Basant Raj Paudyal has followed the PhD Programme at Faculty of Engineering and Science, specialisation in ICT, Scientific field Renewable Energy.
- Trial lecture starts at 10:15
- Public defence starts at 12:15
Title of trial lecture: Sustainability of silicon based solar PV manufacturing, use, recycling, and reuse
Disputation chair: Henrik Kofoed Nielsen
Assessment committee:
- First opponent: Dr. Tom Betts, Loughborough University, UK
- Second opponent: Professor Tobias Boström, UiT The Arctic University of Norway
- Chair of assessment committee: Associate Professor Ingrid Lande, UiA
Supervisors in the doctoral work:
- Main supervisor: Professor Anne Gerd Imenes, UiA
- Co-supervisor: Professor emeritus Tor Oskar Sætre, UiA
Summary of thesis
The Norwegian government has set an ambitious target of 8 TWh of solar production by 2030. With solar PV gradually becoming a significant part of the energy mix in the Nordics, it is important to investigate the factors affecting PV module performance in these conditions. In this regard, the work done in this thesis aims to expand the knowledge of PV performance and its monitoring at high latitudes with a special focus on spectral irradiance. The effects of broadband irradiance and temperature on PV performance are widely discussed in the literature. The high-latitude locations usually get a major part of the total annual irradiation during the summer solstice, aided by the longer sunshine periods. The sky conditions during the winter solstice are dominated by the diffused irradiance with extended periods of cloud cover. Lower annual average ambient temperatures generally benefit most commercial PV modules in the Nordics, as modules experience less thermal stress compared to areas closer to the equator. Broadband irradiance is represented by a single value, whereas spectral irradiance is a two-dimensional parameter, with irradiance intensity varying by wavelength. This needs to be quantified into a single parameter to assess the variations caused by the changing sky conditions, which includes atmospheric parameters like aerosol, water vapors, gases, and clouds. A comprehensive global understanding of the spectral impact on PV performance remains limited, mainly due to the cost and complexity associated with spectral irradiance measurement. With the continuous development of new PV technologies, evaluating the spectral impact to maximize the energy yield from the incident spectra is even more important.
This thesis presents the main results from the spectral irradiance resource assessment and the outdoor performance assessment of fixed-tilt, flat-plate, commercially available solar PV technologies from monitoring stations located at the University of Agder, Grimstad, Norway. The work is divided into three focus areas:
Measurement and quantification of the spectral distribution:
Three widely used spectral indices in the PV domain are used to analyze the spectral irradiance distribution in Grimstad, where the application of a statistical approach showed the lowest uncertainty of averaged photon energy (APE). The annual average general spectrum in Grimstad is found to be blue-rich, with higher energy content in the blue range compared to the AM1.5G standard spectrum. The APE indicates greater energy content than the reference spectrum at shorter wavelengths during summer and at longer wavelengths during winter. Various atmospheric parameters and factors that cause atmospheric extinction are analyzed across a wider geographic area in northern Europe to understand the micro-climatic effects on the measured spectrum using both measured and modeled spectra. The results show location-specific dependence of the spectral irradiance, with small yet significant differences in incident spectrum even in locations within similar climatic conditions.
Assessing the impact of spectral variations on PV performance:
The three commercially available module technologies c-Si, CIGS, and HIT are monitored on a custom-designed long-term performance monitoring platform at UiA, Grimstad. The impact of spectral variations is quantified and discussed on a daily, monthly, and annual basis using the spectral mismatch factor. On an annual scale, a small spectral gain on all of these monitored modules is reported.
Investigating the spectral factor in PV performance studies:
In this part, the spectral correction technique is applied to the STC correction methods in addition to the irradiance and temperature correction for performance assessment using long-term measured data. Multi-crystalline modules deployed for 6 years in these conditions show a much smaller degradation rate compared to the global average. Furthermore, the temperature coefficients are found to have remained unaffected by the outdoor exposure. Incorporating the spectral factor into STC corrections significantly reduces uncertainty in determining temperature coefficients. This provides an alternative method for determining temperature coefficients in the absence of indoor measurement facilities, especially at high latitudes where spectral variations are considerable.
In conclusion, this work presents a thorough analysis of spectral irradiance distribution and its impact on PV performance in Grimstad. The results from this work show significant annual spectral variations in the experimental location and accommodating such variations can be used to evaluate the long-term PV performance and temperature coefficients estimation.
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Opponent ex auditorio:
Deadline for the public to pose questions is during the break between the two opponents. Questions ex auditorio can be submitted to Kristine Evensen Reinfjord.