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%

The economic value of climate information

Fil: Bert, Federico Esteban. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; ArgentinaFil: Letson, David. University Of Miami. Rosenstiel School Of Marine Atmospheric Science. Meteorology And Physical Oceanography; Estados UnidosFil: Podesta, Guillermo. University Of Miami. Rosenstiel School Of Marine Atmospheric Science. Meteorology And Physical Oceanography; Estados Unido

La digitalización de la agricultura, proceso necesario para la transformación positiva de los sistemas alimentarios

La digitalización del sector agrario es un proceso que podría ofrecer beneficios tanto a nivel productivo como comercial; sin embargo, su expansión ha estado limitada por temas de conectividad y desconocimiento de uso. Por lo tanto, es necesario impulsar una agenda de digitalización en América Latina y El Caribe, para lograr una mayor adaptabilidad y aprovechamiento de las nuevas tecnologías por medio de el involucramiento de los actores del sector, la promoción de tecnologías adaptadas al contexto agrario, establecer resultados clave y acordar compromisos

Identifying the factors that determine ecosystem services provision in Pampean agroecosystems (Argentina) using a data-mining approach

Ecosystem services (ES) have become a key concept in the assessment of natural resources, as a way to connect human well-being and ecosystems degradation. However, ES quantification is considered a basic problem because provision varies considerably as a result of land use change and site-specific characteristics (i.e. climate, soil, topography, and time). Thus, more detailed studies are needed to assess whether these changes affect ecological variables. We explored the use of environmental and crop management variables in predicting the provision of four ES (soil C balance, soil N balance, N2O emission control and groundwater contamination control) in three agroecosystems located in the Pampa region (Argentina). Data-mining, represented by k-means cluster and classification trees, was used to identify the dependence of ES provision on the variation of both environmental and crop management factors. We used plot level crop management and environmental field information stored in a large database during a 10-year period. The k-means method selected five different clusters. The final configuration showed two contrasting clusters: one with the lowest ES provision, and another one with the highest ES provision. The five clusters were represented in the terminal nodes of the final classification tree. Regarding the predictive power of the variables, crop and year were the most important predictors. Then, differences observed in ES provision resulted from changes in land use (variable “crop”) and crop season (variable “year”). These results are meant to enlighten stakeholders in terms of how to manage Pampean agroecosystems in order to positively influence ES provision.Fil: Rositano, Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; ArgentinaFil: Bert, Federico Esteban. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Piñeiro, Gervasio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales y Ambiente. Cátedra de Ecología; ArgentinaFil: Ferraro, Diego Omar. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; 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

Digitalización agroalimentaria: Conceptos e ideas para la acción emergentes de diálogos amplios

Este documento expresa los principales conceptos emergentes de las presentaciones y diálogos suscitados durante la Semana de la Agricultura Digital. Los mismos se insertan y enriquecen el encuadre y lineamientos para la acción que IICA viene elaborando respecto a digitalización agroalimentaria. El documento se ofrece como una línea de base para interpretar el estado y proyección de la digitalización agroalimentaria y diseñar acciones para promoverla

Sistemas de producción de maíz: maíz temprano y tardío

En este artículo se describen las condiciones ambientales (con énfasis en el clima) que exploran los distintos sistemas y las implicancias que las mismas tienen sobre el rinde potencial, alcanzable y logrado del cultivo, y sobre su manejo.Fil: Bert, Federico Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; ArgentinaFil: Satorre, Emilio Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentin

Sistemas de producción de maíz: maíz temprano y tardío

En este artículo se describen las condiciones ambientales (con énfasis en el clima) que exploran los distintos sistemas y las implicancias que las mismas tienen sobre el rinde potencial, alcanzable y logrado del cultivo, y sobre su manejo.Fil: Bert, Federico Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; ArgentinaFil: Satorre, Emilio Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario; Argentina. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Producción Vegetal. Cátedra de Cerealicultura; Argentin

Trust levels toward health care and government: insights from TrustMe, an Italian cross-sectional study

Introduction: Negative trends of trust in governments have been described around the world. This study aimed to describe the distrust level in the National Health Service (NHS) and in governmental management of the pandemic, one year after the start of the COVID-19 vaccination campaign.  Methods: A survey was distributed in February 2022 among a convenience sample. Outcomes were measured through validated tools: Revised Health Care System Distrust Scale, and the COVID-SCORE-10 questionnaire. Associations were assessed using multiple linear regression models. Results: A total of 2111 questionnaires were collected (54.8% female, median age 43 years [IQR=34-50]). Distrust in the NHS had a median level of 12 [IQR=10-14], while trust in the government had a level of 47 [IQR=35-60]. COVID-19 vaccine hesitancy, high educational attainment, worse economic status, low conventional and digital health literacy, as well as the presence of conspiracy thoughts and distrust in the NHS were significantly associated with lower trust in government during the COVID-19 pandemic. Lack of trust in governmental actions, along with low education and health literacy, as well as the presence of conspiracy thoughts and worse perceptions of one's own health, were associated with greater distrust in the NHS. Conclusions: Overall, low levels of trust in both the government and the NHS have emerged. Since the determinants of reduced trust in institutions can be very diverse and that such levels of distrust after a pandemic can last for an entire generation, tailored interventions are needed to rebuild adequate levels of trust in institutions among the population