A Thermal-Hydraulic Model for the Stagnation of Solar Thermal Systems with Flat-Plate Collector Arrays

Stagnation is the transient state of a solar thermal system under high solar irradiation where the useful solar gain is zero. Both flat-plate collectors with selective absorber coatings and vacuum-tube collectors exhibit stagnation temperatures far above the saturation temperature of the glycol-based heat carriers within the range of typical system pressures. Therefore, stagnation is always associated with vaporization and propagation of vapor into the pipes of the solar circuit. It is therefore essential to design the system in such a way that vapor never reaches components that cannot withstand high temperatures. In this article, a thermal-hydraulic model based on the integral form of a two-phase mixture model and a drift-flux correlation is presented. The model is applicable to solar thermal flat-plate collectors with meander-shaped absorber tubes and selective absorber coatings. Experimental data from stagnation experiments on two systems, which are identical except for the optical properties of the absorber coating, allowed comparison with simulations carried out under the same boundary conditions. The absorber of one system features a conventional highly selective coating, while the absorber of the other system features a thermochromic coating, which exhibits a significantly lower stagnation temperature. Comparison of simulation results and experimental data shows good conformity. This model is implemented into an open-source software tool called THD for the thermal-hydraulic dimensioning of solar systems. The latest version of THD, updated by the results of this article, enables planners to achieve cost-optimal design of solar thermal systems and to ensure failsafe operation by predicting the steam range under the initial and boundary conditions of worst-case scenarios

Performance Evaluation of an Evacuated Tube Collector with a Low-Cost Diffuse Reflector

In order to increase the overall solar energy gain of evacuated tube collectors, rear‐side reflectors are used. In this way, the otherwise unused incident radiation between the tubes can be reflected back to the absorber, and the performance of the collector can be improved. In this paper, the use of a low‐cost, diffusely reflecting, trapezoidal roof covering made from a galvanized metal sheet is investigated and compared to a high‐quality, specularly reflecting plane reflector made of aluminum. For this purpose, ray‐tracing analysis and TRNSYS simulations were carried out. In the ray‐tracing analysis, the experimentally determined zero‐loss collector efficiency η0 as well as the incident angle modifiers for each reflector can be reproduced with an error lower than 7.5%. Thermal system simulations show that the performance of both reflectors is comparable. The use of the low‐cost reflector leads to an increase in annual collector output of around 30% compared to an increase with the specular reflector of around 33%. Considering a typical domestic hot water system, both reflectors enable an increase in the solar annual yield of approx. 11%

Designing a Messaging Strategy to Improve Information Security Policy Compliance

Lack of employee compliance with information security policies is a key factor driving security incidents. Information security practitioners struggle to enforce policy compliance while employees try to curtail controls in favor of expediency and other perceived business and personal goals. This research-in-progress project utilizes the Design Science Research framework to develop an intervention based on a novel messaging strategy that aims to help information security practitioners improve employees’ behaviors through intrinsic motivation, thus increasing compliance with information security policies

Psychological science in Argentina: current state & future directions

Psychology was internationally developed as a scientific discipline. However, there continues to be a bias towards thepublication of research with Western English?speaking samples. In consequence, it is important to understand what chal-lenges non-English speaking countries are facing in their ability to contribute their research. Considering this, the goal ofthis article is to present an overview of the factors that may affect the development of scientific psychology in Argentina,including the professional practice of psychology, the teaching of psychology in higher education, and obstacles facedby graduate students who pursue research careers. Reviewing these topics will allow us to present the current state ofpsychological science in Argentina, and to propose future directions for scientific development.Fil: Giovannetti, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET; Argentina. Universidad de Buenos Aires. Facultad de Psicología; ArgentinaFil: Yomha Cevasco, Jazmin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Psicología; ArgentinaFil: Acosta Buralli, Karen Elin. Universidad de Buenos Aires. Facultad de Psicología; Argentin

Heat pipe collectors with overheating prevention in a cost-optimized system concept: Monitoring of system performance and stagnation loads under real conditions

