TY - JOUR A1 - Mehta, Kedar A1 - Zörner, Wilfried T1 - Cracking the code: mapping residential building energy performance in rural Central Asia through building typologies JF - SN Applied Sciences N2 - 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. UR - https://doi.org/10.1007/s42452-023-05607-1 Y1 - 2023 UR - https://doi.org/10.1007/s42452-023-05607-1 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-41536 SN - 2523-3971 VL - 5 IS - 12 PB - Springer Nature CY - Cham ER - TY - JOUR A1 - Summ, Thorsten A1 - Oyinlola, Muyiwa A1 - Khattak, Sanober A1 - Trinkl, Christoph A1 - Zörner, Wilfried T1 - Statistical analysis of solar thermal collectors in the Solar Keymark Database JF - Sustainable Energy Technologies and Assessments N2 - 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. UR - https://doi.org/10.1016/j.seta.2023.103581 Y1 - 2023 UR - https://doi.org/10.1016/j.seta.2023.103581 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-43981 SN - 2213-1396 VL - 2024 IS - 61 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Mehta, Kedar A1 - Zörner, Wilfried T1 - Crop selection in Agri-PV: international review based strategic decision-making model JF - Solar Compass N2 - 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. UR - https://doi.org/10.1016/j.solcom.2025.100143 Y1 - 2025 UR - https://doi.org/10.1016/j.solcom.2025.100143 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-62476 SN - 2772-9400 VL - 2025 IS - 16 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Häring, Georg A1 - Trinkl, Christoph A1 - Zörner, Wilfried ED - Der Präsident der Hochschule für angewandte Wissenschaften FH Ingolstadt, T1 - Messtechnische Analyse der Grundwasserwärmepumpenanlage in einem Büro- und Produktionsgebäude N2 - In einer messtechnischen Untersuchung wurde vom KOMPETENZFELD ERNEUERBARE ENERGIEN die Leistungsfähigkeit eines grundwassergespeisten Heiz- und Kühlsystems mit Wärmepumpen in einem Büro- und Produktionsgebäude analysiert und bewertet. Dazu wurde eine umfängliche energetische Bilanzierung von Gebäudetechnik und Gebäude vorgenommen. Innerhalb des mehrjährigen Untersuchungszeitraumes konnten umfangreiche Erkenntnisse über die Effizienz und Arbeitsweise der Heiz- und Kühlanlage gewonnen werden. Dabei wurden eine Reihe von Problemstellungen im realen Anlagenbetrieb identifiziert sowie das Gesamtsystem auf Basis der Messergebnisse optimiert. Um die praxisrelevanten Forschungsergebnisse in zukünftigen innovativen Gebäudetechnikkonzepten einfließen zu lassen wurden konkrete Handlungsempfehlungen für die Planungs-, die Inbetriebnahme- und Einregulierungsphase sowie für die Betriebsführung abgeleitet. T3 - Arbeitsberichte - Working Papers - 21 KW - Wärmepumpe Y1 - 2011 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-373 SN - 1612-6483 PB - Technische Hochschule Ingolstadt CY - Ingolstadt ER - TY - JOUR A1 - Rouegui, Meryem A1 - Bellabair, Hind A1 - El Asli, Abdelghani A1 - Amar, Amine A1 - Zörner, Wilfried A1 - Rachidi, Fouad A1 - Lghoul, Rachid T1 - Bio-Methanization of Sheep Manure and Beet Waste in the Meknes–Fès Region, Morocco: Effects of Pretreatment and Machine Learning Applications for Biochemical Methane Potential Prediction JF - Recycling N2 - 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. UR - https://doi.org/10.3390/recycling10060213 Y1 - 2025 UR - https://doi.org/10.3390/recycling10060213 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-64862 SN - 2313-4321 VL - 10 IS - 6 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mehta, Kedar A1 - Jain, Rushabh Bansilal A1 - Zörner, Wilfried T1 - Agrivoltaics Around the World: Potential, Technology, Crops and Policies to Address the Energy–Agriculture Nexus for Sustainable and Climate-Resilient Land Use JF - Energies N2 - 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. UR - https://doi.org/10.3390/en18246417 Y1 - 2025 UR - https://doi.org/10.3390/en18246417 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-65288 SN - 1996-1073 VL - 18 IS - 24 PB - MDPI CY - Basel ER - TY - JOUR A1 - Mehta, Kedar A1 - Lwakatare, Bertha A1 - Zörner, Wilfried A1 - Ehrenwirth, Mathias T1 - Mini-grid performance in Sub-Saharan Africa: case studies from Tsumkwe and Gam, Namibia JF - Sustainable Energy Research N2 - This paper investigates the performance analysis and operational challenges of mini-grids in Sub-Saharan Africa, focusing on the Tsumkwe and Gam mini-grids, the only officially recognized mini-grids in Namibia. The study addresses a critical gap in understanding mini-grid efficiency, technical difficulties, and future potential. The key research questions focus on