TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Missall, Siegmund A1 - Degembaeva, Nadira A1 - Akmatov, Kuban A1 - Zörner, Wilfried T1 - Energy Profiling of a High-Altitude Kyrgyz Community: Challenges and Motivations to Preserve Floodplain Ecosystems Based on Household Survey JF - Sustainability N2 - The floodplain areas along the Naryn River in Kyrgyzstan are essential as they hold the riparian (local) ecosystems because they provide firewood, pastureland, and areas for recreation and protection against erosion. Due to limited access to adequate, reliable, and sustainable energy services, the rural population usually derived their energy needs from multiple natural energy resources (i.e., firewood, charcoal, agricultural residues, animal dung, and wood branches). This is considered a common and predominant practice in rural Kyrgyzstan. This situation leads to a negative impact on local ecosystem services. In addition to that, the reliance on solid fuels contributes to indoor and outdoor air pollution, which is partially threatening the local ecosystem services. By contrast, the employment of renewable-based energy supply systems would substantially reduce the burden on the environment, which is mainly untapped. To integrate renewable energies, it is important to understand the energy behavior of floodplain communities. In that response, the presented article is the first attempt to capture the energy identity of the floodplain community of Kyrgyzstan based on a quantitative energy-based (on-site) household survey. Furthermore, the present research article synthesizes the driving factors that have a (direct or indirect) impact on the energy and local ecosystem services. In addition, the present article proposes a brief pathway for the sustainable energy transition. The article records the recommendation to integrate renewable energies to preserve the local ecosystems of Kyrgyzstan. UR - https://doi.org/10.3390/su132313086 KW - Central Asia KW - ecosystem services KW - energy pattern KW - energy profiling KW - floodplain community KW - high-altitude KW - household survey KW - Kyrgyzstan KW - renewable energies KW - sustainability Y1 - 2021 UR - https://doi.org/10.3390/su132313086 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-10895 SN - 2071-1050 N1 - This article belongs to the Special Issue "Floodplain Ecology and Sustainable Restoration with Regard to Ecosystem Services" VL - 13 IS - 23 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Greenough, Richard T1 - The energy situation in Central Asia BT - a comprehensive energy review focusing on rural areas JF - Energies N2 - The northern part of the globe is dominated by industrialisation and is well-developed. For many years, the southern part of the world (South Asia, Africa etc.) has been a target of research concentrating on access to energy (mainly electricity) in rural regions. However, the Central Asian region has not been a focus of energy research compared to South East Asia and Africa. Despite plentiful domestically available energy resources, the energy supply in Central Asia is very unevenly distributed between urban and rural areas. Almost half of the total population of Central Asia lives in rural areas and there is a lack of access to modern energy services to meet primary needs. To analyse the energy situation (i.e., electricity, heating, hot water consumption, cooking, etc.) in rural Central Asia, this paper reviews residential energy consumption trends in rural Central Asian regions as compared to urban areas. Furthermore, the paper illustrates the potential of renewable energies in Central Asia. To perform the study, a qualitative comparative analysis was conducted based on a literature review, data, and statistical information. In summary, the presented article discusses the rural energy situation analytically and provides in-depth insights of Central Asian energy infrastructure. UR - https://doi.org/10.3390/en14102805 KW - Central Asia KW - energy resources KW - rural energy supply KW - energy services KW - renewable energy Y1 - 2021 UR - https://doi.org/10.3390/en14102805 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-10908 SN - 1996-1073 VL - 14 IS - 10 PB - MDPI CY - Basel ER - TY - JOUR A1 - Vannahme, Anna A1 - Ehrenwirth, Mathias A1 - Schrag, Tobias T1 - Enhancement of a district heating substation as part of a low-investment optimization strategy for district heating systems JF - Resources N2 - In an ongoing project, low-investment measures for the optimization of district heating systems are analyzed. The optimization strategies are collected in a catalog, which is the core of a guideline. The application of this guideline is demonstrated using two concrete district heating networks as examples. In this study, the improvement of an analog controlled district heating substation by an electronic controller is investigated. High supply temperatures and heat losses are often a challenge in district heating networks. The district heating substations have a major influence on the network return temperatures. The comparison of the two substation setups with analog and electronic controllers is carried out by laboratory measurement. It can be shown that the return temperatures can be reduced by an average of 20 K in winter and transition, as well as 16 K in summer. The district heating network losses are calculated for one of both specific district heating networks. They are calculated from the ratio of network losses to generated energy. The generated energy is the sum of network losses and consumer demand. The thermal losses of the network can be reduced by 3%. The volume flow in the heating network can be reduced to a quarter. Therefore, the pumping energy requirement drops sharply since these changes cubically affect the volume flow UR - https://doi.org/10.3390/resources10050053 KW - district heating substation KW - control KW - optimization KW - local district heating networks KW - non-retrofitted single-family houses KW - thermal test rig Y1 - 2021 UR - https://doi.org/10.3390/resources10050053 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-10951 SN - 2079-9276 VL - 10 IS - 5 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bugaje, Aminu A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried T1 - Electric two-wheeler vehicle integration into rural off-grid photovoltaic system in Kenya JF - Energies N2 - In both rural and urban areas, two-wheeler vehicles are the most common means of transportation, contributing to local air pollution and greenhouse gas emissions (GHG). Transitioning to electric two-wheeler vehicles can help reduce GHG emissions while also increasing the socioeconomic status of people in rural Kenya. Renewable energy systems can play a significant role in charging electric two-wheeled vehicles, resulting in lower carbon emissions and increased renewable energy penetration in rural Kenya. As a result, using the Conventional and Renewable Energy Optimization (CARNOT) Toolbox in the MATLAB/Simulink environment, this paper focuses on integrating and modeling electric two-wheeled vehicles (e-bikes) into an off-grid photovoltaic Water-Energy Hub located in the Lake Victoria Region of Western Kenya. Electricity demand data obtained from the Water-Energy Hub was investigated and analyzed. Potential solar energy surplus was identified and the surplus was used to incorporate the electric two-wheeler vehicles. The energy consumption of the electric two-wheeler vehicles was also measured in the field based on the rider’s driving behavior. The modeling results revealed an annual power consumption of 27,267 kWh, a photovoltaic (PV) electricity production of 37,785 kWh, and an electricity deficit of 370 kWh. The annual results show that PV generation exceeds power consumption, implying that there should be no electricity deficit. The results, however, do not represent the results in hourly resolution, ignoring the impact of weather fluctuation on PV production. As a result, in order to comprehend the electricity deficit, hourly resolution results are shown. A load optimization method was designed to efficiently integrate the electric 2-wheeler vehicle into the Water-Energy Hub in order to alleviate the electricity deficit. The yearly electricity deficit was decreased to 1 kWh and the annual electricity consumption was raised by 11% (i.e., 30,767 kWh), which is enough to charge four more electric two-wheeler