Exergy cost of mineral resources

Mineral deposits are considered as natural capital whose value can be assessed in exergy terms. Historical industry experience provides evidence that exploitation of mineral deposits and the beneficiation of ores are essentially energy intensive. The persisting decline of the grade of the developed deposits demands increasing exergy replacement and processing costs. The results demonstrate how far processed ores and concentrates are from ideal behaviour, and technologies from reversibility conditions. The exploitation of mineral resources of declining quality for mineral commodities imply a long time trend of increasing mass and exergy inputs spent per unit product output, in line with a law of ‘diminishing returns’ on invested exergy

Low-temperature dielectric measurements of confined water in porous granites

The dielectric behavior of rocks affected by the known phase transition of supercooled water is the main problem we analyzed. Three different granitic rocks were used to perform dielectric measurements in the frequency range from 100 Hz to 1 MHz and temperatures 100–350 K. Thin cylindrical samples were prepared, and circular electrodes were established using silver conductive paint. A clear change in the dielectric measurements appears at T∼220K for one of the samples. This coincides with the known phase transition of supercooled water. Tightly bounded water confined in the pores of the rock do not crystallize at 273 K, but form a metastable liquid down to 200–220 K maintaining water polarization. Below this temperature, water molecules solidify and polarizability decreases. The rock presenting the most sizable change has a very low specific surface area of ∼0.09m2g−1, has connected porosity of ∼1.10%, and has the smallest degree of alteration. In addition, geochemical analyzes reveal a low percentage of hydration water in its structure confirming the role of pore water in this change. A comparison between water-saturated, oven-dried, and vacuum-dried samples was done. Finally, a logarithmic dependency of the critical temperature for the supercooled water phase transition with the measuring frequency was found

The Role of Synthetic Fuels for a Carbon Neutral Economy

Fossil fuels depletion and increasing environmental impacts arising from their use call for seeking growing supplies from renewable and nuclear primary energy sources. However, it is necessary to simultaneously attend to both the electrical power needs and the specificities of the transport and industrial sector requirements. A major question posed by the shift away from traditional fossil fuels towards renewable energy sources lies in matching the power demand with the daily and seasonal oscillation and the intermittency of these natural energy fluxes. Huge energy storage requirements become necessary or otherwise the decline of the power factor of both the renewable and conventional generation would mean loss of resources. On the other hand, liquid and gaseous fuels, for which there is vast storage and distribution capacity available, appear essential to supply the transport sector for a very long time ahead, besides their domestic and industrial roles. Within this context, the present assessment suggests that proven technologies and sound tested principles are available to develop an integrated energy system, relying on synthetic fuels. These would incorporate carbon capture and utilization in a closed carbon cycle, progressively relying mostly on solar and/or nuclear primary sources, providing both electric power and gaseous/liquid hydrocarbon fuels, having ample storage capacity, and able to timely satisfy all forms of energy demand. The principles and means are already available to develop a carbon-neutral synthetic fuel economy

Warm cloud study from ground-based remote sensing using different radiative transfer approaches

In this work, an analysis of radiation fields in cloudy atmospheres, as well as of cloud shape factor is presented based on results obtained from different radiative transfer models. The radiative transfer approaches include a plane-parallel approximation (1D), a three-dimensional radiative transfer model (3D) and an analytical model that has been developed and adjusted by the authors. The irradiances are obtained from simulations with the numerical radiative transfer models, considering only cumulus clouds. Furthermore, a shape factor related to cloud roughness is derived from the combination of the analytical model with the 3D numerical model, considering the same atmospheric conditions for all simulations

A simple statistical procedure for the analysis of radon anomalies associated with seismic activity

This study presents an analysis of data from various radon anomalies that were compiled by Toutain and Baubron [1999], to investigate their relationships with the earthquake parameters of magnitude and distance from epicenter. The simple methodology applied here reveals significant and positive correlation between the duration of the radon anomalies and the ratio between the earthquake preparation radius and the distance between the sensor and the event epicenter. This shows an important relationship between seismic activity and duration of radon anomalies at a local scale. The consequences and implications of this relationship are discussed

Influence of seismic activity on the atmospheric electric field in Lisbon (Portugal) from 1955 to 1991

In the present study, we considered the influence of seismic activity on the atmospheric electric field recorded at Portela meteorological station (Lisbon, Portugal) for the period from 1955 to 1991. To this end, an exploratory method was developed, which involved the selection of events for which the distance from the atmospheric electrical field sensor to the earthquake epicenter is smaller than the preparation radius of the event. This enabled the correlation of the atmospheric electric field variations with a quantity S, defined basically as the ratio of the earthquake preparation radius to the distance between the sensor and the event epicenter. The first results show promising perspectives, but clearly a more profound study is required, in which a careful analysis of the weather conditions and other variables, like atmospheric radon levels, must be considered

Low-temperature dielectric measurements of confined water in porous granites

ABSTRACT The dielectric behavior of rocks affected by the known phase transition of supercooled water is the main problem we analyzed. Three different granitic rocks were used to perform dielectric measurements in the frequency range from 100 Hz to 1 MHz and temperatures 100-350 K. Thin cylindrical samples were prepared, and circular electrodes were established using silver conductive paint. A clear change in the dielectric measurements appears at T ∼ 220 K for one of the samples. This coincides with the known phase transition of supercooled water. Tightly bounded water confined in the pores of the rock do not crystallize at 273 K, but form a metastable liquid down to 200-220 K maintaining water polarization. Below this temperature, water molecules solidify and polarizability decreases. The rock presenting the most sizable change has a very low specific surface area of ∼0.09 m 2 g −1 , has connected porosity of ∼1.10%, and has the smallest degree of alteration. In addition, geochemical analyzes reveal a low percentage of hydration water in its structure confirming the role of pore water in this change. A comparison between water-saturated, oven-dried, and vacuum-dried samples was done. Finally, a logarithmic dependency of the critical temperature for the supercooled water phase transition with the measuring frequency was found