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The present work introduces the conceptual design of the optics for a spectral-splitting and light-guiding photovoltaic (PV) four-terminal (4T) module with appealing features for bifacial operation. The geometry here described performs low-gain 2D concentration in the visible (VIS) spectrum and can couple a Si solar cell to a wide-bandgap (WG) one. We analyze and discuss the conditions of applicability of the solution from the optical viewpoint. The performance analysis has been performed using commercial ray-tracing software (ZEMAX OpticStudio), by admitting direct and isotropically diffused solar irradiation at standard AM1.5G spectrum.

The present work introduces the conceptual design of the optics for a spectral-splitting and light-guiding photovoltaic (PV) four-terminal (4T) module with appealing features for bifacial operation. The geometry here described performs low-gain 2D concentration in the visible (VIS) spectrum and can couple a Si solar cell to a wide-bandgap (WG) one. We analyze and discuss the conditions of applicability of the solution from the optical viewpoint. The performance analysis has been performed using commercial ray-tracing software (ZEMAX OpticStudio), by admitting direct and isotropically diffused solar irradiation at standard AM1.5G spectrum.

The early stages of coal oxy-combustion and pyrolysis were investigated in a drop tube furnace operated at 1300°C with different O2/N2/O2/CO2 atmosphere. The different types of carbonaceous solids produced at short residence times (50-100 ms) in the tube were separated to discriminate soot from incipient char for further analysis. In particular, a procedure involving dispersion in ethanol by ultrasonic mixing, followed by settling, and decanting to produce top and bottom products enriched in the coarse and fine particle fractions, respectively, was set up for separating soot from char. The procedure was repeated several times and the separation efficiency was checked by electron microscopy and size determination. Soot and char, separated and weighted after solvent removal, can be further characterized by a wide array of techniques in order to highlight the differences between them and their relation with the atmosphere employed. Beside electron microscopy and laser granulometry, thermogravimetry, elemental analysis and spectroscopic analysis (UV-visible and FT-IR absorption, RAMAN) were applied to soot and char for giving insights on the determination of the conditions under which the amount of soot and its chemical and physical characteristics are of practical significance for full-scale power plant particulate emissions and ash disposal.

The early stages of coal oxy-combustion and pyrolysis were investigated in a drop tube furnace operated at 1300°C with different O2/N2/O2/CO2 atmosphere. The different types of carbonaceous solids produced at short residence times (50-100 ms) in the tube were separated to discriminate soot from incipient char for further analysis. In particular, a procedure involving dispersion in ethanol by ultrasonic mixing, followed by settling, and decanting to produce top and bottom products enriched in the coarse and fine particle fractions, respectively, was set up for separating soot from char. The procedure was repeated several times and the separation efficiency was checked by electron microscopy and size determination. Soot and char, separated and weighted after solvent removal, can be further characterized by a wide array of techniques in order to highlight the differences between them and their relation with the atmosphere employed. Beside electron microscopy and laser granulometry, thermogravimetry, elemental analysis and spectroscopic analysis (UV-visible and FT-IR absorption, RAMAN) were applied to soot and char for giving insights on the determination of the conditions under which the amount of soot and its chemical and physical characteristics are of practical significance for full-scale power plant particulate emissions and ash disposal.

In the present work different methodologies have been used to analyze pyrolysis of a German bituminous coal "Auguste Victoria" with the aim to obtain pyrolysis kinetic submodels suitable for combustion models developed under Barracuda or other CFD environment such as Ansys Fluent. Intrinsic kinetics have been obtained by conventional TGA analysis at low heating rate (2-20 K/min) and with small particle size (in the order of 0.1 mm) and described by a two-step pyrolysis model. Additionally, the rates of pyrolysis were measured under fluidized bed conditions for larger particle size fractions using a method based on the time-resolved measurement of pressure in the freeboard induced by volatiles release and by a flow restriction at the exhaust. Results of thermogravimetric experiments have been worked out to obtain submodels of coal pyrolysis, comparing and discussing alternative reaction networks of different complexity. However, in fluidized bed experiments, using larger particle sizes, transport limitations become important. As expected, for this regime the reactions rates become lower the larger the particle size, reducing the relevance of intrinsic kinetic submodels.

In the present work different methodologies have been used to analyze pyrolysis of a German bituminous coal "Auguste Victoria" with the aim to obtain pyrolysis kinetic submodels suitable for combustion models developed under Barracuda or other CFD environment such as Ansys Fluent. Intrinsic kinetics have been obtained by conventional TGA analysis at low heating rate (2-20 K/min) and with small particle size (in the order of 0.1 mm) and described by a two-step pyrolysis model. Additionally, the rates of pyrolysis were measured under fluidized bed conditions for larger particle size fractions using a method based on the time-resolved measurement of pressure in the freeboard induced by volatiles release and by a flow restriction at the exhaust. Results of thermogravimetric experiments have been worked out to obtain submodels of coal pyrolysis, comparing and discussing alternative reaction networks of different complexity. However, in fluidized bed experiments, using larger particle sizes, transport limitations become important. As expected, for this regime the reactions rates become lower the larger the particle size, reducing the relevance of intrinsic kinetic submodels.

Rapporto relativo all'attività di ricerca svolta dall'IRC-CNR nel progetto STAGE-STE (FP7)