batteries daily using the load optimization technique. UR - https://doi.org/10.3390/en14237956 KW - Lake Victoria KW - photovoltaic KW - off-grid KW - model KW - electric two-wheeled vehicle KW - Water-Energy Hub KW - CARNOT Y1 - 2021 UR - https://doi.org/10.3390/en14237956 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-11070 SN - 1996-1073 VL - 14 IS - 23 PB - MDPI CY - Basel ER - TY - JOUR A1 - Hechelmann, Ron-Hendrik A1 - Seevers, Jan-Peter A1 - Otte, Alexander A1 - Sponer, Jan A1 - Stark, Matthias T1 - Renewable Energy Integration for Steam Supply of Industrial Processes: A Food Processing Case Study JF - Energies N2 - 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% UR - https://doi.org/10.3390/en13102532 KW - biomass boilers KW - fuel cell KW - solar thermal KW - electrode boiler KW - steam systems KW - food processing industry KW - decarbonisation KW - energy costs Y1 - 2020 UR - https://doi.org/10.3390/en13102532 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9397 SN - 1996-1073 VL - 13 IS - 10 PB - MDPI CY - Basel ER - TY - JOUR A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - Evaluation Criteria and Benefit Analysis of Mixing Process in Anaerobic Digesters of Biogas Plants JF - Environmental and Climate Technologies N2 - 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. UR - https://doi.org/10.2478/rtuect-2020-0105 KW - Anaerobic digester KW - biomass KW - computational fluid dynamics (CFD) KW - Cost-Benefit Analysis (CBA) KW - evaluation criteria KW - flow velocity KW - full scale biogas digester KW - mixing KW - propeller Y1 - 2020 UR - https://doi.org/10.2478/rtuect-2020-0105 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9274 SN - 2255-8837 VL - 24 IS - 3 SP - 305 EP - 317 PB - De Gruyter Poland CY - Warsaw ER - TY - JOUR A1 - Dotzauer, Martin A1 - Pfeiffer, Diana A1 - Lauer, Markus A1 - Pohl, Marcel A1 - Mauky, Eric A1 - Bär, Katharina A1 - Sonnleitner, Matthias A1 - Zörner, Wilfried A1 - Hudde, Jessica A1 - Schwarz, Björn A1 - Faßauer, Burkhardt A1 - Dahmen, Markus A1 - Rieke, Christian A1 - Herbert, Johannes A1 - Thrän, Daniela T1 - How to measure flexibility - Performance indicators for demand driven power generation from biogas plants JF - Renewable Energy N2 - 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. UR - https://doi.org/10.1016/j.renene.2018.10.021 KW - Demand-orientated power generation KW - Flexible bioenergy generation KW - Biogas plants KW - Flexibility indicators KW - Gas production modulation KW - Anaerobic digestion Y1 - 2018 UR - https://doi.org/10.1016/j.renene.2018.10.021 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9538 SN - 1879-0682 SN - 0960-1481 VL - 2019 IS - 134 SP - 135 EP - 146 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Conti, Fosca A1 - Saidi, Abdessamad A1 - Goldbrunner, Markus T1 - CFD Modelling of Biomass Mixing in Anaerobic Digesters of Biogas Plants JF - Environmental and Climate Technologies N2 - 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. UR - https://doi.org/10.2478/rtuect-2019-0079 KW - Anaerobic digester KW - biomass KW - cellulose KW - computational fluid dynamics (CFD) KW - full scale biogas digester KW - laboratory digester KW - mixing KW - rheology KW - viscosity Y1 - 2019 UR - https://doi.org/10.2478/rtuect-2019-0079 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9544 SN - 2255-8837 VL - 23 IS - 3 SP - 57 EP - 69 PB - RTU Press CY - Riga ER - TY - JOUR A1 - Reiter, Christoph A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Hanby, Victor Ian T1 - A Dynamic Multinode Model for Component-Oriented Thermal Analysis of Flat-Plate Solar Collectors JF - Journal of Solar Energy N2 - 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. UR - http://dx.doi.org/10.1155/2015/280694 Y1 - 2015 UR - http://dx.doi.org/10.1155/2015/280694 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-9637 SN - 2314-6230 VL - 2015 PB - Hindawi Publ. CY - New York; Cairo ER - TY - JOUR A1 - Greßhake, Lukas A1 - Bosch, Stephan A1 - Tutunaru, Robin A1 - Holzhammer, Uwe T1 - What do you mean by ‘(un-)suitable’? Analysing the diversity of social acceptance towards the deployment of renewable energies in different landscapes JF - Journal of Land Use