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Setup for Long-Term Outdoor Testing of Optically Modified PV Modules Regarding their Thermal and Electrical Behavior Under Load
No full textOptical modifications of the light-facing side of photovoltaic (PV) modules can be used to increase their efficiency by implementing anti-reflective or anti-soiling properties or by achieving a reduction of the operating temperature. Furthermore, such front-optical modifications can be utilized to hybridize concentrating solar thermal systems and PV systems. In order to characterize such modifications correctly, special attention has to be paid to two points: the modules have to be operated under load to keep the cells at a realistic operating temperature, and high precision of the temperature measurement is required to quantify the potentially very small effects of the modifications (e.g., for radiative cooling decreases in operating temperature of less than 1 K have to be expected). In this paper, a setup is presented for testing front-optical modifications in fixed tilt configuration in Almería, Spain. The loading is achieved by the use of an electronic load and the precision of the temperature measurement is achieved by Platinum resistance temperature detectors (Pt100s) laminated into the modules in combination with high precision multimeters. To demonstrate the capabilities of the setup, exemplary measurement data is shown
Development of Procedures for a Regolith Experiment with Human-Robot Interaction at the Lunar South Pole for the LUNA Analog Facility
No full textThis paper addresses the preparation for future lunar missions by systematically analyzing potential off nominal risks astronauts may face during extravehicular activities (EVAs) and developing corresponding malfunction procedures to enhance crew safety and mission success. The research encompasses a fundamental risk assessment of a defined lunar mission sce- nario, identification and prioritization of critical risks, and the subsequent development of operational procedures to mitigate selected high-priority risks. Furthermore, the study evaluates the requirements for realistic simulation of these scenarios within the LUNA analog facility, aimed at training astronauts to respond effectively to off nominal events. The risk assessment method- ology involved comprehensive identification of off-nominal situ- ations through scenario analysis and brainstorming techniques, resulting in a structured flow chart representation of potential anomalies and their consequences. A comparative evaluation method was applied to estimate the likelihood and severity of consequences, enabling the classification of risks within a risk matrix framework. Seven off-nominal scenarios were selected based on combined risk levels and mission relevance, covering a spectrum of challenges from lunar environmental hazards to technological and human-robot interaction issues. Contrary to initial expectations, only one scenario was rated as high risk due to the comparative nature of the evaluation method. Nonetheless, this relative risk assessment provided a useful prioritization tool for procedural development. Following this, two malfunction procedures addressing “Cryobox temperature out of limit” and “Unplanned rover movement during EVA” were developed, incorporating all necessary operational steps. The iterative nature of procedure development is emphasized, with future revisions anticipated following validation phases. Simulation fidelity and validity within the LUNA analog facility were critically assessed to define the equipment and functional requirements for training effectiveness. Findings indicate that while certain advanced features, such as gravity off-loading and sophisticated sun simulators, could enhance fidelity, they are not essential for the validity of training simulations. Additionally, a stationary rover mock-up is necessary for scenarios involving unplanned rover movements and situational awareness training. Limitations include the binary evaluation of component impact without a gradation scale, highlighting an area for future im- provement. On top, future work includes the practical execution of training simulations incorporating the developed procedures, with campaign plans updated to include intentional failures. Comparative studies on simulation fidelity levels could elucidate the relationship between training realism and effectiveness. Nomi- nal procedures should be enhanced to incorporate comprehensive scientific tool usage and detailed sample inspection protocols, including temperature measurement and documentation using digital tools. In conclusion, this paper contributes to the body of knowledge on managing off-nominal risks in lunar EVAs and the development of astronaut training protocols using analog facilities. These insights support ongoing efforts in mission prepa- ration, ultimately advancing human exploration and utilization of the Moon
A Serious Gaming Schematic Design for Efficient and Application-Specific Chatbot Validation on the Example of Air Traffic Control
No full textThe prevalence of chatbot systems is on the rise globally. However, it remains challenging to conduct a comprehensive evaluation of their use cases outside of the domain of so-called service chatbots. This is particularly evident in the context of air traffic control, where safety concerns necessitate a high degree of reliability and accuracy. In this domain, the validation of a chatbot solely based on its performance is impractical and difficult to execute, given the limitations of current large language model technologies, which lack deterministic behavior. To address this challenge, this study proposes a novel approach to validate air traffic control chatbots through the use of serious gaming. By simplifying the real-world scenario, serious gaming offers cost-effective and safe means of testing unproven designs without the need for operational experts. To this end, a methodology integrating standard chatbot evaluation strategies with the european operational concept validation methodology is developed. This methodology was applied to assess the quality of a chatbot that assumes the role of a tower controller. It was found that a chatbot system could be validated with reduced effort using serious gaming. A total of 107 students took part in three distinct studies. The air traffic control chatbot was usable, achieving an aboveaverage system usability score of 85 of 100 when tested with the latest version of the game designed for the proposed validation environment
Innovative approaches to waste heat recovery: Coupling high temperature vapour compression heat pumps with salt hydrate thermochemical systems
