The storage of hydrogen by adsorbent materials has been addressed by several researchers. These materials can serve as a reservoir of hydrogen at a very lower temperature and the emptying operation for fuel cells is simply heating the adsorbent bed. However, in order to maximize the ability of the adsorbent materials to meet the instantaneous hydrogen demand, adequate knowledge of desorbed hydrogen flow rate (DHR) must be investigated. The objective of this study is to model the control of the DHR induced by heating. The results show that the excess of hydrogen stored in the adsorbent material can be completely released at room temperature and the DHR increases with temperature. A solution is proposed for stabilizing the DHR, which consists in controlling the fuel cell supply section and, consequently, the power to be produced.
This paper presents a numerical study of heat transfer inside the adsorber-collector of a solar adsorption refrigerator using the activated carbon AC35-methanol pair. The objective is to estimate the amount of the heat loss through the adsorber-collector, during the solar heating phase, and to determine the effect of heating time on the thermal efficiency of the system. The numerical results showed that the heating time is the most important factor affecting the amount of energy loss. It has shown that the shorter heating time corresponds to the higher efficiency of the adsorber-collector. In addition, a new optimal coefficient of performance, COP optm , is proposed to determine the number of adsorbers to be added to a machine. This latter is considered for consuming an energy equivalent to that received by the adsorber-collector. These additional adsorbers use a heat transfer fluid, coming from the adsorber-collector, instead of direct heating by solar radiation. An application example is presented using experimental results obtained from the literature. It has shown that the number of the additional adsorbers can reach three adsorbers.
We report herein the design of promising composite material as a cathode in a rechargeable battery by combining the properties of polypyrrole (PPy) and MnO2 particles. The composites were prepared by electropolymerization of the pyrrole monomer followed by electrodeposition of a manganese salt suspension by two methods. The first method involved the formation of MnO2 in situ in the PPy/ITO electrode, while the second method involved first a preliminary adsorption of Mn 2+ ions in the polymer, followed by an electrochemical of the electrode. The morphology of the resulting composite materials (PPy/MnO2) was studied by Energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR). The investigations of the electrochemical properties of the composite electrodes show that the presence of MnO2 play an important role in improving the surface of polymer films, which leads to lower charge transfer resistance and higher electrode activity. For the optimal synthesis method, the electrode generates a maximum current of up to-7.9 mA.cm-2 for the oxygen reduction reaction, which is eight times the current density delivered by the electrode without PPy.
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