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This literature study examines previous studies of the optical properties of snow, and attempts to tie them together with studies on the effects of shading on photovoltaic solar panels. The study presents some information on the general properties of snow, and ice including geographic extent and some conditions of snow and ice formation. General optical properties of snow are examined, such as reflectance (albedo) and spectral transmittance. Common transmittance profiles for snow covers are also examined. The study also presents some commonly understood effects of shading on photovoltaic panels, both in the form of uniform shading (weak light) and partial shading. Other snow-related aspects of operating a photovoltaic system are also brought up, such as snow loads and the risks posed by snowmelt, particularly in regards to building-integrated or building-applied photovoltaics. Common methods of addressing snow-related challenges are summarized, both on a material and an architectural level. Lastly, suggested future research paths are presented.

We have experimentally investigated the ablation threshold in silicon as a function of temperature when applying ultrashort laser pulses at three wavelengths. By varying the temperature of a silicon substrate from room temperature to 320 C, we observe that the ablation threshold for a 3 ps pulse using a wavelength of 1030 nm drops from 0.43 J/cm 2 to 0.24 J/cm 2 , a reduction of 43%. For a wavelength of 515 nm, the ablation threshold drops from 0.22 J/cm 2 to 0.15 J/cm 2 , a reduction of 35%. The observed ablation threshold for pulses at 343 nm remains constant with temperature, at 0.10 J/cm 2 . These results indicate that substrate heating is a useful technique for lowering the ablation threshold in industrial silicon processing using ultrashort laser pulses in the IR or visible wavelength range. In order to investigate and explain the observed trends, we apply the two-temperature model, a thermodynamic model for investigation of the interaction between silicon and ultrashort laser pulses. Applying the two-temperature model implies thermal equilibrium between optical and acoustic phonons. On the time scales encountered herein, this need not be the case. However, as discussed in the article, the two-temperature model provides valuable insight into the physical processes governing the interaction between the laser light and the silicon. The simulations indicate that ablation occurs when the number density of excited electrons reaches the critical electron density, while the lattice remains well below vaporization temperature. The simulated laser fluence required to reach critical electron density is also found to be temperature dependent. The dominant contributor to increased electron density is, in the majority of the investigated cases, the linear absorption coefficient. Two-photon absorption and impact ionization also generate carriers, but to a lesser extent. As the linear absorption coefficient is temperature dependent, we find that the simulated reduction in ablation threshold with increased substrate temperature is linked to the temperature dependence of the linear absorption coefficient. Another factor influencing the ablation threshold is the wavelength dependence of the interaction with the excited electron plasma. This wavelength dependence can explain that we observe experimentally similar ablation thresholds for a wavelength of 1030 nm at 320 C and for 515 nm at room temperature, even though the linear absorption coefficient in the latter case is much higher.