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Raul Morin, author of 'Among the Valiant' shakes hands with Dr. Hector P. Garcia (photograph)
No full text(L. to R.): Raul Morin, author of 'Among the Valiant' shakes hands with Dr. Hector P. Garcia
Photoactivity of Shape-Controlled TiO2 in Gas-Solid Regime Under Solar Irradiation
No full textShape-controlled TiO2 materials have been tested as photocatalysts under
both simulated and natural solar irradiation
Applications of solar radiation pressure dominated highly non-Keplerian trajectories around minor bodies
No full textWith the growing interest in the exploration and possible exploitation of small minor bodies, demonstrator missions to asteroids and comets are a trending topic in the research community. Various strategies appearing in literature for the characterisation and proximity operations of small asteroids have limited coverage of the sunlit side of an asteroid. This paper proposes the use of highly non-Keplerian trajectories enabled by solar radiation pressure to map and characterize the region around the sub-solar point of small asteroids. Strategies involving a combination of retrograde and prograde orbits together with inversions of the orbit direction by either manoeuvres or exploiting the natural dynamics are presented and analysed in detail. Additional orbits of interest for hopper spacecraft are also discussed
Photocatalytic Solar Light H2 Production by Aqueous Glucose Reforming
No full textPhotocatalytic Solar Light H2 Production by Aqueous Glucose Reformin
Current sheets in the solar corona : formation, fragmentation and heating
No full textIn this thesis we investigate current sheets in the solar corona. The well known 1D model for the tearing mode instability is presented, before progressing to 2D where we introduce a non-uniform resistivity. The effect this has on growth rates is investigated and we find that the inclusion of the non-uniform term in η cause a decrease in the growth rate of the dominant mode. Analytical approximations and numerical simulations are then used to model current sheet formation by considering two distinct experiments. First, a magnetic field is sheared in two directions, perpendicular to each other. A twisted current layer is formed and we find that as we increase grid resolution, the maximum current increases, the width of the current layer decreases and the total current in the layer is approximately constant. This, together with the residual Lorentz force calculated, suggests that a current sheet is trying to form. The current layer then starts to fragment. By considering the parallel electric field and calculating the perpendicular vorticity, we find evidence of reconnection. The resulting temperatures easily reach the required coronal values. The second set of simulations carried out model an initially straight magnetic field which is stressed by elliptical boundary motions. A highly twisted current layer is formed and analysis of the energetics, current structures, magnetic field and the resulting temperatures is carried out. Results are similar in nature to that of the shearing experiment
Dense suspension of solid particles as a new heat transfer fluid for concentrated solar thermal plants: on-sun proof of concept
No full textThis paper demonstrates the capacity of dense suspensions of solid particles to transfer concentrated solar power from a tubular receiver to an energy conversion process by acting as a heat transfer fluid. Contrary to a circulating fluidized bed, the dense suspension of particles’ flows operates at low gas velocity and large solid fraction. A single-tube solar receiver was tested with 64 µm mean diameter silicon carbide particles for solar flux densities in the range 200–250 kW/m2, resulting in a solid particle temperature increase ranging between 50 °C and 150 °C. The mean wall-to-suspension heat transfer coefficient was calculated from experimental data. It is very sensitive to the particle volume fraction of the suspension, which was varied from 26 to 35%, and to the mean particle velocity. Heat transfer coefficients ranging from 140 W/m2 K to 500 W/m2 K have been obtained, thus corresponding to a 400 W/m2 K mean value for standard operating conditions (high solid fraction) at low temperature. A higher heat transfer coefficient may be expected at high temperatures because the wall-to-suspension heat transfer coefficient increases drastically with temperature. The suspension has a heat capacity similar to a liquid heat transfer fluid, with no temperature limitation but the working temperature limit of the receiver tube. Suspension temperatures of up to 750 °C are expected for metallic tubes, thus opening new opportunities for high efficiency thermodynamic cycles such as supercritical steam and supercritical carbon dioxide
Valoración de colectores solares térmicos planos de vacío para la producción de frío
