• Energy Research

Abstract Urban environments present new challenges to the integration of photovoltaic systems onto the building envelope. This study describes a multi-objective genetic algorithm developed for the maximization of the PV electrical production and minimization of relevant system costs, such as wiring, modules and inverter costs. Two case studies are analyzed, featuring a partially shaded rooftop and a vertical facade. The PV layouts suggested by the genetic algorithm outperform the conventional configurations by reducing the cost of produced electricity between 6% and 18%. The optimization results also show that layouts with more but shorter PV strings achieve higher energy yields. However, when compared with longer clustered strings in the most sunlit areas of the surfaces, this results in the doubling of costs.

The Silicon on Dust Substrate (SDS) is a gas-to-wafer process that produces multicrystalline silicon ribbons directly from gaseous feedstock (silane), avoiding the standard industry steps of polysilicon deposition, crystal growth, and wafering. The SDS technique consists of three main steps: (i) micrometric-sized silicon powder production by grinding silicon chunks; (ii) chemical vapor deposition (CVD) of silicon over this silicon powder substrate; and (iii) zone-melting recrystallization (ZMR) of the nanocrystalline pre-ribbon obtained in the CVD step. Several samples were produced by this technique. During CVD, mechanically self-sustained nanocrystalline pre-ribbons were grown over silicon powder substrates, with growth rates in the order of 50 µm/min. The ZMR process performance is substantially impacted by the pre-ribbon physical characteristics. The best and largest recrystallizations were achieved on pre-ribbons grown over powder substrates with smaller particle sizes, which also have lower substrate powder incorporation ratios. Multicrystalline silicon ribbons with crystalline areas as large as 2 × 4 cm2 were successfully produced. These areas have visible columnar crystal growth with crystal lengths up to 1 cm. The SDS ribbons’ measured resistivity confirmed the high powder content of the resulting material. The ability to produce solar cells on SDS multicrystalline silicon ribbons was demonstrated.

Abstract The study of sustainable energy systems is an interdisciplinary endeavour which entails the analysis of a large amount of diverse data and complex interactions that are better understood if developed from first principles. This paper reviews the approaches to this analysis and presents as a general case study, a fossil free imaginary island whose electricity, heat and mobility demand are fulfilled with sustainable and renewable energies only. The detailed hourly balance between supply and demand highlights the importance of energy storage, which is achieved by reversible hydropower and storage in electric vehicles.

AbstractThis manuscript describes and presents results obtained with an inline optical CVD system operating at low temperature (10mm/min) compressed silicon powder substrate. The deposition parameters, together with the silicon powder substrate feature, provide a solution for a contamination free layer to be detached and used as a pre-ribbon for solar cell formation. 15cm long nanocrystalline silicon pre-ribbon samples were grown at a speed of 10mm/min with depositionrates up to 90μm/min.

Abstract This paper presents the results achieved with an inline optical chemical vapor deposition (CVD) system operating at atmospheric pressure and at low temperatures (