We experimentally studied the electrical efficiency effects of naturally forming atmospheric dust deposits on commercial photovoltaic panels. The variable considered for measurements was the electric potential for three commercial silicon modules: monocrystalline, polycrystalline, and amorphous. A mathematical model was developed to determine maximum potential as a function of temperature and of total incident radiation. The study presents two essential parts: the naturally deposited dust particles and the variation in maximum electric potential between clean and dirty modules. The results indicate that the maximum reduction in potential is around of 6% for monocrystalline and polycrystalline modules and of 12% for the amorphous silicon.

This article reports a numerical study of the transient and steady-state heat transfer and air flow in a horizontal square open cavity. This study has importance in several thermal engineering problems, for example, in the design of electronic devices and thermal receivers for solar concentrators. The most important assumptions in the mathematical formulation of the horizontal square open cavity are three: The flow is laminar, the fluid is radiatively nonparticipating, and the Boussinesq approximation is valid. The conservation equations in primitive variables are solved for a range of Rayleigh number, Ra, from 10³ to 10⁷ using the finite-volume method and the SIMPLEC algorithm. The results show that the radiative exchange between the walls and the aperture increases considerably the total average Nusselt number, from around 94% to 125%, versus the one with no radiative exchange between walls. Also, for Ra = 10⁷, the numerical model predicts periodic formation of thermal plumes in the bottom wall of the cavity, and their further movements explain the oscillation behavior of the Nusselt number with time.

Located in north western Mexico, the State of Sonora has an excellent quality solar resource, with the highest solar irradiation levels in the country. In less than 1% of its vast arid territory, it receives enough solar power to satisfy the energy demand of the entire country. In spite of its huge solar potential, there has been little work on the measurement of solar radiation in this area. At a few locations, global solar radiation has been measured for some years. Also there have been some works reporting evaluation of solar irradiation based on empirical models or satellite images. Because of the very small amount of precipitation on most of its territory, Sonora is ideal for the implementation of concentrated solar power (CSP). Beam solar radiation data is necessary for the sizing and assessment of CSP plants. Unfortunately, very little information is available on this solar radiation component for Sonora. The present work reports on the results of recent measurements of beam and solar global radiation for the area of the city of Hermosillo, in the center of the state. The obtained results are compared with other available information obtained by indirect methods, such as satellite based or empirical climate data based models. The yearly available energy as well as the utilizable energy for certain irradiance levels is evaluated