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Sustainable development reached a new energy paradigm in recent decades, by promoting renewable generation technologies. The present study performs a techno-economic analysis of several hybrid energy systems that combine wind generators, photovoltaic systems, hydrokinetic turbines, lead acid batteries, and diesel generators in southern Ecuador. From real data, the sizing optimization of each renewable system was done under three proposed energy control algorithms. Then, the combinations of renewable systems are compared based on costs, energy, and environment. Additionally, this study includes several sensitivity analyzes varying the cost of the components and fuel, minimum state of charge in batteries, scaled electric load and time step to better understand the impact caused in each renewable hybrid system. The results show that a system composed of three renewable sources under load following and cycle charging energy controls, is cheaper and less polluting with respect to any combination of sources proposed. In addition to this, the systems that include photovoltaic systems and diesel generators present lower cost, 0.36 US$/kWh in the best case. To reduce the operability of the diesel generator, load following energy control is recommended. However, if diesel generator is removed, the resulting cost of 100% renewable systems increases considerably, reaching 0.88 US$/kWh. The results also show that, the variation in the capital cost of the components is directly proportional to the net present cost and cost of energy variation. Moreover, it is possible to reduce the cost of the system by discharging the batteries below their minimum state of charge. Finally, the results are more accurate when using a time step of 5 minutes.

This research aims to show the positive and negative indirect effects of COVID-19 on the environment, particularly in the most affected countries such as China, USA, Italy, and Spain. Our research shows that there is a significant association between contingency measures and improvement in air quality, clean beaches and environmental noise reduction. On the other hand, there are also negative secondary aspects such as the reduction in recycling and the increase in waste, further endangering the contamination of physical spaces (water and land), in addition to air. Global economic activity is expected to return in the coming months in most countries (even if slowly), so decreasing GHG concentrations during a short period is not a sustainable way to clean up our environment.

AbstractTropical glacier melt provides valuable water to surrounding communities, but climate change is projected to cause the demise of many of these glaciers within the coming century. Understanding the future of tropical glaciers requires a detailed record of their thicknesses and volumes, which is currently lacking in the Northern Andes. We calculate present-day (2015–2021) ice-thicknesses for all glaciers in Colombia and Ecuador using six different methods, and combine these into multi-model ensemble mean ice thickness and volume maps. We compare our results against available field-based measurements, and show that current ice volumes in Ecuador and Colombia are 2.49 ± 0.25 km3and 1.68 ± 0.24 km3respectively. We detected no motion on any remaining ice in Venezuela. The overall ice volume in the region, 4.17 ± 0.35 km3, is half of the previous best estimate of 8.11 km3. These data can be used to better evaluate the status and distribution of water resources, as input for models of future glacier change, and to assess regional geohazards associated with ice-clad volcanoes.

To improve the strip rolling technology, it is important to know components of the thermal state of both the strip being rolled and the tool used, that is, rolls at each point of different layers of the strip and rolls, in any section of the deformation zone. It was established that for the numerical solution of thermal problems of heat transfer in the strip-roll system described by equations of unsteady heat conduction, the finite difference method is the most effective. For the further numerical solution of the problems of unsteady thermal conductivity of the strip and rolls during hot rolling, the sections of slabs and rolls were divided by a conditional mesh. Energy balance equations with subsequent finite-difference Fourier approximation for possible options of the mesh nodes occurring in solving the two-dimensional problem of unsteady heat conduction.When solving the heat balance problems for both the strip and the rolls, the performed transformations make it possible to switch from solving the nonlinear heat conduction problem to solving the linearized problem. It was also shown that when calculating the thermal state of the active zone in which cyclic temperature changes occur during one revolution, it becomes possible to switch from solving a problem in a cylindrical coordinate system to solving it in a rectangular coordinate system. Transition to solving a one-dimensional strip-roll system greatly simplifies the calculation. The solution of the III boundary-value problem for the roll and comparison of the obtained results with the results of solutions for the strip-roll system enables the theoretical determination of the heat transfer coefficient in the deformation zone.The study results can be used to determine temperature and speed mode of cooling a thin strip during its rolling as well as set tasks for designing special equipment for accelerated cooling in a production stream of strip rolling mills

La iniciativa Yasuní –presentada por Alberto Acosta cuando fue Ministro de Energía y Minas en los primeros tiempos del gobierno de Rafael Correa– recogió las propuestas de varias personas, movimientos y organizaciones de la sociedad civil ecuatoriana y fue asumida por el Presidente de la República, Rafael Correa, en la sesión del Directorio de Petroecuador, el 30 de marzo de 2007. De esta manera, Rafael Correa congeló las pretensiones de Petroecuador de empezar inmediatamente el proceso de licitación para la extracción del crudo del campo Ishpingo- Tambococha-Tiputini (ITT). En esa ocasión el pronunciamiento del Ministerio de Energía fue muy claro: “Se aceptó como primera opción la de dejar el crudo represado en tierra, a fin de no afectar un área de extraordinaria biodiversidad y no poner en riesgo la existencia de varios pueblos en aislamiento voluntario o pueblos no contactados. Esta medida será considerada siempre y cuando la comunidad internacional entregue al menos la mitad de los recursos que se generarían si se opta por la explotación del petróleo, recursos que requiere la economía ecuatoriana para su desarrollo”. De esta declaración se deducen dos asuntos: desde la perspectiva presidencial, siempre había una segunda opción: el extraer el petróleo. Los objetivos de conservación de la biodiversidad de Yasuní y de respeto al territorio de los pueblos en aislamiento voluntario se garantizaban en la medida en que se obtuviese una compensación internacional estimada entonces en 350 millones de dólares. Adicionalmente, el dejar el crudo en el subsuelo suponía concentrar en esa opción los esfuerzos prioritarios y, sobre todo, ser coherente con ella.

Assessing Biodiversity Declines Understanding human impact on biodiversity depends on sound quantitative projection. Pereira et al. (p. 1496 , published online 26 October) review quantitative scenarios that have been developed for four main areas of concern: species extinctions, species abundances and community structure, habitat loss and degradation, and shifts in the distribution of species and biomes. Declines in biodiversity are projected for the whole of the 21st century in all scenarios, but with a wide range of variation. Hoffmann et al. (p. 1503 , published online 26 October) draw on the results of five decades' worth of data collection, managed by the International Union for Conservation of Nature Species Survival Commission. A comprehensive synthesis of the conservation status of the world's vertebrates, based on an analysis of 25,780 species (approximately half of total vertebrate diversity), is presented: Approximately 20% of all vertebrate species are at risk of extinction in the wild, and 11% of threatened birds and 17% of threatened mammals have moved closer to extinction over time. Despite these trends, overall declines would have been significantly worse in the absence of conservation actions.