Suchergebnisse

Several oxidation protective coatings, both glass-based and ceramic/polymer hybrid coatings, for p- and n-type thermoelectrics were designed at the Politecnico di Torino in recent years, and they were characterised and tested under relevant conditions. The 'glass-ceramic route' to obtain a thermo-mechanical compatible and high-temperature resistant coated thermoelectric is discussed with some examples. Oxidation tests demonstrated the effectiveness of the coatings for the protection of both n- and p-type thermoelectrics.

Ratiometric luminescence thermometry with trivalent lanthanide ions and their 4fn energy levels is an emerging technique for non-invasive remote temperature sensing with high spatial and temporal resolution. Conventional ratiometric luminescence thermometry often relies on thermal coupling between two closely lying energy levels governed by Boltzmann's law. Despite its simplicity, Boltzmann thermometry with two excited levels allows precise temperature sensing, but only within a limited temperature range. While low temperatures slow down the nonradiative transitions required to generate a measurable population in the higher excitation level, temperatures that are too high favour equalized populations of the two excited levels, at the expense of low relative thermal sensitivity. In this work, we extend the concept of Boltzmann thermometry to more than two excited levels and provide quantitative guidelines that link the choice of energy gaps between multiple excited states to the performance in different temperature windows. By this approach, it is possible to retain the high relative sensitivity and precision of the temperature measurement over a wide temperature range within the same system. We demonstrate this concept using YAl3(BO3)4 (YAB):Pr3+, Gd3+ with an excited 6PJ crystal field and spin-orbit split levels of Gd3+ in the UV range to avoid a thermal black body background even at the highest temperatures. This phosphor is easily excitable with inexpensive and powerful blue LEDs at 450 nm. Zero-background luminescence thermometry is realized by using blue-to-UV energy transfer upconversion with the Pr3+−Gd3+ couple upon excitation in the visible range. This method allows us to cover a temperature window between 30 and 800 K. ; This project has received funding from the European Union's Horizon 2020 FET Open programme under grant agreement No 801305 (NanoTBTech).

The improvement of thermal energy storage systems implemented in solar technologies increases not only their performance but also their dispatchability and competitiveness in the energy market. Latent heat thermal energy storage systems are one of those storing methods. Therefore, the need of finding the best materials for each application becomes an appealing research subject. The main goal of this paper is to find suitable and economically viable materials able to work as phase change material (PCM) within the temperature range of 210-270 ºC and endure daily loading and unloading processes in a system with Fresnel collector and an organic Rankine cycle (ORC). Twenty-six materials have been tested and characterized in terms of their thermophysical conditions, thermal and cycling stability, and health hazard. Two materials out of the 26 candidates achieved the last stage of the selection process. However, one of the two finalists would require an inert working atmosphere, which would highly increase the cost for the real scale application. This leads to a unique suitable material, solar salt (40 wt % KNO3/60 wt % NaNO3). ; This work was partially funded by the European Union's Horizon 2020 Research & Innovation Programme under Grant Agreement 723596 with reference name Innova MicroSolar. This work was partially funded by the Ministerio de Economía y Competitividad de España (ENE2015-64117-C5-1-R (MINECO/FEDER) and ENE2015-64117-C5-3-R (MINECO/FEDER)). The authors would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. José Miguel Maldonado would like to thank the Spanish Government for his research fellowship (BES-2016-076554). Aran Solé would like to thank Ministerio de Economía y Competitividad de España for Grant Juan de la Cierva, FJCI-2015-25741. Alvaro de Gracia has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 712949. Angel G. Fernández would like to acknowledge the financial support provided by GIZ "Programa de pasantía en el extranjero en tecnologías de concentración solar para investigadores" and CONICYT/FONDAP 15110019 "Solar Energy Research Center" SERC-Chile.

