Effect of Na doping on the Ca3Co4O9 thermoelectric performance

Abstract

The MYRTE platform consists of a photovoltaic array, a fuel cells, an electrolyzer, tanks (H 2 , O 2 and H 2 O), a thermal management system and electricity converters associated to various sub-systems. The aim of this platform is to study how hydrogen could be a good solution for storage energy associated to intermittent renewable energy sources systems, like photovoltaic plant, for electrical grid application, in an island context. This article describes the platform's way of operating and specifically the photovoltaic output power fluctuations smoothing, with the trapezoid profile shape, using storage methodology and his association with solar forecasting. The used approach is consistent with the specifications of the invitation to tender of the French Energy Regulation Commission, in September, 2011. Note that during the simulations, we have firstly used measured and not predicted meteorological data, and at this end of this paper the first estimation with our solar forecasting methodology. The main result shown in this paper is that the platform is compatible with this operational mode based on the power fluctuations smoothing. However, to minimize the use of hydrogen stored it is necessary that the supply of the trapezoid profile comes from the PV production rather than the fuel cells. A minimum part of 76 % seems necessary

Thermoelectric properties of lower concentration K-doped Ca 3 Co 4 O 9 ceramics

“…According to the above equation, the value of S increases with decreasing x value, that is, it is assumed that the K ion fraction replaces Co 4+ in CoO 2 , which can reduce the concentration of Co 4+ ions. Simultaneously, the transition of Co 4+ state to the low spin state Co 3+ also reduces x, thereby increasing S. However, S does not change with K doping in the present study, and thus K ions do not enter into the CoO 2 conductive layer, [35] which is consistent with previous E a analysis. Furthermore, the test results can also be analyzed based on Mott formula [36]…”

Influence of a mechano-chemical treatment on the synthesis and characteristics of p-type thermoelectric Ca 3 Co 4 O 9 ceramics

“…In all the samples the electrical conductivity is generally slightly increasing with temperature. The highest s of 44 S/cm at 600 C was obtained for the sample prepared from the MC powder, sintered at 920 C, and is among the highest reported for conventionally sintered Ca349 ceramics [12].…”

Physics and technology of thermoelectric materials and devices

“…For instance, synthesis of Ca 1−x Na x Co 4 O 9 was carried out by ball milling stoichiometrically weighed CaCO 3 , Na 2 CO 3 and Co 2 O 3 at 300 rpm for 30 min using agate ball mill in acetone media. Then, the slurry was dried under infrared radiation for evaporating acetone, followed by hand grinding the obtained powder which was then heat treated under air atmosphere for 12 h [516]. Whereas, for the synthesis of La 0.1−x Dy 0.1+x Sr 0.8 TiO 3 , after weighing the raw materials such as La 2 O 3 , SrCO 3 , TiO 2 and Dy 2 O 3 in stoichiometric proportions, they were subjected to ball milling for 12 h in ethanol media with zirconia balls.…”