TY - JOUR A1 - Summ, Thorsten A1 - Ehrenwirth, Mathias A1 - Trinkl, Christoph A1 - Zörner, Wilfried A1 - Pischow, Kaj A1 - Greenough, Richard A1 - Oyinlola, Muyiwa T1 - Effect of argon concentration on thermal efficiency of gas-filled insulating glass flat-plate collectors JF - Applied Thermal Engineering N2 - Insulating glass flat-plate collectors can save cost by being produced quickly and automatically in insulated glass production facilities, and they can be filled with argon to reduce heat loss. During its lifetime, the collector is likely to lose argon because of gradual material degradation of the sealing. However, information on the influence of the argon concentration on the collector efficiency is limited. Therefore, the objective of this research work was to analyse this effect. A theoretical material property calculation of argon-air mixtures was carried out to determine the convective losses with variable argon concentrations. Thermal collector performance was measured experimentally using an outdoor solar tracker test rig. The results strongly suggest, that the influence of argon concentration on both the convective losses and the thermal efficiency is non-linear. The measurements revealed that an argon concentration of 90 % can increase average thermal performance by 6.7 ± 4.8 percentage points. An increase in argon concentration from 0 % to 50 % has almost twice the effect on average thermal efficiency as an increase from 50 % to 90 %. Concluding from these results, an argon leakage threshold of 2.5 percentage points per year is proposed to avoid disproportionate loss of efficiency over time. UR - https://doi.org/10.1016/j.applthermaleng.2023.120657 KW - Insulating glass KW - Flat-plate collector KW - Argon KW - Gas concentration KW - Efficiency measurement KW - Convective heat transfer Y1 - 2023 UR - https://doi.org/10.1016/j.applthermaleng.2023.120657 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-37875 SN - 1873-5606 SN - 1359-4311 VL - 2023 IS - 230, Part A PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Besner, Rebekka A1 - Mehta, Kedar A1 - Zörner, Wilfried T1 - How to Enhance Energy Services in Informal Settlements? BT - Qualitative Comparison of Renewable Energy Solutions JF - Energies N2 - More than half of the urban population of Sub-Saharan Africa lives in informal housing conditions. While urban areas are, in general, characterized by a high electrification rate, residents of informal settlements are still affected by energy poverty, the use of traditional energy sources and unreliable electricity supply. The aim of the study is to give an overview of different renewable-energybased solutions which are able to improve local energy provision. These are Solar Home Systems, Mini-Grids, and Energy-Hubs. The technologies are compared to another option for improving energy supply, namely Grid Expansion. The analysis is based on 24 Key Performance Indicators, which can be classified into technical, economic, environmental, social, and political dimensions. The selection of indicators is based on the challenges prevalent in informal settlements that impede a comprehensive, sustainable energy supply. The literature-based indices are used to determine which of the four technologies is a suitable solution for minimizing the challenges prevailing in informal settlements. The resulting matrix provides a holistic comparison and serves as a decision aid in selecting the appropriate technology for future projects in informal settlements, depending on local conditions and the needs of the population. The results show that the Energy-Hub is a valid alternative for energy supply improvement in Informal Settlements. UR - https://doi.org/10.3390/en16124687 KW - informal settlements KW - energy access KW - Sub-Saharan Africa KW - Energy-Hub KW - Mini-Grid Y1 - 2023 UR - https://doi.org/10.3390/en16124687 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-37319 SN - 1996-1073 VL - 16 IS - 12 PB - MDPI CY - Basel ER - TY - JOUR A1 - El Makroum, Reda A1 - Khallaayoun, Ahmed A1 - Lghoul, Rachid A1 - Mehta, Kedar A1 - Zörner, Wilfried T1 - Home Energy Management System Based on Genetic Algorithm for Load Scheduling: A Case Study Based on Real Life Consumption Data JF - Energies N2 - This paper proposes a home energy management system able to achieve optimized load scheduling for the operation of appliances within a given household. The system, based on the genetic algorithm, provides recommendations for the user to improve the way the energy needs of the home are handled. These recommendations not only take into account the dynamic pricing of electricity, but also the optimization for solar energy usage as well as user comfort. Historical data regarding the times at which the appliances have been used is leveraged through a statistical method to integrate the user’s preference into the algorithm. Based on real life appliance consumption data collected from a household in Morocco, three scenarios are established to assess the performance of the proposed system with each scenario having different parameters. Running the scenarios on the developed MATLAB script shows a cost saving of up to 63.48% as compared to a base scenario for a specific day. These results demonstrate that significant cost saving can be achieved while maintaining user comfort. The addition of supplementary shiftable loads (i.e., an electric vehicle) to the household as well as the limitations of such home energy management systems are discussed. The main contribution of this paper is the real data and including the user comfort as a metric in in the home energy management scheme. UR - https://doi.org/10.3390/en16062698 KW - home energy management KW - load scheduling KW - genetic algorithm KW - user comfort Y1 - 2023 UR - https://doi.org/10.3390/en16062698 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-32284 SN - 1996-1073 VL - 16 IS - 6 PB - MDPI CY - Basel ER - TY - JOUR A1 - Bazzi, Ahmed A1 - El Hafdaoui, Hamza A1 - Khallaayoun, Ahmed A1 - Mehta, Kedar A1 - Ouazzani, Kamar A1 - Zörner, Wilfried T1 - Optimization Model of Hybrid Renewable Energy Generation for Electric Bus Charging Stations JF - Energies N2 - This paper introduces a comprehensive approach for sizing grid-connected hybrid renewable energy systems tailored for electric bus fleet operations. The study involves two main steps. First, a mathematical model that optimizes the configuration of such systems by considering daily electric bus consumption, solar irradiance, wind speed, and biomass potential is formulated. The model utilizes Pareto frontier multi-objective optimization to minimize the net present cost, the cost of energy, and greenhouse gas emissions. Second, the model is rigorously applied and tested in a real-world case study in Fez, Morocco, using HOMER Pro; the case study centers on the daily energy requirements of the buses, estimated at 2.5 megawatt hours per day, with a peak demand of 345 kilowatts. Two scenarios are explored, revealing a discernible trade-off dilemma between the full hybrid renewable energy scenario (Scenario 1) and the grid-connected hybrid renewable energy scenario (Scenario 2). In Scenario 2, the grid-connected hybrid renewable energy system demonstrates a notable 42.8% reduction in the net present cost, totaling USD 984,624. Similarly, the levelized cost of energy experiences a significant decrease, reaching approximately 0.08 USD/kWh, marking a 38.1% reduction. However, this apparent economic advantage is juxtaposed with a critical consideration—an increase in greenhouse gas emissions from null to 330,418 kg/year. UR - https://doi.org/10.3390/en17010053 KW - electric buses KW - HOMER KW - on-site renewable energy generation KW - sustainable transport KW - hybrid renewable energy generation KW - grid-connected renewable energy system KW - electric bus charging station Y1 - 2023 UR - https://doi.org/10.3390/en17010053 UR - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:573-47109 SN - 1996-1073 VL - 17 IS - 1 PB - MDPI CY - Basel ER - 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 - 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 -