Using vanadium redox flow batteries for the electricity storage towards the electric vehicles fast charging process

This work was later revised, extended and published as a full journal paper in ENERGY. Please use the journal version for citation purposes: Álvaro Cunha, Jorge Martins, Nuno Rodrigues, Vítor Monteiro, João L. Afonso, Paula Ferreira, F. P. Brito, Assessment of the use of Vanadium Redox Flow Batteries for Energy Storage and Fast Charging of Electric Vehicles in Gas Stations, Energy, 115-2, (2016), 1478–1494, DOI:10.1016/j.energy.2016.02.118. journal article available at: http://www.sciencedirect.com/science/article/pii/S0360544216301803The multitude and magnitude of the problems deriving from the use of fossil fuels for road transport is widely known. Therefore, electric mobility associated with renewable energy sources seems to be a good solution for minimizing these problems. However, the time required to charge the batteries of Electric Vehicles (EVs) and the availability of charging stations are seen as critical factors for their market viability. The use of fast charging stations is a possibility to mitigate the long time required to charge the batteries, but the high cost for power availability makes their operation very expensive. Moreover, it might be difficult to find suitable and affordable locations for installing these stations, so gas stations seem to be good candidates for this purpose. This paper assesses the use of fast charging stations for EVs in conjunction with Vanadium Redox Flow Batteries (VRFBs). Taking into account the low energy density of VRFBs, they are especially suited for situations where volume and weight are not limiting factors. Moreover, their liquid nature allows their installation inside deactivated underground fuel tanks located at gas stations. A preliminary assessment of a VRFB system for EVs fast charging stations taking advantage of existing gas stations infrastructures is presented. An energy and cost analysis of this concept is outlined, including a sensitivity analysis which shows that the project is technologically and economically viable for the conditions tested, although with long payback times.MOBI-MPP (MIT-Pt/EDAM-SMS/0030/2008) supported by the MIT Portugal Program and FEDER funds through the Programa Operacional Factores de Competitividade e COMPETE and National Funds through FCT e Foundation for Science and Technology. Post-doctoral grants SFRH/BPD/ 51048/2010 and SFRH/BPD/89553/2012 supported by the MIT Portugal EDAM and FCT, respectivelyinfo:eu-repo/semantics/publishedVersio

Evaluating Two Quantitative Ethnobotanical Techniques

A critical evaluation of two quantitative techniques used in ethnobotanical studies was undertaken using data concerning plant use in a rural community in the semi-arid region of Pernambuco State, northeastern Brazil. The relative importance of 36 native woody species reported as being useful by 98 informants was calculated employing the Use-Value (UV) and Relative Importance (RI) techniques. Both techniques place value on a given taxon based on the number of uses attributed to it. Results obtained for both techniques are positively correlated, suggesting that they can be used interchangeably to evaluate local knowledge of a given resource. The implications and interpretation limitations of these two techniques are discussed in detail

Energy Resolution studies for NEXT

This work aims to present the current state of simulations of electroluminescence (EL) produced in gas-based detectors with special interest for NEXT --- Neutrino Experiment with a Xenon TPC. NEXT is a neutrinoless double beta decay experiment, thus needs outstanding energy resolution which can be achieved by using electroluminescence. The process of light production is reviewed and properties such as EL yield and associated fluctuations, excitation and electroluminescence efficiencies, and energy resolution, are calculated. An EL production region with a 5 mm width gap between two infinite parallel planes is considered, where a uniform electric field is produced. The pressure and temperature considered are 10 bar and 293 K, respectively. The results show that, even for low values of VUV photon detection efficiency, good energy resolution can be achieved: below 0.4 % (FWHM) at $Q_{\beta\beta}=$2.458 MeV

Evaluation of turbulent dissipation rate retrievals from Doppler Cloud Radar

Turbulent dissipation rate retrievals from cloud radar Doppler velocity measurements are evaluated using independent, in situ observations in Arctic stratocumulus clouds. In situ validation data sets of dissipation rate are derived using sonic anemometer measurements from a tethered balloon and high frequency pressure variation observations from a research aircraft, both flown in proximity to stationary, ground-based radars. Modest biases are found among the data sets in particularly low- or high-turbulence regimes, but in general the radar-retrieved values correspond well with the in situ measurements. Root mean square differences are typically a factor of 4-6 relative to any given magnitude of dissipation rate. These differences are no larger than those found when comparing dissipation rates computed from tetheredballoon and meteorological tower-mounted sonic anemometer measurements made at spatial distances of a few hundred meters. Temporal lag analyses suggest that approximately half of the observed differences are due to spatial sampling considerations, such that the anticipated radar-based retrieval uncertainty is on the order of a factor of 2-3. Moreover, radar retrievals are clearly able to capture the vertical dissipation rate structure observed by the in situ sensors, while offering substantially more information on the time variability of turbulence profiles. Together these evaluations indicate that radar-based retrievals can, at a minimum, be used to determine the vertical structure of turbulence in Arctic stratocumulus clouds

Low-diffusion Xe-He gas mixtures for rare-event detection: electroluminescence yield

High pressure xenon Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification are being proposed for rare event detection such as directional dark matter, double electron capture and double beta decay detection. The discrimination of the rare event through the topological signature of primary ionisation trails is a major asset for this type of TPC when compared to single liquid or double-phase TPCs, limited mainly by the high electron diffusion in pure xenon. Helium admixtures with xenon can be an attractive solution to reduce the electron diffu- sion significantly, improving the discrimination efficiency of these optical TPCs. We have measured the electroluminescence (EL) yield of Xe–He mixtures, in the range of 0 to 30% He and demonstrated the small impact on the EL yield of the addition of helium to pure xenon. For a typical reduced electric field of 2.5 kV/cm/bar in the EL region, the EL yield is lowered by ∼ 2%, 3%, 6% and 10% for 10%, 15%, 20% and 30% of helium concentration, respectively. This decrease is less than what has been obtained from the most recent simulation framework in the literature. The impact of the addition of helium on EL statistical fluctuations is negligible, within the experimental uncertainties. The present results are an important benchmark for the simulation tools to be applied to future optical TPCs based on Xe-He mixtures. [Figure not available: see fulltext.]