Champion photovoltaic (PV) cell and module efficiencies have been reported in Progress in PV since 1993. Following the evolution of these efficiencies enables researchers to track the progress of various technologies. National Renewable Energy Laboratory has maintained a historical chart of the champion cell efficiencies, but has not published a similar chart of champion module efficiencies. Here, we analyze champion module efficiencies and compare them to champion cell efficiencies to better understand technology trends over the last three decades, highlighting that, in some cases, module efficiencies exceed 90% of cell efficiencies. Recommendations are provided on how to change the data collection and reporting for champion efficiencies to increase the value of these records.

Soiling, particulate accumulation on photovoltaic (PV) module surfaces, reduces the available solar resource and the resulting generated device power. In regions where the installation of PV technology is advantageous because of high irradiance areas, in many cases, also possess arid or desert climates that inherently exhibit greater surface soiling. Because of the energy production and associated maintenance-cost factors, it is advantageous to evaluate environmental factors (meteorological variables, climate, and geographical features) as early as possible in developing a PV installation. Alternatively, the determination of the soiling rates (SRate), even after system commissioning can aid in the optimization of maintenance and cleaning-cycle requirements. Significant research has been reported addressing these critical factors through determining local soiling losses. This article presents, evaluates, and compares methodologies to accurately determine and compare SRate and losses from soiling monitoring stations and installed PV systems operating in Belo Horizonte, Brazil (latitude-19.92°, longitude-43.99°). Specifically, data collected from soiling stations were used to estimate the soiling ratio (SRatio) and SRate. A related process is applied to the PV system, using the performance ratio. The methodology incorporates several key refinements. These include normalization and adjustment for the meteorological parameters (temperature and irradiance). Additionally, the differences between the measured global horizontal irradiance (GHI), the plane-of-array irradiance ( G _POA ) obtained through the application of a transposition model, and the plane-of-array measured by reference cell ( G _ref ) are presented and compared. The results demonstrate that the transposition model is an acceptable option for cases in which only GHI measurements are available.

The choice of a particular PV technology for best performance is sometimes based upon a single factor or single operating condition. However, many parameters have functionalities that oppose each under actual operating conditions. In this paper, the comparisons of different PV module technologies under moderate environmental conditions (Tropical Climate Zone, Belo Horizonte, Brazil) are explored based upon the two competing parameters of soiling-layer spectral effects and panel operating temperature. Specifically, low-bandgap PV technologies (e.g., Si or Cu(In,Ga)(SSe)₂) are reported to have performances less affected by the absorption of incoming sunlight than higher-bandgap absorbers (e.g., a-Si:H or CdTe). However, the opposite is true for operating temperatures, with higher bandgaps having advantages under higher-temperature operating conditions. We present a simple comparative soiling-temperature model with experimental collaborative data to address the following question: What is the controlling parameter of the combination of soiling spectral effects and temperature on lower- and higher-bandgap module technologies? Temperature coefficients are measured for groups of modules for the four technologies having bandgaps ranging from 1.1 to 1.7 eV. Additional optical absorption for the soiling layers in the range of 300 nm to ~600 nm is confirmed by transmission measurements. The data from our soiling monitoring stations indicate that these potential spectral effects are based on consistent differences in soiling ratios and soiling rates. Some differences between the model predications and experimental observations are discussed. This paper reports temperature and soiling regions of “best-of-class” performances for these four commercial PV technologies in this climate region based upon the two competing parameters.

Solar energy has emerged as the lowest-cost source of electricity in many locations. This low cost, coupled with its clean, quiet operation, has led to it being the fastest expanding electricity-generating technology today. This is true for both large grid-connected installations and small stand-alone systems. Photovoltaics (PV) promises to be a major driver for ensuring reliable energy access for nearly a billion underserved people around the globe, as well as providing the path for the energy transition from a fossil fuel past to a green and sustainable future.