A unique system for the synchronous measurement of photovoltaic module electrical
parameters and solar spectral irradiance is described. Data quality control is addressed
in depth and the practices followed to ensure integrity for the ensuing analysis are
Irradiance spectra have been characterised with a single-number descriptor, the average
photon energy. Unlike previous spectral characterisation work, the figure employed here
is independent of artificially imposed references, such as the spectral response of a solar
cell. This has allowed it to be used in a full analysis of spectral variation in the UK, with
comparison made to a second site of significantly different climate.
This simple characterisation has also allowed spectral irradiance measurements to be
included for the first time in a thorough investigation of the effects of different
environmental factors on photovoltaic device performance in real operating conditions.
Discussion is entered on each of the main influences on key device parameters and
concludes with a quantification of the principal effects on electrical energy generation.
The development of an enhanced spectral irradiance model is described, which can
simulate solar spectra under non-ideal weather conditions, as experienced by many
locations. In validation against measured data, it is proved a convenient solution to the
problem of poor availability of spectral irradiance data for use in photovoltaic
The inclusion of spectral effects into photovoltaic device modelling is undertaken and
shown to significantly improve existing modelling approaches. Finally, improvements
are identified and suggestions made to further the work.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.