Science N2 - 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. UR - https://doi.org/10.1080/1747423X.2025.2499280 Y1 - 2025 UR - https://doi.org/10.1080/1747423X.2025.2499280 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-59512 SN - 1747-4248 SN - 1747-423X VL - 20 IS - 1 SP - 117 EP - 150 PB - Taylor & Francis CY - London ER - TY - CHAP A1 - Schmitt, David A1 - Reum, Tobias A1 - Summ, Thorsten A1 - Trinkl, Christoph A1 - Schrag, Tobias ED - Fink, Christian ED - Brunner, Christoph T1 - Investigation of the Flexibility Potential by Decoupling Building Mass and Room Temperature T2 - International Sustainable Energy Conference - Proceedings N2 - 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. UR - https://doi.org/10.52825/isec.v1i.1165 Y1 - 2024 UR - https://doi.org/10.52825/isec.v1i.1165 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-56543 SN - 2976-2030 PB - TIB Open Publishing CY - Hannover ER - TY - INPR A1 - Chaturvedi, Pushpendra Kr. A1 - Kumar, Nand A1 - Lamba, Ravita A1 - Mehta, Kedar T1 - Multi-objective optimization of glazing and shading configurations for visual, thermal, and energy performance of cooling dominant climatic regions of India T2 - Research Square N2 - 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. UR - https://doi.org/10.21203/rs.3.rs-4983831/v1 Y1 - 2024 UR - https://doi.org/10.21203/rs.3.rs-4983831/v1 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-57621 SN - 2693-5015 PB - Research Square CY - Durham ER - TY - JOUR A1 - Reum, Tobias A1 - Schmitt, David A1 - Summ, Thorsten A1 - Trinkl, Christoph A1 - Ochs, Fabian A1 - Schrag, Tobias T1 - Experimental analysis of parallel operation of two heat sources in a dual-source heat pump incorporating two compressors JF - International Journal of Refrigeration N2 - 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. UR - https://doi.org/10.1016/j.ijrefrig.2024.12.013 Y1 - 2024 UR - https://doi.org/10.1016/j.ijrefrig.2024.12.013 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-57723 SN - 1879-2081 SN - 0140-7007 VL - 2025 IS - 171 SP - 124 EP - 138 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mehta, Kedar A1 - Zörner, Wilfried T1 - Optimizing Agri-PV System: Systematic Methodology to Assess Key Design Parameters JF - Energies N2 - 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. UR - https://doi.org/10.3390/en18143877 Y1 - 2025 UR - https://doi.org/10.3390/en18143877 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-61136 SN - 1996-1073 VL - 18 IS - 14 PB - MDPI CY - Basel ER - TY - JOUR A1 - Laband, Dana Laureen A1 - Stöckl, Martin A1 - Mittreiter, Annedore A1 - Holzhammer, Uwe T1 - Barrier Analysis of Flexibilization of Cooling Supply Systems JF - Energies N2 - 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. UR - https://doi.org/10.3390/en18154133 Y1 - 2025 UR - https://doi.org/10.3390/en18154133 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-61098 SN - 1996-1073 VL - 18 IS - 15 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mehta, Kedar A1 - Wright, Andrew A1 - Brown, Neil A1 - Zörner, Wilfried T1 - Transitioning to Low-Carbon Heating: Decision-Making Approach for Cold Communities JF - Clean Energy N2 - 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. UR - https://doi.org/10.1093/ce/zkaf010 Y1 - 2025 UR - https://doi.org/10.1093/ce/zkaf010 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-58214 SN - 2515-396X VL - 9 IS - 4 PB - Oxford University Press CY - Oxford ER - TY - JOUR A1 - Werner, Melanie A1 - Ehrenwirth, Mathias A1 - Muschik, Sebastian A1 - Trinkl, Christoph A1 - Schrag, Tobias T1 - Operational experiences with a temperature-variable district heating network for a rural community JF - Chemical Engineering & Technology N2 - The potential of utilizing temperature-variable district heating systems in rural areas was investigated. A local district heating system in Germany and the related project NATAR are briefly described; measurement data is evaluated. Operational experiences with a seasonal temperature reduction and consequent advantages for different heat generation systems and heat storages are discussed. The analysis of measurement data reveals a high optimization potential for solar thermal