour to maintaining indoor visual and thermal environment while minimizing energy consumption. This study employed the MOO approach through SPEA-II and HypE algorithms to find the efficient glazing and shading configurations in four cooling dominant climatic zones of India such as hot and dry, composite, warm and humid, and temperate. A residential building situated in Jaipur city (India) was chosen for the analysis and to demonstrate the effectiveness and reliability of the optimization process. Twenty-six design variables including wall window ratio, louvers depth, louvers count, fin depth and fins count of each orientation, window height, sill height, glazing U-value, solar heat gain coefficient, and visual light transmittance were imported into the Octopus to investigate their interactive impact on the Useful Daylight Illuminance (UDI), Thermal Discomfort Percentage (TDP) and Energy Use Intensity (EUI). The optimized trade-off solutions represented a considerable improvement; UDI increased by 24.61\%, 21.90\%, 14.91\% \& 26.41\%, and TDP reduced by 10.38\%, 1.5\%, 13.95\%, \& 17.68\%, and EUI decreased by 10.10\%, 1.9\%, 15.82\%, \& 19.19\% compared to initially generated solutions for Ahmedabad, Delhi, Mumbai and Bangalore cities respectively. Finally, the Bayesian machine learning technique has been used for sensitivity analysis to identify the correlation between the design variables and performance objectives. The outcomes of this research can help architects in selecting optimal glazing and shading features for both new building design and retrofitting of existing buildings in the tropical climatic conditions of India.}, language = {en} } @inproceedings{MuellerSchmitt2023, author = {M{\"u}ller, Lucas and Schmitt, David}, title = {Comparison of energy efficiency of a linear time-invariant and a linear time-varying state space model in a Model Predictive Controller of an air-to-water heat pump}, booktitle = {Applied Research Conference 2023 Conference Proceedings: 3rd July 2023 Technische Hochschule Ingolstadt}, editor = {Vaculin, Ondrej}, publisher = {Technische Hochschule Ingolstadt}, address = {Ingolstadt}, doi = {https://doi.org/10.57825/repo_in-5244}, pages = {185 -- 189}, year = {2023}, language = {en} } @inproceedings{Idda2023, author = {Idda, Johannes}, title = {Simulation and analysis of the energy demand of the refrigeration system in the refrigerated transport of dairy products}, booktitle = {Applied Research Conference 2023 Conference Proceedings: 3rd July 2023 Technische Hochschule Ingolstadt}, editor = {Vaculin, Ondrej}, publisher = {Technische Hochschule Ingolstadt}, address = {Ingolstadt}, doi = {https://doi.org/10.57825/repo_in-5244}, pages = {171 -- 175}, year = {2023}, language = {en} } @inproceedings{Seiler2023, author = {Seiler, Michael}, title = {Design concept for the construction of a solar thermal pilot plant}, booktitle = {Applied Research Conference 2023 Conference Proceedings: 3rd July 2023 Technische Hochschule Ingolstadt}, editor = {Vaculin, Ondrej}, publisher = {Technische Hochschule Ingolstadt}, address = {Ingolstadt}, doi = {https://doi.org/10.57825/repo_in-5244}, pages = {205 -- 209}, year = {2023}, 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{LabandStoecklMittreiteretal.2025, author = {Laband, Dana Laureen and St{\"o}ckl, Martin and Mittreiter, Annedore and Holzhammer, Uwe}, title = {Barrier Analysis of Flexibilization of Cooling Supply Systems}, volume = {18}, pages = {4133}, journal = {Energies}, number = {15}, publisher = {MDPI}, address = {Basel}, issn = {1996-1073}, doi = {https://doi.org/10.3390/en18154133}, year = {2025}, abstract = {The present study examines the barriers that prevent cooling system flexibility from being optimized. In the context of an increasing reliance on renewable energy sources, the necessity for flexible energy utilization is becoming increasingly apparent. A survey and discussion groups were conducted with various stakeholders within the cooling value chain to obtain their experiences and insights regarding barriers to flexibilization. The findings point out that economic, technological, and regulatory barriers are the primary factors impeding the implementation of flexible solutions. In particular, high investment costs, complex technical implementation, a lack of information, and a complicated legal framework were identified as significant impediments. To enhance the flexibility of cooling systems, coordinated efforts are necessary to address these barriers. Practical examples, training, and the standardization and digitalization of processes could facilitate the widespread implementation of flexible cooling systems.}, 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} }