Development of a spectral dependent electrical & thermal model for high concentrating photovoltaic (HCPV) receivers
Abstract
High concentrating photovoltaic (HCPV) systems employ III-V multijunction (MJ)
solar cells. Such solar cells are monolithically connected in-series and therefore present
a strong dependence on the solar spectrum variations. In addition, the concentrated solar
flux contributes to the heat generation within the solar cells and, in combination with
the current mismatch between the subcells, can force the device to operate in elevated
temperatures. It is important therefore, to investigate the influence of the atmospheric
parameters on the electrical performance of HCPV and also to quantify the cooling
requirements based on the spectrum changes.
In this thesis, a spectral dependent electrical model has been developed to calculate the
electrical characteristics and quantify the heat power of a multijunction solar cell. A
three-dimensional finite element analysis is also used to predict the solar cell's operating
temperature and cooling requirements for a range of ambient temperatures. The
combination of these models improves the prediction accuracy of the electrical and
thermal behaviour of triple-junction solar cells. The convective heat transfer coefficient
between the back-plate and ambient air is quantified based on input spectra. A
theoretical investigation is performed to analyse the influence of air mass (AM), aerosol
optical depth (AOD) and precipitable water (PW) on the performance of each subcell
and whole. It has been shown that the AM and AOD have a negative impact on the
spectral and electrical performance of 3J solar cells while the PW has a positive effect,
although, to a lesser degree. In order to get a more realistic assessment and also to
investigate the effect of heat transfer coefficient on the annual energy yield, the
methodology is applied to four US locations using data from a typical meteorological
year (TMY3). The integrated modelling procedure is validated experimentally using
field measurements from Albuquerque, NM. The importance of the effect of
atmospheric parameters on the solar spectrum and hence the performance of HCPV
systems is highlighted in this work. The outdoor characterisation provides with useful
insight of the influence of spectrum on the performance of a HCPV monomodule and
the current CSOC and CSTC ratings are evaluated based on different spectral filtering
criteria