Review on feasible recycling pathways and technologies of solar photovoltaic modules

Phase and morphology evolution of CaCO3 precipitated during carbonation of lime pastes via the reaction Ca(OH)2 + CO2 → CaCO3 + H2O has been investigated under different conditions (pCO2 ≈ 10−3.5 atm at 60 % RH and 93 % RH; pCO2 = 1 atm at 93 % RH) using XRD, FTIR, TGA, and SEM. Simulations of the pore solution chemistry for different stages and conditions of carbonation were performed using the PHREEQC code to investigate the evolution of the chemistry of the system. Results indicate initial precipitation of amorphous calcium carbonate (ACC) which in turn transforms into scalenohedral calcite under excess Ca2+ ions. Because of their polar character, $$ \left\{ {21\bar{3}4} \right\} $$
 scalenohedral faces (type S) interact more strongly with excess Ca2+ than non-polar $$ \left\{ {10\bar{1}4} \right\} $$
 rhombohedral faces (type F), an effect that ultimately favors the stabilization of $$ \left\{ {21\bar{3}4} \right\} $$
 faces. Following the full consumption of Ca2+ ions and further dissolution of CO2 leading to a pH drop of the pore solution, $$ \left\{ {21\bar{3}4} \right\} $$
 scalenohedra are subjected to dissolution. This eventually results in re-precipitation of $$ \left\{ {10\bar{1}4} \right\} $$
 rhombohedra at close-to-neutral pH. This crystallization sequence progresses through the carbonated depth with a strong dependence on the degree of exposure to CO2, which is controlled by the carbonated pore structure governing the diffusion of CO2. Both the carbonation process and the scalenohedral-to-rhombohedral transformation are kinetically favored under high RH and high pCO2. Supersaturation plays a critical role on the nucleation density and size of CaCO3 crystals. These results have important implications in understanding the behavior of ancient and modern lime mortars for applications in architectural heritage conservation.

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Phase and morphology evolution of calcium carbonate precipitated by carbonation of hydrated lime

Whispering gallery modes (WGMs) have been exploited for a broad range of sensing applications. However, the vast majority of WGM sensors consist of passive resonators, requiring complex interrogation systems to be employed, ultimately limiting their practicality. Active resonators containing a gain medium, allowing remote excitation and collection of the WGM-modulated fluorescence spectra, have emerged as an alternative to passive resonators. Although research is still in its infancy, recent progress has reduced the performance gap between the two paradigms, fueled by the potential for new applications that could not previously be realized. Here, recent developments in sensors based on active WGM microresonators are reviewed, beginning with a discussion of the theory of fluorescence-based and lasing WGMs, followed by a discussion of the variety of gain media, resonator architectures, and emerging sensing applications. We conclude with a discussion of the prospects and future directions for improving active WGM sensors.

Fluorescent and lasing whispering gallery mode microresonators for sensing applications

Photovoltaic (PV) technologies have experienced considerable growth rates of up to 70% in the last years. This has been possible because of low total CO 2 emissions and a positive overall energy balance for PV. Several institutions have developed future scenarios which show an increase in global electricity demand from 17 000 TWh in 2005 to some 60 000 TWh by 2050. A significant part of this amount should be supplied by PV installations. Based on selected scenarios material demand is calculated for four different PV technologies: crystalline silicon (c-Si), amorphous silicon (a-Si) in tandem configuration, cadmium tellurium (CdTe) and copper indium gallium diselenide (CIGS). As these technologies use rare metals it is shown, that particular scenarios are unlikely to be realized because of supply constraints and scarcity phenomena. Critical materials are silver, tellurium and indium. We consider photovoltaics as an appropriate example for the implementation of resource availability considerations into technology development strategies.

Considerations of resource availability in technology development strategies: The case study of photovoltaics

A comparative life-cycle assessment of photovoltaic electricity generation in Singapore by multicrystalline silicon technologies

Recovery of silicon powder from kerf loss slurry by centrifugation

The constantly rising price of silicon feedstock has been the most important factor preventing photovoltaic (PV) energy from reaching grid parity. On the other hand, large amount of silicon gets wasted during slicing. We report a promising approach to recycle kerf loss silicon from cutting slurry waste for solar cell applications. Silicon carbide (SiC) and metal impurities were successfully removed by chemical/ physical processing from the slurry waste to recover solar grade silicon. The effects of centrifugation using heavy fluids and high-temperature treatment in the removal of SiC particles are discussed in detail. Ingots from the recycled silicon were grown by using directional solidification. The average resistivity and minority carrier lifetime of the grown crystals were found to be about 0·7 Ω cm and 1·02 µs, respectively, which were close to the original sawing silicon ingots. Solar cells using multi-crystalline wafers of recovered silicon were fabricated and the best energy conversion efficiency was found to be 12·6% comparable to those from the high-purity silicon. Copyright © 2008 John Wiley & Sons, Ltd.

Recovery of silicon from kerf loss slurry waste for photovoltaic applications

Recovery of silicon powder from kerfs loss slurry using phase-transfer separation method

http://ntur.lib.ntu.edu.tw/bitstream/246246/92184/1/36.pdf

Interpretation of calcite growth data using the two-step crystal growth model

In slicing a crystal bar into silicon wafers, an average about 40% of silicon would be loss due to the widths of slicing wires themselves. The fact that the silicon slurry is discarded as sludge or discarded after recovering silicon carbide particles causes a large waste of cost. If the silicon slurry (40% of silicon) could be recovered as the raw material for growing silicon crystal bars, the production cost would be lowered. The recovery method of silicon slurry according to the present invention could effectively obtain silicon raw material after removing impurities, which could recover the raw material used in solar crystals, further capable of increasing the silicon crystal production and lowering the cost.

Yen-Chih Lin

Papers

Recovery of silicon powder from kerf loss slurry by centrifugation

Recovery of silicon from kerf loss slurry waste for photovoltaic applications

Recovery of silicon powder from kerfs loss slurry using phase-transfer separation method

Interpretation of calcite growth data using the two-step crystal growth model

Recovery method of silicon slurry