Heat pipe collectors can significantly reduce stagnation loads in solar thermal systems due to their thermophysical properties. The paper experimentally investigates a novel system concept based on both evacuated tube collectors and flat-plate collectors with overheating prevention. Due to the resulting temperature limitation in the collector, the use of polymeric pipes as well as a significantly downsized expansion volume is possible. We implemented this concept in five demonstration plants and monitored their behavior over more than one year of operation. Both domestic hot water systems and combi-systems with space heating support in residential and office buildings are under consideration. The measured collector performance in all the systems matches the theoretical collector efficiency curve with a maximum deviation of five percentage points. Depending on the individual system configurations, the specific annual yield ranges between 174 kWh/m² and 445 kWh/m². During stagnation, we report a maximum temperature between 105 °C and 127 °C. In comparison to state-of-the-art systems, the maximum temperature in the solar circuit is 80–100 K lower and evaporation does not occur. The approach leads to reductions in investment costs of up to 16% and can significantly decrease the annual maintenance effort. Assuming a system lifetime of 25 years, we estimate a cost reduction of up to 22% in Levelized Cost of Heat (LCoH) compared to common system configurations

Impact of an Individualized Cognitive Training Intervention in Preschoolers from Poor Homes

Over the last few decades, different interventions were shown to be effective in changing cognitive performance in preschoolers from poor homes undertaking tasks with executive demands. However, this evidence also showed that not all children included in the intervention groups equally increased their performance levels, which could be related to individual and contextual variability. The present study aimed to explore the impact of a computerized cognitive training intervention with lab-based tasks in preschoolers from Unsatisfied Basic Needs (UBN) homes under the consideration of their baseline performance. In the context of a randomized controlled trial design, different interventions were administered to children according to their baseline performance in a variety of cognitive tasks (i.e., executive attention, inhibitory control, working memory, and planning demands). The results showed different patterns of impact on performance depending on the experimental group, supporting the importance of considering individual and contextual differences in the design of interventions aimed at optimizing executive functions in poverty-impacted sample populations in early stages of development.Fil: Giovannetti, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET; ArgentinaFil: Pietto, Marcos Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET; ArgentinaFil: Segretin, María Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET; ArgentinaFil: Lipina, Sebastián Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET; Argentin

Solar thermal component activation

Wall and roof components made of steel sandwich elements are firmly established in industrial and commercial construction. They are cost-effective and characterized by excellent physical properties. Here, hybrid approaches from heating- and cooling ceiling construction were examined for the solar thermal activation of sandwich elements. Besides the implementation of the solar components, the connection to and the optimization of the system technology was focused. In addition, alternative piping materials were investigated numerically and experimentally. The performance as well as the static and thermo-hydraulic behavior of the new active components were simulatively and experimentally examined, and the economic viability of the variants was also checked. With the newly developed solar sandwich elements, an overall energy concept was developed with connection variants to the building services system, control and storage technology. Steel sandwich elements with mineral fiber core are well suited for the hidden integration of component parts such as pipe registers and heat conducting plates. The functionality of the component has been proven, the implementation of heat exchanger leads to considerable heat gains. In combination with a brine-to-water heat pump system, the solar panel can provide for a more sustainable operation and a significant size reduction of the geothermal source

Optimizing quantum-enhanced Bayesian multiparameter estimation in noisy apparata

Achieving quantum-enhanced performances when measuring unknown quantities requires developing suitable methodologies for practical scenarios, that include noise and the availability of a limited amount of resources. Here, we report on the optimization of quantum-enhanced Bayesian multiparameter estimation in a scenario where a subset of the parameters describes unavoidable noise processes in an experimental photonic sensor. We explore how the optimization of the estimation changes depending on which parameters are either of interest or are treated as nuisance ones. Our results show that optimizing the multiparameter approach in noisy apparata represents a significant tool to fully exploit the potential of practical sensors operating beyond the standard quantum limit for broad resources range

Non-asymptotic Heisenberg scaling: experimental metrology for a wide resources range

Adopting quantum resources for parameter estimation discloses the possibility to realize quantum sensors operating at a sensitivity beyond the standard quantum limit. Such approach promises to reach the fundamental Heisenberg scaling as a function of the employed resources $N$ in the estimation process. Although previous experiments demonstrated precision scaling approaching Heisenberg-limited performances, reaching such regime for a wide range of $N$ remains hard to accomplish. Here, we show a method which suitably allocates the available resources reaching Heisenberg scaling without any prior information on the parameter. We demonstrate experimentally such an advantage in measuring a rotation angle. We quantitatively verify Heisenberg scaling for a considerable range of $N$ by using single-photon states with high-order orbital angular momentum, achieving an error reduction greater than $10$ dB below the standard quantum limit. Such results can be applied to different scenarios, opening the way to the optimization of resources in quantum sensing