assessing mini-grid performance, identifying technical and operational challenges, quantifying the relationship between electricity demand and supply, and providing recommendations for enhancing rural electrification through mini-grids. These insights are crucial for evaluating the effectiveness of mini-grids in the African context and understanding their role in advancing rural electrification. By using a mixed-method approach, the research combines quantitative and qualitative data to offer a comprehensive analysis of these two mini-grid systems of Namibia. The data collected from 2017 to 2022 include metrics on energy supply, consumption, photovoltaic generation, community load, and meteorological conditions. Qualitative insights were gathered through field visits, surveys, and interviews with mini-grid operators, allowing for a thorough examination of community perspectives, operational issues, and technical performance. The findings reveal that the Tsumkwe mini-grid has seen a decline in efficiency due to maintenance problems and battery overheating, while the Gam mini-grid, initially oversized, now struggles with increased demand and new connections. This study provides the first detailed technical insights, identifies consumer archetypes, and evaluates the energy dynamics of mini-grids in Namibia. Recommendations include improved maintenance protocols, advanced battery management, and enhanced data monitoring. By analyzing Tsumkwe and Gam, this paper offers valuable lessons for mini-grid development in Sub-Saharan Africa, stressing the need for continuous evaluation and strategic improvements to achieve sustainable rural electrification. UR - https://doi.org/10.1186/s40807-025-00174-y Y1 - 2025 UR - https://doi.org/10.1186/s40807-025-00174-y UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-65316 SN - 2731-9237 VL - 12 IS - 1 PB - SpringerOpen CY - Singapore ER - TY - JOUR A1 - Mehta, Kedar A1 - Ehrenwirth, Mathias A1 - Zörner, Wilfried A1 - Greenough, Richard T1 - Need of energy transition at roof of the world BT - Correlative approach to interpret energy identity of high-altitude Central Asian communities JF - Energy for Sustainable Development UR - https://doi.org/10.1016/j.esd.2023.101271 Y1 - 2023 UR - https://doi.org/10.1016/j.esd.2023.101271 SN - 2352-4669 SN - 0973-0826 VL - 2023 IS - 76 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ngetuny, Joshua Kiplagat A1 - Baldauf, Tobias A1 - Zörner, Wilfried T1 - Evaluating Feedstock Pretreatment Methods to Unlock Co-Digestion in Small-Scale Biogas Systems: A Multi-Criteria Approach to System Integration and Decision Making JF - Energies N2 - Small-scale biogas plants in developing countries present a viable alternative to traditional polluting energy sources, particularly in rural and underserved communities. These systems typically rely on locally sourced livestock manure; however, inconsistent supply often results in underfeeding, reduced biogas production, and, in many cases, system abandonment. Co-digestion with crop residues presents a promising strategy to enhance feedstock availability and system resilience. However, the recalcitrant nature of lignocellulosic biomass and limited access to suitable pretreatment technologies have constrained its adoption. This paper evaluates feasible pretreatment methods for integrating crop residues, especially straw, into small-scale biogas systems. Using the Analytic Hierarchy Process (AHP), pretreatment methods are assessed based on five criteria: (i) technology simplicity, (ii) energy requirements, (iii) capital and operational costs, (iv) effectiveness, and (v) environmental impact. The analysis identifies microbial pretreatment using the liquid fraction of digestate, combined with mechanical size reduction, as the most suitable approach for small-scale implementation, utilizing low-cost, simplified mechanical devices adaptable to various crop residues with minimal energy input. A conceptual design of a demonstration plant is proposed to validate this integrated pretreatment approach and assess its impact on biogas yield, system performance, and technology adoption. The design incorporates an on-site digestate separation unit to supply microbial inoculum and emphasizes simplicity and cost-effectiveness in material handling and energy use. Pilot trials are proposed to evaluate key performance indicators, including specific methane yield (LCH4/gVS added), volatile solids reduction (%), and methane content increase (%), ensuring evidence-based adoption and practical applicability of the design. UR - https://doi.org/10.3390/en19051303 Y1 - 2026 UR - https://doi.org/10.3390/en19051303 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-67479 SN - 1996-1073 VL - 19 IS - 5 PB - MDPI CY - Basel ER - TY - JOUR A1 - Ngetuny, Joshua Kiplagat A1 - Baldauf, Tobias A1 - Zörner, Wilfried T1 - Optimizing Feedstock Selection for Sustainable Small-Scale Biogas Systems Using the Analytic Hierarchy Process JF - Energies N2 - Small-scale biogas systems can play a pivotal role in sustainable energy provision, particularly in developing countries. However, their dependence on livestock manure as the only feedstock poses challenges to their adoption and long-term viability. This often leads to insufficient biogas production and plant abandonment. This study proposes co-digestion of livestock manure with other farm residues to enhance the technical sustainability of small-scale biogas systems by ensuring adequate and consistent biogas production throughout the plant’s lifespan, minimizing the risks associated with reliance on a single feedstock. A novel feedstock selection approach is developed using the Analytic Hierarchy Process (AHP), a multicriteria decision-making method, to prioritize feedstocks based on adequacy, supply consistency, and logistical ease. AHP is chosen due to its capability to handle both quantitative and qualitative evaluation criteria. This approach is applied to the Fès-Meknès region of Morocco, which offers abundant livestock and crop residues alongside product utilization pathways. The prioritization and ranking of the potential feedstocks identified in the region reveals cattle manure as the top-ranked feedstock due to its consistent supply and ease of collection, followed by straw, valued for its storability and nutrient stability. Sheep, horse, and chicken manure ranked third, fourth, and fifth, respectively, while household food waste and fruit and vegetable residues, limited by seasonality and perishability, were ranked lower. Based on these findings, co-digestion of cattle manure and straw is proposed as a sustainable strategy for small-scale biogas plants in Fès-Meknès, addressing feedstock shortages, enhancing biogas production, and reducing plant abandonment. This approach strengthens technical sustainability and promotes the broader adoption of biogas technologies in developing countries. UR - https://doi.org/10.3390/en18071739 Y1 - 2025 UR - https://doi.org/10.3390/en18071739 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-57915 SN - 1996-1073 VL - 18 IS - 7 PB - MDPI CY - Basel ER - TY - JOUR A1 - Ngetuny, Joshua Kiplagat A1 - Hsaine, Jalal A1 - Mabrouki, Abdelaalim A1 - Rachidi, Fouad A1 - El Asli, Abdelghani A1 - Zörner, Wilfried T1 - Assessment of agricultural residues for small-scale biogas plants and adoption drivers: a case study of the Fès-Meknès region in Morocco JF - Biomass Conversion and Biorefinery N2 - Small-scale biogas systems hold promise as reliable renewable energy sources in developing nations; however, adequate and consistent supply of feedstock remains a challenge. Agricultural residue, due to their lack of competition with food crops for resources, is touted as a dependable feedstock choice. This article therefore examines agricultural residues as potential biogas plant feedstocks in the Fès-Meknès region of Morocco, using a structured farm survey to evaluate livestock types, crop varieties, and residue utilization. Additionally, the study explores the challenges and drivers influencing biogas technology adoption in Morocco. Findings indicate a predominance of small-scale farms with livestock (averaging 11 cattle, 45 sheep, and 20 chicken) and mainly subsistence crop production, making these farms suitable candidates for small-scale biogas plants. Key barriers to adoption include a lack of awareness about the technology, along with technical and financial constraints. However, raising awareness, establishing demonstration plants, and offering financial and non-financial incentives are identified as potential drivers of adoption. This research provides a foundation for implementing biogas technologies in the case study area and other developing nations, guiding researchers and governmental and non-governmental organizations in disseminating small-scale biogas systems as a reliable energy source and a method for converting agricultural residues into sustainable energy (biogas) and fertilizer. Graphical Abstract UR - https://doi.org/10.1007/s13399-024-06443-y Y1 - 2025 UR - https://doi.org/10.1007/s13399-024-06443-y UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-55523 SN - 2190-6815 VL - 15 IS - 22 SP - 29207 EP - 29223 PB - Springer CY - Berlin ER -