We analyze the impact of stratospheric volcanic aerosols on the diurnal temperature range (DTR) over Europe using long-term subdaily station records. We compare the results with a 28-member ensemble of European Centre/Hamburg version 5.4 (ECHAM5.4) general circulation model simulations. Eight stratospheric volcanic eruptions during the instrumental period are investigated. Seasonal all- and clear-sky DTR anomalies are compared with contemporary (approximately 20year) reference periods. Clear sky is used to eliminate cloud effects and better estimate the signal from the direct radiative forcing of the volcanic aerosols. We do not find a consistent effect of stratospheric aerosols on all-sky DTR. For clear skies, we find average DTR anomalies of -0.08 degrees C (-0.13 degrees C) in the observations (in the model), with the largest effect in the second winter after the eruption. Although the clear-sky DTR anomalies from different stations, volcanic eruptions, and seasons show heterogeneous signals in terms of order of magnitude and sign, the significantly negative DTR anomalies (e.g., after the Tambora eruption) are qualitatively consistent with other studies. Referencing with clear-sky DTR anomalies to the radiative forcing from stratospheric volcanic eruptions, we find the resulting sensitivity to be of the same order of magnitude as previously published estimates for tropospheric aerosols during the so-called global dimming period (i.e., 1950s to 1980s). Analyzing cloud cover changes after volcanic eruptions reveals an increase in clear-sky days in both data sets. Quantifying the impact of stratospheric volcanic eruptions on clear-sky DTR over Europe provides valuable information for the study of the radiative effect of stratospheric aerosols and for geo-engineering purposes ; This work is supported by the National Centre for Competence in Research (NCCR)-Climate program of the Swiss National Foundation (PALVAREX project) and under grant CRSI122-130642 (FUPSOL). MeteoSwiss is acknowledged for provision of data. We acknowledge the Catalan Meteorological Office (SMC, Barcelona, Spain) for providing funding support for the digitization of the Barcelona meteorological data series from 1780 to 2012. Computing facilities and time (for the paleosimulation with ECHAM5.4) were provided by the Swiss National Supercomputing Centre (CSCS). A. S. L. was supported by a postd-octoral fellowship from the government of Catalonia (2011 BP-B) and the project NUCLIERSOL (CGL2010-18546)

We analyze the impact of stratospheric volcanic aerosols on the diurnal temperature range (DTR) over Europe using long-term subdaily station records. We compare the results with a 28-member ensemble of European Centre/Hamburg version 5.4 (ECHAM5.4) general circulation model simulations. Eight stratospheric volcanic eruptions during the instrumental period are investigated. Seasonal all- and clear-sky DTR anomalies are compared with contemporary (approximately 20year) reference periods. Clear sky is used to eliminate cloud effects and better estimate the signal from the direct radiative forcing of the volcanic aerosols. We do not find a consistent effect of stratospheric aerosols on all-sky DTR. For clear skies, we find average DTR anomalies of -0.08 degrees C (-0.13 degrees C) in the observations (in the model), with the largest effect in the second winter after the eruption. Although the clear-sky DTR anomalies from different stations, volcanic eruptions, and seasons show heterogeneous signals in terms of order of magnitude and sign, the significantly negative DTR anomalies (e.g., after the Tambora eruption) are qualitatively consistent with other studies. Referencing with clear-sky DTR anomalies to the radiative forcing from stratospheric volcanic eruptions, we find the resulting sensitivity to be of the same order of magnitude as previously published estimates for tropospheric aerosols during the so-called global dimming period (i.e., 1950s to 1980s). Analyzing cloud cover changes after volcanic eruptions reveals an increase in clear-sky days in both data sets. Quantifying the impact of stratospheric volcanic eruptions on clear-sky DTR over Europe provides valuable information for the study of the radiative effect of stratospheric aerosols and for geo-engineering purposes ; This work is supported by the National Centre for Competence in Research (NCCR)-Climate program of the Swiss National Foundation (PALVAREX project) and under grant CRSI122-130642 (FUPSOL). MeteoSwiss is acknowledged for provision of data. We acknowledge the Catalan Meteorological Office (SMC, Barcelona, Spain) for providing funding support for the digitization of the Barcelona meteorological data series from 1780 to 2012. Computing facilities and time (for the paleosimulation with ECHAM5.4) were provided by the Swiss National Supercomputing Centre (CSCS). A. S. L. was supported by a postd-octoral fellowship from the government of Catalonia (2011 BP-B) and the project NUCLIERSOL (CGL2010-18546)