systems in case of an integration both into a low- and a high-temperature storage. Furthermore, a combined heat-and-power plant in combination with a CO2 heat pump promises sector-coupling potential and high electricity self-consumption. UR - https://doi.org/10.1002/ceat.202100114 KW - district heating network KW - low temperature KW - sector coupling Y1 - 2021 UR - https://doi.org/10.1002/ceat.202100114 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-20824 SN - 0930-7516 VL - 46 IS - 3 SP - 482 EP - 490 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Slonski, Matthias A1 - Schrag, Tobias T1 - Linear optimisation of a settlement towards the energy-plus house standard JF - Energies N2 - 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. UR - https://doi.org/10.3390/en12020210 KW - efficiency KW - renewables KW - buildings KW - quarters KW - settlements KW - energy-plus house KW - simulation KW - optimisation Y1 - 2019 UR - https://doi.org/10.3390/en12020210 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-20861 SN - 1996-1073 VL - 12 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mehta, Kedar A1 - Mingaleva, Ekaterina A1 - Zörner, Wilfried A1 - Degembaeva, Nadira A1 - Baibagyshov, Ermek T1 - Comprehensive analysis of the energy legislative framework of Kyrgyzstan BT - Investigation to develop a roadmap of Kyrgyz renewable energy sector JF - Cleaner Energy Systems N2 - 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. UR - https://doi.org/10.1016/j.cles.2022.100013 KW - Central Asia KW - Energy policy KW - Energy legislation KW - Energy security KW - Kyrgyzstan KW - Renewable energies KW - Solar energy KW - Sustainable energy Y1 - 2022 UR - https://doi.org/10.1016/j.cles.2022.100013 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-29165 SN - 2772-7831 VL - 2022 IS - 2 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried T1 - Mapping Potential for Improving Rural Energy Services in Kyrgyzstan: Factors for Achieving Sustainable Development Goals in the Community Context JF - World N2 - Energy is a pivotal element for overall development. Therefore, affordable and clean energy for all (Sustainable Development Goal 7) is one of the important elements. Despite a suitable approach, Kyrgyzstan lags behind to achieve its Sustainable Development Goals by 2030. Improving access to energy can significantly impact the progress of many other sustainable development targets. However, access to reliable, sustainable, and adequate energy is a crucial task in rural Kyrgyzstan. Taking into consideration the energy situation and the importance of the availability of energy services, the overarching aim of the presented article is to map the potential of improving rural energy services to foster overall sustainable development goals. The article presents the most relevant information about rural energy usage behaviour based on three primary pillars: energy demand, energy carrier, and energy sources. In addition, the presented research article synthesises the key driving factors which have a direct or indirect impact on the energy services in rural areas. The summarised data displays a deep insight into a variety of complex and dynamic household energy consumption patterns. The article provides a potential solution nexus to foster improved energy services in rural Kyrgyzstan and therefore to foster the overall sustainable development in Kyrgyzstan. The findings of the article help to formulate a strategy to design rural energy services for policy makers and stockholders. UR - https://doi.org/10.3390/world3030032 KW - energy need KW - rural livelihood KW - energy poverty KW - energy services KW - sustainable energy transition KW - sustainable development goals KW - Kyrgyzstan KW - Central Asia Y1 - 2022 UR - https://doi.org/10.3390/world3030032 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-29518 SN - 2673-4060 VL - 3 IS - 3 SP - 586 EP - 606 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mehta, Kedar A1 - Zörner, Wilfried A1 - Greenough, Richard T1 - Residential Building Construction Techniques and the Potential for Energy Efficiency in Central Asia: Example from High-Altitude Rural Settlement in Kyrgyzstan JF - Energies N2 - 