We present a case study from commercial-scale PV power plants in the US Southwest, demonstrating that accurate soiling measurement requires detection of PV module power loss in order to account for non-uniform soiling, such as along the edges of modules. Small amounts of non-uniform soiling may cause significant power losses that cannot be detected accurately through measurements of short-circuit current alone. Furthermore, based on aerial IR and visual inspection and I-V curve data acquired at a number of sites, we believe that the non-uniform soiling phenomenon is common in regions with higher rates of soiling and little rain, especially for low-tilt installations.

The proper modeling of Photovoltaic(PV) systems is critical for their financing, design, and operation. PV_LIB provides a flexible toolbox to perform advanced data analysis and research into the performance modeling and operations of PV assets, and this paper presents the extension of the PV_LIB toolbox into the python programming language. PV_LIB provides a common repository for the release of published modeling algorithms, and thus can also help to improve the quality and frequency of model validation and inter comparison studies. Overall, the goal of PV_LIB is to accelerate the pace of innovation in the PV sector.

Accurate solar radiation data are necessary to model solar photovoltaic (PV) systems; unfortunately, ground-measured or satellite-derived data are not universally available. The MERRA reanalysis dataset offers hourly solar radiation data for the entire globe. The accuracy of the MERRA dataset has been evaluated using ground measurements of solar radiation, but it has never been evaluated for use as an input for PV modeling. This study uses measured solar radiation and PV production data to evaluate the suitability of the MERRA solar data for PV modeling. The results indicate that MERRA solar data produces slightly higher errors than ground-measured solar data, but overall the accuracy is suitable for most PV applications.

Although the spectral effects of direct and diffuse radiation on solar photovoltaic (PV) performance are relatively well understood, recent investigations have shown that there can be a spectral bias introduced due to albedo from common ground surfaces that can impact the optimal selection of PV materials for a known location. This paper extends analysis to the effects of spectral bias due to the specular reflectivity of 22 commonly occurring surface materials (both man-made and natural) and analyzes the albedo effects on the performance of seven PV materials covering three common PV system topologies: industrial (solar farms), commercial flat rooftops and residential pitched roof applications. An effective albedo is found for each surface material and PV material combination, which can be used in lieu of broadband albedo values in PV simulations. These results enable PV material selection for specific environments enabling geographic optimization for the micro-environment, while at the same time assisting optimal surface selection in the vicinity of existing or planned PV arrays. This analysis is of particular significance for the modeling of performance of bi-facial PV modules and vertical BIPV.

The accurate prediction of yields from photovoltaic systems (PV) is critical for their proper operation and financing, and in northern latitudes the effects of snowfall on yield can become significant.This work provides methods for identifying snowfall effects from commonly collected performance data, and recommends a model to allow for prediction of these effects based solely on meteorological time series.The model was validated with data from two large-scale (>8MW) operational PV plants.For the low tilt angles most affected by snowfall, this analysis was able to accurately predict both daily and mean values of snow effects.This methodology will enable system operators to utilize performance data to accurately identify and predict snowfall losses, and will assist system designers to optimize for the effects of snowfall on new system designs.

La eficiencia cuántica de materiales fotovoltaicos depende de la longitud de onda de la radiación incidente, el espectro solar influye en la producción de energía producida por estos sistemas. En el presente trabajo, se diseñó y construyó un prototipo funcional de un sistema de medición de radiación solar (global y difusa) basado en un espectrómetro de amplio espectro para el monitoreo solar en Cochabamba, Bolivia, conjuntamente con un sistema similar instalado en Kingston, Ontario. Los datos obtenidos en dos regiones con características geográficas muy distintas ayudarán en el estudio y optimización de materiales fotovoltaicos, para su implementación en diferentes partes del mundo, con características particulares de radiación incidente. Los resultados obtenidos serán publicados para que otras regiones también se beneficien de sistemas fotovoltaicos con materiales optimizados según las características geográficas. Para la construcción mecánica del sistema, se utilizaron perfiles de aluminio de 60x30 mm. Esta estructura metálica sujeta a una fibra óptica de cuarzo lleva la radiación solar al espectrómetro Ocean Optics USB4000 (200-900 nm). La electrónica del sistema de control, está gobernada por un microcontrolador Arduino UNO, el cual se encarga de sincronizar el movimiento de dos motores PAP bipolares y la toma de datos en el espectrómetro que se activa con un trigger externo. La característica principal del sistema es permitir la medición del espectro de los componentes global y difuso de la radiación solar en diferentes ángulos de incidencia. El sistema mecánico ajusta un extremo de una fibra óptica de 0 a 90 grados en dirección norte, cada nueve grados, midiendo la radiación global y mediante una banda mecánica que produce sombra sobre la fibra óptica, mide la radiación difusa. Las medidas son tomadas cada hora y el rango espectral abarcado es del UVA, VIS y parte del IR cercano. Se realizaron pruebas preliminares en dos ciudades de Bolivia y se demostró que la cantidad de radiación UVA es mayor en el El Alto (4062 msnm), la ciudad con mayor elevación, en comparación con Cochabamba que se encuentra a 2570 msnm.

The technological evolution of the 3-D printer, widespread internet access and inexpensive computing has made a new means of open design capable of accelerating self-directed sustainable development.This study critically examines how open source 3-D printers, such as the RepRap and Fab@home, enable the use of designs in the public domain to fabricate open source appropriate technology (OSAT), which are easily and economically made from readily available resources by local communities to meet their needs.The current capabilities of open source 3-D printers is reviewed and a new classification scheme is proposed for OSATs that are technically feasible and economically viable for production.Then, a methodology for quantifying the properties of printed parts and a research trajectory is outlined to extend the existing technology to provide complete village-level fabrication of OSATs.Finally, conclusions are drawn on the potential for open source 3-D printers to assist in driving sustainable development.

The authors discuss the benefits of instituting a computerized dispatch card system to make the hospital security department more efficient and effective.