No full textLos objetivos a cumplir son: - Revisión bibliográfica sobre el estado actual de la tecnología de energía solar térmica de baja temperatura y sus aplicaciones para la producción de frío.- Análisis de los datos experimentales de los colectores planos de vacío y de la máquina de absorción YAZAKI WFC-10. - Adaptación de un modelo de una instalación de frío solar (planta solar y máquina de absorción) empleando el calor procedente de los colectores solares planos y analizando la influencia de la superficie solar y volumen del tanque de almacenamiento. - Realización de un estudio económico y medioambiental de la instalación.Ingeniería Técnica en Mecánic
Proposal of a Reflector-Enhanced Solar Still Concept and Its Comparison with Conventional Solar Stills
No full textWater scarcity is a global concern and poses significant problems to countries with arid and semi-arid climates, like Iran. Considering financial difficulties, a lack of knowledge about high-tech alternatives, low incomes, a lack of access to high-tech tools, and low maintenance capabilities in developing countries, solar still desalination is a decent technology for providing proper water, especially for rural areas. However, the low water-production rate using this method dictates a very vast area requirement for solar still farms in order to provide significant amounts of water. In this research, we proposed a mirror-enhanced solar still and mathematically compared its water-production rate to that of conventional ones. In comparison to conventional solar stills, our proposed reflector-enhanced solar still benefits from several improvements, including lower glass temperatures, increased water basing temperatures, and receiving much more solar irradiation. Hence, the proposed system can increase water production from 7.5 L/day to 24 L/day. The results showed that the proposed method is highly effective and could be used in field-scale projects in arid and semi-arid climates
Electrochemical Assessment of the Band-Edge Positioning in Shape-Tailored TiO2-Nanorod-Based Photoelectrodes for Dye Solar Cells
No full textThree families of linear shaped TiO2 anatase nanocrystals with variable aspect ratio (4, 8, 16)
and two sets of branched TiO2 anatase nanocrystals (in the form of open-framework sheaf-like
nanorods and compact braid-like nanorod bundles, respectively) were employed to fabricate
high-quality mesoporous photoelectrodes and then implemented into dye-sensitized solar cells to
elucidate the intrinsic correlation holding between the photovoltaic performances and the
structure of the nanocrystal building blocks. To this aim, the chemical capacitance and the charge-transfer resistance of the photoelectrodes were extrapolated from electrochemical
impedance spectroscopy measurements and used to draw a quantitative energy diagram of the
dye-sensitized solar cells realized, on the basis of which their photovoltaic performances have
been discussed. It has thus been revealed that photoanodes made from braid-like branchednanorod
bundles exhibited the most favorable conditions to minimize recombination at the
interface with the electrolyte due to their deep distribution of trap states, whereas linear-shaped
nanorods with higher aspect-ratios result in more remarkable downshift of the conduction band
edge
Two dimensional hybrid simulations of small scale obstacles in the solar wind
No full textThe structure and dynamics of the solar wind interaction with two small
scale obstacles (of the order of a pickup ion gyroradius) is examined. These are a
comet, comparable to Grigg-Skjellerup, and a weakly ionospheric planet. We also
perform a pilot study of an intrinsically magnetized planet in such flow, in preparation
for a future three-dimensional simulation. Here, we use two-dimensional hybrid
simulations (particle ions, fluid electrons) and consider different solar wind Alfven
Mach number flow (MA) and interplanetary magnetic field orientation relative to
this plane. This allows control of the available wave types.
The cometary simulations display magnetosonic "turbulence" as MA is increased,
when the field is perpendicular to the simulation plane. If we allow parallel
propagating modes by setting the field parallel to the plane, we find the "turbulence"
significantly changes in scale and extent, suggesting resonant growth of Alfven ion
cyclotron waves in the presence of magnetosonic "turbulence" occurs. Free energy
is available from picked up cometary ions. The process depends on the cometary ion
density, which strongly varies, and we conclude this explains the broadband nature
of the disturbances.
In the perpendicular field orientation, the planetary source produces a novel
two tail structure which continuously strips the planetary ionosphere. We find these
tails have very distinct characteristics, resulting in the wake being filled relatively
quickly downstream, by complex structure. At higher MAl magnetosonic "turbulence"
again appears. Switching the field parallel to the plane causes massive field
line draping and pile-up, and causes instability. A long lasting wake appears, and
we conclude that a three-dimensional simulation is required.
The magnetized ionospheric planet pilot study proved difficult to scale accurately
in two dimensions. The planetary field failed to penetrate the solar wind,
however it appears the simulation would be stable and achieve equilibrium in three
dimensions
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