Lunar grains become charged by the sun's radiation in the tenuous atmosphere of the moon. This leads to lunar dust levitation and particle deposition which often create serious problems in the costly system deployed in lunar exploration. In this study, an electrostatic lunar dust collector (ELDC) is proposed to address the issue and the discrete element method (DEM) is used to investigate the effects of electrical particle-particle interactions, non-uniformity of the electrostatic field, and characteristics of the ELDC. The simulations on 20-lm-sized lunar particles reveal the electrical particle-particle interactions of the dust particles within the ELDC plates require 29% higher electrostatic field strength than that without the interactions for 100% collection efficiency. For the given ELDC geometry, consideration of non-uniformity of the electrostatic field along with electrical interactions between particles on the same ELDC geometry leads to a higher requirement of $3.5 kV/m to ensure 100% particle collection. Notably, such an electrostatic field is about 10 3 times less than required for electrodynamic self-cleaning methods. Finally, it is shown for a "halfsize" system that the DEM model predicts greater collection efficiency than the Eulerian-based model at all voltages less than required for 100% efficiency. Halving the ELDC dimensions boosts the particle concentration inside the ELDC, as well as the resulting field strength for a given voltage. Though a lunar photovoltaic system was the subject, the results of this study are useful for evaluation of any system for collecting charged particles in other high vacuum environment using an electrostatic field. V

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The long‐term performance and reliability of photovoltaic (PV) modules and systems are critical metrics for the economic viability of PV as a power source. In this study, the power degradation rates of two identical PV systems deployed in Florida are quantified using the Performance Ratio analytical technique and the translation of power output to an alternative reporting condition of 1000 W m−2 irradiance and cell temperature of 50 °C. We introduce a multi‐pronged strategy for quantifying the degradation rates of PV modules and arrays using archived data. This multi‐pronged approach utilizes nearby weather stations to validate and, if needed, correct suspect environmental data that can be a problem when sensor calibrations may have drifted. Recent field measurements, including I‐V curve measurements of the arrays, visual inspection, and infrared imaging, are then used to further investigate the performance of these systems. Finally, the degradation rates and calculated uncertainties are reported for both systems using the methods described previously. Copyright © 2012 John Wiley & Sons, Ltd.

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