Stefan Myrskog

Anti-soiling coatings for Sun Simba concentrated photovoltaic (CPV) modules

Soiling is a major source of power degradation in photovoltaic (PV) modules, with variable impact as a function of environmental conditions. For concentrated photovoltaic (CPV) modules the impact is greater due to requirements in preserving the optical path within the module. In an effort to reduce soiling a number of self-cleaning coatings have been developed and implemented in solar modules. Self-cleaning films are generally based on high (hydrophilic) or low (hydrophobic) surface energy materials that leverage extreme wetting behavior to reduce contamination, and/or photocatalytic materials that decompose contaminants with ultraviolet (UV) activation. In this study we explore a number of third-party coating materials to reduce soiling losses in Morgan Solar’s Sun Simba CPV modules. The primary objective is to identify coating solutions that are mechanically robust and effective in anti-soiling, as well as compatible with our materials and optical concentration architecture. In preliminary testing two p...

Electroluminescence imaging of Morgan Solar Inc.’s 4th generation CPV technology for in-line quality control and optical efficiency estimation

An electroluminescence test for a Concentrated PV system is presented with the objective of capturing high resolution pseudo-efficiency maps that highlight optical defects in the concentrator system. Key parameters of the experimental setup and imaging system are presented. Image processing is discussed, including comparison of experimental to nominal results and the quantitative estimation of optical efficiency. Efficiency estimates are validated using measurements under a collimated solar simulator and ray-tracing software. Further validation is performed by comparison of the electroluminescence technique to direct mapping of the optical efficiency. Initial results indicate the mean estimation error for Isc is -2.4% with a standard deviation is 6.9% and a combined measurement and analysis time of less than 5 seconds per optic. An extension of this approach to in-line quality control is discussed.

Laser-based measurement of tunnel junctions in triple-junction solar cells: Lab-scale characterization and in-line screening

A laser-based system capable of characterizing tunnel junction behaviour in multi-junction cells has been developed. Incident flux density and therefore local current density is varied, while keeping total current constant. Current-voltage (IV) curves show characteristic dips due to exceeding the current density threshold beyond which the tunnel junction behaves non-linearly (Jpeak). This approach has been validated through correlation with on-sun results. The ability to distinguish which tunnel junction is problematic within a multi-junction solar cell stack is also demonstrated. The design of a relatively simple and low-cost bench-top test system is presented, as well as a version suitable for inline screening. This work affords the development and selection of cells appropriate for implementation in high-efficiency, low-cost CPV designs.

Validation and comparison of three power prediction models for CPV modules

Accurate predictive energy modelling of a solar farm requires a thorough understanding of solar spectral variations, along with the spectral response and optical properties of the photovoltaic system. This paper investigates the minimum data required to accurately predict power output from CPV modules, comparing modelled output to both measured data and the existing method used by Sandia PV Array Performance Model (SAPM). Three models were derived based on various weather inputs. A Detailed Spectral Model (DS) uses SMARTS, inputting measured air mass, aerosols, ozone and water content, and incorporating measured DNI to account for cloudy days. The Sub-System Algebraic Model (SSA) removes the need for instantaneous spectrum calculations by creating equations for each sub-cell and DNI, based on the same inputs as the DS. These two models rely heavily on aerosol, which is not readily available. Alternatively, an Empirical model (EMP) may be used to determine the relationship between measured output power and...