12Energy storage technologies provide an alternative solution to the problem of balancing power generation and power consumption. Redox flow cells are designed to convert and store electrical energy into chemical energy and release it in a controlled fashion when required. Many redox couples and cell designs have being evaluated. In this paper, redox flow systems are compared in the light of characteristics such as open circuit potential, power density, energy efficiency and charge-discharge behaviour. The key advantages and disadvantages of redox flow cells are considered while areas for further research are highlighted.

No abstract

The aim of this paper is the characterization of a carbon felt (Le Carbone Lorraine, RVC 4002) to be used as three-dimensional electrode. A wide group of very different techniques were used in the physical and structural characterization of this material. Both, structural (porosity, mean pore radius, specific surface area, tortuosity) and physical properties (permeability, electrical resistance) were determined by using mercury porosimetry, adsorption isotherm analysis, a filamentary analog procedure and liquid permeametry (pressure drop method). The results obtained from the modelling of the hydrodynamic behaviour, from previous work, were also applied here. The carbon felt studied was found to have a porosity around 0.98, a specific surface area of 22100-22700 m -1 , 2.7 10 -3 Ω m electrical resistivity and a tortuosity between 5 and 6. The comparison of these results with those found in the literature for other similar materials, used as three-dimensional electrodes, highlights the attractions of this

No abstract

The intensity distribution of the ultrasonic energy is, after the frequency, the most significant parameter to characterize ultrasonic fields in any sonochemical experiment.Whereas in the case of low intensity ultrasound the measurement of intensity and its distribution is well solved, in the case of high intensity (when cavitation takes place) the measurement is much more complicated. That is why the predicting the acoustic pressure distribution within the cell is desirable.A numerical solution of the wave equation gave the distribution of intensity within the cell. The calculations together with experimental verification have shown that the whole reactor behaves like a resonator and the energy distribution depends strongly on its shape.The agreement between computational simulations and experiments allowed optimisation of the shape of the sonochemical reactor. The optimal geometry resulted in a 2 strong increase in intensity along a large part of the cell. The advantages of such optimised geometry are (i) the ultrasonic power necessary for obtaining cavitation is low, (ii) low power delivered to the system results in only weak heating; consequently no cooling is necessary and (iii) the "active volume" is large, i.e. the fraction of the reactor volume with high intensity is large and is not limited to a vicinity close to the horn tip.