Global distribution of winter lightning: a threat to wind turbines and aircraft

Lightning is one of the major threats to multi-megawatt wind turbines and a concern for modern aircraft due to the use of lightweight composite materials. Both wind turbines and aircraft can initiate lightning, and very favorable conditions for lightning initiation occur in winter thunderstorms. Moreover, winter thunderstorms are characterized by a relatively high production of very energetic lightning. This paper reviews the different types of lightning interactions and summarizes the well-known winter thunderstorm areas. Until now comprehensive maps of global distribution of winter lightning prevalence to be used for risk assessment have been unavailable. In this paper we present the global winter lightning activity for a period of 5 years. Using lightning location data and meteorological re-analysis data, six maps are created: annual winter lightning stroke density, seasonal variation of the winter lightning and the annual number of winter thunderstorm days. In the Northern Hemisphere, the maps confirmed Japan to be one of the most active regions but other areas such as the Mediterranean and the USA are active as well. In the Southern Hemisphere, Uruguay and surrounding area, the southwestern Indian Ocean and the Tasman Sea experience the highest activity. The maps provided here can be used in the development of a risk assessment.Peer ReviewedPostprint (published version

Asteroids' physical models from combined dense and sparse photometry and scaling of the YORP effect by the observed obliquity distribution

The larger number of models of asteroid shapes and their rotational states derived by the lightcurve inversion give us better insight into both the nature of individual objects and the whole asteroid population. With a larger statistical sample we can study the physical properties of asteroid populations, such as main-belt asteroids or individual asteroid families, in more detail. Shape models can also be used in combination with other types of observational data (IR, adaptive optics images, stellar occultations), e.g., to determine sizes and thermal properties. We use all available photometric data of asteroids to derive their physical models by the lightcurve inversion method and compare the observed pole latitude distributions of all asteroids with known convex shape models with the simulated pole latitude distributions. We used classical dense photometric lightcurves from several sources and sparse-in-time photometry from the U.S. Naval Observatory in Flagstaff, Catalina Sky Survey, and La Palma surveys (IAU codes 689, 703, 950) in the lightcurve inversion method to determine asteroid convex models and their rotational states. We also extended a simple dynamical model for the spin evolution of asteroids used in our previous paper. We present 119 new asteroid models derived from combined dense and sparse-in-time photometry. We discuss the reliability of asteroid shape models derived only from Catalina Sky Survey data (IAU code 703) and present 20 such models. By using different values for a scaling parameter cYORP (corresponds to the magnitude of the YORP momentum) in the dynamical model for the spin evolution and by comparing synthetics and observed pole-latitude distributions, we were able to constrain the typical values of the cYORP parameter as between 0.05 and 0.6.Comment: Accepted for publication in A&A, January 15, 201

New System for the Acceleration of the Airflow in Wind Turbines

Background: This patent is based on the wind industry technology called Diffuser Augmented Wind Turbines (DAWTs). This technology consists of a horizontal axis wind turbine, which is housed inside a duct with diverging section in the direction of the free air stream. In this paper, a review of preceding patents related to this technology is carried out. Objective: This paper presents an innovative patent to improve the performance of horizontal axis wind turbines. In particular, this system is aimed at improving the performance of those turbines that otherwise might not be installed due to the low wind resource existing at certain locations. Methods: The most innovative elements of this patent are: (1) the semi-spherical grooves, which are mechanized on the surface of the two diffusers in order to guarantee a more energetic boundary layer; (2) the coaxial diffuser, which is located downwind following the first diffuser in order to increase the suction effect on the air mass close to the inlet; (3) the coaxial rings located around the first diffuser outlet, which are used to deflect the external airflow toward the turbine wake; and (4), the selforientating system to orientate the system by the prevailing wind direction. Results: An application of the patent for increasing the power generated by a horizontal axis wind turbine with three blades is presented. The patent is designed and its performance is evaluated by using a Computational Fluid Dynamics code. The numerical results show that this system rises the airflow going through the rotor of the turbine. Conclusion: The patented device is an original contribution aimed at enabling a more profitable installation of wind turbines in places where the wind resource is insufficient because of the wind shear caused both by the proximity of the earth and the obstacles on the earth surface.This work was supported by the OASIS Research Project that was cofinanced by CDTI (Spanish Science and Innovation Ministry) and developed with the Spanish companies: Iridium, OHL Concesiones, Abertis, Sice, Indra, Dragados, OHL, Geocisa, GMV, Asfaltos Augusta, Hidrofersa, Eipsa, PyG, CPS, AEC and Torre de Comares Arquitectos S.L and 16 research centres. The authors also acknowledge the partial funding with FEDER funds under the Research Project FC-15-GRUPIN14-004. Finally, we also thank Swanson Analysis Inc. for the use of ANSYS University Research programs as well as the Workbench simulation environment

