Catalytic properties of Ceramic Foams

Several ceramic foams made of Ceria- stabilized Tetragonal Zirconia Polycrystals have been prepared by an in-situ polimerization of polyurethans. It is shown that the powder preparation technique has a profound influence on the microstructure of the foam; specifically, co-precipitaed powders give origin to more irregular surfaces of the foam, whereas co-milled powders result in very dense and regular microstructures of the struts constituting the foams. The catalitic activity of these foams have been studied by Temperature Programmed Reduction (TPR) experiments and it is shown that co-milled powders yields TPR profiles rather similar to pure Cerium oxide, even if the real CeO2 content of the foams is about 12-14% mol

Power electronic conditioning systems for industrial photovoltaic fields: centralized or string inverters?

Photovoltaic (PV) plants in Italy are presently subject to a rapid increase due to recent government incentives dedicated to grid connected PV plants. Incentives are given on the basis of the energy actually delivered to the grid, so that it becomes fundamental for the owner to produce as much energy as possible in order to reduce the payback time. In this framework, PV system efficiency plays a fundamental role. This paper focuses on medium and large size PV power systems, for which plant efficiency becomes a key design issue. In particular, the choice between centralized or distributed ("string") architecture is analyzed in terms of plant efficiency, considering the following basic issues: (1) losses in the power electronic conditioning system; (2) losses due to cable dissipation; (3) losses due to possible maximum power point mismatch