Increasing electricity generation worldwide from renewable energy sources is essential when facing global warming. Solar power has proven cost-efficient and obtains an increasing market share, but it has a drawback of extensive area usage. Research on developing more efficient solar cells, with less area usage per unit of energy generated, has led to an interest in tandem solar cells made of perovskite and silicon. These have reported a record solar cell efficiency of 33.9%, surpassing the maximum limit for a classic crystalline silicon (c-Si) solar cell, and a solar module efficiency of 25%. Energy yield (EY) modeling is necessary to quantify how the tandem solar cells’ performance translates to the outdoor. Unlike a single junction solar cell, tandem as a multijunction configuration needs spectral irradiance as input to model the EY, which the established EY tools do not include. New developed EY tools have to use synthetic spectra models to spectrally resolve
the irradiance, and the accuracy of these synthetic spectra should be evaluated. Many EY assessments for tandem modules have not been reported, and none for Norwegian conditions situated at high latitudes and experiencing frequent cloud coverages.
This thesis compared spectra generated from two implemented synthetic spectra models, SMARTS and SBDART, in the EY modeling software PVMD Toolbox, with outdoor measurements to evaluate their accuracy in predicting the spectra. The measurements came from an EKO MS 711-N spectroradiometer at the Institute for Energy Technology (IFE) in Kjeller, Norway. The average photon energy (APE) was the primary metric used for comparison. PVMD Toolbox was then used to simulate the EY for five Norwegian locations, using the proven most precise synthetic spectra implementation.
Exploring the deviations in APE to the measured spectra, the implementation of SBDART reported a mean absolute error in APE of 0.046 eV compared to 0.209 eV for SMARTS. The most significant deviations for both implementations occurred for cloudy conditions. Using SMARTS failed to account for the clouds’ effect of altering the spectral shape, highlighting that more than simply scaling a modeled clear sky spectrum to the measured irradiance is required to account for clouds.
Further research should continue efforts to predict accurate spectra also under cloudy conditions.
The SBDART implementation was determined to be the most precise and used for EY modeling of a tandem and a c-Si module of 27.4% and 22.4% nominal efficiency, respectively, for comparison at five locations across Norway. The simulation reported a tandem EY per m2
in Norway ranging from 183 kWh/m2 in Tromsø to 320 kWh/m2
in Kristiansand. The reported yield represented a gain in EY compared to c-Si between 23.1 to 26.1% and specific EY between 0.7 to 3.1%.
However, in primo May, an error in the temperature dependency of the module efficiencies below 15◦C inside the PVMD Toolbox software was discovered, introducing more uncertainty to the results. Reportings occurring above this temperature still reported a gain in EY per m2 between 20.7 and 22.5%, with a shift in specific EY gain to the range of -1.3 to +0.2%. Quantifying the seasonal variation of the performance had the highest uncertainty, as the EY under the winter period generally is generated below temperatures of 15◦C. This leads to a need for further
research to determine the effects of seasonal variation.
The results do, however, indicate that the performance of the tandem modules seems to translate well to the outdoor Norwegian conditions, reporting specific yields comparable to the c-Si module. This means introducing a highly efficient tandem module of perovskite and silicon in Norway could increase the EY per area for future PV installations, possibly reducing land usage and area conflicts
