| dc.description.abstract | Solar energy is deemed to be one the most efficient and clean energy resources to generate
electricity. Photovoltaic technologies have a promising future in space and terrestrial
applications. Photovoltaic concentrating is a technique to increase the conversion
efficiency of high-efficiency solar cells. Multi-junction solar cells are designed to exploit
a larger range of solar spectrum photons and convert to electricity. In this study, triple-junction III–V solar cells compound consisting of GaInP/GaInAs/Ge semiconductor
materials is considered.
This work investigates terrestrial multi-junction solar cells performance characterisation,
which is important for the design of high concentration photovoltaic systems. The
research has developed a model of a III–V solar cell operating at high flux conditions
induced by light concentration. The thermal management on such an assembly is a focus
of this work. This research also presents the effects of Air Mass (AM) on solar cell
performance. This atmospheric parameter has a strong influence on the behaviour of high
concentrating photovoltaic solar cells. As air mass increases, the corresponding Direct
Normal Irradiance (DNI) and Cell Temperature (Tc) decrease. The effects of air mass (AM
=1–10D) atmospheric changes on triple-junction solar cells have been assessed. For High
Concentration Photovoltaic (HCPV) the light concentration on to a relatively small solar
cell area leads to high power densities.
Effective thermal management is essential to avoid damaging high temperatures. A
thermal model by using a convergent iterative technique has been developed; the
predicted convergent cell temperature limit is ≤ 80oC. The proportion of the incident
radiation not converted to electricity leads to the generation of heat; this is a function of
material temperature coefficients and current mismatch in variable atmospheric
conditions and results in an increase in cell temperature. The rate of heat loss by
convective transfer is also considered for air mass values AM =1.5, 4 and 8D. In addition,
a Finite Element Method (FEM) model is developed in COMSOL Multiphysics® in order
to predict the temperature distribution of the PV cells and thermal behaviour of the
receiver assembly.
Furthermore, in this study, a transient model of the HCPV cell has been developed using
MATLAB® Live-Link with COMSOL Multiphysics. In order to characterise the
behaviour of a triple-junction solar cell, it is essential to find the transient cell operating
temperature. The behaviour of electrical parameters of the Jsc, Voc, FF and conversion efficiency are considered. However, in the proposed model, a dynamical efficiency is
compared with constant efficiency and the error is about 12%.
The research has given a better understanding of the overall daily/annual performance
prediction of CPVs and is important for future system design in variable environment
conditions. At higher values of DNI, Tamb and lower AM the thermal response needs
enhanced/forced convection to maintain cell operation within/below safe operating
temperature and to optimise energy yield. For long-term performance evaluation, the
average of monthly variations of atmospheric parameters throughout the year is
considered. Thus, during the summer months, a higher record of the atmospheric
parameters values in which need more consideration. The annual cell operating
temperature of ˃ 80oC represents about 13% of the time, which happened during the
Summer season. As is noted, the cell temperature between 65 – 70oC is predominate in
the Spring and Autumn seasons and represent about 24%, (the highest frequency). | en |