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. UR - https://doi.org/10.3390/en15238869 KW - Central Asia KW - earthen high-altitude houses KW - building construction KW - vernacular buildings KW - energy efficiency KW - cold climate Y1 - 2022 UR - https://doi.org/10.3390/en15238869 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-29752 SN - 1996-1073 VL - 15 IS - 23 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bader, Tobias A1 - Brandmayr, Sebastian A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Hanby, Victor Ian T1 - Climate Specific Design and Effectiveness of Solar DEC-systems BT - a Methodological Zoning Approach JF - Energy Procedia N2 - 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. UR - https://doi.org/10.1016/j.egypro.2014.02.090 KW - Solar DEC-air-conditioning KW - methodological system design KW - worldwide transferabiltiy KW - climate driven design KW - system effectiveness Y1 - 2014 UR - https://doi.org/10.1016/j.egypro.2014.02.090 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-23614 SN - 1876-6102 N1 - Part of special issue: "Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)" VL - 2014 IS - 48 SP - 778 EP - 789 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Reiter, Christoph A1 - Brandmayr, Sebastian A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Hanby, Victor Ian T1 - Performance Optimisation of Polymeric Collectors by Means of Dynamic Simulation and Sensitivity Analysis JF - Energy Procedia N2 - 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. UR - https://doi.org/10.1016/j.egypro.2014.02.023 KW - mathematical model KW - simulation KW - flat-plate collector KW - collector efficiency KW - stagnation temperature KW - polymeric materials Y1 - 2014 UR - https://doi.org/10.1016/j.egypro.2014.02.023 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-23625 SN - 1876-6102 N1 - Part of special issue: "Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)" VL - 2014 IS - 48 SP - 181 EP - 191 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Ramm, Tobias A1 - Hammel, Carolina A1 - Klärner, Michael A1 - Kruck, Alfons A1 - Schrag, Tobias T1 - Energy storage and integrated energy approach for district heating systems T2 - Energy Procedia N2 - This paper deals with the potential of using the thermal storage capacities within local district heating systems to balance the low and medium voltage grids by the use of heat pumps (HP) and combined heat and power (CHP) plants. The state-of-the-ar of district heating systems as well as the coupling of the heat and power grid is discussed. The research work of the projec NATAR (local heating grids with lowered temperature as provider of balancing power) and the local heating grid of Dollnstein which serves as an use case, are further described. A first analysis of measured data of the district heating system indicates an optimisation potential regarding to the control strategy of the combined heat and power plant as well as the usage of the available thermal storage capacities. UR - https://doi.org/10.1016/j.egypro.2017.09.515 KW - district heating system KW - variable temperatures KW - low-exergy KW - heat pumps KW - coupled energy systems KW - balancing power Y1 - 2017 UR - https://doi.org/10.1016/j.egypro.2017.09.515 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-23501 SN - 1876-6102 VL - 2017 IS - 135 SP - 391 EP - 397 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Riess, Hermann A1 - Brandmayr, Sebastian A1 - Zörner, Wilfried A1 - Greenough, Richard T1 - Analysis of the mechanical behaviour of an all-round fully adhesive supported absorber JF - Energy Procedia N2 - 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. UR - https://doi.org/10.1016/j.egypro.2014.02.025 KW - Solar collector KW - Absorber KW - Thermal expansion KW - Deformation KW - Mechanical stress KW - Hyperstatic KW - Edge bond Y1 - 2014 UR - https://doi.org/10.1016/j.egypro.2014.02.025 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-23744 SN - 1876-6102 N1 - Part of special issue: "Proceedings of the 2nd International Conference on Solar Heating and Cooling for Buildings and Industry (SHC 2013)" VL - 2014 IS - 48 SP - 201 EP - 211 PB - Elsevier CY - Amsterdam ER -