No full textEfficient utilization of waste heat is a crucial method to meet global energy demands and carbon neutrality. High Temperature mechanical Heat Pumps (HTHPs) are vital in this context but are limited by evaporator temperature constraints. This study proposes an innovative approach to upgrading and reintegrating waste heat from HTHPs (105–140 °C) by coupling them with a dual reactor salt hydrate based Thermo-Chemical Energy Storage (TCES) system. Operating in a quasi-continuous mode, the system utilizes the waste heat from the HTHP to drive hydration (discharge) in one reactor and dehydration (charge) in another. The key to heat upgrading lies in the evaporator of the TCES system, which governs system performance. Therefore, an empirical relation has been developed to determine its optimum temperature as a function of waste heat temperature, heat upgrade temperature, and the thermal properties of the salt hydrate. Subsequently, the system performance with K2CO3-H2O was assessed by applying the first law of thermodynamics, with the evaporator temperature of the TCES varied from 100 °C to 90 °C. Lowering the evaporator temperature of the TCES enhances thermal output but is constrained by the HTHP's temperature requirements. The system delivers 55.4 kW per kg/s of air with a heat upgrade efficiency of 45.7 %, using waste heat at 140 °C and the evaporator of the TCES at 100 °C. This study attempts to establish a framework for designing efficient thermally driven cascaded heat pumps
A 3D battery model incorporating Si particle expansion induced electrolyte motion
No full textSilicon is frequently used as active material in the negative electrode of Lithium-ion batteries as it provides substantial improvements in the energy density compared to conventional graphite electrodes. Due to large volume changes during cycling, the Si content in state-of-the-art Si/graphite composite electrodes is often rather low. As significantly higher Si contents are desirable, the effects of structural changes that influence ion and electron transport and, thus, battery performance and degradation have to be analyzed. An aspect which is often overlooked is the displacement of electrolyte into the void regions of the cells.
In our work, we developed a homogenized electrochemical model of Li-ion batteries including single phase flow through the porous electrode media to account for electrolyte motion. The considered Darcy flow is generated by the change in active material volume during battery operation. In our studies, we keep track of the amount of displaced electrolyte and the Li concentration therein. Considering different material compositions and cell designs highlights that the ratio of anode and cathode thickness and permeability are the dominant parameters determining the Li concentration in the displaced electrolyte volume.
The difference between inner and displaced electrolyte Li concentration results in a concentration gradient in outflow direction. While the accumulation or depletion of local Li concentration favors degradation during prolonged cycling, our simulations show that this effect can be mitigated by tuning the permeability
Optimizing Peak Age under Intermittent Satellite Connectivity and Store-and-Forward
Full text linkWe consider a real-time task-oriented application operating over an intermittently available satellite-based communication network, aiming to collect status updates generated by a remote sensing device. The system is modeled as a scheduling problem over a finite horizon, corresponding to the duration of the task, to minimize the peak Age of Information at the destination. The number of updates that can be transmitted is constrained by a transmission budget. Moreover, the status updates are subject to delays caused by the store-and-forward operation of the satellites, which may vastly vary depending on the network conditions. We investigate three levels of awareness regarding the connectivity conditions of the satellite network: (i) scheduling without any information about connectivity conditions, (ii) scheduling based solely on the current conditions, and (iii) scheduling based on full connectivity knowledge. The first case admits a relatively simple structure, for which a periodic transmission strategy is adopted. The latter two cases are formulated as semi-Markov decision processes and solved to obtain the optimal transmission scheduling policy. Simulation results demonstrate the impact of connectivity awareness on the application performance at the destination. Through a simple modeling approach, we provide first insights into the practically relevant setting of store-and-forward satellite architectures
Advances in high-temperature heat pump technologies for industrial process applications with large temperature glides: assessing the potential for carbon dioxide as a refrigerant
No full textIndustrial process heat users face great uncertainty due to the cost and complexity of transitioning to renewable energy sources. High-temperature heat pumps offer a promising solution due to the high COPs that can be achieved compared to electric heating. However, it can be difficult to identify which heat pump systems are most suitable for which applications. This is particularly true for transcritical heat pumps where the temperature glide in the gas cooler (equivalent to a condenser) is very high. This paper aims to quantify the potential decarbonisation impact that could be realised from the development of new CO2 high-temperature heat pump cycles with large temperature glides (>100 °C). To this end, this study identifies potential process applications, including suitable sink and source streams to supply the heat pump system, and discusses the opportunities and barriers for HTHP implementation. Thermodynamic models of three CO2 heat pump cycles were used to estimate the COPs and the carbon abatement potential for the identified applications. Drying applications such as for producing milk powder, starch and instant coffee, were identified as suitable applications and the COPs estimated based on the required process temperatures and available waste heat
The next Generation of DLR's C-band Transponders for Calibrating future SAR Systems - Status and Outlook
No full textSince more than 30 years the DLR SAR Calibration Center is active in the calibration of spaceborne SAR Systems. Three C-band transponders, named „Kalibri, and three remote-controlled corner reflectors were commissioned in 2014 and have been serving as central calibration field for ESA‘s Sentinel-1 mission. In order to be well prepared for the future, DLR intensifies its development activities for novel C-band transponders. The increasing complexity of modern SAR missions requires for suitable reference targets with state-of-the-art hardware. In this paper the current status of DLR’s C-band
transponder development including a roadmap is presented. Within the next years a new generation of innovative C-band transponders will be developed, in order to be well prepared for the calibration of future SAR missions