HARSNET, Thematic Network on Hazard Assessment of Highly Reactive Systems

The Health and Safety Executive indicates that in United Kingdom, about five accidents per month involve exothermic runaway reactions, of which approximately half occur in batch or semibatch reactors. The major source of hazard comes from the highly reactive chemicals necessarily involved in many discontinuous processes and the strongly exothermic nature of many industrially important syntheses. In the event of loss of control, thermal runaway can result. Inappropriate engineering design for heat transfer, inadequate understanding of the process chemistry and thermodynamic, unsuitable control systems and inappropriate operational procedures, including training, have been highlighted as the prime causes of these types of incidents. Due to the importance of the field under consideration, most of the large companies and some universities and research centres have developed their own specific procedures for the safety assessment of highly reactive systems based on sophisticated instruments that can reproduce industrial processes at bench scale. However many fine and speciality chemicals are produced in Small and Medium Enterprises, SME, which usually do not have the necessary expertise to apply such methodologies. In addition, SME's frequently have limited resources so that there are severe constraints regarding the purchase or use of the type of expensive equipment sometimes needed for the testing methodologies. However, prevention of runaways and their consequences is of the highest priority for the chemical industry. Because of this, an important number of chemical companies, both, small and large, universities, and research centres have created HarsNet, supported by the European Commission. The acronym HarsNet means thematic network on hazard assessment of highly reactive systems. HarsNet is a thematic network included in the Industrial and Materials Technologies Programme (Brite EuRam, Project number: BET2-0572) of the European Commission. This type of thematic network is a platform to exchange and create knowledge, that joins specialists in a specific field, from European Universities and industry. The importance of HarsNet is guaranteed by the number of partners, 26 from 11 countries in the European Union as well as by the chemical industry participation, about the 58 % and by the economic support from the European Union

Comparative study of binderless zeolites and carbon molecular sieves as adsorbents for CO2 capture processes

CO2 capture from concentrated sources such as power plants will play an important role in reducing CO2 emissions, contributing to climate change mitigation. Adsorption technology has attracting scientific attention because it offers improved energy efficiency and reduced costs. Two of the most used families of adsorbents in the industry are zeolites and carbon-based adsorbents. This study compares the CO2 separation performance of two promising groups of adsorbents belonging to these families: binderless zeolites and carbon molecular sieves (CMSs). Five adsorption key performance indicators (KPIs), namely adsorption capacity, working capacity, regenerability, selectivity and adsorption selection parameter were obtained from the adsorption isotherms (CO2 and N2; measured at 0-10 bar and 283-323 K) and used to assess the potential of the adsorbents for CO2 capture processes. In general, the KPIs were better for binderless zeolites than for CMSs although CMSs had better regenerability. Zeolites 13XBL and 5ABL were selected as the most promising adsorbents and were tested in a laboratory column set-up for dynamic adsorption of a CO2/N2 mixture (15%/85% v/v), resembling a dry flue gas composition. Simulations of column adsorption experiments were then carried out combining an extended dual-site Langmuir (DSL) model for binary mixtures with Aspen Adsorption™. Binderless zeolite 13XBL showed a higher selectivity with a lower dependence on the pressure and temperature of adsorption, when compared to zeolite 5ABL. These results show that the 13XBL can be considered a good adsorbent for CO2/N2 separations.The authors gratefully acknowledge the funding provided by the company GasN2 and the knowledge and enterprise department of the Catalan government through its Industrial Doctorate program to support this research project (AGAUR, Doctorats Industrials 2014 DI-057). Special thanks to graduates students Carlos Arregui and Guillermo Parladé for their help and support provided with the modeling and master student Albert Melis for the support with column experiments. GESPA group has been recognized as Consolidated Research Group by the Catalan Government with code 2017-SGR-1016. The authors gratefully acknowledge the financial support received from the Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033, Project PID2020-115334GB-I00) and Principado de Asturias (FICYT)-European Union (FEDER) (Project PCTI-Asturias IDI/2021/000015). Miguel Montes is member of the SusPlast PTI+ platform of the Spanish National Research Council (CSIC).Peer reviewe